A DNA conjugate of the bis-1, 10-phenanthroline ligand Clip-phen was prepared and combined with a complementary, fluorescent reporter labeled DNA strand. In the resulting ds-DNA, the fluorescent reporter signals both the binding of Cu²⁺ ions to the Clip-phen moiety and the reduction to Cu⁺ by a change in fluorescence intensity. In preliminary single molecule fluorescence investigations, these processes appear to be observable on the level of individual molecules by single molecule fluorescence spectroscopy, but further validation and optimisation of the system is needed.

The electron density of a molecular scale system is probably the most information-rich observable in natural science, and experimental electron density determination based on X-ray diffraction is a strong field of modern crystallography. Most studies concern small molecule organic or metal-organic crystals, and indeed the experimental method and the subsequent data modeling and analysis have become a very versatile tool for such systems. However, inorganic materials in the form of high-symmetry dense solids, often with extended structures and containing heavy atoms, represent one of the most serious challenges to the X-ray electron density technique. For inorganic materials the scattering from the valence electrons is minute compared with the core electron scattering, and systematic errors such as extinction and absorption can be severe. In some sense studies of inorganic materials can be used as a benchmark for the current level of electron density analysis using X-ray diffraction. Here we discuss the special challenges that face X-ray electron density studies of inorganic materials. We discuss the special experimental requirements – basically the ideal X-ray electron density experiment shines stable, intense, high energy, monochromatic X-rays on minute single crystals at the lowest possible temperature, and the diffracted intensities are recorded on detectors with low background noise and large dynamic range. We also address the specific problems encountered when modeling very diffuse valence electrons in heavy atoms. Furthermore, for light atom materials topological analysis is often used as an analysis tool to extract information e.g. about chemical bonding, but for inorganic materials many of the commonly used descriptors are less informative, and other approaches are called for.

A new complex based on chlorendic acid (HET), [Cd₈(HET)₈(DMF)₄(H₂O)₁₂]·8DMF (1) was synthesized by liquid evaporate method from the mixture of HET and Cd(NO₃)₂·4H₂O. Single crystal X-ray analysis reveals that the structure of complex 1 features a one-dimensional (1D) wave chain that is further assembled into three-dimensional (3D) framework directed by supramolecular interactions, including hydrogen bond, Cl···Cl halogen bond, and so on. To the best of our knowledge, this is the first metal-organic coordination polymer based on chlorendic acid (HET). The luminescent property and thermal stability of complex 1 were also discussed.

This work focuses on the cationic antimicrobial peptide (CAP) DP18L with its known propensity to target and selectively kill cancer cells. DP18L was derivatised to dap-DP18L where dap is 2,3-diaminopropionic acid. Dap facilitated binding to Pt^II via an (N,N') bidentate ligand to afford the first reported Pt-CAP complex, cis-[Pt(dap-DP18L)Cl₂)]. The syntheses of the peptides and the Pt-peptide complex were carried out using solid phase chemistry. It was envisioned that the presence of the peptide in the complex would confer enhanced selectivity of the novel complex for neoplastic cells in addition to increasing the cellular uptake of the complex relative to cisplatin.

The cationic zinc complex [L¹Zn][Al(OC(CF₃)₃)₄] (1) (L¹ = {[(2,4,6-Me₃–C₆H₂)NC(Me)]₂CH}) bearing a weakly coordinating aluminate anion was obtained from reaction of L¹ZnCl with Li[Al(OC(CF₃)₃)₄]. In addition, base-stabilized zinc cations [L^1/2Zn(base)₂][X] (2–5) (L² = {[(2,6-iPr₂–C₆H₃)NC(Me)]₂CH}; X = [Al(OC(CF₃)₃)₄], [B(C₆F₅)₄]) containing weakly coordinating anions and different Lewis bases (dimethylaminopyridine (dmap), tert-butylpyridine (tBuPy)) were synthesized and structurally characterized. Moreover, the solid-state structures of L¹ZnMe (6) and the neutral base-stabilized complexes tBuPy-Zn(Cl)L¹ (7) and base-Zn(Me)L² (base = dmap 8, tBuPy 9) are reported and compared with those of 2–5. Preliminary studies showed that 1 is catalytically activity in lactide polymerization at 160 °C.

Reactions of 2-benzimidazole propionic acid (1) with [Sn(nBu)₃]₂O and SnPh₃OH gave mononuclear organometallic tin esters 2 and 3, respectively, where 1 is coordinated to the tin atom through the carboxylate group. Further reactions of 2 with DMSO and 3 with methanol, ethanol, pyridine, DMSO, THF and water afforded the corresponding tin compounds coordinated by the base 4–10, respectively. X-ray diffraction analyses of 5, 6 and 10 were obtained. The solid-state structures showed that the ligand 1 is bound through both oxygen atoms of the carboxylic group with the Lewis base anti to it. Reaction of 1 with di-n-butyltin oxide produced a tetranuclear distannoxane (11) by the association of four Sn(nBu)₂ groups, two oxygen atoms and four ligands. Four of the oxygen atoms are tricoordinate. The tin atoms are hexacoordinate with distorted octahedral geometries. The macromolecule has in total seven fused rings. Five of them are four membered rings arranged in a ladder-type arrangement and the other two are six membered rings. The aliphatic chains and the benzimidazole groups are perpendicularly oriented to the polycyclic arrangement giving a sandwich with polar bonds in the middle and covered by the aliphatic and aromatic groups. In all compounds the ligands showed a chiral helicoidal preferred conformation.

An addition reaction of dinuclear [(η⁶-C₆Me₆)Ru(η^3,1-exo-syn-CH₂CHCHCHO)]₂(BF₄)₂ (1) with different Lewis bases in acetone results in the formation of mononuclear [(η⁶-C₆Me₆)Ru(η³-exo-syn-CH₂CHCHCHO)(L)](BF₄) (L = PMe₃, 2; PPh₃, 3; PHPh₂, 4; Ph₂PEtPy, 6; CO, 7) and dinuclear [{(η⁶-C₆Me₆)Ru(η³-exo-syn-CH₂CHCHCHO)}₂(μ₂-dppe)](BF₄)₂ (5). The addition of Ph₂PCH₂CH₂PPh₂ to the dinuclear product 1 affords 5 which show a bridging phosphine between two ruthenium centers. A comparative study of the new cationic arene derivatives and the corresponding isoelectronic Cp*Ru(heteropentadienyl) is established. All compounds were characterized by IR spectroscopy, high resolution mass spectrometry, NMR spectroscopy and the crystal structures of 2 and 3 are also described.

The electronic structure of the intermetallic compound MgZn₂, a prototypical Laves phase, was investigated by first-principles calculations based on Kohn-Sham density-functional theory. A variety of six exchange-correlation energy density functionals, from local density approximation to hybrid functionals, was used to fully optimize the crystal structure. Cell parameters and mass density calculated with the density functional parameterization by Perdew, Burke, and Ernzerhof (PBE) were found closest to their corresponding experimental values. The revised version of the functional, PBEsol, recommended for solid state applications, gave inferior results. The electronic structure was analysed in terms of band structure, density of states and electron density.

The novel coordination compound [Cu^I₁₂(C₁₆H₁₆N₄)₆]·8DMAc, (2), (DMAc = N,N-dimethylacetamide) was prepared in solvothermal or microwave assisted reaction. It contains four metallamacrocyclic trinuclear copper(I) pyrazolate coordination units, which occupy four (opposite) faces of an imaginary metallosupramolecular octahedron. Six (4,4′-(1,2-phenylene)bis(3,5-dimethylpyrazol-1-ide) ligands (L₁^2–) are placed at the corners of the octahedron. Crystals of the free ligand H₂L₁ [1,2-bis(3,5-dimethyl-1H-pyrazol-4-yl)benzene, (1)], and [Cu^I₁₂(C₁₆H₁₆N₄)₆]·8DMAc (2), were characterized by single-crystal X-ray structure analyses. Lingand 1 crystallizes in the monoclinic crystal system, with: a = 9.0118(9), b = 14.0075(11), c = 11.7484(11) Å, β = 104.945(5)°, V = 1432.9(2) ų, space group P2₁/c (no. 14). Compound 2 crystallizes in the tetragonal system, with: a = b = 19.506(5), c = 42.888(5) Å, V = 16318(6) ų, space group I4₁/amd (no. 141). Compound 2 represents a porous structure, where each metallosupramolecular octahedron encloses a solvent-filled cavity of 889 ų (accounting for 6 DMAc molecules, 21.8 % of the cell volume). The incomplete crystal packing arrangement of adjacent [Cu^I₁₂(C₁₆H₁₆N₄)₆] moieties in addition leads to solvent-filled interstitial voids accounting to 8.1 % of the cell volume. Removing solvent molecules in vacuo is accompanied by reversible structural changes, leading to a partial loss of porosity, as revealed by Ar-BET sorption analysis. Compounds 1 and 2 were further characterized by elemental and thermogravimetric analysis, X-ray powder diffraction, FTIR-, UV/Vis- and fluorescence spectroscopy. Preliminary results on the activation of molecular oxygen by compound 2 are presented.

