Thermal or photodecomposition of the classical free radical generating diazo reagent 2,2′-azobis(2-methylpropionitrile) (AIBN) was used as a source of cyanide anions in the synthesis of copper(I)–cyanide frameworks. The reported methodology utilizes the direct reduction of Cu^II(aa)(NN)X (aa = deprotonated amino acid, NN = bidentate nitrogen-based ligand, X = Cl or Br) complexes by AIBN/ascorbic acid to yield seven novel coordination networks. Aromatic amines were directly incorporated into 1D Cu^I–CN chains. In the case of the aliphatic amine tetramethylethylenediamine (TMEDA), a 3D Cu^I–CN framework was obtained. This novel procedure is mild, applicable to a variety of nitrogen-based ligands, and represents an efficient alternative to currently used hydrothermal or solvothermal methods.

Thermal or photodecomposition of 2,2′-azobis(2-methylpropionitrile) (AIBN) is used as a source of cyanide anions in the synthesis of copper(I)–cyanide frameworks. The reported methodology utilizes the direct reduction of Cu^II(aa)(NN)X (aa = deprotonated amino acid, NN = bidentate nitrogen-based ligand, X = Cl or Br) complexes by AIBN/ascorbic acid to yield six novel coordination networks.

Well-ordered ultrathin films (UTFs) of {pyrenetetrasulfonate(PyTS)/ZnS}_n were fabricated by alternating assembly of 1,3,6,8-PyTS and exfoliated Zn₂Al layered double hydroxide (LDH) nanosheets through layer-by-layer (LBL) electrostatic deposition, followed by an effective in situ gas/solid sulfurization reaction with H₂S. The assembly process was monitored by UV/Vis spectroscopy, which showed regular stepwise growth of the (PyTS/LDH)_n UTFs with consecutive deposition cycles. It is worth noting that the structure of the well-ordered UTFs is retained after the in situ gas/solid sulfurization reaction. Although both (PyTS/LDH)_n UTFs and the sulfurized (PyTS/ZnS)_n UTFs respond to ethanol at a relatively low operating temperature (70 °C), the (PyTS/ZnS)_n UTFs exhibit a much better response, a fact that can be attributed to synergistic interactions between inorganic ZnS and organic pyrene components. Moreover, the well-ordered (PyTS/ZnS)₃₀ UTF exhibits a stronger sensor response to ethanol than to other gases, including NH₃, H₂, CO, C₂H₂, and CH₄.

{Pyrenetetrasulfonate(PyTS)/ZnS}_n ultrathin films have been fabricated by a two-step procedure of layer-by-layer assembly of PyTS with Zn₂Al layered double hydroxide, followed by in situ sulfurization with H₂S. Gas-sensing measurements of the as-prepared (PyTS/ZnS)_n films indicate that they selectively respond to ethanol gas at a relatively low temperature of 70 °C.

The capability of bis(trimethylsilyl)amidoalane to act as a hydride transfer reagent in organolanthanide chemistry was investigated by probing its reactivity toward alkylyttrium complexes. Reaction with Cp*₂YMe(thf) led to the isolation of the bimetallic complex Cp*₂Y(μ-H)₂Al(Me)[N(SiMe₃)₂] (Cp* = 1,2,3,4,5-pentamethylcyclopentadiene), whereas reaction with [Cp*YMe₂]₃ gave MeAl[N(SiMe₃)₂]₂ as the only isolable hydride transfer product. The dimeric complex [Cp*Y{N(SiMe₃)₂}(μ-H)]₂ represents one possible product of the aforementioned reaction that could be structurally characterized. The use of [YMe₃]_n as the alkylyttrium source led to the isolation of Y[N(SiMe₃)₂]₃, which displays competition between amide and hydride transfer. Finally, the performance of Cp*₂Y(μ-H)₂Al(Me)[N(SiMe₃)₂] and [YMe₃]_n in the hydroalumination of 1-octene was tested, and these compounds represent the first rare-earth metal catalysts for this transformation.

YAH: Alkyl/hydrido exchange readily takes place when the yttrium methyl complexes (C₅Me₅)₂YMe(thf), [(C₅Me₅)YMe₂]₃, and [YMe₃]_n are treated with the amidoalane HAl[N(SiMe₃)₂]₂. The resulting heterobimetallics catalyze the addition of the amidoalane across 1-octene, as shown for (C₅Me₅)₂Y(μ-H)₂Al(Me)[N(SiMe₃)₂].

The reactions of the metallocene generators Cp′₂M(L)(η²-Me₃SiC≡CSiMe₃) [1a-Ti: Cp′ = Cp = η⁵-cyclopentadienyl, M = Ti, L = none; 1b-Ti: Cp′ = Cp* = η⁵-pentamethylcyclopentadienyl, M = Ti, L = none; 1c-Ti: Cp′₂ = rac-(ebthi) = rac-ethylenebistetrahydroindenyl, M = Ti, L = none; 1a-Zr: Cp′ = Cp, M = Zr, L = pyridine; 1b-Zr: Cp′ = Cp*, M = Zr, L = none; 1c-Zr: Cp′₂ = rac-(ebthi), M = Zr, L = none] with 1,2-bis(4′,4′,5′,5′-tetramethyl[1′,3′,2′]dioxaborolan-2′-yl)acetylene (bPinBA, 2) as a di-heteroatom-substituted alkyne were investigated. A slightly special reaction of 1a-Ti with 2 produced no titanacyclopropene or titanacyclopentadiene, but instead complex 3 was produced by the coupling of two alkyne units with one of the Cp ligands to form a six-membered ring annelated to a five-membered one. The titanocene complexes 1b-Ti and 1c-Ti reacted with 2 to form the titanacylopropenes 4 and 5. The complex 1a-Zr reacts with 2 to the corresponding zirconacyclopropene 6 as a byproduct, in which the pyridine ligand remains coordinated. If the pyridine ligand dissociates, a coupling with a second alkyne yields the zirconacyclopentadiene 7 as the main product. The reaction of the sterically more demanding zirconocene precursor 1c-Zr also yielded the zirconacyclopentadiene 8, whereas 1b-Zr did not react with 2. The complex rac-(ebthi)Ti(η²-bPinBA) (5) reacts with gaseous dry CO₂ directly to form the titanafuranone 9. The molecular structures of complexes 5 and 6 were characterised by single-crystal X-ray crystallography.

Group 4 metallocenes and bis(tetramethyldioxaborolanyl)acetylene gave different products: “Cp₂Ti” afforded a dihydroindenyl complex. “rac-(ebthi)Ti”, “Cp*₂Ti” and “Cp₂Zr(py)” led to metallacyclopropenes, whereas “Cp₂Zr” and “rac-(ebthi)Zr” yielded metallacyclopentadienes. One of the titanacyclopropenes reacts with CO₂ to a titanacyclofuranone.

A novel synthetic route to 4,4″-disubstituted-2,2′:6′,2″-terpyridine ligands by Suzuki–Miyaura cross-coupling was elaborated by synthesizing compounds 4a–5c. The considerable stability of 4-substituted lithium triisopropyl 2-pyridylborates 2a–c, which are less prone to protodeboronation than similarly functionalized neutral boronic acid derivatives, enabled this synthetic route. The terpyridine core structure was further functionalized by exposing 4,4″-dichloroterpyridine (4b) to Suzuki coupling conditions to yield 4,4″-diarylterpyridines 5a–c. Homoleptic Fe^II complexes 8a–f of the reported terpyridine ligands were formed quantitatively, which demonstrates the lack of steric repulsion of substituents at the 4- and 4″-positions during complexation. The solid-state structures of particular ligands and Fe^II complexes were analyzed by single-crystal X-ray crystallography. UV/Vis absorption data for the Fe^II complexes are also provided to complement the results reported here.

A novel synthetic route to terpyridine ligands is reported. Pyridine building blocks are interlinked by Suzuki–Miyaura cross-coupling reactions. The potential of the method is demonstrated by assembling the 4,4″-disubstituted terpyridine ligands shown, which are subsequently converted into their homoleptic Fe^II complexes.

A DFT/time-dependent DFT (TD-DFT) investigation was conducted on a series of cationic iridium(III) complexes with 2-phenylpyridine (ppyⁿ) derivatives and a diphosphane (PPⁿ) ancillary ligand to shed light on the effects of stereoisomerism and ligand substituents on the photophysical properties. The geometries, electronic structures, lowest-lying singlet–singlet absorptions, vertical singlet–triplet excitations, and triplet–singlet emissions of N,N-cis-[Ir(ppy⁰)₂(PP)]⁺ (1), N,N-trans-[Ir(ppy⁰)₂(PP)]⁺ (2) and their derivatives were investigated with DFT-based approaches [ppy⁰ = 2-phenylpyridine, PP = 1,2-bis(diphenylphosphanyl)ethene]. The complex N,N-trans-[Ir(ppy²)₂(PP²)]⁺ (3b) shows high quantum phosphorescence efficiency (Φ_PL) of 91 %, whereas an extremely low Φ_PL (<1 %) was observed for N,N-trans-[Ir(ppy⁴)₂(PP¹)]⁺ (2d). To clarify this behavior, the S₁–T_n splitting energy (ΔE), the transition dipole moment (μ) upon the S₀→S₁ transition, and the energy gap between the triplet metal-to-ligand charge transfer (³MLCT) π–π* and triplet metal-centered (³MC) d–d states (ΔE_MC–MLCT) were calculated. A drastically small ΔE and large μ for 3b (<0.05 eV and 1.38 D, respectively), compared to those for 2d (>0.2 eV and 1.26 D, respectively), were found to be closely linked to the substituents on the ppyⁿ ligands. The remarkably small ΔE and similar μ for N,N-cis 1c (<0.05 eV and 1.41 D, respectively), compared to those for N,N-trans 2c (>0.1 eV and 1.42 D, respectively), could be attributed to the effects of the trans–cis structural isomerism. On the basis of these parameters, the higher Φ_PL of 3b with respect to that of 2d was explained, and 1c, 1d, 2b, and 2e were considered to have better physical properties than the experimentally synthesized complexes 2, 2d, and 3b. The newly designed 1c, 1d, 2b, and 2e are expected to be highly emissive in the blue-green region for light-emitting electrochemical cell (LEC) applications.

The N,N-trans and N,N-cis isomers of [Ir(ppy⁰)₂(PP)]⁺ (ppy⁰ = 2-phenylpyridine ligand, PP = diphosphane ligand) have markedly different photophysical properties, which were investigated by a DFT/time-dependent DFT (TD-DFT) approach. Their different quantum phosphorescence efficiencies (Φ_PL) are interpreted with their different radiative (k_r) and nonradiative (k_nr) rates.

The first terminal organometallic alkylphosphanylidenetantalum(V) complexes [Cp*Ta{1,2-(NSiMe₃)₂C₆H₄}(PR)] were obtained with cyclohexyl (2) and isopropyl groups (3) at phosphorus, whereas adamantyl and tert-butyl substituents resulted in the formation of the paramagnetic tantalum(IV) complex [Cp*Ta{1,2-(NSiMe₃)₂C₆H₄}Cl] (4). DFT studies showed that the terminal cyclohexyl and isopropyl phosphanylidene complexes are stable towards dimerization and dissociation.

The first terminal organometallic alkylphosphanylidenetantalum(V) complexes are obtained with cyclohexyl and isopropyl groups at phosphorus, whereas adamantyl and tert-butyl substituents result in the formation of a paramagnetic tantalum(IV) complex. DFT studies show that the terminal cyclohexyl and isopropyl phosphanylidene complexes are stable towards dimerization and dissociation.

We demonstrate that the particle sizes in cyano-bridged coordination polymers consisting of Ni^II–C≡N–Fe^II units are precisely controlled by changing the amount of chelating agent, sodium citrate. With an increase in the amount of chelating agent added, the average size of the particles gradually increases from 20 to 350 nm with retention of a well-defined cubic shape. Furthermore, the use of different Fe sources expands the possible control range up to 500 nm.

The particle sizes in cyano-bridged coordination polymers consisting of Ni^II–C≡N–Fe^II units are precisely controlled from 20 to 500 nm by changing the amount of sodium citrate added as a chelating agent and/or by using a different Fe source. Our synthetic concept is widely applicable to other coordination polymers, which would be beneficial to various applications in the future.

Perfluoroarylation of a known iron(II) diiodoclathrochelate precursor and its new n-butylboron-capped hexaiodomacrobicyclic analog with pentafluorophenylcopper(I) gave the first iron(II) cage complexes with inherent perfluoroaryl substituent(s). The complexes synthesized were characterized by elemental analysis, MALDI-TOF mass spectrometry, IR, UV/Vis, ¹H, ¹¹B, ¹⁹F, and ¹³C{¹H} NMR spectroscopy, and X-ray crystallography. The encapsulated iron(II) ions in the X-rayed hexaiodo- and di- and hexa(pentafluorophenyl)ated iron(II) clathrochelates are located almost in the centers of their FeN₆ coordination polyhedra. The geometry of the hexaiodoclathrochelate precursor is trigonal prismatic (TP, distortion angle φ = 4.5°), whereas the perfluoroarylated iron(II) clathrochelates are intermediate between a TP and a trigonal antiprism (TAP) (φ ≈ 25°). This rotation and expansion from TP to TAP polyhedra causes horizontal spreading, and the heights h decrease from 2.40 to 2.33–2.35 Å. Anodic ranges of the cyclic voltammograms (CVs) for the pentafluorophenylated iron(II) clathrochelates contain one-electron waves of the metal-centered Fe^2+/3+ oxidation, which are quasireversible in the cyclic voltammetry (CV) timescale. The potentials for the mono- and difunctionalized clathrochelates are only slightly different, as a result of steric hindrance between two pentafluorophenyl substituents in the same chelate ribbed fragment decreasing their conjugation with the polyazomethine clathrochelate framework and lowering the electronic effects. The cathodic ranges of these CVs contain irreversible waves for encapsulated metal-centered Fe^2+/+ reduction to anionic forms of the cage complexes that are unstable on the CV timescale.

Iron(II) clathrochelates with two and six inherent pentafluorophenyl substituents were obtained by copper-promoted perfluoroarylation of their iodine-containing macrobicyclic precursors and characterized by analytical and spectral methods and X-ray diffraction.

New mixed-valence Cu^I–Cu^II 1D coordination polymers of the structure [Cu^I₂Cu^IIX₂(Pip-dtc)₂(CH₃CN)₂]_n [Pip-dtc = piperidine-1-carbodithioate; X = Br (1a), I (1b)] containing a dithiocarbamate derivative have been synthesized and structurally characterized by X-ray diffraction. The 1D infinite chains were formed from mononuclear copper units [Cu(Pip-dtc)₂] connected by bromido- or iodido-bridged copper dinuclear units that include acetonitrile ligands {i.e., [Cu₂X₂(CH₃CN)₂]}. Evaluation of the magnetic properties of 1a and 1b revealed that these complexes displayed relatively strong antiferromagnetic interactions [J = –20.4 cm^–1 (1a) and J = –18.8 cm^–1 (1b)] between unpaired electrons of the copper(II) ions through the dinuclear halido–copper(I) units. Impedance spectroscopy revealed that complexes 1a and 1b exhibit intriguing semiconducting properties at activation energies of E_a = 0.78 eV (1a) and E_a = 0.62 eV (1b). Coordination polymers 1a and 1b were then adopted as the sensitizing material in dye-sensitized solar cells (DSSCs).

New halido-bridged mixed-valence Cu^I–Cu^II coordination polymers with 1D infinite chain structures have been synthesized and structurally characterized The complexes show a relatively strong antiferromagnetic interaction and interesting semiconducting behavior. These coordination polymers were applied as sensitizing materials for DSSCs.