Stability constants of the ternary Cu(Arm)(H;PMEC)⁺ and Cu(Arm)(PMEC) complexes {PMEC^2– = dianion of 1-[2-(phosphonomethoxy)ethyl]cytosine, Arm = 2, 2′-bipyridine (Bpy) or 1, 10-phenanthroline (Phen)} were measured by potentiometric pH titrations (aq. sol.; 25 °C; I = 0.1 M, NaNO₃) and compared with those of Cu(Arm)(H;PMEA)⁺ and Cu(Arm)(PMEA) {PMEA^2– = dianion of 9-[2-(phosphonomethoxy)ethyl]adenine}, and related species. The basicity of the terminal phosphonate group is similar in PMEC^2– and PMEA^2–. Stability-constant comparisons reveal, that in the monoprotonated ternary Cu(Arm)(H;PMEC)⁺ complexes H⁺ is at the phosphonate group, that the ether oxygen atom of the –CH₂–O–CH₂–P(O)^–₂(OH) residue participates, next to the P(O)^–₂(OH) group, in Cu(Arm)²⁺ coordination, and that π–π stacking between the aromatic rings of Cu(Arm)²⁺ and the pyrimidine moiety is important. The Cu(Arm)(PMEC) complexes are considerably more stable than the corresponding Cu(Arm)(R–PO₃) species, where R–PO^2–₃ is a phosph(on)ate with a group R unable to interact intramolecularly. The stability enhancements are mainly attributed to intramolecular stacks and, to a smaller extent, to the formation of five-membered chelates involving the ether oxygen atom of the –CH₂–O–CH₂–P(O)^2–₃ residue of PMEC^2–. Analysis of the intramolecular equilibria reveals that ca. 10 % of the isomeric ternary complexes exist with Cu(Arm)²⁺ solely coordinated to the phosphonate group, ca. 25 % as a five-membered chelate involving the ether oxygen, and ca. 65 % with an intramolecular π–π stack between the pyrimidine moiety of PMEC^2– and the rings of Bpy or Phen. For a given Cu(Arm)²⁺ the stacking intensity increases from PMEC^2– to PMEA^2–. It seems feasible that the reduced stacking intensity of PMEC^2–, together with a different hydrogen bonding pattern, leads to a different orientation of the cytosine residue (compared to the adenine moiety) in the active site of the nucleic acid polymerases, thus resulting in a reduced antiviral activity of PMEC compared to PMEA.

Abstract. Based on a mononuclear precursor [Mn(Hstp)₂(4,4′-Hbpy)₂] (1), a hetero-metallic complex, [Mn₂Ni(stp)₂(4,4′-bpy)(H₂O)₄] (2) [stp = 2-sulfoterephthalate, 4,4′-bpy = 4,4′-bpyridine] was synthesized by solvothermal reaction. Single-crystal X-ray diffraction analysis reveals that the Mn^II ion of the precursor 1 is hexacoordinate by four oxygen atoms from two Hstp^2– anions and two nitrogen atoms from two protonated 4,4′-Hbpy, and hydrogen bonding plays a significant role in constructing 3D supramolecular structure. While complex 2 features a self-weaving framework from 1D straight chains and 2D wavy networks with double helical chains. Magnetic behavior of complex 2 was analyzed in connection with its crystal structure, which exhibits the weak antiferromagnetic interactions between the Mn^II and Ni^II ions.

A new ternary potassium cobalt stannide, K₁₃CoSn_17–x (x = 0.1), was obtained by reacting the mixture of the corresponding pure elements at high temperature, and structurally characterized by single-crystal X-ray diffraction study. K₁₃CoSn_17–x (x = 0.1) crystallizes in the orthorhombic space group Pbca (No. 61) with a = 26.2799(7) Å, b = 24.1541(6) Å, c = 29.8839(6) Å, V = 18969.3(8) ų, and Z = 16. Its structure contains isolated [CoSn₉] monocapped square antiprism and [Sn₄] tetrahedron in the ratio 1:2, forming a hierarchical variant of Laves phase MgZn₂. The structural relation between the title compound with MgZn₂ as well as other binary stannides is also discussed.

The reaction of the complex [{Ir(μ-Cl)(ptpy)₂}₂] (1) with oxamide in methanol in the presence of sodium methylate as the base was investigated. During the reaction the new complex [Ir₂(μ₂-oxamidato-N,N′,O,O′)(ptpy)₄] (2), ptpy = 2-(p-tolyl)pyridinato was obtained. The molecular structure of compound 2 was determined by an X-ray diffraction study. 2 crystallized from dichloromethane/methanol as a dihydrate in the orthorhombic space group Pbcm. This new compound displays intense green phosphorescence, with φ_PL = 60 %, stemming from the lowest triplet state of the ³MLCT/LC character.

The reactivity studies of stable silylenes with organo isothiocyanates are so far not reported. In this manuscript we describe for the first time the reaction of the stable silylene LSiNPh₂ (1) [L = PhC(NtBu)₂] with PhNCS to yield the silathione LSi(S)NPh₂ (2), with elimination of PhNC. The reaction of PhC≡CPh with LSiNPh₂ resulted in the [1+2]-cycloaddition product silacyclopropene 3. Treatment of 1 with 3,5-di-tert-butyl-o-benzoquinone yielded the [1+4]-cycloaddition product 4. Compounds 2, 3, and 4 were characterized by elemental analysis, multinuclear NMR spectroscopy, and EI-MS spectrometry. The molecular structures of compounds 2, 3, and 4 were established unequivocally by single-crystal X-ray structural analysis.

Hexaamminecobalt(III), an octahedral, inert metal ion complex, has lately gained increasing attention of structural biologists and bioinorganic chemists due to its use in structure determination of nucleic acids. This complex mimics outer-sphere binding events of the physiologically relevant magnesium(II)hexaaqua ion; hexaamminecobalt(III) often finds usage either in NMR spectroscopy, where cross-peaks between the complex ammines and the nucleic acid protons near the binding site are observed, in X-ray spectroscopy as heavy metal derivative for phasing, or in other techniques. In this review, we discuss the basic hexaamminecobalt(III) binding modes and give an overview on the most recent findings on [Co(NH₃)₆]Cl₃–nucleic acid complexes. The various techniques that are applied in combination with this complex are mentioned and briefly summarized. Special attention is given to the application of [Co(NH₃)₆]Cl₃ in nuclear magnetic resonance spectroscopy of nucleic acids, where it is used to reveal potential outer-sphere magnesium binding sites.

5-(8-Carboxy-1-naphthyl)-10,15,20-tritolyl porphyrin (H₃CNTTP) and its iron(III) complexes, [Fe(CNTTP)]₂ and [Fe(CNTTP)(N-MeIm)₂], were synthesized and characterized. X-ray crystallography revealed that the carboxylate group is “hanging” over the porphyrin plane. The rigid framework makes the distance between the carboxylate oxygen and iron in the same porphyrin too long to form a coordination bond. On the other hand, the carboxylate group is not bulky enough to block the axial binding site. In the presence of OH^–, the carboxylate oxygen is coordinated to iron in the symmetry-related unit, which led to the dimeric structure, [Fe(CNTTP)]₂. In the presence of excess N-methylimidazole, a six-coordinate species, [Fe(CNTTP)(N-MeIm)₂], was obtained. In such a structure, CH···O interactions between the carboxylate group and imidazole probably play an important role to determine the orientation of imidazole plane. Two imidazole planes have relative parallel orientation. For [Fe(CNTTP)(N-MeIm)₂], ¹H NMR shows pyrrole protons at the region –10 to –25 ppm. EPR shows rhombic spectrum. Those suggest [Fe(CNTTP)(N-MeIm)₂] is a type II low-spin iron(III) porphyrinate.

A new coordination polymer, [Cu(3,4-pybz)₂]_n (1) [3,4-Hpybz = 3-pyridin-4-yl-benzoic acid], was synthesized by hydrothermal reaction of CuCl₂·2H₂O and 3,4-Hpybz, and characterized by elemental analysis, IR spectroscopy, PXRD, and single-crystal X-ray diffraction. The structure determination reveals that 1 exhibits a 2D twofold interpenetrated 4-connected (4,4) network topology, these 2D layers are further enlarged to form the final 3D supramolecular edifice via aromatic π–π stacking interactions. In addition, the magnetic behavior and thermogravimetric analysis of 1 were also studied.

An organometallic salt composed of a new cationic p-cymene ruthenium chloro complex containing a chelating benzaldehyde semicarbazone ligand and of the known anionic p-cymene ruthenium trichloro complex, [(η⁶-p-cymene)Ru(bzsc)Cl]⁺[(η⁶-p-cymene)RuCl₃]^– (1) (bzsc = benzaldehyde semicarbazone) was synthesized and further characterized by IR, ¹H NMR, and UV/Vis spectroscopy HR-ESI mass spectrometry, and elemental analysis. The single-crystal structure of 1 was also determined. The in vitro anticancer activities of the complex was evaluated against three human cancer cell lines (SGC-7901, BEL-7404 and CNE-1), and the IC₅₀ values were 20.7, 71.1 and 42.6 μM, respectively.

1,1-Diamino-2,2-dinitroethylene (FOX-7) has received increasing attention since it was industrialized in the late 1990s. It has lower sensitivity and comparable performance to RDX. This paper presents ballistic properties of FOX-7, its mono and dinitro derivatives and their epoxide derivatives computationally. The structures were optimized at the B3LYP/6-31G(d, p) level and the bond lengths were calculated. The calculated data for FOX-7 are compatible with the literature one. We have investigated the bond dissociation energies of the molecules. Mulliken electro negativities (χ_M) and chemical hardness (η) were reviewed using Frontier Molecular Orbitals at HF/6-31G(d, p)//B3LYP/6-31G(d, p) theoretical level. The detonation performance analyses were done using empirical Kamlet-Jacobs equations. Additionally, power index values were calculated. All the compounds considered in the present article are powerful candidates for high energy materials.

Simple mixing or shaking of alkaline earth hydroxides with ammonium fluoride results in nanocrystalline phase pure metal fluorides MF₂ (M: Ca, Sr, Ba). The formation of the alkaline earth fluorides was investigated by varying the reaction conditions. Evidence was found that just the contact between the starting materials is sufficient for the reaction to take place. X-ray diffraction, elemental analysis, ¹⁹F MAS NMR spectroscopy, and measurements of DC conductivities were used to characterize the fluorides regarding properties like crystal structure, crystallite sizes, local fluorine coordination, and fluorine ion conductivity. The ¹⁹F MAS NMR spectra of the phase pure fluorides prepared showed several signals, which were assigned to defects, impurities, or geometric distortions. The fluorides prepared by mixing or shaking revealed fluorine ion conductivities several orders of magnitude higher than observed for the respective microcrystalline alkaline earth fluorides. Therefore, the synthesis routine presented in this study may open a path to a very quick and simple synthesis of nanocrystalline fast fluorine ion conductors.

Mono-oxo-bis-dithioveratrol-molybdate was synthesized, structurally characterized, and investigated with respect to its oxo-transfer activity. The latter was compared with the activity of the analogous tungsten complex. The title complex is a structural model for molybdopterin bearing arsenite oxidase and both complexes catalyze oxo-transfer reactions successfully to 100 % conversion. With the dithioveratrol ligand the oxidation of triphenylphosphine proved to be faster for the tungsten complex, which is untypical. The solid-state structure of the molybdenum complex exhibits an unexpected and very unusual polymeric structural motif consisting of the complex anion mono-oxo-bis-dithioveratrol-molybdate, sodium cations, and methanol. Infinite double-decker strands are formed with sodium bridges between the ether functions of two ligands in one strand and the Mo=O moiety of the second strand.

Thermodynamic parameters are presented here illustrating the effects caused by the two anticancer active metal complexes cisplatin and oxaliplatin after introduction into four closely related RNA and DNA duplexes. The duplexes used are blunt end, fully complementary 15-mer duplexes with a centrally located either GG- or GNG (here: N = T or U) binding site. For all duplexes, a common trend of reduced melting temperature was observed after platination. Analysis of the thermodynamic parameters for the duplex dissociation reactions showed good correlation between variations in melting temperatures (T_m) and ground state enthalpies (ΔH) in both DNA- and RNA duplexes. The melting temperatures of the native duplexes were found to be determined by their chemical nature, i.e. with observed T_m -values of ca. 50 °C for DNA and ca. 61 °C for RNA (C_T = 2 μM and C_Na+ = 129 mM, pH 6.3). Of the two types of nucleic acids, RNA is the one that exhibits the most pronounced sensitivity towards introduction of the platinum complexes, and with oxaliplatin as the more influential metalation reagent. Of note is that the thermal destabilization caused by oxaliplatin interacting with a centrally located GUG-sequence results in a duplex stability below native DNA.

Reactions of complexes [{M(μ-Cl)(ptpy)₂}₂] (M = Rh, 1; M = Ir, 2; ptpy = 2-(p-tolyl)pyridinato) with glycinamide hydrochloride in methanol/dichloromethane in the presence of sodium methylate as the base were investigated. Thus, the new complexes [M(glycinamidato-N,N′)(ptpy)₂] (M = Rh, 3; M = Ir, 4) were obtained. The new chiral compounds were characterized by 2D¹H and ¹³C NMR spectroscopic studies. The molecular structure of compound 4 was confirmed by X-ray diffraction. Complex 4 crystallized from dichloromethane/methanol/isohexane in the centrosymmetric space group C2/c with the two enantiomers in the unit cell. The emission spectrum of 4 exhibited the new compound as a green emitting complex.

A new barium ytterbium indium selenide, Ba₂YbInSe₅, was obtained by conventional high temperature solid state reaction. The compound crystallizes in the noncentrosymmetric space group Cmc2₁ of the orthorhombic system. The structure contains infinite one-dimensional anionic chains [YbInSe₅]^4–, which are built from YbSe₆ octahedra and InSe₄ tetrahedra and separated by Ba²⁺ cation. The magnetic measurement indicates that the compound is paramagnetic. In addition, the calculated bandgap is 0.29 eV.

The synthesis of two new low-valent dicarbonyl complexes of tungsten [W(CO)₂(SPh-oz)₂] (3b) and molybdenum [Mo(CO)₂(SPh-oz)₂] (4b) coordinated by a bidentate thiolate-oxazoline ligand SPh-oz is reported. The thereby created coordination via two anionic sulfur atoms can be seen as biologically inspired as it reflects the first coordination sphere of the pterin cofactor found in molybdenum and tungsten enzymes. The in-situ preparation of the lithium salt Li(SPh-oz) (1) was described previously in literature, but analytical data was not available. A similar situation was found for the published syntheses of the low-valent metal precursors [W(CO)₃(PPh₃)₂Cl₂] (2a), [W₂(CO)₇Br₄] (3a) and [Mo(CO)₄Br₂] where experimental procedures were unreliable and experimental data was inadequate or missing.To the best of our knowledge this is the first report of a full characterization of the literature known compounds Li(SPh-oz) (1), [W(CO)₃(PPh₃)₂Cl₂] (2a) and [W₂(CO)₇Br₄] (3a). Furthermore the novel tetranuclear Mo-precursor [Mo₄(CO)₇Br₁₀] (4a) was synthesized. The symmetric and asymmetric IR stretching frequencies of its seven carbonyl ligands were calculated using DFT and related to the experimental values. The molecular structures of the novel precursor compounds [W(CO)₂(PPh₃)₂Cl₂] (2a'), [PPh₃Cl]₂[WCl₆] (2b), [Mo₄(CO)₇Br₁₀] (4a), the two complexes with the SPh-oz ligand [W(CO)₂(SPh-oz)₂] (3b), [Mo(CO)₂(SPh-oz)₂] (4b) and a new modification of [W₂(CO)₇Br₄] (3a) were determined by single-crystal X-ray diffraction analysis.

A new tyrosinase model based on the mononuclear copper(I) complex CuL_bzm1 is synthesized and characterized. The ligand L_bzm1 of this system contains a combination of an imine and a benzimidazole function which renders the system more biomimetic in comparison to the recently published L_py1 model of tyrosinase (M. Rolff, J. Schottenheim, G. Peters, F. Tuczek, Angew. Chem. Int. Ed. 2010, 122, 6583). As shown by UV/Vis and NMR spectroscopy, the CuL_bzm1 complex catalytically mediates the conversion of the monophenol DTBP-H to the o-quinone DTBQ with a TON of 31. This reaction was also conducted in a stoichiometric fashion to get information about the involved intermediates and identify possible reasons for the observed increase in catalytic performance with respect to the L_py1 system. DFT calculations were performed for the μ-catecholato dicopper intermediate, compound 4^bzm. These calculations indicate a mixed valent Cu^I-semiquinone-Cu^II structure, indicating that one-electron transfer from the monohydroxylated substrate to the copper centers has already occurred at this stage.

The copper(I) and copper(II) complexes [Cu((TMG_et)₂N_etSEt)]BPh₄ (1·BPh₄) and [Cu((TMG_et)₂N_etSEt)Cl]Cl (2·Cl) with (TMG_et)₂N_etSEt = ((Me₂N)₂C=NCH₂CH₂)₂NCH₂CH₂SEt were synthesized and structurally characterized as a model system for the copper enzyme PHM, a monooxygenase involved in the activation of peptide hormones and neuropeptides. The reaction of the copper(I) complex 1·BPh₄ with dioxygen has been studied using low temperature stopped-flow methods. However, in contrast to PHM no formation of an end-on copper superoxido complex could be observed. Instead an equilibrium between a bis-μ-oxo and a side-on peroxide complex was detected spectroscopically.

The synthesis and characterization of two new Cu^II complexes with pyrazole ligands formulated as [Cu₃(μ-Pz)₃(μ₃-OH)(Pz)₂Cl₂][Cu₃(μ-Pz)₃(μ₃-OH)(Pz)₂Cl₂(DMF)]·2DMF (1) and [Cu₃(μ-DMPz)₃(DMF)₄(OAc)(μ₃-OH)(H₂O)]⁺[Cu₃(μ-DMPz)₃(DMF)(NCS)₃(μ₃-OH)]^– (2) (where Pz = 1H-pyrazole and DMPz = 3, 5-dimethyl-1H-pyrazole) are reported. The compounds were prepared by the reaction of zero valent copper metal and Pz or DMPz in the dimethylformamide solution in the presence of the different additional components (chloride or thiocyanate ligands). The crystal structures of both compounds were determined by single-crystal X-ray diffraction analysis. Both compounds 1 and 2 are hexanuclear clusters comprising from neutral (1) or charged (2) trinuclear triangular fragments Cu₃(μ₃-OH)(μ-Pz)₃ of inverse azametallacrowns aza9-MC_Cu^II-3 topology. Nevertheless, they exhibit relevant differences in their molecular structures. The magnetic measurement shows the isotropic antiferromagnetic interaction in 2 with J₁ = –140 cm^–1 for the cationic and J₂ = –109 cm^–1 (–2JS_i·S_j model) for the anionic part of the molecule above 100 K and significant influence of antisymmetric exchange at lower temperatures.