5-Cyanotetrazole readily forms from (CN)₂ and HN₃. The coordination abilities of the 5-cyanotetrazolate anion N₄CCN^– (ctz) towards Cu^II ions were examined and a series of complexes and coordination polymers were synthesized and characterized by single-crystal structure analyses: PPh₄[Cu(ctz)₃] (1), [Cu(ctz)₂(bipy)] (2, bipy = 2,2′-bipyridine), [CuCl(py)₄](ctz)·2py (3, py = pyridine), [Cu₂(ctz)₆Cu(CH₃CN)₂(H₂O)₂]·2CH₃CN (4a), [Cu₂(ctz)₆Cu(H₂O)₃{(CH₃)₂CO}]·3(CH₃)₂CO (4b), [Cu(ctz)₂(py)₄] (5), [Cu₂(ctz)₄(bipy)₂] (6) and [Cu₂(ctz)₂(tpm)₂(NO₃)]NO₃ [7, tpm = tris(pyrazol-1-yl)methane]. As ctz is a multidentate linker, additional neutral coligands such as monodentate py, bidentate bipy and tridentate tpm ligands were used to avoid the formation of noncrystalline polymers. The structures of 1–7 reflect the versatile coordination abilities of ctz in the various types of coordination environments of the Cu^II ions and dimensionalities of the linkages. The structures represent 1D chain motifs (1, 2 and 3), 2D layered structures (4a and 4b), mononuclear (5) and dinuclear complexes (6 and 7). Magnetic coupling phenomena were detected by susceptibility measurements of 1, 4a, 6 and 7, which were fitted to the magnetic models according to antiferromagnetic spin-pairing of two S = 1/2 systems (Bleaney–Bowers) for 6 (J = –0.53 cm^–1) and 7 (J = –2.91 cm^–1), to the ferromagnetic high-temperature series expansion based on the Baker 1D (S = 1/2) chain model for 1 (J = +14.4 cm^–1) and to the Néel model of ferrimagnetism for 4a. The diverse magnetic interactions between the Cu²⁺ sites are communicated by the bridging ctz anions.

Cyanotetrazolate (ctz) is a versatile ligand towards Cu^II ions and allows different kinds of linkage. Eight complexes and coordination polymers are presented with structures representing 1D chain motifs, 2D layered structures, mononuclear and dinuclear complexes. The complexes show different magnetic coupling phenomena at low temperatures.

Donor–acceptor interactions play a dominant role in descriptions of various chemical systems. The interactions of main-group Lewis bases with main-group Lewis acids has attracted interest for many years. In this article, donor–acceptor interactions in NHC–EX₃ (NHC = normal and abnormal N-heterocyclic carbene; E = B, Al, Ga; X = H, F, Cl, OH, NH₂, CH₃, CF₃) adducts have been investigated within the realms of DFT and atoms-in-molecules (AIM) theory. Substituents attached to the E atom have a profound effect on the strength and dissociation energies of the NHC–E bond. AIM analysis suggests that these donor–acceptor bonds have significant covalent character, which follows the order Al < Ga < B.

Donor–acceptor bonds in the complexes of normal and abnormal N-heterocyclic carbenes with tricoordinate group 13 elements (B, Al and Ga) have been studied by quantum chemistry. The substituents attached to the group 13 atoms are found to have a profound effect on the strengths of the donor–acceptor bonds.

The syntheses of several cobalt diglyoximate complexes connected by one or two aluminum bridges are described. The aluminum centers are supported by tunable tetradentate diamine bisphenoxide ligands. Electrochemical investigations revealed that the number of aluminum bridges and the nature of the substituents on the phenoxide ligands significantly affect the cobalt reduction potentials. The present aluminum–cobalt compounds are electrocatalysts for proton reduction to hydrogen at potentials negative relative to those of the boron- and proton-bridged analogs. The reported synthetic strategies allow modulation of the reduction potentials and the secondary coordination sphere interactions by tuning the ancillary ligands bound to aluminum.

Cobalt diglyoximate complexes connected by aluminum bridges were synthesized. The redox chemistry of these species is dependent on the number of aluminum centers and the nature of the ancillary ligand coordinated to aluminum. Proton reduction to hydrogen was observed and compared to BF₂- and proton-bridged analogs.

N-(Quinoline-8-yl-aryl)benzenesulfonamides 1–6 were successfully synthesized by the reaction of 8-aminoquinoline and various benzenesulfonyl chlorides. Then, half-sandwich ruthenium complexes 7–12 were prepared from the reactions of 1–6 with [RuCl₂(p-cymene)]₂. The synthesized compounds were characterized by NMR and FTIR spectroscopy and elemental analysis, and compounds 8 and 9 were further analyzed by X-ray diffraction. The complexes were screened for their efficiency as catalysts in the transfer hydrogenation of acetophenone derivatives to phenylethanols in the presence of KOH with 2-propanol (as hydrogen source) at 82 °C, and they all showed good activity. Complexes 10 and 12 were the most active (turnover frequency values: 703 and 734 h^–1, respectively).

A series of new half-sandwich Ru^II complexes containing sulfonamide ligands were synthesized and characterized by NMR and FTIR spectroscopy and elemental analysis, and two of the complexes were further analyzed by X-ray diffraction. We investigated the catalytic activity of these complexes in the transfer hydrogenation of a few acetophenone derivatives with the use of 2-propanol in the presence of base.

Six Mn^III complexes of general formula [Mn(L)XY], in which L is a dideprotonated Schiff base ligand N,N′-bis(pyridoxylidene)ethylenediamine (L¹H₂ or pydxen) or N,N′-bis(pyridoxylidene)-1,3-propanediamine (L²H₂ or pydxpn), X = Cl, N₃, NCS, and Y = H₂O, MeOH, EtOH, and another Mn^III compound [Mn(L¹)(H₂O)₂]Cl have been synthesized. The structures of five of the complexes were determined by single-crystal X-ray diffraction studies. The compounds show a quasireversible Mn^III/Mn^II couple at ca. 0 V (vs. Ag/AgCl) and two to three overlapping oxidations at 1.0–1.3 V, which are assigned to Mn^III/Mn^IV oxidation and ligand (phenolate) oxidation. The redox potential of the phenolate moiety reported here is very similar to the Y_z/Y_z^·+ potential of photosystem II (PS II, Y_z = tyrosine). Spectrochemical studies and DFT calculations support this assignment. The DFT calculations also show that there is considerable covalence in the metal–ligand bonds and the covalence increases with the oxidation state of the central metal ion. The geometry of the metal ion is found to be dependent on the oxidation state as well as spin state of the metal ion, the nature of the N,O-donor ligand used as model, and solvation effects. In silico stepwise one and two electron oxidation of a model pydxen-type complex shows strengthening of the metal–ligands interactions, but three-electron oxidation could significantly weaken one of the Mn–O bonds, which might trigger splitting into a diphenoxyl diradical species and a transient Mn^IV complex, in agreement with the experimental results.

Mn^III compounds of N,N′-bis(pyridoxylidene)ethylenediamine and N,N′-bis(pyridoxylidene)-1,3-propanediamine show a quasireversible Mn^III/Mn^II couple at ca. 0 V (vs. Ag/AgCl) and two to three overlapping oxidations at 1.0–1.3 V, which are assigned to Mn^III/Mn^IV and phenolate oxidations.

Recently, it has been demonstrated that the insertion of CO₂ into iridium hydrides is a crucial step in the catalytic conversion of CO₂ and H₂ into formic acid. We and others have elucidated the mechanism by which CO₂ inserts into six-coordinate iridium(III) trihydrides supported by pincer ligands; these complexes are very active catalysts for CO₂ hydrogenation. However, it has also been demonstrated that five-coordinate iridium(III) dihydrides can react with CO₂ and catalyze both thermal and electrochemical CO₂ hydrogenation. In this work, we study the mechanism of CO₂ insertion into pincer-supported five-coordinate iridium(III) dihydrides and four-coordinate iridium(I) hydrides using density functional theory. The mechanisms differ slightly between the two cases. Insertion into the five-coordinate species is a multistep process involving initial CO₂ precoordination, whereas insertion into the four-coordinate species proceeds via a single step with no prior CO₂ coordination. Both of these mechanisms are different from the pathway that was recently proposed for CO₂ insertion into six-coordinate iridium(III) trihydrides. In addition, a complete pathway for catalytic CO₂ hydrogenation using a five-coordinate iridium(III) dihydride has been calculated.

The insertion of CO₂ into iridium hydrides has been proposed as a crucial step in the iridium-catalyzed hydrogenation of CO₂. We used DFT to explore the mechanism of CO₂ insertion into five-coordinate iridium(III) dihydrides and four-coordinate iridium(I) monohydrides with pincer ligands, and also calculated the catalytic cycle for thermal CO₂ hydrogenation starting from an iridium(III) dihydride.

A nitride complex [K(thf)₂]₂[{(O₃)Nb}₂(μ-N)₂] (2), prepared from [K(DME)]₂[{(O₃)Nb}₂(μ-H)₄] (1) and N₂, was protonated with 2,6-lutidinium chloride to yield ammonia and [(O₃)NbCl₃]^– (3), where H₃[O₃] = tris(3,5-di-tert-butyl-2-hydroxy phenyl)methane. The reaction of 3 with KBHEt₃ regenerated [K(DME)]₂[{(O₃)Nb}₂(μ-H)₄] (1), thereby completing a synthetic cycle for the conversion of N₂ to NH₃. Alkylation of 2 with methyl iodide led to formation of [K(thf)][{(O₃)Nb}₂(μ-N)(μ-NMe)] (4) and [{(O₃)Nb}₂(μ-NMe)₂] (5). Treatment of 5 with pyridine afforded a terminal imide complex [(O₃)Nb=NMe(py)₂] (6). The imide monomer 6 reacted with CO₂ to give [(O₃)Nb{(MeN)₂CO}(py)] (7) and [{(O₃)Nb}₂(μ-O)₂] (8) in a 2:1 ratio, while the reaction of 6 with p-TolNCO gave an asymmetric ureate complex [(O₃)Nb{p-TolNC(O)NMe}(py)] (9).

The niobium nitride complex prepared from N₂ was protonated to generate NH₃, while the reaction with methyl iodide gave the methyl imide complex. Exposure of the imide complex to CO₂ gave the ureate complex along with the oxo-bridged dinuclear complex.

An attempt to prepare Tmp-C(NDipp)₂Li by treatment of lithium tetramethylpiperidide (Li-Tmp) with N,N′-bis(2,6-diisopropylphenyl)carbodiimide (Dipp-N=C=N-Dipp) failed, and ether degradation occurred instead, allowing the isolation of a few crystals of O=CH–CH=C(NH-Dipp)₂ (1) after hydrolytic work-up. We then investigated calcium and strontium compounds. Metalation of PrisoH [Priso = iPr₂N–C(N-Dipp)₂] with [(thf)₂Ca{N(SiMe₃)₂}₂] in refluxing hexane for 18 h yielded [{(Me₃Si)₂N}(thf)Ca(Priso)] (2). At room temperature, very few crystals of [Ca(Priso)₂]·hexane (3) precipitated after several months from a saturated hexane solution of 2. KN(SiMe₃)₂ was added to a THF solution of [(thf)₄CaI₂] and PrisoH and heated to 60 °C for several hours yielding [(thf)Ca(Priso)(μ-I)]₂ (4). Metalation of PrisoH with [(thf)₂Sr{N(SiMe₃)₂}₂] led to formation of [Sr(Priso)₂] (5) regardless of the applied stoichiometry. The reaction of N,N′-bis(2,6-diisopropylphenyl)benzamidine with KN(SiMe₃)₂ and [(thf)₄CaI₂] in THF followed by recrystallization from 1,2-dimethoxyethane (dme) solution yielded [(dme)Ca{(Dipp-N)₂C–Ph}₂] (6). The molecular structures of these compounds are discussed and compared with those of other encumbered complexes of divalent metal ions.

In N,N′-bis(diisopropylphenyl)amidinates and guanidinates of calcium the metal center is effectively shielded. Therefore drastic reaction conditions are required, with the disadvantage that side reactions such as ether cleavage and subsequent reactions also occur.

The synthesis of the classical, neutral donor–acceptor adducts Ph₂MeP–/Ph₃P–/Ph₃As–Al(OR^F)₃ and H₂O–Al(OR^F)₃ [1, 2, 3, 4, OR^F = OC(CF₃)₃] is reported. The intermediate H₂O–Al(OR^F)₃ (4) was generated by substitution of PhF in PhF–Al(OR^F)₃ with H₂O and was analyzed in a long-term NMR study over 22 days. This Brønsted acidic system was used in orienting experiments to protonate phosphanes such as PMePh₂, PPh₃, PCy₃, P(tBu)₃, and PCy₂[2,4,6-(iPr)₃C₆H₂]. Depending on the use of one or two equivalents of PhF–Al(OR^F)₃, the new weakly coordinating anions [(R^FO)₃Al(μ-OH)Al(OR^F)₃]^– or [HOAl(OR^F)₃]^– were obtained. However, in dependence of the steric bulk of the phosphanes, stable and unreactive R₃P–Al(OR^F)₃ adducts were also observed in the NMR experiments. The absolute acidity of the key H₂O–Al(OR^F)₃ adduct was evaluated by the relaxed COSMO cluster-continuum (rCCC, COSMO = conductor-like screening model) model in fluorobenzene solution. For a 0.001 M solution of H₂O–Al(OR^F)₃, the medium acidity resulted as –986 kJ mol^–1 or a pH_abs value of 173. Long-term hydrolysis of H₂O–Al(OR^F)₃ (4), probably to give HOR^F and HOAl(OR^F)₂ followed by trimerization, gave [HOAl(OR^F)₂]₃ (10), which was identified by X-ray diffraction.

Small donor ligands such as Ph₂MeP, Ph₃P, Ph₃As, or even H₂O form classical donor–acceptor adducts with the Lewis superacid Al(OR^F)₃ [R^F = C(CF₃)₃]. FLP-like (FLP = frustrated Lewis pair) combinations of this Lewis acid, phosphanes, and water then lead to [HPR₃]⁺ and two new weakly coordinating anions [HOAl(OR^F)₃]^– and [(^FRO)₃Al(μ-OH)Al(OR^F)₃]^–. The absolute acidity of H₂O–Al(OR^F)₃ is evaluated.

Properties of the Eu^III/Eu^II redox couple, in the presence of one of a group of different ligands of ligands, were investigated using several electrochemical methods. Ligands used in this study included cyclodextrins, polyazamacrocycles and poly(aminocarboxylates). The poly(aminocarboxylate) containing ligands currently used as MRI contrast agents (DTPA, DOTA) as well as newly developed ligands [1,4-DOTA(GAC₁₂)₂, 1,7-DOTA(GAC₁₂)₂] with potential use as MRI contrast agents were studied. Cyclic voltammetry, phase sensitive AC voltammetry, DC polarography and highly effective electrochemical impedance spectroscopy were utilised to elucidate the mechanism of the reduction/oxidation of the Eu ion in the presence of these compounds. Stability constants of the Eu^III and/or Eu^II complexes and heterogeneous rate constants of the charge transfer were determined. Theoretical calculations of molecular volumes and diffusion coefficients were performed as well.

CV, AC voltammetry, DC polarography and impedance spectroscopy were utilized to elucidate the mechanism, stability constants and heterogeneous rate constants of the charge transfer of the reduction/oxidation of the Eu^III/Eu^II ion pair in the presence the newly developed ligands 1,4-DOTA(GAC₁₂)₂ and 1,7-DOTA(GAC₁₂)₂ with potential use as MRI contrast agents.

The symmetry-forbidden cyclometalation of (silox)₂W=N^tBu (1, silox = OSi^tBu₃) to (silox)(^tBuN)W(H)(κO,κC-OSi^tBu₂CMe₂CH₂) (2) was investigated by kinetics [ΔH^‡ = 19.2(9) kcal/mol; ΔS^‡ = –23(3) eu; ΔG^‡(25 °C) = 26.1(10) kcal/mol], isotopic labeling {[D₅₄]1 → [D₅₄]2; k_H/k_D = 2.7(4)}, and equilibrium studies [ΔH° = –6.7(3) kcal/mol; ΔS° = –12.1(8) eu; ΔG°(25 °C) = –3.1(4) kcal/mol]. The crystal structure of 2 reveals a pseudo-square-pyramidal structure that can be viewed as a distorted tetrahedron with the W–H and W–C bonds occupying one site. The addition of H₂ (or D₂) to 1 proceeds similarly to afford (silox)₂(^tBuN=)WH₂ (3), and the addition of H₂ to 2 also affords 3, but labeling experiments show that it proceeds via 1. Phosphane bases with cone angles < 160° trigger the cyclometalation of 1 to 2 in < 5 min, and PMe₃ catalyzed the dihydrogen addition to 1. Quantum mechanics/molecular mechanics (QM/MM) calculations support the experimental findings and show that Lewis bases promote σ/π mixing. The experimentally observed intermediate (silox)₂(^tBuN=)WPMe₃ (1-PMe₃) has a (d_yz)² (i.e., π²) ground state in contrast to the (d)² (i.e., σ²) configuration of 1. The σ/π mixing circumvents the constraints of orbital symmetry for both cyclometalation and dihydrogen addition.

The symmetry-forbidden cyclometalation of (silox)₂W=N^tBu (1, silox = OSi^tBu₃) to (silox)(^tBuN)W(H)(κO,κC-OSi^tBu₂CMe₂CH₂) (2) and the oxidative addition of dihydrogen to give (silox)₂(^tBuN=)WH₂ (3) are catalyzed by phosphane bases with cone angles < 160°. Quantum mechanics/molecular mechanics (QM/MM) calculations support the experimental findings and show that Lewis bases promote σ/π mixing.

The structural organization and magnetic properties of Mn^III complexes with meso-tetraphenylporphyrin (TPP), bis(3,5-di-tert-butylsalicylidene)ethylenediamine (^tBuSalen), and bis(salicylidene)ethylenediamine (Salen) capping ligands assembled with phosphinate ligands such as H₂PO₂^–, PhHPO₂^– and Ph₂PO₂^– have been investigated. The structural organization and, thus, the magnetic properties in this series depends on the nature of both the capping and bridging ligands. The hypophosphite ion (H₂PO₂^–) and the diphenylphosphinate ion (Ph₂PO₂^–) act as bridging ligands to form 1D polymeric structures [{Mn(TPP)O₂PH₂}₂·H₂O·EtOH]_n and [Mn(Salen)O₂PPh₂]_n, among which only the former presents single chain magnet behaviour; the pronounced nonalignment of the anisotropy axes explains the absence of such behaviour in the latter. The phenylphosphinate ion (PhHPO₂^–) and the diphenylphosphinate ion (Ph₂PO₂^–) act as monodentate ligands in the complexes with ^tBuSalen and TPP as capping ligands, respectively. The diphenylphosphinate ion acts as both a bidentate ligand and charge-compensating anion in [Mn₂(^tBuSalen)₂(O₂PPh₂)(EtOH)₂⁺(Ph₂PO₂^–)·H₂O].

The synthesis of Mn^III complexes capped by tetradentate ligands and assembled by phosphinate ligands is reported. The phosphinate coordination mode is influenced by the steric hindrance of both the phosphinate and the tetradentate ligands. Two 1D polymeric structures have been obtained, one of which presents single chain magnet (SCM) behaviour.

A new pyridine-substituted dithiolene complex, PPh₄[Au(4-pdddt)₂] (3), was prepared and characterised. Cyclic voltammetry shows three redox processes corresponding to the interconversion between dianionic, monoanionic, neutral and cationic states, as often presented by this type of bis(dithiolene) complexes. However, the last oxidation process in this compound leads to a polymerised species obtained as an electrodeposited film. By potentiostatic electrodeposition, thin films of either the neutral gold complex, [Au(4-pdddt)₂] (4), or the polymerised cationic species can be obtained. Both films absorb strongly in the NIR region and have properties consistent with the incorporation of the intact metal bis(dithiolene) complex. A mechanism for polymerisation through formation of S–S interligand bonds is proposed.

Pyridine-substituted dithiolene gold complex [Au(4-pdddt)₂] shows three redox processes corresponding to the interconversion between dianionic, monoanionic, neutral and cationic states, the last one corresponding to a polymerised species obtained as an electrodeposited film.

For the first time, single crystals of KPbBP₂O₈ with sizes up to 18 × 13 × 6 mm have been grown from a stoichiometric mixture of its components by the top seed growth method. The crystal structure was determined from single-crystal X-ray data: tetragonal, space group I2d, a = 7.1464(7) Å, c = 13.8917(16) Å, Z = 4. It exhibits an isolated [BP₂O₈]^3– unit that is built from nearly ideal tetrahedral BO₄ and PO₄ groups, which are connected to each other alternatively by corner-sharing O atoms to make a 12-membered ring. Transmission spectroscopy illustrates that the UV cutoff edge is at approximately 235 nm. Furthermore, IR spectroscopy, thermal analysis, and second-harmonic generation (SHG) measurements were also performed on the reported material.

KPbBP₂O₈ is synthesized and its structure is determined by single-crystal X-ray diffraction. Thermal and XRD analysis show that KPbBP₂O₈ melts congruently. IR and UV/Vis spectroscopy and second-harmonic generation measurements are also performed on the reported material.

The evaluation of a new azacrown ether ligand bis{[3-(pyridin-4-yl)-1H-pyrazol-1-yl]methyl}diaza-18-crown-6 (b3pd), which contains pendant p-pyridylpyrazole arms connected by diaminomethane linkers, identified a tendency to undergo retro-Mannich fragmentation in the presence of transition-metal ions. However, treatment of b3pd with potassium perchlorate or potassium iodide prior to complexation with transition-metal ions imparted a resistance to fragmentation, such that crystallisation of coordination polymers from concentrated solutions after several weeks was possible. Four solid-state structures containing Kb3pd were isolated: a perchlorate salt (1), a divalent manganese 1D coordination polymer [Mn(Kb3pd)(DMF)₄]·2ClO₄·I₃ (2, DMF = N,N-dimethylformamide), a cuprous 2D coordination network [Cu₂(Kb3pd)₂(I₃)(I)₃]·3H₂O (3) and a cuprous 1D coordination polymer [Cu(Kb3pd)(I)₂] (4). Additionally, the retro-Mannich process was investigated by in situ FTIR spectroscopy, mass spectrometry, crystallography and by the isolation of a cobalt complex ligated by a partially fragmented ligand, mono{[3-(pyridin-4-yl)-1H-pyrazol-1-yl]methyl}diaza-18-crown-6 (m3pd). The composition of the cobalt complex was found to be [CoCl₃(Hm3pd)]·H₂O (5).

Diaza-18-crown-6 ligands functionalised with diaminomethane linkers are unstable in the presence of selected divalent transition-metal ions. Pretreatment of the ligands with potassium salts prevents degradation by blocking the central coordination region. Iodide redox chemistry also affects the coordination-polymer motif.

The ambiphilic and small-bite-angle diphosphanylborane ligands Ph₂PCH(PPh₂)CH₂B(C₈H₁₄) (2) and Ph₂PCH₂CH[B(C₈H₁₄)]PPh₂ (3) containing the Lewis acidic 9-boranorbornyl group B(C₈H₁₄) have been prepared in one step by regioselective anti-Markovnikov hydroborations of 1,1-bis(diphenylphosphanyl)ethylene and 1,2-bis(diphenylphosphanyl)ethylene with 9-borabicyclo[3.3.1]nonane (9-BBN) under relatively drastic reaction condition. The coordination properties of Ph₂PCH₂CH₂B(C₈H₁₄) (1) and the newly prepared 2 and 3 towards the tungsten nitrosyl fragment {WNO}⁶ have been studied structurally and spectroscopically. Herein, we report the cis and trans tungsten nitrosyl complexes cis-[W(CO)₂(1)₂(NO)(Cl)] (cis-4a), cis-[W(CO)₂(1)₂(NO)(H)] (cis-4b), trans-[W(CO)₂(1)₂(NO)(Cl)] (trans-4a), trans-[W(CO)₂(1)₂(NO)(H)] (trans-4b), cis-[W(CO)₂(2)(NO)(Cl)] (cis-5a), cis-[W(CO)₂(2)(NO)(H)] (cis-5b), cis-[W(CO)₂(3)(NO)(Cl)] (cis-6a), cis-[W(CO)₂(3)(NO)(H)] (cis-6b), which were readily obtained from straightforward ligand-substitution reactions of the tungsten carbonyl nitrosyl precursor [W(NO)(CO)₄(ClAlCl₃)] in tetrahydrofuran. The crystal structures of the tungsten chloride complexes cis-4a, trans-4a, and cis-5a revealed that the trialkyl boron centers are free pendants in the secondary coordination spheres, whereas in the hydride complexes trans-4b, cis-5b, and cis-6b the hydride ligand trans to the nitrosyl ligand is σ coordinated to the tethered B(C₈H₁₄) group and form three-center, two-electron (3c–2e) W–H–B bonds, which were observed in their crystal structures. The authenticity of the 3c–2e W–H–B bond in the tungsten hydride complex cis-5b was further checked by a DFT structural optimization and natural bond order (NBO) analysis.

The coordination properties of phosphanylborane ligands in newly synthesized tungsten carbonyl nitrosyl complexes are explored by multinuclear NMR and IR spectroscopy, single-crystal X-ray structure analyses, and DFT calculations.

The new carbodiimide compound La₃Cl(CN₂)O₃ was obtained by a solid-state metathesis reaction from LaOCl and Li₂(CN₂) at 750 °C in a fused tube. Differential scanning calorimetry of the reaction mixture was performed. The crystal structure of La₃Cl(CN₂)O₃ was determined by single-crystal X-ray diffraction studies (space group Cmcm, No. 63). The luminescent properties of the Eu³⁺- and Tb³⁺-doped compounds are reported.

The new luminescent material La₃Cl(CN₂)O₃:Ln 5 mol-% (Ln = Eu³⁺ or Tb³⁺) was successfully synthesized by a simple reaction of LaOCl with Li₂CN₂ (+ LnCl₃).

Binding Ni^II to the terminal amine of a peptide depresses totally its nucleophilic character as measured by the rate constant of the reaction of the peptide with 4-nitrophenyl acetate. The structure of Ni^II(GGGGG) in aqueous solutions was determined by this technique. The results indicate that the ratio of complexes in which the nickel is bound to four deprotonated peptide nitrogen atoms to those in which the nickel is bound to the terminal amine and three deprotonated peptide nitrogen atoms increases as the pH increases. At pH 9.0, this ratio is approximately 1.

We measured the nucleophilic properties of the terminal amine of a Ni(peptide) complex as a tool to elucidate the ligation sites of the cation.

The facile two-electron reduction of the phosphaalkyne tBuC≡P by the U^III cyclopentadienyl–pentalene mixed-sandwich complex [U(η⁵-C₅Me₅){η⁸-C₈H₄(SiiPr₃)₂}] is reported. A single-crystal X-ray structural analysis of the diuranium(IV) product [(U{η⁵-C₅Me₅}{η⁸-C₈H₄(SiiPr₃)₂})₂(μ-tBuCP)] shows that it contains a slightly unsymmetrical, bridging μ-η²:η¹-ligated phosphaalkene dianion.

The two-electron reduction of the phosphaalkyne tBuC≡P by the U^III mixed-sandwich complex [U(η⁵-C₅Me₅){η⁸-C₈H₄(SiiPr₃)₂}] yields the diuranium(IV) product [(U{η⁵-C₅Me₅}{η⁸-C₈H₄(SiiPr₃)₂})₂(μ-tBuCP)], which contains a μ-η²:η¹-ligated phosphaalkene dianion.

Hydrolysis of half-sandwich-type platinum metal cations with the general formula [M(η⁶-arene)(H₂O)₃]²⁺ {M = Ru, Os; η⁶-arene = benzene, toluene, 1-methyl-4-isopropylbenzene (p-cym), or 1,3,5-triisopropylbenzene (tri-iPr)} or [Ir(η⁵-Cp*)(H₂O)₃]²⁺ (Cp* = pentamethylcyclopentadienyl anion) was studied in aqueous solution in the presence of 0.20 M KNO₃ or KCl as a background electrolyte to explore the effects of the type of metal ion, the moderately coordinating monodentate chloride ion, and the electron-donating ability of the arene ligand. Replacement of Ru by Os enhances the formation of the biologically less-active, triple hydroxido-bridged dimer, [{M(η⁶-arene)}₂(μ²-OH)₃]⁺, whereas in the presence of Cl^– complete hydrolysis is suppressed owing to the formation of various chlorido and mixed chlorido/hydroxido species as intermediates. A linear relationship was found between the stability constants of the [{Ru(η⁶-arene)}₂(μ²-OH)₃]⁺ complexes in the presence of arenes with different electron-donating abilities and various atomic and molecular parameters of the corresponding [Ru(η⁶-arene)(H₂O)₃]²⁺ cations; the triisopropylbenzene derivative was the most resistant to hydrolysis. The results of this study may help in rationalizing the bioactivity of anticancer half-sandwich metal complexes and can contribute to the rational design of metal compounds with increased biological activity.

The hydrolytic properties of half-sandwich [M(η⁶-arene)(H₂O)₃]²⁺ (M = Ru, Os; η⁶-arene = benzene, toluene, 1-methyl-4-isopropylbenzene, 1,3,5-triisopropylbenzene) or [Ir(η⁵-Cp*)(H₂O)₃]²⁺ (Cp* = pentamethylcyclopentadienyl) cations can be tuned by the proper selection of the arene system and by modification of the metal ion to make them more resistant to hydrolysis.

The β-lactamase activity of two previously reported dinuclear cobalt(II) complexes is described. The two complexes, [Co₂(CO₂EtH₂L1)(CH₃COO)₂](PF₆) (CO₂EtH₃L1 = ethyl 4-hydroxy-3,5-bis{[(2-hydroxyethyl)(pyridin-2-ylmethyl)amino]methyl}benzoate) and [Co₂(CO₂EtL2)(CH₃COO)₂](PF₆) (CO₂EtHL2 = ethyl 4-hydroxy-3,5-bis{[(2-methoxyethyl)(pyridin-2-ylmethyl)amino]methyl}benzoate), differ in that the latter has methyl ether donors in contrast to potentially nucleophilic alkoxide donors in the former. They thus offer a direct comparison of potential ligand-centered nucleophiles. The complexes were treated with the antibiotic penicillin G and the commonly used lactamase substrate nitrocefin. On the basis of mass spectrometry, UV/Vis, and infrared spectroscopy measurements in solution, it was shown that only [Co₂(CO₂EtH₂L1)(CH₃COO)₂](PF₆) was capable of hydrolyzing both penicillin and nitrocefin, and that the hydrolysis-initiating nucleophile was an alkoxide donor. Analysis of kinetic data showed that nitrocefin binding occurs more rapidly {k₁ = [(2.5 × 10³) ± (1.9 × 10¹)] M^–1 min^–1} than its subsequent hydrolysis {k₂ = [(1.6 × 10^–1) ± (8.1 × 10^–4)] min^–1}. The pH dependence of nitrocefin hydrolysis by [Co₂(CO₂EtH₂L1)(CH₃COO)₂]⁺ displays two pK_a values (6.88 ± 0.74; 8.45 ± 0.68), the first of which is attributed to the deprotonation of a Co^II alcohol, and the second of which is proposed to arise from Co^II–OH₂. For [Co₂(CO₂EtL2)(CH₃COO)₂]⁺, only one relevant pK_a1 (8.47 ± 0.14) is evident, assigned to a terminal water molecule. By using variable-temperature/variable-field magnetic circular dichroism (VTVH MCD), it was demonstrated that the sign of the magnetic exchange coupling parameter (J) for the parent dinuclear cobalt(II) complexes changes upon binding of the substrate. This work presents one of the few cobalt(II) β-lactamase model complexes that is capable of facile hydrolysis of β-lactam substrates, an outcome that provides a good benchmark to investigate the reaction mechanism(s) applicable to the enzyme systems.