A novel [(1, 3-benzoxazol-2-yl)-(5-chloro-1, 3-benzoxazol-2-yl)]amine (L) (1) compound was synthesized. The molecule has a nitrogen atom between 1, 3-benzoxazol-2-yl and 5-chloro-1, 3-benzoxazol-2-yl groups. For compound 1 there are twelve possible conformers and tautomers. Ab initio calculations were performed in order to investigate the more stable structures. Three crystals of compound 1 were obtained in different media, where compound 1 is associated by hydrogen bonding to H₂O (1a), THF (1b), or o-aminophenol (1c). Their X-ray diffraction analyses are reported. The synthesis and structural study of the coordination compounds [Co(L)₂(H₂O)] (3) and [Ni(L)₂(H₂O)₂] (4) are discussed.

The N₄ ligand 1-{6-[1, 1-bis(pyridin-2-yl)ethyl]pyridin-2-yl}-N,N-dimethylmethanamine (L) is presented. It has been used to obtain the copper(I) complex [CuL(MeCN)]PF₆ and the iron(II) complex [Fe(CN)₂L]. Aerobic oxidation of the copper(I) complex is unspecific at room temperature. Anaerobic oxidation in solution, which is very sluggish, occurs with formation of the copper(II) complex [Cu^IIFL]PF₆, suggesting concomitant hydrolysis of hexafluorophosphate initiated by traces of water. The iron(II) complex adsorbed at a TiO₂ surface is an efficient photosensitiser of the support. Photoelectrochemical photocurrent switching (PEPS), which can be initiated by changing the electrochemical potential and photon energy, is very pronounced. The construction of a simple photoelectrochemical NOR logic gate has been demonstrated.

Three new alkali metal acetylides CsNaC₂, CsKC₂, and CsRbC₂ have been synthesized and characterized by means of synchrotron powder diffraction studies. As a new synthetic approach, the binary alkali metal acetylides were reacted at relatively low temperatures (200 °C). DSC measurements were performed to prove the general usability of this reaction. CsKC₂ and CsRbC₂ crystallize in a variant of the anti-PbCl₂-type structure (Pnma, Z = 4), while for CsNaC₂ a new structure type (Pbcm, Z = 4) is found.

Structural response of crystals to an applied external perturbation is important as a key for understanding microscopic origin of physical properties. Experimental investigation of structural response is a great challenge for modern structure analysis. We demonstrate how advanced X-ray diffraction techniques facilitate probing tiny (10^–4 Å) distortions of bond lengths under a permanent electric field. We also discuss details of the experimental procedure essential for reaching such precision. We ask whether the experiment can be used to evaluate chemical bonds in crystals by their sensitivity to an external electric field and discuss if the bond deformations can be predicted using the bond-valence model or the Bader's theory of atoms in molecules and crystals. Finally, we describe the new time-resolved studies of a structural response to a dynamical switch of applied electric field. These results give access to the time-lining of piezoelectric effect on a microsecond time scale.

As the reactivity of organolithium compounds is strongly connected with the structure of the involved species, the structural knowledge is a prerequisite for the understanding of reaction mechanisms. Using the example of methyllithium, we address particularly the issues of stabilizing non-classical interactions in organolithium aggregates and the relations between disaggregation and polarity, using a combination of X-ray structure analysis and quantum-chemical methods. The structure analyses of a series of MeLi adducts, among them the diethyl ether adduct (MeLi·Et₂O)₄, exhibit varying arrangements of the α-hydrogen atoms relative to lithium. α-Hydrogen orientations differ even when changing the stereochemistry of the ligand in dimeric adducts. Computations confirm only weak stabilizing effects of agostic Li–H interactions, which compete with other aspects of the spatial situation in the formed aggregates. NPA and QTAIM analyses on different aggregates (e.g. monomer, dimer, tetramer, extended crystal environment) with different co-ligands reveal a complicated relation between the degree of aggregation and Li–C bond polarity but a more clearcut dependence on the lithium coordination number.

The sodium complex [{Ph₂P(O)NH(2, 6-Me₂C₆H₃)}Na{Ph₂P(O)N(2, 6-Me₂C₆H₃)}]₂ (2) with the ligand N-(2, 6-dimethylphenyl)diphenylphosphinic amide was synthesized involving the reaction of the neutral ligand [Ph₂P(O)NH(2, 6-Me₂C₆H₃)] (1) and sodium bis(trimethylsilyl)amide in toluene at 60 °C. The calcium complex [{Ph₂P(O)NH(2, 6-Me₂C₆H₃)CaI(THF)₃}I] (3) was obtained by the reaction between the neutral ligand 1 and anhydrous calcium diiodide in THF at ambient temperature. The solid-state structures of the complexes were established by single-crystal X-ray diffraction analysis. In the solid-state structure of 2, the sodium ion is coordinated through the chelation of oxygen atom attached to the phosphorus atom. Two different P–N and P–O bond lengths are observed, which indicates that one ligand moiety is anionic, whereas the second one is neutral. In the solid-state structure of 3, the calcium atom adopts distorted octahedral arrangement through the ligation of two phosphinic amide ligands, three THF molecules, and one iodide ion.

. A new manganese(II) coordination polymer, [Mn₃(atpt)₃(2, 2′-bpy)₂]_n (1) (H₂atpt = 2-aminoterephthalic acid; 2, 2′-bpy = 2, 2′-bipyridine), was synthesized by hydrothermal reaction of Mn(OAc)₂, H₂atpt, and 2, 2′-bpy. It was structurally characterized by element analysis, IR spectroscopy, powder XRD, and magnetic measurements. X-ray single-crystal analysis was carried out for 1, which crystallizes in the orthorhombic system, space group Pbca. The single X-ray diffraction studies reveal that 1 consists of infinite layers of alternating trinuclear manganese subunits and H₂atpt ligands. There are two types of different coordination modes of H₂atpt in 1. Magnetic susceptibility data for 1 were measured in the range 3–300 K. There are antiferromagnetic interactions between manganese ions of 1.

As a conceptual study, In⁰ nanoparticles are obtained by NaBH₄-driven reduction of InCl₃ · 4H₂O and transferred from a polar/hydrophilic diethylene glycol phase to a non-polar hydrophobic dodecane phase for purification and stabilization. Finally, the In⁰ nanoparticles are oxidized via a Laux-like reaction with nitrobenzene to In₂O₃ nanoparticles. The challenge of the reaction is to perform the final oxidation to In₂O₃ under mild conditions with the colloidal stability, particle size and particle size distribution of the initial In⁰ nanoparticles retained. To this concern, the mean diameter of the initial In⁰ nanoparticles changed from 11(1) to 14(2) nm of the oxidized In₂O₃ nanoparticles. Such multi-step reaction, including reduction, nucleation, phase transfer, exchange of surface capping and oxidation are of increasing importance for nanoparticles. Especially, Laux-type conditions with nitrobenzene as a molecular oxidizing agent of nanoparticles have not been used till now. Particle size, size distribution and chemical composition of the In⁰ and In₂O₃ nanoparticles are analyzed by DLS, SEM, XRD, FT-IR and HRTEM.

The single crystals of Ba₂Cd(B₃O₆)₂ were grown by the spontaneous crystallization method for the first time. They crystallize in the centrosymmetric trigonal space group R with a = 7.143(3) Å, c = 17.405(16) Å, and Z = 3. The structure is characterized by isolated B₃O₆ units, and the Ba²⁺ and Cd²⁺ cations connect with B₃O₆ rings to form three dimensional structure. The TG/DSC and XRD results reveal that Ba₂Cd(B₃O₆)₂ melts congruently. First-principles electronic structure calculation performed with the density functional theory (DFT) method shows that the calculated bandgaps are 4.66 eV, which is in good agreement with the UV/Vis/NIR experimental value 4.59 eV. The calculation shows that the Ba₂Cd(B₃O₆)₂ crystal has a large birefringence (Δn = 0.0875–0.0569 from 270 nm to 2600 nm), which demonstrates that Ba₂Cd(B₃O₆)₂ is a potential birefringence crystal.

The first organic amine templated europium sulfate chloride [C₆N₄H₂₂]_0.5Cl[Eu(SO₄)₂·H₂O] (1) was synthesized solvothermally and structurally characterized by single-crystal X-ray diffraction, IR spectroscopy, TGA, and ICP. Crystal analyses of compound 1 shows a novel inorganic layer constructed from [–Eu–O–S–O–]_n chains. The adjacent chains are connected by sharing the bridging SO₄^2– groups to generate eight-membered rings. The very strong luminescence in the red light region indicates compound 1 is an excellent candidate for red fluorescent materials.

Three new coordination polymers, namely, [CuL_0.5] (1), [Co(H₂L)(H₂O)₂][H₂O] (2), and [(CdCl)_0.5Cd_0.25(H₂L)_0.5] (3) were synthesized under hydrothermal conditions from the corresponding Cu^II, Co^II, and Cd^II salts with a multidentate ligand of 2, 2′,2′′,2′′′-[2, 3, 5, 6-tetramethyl-1, 4-phenylenebis(methylenenitrilo)]tetraacetic acid (H₄L). The complexes were characterized by single-crystal X-ray diffraction, IR, thermogravimetric, and elemental analyses. Complex 1 crystallizes in the orthorhombic space group Pbca and has a three-dimensional architecture with infinite two-dimensional networks linked together by weak Cu–O interactions. Complex 2 crystallizes in the monoclinic space group P2(1) and displays a 2D network. Complex 3 crystallizes in the tetragonal space group P4(2)/ncm and exhibits an infinite 3D architecture that has unusual [Cd₂(CO₂)₄Cl₂] dinuclear paddle-wheel units and [Cd(CO₂)₄] dodecahedron units. The results showed that the coordination arrangement of central metal atoms and the conformation and coordination mode of organic ligands play an important role in determining the structure of the complexes. The luminescence property of complex 3 was studied in the solid state at room temperature.