Two dinuclear Co^II complexes were tested for their ability to hydrolyze β-lactam substrates. The [Co₂(CO₂EtH₂L1)(CH₃COO)₂]⁺ complex is reactive towards nitrocefin and penicillin, whereas [Co₂(CO₂EtL2)(CH₃COO)₂]⁺ is unreactive. The difference between the two complexes is due to the presence of an alkoxide in the former.

The essential but also toxic gaseous signaling molecule nitric oxide is scavenged by the reduced vitamin B₁₂ complex cob(II)alamin. The resulting complex, nitroxylcobalamin [NO^–-Cbl(III)], is rapidly oxidized to nitrocobalamin (NO₂Cbl) in the presence of oxygen; however, it is unlikely that nitrocobalamin is itself stable in biological systems. Kinetic studies on the reaction between NO₂Cbl and the important intracellular antioxidant, glutathione (GSH), are reported. In this study, a reaction pathway is proposed in which the β-axial ligand of NO₂Cbl is first substituted by water to give aquacobalamin (H₂OCbl⁺), which then reacts further with GSH to form glutathionylcobalamin (GSCbl). Independent measurements of the four associated rate constants k₁, k_–1, k₂, and k_–2 support the proposed mechanism. These findings provide insight into the fundamental mechanism of ligand substitution reactions of cob(III)alamins with inorganic ligands at the β-axial site.

Kinetic studies on the reaction of nitrocobalamin (NO₂Cbl) with glutathione show that glutathionylcobalamin (GSCbl) is formed via an aquacobalamin (H₂OCbl⁺) intermediate. This reaction pathway is demonstrated by independently determining individual rate constants for each step.

A bis(β-diketone), 1,3-bis(4,4,4-trifluoro-1,3-dioxobutyl)phenyl (BTP), which contains a trifluorinated alkyl group, has been exploited to obtain three series of visible-light sensitive dinuclear rare-earth complexes with the general formula [Ln₂(BTP)₃L₂] [Ln = Nd, L = DME (1), bpy (2), and phen (3); Ln = Yb, L = DME (4), bpy (5), and phen (6); Ln = Er, L = DME (7); DME = ethylene glycol dimethyl ether, bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline]. An X-ray crystallographic analysis revealed that complexes 1, 2, 4, 5, and 7 are triple-stranded helical dinuclear structures that are formed by three bis(bidentate) ligands with two lanthanide ions. The room-temperature near-IR luminescent properties of complexes 1–6 show that this bis(β-diketone) can effectively sensitize rare earths (Nd³⁺, Yb³⁺) and produce typical near-infrared luminescence upon excitation with visible light of the corresponding Nd³⁺ and Yb³⁺ ions. Additionally, two bidentate nitrogen ancillary ligands, 2,2-bipydine (bpy) and 1,10-phenanthroline (phen), have been applied to enhance the NIR luminescent properties.

A bis(β-diketone), 1,3-bis(4,4,4-trifluoro-1,3-dioxobutyl)phenyl (BTP), has been designed and employed for the synthesis of three series of new BTP lanthanide complexes that featured promising NIR luminescence.

Hydrogenation of the neutral bis(allyl) complexes of the early lanthanides [Ln(Me₃TACD)(η³-C₃H₅)₂] [(Me₃TACD)H = 1,4,7-trimethyl-1,4,7,10-tetraazacyclododecane, Me₃[12]aneN₄] with phenylsilane gave the tetranuclear octahydrido complexes [Ln(Me₃TACD)(μ-H)₂]₄ [Ln = Ce (1-Ce), Pr (2-Pr)] or the dinuclear allyl/hydrido complexes [Ln(Me₃TACD)(η³-C₃H₅)(μ-H)]₂ [Ln = Nd (3-Nd), Sm (4-Sm)], which were isolated and characterized. The structures of 1-Ce and 2-Pr are constructed of a tetrahedral Ln₄H₈ core. Single-crystal X-ray diffraction analyses of 3-Nd and 4-Sm revealed a C₂ symmetric planar Ln₂H₂ core. The experimental structures agreed with the results of DFT calculations, which predict that the nuclearity of the dihydrido complexes depend on the ionic radius of the metal. Compounds 1-Ce, 2-Pr, 3-Nd and 4-Sm were tested as catalysts in the copolymerization of cyclohexene oxide with CO₂ to give highly carbonate-linked copolymers with moderate activities.

Tetranuclear [Ln(Me₃TACD)(μ-H)₂]₄ [Ln = Ce (1-Ce), Pr (2-Pr)] and dinuclear [Ln(Me₃TACD)(η³-C₃H₅)(μ-H)]₂ [Ln = Nd (3-Nd), Sm (4-Sm)] have been obtained by treatment of the corresponding bis(allyl) Me₃TACD complexes with phenylsilane and were tested as catalysts in the copolymerization of cyclohexene oxide with CO₂.

In this microreview, we focus on our work on the development of group 5 imido and bis(imido) semihydrogenation catalysts in the context of previous stoichiometric studies on d⁰ metal–ligand multiple-bond activations of strong σ bonds and both stoichiometric and catalytic studies on H₂ activation and hydrogenation by d² group 5 complexes. These studies develop electronic structure models and mechanistic analyses necessary for the application of catalytic reactions involving 1,2-addition reactions of σ-bonded substrates across early transition metal–ligand multiple bonds. Extension of these studies to the second and third row group 5 imido complexes has led to the development of mechanistically distinct hydrogenation catalysts with product selectivities not readily obtainable with traditional late transition-metal catalysts that employ H₂ as the reductant.

The selective, catalytic semihydrogenation of alkynes by group 5 imido and bis(imido) complexes is presented from synthetic and mechanistic perspectives in the context of previous stoichiometric studies on the d⁰ metal–ligand multiple-bond activation of strong σ bonds and both stoichiometric and catalytic studies on H₂ activation and hydrogenation by d² group 5 complexes.

The utility of the fac-[RuH₃(PR₃)₃]^– anion (R = Ph, C₆H₄-4-Me) for the preparation of new oligonuclear transition metal polyhydrides has been examined. The lithium salts [Li(thf)_x{Ru(μ-H)₃(PPh₃)₃}] {1: R = Ph, x = 3; 1′: R = C₆H₄-4-Me (Tol), x = 2.5} react with [Cp*RuCl]₄ (Cp* = C₅Me₅), ZnCl₂, and CuCl(SMe₂) to form new oligonuclear polyhydrido complexes. The compounds [Cp*Ru(μ-H)₃Ru(PR₃)₃] (2: R = Ph, 2′: R = Tol), [Zn{Ru(μ-H)₃(PPh₃)₃}₂] (3), and [Cu₂{Ru(μ-H)₃(PPh₃)₃}₂] (4) were synthesized and characterized by multinuclear NMR and IR spectroscopy, and microanalysis. The molecular structures were determined by X-ray crystallography. Density functional theory calculations at the PBE-D3/def2-TZVP level support the proposed structures of the new polyhydride complexes. The impact of intramolecular London dispersion interactions on the optimized geometries is discussed.

Di-, tri-, and tetranuclear polyhydride complexes with a fac-[RuH₃(PPh₃)₃]^– anion are accessible by salt metathesis of [Li(thf)₃{Ru(μ-H)₃(PPh₃)₃}] (1) with [Cp*RuCl]₄, ZnCl₂, and CuCl(SMe₂). Complexes 2–4 have been characterized by X-ray crystallography and spectroscopic techniques. DFT calculations support the structural analyses and examine the influence of the London dispersion interactions.

N,N-Diethylcarbamates [NbE(O₂CNEt₂)₃] (E = O, S) have been prepared in high yields by treating NbOCl₃ or [NbSCl₃(CH₃CN)₂] with CO₂/NHEt₂ in toluene at approximately –10 °C. The products were characterized by spectroscopic techniques, elemental analysis and X-ray diffractometry in the case of [NbO(O₂CNEt₂)₃]. The molecular structure of the latter consists of a niobium centre coordinated to the oxido moiety and six O atoms belonging to bridging and bidentate carbamates, in a slightly distorted pentagonal-bipyramidal arrangement. The structures of both [NbE(O₂CNEt₂)₃] compounds were reproduced by DFT calculations, which show substantial similarity despite the different nature of the chalcogen atoms.

N,N-Diethylcarbamates [NbE(O₂CNEt₂)₃] (E = O, S) have been prepared from NbECl₃ and fully characterized. The structures of both products have been optimized by DFT calculations.

This paper reports a new approach towards the construction of a multifunctional periodic mesoporous organosilica (PMO), which integrates a range of advantages, such as mesoporous structural order, selective nucleobase-recognition properties, stimuli-responsive site-specific delivery of anticancer agents to cancer tissues, and Cu²⁺ adsorption, into a single entity. First, the appropriate organic-functional-receptor precursor was synthesized by a chemical process and used to fabricate a multifunctional pyridine-containing PMO material (DMPy-PMO) by a hydrolysis and condensation route. The designed organic–inorganic hybrid mesoporous silica chemosensor showed an intrinsic selective recognition of nucleobase, specifically thymidine, through multipoint hydrogen-bonding interactions with suitably arrayed receptor sites loaded into the rigid silica framework. An in vitro cytotoxicity test showed that the designed chemosensor materials have good biocompatibility and, therefore, could be promising candidates for the delivery of a range of therapeutic agents. Confocal laser scanning microscopy (CLSM) confirmed that the material can be internalized effectively by cancer cells (MCF-7 cells). In addition, the DMPy-PMOs showed efficient Cu²⁺ ion removal capacity at pH 5.0 with significantly high levels of adsorption (0.95 mmol g^–1). These results suggest that the prepared multifunctional PMO hybrid has potential use as a smart material for a range of applications, such as biomolecule recognition, biomedical applications, and as an efficient adsorbent for the removal of metal ions.

A multifunctional mesoporous silica hybrid is presented, in which the receptor site plays a key role in nucleobase recognition, pH-induced delivery of anticancer agents, and as a metal binding site for Cu²⁺ ions. The pyridine-containing material selectively recognizes thymidine, is an effective potential drug-carrier system in cancer therapy, and is an efficient adsorbent for Cu²⁺ removal.

Dinuclear rhodium complexes have attracted considerable attention as a result of their chemical and biological reactivity. We report herein the synthesis and structural elucidation by combined spectroscopic methods of a new rhodium complex containing N-methyl-D-phenylalaninate (NMfO^–) as a chiral ligand. It has been demonstrated that the structure of the chiral complex formed in water is independent of the ligand/metal molar ratio, the type of solvent, and reaction time, as shown by HPLC and ESI-MS analyses. The steric structure of the isolated and identified [Rh₂(OAc)₂(OfMN)₂] complex was determined by chiroptical (VCD, ECD) and NMR spectroscopy supported by DFT calculations. By this combined analysis, our studies have shown that the complex formed has two chiral ligands chelated through the O and N atoms of their carboxylate and sec-amino groups, respectively, in the vicinity of the two bridging acetate ligands.

The steric structure and binding mode of the isolated new chiral dirhodium complex [Rh₂(OAc)₂(OfMN)₂] have been determined by chiroptical (VCD, ECD) and NMR spectroscopy supported by DFT calculations.

Metalloligands L1 and L2 consisting of directional bis(terpyridine)ruthenium(II) units and bipyridine moieties were constructed by amide formation. From these metalloligands two Ru–Pt heterobimetallic complexes 1 and 2 were derived by a building-block method by means of platination with [PtCl₂(dmso)₂]. Both bimetallic complexes 1 and 2 feature metal-to-ligand charge transfer (MLCT) absorptions, and emission occurs at room temperature in fluid solution from ³MLCT(Ru) states in all cases. Energy transfer from platinum to ruthenium is observed in 2 but not in 1 (light harvesting). The one-electron-reduced species [1]^– and [2]^– were prepared by reduction of 1 and 2 with decamethylcobaltocene. EPR spectra and DFT calculations reveal that the spin density is localized at the tpy–CO/Ru (tpy = terpyridine) site in [1]^–, whereas it is centered at bpy–CO/Pt (bpy = 2,2′-bipyridine) in [2]^–. Efficient photoinduced electron transfer from triethanolamine to 1 and 2 is feasible by excitation at 500 nm [MLCT(Ru)].

Heterobimetallic complexes Pt–Ru (1) and Ru–Pt (2) were constructed from directional bis(terpyridine) ruthenium(II) and bipyridinedichloroplatinum(II) moieties. The photophysical properties of 1 and 2 as well as their responses to one-electron reduction (thermal and photochemical) were elucidated by EPR spectroscopy, DFT calculations, and Stern–Volmer plots.

The connection of flexible protodendritic wedges to the bis-tridentate rigid polyaromatic ligand L1 provides amphiphilic receptors L5 and L6; their reduced affinities for complexing trivalent lanthanides (Ln = La, Y, Lu) in organic solvent (by fifteen orders of magnitude!) prevent the formation of the expected dinuclear triple-stranded helicates [Ln₂(Lk)₃]⁶⁺. This limitation could be turned into an advantage because L1 or L6 can be treated with [Ln(hfac)₃] (Hhfac = 1,1,1,5,5,5-hexafluoro-2,4-pentanedione) to give neutral single-stranded [Ln₂(Lk)(hfac)₆] complexes with no trace of higher-order helicates. Whereas ligands L1 and L5 are not liquid crystals, L6 can be melted above room temperature (41 °C) to give a nematic mesophase, and its associated dinuclear helical complex [Y₂(L6)(hfac)₆] self-organises at the same temperature into a fluidic smectic mesophase.

The lipophilic dendritic ligand L6 selectively reacts with trivalent yttrium hexafluoroacetylacetonate (hfac) to give the liquid-crystalline single-stranded dinuclear helicate [Y₂(L6)(hfac)₆], which self-organises into an SmA mesophase.

A mixed-ligand 3D metal–organic framework, [Ni(1,2-cpd)(bpe)(H₂O)]_n (1) [1,2-cpd = cis-cyclopentane-1,2-dicarboxylate, bpe = 1,2-di(4-pyridyl)ethylene], has been constructed. Topological analysis revealed that the structure is a 3-c uninodal 2D + 2D → 3D polycatenated net with the Schläfli symbol 6³. The compound is catalytically active towards the epoxidation reaction in heterogeneous media. It catalyses almost all types of olefinic substrates with equal efficiency. After reaction it can be recovered quite easily and can be used for further reaction without any loss of activity for several cycles. Variable-temperature magnetic susceptibility measurement reveals the presence of a weak antiferromagnetic interaction in compound 1.

A mixed-ligand nickel–organic framework has been made that has a 3-c uninodal 2D + 2D → 3D polycatenated net. It can catalyse almost all types of olefinic substrates with equal efficiency and be used for several cycles without loss of any catalytic activity.

CdV₂O₆ and Cd₂V₂O₇ were successfully synthesized by a simple hydrothermal process. The effects of the hydrothermal temperature and pH on the phase transition between CdV₂O₆ and Cd₂V₂O₇ were investigated in detail. That the Cd₂V₂O₇ phase could transform into CdV₂O₆ was attributed to polymerization of vanadate in an acidic environment as the V/O ratio increased as the pH decreased. V₂O₇^4– was stable in a neutral or alkaline environment at an identical hydrothermal temperature, therefore, the Cd₂V₂O₇ phase was obtained after hydrothermal treatment for 24 h. Because the degree of hydrolysis of NH₄Cl increased with increasing temperature in the solution, the increased temperature accelerated the speed of the pH decrease. Therefore, the hydrothermal temperature played an important part in the phase transition between CdV₂O₆ and Cd₂V₂O₇. CdV₂O₆ and Cd₂V₂O₇ showed high photocatalytic activity for the degradation of methylene blue under visible-light irradiation.

CdV₂O₆ and Cd₂V₂O₇ are controllably synthesized by a simple hydrothermal method. The influence of the reaction parameters (pH, hydrothermal temperature) on the phase transition between CdV₂O₆ and Cd₂V₂O₇ and the relationship between the phases and photocatalytic activities are investigated.