Two new metallaphosphacarboranes have been synthesised from [7, 8-nido-CPB₉H₁₁]^– by deprotonation followed by treatment with a metal fragment. Starting with [HNMe₃][7, 8-nido-CPB₉H₁₁] deprotonation and reaction with a source of {(indenyl)Co}²⁺ affords the η-bonded cobaltaphosphacarborane 3-(η-C₉H₇)-3, 1, 2-closo-CoCPB₉H₁₀ (1) the first “half-sandwich“ 3, 1, 2-metallaphosphacarborane. The indenyl ligand conformation in 1 (cisoid between the indenyl bridgehead carbon atoms and cage heteroatoms, with the cage carbon atom lying below the indenyl C–C bond) reveals that the structural trans effect in a phosphacarborane ligand is weakest for carbon and therefore varies in the order B > P > C. Starting with [HNC₅H₁₁][7, 8-nido-CPB₉H₁₁] deprotonation and reaction with half an equivalent of [Ru(p-cymene)Cl₂]₂ affords the σ-bonded ruthenaphosphacarborane 8-{Ru(p-cymene)Cl(C₅H₁₁N)}-7, 8-nido-CPB₉H₁₁ (2), the first example of a molecule with a phosphacarborane σ-bonded to a metal to be crystallographically characterised.

We here review the principles and applications of solid-state NMR spectroscopy of quadrupolar nuclei, with a special emphasis on structural studies of inorganic solids. Most NMR-observable nuclei have spin I > 1/2, and possess a quadrupole moment. The resulting quadrupolar interaction severely broadens the resonances, but also encapsulates valuable information about the symmetry of the electronic surroundings of the observed nucleus. The effect of the quadrupolar interaction, as well as that of the chemical shift and dipolar interaction, on solid-state NMR spectra is examined in this article. To regain good resolution, specifically designed NMR techniques exist to remove the quadrupolar broadening, i.e. overtone and MQMAS spectroscopy, the principles of which are outlined here. In addition, the possibility of distance measurements via the dipolar interaction using the REDOR technique is discussed. The combined information derived from distance measurements, quadrupolar and chemical shift parameters can be helpful for determination of the crystal structure, or for detection of impurity phases, as illustrated by surveying a number of case studies covering spin I = 1, 3/2, 5/2 and 7/2.

palladium complexes of ferrocenyl-functionalized N-heterocyclic carbenes with different substituents were synthesized. The molecular structures of selected complexes were determined by X-ray diffraction and show a pseudo-square-planar structure with a central palladium atom surrounded by carbene, pyridine, and two chloride ligands. The influence of the different substituents on the structure and reactivity of the complexes was studied. The catalytic properties of the complexes were investigated in the Larock indolization reactions of 2-bromoanilines with diphenylacetylene. Their performances slightly varied in this reaction, but the complex with mesityl substituent showed the best activity.

The reaction of MoBr₃ and pyridine at room temperature provided single crystals of mer-[MoX₃Py₃]. mer-[MoBr₃Py₃] crystallizes in P2₁/n monoclinic space group with cell dimensions a = 9.2297(5) Å, b = 12.911(8) Å, c = 15.7022(9) Å and β = 90.479(3)°. There are four formula units in a unit cell. Mo–N distances are in the range 2.196(8)–2.214(8) Å and Mo–Br distances are 2.573(1) Å and 2.574(1) Å. Fundamental vibrational frequencies of pyridine molecules are strongly affected upon coordination in all three coordination compounds: mer-[MoBr₃Py₃], mer-[MoI₃Py₃] and trans,trans-[MoBr₂Py₄][MoBr₄Py₂].

Quinoline bridged imidazolium precursors 5,8-bis(N-R-imidazolylidenylmethylene)quinoline PF₆^– salts [H₂L](PF₆)₂ [R = Me (1a), R = naphthylmethyl (1b)] were prepared by quaternization of N-methylimidazole and N-naphthylmethylimidazole with 5, 8-bis(bromomethyl)quinoline, respectively. Reaction of the imidazolium ligands 1a and 1b with Hg(OAc)₂ and Ag₂O in acetonitrile gave the macrocyclic transition metal carbene complexes [Hg₂L₂](PF₆)₄ (2a and 2b) and [Ag₂L₂](PF₆)₂ (3a and 3b), respectively. All the N-heterocyclic carbene complexes were characterized in detail by NMR, ESI-MS, and elemental analysis. Structures of complexes 2a and 3a were determined by X-ray diffraction studies. Structural studies revealed that the coordination arrangement of the central mercury atom in complex 2a displays a tricoordinate mode and the molecular conformation results in a“closed” form with the bridging quinoline functionality in the macrocycle, whereas the silver complex 3a does not show an coordiantion between the bridging quinoline and the Ag^I ion, which results in an “open” conformation of the macrocycle. The Hg^II and Ag^I NHC complexes showed similar UV absorption and luminescence in acetonitrile solutions.

Two heterospin complexes [Cu(NIT3Py)(cda)H₂O]·H₂O (1) and [Cu(NIT2Py)(cda)H₂O]·H₂O·CH₃OH (2) with Cu^II ions and pyridyl-substituted nitronyl nitroxide radicals (NITxPy = 2-(x′-pyridyl)-4, 4, 5, 5-tetramethyl-imidazoline-1-oxyl-3-oxide, x = 3, 2; H₂cda = 4-hydroxy-pyridine-2, 6-dicarboxylic acid) were synthesized and characterized structurally and magnetically. The single crystal structures show that the two complexes are both two-spin complexes, in which the different radicals make the two complexes have different hydrogen bonding interactions to form 2D and 1D supramolecular network for complexes 1 and 2, respectively. The magnetic measurements indicate that complexes 1 and 2 both exhibit antiferromagnetic interactions between Cu^II and radicals.

A series of five tripodal tridentate ligands (HO)C[(CH₂)_xNR₂](CH₂SR)₂ (HL¹–HL⁵) with {NS₂} donor set has been synthesized via an efficient two-step protocol starting from 1, 3-dichloroacetone. All five ligands bear a backbone hydroxo group that is available for further functionalization. The five ligands differ by the type of N-donor (NR₂ = pyridine-2-yl or imidazol-2-yl), by the spacer between the backbone-C and the N-donor heterocycle (x = 0, 1), and with respect to their topology, viz. whether two thioether-S are part of a cyclic 1, 4-dithiacycloheptane fragment or not (R = Et or –CH₂–). Copper(I) and copper(II) complexes have been prepared and studied in solution (ESI-MS, UV/Vis, and NMR spectroscopy in case of the copper(I) complexes) as well as in solid state (single-crystal X-ray diffraction of [(HL²)Cu(MeCN)]_n(OTf)_n, [(HL³)Cu(MeCN)](PF₆) and [(HL⁵)Cu(MeCN)]_n(PF₆)_n as well as [(L⁴)₂Cu₃(MeCN)₃](PF₆)₂ and [(L²)₂Cu₂Cl₂], [(L³)₄Cu₄](OTf)₄, and [(L⁴)₂Cu₂(MeCN)₂](OTf)₂; SQUID magnetometry of [(L²)₂Cu₂Cl₂] and [(L³)₄Cu₄](OTf)₄,). The ligand scaffolds show ambidentate character depending on the metal ion oxidation state. All copper(I) ions are found in distorted tetrahedral environment comprising an {NS₂} ligation of the tridentate ligand as well as an exogenous MeCN; either mononuclear complex cations or 1D polymeric structures are found. In case of all copper(II) complexes the backbone-alcohol group is deprotonated and bridges two metal ions, giving dinuclear or tetranuclear species with antiferromagnetic coupling. The Cu–S bond lengths are found to vary significantly, which reflects the plasticity of the Cu-thioether bond known from metalloproteins and synthetic analogs.

BaAl₂(NH₂)₈·2NH₃ was synthesized starting from an intermetallic phase with nominal composition Al₂Ba under ammonothermal conditions in a stainless-steel autoclave at 823 K and 245 MPa. Single crystals were grown on aluminum substrates and prepared under low-temperature conditions. The crystal structure (Rc (no. 167), a = 15.7370(17), c = 28.804(6) Å, Z = 1, 1829 reflections, 65 parameters, wR₂ = 0.07) was solved on the basis of single-crystal X-ray diffraction data. BaAl₂(NH₂)₈·2NH₃ contains isolated Al(NH₂)₄-tetrahedra forming two different types of channels along [001].

The crystal structures of the M₂NaIO₆ series (M = Ca, Sr, Ba), prepared at 650 °C by ceramic methods, were determined from conventional laboratory X-ray powder diffraction data. Synthesis and crystal growth were made by oxidizing I^– with O₂^(air) to I⁷⁺ followed by crystal growth in the presence of NaF as mineralizator, or by the reaction of the alkali-metal periodate with the alkaline-earth metal hydroxide. All three compounds are insoluble and stable in water. The barium compound crystallizes in the cubic space group Fm3m (no. 225) with lattice parameters of a = 8.3384(1) Å, whereas the strontium and calcium compounds crystallize in the monoclinic space group P2₁/c (no. 14) with a = 5.7600(1) Å, b = 5.7759(1) Å, c = 9.9742(1) Å, β = 125.362(1)° and a = 5.5376(1) Å, b = 5.7911(1) Å, c = 9.6055(1) Å, β = 124.300(1)°, respectively. The crystal structure consists of either symmetric (for Ba) or distorted (for Sr and Ca) perovskite superstructures. Ba₂NaIO₆ contains the first perfectly octahedral [IO₆]^5– unit reported. The compounds of the ortho-periodates are stable up to 800 °C. Spectroscopic measurements as well as DFT calculations show a reasonable agreement between calculated and observed IR- and Raman-active vibrations.