Four azide–copper coordination polymers, [Cu₂L¹(N₃)₄]_n, [Cu₂L²(N₃)₄]_n, [Cu₂L^3R(N₃)₄]_n, and [Cu₂L^3S(N₃)₄]_n, were synthesized by using pybox [pyridine-2,6-bis(oxazolines)] as coligands {L¹: 2,6-bis(4,5-dihydrooxazol-2-yl)pyridine; L²: 2,6-bis(5,6-dihydro-4H-1,3-oxazin-2-yl)pyridine; L^{3R or 3S}: 2,6-bis[(R or S)-4-benzyl-4,5-dihydrooxazol-2-yl]pyridine}. Compounds 1 and 2 possess similar 1D infinite azide–copper hexagonal tapes with three types of N₃ bridges (two single end-on N₃ bridges and one double end-on N₃ bridge). Compounds 3R and 3S possess an azide–copper 2D honeycomb layer with two types of N₃ bridges (a single end-to-end N₃ bridge and a double end-on N₃ bridge). The chirality of these enantiopure layered structures is controlled by the addition of the chiral pybox ligand in the synthesis, which is very rare for the reported azide–copper coordination polymers. The double end-on N₃ bridge transfers mainly ferromagnetic exchange coupling interactions in these four compounds. Owing to the steric hindrance of the pybox ligands, the interchain and interlayer separations are broadened, which weakens the magnetic interactions between them. Thus, no long-range ferromagnetic ordering was observed above 1.8 K. A magnetostructural correlation was also discussed in detail.

A series of pybox ligands were used as effective coligands to construct four azide–copper low-dimensional coordination polymers. Two of these polymers possess similar 1D infinite azide–copper hexagonal tapes and the other two possess a very interesting enantiopure 2D honeycomb layer structure. Magnetic studies revealed the weak ferromagnetic characters of these complexes.

The useful optoelectronic properties of cationic iridium(III) complexes have been exploited in diverse applications, from visual displays to biological probes to analytical sensors. It is thus not surprising to note the increased recent efforts to document, understand, and ultimately control the photophysical and electrochemical properties of the archetypal cationic iridium(III) complex [(ppy)₂Ir(bpy)]⁺, in which ppyH = 2-phenylpyridine and bpy = 2,2′-bipyridine, and decorated versions thereof. Of the ligand architectures explored, the greatest attention has been devoted to ligands that incorporate the common pyridine unit. In this Microreview, we survey the salient emission and electrochemical properties of cationic iridium(III) complexes of the form [(C∧N)₂Ir(L∧X)]⁺, in which C∧N is a cyclometalating ligand and L∧X is a bidentate neutral ancillary ligand, with at least one heterocyclic ligand other than pyridine. We contrast their properties to that of [(ppy)₂Ir(bpy)]⁺ and highlight recent exploits in materials applications.

This Microreview summarizes the optoelectronic properties of luminescent cationic iridium complexes bearing nontraditional ligand motifs with generalized structure [(C∧N)₂Ir(L∧X)]⁺, in which C∧N is a cyclometalating ligand and L∧X is a bidentate neutral ancillary ligand, with the goal of elucidating structure–property trends. Their use in applications such as photosensitizers for solar fuels and as luminophores in light-emitting electrochemical cells is also discussed.

A new Ru₂ azido complex, [Ru₂(chp)₄N₃] (4, chp = 2-chloro-6-hydroxypyridinate), was investigated under photolytic conditions to study the chemical reactivity of the corresponding Ru₂ nitride species, [Ru₂(chp)₄N] (6), towards intermolecular N atom transfer to triphenylphosphane (PPh₃). Photolysis of a dichloromethane solution of 4 at λ > 350 nm leads to a characteristic color change from purple to magenta. Upon acidic workup, triphenylphosphanamine chloride ([H₂NPPh₃]Cl) is produced and [Ru₂(chp)₄Cl] (5), the precursor to 4, is regenerated. The first stoichiometric cycle for intermolecular N atom transfer from a Ru₂ nitride is thus presented.

The new Ru₂ azido complex [Ru₂(chp)₄N₃] (chp = 2-chloro-6-hydroxypyridinate) reacts with PPh₃ under photolytic conditions to form [H₂NPPh₃]⁺Cl^– and [Ru₂(chp)₄Cl], from which the azide complex can be regenerated.

Addition of TEMPO (TEMPO = 2,2,6,6-tetramethylpiperidine-N-oxyl) to a toluene slurry of AlBr₃ results in rapid formation of AlBr₃(η¹-TEMPO) (1), which can be isolated in 65 % yield. In contrast, addition of TEMPO to a hexanes solution of BBr₃ results in formation of [TEMPO][BBr₄] (2) and (TEMPO)₂BBr (3), the products of TEMPO disproportionation. Complexes 1–3 have been fully characterized, including analysis by X-ray crystallography. The divergent reactivity is likely dictated by the Lewis acidity of the group 13 halide, and in the case of the stronger Lewis acid BBr₃, coordination of TEMPO to the boron center generates an adduct that is capable of oxidizing free TEMPO.

The outcome of the reaction between TEMPO and MBr₃ (M = B, Al) was found to depend on the Lewis acidity of the group 13 element. Addition of TEMPO to AlBr₃ results in formation of the 1:1 adduct, AlBr₃(η¹-TEMPO). In contrast, addition of TEMPO to BBr₃ results in TEMPO disproportionation and formation of [TEMPO][BBr₄] and (TEMPO)₂BBr.

A novel synthetic route based on [4+2] cycloaddition for dibromobenzobarrelene derivatives starting from in situ generated 3,5-dibromo-1,2-didehydrobenzene and mesitylene, 1,2,4,5-tetramethylbenzene, 1,2,3,5-tetramethylbenzene, pentamethylbenzene, 1,3-dimethoxybenzene, and 2,4,6-trimethylbromobenzene, respectively, was developed. Thus, six novel dibromobenzobarrelenes with diverse substitution patterns at the barrelene framework including chiral derivatives are reported. The benzobarrelene 6,8-dibromo-1,3,10-trimethyl-1,4-dihydro-1,4-ethenonaphthalene (1a) was functionalized at the annulated benzene ring to give three novel carboxylic acids and two novel phosphonic acid esters. Selected benzobarrelene complexes with Rh^ICl were tested for their catalytic activity in the 1,4-addition of phenylboronic acid towards cyclohex-2-enone. Turnover frequencies up to 3405 h^–1 were observed, which are among the highest reported so far for Rh–diene complexes in this type of C–C coupling reaction.

The synthesis by means of a [4+2] cycloaddition approach of six novel dibromobenzobarrelenes with diverse substitution patterns at the barrelene framework, including chiral derivatives, is reported as well as the functionalization of 6,8-dibromo-1,3,10-trimethyl-1,4-dihydro-1,4-ethenonaphthalene to give carboxylic acid and phosphonic acid ester derivatives.

Although phosphonous acid ligands have recently become of interest for use in transition metal complex catalysts for organic reactions such as alkene hydroformylations, the factors that affect the steric and electronic properties of these ligands have not been studied in detail. To gain insight into the electronic and steric properties of phosphonous acid ligands, we have prepared tungsten(0) pentacarbonyl complexes with chlorophosphite ligands derived from either 2,2′-biphenol or (±)-1,1′-bi-2-naphthol and have then hydrolyzed the coordinated ligands to generate tungsten(0) pentacarbonyl complexes with the corresponding phosphonous acid ligands. NMR measurements of the W–P coupling constants demonstrate that changing the biaryl groups from biphenyl to binaphthyl does not affect the electron-donor ability of the ligand, whereas changing the third substituent from chloro to oxo has a significant effect. Estimation of cone angles of the ligands from X-ray crystallographic data have shown that neither changing the biaryl group nor changing the third substituent have a significant effect on their cone angles. Further, these studies have identified important intra- and intermolecular interactions that favor certain ligand conformations. The data could be useful for the development of catalytic structure–activity relationships that could be used in the rational design of catalysts.

Steric and electronic properties of chlorophosphite ligands derived from 2,2′-biphenol or (±)-1,1′-bi-2-naphthol and their corresponding phosphonous acid ligands in tungsten(0) pentacarbonyl have been studied by using multinuclear NMR spectroscopy and X-ray crystallography. The identity of the biaryl group does not affect either the steric or the electronic properties of the ligands.

[Fe]-hydrogenase, one of three types of hydrogenases, activates molecular hydrogen. Here, using DFT computations, we examine the electronic elements governing the binding of small ligands to a recently synthesized [Fe]-hydrogenase biomimic. Computed reaction free energies indicate that anionic species, such as CN^– and H^–, and π acceptors, such as CO, bind favourably with the Fe centre. Ligands such as H₂O, CH₃CN, and H₂, however, do not bind iron. Protonation of an adjacent thiolate ligand on the mimic significantly increases the energies of ligand binding. Additional computational analysis reveals that the degree of electron donation from the ligand to the mimic correlates strongly with overall binding ability. The results give insights into the electronic elements of iron–small-molecule interaction in these model complexes.

The electronic effects that dictate the binding of small molecules to a [Fe]-hydrogenase mimic are examined by DFT computations. Analysis reveals that a ligand's ability to donate electron density to the Fe centre determines the overall reaction free energy.

The first two lanthanum selenide chlorides, LaSeCl and La₃Se₄Cl, both crystallize orthorhombically in space group Pnma (no. 62). They emerged from reactions of LaCl₃ with lanthanum and selenium in appropriate molar ratios at 800–900 °C. Single crystals of the yellow LaSeCl adopt the cotunnite-type structure of PbCl₂ with a = 760.63(5), b = 433.52(3) and c = 910.07(6) pm (Z = 4). The tricapped trigonal prisms [LaSe₅Cl₄]^11– share their triangular faces to form chains that run parallel to the [010] direction and are condensed through caps and common edges to give a complete crystal structure in accord with _∞³{LaSe_5/5Cl_4/4}. Dark-red La₃Se₄Cl exhibits the U₃S₅-type structure with a = 1271.98(5), b = 855.84(3) and c = 795.05(2) pm (Z = 4). The chloride anions are located at the Wyckoff position 8d together with selenium showing site occupation factors of 0.5 for both anion types. Bicapped trigonal prisms [LaSe₇Cl]^12– with (La2)³⁺ are connected through common faces and corners to form a three-dimensional framework suited to the embedding of chains of fused tricapped trigonal prisms [LaSe₅₊₁Cl₂]^11– with (La1)³⁺ running parallel to [010]. The absorption edge energy of approximately 1.75 eV indicates a wide band-gap semiconductor that is stable towards air, water and some aqueous bases at different concentrations.

The crystal structures of the first lanthanum selenide chlorides, LaSeCl and La₃Se₄Cl, are described in terms of condensed bi- and tricapped trigonal prisms [LaSe_nCl_m]^11/12– (n = 5, 5+1, 7; m = 1, 2, 4). A phase-pure sample of La₃Se₄Cl displays an optical band gap of 1.75 eV. Both show high stability towards air, water and inorganic bases, but decompose upon contact with acids.

Novel phosphors, Ca₂YF₄PO₄:Eu²⁺,Mn²⁺, have been prepared by high-temperature solid-state reactions. XRD and XPS techniques were used to investigate the purity and composition of the as-prepared samples. The Ca₂YF₄PO₄:Eu²⁺,Mn²⁺ phosphors exhibit broad excitation spectra ranging from 275–420 nm and the emission spectra show a broad blue emission band centered at 455 nm and a yellow emission band centered at 570 nm, which originate from the Eu²⁺ and Mn²⁺ ions, respectively. Energy transfer from the Eu²⁺ to Mn²⁺ ions in the Ca₂YF₄PO₄ host matrix was observed and studied by luminescence spectrosccopy as well as the lifetime of the Eu²⁺ ions. The emission color of the Ca₂YF₄PO₄:Eu²⁺,Mn²⁺ samples can be adjusted from blue to yellow under excitation by UV radiation of 375 nm by adjusting the Eu²⁺ and Mn²⁺ concentrations, and white-light emission with chromaticity coordinates (0.327, 0.312) was obtained with the Ca₂YF₄PO₄:0.015Eu²⁺,0.015Mn²⁺ sample. In addition, the temperature-dependent photoluminescence of the as-prepared phosphors has been investigated in detail. The results revealed that the Ca₂YF₄PO₄ host has good thermal stability. The stable structure of the host and tunable luminescence suggest that Ca₂YF₄PO₄:Eu²⁺,Mn²⁺ could be regarded as a good candidate for UV LED-based white-light emitting diodes.

The tunable luminescence and energy-transfer properties of Ca₂YF₄PO₄:Eu²⁺,Mn²⁺ phosphors with potential application in LEDs have been investigated.

1,10-Diaza-18-crown-6 and 4,4′-trimethylenedipiperidine were transformed into bis-dithiocarbamate ligands, which were then reacted in situ with different di- and triorganotin(IV) chlorides to generate dinuclear monomeric or macrocyclic products. The identity of the compounds was established by elemental analysis, multinuclear NMR spectroscopy (¹H, ¹³C, and ¹¹⁹Sn), IR spectroscopy, mass spectrometry, and for representative examples additionally by single-crystal X-ray diffraction analysis. In combination with DFT calculations, the structural characterization showed that diaryltin and dialkyltin fragments give macrocycles of different conformation owing to changes in the coordination stereochemistry (cis vs. trans isomers). The macrocycle cavities are suitable for the inclusion of guest molecules. At the supramolecular level, the Sn complex molecules are linked through intermolecular C–H···S and C–H···Cl interactions in the solid state.

Dinuclear monomeric and macrocyclic complexes derived from diorganotin dithiocarbamates are prepared by using ligands with azacrown and dipiperidine spacers. The macrocyclic structures have different conformations depending on the R₂Sn group, which also changes the size of the cavity suitable for guest inclusion. The structures show supramolecular arrays through C–H···S and C–H···Cl interactions.

9-Hydroxy-2-methyl-phenalenone (MHPO) was synthesized and modified with 3-(triethoxysilyl)propyl isocyanate (TEPIC) through a hydrogen atom addition reaction to achieve a new chemical linkage (named as MHPOSi). SBA-15 mesoporous silica organically functionalized with MHPOSi was synthesized. The MHPOSi was linked to tetraethoxysilane (TEOS) through a condensation process in the presence of Pluronic P123 surfactant as a template. New Ln³⁺ (Eu³⁺, Nd³⁺, Yb³⁺) organic–inorganic mesoporous hybrid materials were prepared, in which the Ln³⁺ complexes are covalently attached to SBA-15 and have 1,10-phenanthroline (phen) as a second ligand. The resultant mesoporous hybrids were characterized by FTIR spectroscopy, small-angle X-ray diffraction, N₂ adsorption–desorption measurements, thermal analysis, and UV/Vis spectroscopy. They all have high surface areas, uniform mesostructures, and good crystallinity. The photophysical properties of the functionalized mesoporous SBA-15 networks are discussed in detail and they still present excitation capability in the visible region despite the modification of the organic silane. Subsequently, they exhibit characteristic visible (Eu³⁺) and near-infrared (NIR) luminescence (Nd⁺ and Yb³⁺).

Ln³⁺ (Eu³⁺, Nd³⁺, Yb³⁺) organic–inorganic mesoporous hybrid materials are prepared. The hybrids contain lanthanide complexes covalently grafted to 2-methyl-9-hydroxyphenalenone (MHPO) functionalized ordered mesoporous SBA-15 and with 1,10-phenanthroline as a second ligand. The materials exhibit the characteristic visible (Eu³⁺) and near-infrared (NIR) luminescence (Nd⁺ and Yb³⁺) of lanthanides.