[FeFe] hydrogenase model complexes [Fe(CO)₃]₂[(μ-ECH₂)₂C(CH₂OH)₂] (E = S (1) or Se (2)) containing CH₂OH bridgehead substituents were synthesized via reaction of equimolar amounts of 4,4-bis(hydroxymethyl)-1,2-dithiolane (A) or 4,4-bis(hydroxymethyl)-1,2-diselenolane (B) with Fe₃(CO)₁₂ in toluene at 100 °C. The presence of OH groups in complexes 1 and 2 is found to influence the cathodic processes and their potentials. The catalytic reduction of acetic acid (AcOH) occurs by the anions 1^– and 2^–, while the neutral complexes are procatalysts.

The interaction of methyl(oxo)borane, CH₃BO, with typical Lewis bases (nitrogen based and N-heterocyclic carbenes) was investigated using density functional theory (B97-D, TPSS-D3), double hybrid density functionals (PWPB95-D3, B2PLYP-D3) in conjunction with empirical dispersion corrections, and coupled cluster theory involving singles, doubles, and a perturbative estimate of triple excitations [CCSD(T)]. A polarized quadruple-zeta basis set was used throughout. The interaction energies computed with the double-hybrid methods agree very well with CCSD(T). Compared to typical boron Lewis acids, the interaction energies are much smaller for methyl(oxo)borane, indicating that the BO triple bond results in significantly reduced Lewis acidity. An analysis of the mechanical bond strengths in CH₃BO and its complexes indicates that the relaxed BO force constants (compliance constants) and the stretching vibrations decrease with increasing strengths of the dative interactions.

The ability of the macrocyclic hexaaza-dithiophenolate macrocycles (H₂L^H6, H₂L^Me2H4, and H₂L^Me6) to support dinuclear zinc complexes has been examined. The macrocyclces contain two 4-tert-butylthiophenolate units which are connected by two lateral dipropylenetriamine units with different nature and patterns (secondary or tertiary) of the N donors (H₂L^H6: 6 × R₂NH, H₂L^Me2H4: 4 × R₂NH, 2 × R₂NMe, H₂L^Me6: 6 × R₂NMe). Three binuclear complexes ([Zn₂(L^H6)]²⁺ (1), [Zn₂(L^Me2H4)]²⁺ (2), and [Zn₂H₂(L^Me6)Cl₂]²⁺ (3)) were obtained, isolated as ClO₄^– or BPh₄^– salts, and characterized by CHN, ESI-MS, IR, and NMR spectroscopy, and X-ray crystallography (1(ClO₄)₂, 1(BPh₄)₂, 2(BPh₄)₂, 3(ClO₄)₂). In contrast to the parent N₆S₂ macrocycles with diethylenetriamine linkers which support bioctahedral [Zn₂L(L′)]ⁿ⁺ complexes (L' = bridging coligand), the present ligands coordinate to zinc with non-bridging thiolato donors to afford tetrahedral ZnN₃S (1,2) or ZnN₂SCl (3) coordination environments. The decrease of the coordination number from 6 in the [Zn₂L(L′)]ⁿ⁺ to 4 in the present complexes is attributed to the change of the chelate-ring size. The six-membered chelate rings in 1–3 allow larger bond angles and encourage tetrahedral coordination.

Abstract. Treatment of the dialkynylphosphine Mes–P(–C≡C–CMe₃)₂ (1) with diethylaluminum hydride (2) in an equimolar ratio afforded a mixture of compounds, in which a [3.2.0]-bicyclic compound 3 with annulated four-membered AlC₂P and five-membered P₂C₃ heterocycles could be identified by NMR spectroscopy. Excess of the hydride 2 yielded small quantities of the zwitterionic [4.3.0]-bicyclic compound 4, which formally resulted from the unique insertion of a diethylaluminum hydride molecule into the Al–C(vinyl) bond of the strained four-membered heterocycle of 3. A six-membered ring is formed which contains an Al–H–Al 3c-2e bond.

A new enantiopure heteroscorpionate ligand HOPhbpm^3menth (2) was synthesized in a one-pot synthesis. Ligand 2 was obtained in a pyridine-catalysed Peterson rearrangement starting from menthopyrazole, thionyl chloride, and salicylaldehyde. The evidence of κ³-coordination of the ligand was shown by the formation of a tetrahedral zinc complex [Zn-κ³-(OPhbpm^3menth)CH₃] (3) as well as an molybdenum complex [Mo-κ³-(OPhbpm^3menth)O₂Cl] (4).

Syntheses for 2-[1-(diarylphosphinoyl)-1-(pyridin-2-yl)methyl]pyridines, (8a, b), and 2-[1-(diarylphosphinoyl)-1,1-bis(methylpyridin-2yl)methyl]pyridines, (11a, b), (Ar = C₆H₅ and 2-CF₃C₆H₄), based on substitution of 2-methylpyridine fragments onto the exo methylene carbon atom of 2-[(diaryl)phosphinoylmethyl]pyridine platforms, are described. N-oxidations of 8a, b and 11a, b produced the 2-[1-(diarylphosphinoyl)-1-(1-oxy-pyridin-2yl)methyl]pyridine N-oxides (5a, b) and the 2-[1-(diarylphosphinoyl)-1,1-bis(1-oxy-methylpyridin-2-yl)methyl]pyridines (6a, b), respectively. The “short-arm“ pyridine fragment of 11a, b resists N-oxidation, and the fully oxidized molecules, 2-[1-(diarylphosphinoyl)-1,1-bis(1-oxy-methylpyridin-2-yl)methyl]pyridine N-oxides (7a, b) were not isolated. Molecular mechanics calculations for gas phase 1:1 ligand/lanthanide complexes indicated that 5a should accommodate a tridentate NO(meNO)PO coordination mode with minimal steric strain. In contrast, 7a cannot form tetradentate NO(meNO)₂PO chelates; however, tridentate binding should be accessible with minimal ligand strain. Coordination complexes of 8a, b, 5a, b, 6a, b and 11a, b with Ln(NO₃)₃ salts were isolated and a X-ray crystal structure for [Er(8a)(NO₃)₃(MeOH)₂]·CH₂Cl₂, revealed a monodentate Er–O=P interaction. On the other hand, complexes formed by a more symmetrical trifunctional phenylphosphino-bis-2-methylpyridine N, N, P-trioxide ligand, (meNO)₂PO*, {La[(meNO)₂PO*)](OTf)₂(MeOH)₃(H₂O)⁺}(OTf^–) and {Pr[(meNO)₂PO*)](OTf)(MeOH)₄⁺}(OTf^–)₂, realized a tridentate coordination mode. Solvent extraction behaviors for Eu^III and Am^III in nitric acid solutions using 5a, b, 6a, b, Ph₃PO and the parent bifunctional ligand 2-[(diphenylphosphanyl)methyl]pyridine N, P-dioxide (3a) in 1, 2-dichloroethane were assessed, and 5a, b and 6a, b were found to behave more like Ph₃PO than 3a.

The reactions of [Os(NO)Cl₅]^2– with glycine (GlyH), picolinic acid (PicoH), L-proline (L-ProH) and D-proline (D-ProH) afforded four novel complexes of the general formula [Os(NO)Cl₃(AA)]^–, where AA = Gly, Pico, L-Pro and D-Pro, respectively. X-ray diffraction studies have revealed that in all cases the same isomer type from three theoretically possible, has been isolated, namely mer(Cl), trans(NO, O)-[Os(NO)Cl₃(AA)]^–. Spectroscopic and electrochemical properties, behavior in aqueous solution and antiproliferative activity in three human cancer cell lines are also reported.

Metal ions poisoning can result from environmental factors, intentional action, or disruption of homeostasis. Although the origin of toxicity may be different, the treatment is similar. Chelation therapy aims to remove the excess of metal ions from tissues to stop further damage of cells. For almost every metal ion, molecules that are able to bind it and remove from the human body are known. Over the years some new chelating agents were discovered and introduced into clinical treatment. In this paper we have focused on typical chelators for metal ions, both essential and toxic for humans. The treatment of poisoning caused by essential metal ions is hard due to the risk of removing them from the biologically relevant molecules (e.g. enzymes). Acute metal ions poisoning is rather rare, so the development of chelators for such cases are historical, but prolonged toxicity of, especially, essential metal ions is extensively studied.

Using the bis(pyrazolyl)pyridinylmethane ligand α,α,α-bis(1-pyrazolyl)(2-pyridinyl)toluene {(ph)C(pz)₂(py)} for bioinorganic inspired coordination chemistry studies, we synthesised and structurally characterised three monofacial complexes [{(ph)C(pz)₂(py)}CoCl₂] (C1), [{(ph)C(pz)₂(py)}CuCl₂] (C2), [{(ph)C(pz)₂(py)}ZnCl₂] (C3) and the binuclear halogenido-bridged complexes [{(ph)C(pz)₂(py)}₂(μ-Cl)₂Fe₂Cl₂] (C4) and [{(ph)C(pz)₂(py)}₂(μ-Br)₂Cu₂Br₂] (C5). In four of these complexes, severe disorders between pyrazolyl and pyridinyl donor groups are observed such that bis(pyrazolyl) and (pyrazolyl)(pyridinyl) coordination modes are concomitantly found. The donor competition is dissected by DFT calculation of the energy differences between the two coordination modes and NBO analysis of the donor situation. The pyrazolyl units provide with more donor strength although pyridine is considerably more basic.

The plant metallothioneins (MTs) show high sequence diversity. Proposed to function mainly in metal ion homeostasis and detoxification these small cysteine-rich proteins exhibit pronounced affinities to metal ions with the electron configuration d¹⁰. Having previously studied the coordination abilities of two MTs from Cicerarietinum (chickpea) for divalent metal ions we now aim to expand the knowledge to the binding characteristics for Cu^I. Performing titration studies followed by UV and circular dichroism spectroscopy distinct differences between the two proteins are revealed.

The electron distributions in position and in momentum space of the hcp metals magnesium and zinc are investigated experimentally and compared to results of quantum-chemical calculations. Furthermore, a survey is given on recent analyses of the bonding properties of zinc and cadmium, using the method of increments. The experimental deformation densities were obtained by refining multipole models to X-ray diffraction data sets measured at 100 K with either Mo-K_α (Mg) or Ag-K_α (Zn) radiation. The final R_F values (Valray/Jana2006) are 0.0028/0.0034 (Mg) and 0.0068/0.0068 (Zn). The differences to deformation densities obtained from periodic density functional calculations are discussed. The effect of dynamical electron correlation on the electron density was analyzed, using cluster models. Compton profiles were measured with 88.67 keV synchrotron radiation at beamline ID15B at the ESRF in Grenoble. Varied orientations of the samples allowed for probing the projected momentum distribution along the [100], [423] and [001] directions. Fourier transforms of the computed reciprocal form factor B(r) resulted in the corresponding theoretical Compton profiles. It is suggested that the anomalous hcp structure of zinc is favored by a kinetic balancing of the valence electrons, i.e. correlation mediated 4s-3d interactions.

The Cu^II solution chemistry of synthetic derivatives of naturally occurring pseudo-octapeptides (patellamides and ascidiacyclamide) is described. The complex stabilities [mono- and dicopper(II) complexes] of five different ligands were determined by isothermal microcalorimetry (ITC), and square wave voltammetry (SQW) was used to elucidate the electrochemical properties. In agreement with published spectroscopic data, there is cooperative binding of two Cu^II ions and the overall stabilities are, in agreement with known stabilities of the natural ligands and expectations based on the donor sets (two N-based heterocycles and one amide per Cu^II), only moderate (K ≤ 10⁶). There is a slight dependence of the stabilities on the ligand structure (configuration of the side chains), and that derived from the natural products forms the most stable complexes. Due to the complex equilibria in solution and the instability of the reduced forms, voltammetry shows complex equilibria, which preclude the full assignment of all processes. The positive reduction potentials are in agreement with relatively low complex stabilities. These observations complete earlier studies, concentrating on spectroscopy and structural aspects, and are also discussed in relation to the possible biological function of the cyclic peptides, i.e. metal ion transport, oxygen activation, carboanhydrase, and phosphatase activities.

Setting out from protected L-cysteine a 2,5-diketopiperazine V can be synthesized, the reduction of which with NaBH₄/TiCl₄ leads to (6R,8aR)-7-methyl-6-(sulfanylmethyl)-thiazolidine [3,4-a] piperazine, L¹H as well as N,N′-dimethyl-(2R,5R)-bis(sulfanylmethyl) piperazine, L²H₂, which were separated and characterized. L²H₂ can be obtained selectively, if V is reduced by NaBH₄/TiCl₄ in the presence of DIEA·HCl, and it represents a precursor for a novel, chiral ligand, as after deprotonation it provides two thiolato and two amino donor functions for the coordination of a metal atom. Deprotonation of L¹H and L²H₂ with NaOMe followed by treatment with NiBr₂(dme) led to the isolation of the dimeric complexes [L¹NiBr]₂ (1) and [L²Ni]₂ (2), respectively. Both were fully characterized, and cyclic voltammetry indicated the possibility of Ni^II → Ni^III oxidations for complex 2. 2 can be regarded as a structural model for the A clusters of the acetyl coenzyme A synthase.

Two new dinucleating phenol-based ligands (m-HL_SMe and p-HL_SMe) bearing pyridine-containing pendant arms with a SMe group on one pyridine (meta or para position relative to the pyridine nitrogen atom) have been synthesized. After coordination by two copper(II) ions, the corresponding μ-phenoxido, μ-hydroxido dicopper(II) complexes were isolated and characterized by UV/Vis, EPR spectroscopy, single-crystal X-ray analysis (for the complex with the SMe substituent at the meta position) and electrochemistry. The presented compounds mimic the active site of type 3 copper enzymes and in particular the distinct environments of the copper ions.Both complexes are active as catalysts for the oxidation of 3, 5-di-tert-butylcatechol to the respective quinone. The catalytic properties of the complexes depend on substrate binding, as reflected by the K_M values determined for the complexes in presence of 3, 5-dtbc and are not correlated directly with the redox properties of the dicopper center.

The chemistry of cytotoxic platinum(II) complexes is more or less restricted to ligand exchange reactions, derivatization of coordinated ligands is cumbersome, and subsequent purification in many cases impossible. Consequently, kinetically more inert platinum(IV) complexes found their way into the development of novel, promising anticancer drugs. Research has focused more and more during the last years on the use of platinum(IV) complexes featuring one or two axial succinato ligands in which one carboxylic acid moiety is available for further derivatization. In order to gain a deeper insight into the mechanism of action, isotopically labeled platinum(IV) complexes with axial (1,4–¹³C₂)succinato ligands were synthesized and fully characterized by multinuclear (¹H, ¹³C, ¹⁵N, and ¹⁹⁵Pt) 1D- and 2D-NMR spectroscopy. Especially of note in this context is a long range ¹H,¹³C shift correlation signal detected between the equatorial ammine protons and the axially coordinated carboxylato moiety. Furthermore, their behavior in extracts of SW480 cancer cells was investigated. Preliminary results demonstrate that cisplatin analogs are reduced significantly faster in comparison to carboplatin analogs.

A new chiral racemic ligand (o-carboranyl)bis(2-hydroxymethyl)pyridine oCB(hmpH)₂, that is composed of a central o-carborane unit where two arms radiate out of the cluster carbons each one containing a 2-pyridylmethylalcohol chelating arms, provides two potentially bidentate {NO} or one tetradentate {N₂O₂} binding pockets. An unprecedented octahedral Co^II complex [CoCl₂(anti-oCB(hmpH)₂] was obtained under aerobic conditions and characterized by X-ray crystallography as well as IR and NMR spectroscopy. anti-oCB(hmpH)₂ acts as a tetradentate N₂O₂-ligand affording the complex as a racemic mixture of cis-α Δ-[CoCl₂(^RRanti-oCB(hmpH)₂)] and Λ-[CoCl₂(^SSanti-oCB(hmpH)₂)]. The new ligand oCB(hmpH)₂ appears to be suitable for producing a variety of new chiral-at-metal complexes.

An unprecedented Mo/Cu/S cluster, [Et₄N]₄[Mo₃Cu₆S₁₄] (1) was obtained from the smaller cluster, [Ph₄P]₂[MoS₄CuCl], in the presence of aqueous solution of tetraethylammonium hydroxide in DMF/i-propanol by self-rearrangement. The crystal structure shows that butterfly-shaped {MoS₄Cu₂S₂} fragments are connected via μ₃-S atoms to form a cage-like structure, [Mo₃Cu₆S₁₄]^4–. The rearrangement of the Mo/Cu/S cluster may reflect the structural instability of Orange protein (ORP) cofactor.

Metallothioneins achieve metal binding specificity by modulation of their amino acid sequences through evolution. Non-coordinating residues seem to play a key role in this function, and among them histidine may be of particular importance. Here we report how this residue regulates Cu^I binding to a highly copper specific isoform, the CuMT of the snail Helix pomatia, by analysis of the recombinant complexes yielded by a constructed mutant where this residue has been changed to an alanine.

Searching for new promising metal-based drugs for the treatment of parasitic diseases against Trypanosoma cruzi, three related oxidovanadium(IV) complexes, [V^IVO(SO₄)(H₂O)₂(NN)], with the phenanthroline derivatives (NN) [1,2,5]thiadiazolo[3,4-f][1,10]phenanthroline (tdzp), 1, 10-phenanthroline-5, 6-dione (phendione), and 5, 6-epoxy-5, 6-dihydro-1, 10-phenanthroline (epoxyphen) are synthesized, characterized, and evaluated in vitro as anti-T. cruzi agents. The compounds are characterized in the solid state and in solution by elemental analysis, electrospray ionization mass spectrometry (ESI-MS), conductimetric measurements, and infrared (FTIR), UV/Vis, and electronic paramagnetic resonance (EPR) spectroscopy. EPR spectroscopy suggests that the ligands act as bidentate, binding through both nitrogen donor atoms in an axial-equatorial mode. DFT calculations corroborate the structural assignments. The stability of the complexes in solution is evaluated by EPR and ⁵¹V- NMR spectroscopy and all complexes show reasonable stability. The anti-T. cruzi activity of the complexes was tested by measuring the growth inhibitory effect on the epimastigote life cycle form of the parasite (Dm28c strain). All complexes show IC₅₀ values in the micromolar range against T. cruzi and display activities of the same order of that of Nifurtimox, but lower than that of the previously reported analogue [V^IVO(SO₄)(H₂O)₂(dppz)] (dppz = dipyrido[3, 2-a:2′,3′-c]phenazine). Furthermore, DNA was evaluated as a potential target by using atomic force microscopy (AFM), showing that the complexes display ability to interact with this biomolecule.