The reaction of H₂C(PCl₂)₂ with four equivalents of iPrMgCl produces H₂C(PiPr₂)₂, which was treated with tellurium in boiling toluene, or selenium in toluene at room temperature, to give the monochalcogenides EPiPr₂CH₂PiPr₂ (E = Te, 4a; E = Se, 4b) in high yields. X-ray structural determinations show that 4a and 4b exist as the CH₂ tautomers in the solid state with E–P–C–P dihedral angles of 56.1(2)° and 56.7(1)°, respectively. DFT calculations were carried out for the isolectronic series EPR₂CH₂PR₂ and EPR₂NHPR₂ (E = Se, Te; R = Me, iPr, tBu, Ph) and for their non-chalcogenated precursors in order to elucidate the factors that determine the preference for PH tautomers in some PNP-bridged systems. Compounds 4a and 4b were also characterized by multinuclear (¹H, ¹³C, ³¹P, ⁷⁷Se, ¹²⁵Te) NMR spectroscopy. In solution, 4a exhibits fluxional behavior, which has been investigated by variable-temperature and variable-concentration multinuclear NMR spectroscopy. The observed behavior is consistent with an intermolecular tellurium transfer with an activation energy of 21.9 ± 3.2 kJ mol^–1; consideration of selenium exchange in 4b indicates a much higher energetic barrier. DFT calculations provide insights into the pathway for the chalcogen exchange process in 4a (ΔE = 20.4 kJ mol^–1). The outcome of reactions of 4a with selenium and nBuLi reflects the lability of the P-Te functionality.

The monochalcogenides EPiPr₂CH₂PiPr₂ (E = Se, Te) exist as CH₂ tautomers in the solid state; the contrast in this finding with that of the preferential formation of PH tautomers by PNP-bridged analogues is addressed through DFT calculations. In solution, the PCP-bridged tellurium derivative undergoes rapid intermolecular tellurium exchange with an activation energy of 21.9 ± 3.2 kJ mol^–1.

To date, only a few nanosystems have been investigated as T₁ MRI-CT dual contrast agents. The T₁ MRI-CT dual functionality of a material depends on its longitudinal water-proton relaxivity (r₁) and X-ray absorption strength. We explored Gd(IO₃)₃·2H₂O nanomaterial because Gd is the most powerful element for T₁ MRI contrast agents, and both Gd and I absorb X-ray radiation; Gd absorbs X-ray radiation ca. 2.5 times more strongly than I. D-Glucuronic acid coated Gd(IO₃)₃·2H₂O nanomaterial showed a very large r₁ of 52.3 s^–1 mM^–1 (r₂/r₁ = 1.21), which could be ascribed to hydrated water molecules in the lattice. Its X-ray absorption intensity was also stronger than those of commercial molecular iodine CT contrast agents. This result clearly suggests that D-glucuronic acid coated Gd(IO₃)₃·2H₂O nanomaterial is a potential T₁ MRI-CT dual contrast agent.

D-Glucuronic acid coated Gd(IO₃)₃·2H₂O nanomaterial is synthesized in one-pot and its T₁ MRI-CT dual imaging properties are investigated. It has a very large r₁ and strong X-ray absorption, which are prerequisites for high-performance T₁ MRI-CT dual contrast agents.

The incorporation of europium polyoxometalates into silica nanoparticles can lead to a biocompatible nanomaterial with luminescent properties suitable for applications in biosensors, biological probes, and imaging. Keggin-type europium polyoxometalates Eu(PW₁₁)_x (x = 1 and 2) with different europium coordination environments were prepared by using simple methodologies and no expensive reactants. These luminescent compounds were then encapsulated into silica nanoparticles for the first time through the water-in-oil microemulsion methodology with a nonionic surfactant. The europium polyoxometalates and the nanoparticles were characterized by using several techniques [FTIR, FT-Raman, ³¹P magic angle spinning (MAS) NMR, and TEM/energy-dispersive X-ray spectroscopy (TEM-EDS), AFM, dynamic light scattering (DLS), and inductively coupled plasma MS (ICP-MS) analysis]. The stability of the material and the integrity of the europium compounds incorporated were also examined. Furthermore, the photoluminescence properties of the Eu(PW₁₁)_x@SiO₂ nanomaterials were evaluated and compared with those of the free europium polyoxometalates. The silica surface of the most stable nanoparticles was successfully functionalized with appropriate organosilanes to enable the covalent binding of oligonucleotides.

Europium polyoxometalates with distinct europium coordination are encapsulated in silica nanoparticles by a microemulsion methodology. Their surface is further functionalized with appropriate organic groups to originate biocompatible nanomaterials with suitable photoluminescent properties.

Nanocrystalline Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂ was prepared by a layered-template method and was tested as a high-capacity and high-power cathode for Li-ion batteries. Structural characterization demonstrates that the Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂ nanoparticles have a high crystallinity with a monoclinic (C/2m) structure. This material exhibits an initial discharge capacity of 277.4 mAh g^–1 and a high coulombic efficiency of 87.3 %, with a very small capacity fade of 0.046 % per cycle over 100 cycles. Such excellent electrochemical performance is likely to result from its monoclinic structure that enables a stable solid solution structure and reversible structural changes during cycling. Therefore, monoclinic Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂ may meet the high-capacity and high-rate requirements for an alternative cathode for a new generation of Li-ion batteries.

A layered-template method was used to synthesis the Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂ nanoparticles with a monoclinic structure. Due to the presence of the monoclinic structure, the cycling stability and rate capability of the Li[Li_0.2Mn_0.54Ni_0.13Co_0.13]O₂ electrode are excellent.

The treatment of [Ru(CO)₂Cl₂]_x with 4,4′,4″-tri-tert-butyl-2,2′:6′,6″-terpyridyl (tbtpy) in tetrahydrofuran at reflux afforded trans-[Ru(tbtpy)Cl₂(CO)] (1). The alkylation of complex 1 with excess Me₃SiCH₂MgCl afforded a mixture of trans-[Ru(tbtpy)(CH₂SiMe₃)₂(CO)] (2) and trans-[Ru(tbtpy)(CH₂SiMe₃)Cl(CO)] (3), whereas complex 3 could be obtained in good yield by the alkylation of complex 1 with 1 equiv. of Me₃SiCH₂MgCl. On the other hand, the alkylation of 1 with MeLi and PhCH₂MgBr afforded the monoalkyl complexes [Ru(tbtpy)(Me)Cl(CO)] (4) and [Ru(tbtpy)(CH₂Ph)Cl_0.5Br_0.5(CO)] (5), respectively. The crystal structure of complex 5 was determined. Complex 2 and the previously prepared mer-[Ru(dtbpy)(CH₂SiMe₃)₃(NO)] (dtbpy = 4,4′-di-tert-butyl-2,2′-bipyridyl) were immobilized on SBA-15 by treating the Ru complexes with SBA-15 in benzene at room temperature. ¹H NMR spectroscopy indicated that the reaction of complex 2 and [Ru(dtbpy)(CH₂SiMe₃)₃(NO)] with SBA-15 in C₆D₆ resulted in the formation of approximately 1 equiv. of SiMe₄, which suggests the grafted species are possibly (≡SiO)Ru(tbtpy)(CH₂SiMe₃)(CO) and (≡SiO)Ru(dtbpy)(CH₂SiMe₃)₂(NO), respectively. The Ru-grafted SBA-15 materials were characterized by IR, reflectance UV/Vis, and X-ray photoelectron spectroscopy as well as transmission electronic microscopy, and their catalytic performance in the oxidation of benzyl alcohol with tert-butyl hydroperoxide was examined.

The alkylation of [Ru(tbtpy)(CO)Cl₂] (tbtpy = 4,4′,4″-tri-tert-butyl-2,2′:6′,6″-terpyridyl) with Me₃SiCH₂MgCl afforded a mixture of trans-[Ru(tbtpy)(CH₂SiMe₃)₂(CO)] and trans-[Ru(tbtpy)(CH₂SiMe₃)Cl(CO)]. trans-[Ru(tbtpy)(CH₂SiMe₃)₂(CO)] and mer-[Ru(dtbpy)(CH₂SiMe₃)₃(NO)] were immobilized on SBA-15 by elimination of SiMe₄ and the grafted species showed catalytic behavior.

Reactivity studies of aluminoxane hydroxide and hydrogensulfide [{^MeLAl(EH)}₂(μ-O)] {^MeL = CH[CMe(NAr)]₂^– (Ar = 2,4,6-Me₃C₆H₂); E = O (1), S (2)} with Group 4 amides led to the molecular heterobimetallic aluminoxanes [(^MeLAlO)₂(μ-O){M(NR₂)₂}] [M = Ti, R = Me (3); M = Zr, R = Me (4), Et (5); M = Hf, R = Me (6), Et (7)] and aluminoxane sulfides [(^MeLAlS)₂(μ-O){M(NR₂)₂}] [M = Ti, R = Me (8), Et (9); M = Zr, R = Me (10), Et (11); M = Hf, R = Me (12), Et (13)], respectively. The structural analyses of these compounds reveal six-membered inorganic cores that exhibit Al–E–M (E = O, S; M = Ti, Zr, Hf) moieties. Compounds 10–13 exhibit strong O···M (M = Zr, Hf) transannular bonding, whereas 8 and 9 exhibit relatively short Ti–S bond lengths. DFT calculations performed on 8–13 at the B3LYP/LANL2DZ level of theory indicate that the titanium atoms in 8 and 9, despite having the lowest transannular bond index, have the highest total Wiberg bond indexes. This can be rationalized in terms of the high Ti–S bond indexes, which indicate an important degree of electron density delocalized from the sulfur atoms to the titanium atom.

A series of Group 4 heterobimetallic aluminoxanes and aluminoxane sulfides have been prepared. The aluminoxane sulfides exhibit unprecedented Al–S–M (M = Zr, Hf) moieties. The structural and electronic features of these compounds were investigated by DFT calculations.

The multinuclear silicon complexes [{H₂ClSi(μ-pz*)₂}₂SiH₂] (1) and [Cl₂Si(μ-pz^RR)₂SiCl₂] (2, R = Me; 3, R = Ph) were formed by the reaction of dichlorosilane (for 1) or hexachlorodisilane with 1-trimethylsilyl-3,5-dimethylpyrazole (for 1 and 2) and the 3,5-diphenyl analogue (for 3). The reaction of trichlorosilane with 3,5-dimethylpyrazole (Hpz*) in MeCN resulted in the formation of two MeCN insertion products of 2 (4, 5). From different samples of synthesis products of this work a preferred hydrolysis product was obtained: [{(μ-pz*)₂SiH}₃–μ³-O]⁺Cl^– (6). The structural and electronic features of the compounds synthesised in this work were analysed with single-crystal X-ray diffraction and ²⁹Si cross-polarisation (CP)/magic-angle spinning (MAS) NMR spectroscopy combined with quantum chemical computations to investigate their ²⁹Si chemical-shift anisotropy principal tensor components.

The reaction of trichlorosilane with 3,5-dimethylpyrazole (Hpz*) in acetonitrile afforded dinuclear silicon compounds. Their outstanding feature is the formal insertion of one or two molecules of MeCN into the former N–Si bond of a Sipz* moiety. These compounds were examined with single-crystal X-ray diffraction, ²⁹Si cross-polarisation (CP)/magic-angle spinning (MAS) NMR spectroscopy and quantum chemical calculations.

The guanidine proligands {2-[4-(tert-butyl)phenyl]-1,3-diisopropylguanidine} (1), [2-(4-methoxyphenyl)-1,3-diisopropylguanidine] (2) and [2-(4-bromophenyl)-1,3-diisopropylguanidine] (3) have been prepared by guanylation of anilines with diisopropylcarbodiimide, using [MgBz₂(thf)₂] as the catalyst at room temperature. These proligands react with the complex {[Nb(CH₂SiMe₃)₃(CH₃CN)]₂(μ-1,4-NC₆H₄N)} (4) to afford new guanidinate-supported dialkyl niobium dinuclear complexes [{Nb(CH₂SiMe₃)₂[(4-tBuC₆H₄)N=C(NiPr)(NHiPr)]}₂(μ-1,4-NC₆H₄N)] (5), [{Nb(CH₂SiMe₃)₂[(4-MeOC₆H₄)N=C(NiPr)(NHiPr)]}₂(μ-1,4-NC₆H₄N)] (6) and [{Nb(CH₂SiMe₃)₂[(4-BrC₆H₄)N=C(NiPr)(NHiPr)]}₂(μ-1,4-NC₆H₄N)] (7). Treatment of compounds 5–7 with 2 equiv. of 2,6-dimethylphenyl isocyanide gave the imido bis(iminoacyl) compounds [{Nb(Me₃SiCH₂C=Nxylyl)₂[(4-tBuC₆H₄)N=C(NiPr)(NHiPr)]}₂(μ-1,4-NC₆H₄N)] (8), [{Nb(Me₃SiCH₂C=Nxylyl)₂[(4-MeOC₆H₄)N=C(NiPr)(NHiPr)]}₂(μ-1,4-NC₆H₄N)] (9) and [{Nb(Me₃SiCH₂C=Nxylyl)₂[(4-BrC₆H₄)N=C(NiPr)(NHiPr)]}₂(μ-1,4-NC₆H₄N)] (10). The molecular structures of compound 2 and complex 9 have been determined.

Dinuclear alkyl diimidoniobium complexes reacted with catalytically obtained guanidines to yield guanidinate complexes. Double bis(iminoacyl) derivatives were obtained by a migratory insertion reaction of 2,6-dimethylphenyl isocyanide.

A (β-diketiminato)nickel(II) hydrazido(1–) complex [L^tBuNi(η²-N₂H₃)], {1, L^tBu = [HC(CtBuNC₆H₃{iPr}₂)₂]^–} has been obtained by treatment of [L^tBuNiBr] with hydrazine. In a reaction of 1 with two equivalents of the azo compound diisopropyl azodicarboxylic ester (adc–OiPr) the Ni(N₂H₃) entity acts as both a hydrogenating and a reducing agent: diisopropyl hydrazidodicarboxylate (hdc–OiPr) is formed, and more adc–OiPr is reduced by two electrons. The resulting (adc–OiPr)^2– is found as a ligand in the ultimate nickel product complex, the trinuclear nickel(II) compound [L^tBuNi(μ-adc–OiPr)Ni(μ-adc–OiPr)NiL^tBu] (2), in which two L^tBuNi⁺ units are linked by a [Ni^II(adc–OiPr)₂]^2– moiety. The hypothesis that L^tBuNi^I species are acting as intermediates was supported by the independent finding that 2 can also be obtained by reaction of [L^tBuNi(OEt₂)] with adc–OiPr.

A (β-diketiminato)nickel hydrazido(1–) complex has been synthesized that acts as a four-electron reductant towards a diazene: The corresponding hydrazine is formed, as well as a novel trinuclear complex with bridging hydrazido(2–) ligands, which can also be obtained through activation of the diazene at nickel(I) precursors.

Energy storage and conversion schemes based on environmentally benign chemical fuels will require the discovery of faster, cheaper, and more robust catalysts for the oxygen-evolution reaction (OER). Although the incorporation of pendant bases into molecular catalysts for hydrogen production and utilization has led to enhanced turnover frequencies, the analogous incorporation of pendant bases into molecular catalysts for water oxidation has received little attention. Herein, the syntheses, structures, and catalytic activities of new iron complexes with pendant bases are reported. Of these new complexes, [Fe(L¹)]²⁺ {L¹ = N,N′-dimethyl-N,N′-bis(pyridazin-3-ylmethyl)ethane-1,2-diamine} is the most active catalyst. Initial turnover frequencies of 141 and 24 h^–1 were measured by using ceric ammonium nitrate at pH 0.7 and sodium periodate at pH 4.7, respectively. These results suggest that the incorporation of pendant bases into molecular catalysts for water oxidation might be an effective strategy that can be considered in the development of new catalysts for the OER, but will require the careful balance of many factors.

The structural, electrochemical, and catalytic properties of a family of iron-containing homogeneous water oxidation catalysts with pendant heteroatoms are studied. Slightly faster O₂ evolution relative to a parent compound is observed when the solvent pH is matched to the pK_a of the pendant nitrogen base, which might be attributable to interactions with substrate water.

Reaction of [2-{(CH₂O)₂CH}C₆H₄]Li with SnCl₄ in a 4:1 molar ratio afforded [2-{(CH₂O)₂CH}C₆H₄]₄Sn (1), which was deprotected to give [2-(O=CH)C₆H₄]₄Sn (2). Homoleptic [2-(RN=CH)C₆H₄]₄Sn [R = Me₂NCH₂CH₂ (3), 2,4,6-Me₃C₆H₂ (4), PhCH₂ (5)] were obtained by condensation of 2 with the corresponding amine either in solution or by using a green, solvent-free procedure for (imino)arylmetal species. All compounds were characterised by multinuclear NMR spectroscopy and mass spectrometry, and their molecular structures were determined by single-crystal X-ray diffraction. In all cases, the C₄Sn core is distorted tetrahedral as a result of the combined effects of the intramolecular coordination of the heteroatoms from the organic ligands and the steric impediments imposed by the ligands. The overall coordination around tin was found to be different, that is, coordination numbers from six for 1 and 4, to seven for 3 and 5 and eight for 2. Compound 2 is the first example of a mononuclear tetraorganotin(IV) compound that contains an octacoordinated metal centre with a double helicate topology in the solid state. Multinuclear NMR spectroscopy studies in solutions of CDCl₃ are consistent with equivalent organic groups attached to a tetracoordinate tin atom.

Homoleptic tetraorganotin(IV) compounds with hexa-, hepta- and octacoordinated metal centres were prepared. A solvent- and catalyst-free green synthetic method was used to obtain three (imino)aryltin derivatives. A mononuclear, octacoordinated, double helical tetraorganotin(IV) compound is reported.

Direct metalation reactions of diphenylamine and carbazole by using an amido-bridged dinuclear Al₂ complex proceeded across two aluminum atoms while maintaining the dinuclear structure. In contrast, an aryloxido-bridged dinuclear aluminium complex was inert to the C–H metalation reaction. Such different reactivity of the alkylaluminum complexes with an [Al₂O₂] or [Al₂N₂] core was attributed to the space available for the secondary amine substrates to approach the Al–Me moiety: the flexibility provided by the bridging amido ligand forms an Al₂N₂ core with both a planar and butterfly shape, which creates enough space for the Al–Me moiety to activate the amines.

Direct metalation reactions of diphenylamine and carbazole were achieved by using amido-bridged dinuclear Al₂ complexes. By comparing the inertness of the aryloxido-bridged dinuclear aluminum complexes for the C–H metalation reaction, we found that the Al₂N₂ core created enough space for the secondary amine substrates to approach the Al–alkyl moiety due to the flexibility of the bridging amido ligand, which allows the Al₂N₂ core to form both a planar and butterfly shape.

Over the last 15 years or so, it has been shown that low-valent, electron-rich uranium(III) complexes exhibit a wide variety of reactivity towards small molecules. As a result, the field of uranium-mediated small-molecule activation chemistry has undergone significant development in recent years. The classical organometallic reactivity patterns of oxidative addition and reductive elimination that dominate the chemistry of transition-metal complexes are much less common for uranium. Owing to the invocation of the 5f orbitals for bonding and the highly polarising nature of the actinide centre, the prevalent reactivity observed for non-aqueous uranium compounds is that of migratory insertion, σ-bond metathesis and redox activity, and this can account for the often unexpected chemistry encountered with these species. This microreview focuses on the activation chemistry of trivalent uranium complexes towards the important small molecules dinitrogen (N₂), nitric oxide (NO), azide (N₃^–), carbon monoxide (CO) and carbon dioxide (CO₂).

Low-valent, electron-rich U^III complexes have the ability to access a wide range of novel reactivity patterns with small molecules. This microreview focuses on the activation chemistry of trivalent uranium complexes towards the industrially relevant small molecules N₂, NO, N₃^–, CO and CO₂, outlining the often unexpected chemistry observed for these reactive U^III centres.

Borylation of hafno- and zirconocene complexes [(η⁵-C₅H₂-1,2,4-Me₃)₂M]₂(μ₂,η²,η²-N₂), containing strongly activated dinitrogen ligands, with pinacolborane (HBPin) resulted in N–B and M–H bond formation. Treatment of the borylated products with carbon monoxide triggered N–N bond scission with concomitant N–C bond formation to produce μ-borylimido and μ-formamidido fragments. Conversely, addition of tBuNC resulted in insertion of the isocyanide ligand into the M–H bonds and furnished the corresponding η²-iminoacylhafnocene complexes.

Use of pinacolborane to borylate a hafnocene complex with a highly activated, side-on bound dinitrogen ligand resulted in N–B and M–H bond formation. Carbonylation of the functionalized hafnocene product triggers N–N cleavage to borylimido and formamidido ligands, thereby expanding the scope of CO-induced N₂ bond cleavage.

Aryl amido iridium complexes supported by a tridentate phosphanyl–carbene–phosphanyl pincer ligand [(PCP)Ir–N(H)Ar, Ar = C₆H₅, 1a; Ar = 2,6-iPr₂C₆H₃, 1b] react with acetonitrile to afford the dimeric complex 2, in which two (PCP)Ir fragments are bridged by a diiminato ligand derived from two molecules of CH₃CN. Metrical parameters obtained from X-ray structural determination of 2 confirm that the bridging ligand is a diiminato species rather than an enediamido moiety, which indicates that the reductive coupling is mediated by one electron per iridium center. Experiments suggest that the reaction proceeds by heterolytic cleavage of the Ir–N(H)Ar bond followed by one-electron reduction of the resulting Ir^I–NCCH₃ cation by the amido anion. The resulting anilino radical rapidly abstracts a hydrogen atom from the solvent. The reductive coupling of acetonitrile at a late transition metal center is unusual and in this instance occurs as a result of the highly σ-donating, electron-rich nature of the PCP ligand.

Electron-rich Ir^I aryl amido complexes undergo heterolytic bond cleavage and one-electron reduction to effect coupling of a coordinated acetonitrile ligand. The dimeric product features a bridging diiminato ligand. The ability to mediate this coupling with a late transition metal attests to the highly donating nature of the PCP pincer ligand environment.

A half-sandwich, coordinatively unsaturated N-heterocyclic carbene complex of iron with a metallacycle was found to cleave the Si–H bonds of hydrosilanes to give 16-electron iron–silyl complexes. The reactions of silyl complexes with H₂ led to the formation of dihydride complexes, in which hydride ligands weakly interact with the silicon atom. The molecular structures of these new complexes have been determined by means of X-ray crystallography.

A half-sandwich, 16-electron iron complex with a cyclometalated N-heterocyclic carbene ligand was found to activate the Si–H bonds of hydrosilanes, thus giving rise to coordinatively unsaturated iron–silyl complexes. The silyl complexes interact with H₂ to form 18-electron dihydride complexes.

Benzimidazolium salts N,N′-disubstituted with 9-alkylfluorenyl groups (3a–e, alkyl = methyl, ethyl, propyl, butyl, benzyl) have been synthesised in high yields in three steps from o-phenylenediamine. This amine was treated with fluorenone in the presence of TiCl₄ and tetramethylethylenediamine (TMEDA) to form N,N′-bis(9H-fluoren-9-ylidene)benzene-1,2-diamine (1) in 91 % yield. Diamines 2a–e were then obtained in yields superior or equal to 77 % by reacting diimine 1 with the appropriate organolithium reagent. In the final step, diamines 2a–e were treated with ethylorthoformate under acidic conditions to afford benzimidazolium salts 3a–e. These were readily converted into the PEPPSI palladium complexes 4a–e (PEPPSI = pyridine-enhanced precatalyst preparation stabilisation and initiation). NMR and X-ray diffraction studies revealed that the flat fluorenylidene moiety orientates the alkyl groups towards the metal centre and because of its restricted rotational freedom makes the ligand bulkiness time independent. Thus, the metal centre is permanently confined between the two alkyl groups, and thereby forms a monoligating clamp with the carbenic centre. The CH₂ groups close to the palladium ion give rise to anagostic C–H···Pd interactions. Catalytic tests revealed that the palladium complexes 4a–e are highly efficient in Suzuki–Miyaura cross-coupling reactions; their activity is equal or superior to the best PEPPSI catalysts reported to date.

N-Heterocyclic carbene ligands act as clamps with Pd centres to form highly active Suzuki–Miyaura cross-coupling catalysts. The remarkable performance displayed by these ligands relies on the presence of expanded 9-alkylfluorenyl substituents with a restricted rotational freedom, which results in a permanent, meridional confinement of the metal centre.

The phosphanylbipyridine ligands 6-(diphenylphosphanyl)-4,4′-dimethyl-2,2′-bipyridine (PPh₂-Me₂-bipy, a), 4,4′-di-tert-butyl-6-(diphenylphosphanyl)-2,2′-bipyridine (PPh₂-tBu₂-bipy, b), and 6-(diisopropylphosphanyl)-2,2′-bipyridine (PiPr₂bipy, c) and the corresponding dinuclear copper complexes [Cu₂(μ-PPh₂-Me₂-bipy)₂(NCCH₃)₂](PF₆)₂ (1), [Cu₂(μ-PPh₂-tBu₂-bipy)₂(NCCH₃)₂](PF₆)₂ (2), [Cu₂(μ-PiPr₂bipy)₂(μ-NCCH₃)](PF₆)₂ (3), and [Cu₂(μ-PiPr₂bipy)₂{μ-CNCH(CH₃)₂}](PF₆)₂ (4) were synthesized. The X-ray structures of 1–4 show that the complexes are dinuclear with the bidentate bipyridine coordinating to one copper atom and the phosphane moiety coordinating the other copper center. Complexes 3 and 4 possess short Cu–Cu distances with bridging acetonitrile and isocyanide ligands. The cyclic voltammograms of 1–4 were examined under N₂ and CO₂. Under N₂, 1–3 show four quasi-reversible 1e^– reductions, and under CO₂, they show current enhancement at the second reduction. In comparison, complex 4 shows four irreversible reductions under N₂ and no current enhancement under CO₂.

Three phosphanylbipyridine ligands that react with Cu^I to form dimeric complexes have been synthesized and structurally characterized. The Cu–Cu distance can be controlled by ligand substitution, and electrochemical studies of the dimers suggest that four sequential 1e^– reductions of the bipyridine ligands occur. Catalytic behavior is observed under CO₂.

The cover picture shows a model structure of the human copper chaperone Atox1 bound to cisplatin (magenta: Pt; green: Cl; blue: N; white: H; yellow: S) and poses an intriguing question: Is platinum exchanged between transporters as it happens for copper? This major question is still lacking an answer. Details are presented in the Microreview by F. Arnesano, M. Losacco, and G. Natile on p. 2701 ff. For more on the story behind the cover research, see the Cover Profile. In the background is “the near-touching hands”, a detail of the Creation of Adam by Michelangelo.

Cisplatin, or cis-diamminedichloridoplatinum(II) cis-[PtCl₂(NH₃)₂], is a platinum-based anticancer drug largely used for the treatment of various types of cancers, including ovarian and colorectal carcinomas, sarcomas, and lymphomas. Together with other platinum-based drugs, it triggers malignant cell death by binding to nuclear DNA, which appears to be the ultimate target. In addition to passive diffusion across the cell membrane, other transport mechanisms, including endocytosis and some active or facilitated transport, are currently proposed to play a pivotal role in the uptake of platinum-based drugs. In this microreview, we will give an updated view of the current literature regarding cisplatin transport and processing inside the cell, with special emphasis on the membrane copper transporter Ctr1 and the soluble copper chaperone Atox1.

Membrane transporters and soluble chaperones of copper ions mediate cellular uptake of and resistance to platinum-based drugs. In this microreview, the interactions of cisplatin with the methionine-rich motifs of the copper permease Ctr1 and with the cysteine motifs of the cytosolic copper chaperone Atox1 are described. Only in the latter case does the drug retain its ammine ligands essential for antitumor activity.

The simple metathesis reaction of the silver(I) weakly coordinating anion (WCA) salt Ag[Al(OR^F)₄] {R^F = C(CF₃)₃} with gold(I) chloride and ethene led to the formation of the second isolable tris(ethene)gold(I) complex, the last missing entry in the triad [M(C₂H₄)₃]⁺[Al(OR^F)₄]^– (M = Cu, Ag, Au). The Au atom is coordinated by three ethene ligands in a distorted trigonal-planar manner in a so-called spoke-wheel arrangement. The formation of the tris(ethene) complex instead of the more expected bis(ethene) complex was analyzed by theoretical investigations and by a Born–Fajans–Haber cycle for [Au(C₂H₄)₃]⁺[Al(OR^F)₄]^– as well as the only other known example [Au(C₂H₄)₃]⁺[SbF₆]^–.

The missing puzzle piece: [Au(η²-C₂H₄)₃]⁺[Al{OC(CF₃)₃}₄]^– in a spoke-wheel structure is the missing puzzle piece in the series of homoleptic univalent group 11 ethene complexes with the weakly coordinating anion [Al{OC(CF₃)₃}₄]^–. Herein, we describe the synthesis, characterization, and theoretical investigations of the second isolable, homoleptic η²-bound tris(ethene)gold(I) complex.

The enzyme thioredoxin reductase (TrxR) is attracting much interest as a potential target for cancer therapy. The presence of a selenium atom in the catalytic site makes it sensitive to inhibition by electrophilic molecules, including the Au^I complex auranofin [2,3,4,6-tetra-O-acetyl-1-thio-β-D-glucopyranosato-S-(triethylphosphane)gold]. The reactions between auranofin and models of thiol and selenol nucleophiles present in TrxR (PhSH and PhSeH) have been investigated in chloroform and methanol by means of ¹H, ³¹P, and ⁷⁷Se NMR spectroscopy. In chloroform, auranofin undergoes ligand substitution of the tetraacetylthioglucose moiety by a PhS or PhSe group. The reaction is reversible in both cases, but it is characterized by widely different equilibrium constants (ca. 1 for S and at least 10³ for Se). In polar solvents, such as methanol, the reaction is more complex, and the phosphane moiety also undergoes ligand exchange. Some features have been clarified through the investigation of Et₃PAuCl. The elementary processes involved have been characterized by DFT calculations.

The reactivity of the drug auranofin, a gold(I) complex with anticancer properties, towards selenols and thiols is investigated by multinuclear NMR spectroscopy and DFT calculations. Useful insights that are relevant to the mechanism of inhibition of thioredoxin reductase are obtained.

The catalytic activity of [Cp*₂M₂O₅] (M = Mo, W; Cp* = pentamethylcyclopentadienyl) for the homogeneous epoxidation of a solution of cyclooctene in MeCN/toluene follows the order Mo >> W when using tert-butyl hydroperoxide (TBHP)/decane as oxidant, in contrast to the inverse order (W >> Mo) when using aqueous H₂O₂ as oxidant. The catalytic activity for the Mo system strongly depends on the solvent used to deliver the oxidant (TBHP/decane >> TBHP/H₂O). The low activity of the W system is also decreased when using TBHP/water in place of TBHP/decane. For both metals, H₂O₂/H₂O is a better oxidant than TBHP/H₂O. However, whereas the Mo-based catalyst is much more active for the TBHP/decane epoxidation in spite of the lower TBHP oxidizing power (TBHP/decane > H₂O₂/H₂O > TBHP/H₂O), the W-based system is much more active for the H₂O₂/H₂O epoxidation in spite of the negative effect of water (H₂O₂/H₂O > TBHP/decane > TBHP/H₂O). The kinetic profile of the TBHP/decane epoxidation process is affected by product inhibition. Initial rate measurements show that the rate law is first order with respect to substrate and has saturation behavior with respect to the oxidant.

[Cp*₂M₂O₅]-catalyzed (Cp* = pentamethylcyclopentadienyl) cyclooctene epoxidation is more efficient for M = Mo when the oxidant is tert-butyl hydroperoxide (TBHP)/decane, whereas it is more efficient for M = W when using H₂O₂/H₂O. Water has a negative effect with both oxidants, and H₂O₂ is a better oxidant than TBHP for both metals, but the relative effects are system-specific.

Two crystalline modifications of a cobalt(II) benzoate complex containing substituted pyrazole ligands are investigated. The polymorphs are characterized by different intermolecular bonding as well as by different metal-atom environments. A thorough analysis of the chemical bonding patterns by means of Bader's “Atoms in Molecules” theory reveals the significant role of N–H···O hydrogen bonds in charge transfer within the molecule and in stabilization of unfavorable [4+1] cobalt polyhedra. Specifically, an estimation of the interaction energies according to an Espinosa correlation scheme shows the significant contribution of H bonds to the stabilization energy of the molecular conformations.

A thorough analysis of the chemical bonding patterns in two polymorphs of a cobalt(II) benzoate complex with substituted pyrazole ligands by using Bader's “Atoms in Molecules” theory reveals the crucial role of N–H···O hydrogen bonds in the stabilization of unfavorable [4+1] cobalt polyhedron.

With the ultimate goal of rationally studying the factor able to affect the stability of the photoinduced high-spin state, we selected three iron(II) 1D coordination polymers with the general formula [FeL_eq(L_ax)]·solvent with L_eq = {3,3′-[1,2-phenylenebis(iminomethylidyne)]bis(2,4-pentanedionato)(2-)-N,N′,O²,O²′}; L_ax = 4,4′-bipyridine (bipy, 1), 1,2-bis(4-pyridyl)ethane (bpea, 2), and 1,3-bis(4-pyridyl)propane (bppa, 3); and solvent MeOH. This series of complexes comprises 1D chains with structures varying from linear (for bipy) over step-like (for bpea) to zigzag (for bppa). For all the materials, the thermal spin-crossover properties were measured and the stabilities of the photoinduced high-spin states were probed through determination of the T(LIESST) values associated with the light-induced excited spin-state trapping (LIESST) effect. For some of the investigated samples, the existence of steps in the relaxation of the photoinduced high-spin state was discussed.

Spin crossover and photomagnetic properties of iron(II) coordination polymers: In a series of three 1D complexes, the thermal spin-crossover properties were measured and the stabilities of the photoinduced high-spin states were probed through determination of the T(LIESST) values associated with the light-induced excited spin-state trapping (LIESST) effect.

The mass spectra of benzo-2,1,3-chalcogenadiazoles, acquired from the equilibrium conditions of the UV-laser desorption/ionization plume, contain isotopic patterns that are characteristic of protonated and ionized dimers. Dispersion-corrected DFT modeling shows that the most stable structures of these dimers feature the supramolecular four-membered Te₂N₂ ring, which is pervasive in the crystal structures of these compounds. These observations provide the first evidence of the persistence of Te–N supramolecular association in the gas phase.

Ionized supramolecular aggregates held together by chalcogen–nitrogen secondary bonding interactions (SBIs) are detected by mass spectrometry.

The synthesis and spectroscopic characterisation of a series of homoleptic complexes of the tridentate pyridine-2,6-di(5-tetrazolate) ligand (pydtz^2–) with Co^II, Ni^II, Cu^II and Zn^II are reported. Single-crystal XRD data reveals the formation of octahedrally configured complexes [M(pydtz)₂]^2– for M = Zn or [M(Hpydtz)(pydtz)]^– for M = Co or Ni, whereas for M = Cu a polymeric structure [Cu(pydtz)(EtOH)]_n crystallised. In the latter, alternate short and long Cu···Cu distances were found. Magnetic measurements and electron paramagnetic resonance (EPR) spectroscopy reveal noncoupled S = 1/2 Cu^II ions for [Cu(pydtz)(EtOH)]_n, S = 1/2 low-spin configuration for the Co^II complex and an S = 1 ground state for the Ni^II derivative. At T < 16 K the latter shows anomalies that resemble those of single-ion molecular magnets. The ligand strength of pydtz^2– is markedly higher than that of the bioisosteric pyridine-2,6-dicarboxylate (pydic^2–) ligand and is very similar to that of the well-established 2,2′:6′,2″-terpyridine (terpy) ligand as revealed by the ligand field bands of the Co, Ni and Cu complexes and the magnetism of the Co and Ni derivatives. Solution electrochemical investigations suggest that essentially ligand-centred reduction at rather negative potentials and metal-centred oxidation processes occur.

The new compounds K[Co(Hpydtz)(pydtz)], K[Ni(Hpydtz)(pydtz)], [Cu(pydtz)(EtOH)]_n and Na₂[Zn(pydtz)₂] [pydtz = pyridine-2,6-di(5-tetrazolate)] are characterised by single-crystal XRD, electron paramagnetic resonance (EPR) spectroscopy, magnetic measurements and UV/Vis absorption spectroscopy to assess the strength of the tridentate pydtz^2– ligand.

The manganese(III) complex with a Schiff-base salen-type ligand (1,5-bis{[(1E)-(2-hydroxyphenyl)methylene]amino}-1H-imidazole-4-carbonitrile) has been encapsulated in the nanopores of a Y zeolite by using two different methodologies, the flexible ligand and in situ complex preparation methods. Cyclic voltammetry studies revealed that the neat complex undergoes reversible oxidation in dmf, which has been attributed to the Mn^II/III redox couple, whereas the two heterogeneous catalysts show different electrochemical behaviour in aqueous medium. The encapsulated and non-encapsulated homogeneous Mn^IIIsalen complexes were screened as catalysts for olefin oxidation by using tBuOOH as the oxygen source in different solvents. Under the optimized conditions, the catalysts exhibited moderate activity. Both heterogeneous catalysts catalysed the oxidation of cyclohexene with tBuOOH, primarily to give the allylic oxidation products. These catalysts were found to be reusable after the catalytic cycle, but with some loss of activity. A DFT study confirmed the distortion of the complex in the zeolite cage, the main difference being observed for the bonded chloride.

Two methods for the encapsulation of a Mn^IIIsalen complex in NaY zeolite lead to different modes of coordination at the metal. Cyclic voltammetry of the neat and heterogeneous complexes shows different electrochemical behaviour. The heterogeneous catalysts lead to similar or higher alkene conversion than the homogeneous catalyst. DFT confirmed distortion of the complex in a confined space.

The reaction of LSitBu [L = PhC(NtBu)₂] (1) with 4,4′-bis(dimethylamino)thiobenzophenone resulted in the [1+2]-cycloaddition product silathiacyclopropane 3, bearing a three-membered SiCS ring. The reaction of LSiC(SiMe₃)₃ (2) with 3,5-di-tert-butyl-o-benzoquinone leads to the [1+4]-cycloaddition product 4. In 3 the silicon atom is five- and in 4 it is four-coordinate. Compounds 3 and 4 were characterized by spectroscopic and spectrometric techniques. The molecular structures of 1, 3, and 4 were unequivocally established by single-crystal X-ray structure analysis.

The reaction of LSitBu [L = PhC(NtBu)₂] (1) with 4,4′-bis(dimethylamino)thiobenzophenone resulted in the [1+2]-cycloaddition product silathiacyclopropane 3, bearing a three-membered SiCS ring. The reaction of LSiC(SiMe₃)₃ (2) with 3,5-di-tert-butyl-o-benzoquinone leads to the [1+4]-cycloaddition product 4.

The N-heterocyclic carbene NHC/thione ligand precursors 1-[(3-R-2-thioxo-2H-imidazol-1-yl)methyl]-3-R-2H-imidazol-2-ium hexafluorophosphate, [HCS^R]PF₆ (R = methyl, benzyl) have been prepared and used in the synthesis of the complexes [Rh(CS^R)(cod)][PF₆] (R = methyl, benzyl; cod = 1,5-cyclooctadiene). The coordination and structural features of the novel ditopic NHC/thione ligands have been explored.

The mixed donor N-heterocyclic carbene/sulfur ligands CS^R (R = Me, Bn) coordinate to rhodium centres to provide complexes of the type [Rh(CS^R)(cod)]PF₆. The complexes were prepared by using the corresponding imidazolium salt precursors [HCS^R]PF₆. The complexes have been fully characterized by spectroscopic and analytical methods in addition to X-ray crystallography.

Bis(dimethylsulfido)decaborane, 6,9-(Me₂S)₂-arachno-B₁₀H₁₂, reacts smoothly with ferrocenyl alkynes FcC≡CR [1a–h; Fc = ferrocenyl, R = H (1a), CH₃ (1b), Ph (1c), 4-MeO₂CC₆H₄ (1d), Fc (1e), C≡CFc (1f), C(O)CH₃ (1g), and CO₂CH₂CH₃ (1h)] to afford the corresponding 1-ferrocenyl-1,2-dicarba-closo-dodecaboranes 2a–h in good yields. Ester 2h was further reduced to the respective hydroxymethyl derivative, 1-Fc-2-CH₂OH-1,2-closo-C₂B₁₀H₁₀ (3). The reaction of 6,9-(Me₂S)₂-B₁₀H₁₂ with FcC≡CSiMe₃ proceeded in a different manner to produce (among other products) an SMe₂ adduct of an opened decaborane substituted with a 2-ferrocenyl-2-(trimethylsilyl)ethen-1-yl group (4). This compound probably results through hydroboration of the starting alkyne and migration of the SiMe₃ group. All prepared compounds were characterized by spectroscopic methods (¹H, ¹³C, and ¹¹B NMR spectroscopy, IR spectroscopy, and mass spectrometry), and their molecular structures were determined by single-crystal X-ray diffraction analysis. In addition, the compounds were studied by cyclic and differential pulse voltammetry on a platinum disc electrode to reveal simple ferrocenyl-centered oxidations for the singly ferrocenylated carboranes and two consecutive oxidation waves for compounds 2e and 2f, which possess two ferrocenyl substituents.

6,9-(Me₂S)₂-arachno-B₁₀H₁₂ reacts smoothly with ferrocenyl alkynes bearing simple and functional substituents at the triple bond to afford the respective 1-ferrocenyl-1,2-dicarba-closo-dodecaboranes in good yields. The compounds were structurally characterized by spectroscopic methods, X-ray crystallography, and voltammetric techniques.

Silylboranes are important reagents in a variety of catalytic silylation and silaboration reactions. While transition-metal-catalyzed reactions are well established, organo-/Lewis base-catalyzed reactions of silylboranes have only recently emerged. For both catalytic processes the reactivity of silylboranes toward Lewis bases is of relevance. While for organo-catalyzed reactions Lewis base activation of the silylborane has been proposed, transition-metal- and especially copper-catalyzed reactions also frequently require the presence of Lewis basic alkali metal alkoxides. In the present study we explore the reaction of K(18-crown-6) tert-butoxide and the NHC 1,3-diisopropyl-4,5-dimethyl-imidazol-2-ylidene as exemplary Lewis bases with the two silylboranes pinB-SiMe₂Ph and pinB-SiPh₃ (pin = OCMe₂CMe₂O). The reaction with K(18-crown-6) tert-butoxide results in activation of the boron–silicon bond. The isolated product of this activation is either the potassium silyl complex [K(18-crown-6)SiPh₃] or [K(18-crown-6)(thf)₂][pinB(SiMe₂Ph)₂], the formal Lewis acid/base adduct of [K(18-crown-6)SiMe₂Ph] with pinB-SiMe₂Ph. Both complexes react essentially as sources of nucleophilic silyl moieties in reactions with exemplary electrophiles. In contrast, usage of the carbene leads to the formation of isolable Lewis acid/base adducts of the type (NHC)pinB-SiR₃, which do not react as sources of nucleophilic silyl moieties. The identification and characterization of these species appears of relevance for the mechanistic understanding and further development of Lewis base/organo- as well as transition-metal-catalyzed silyl transfer reactions.

The reaction of a Lewis base with a silylborane is central to a series of Lewis base-mediated reactions of silylboranes. For [K(18-C-6)OtBu] and an NHC the reaction products were isolated and characterized. Either the activation of a B–Si bond or the formation of Lewis acid/base adducts is observed. The reactivity of the reaction products toward selected electrophiles is studied.

Heterobimetallic rare earth–alkali metal binaphtholates (REMBs) are exquisite catalysts for asymmetric synthesis (Shibasaki catalysts). All solid-state structures reported so far correspond to the general formula M₃RE[(S)-binolate]₃ (RE/M/B = 1:3:3 stoichiometry). We have synthesized and characterized crystallographically new complexes of this category, namely Li₃RE[(S)-binolate]₃·xTHF [RE = Sc (2), Sm (3)] and Li₃Nd[(S)-binolate]₃·6THF·LiCl (4). The latter is the first reported adduct between a REMB and LiCl. We have also crystallized a rare type of REMB of 1:2:2.5 stoichiometry: Li₄Sm₂[(S)-binolate]₅·6THF·2H₂O (5). Such a complex has only one precedent in the literature. The use of (S)-3,3′-dimesityl-1,1′-binaphthyl-2,2′-diol (6) as ligand precursor allowed us to obtain the first X-ray structures of unprecedented REMBs of 1:1:1 and 1:1:2 stoichiometries: {[(S)-6]RECl₂(THF)₂}[Li(THF)₂] [RE = Y (7), Sm (8)] and LiY[(S)-6]₂·2THF (9).

Heterobimetallic rare earth–alkali metal binaphtholates (REMBs) are exquisite catalysts for asymmetric synthesis. No REMBs with fewer than three binaphtholates have yet been characterized in the solid state. We report the first X-ray structure analyses of REMBs with only two, and even one, chiral ligands.

We report the design, synthesis, and assembly of functionalized carbon nanotubes (f-CNTs) in the absence of other templates by using a polysiloxane quaternary ammonium salt. Specifically, the perpendicular organic coating has a depth of ca. 3.2 nm and its hydrophobic nature provides the hydrophobic interactions (driving force) between near-neighbor CNTs. Once a complete coverage (ca. 100 %) of CNTs is achieved, the upper-layer nanotubes can spontaneously and readily interact with the sublayer tubes to assemble into oriented nanostructures with a tube distance of 26 nm along the tube axis. Therefore, the spontaneous assembly of f-CNTs in aqueous solution becomes possible without the help of other templates. Additionally, further investigations suggest that it is easier to obtain arrayed nanostructures with straight f-CNTs with 100 % coverage than with curved ones. Our strategy seems very attractive because the aligned CNT array can be achieved through simple control of the chemical functionalization of the nanotubes. This offers us a valuable insight into the bottom-up design of f-CNTs, one-dimensional nanostructures, and building blocks for supramolecular chemistry and nanotechnology.

Surface-functionalized carbon nanotubes (CNTs) with 100 % organic coverage exhibit parallel-aligned arrays with a tube distance of 26 nm in the absence of other templates. The alignment depends on the nature of the hydrophobic interaction between near-neighbor tubes. The depth of the perpendicular coating of the polysiloxane quaternary ammonium compound on the CNT surface is ca. 3.2 nm (inset).

Centimeter-sized single crystals of Ba₂LaFeNb₄O₁₅ were grown from a high-temperature solution by using LiBO₂ flux and a sealed platinum assembly. The obtained single crystals display the same physical properties as their ceramic counterparts. A frequency-dependent dielectric permittivity maximum was found (T_m = 100 K at 5 kHz), which indicates relaxor behavior. Magnetic susceptibility measurements revealed purely paramagnetic behavior between 10 and 350 K. X-ray diffraction measurements of Ba₂LaFeNb₄O₁₅ single crystals revealed an incommensurate structure at room temperature with a bidimensional modulation characterized by vectors q₁ = (α, α, 1/2) and q₂ = (α, –α, 1/2) with α = 0.295(1). This crystal growth method offers a promising elaboration route to centimeter-sized crystals of niobate-based compounds, which may not be grown from the pure liquid phase, especially those with a tetragonal tungsten bronze (TTB) structure.

Centimeter-sized Ba₂LaFeNb₄O₁₅ (BLFNO) crystals are obtained by a flux method. A frequency-dependent dielectric permittivity maximum is found (T_m = 100 K at 5 kHz), which indicates relaxor behavior. Single-crystal XRD analysis reveals an incommensurate structure at room temperature with a bidimensional modulation characterized by vectors q₁ = (α, α, 1/2) and q₂ = (α, –α, 1/2) with α = 0.295(1).