A series of seven molybdenum(II) allyl dicarbonyl complexes of the general formula [Mo(allyl)(CO)₂(N-N)(py)]⁺, in which N-N is a bidentate chelating polypyridyl ligand with variable aromatic surface area, was synthesized by a new two-step approach and fully characterized by IR and NMR spectropscopy, ESI mass spectrometry, and elemental analysis. The n-octanol/water partition coefficient logP increased with the size of the N-N ligand from –0.4 to +1.8. The biological activity on adherent HT-29 and MCF-7 as well as non-adherent NALM-6 human cancer cell lines was studied with various assays, allowing also an insight in the mechanism of cell death. Most of the title compounds showed high antiproliferative activity in the low micromolar concentration range on all three cell lines tested, which however did not correlate much with the logP values determined. Apoptosis could be demonstrated as the major pathway of cell death for selected compounds and cell lines, setting on at 5 μM for the most active complex. Interestingly, no difference in apoptosis induction was observed between MCF(+/–) cell lines differentiated by expression of pro-apoptotic enzyme caspase-3 (+) or a lack thereof (–). This indicates an apoptosis induction pathway, which is independent of caspase-3.

Three 3-amino-1, 2, 4-triazole (atz)-based paramagnetic complexes, [Mn(atz)(pa)]_n (1), {[Mn(atz)_1.5(hip)]·H₂O}_n (2), and [Mn(H₂O)₂(atz)₂(nb)₂] (3) (H₂pa = o-phthalic acid, H₂hip = 5-hydroxylisophthalic acid, and Hnb = p-nitrobenzoic acid) were prepared by introducing different carboxylate-containing aromatic coligands, and structurally and magnetically characterized. Helical Mn^II-atz and bent Mn^II-pa^2– chains are crosslinked by sharing the same metal sites to generate a honeycomb-shaped framework of 1. The undulated Mn^II-atz layers constructed from 22-member metallomacrocycles are periodically supported by ditopic hip^2– ligands to lead to a pillared-layer structure of 2. In contrast, complex 3 is a centrosymmetric mononuclear entity, which is assembled into a three-dimensional supramolecular network by abundant hydrogen-bonding interactions. The structural difference of 1–3 is significantly due to the combinations of the flexible coordination modes adopted by the mixed atz and carboxylate groups. Weak and comparable antiferromagnetic couplings are observed in the nearest neighbors of 1–3, which are cooperatively transmitted either by short carboxylate and/or atz heterobridges or by weak non-covalent interactions.

This research report is devoted to guanidinyl-functionalized aromatic compounds (GFAs), which represent a new class of strong electron donors and redox-active ligands. Charge and spin density studies provided the basis for the development of a rich coordination chemistry, which includes molecular complexes as well as 1D coordination polymers.

The crystal structure of the hexaborides MB₆ of alkali, alkaline-earth, and rare-earth metals displays a network of interconnected B₆ octahedra, while isolated B₆H₆ units occur in the molecular crystal K₂[B₆H₆]. For the case of a total charge transfer of two electrons from the metal atoms, the B₆ units serve as classical examples of electron deficient clusters. QTAIM and ELI-D analyses of chemical bonding based on solid state DFT/APW+lo quantum chemical calculations were performed. Consistent with Wade's rules, a number of about seven endohedral bonds for the octahedral units is recovered from the delocalization index (DI). Detailed analyses of two- and three-center delocalization indices yield a clear two-center character of the exohedral B–B bonds and a mixed two- and three-center character of the endohedral B–B bonds. The picture obtained by topological analysis of ELI-D is in agreement with the DI results. With changing effective electron transfer from the metal atoms, electronic saturation of the intra-cluster bonding is found, which leads to the notion of generally two-valent rare-earth atoms in MB₆ hexaborides.

The bromidovanadium complexes cis-[V^IIBr₂(bith)] (1) [bith = 1, 6-bis(2-benzimidazolyl)-2, 5-dithiahexane], cis-[V^IIBr₂(pth)] (2a) [pth = 1, 6-bis(2-pyridyl)-2, 5-dithiahexane], cis-[V^IIIBr₂(pth)]Br (2b), trans-[V^IIBr₂(tmeda)₂] (3) (tmeda = tetramethylethylenediamine), fac-[V^IIIBr₃(9S3)] (4) (9S3 = 1, 4, 7-trithiacyclononane), mer-[V^IIIBr₃(thf)₃] (5) (thf = tetrahydrofurane), and trans-[V^IVOBr₂(thf)₂H₂O] (6) were prepared and characterized by, inter alia, XRD (5, 6), K-edge XAS (3, 4) or L-edge XAS (2a, 2b). The complexes are also addressed in the context of the potential of halogenidovanadium compounds in catalytically conducted reactions, including biogenic processes.

Hemoglobin (Hb) is the most abundant protein in human blood and we showed that under oxidative/nitrative stress conditions it is susceptible to cysteine oxidation, tyrosine nitration, and formation of a dimer of Hb subunits through tyrosine linkage. In the presence of hydrogen peroxide, Hb and its subunits efficiently convert nitrite into reactive nitrogen species, through reactions that are typical of peroxidases. If an exogenous phenolic substrate is present, Hb promotes its nitration with a fivefold higher efficiency with respect to the peroxidase-like phenol coupling reaction. In the absence of an exogenous substrate, the protein itself undergoes covalent modification. Trypsin treatment of Hb modified under conditions mimicking pathophysiological conditions, followed byHPLC-ESI-MS/MS analysis, allowed detection of nitration of Yα24, Yα42, Yβ130 and Yβ145, and conversion of Cα104, Cβ93 and Cβ112 into cysteine sulfinic acids. As additional biomarkers of nitrative stress, we found a covalent dimer of Hb αβ subunits and covalently linked heme-peptide. The dimer is selectively nitrated at Yα42. In a preliminary analysis of samples of human blood we found that low amounts of the dimer of subunits are always present. Therefore, if a correlation between the extent of Hb subunits coupling and pathological states could be established, this dimer could become an easily detectable biomarker of pathological conditions.

A series of macrocyclic Ni/Fe/S cluster complexes were synthesized and structurally characterized. The macrocyclic type of (diphosphine)Ni-bridged double butterfly Fe/S complexes [μ-SCH₂CH₂OCH₂CH₂S-μ][(μ-S=CS)Fe₂(CO)₆]₂-[Ni(diphosphine)] (1–3; diphosphine = dppe, dppv, dppb) were prepared by treatment of the dianion [{μ-SCH₂CH₂OCH₂CH₂S-μ}{(μ-CO)Fe₂(CO)₆}₂]^2–, generated in situ from Fe₃(CO)₁₂, Et₃N, and HSCH₂CH₂OCH₂CH₂SH with excess CS₂ followed by treatment of the resulting dianion [{μ-SCH₂CH₂OCH₂CH₂S-μ}{(μ-SC=S)Fe₂(CO)₆}₂]^2– with (diphosphine)NiCl₂. The three complexes 1–3 were characterized by elemental analysis and IR, ¹H NMR, and ³¹P NMR spectroscopy. In addition, the molecular structures of 2 and 3 were established by X-ray crystallography.

A new family of hydrazone-based nucleosides for use in metal-mediated base pairs was devised. The artificial nucleobases are derivatives of the papy ligand (papy = pyridinecarboxaldehyde-2′-pyridylhydrazone). By replacing the pendant pyridine moiety in papy by furan and thiophene, respectively, tridentate nucleosides with N, N, N-, N, N, O- and N, N, S-donor sites were obtained. As only a few transition metal complexes with pendant furan ligands have been reported, a model nucleobase for the N, N, O-donor nucleoside was synthesized. The molecular structures of its Cu²⁺, Ni²⁺, and Co²⁺ complexes are reported. In all complexes, only weak M–O(furan) bonding is observed. The Co²⁺ complex displays a pentagonal bipyramidal coordination arrangement. In general, the structures of the metal complexes suggest that the respective nucleosides can be applied in metal-mediated base pairs.

The mononuclear complex [Ni(HOphen)(OSO₃)(H₂O)₃]·5H₂O (HOphen = 1, 10-phenanthrolin-2-ol) was prepared and its single structure was determined by X-ray crystallography. In this complex, the Ni^II ion has a distorted octahedral arrangement. Crystal structure analysis shows that two kinds of π–π stacking interactions and C–H···O short contact intermolecular interactions exist among the adjacent complexes. Fitting to the variable-temperature magnetic susceptibility data gave the magnetic coupling constant, 2J = –0.98 cm^–1. Theoretical calculations, based on density functional theory (DFT) coupling with the broken-symmetry approach (BS), revealed that the π–π stacking magnetic coupling pathways resulted in weak ferromagnetic interactions with 2J = 4.86 cm^–1 and 2J = 4.16 cm^–1, respectively, for the adjacent Ni^II ions with separations of 8.568(19) Å and 8.749(32) Å, respectively; whereas the magnetic coupling pathway of the C–H···O short contact intermolecular interaction led to a weak antiferromagnetic interaction with 2J = –17.62 cm^–1 for the adjacent Ni^II ions with a separation of 10.291(26) Å. The ferromagnetic coupling sign can be explained by the McConnell I spin-polarization mechanism.

Abstract. Triorganoboranes BR₃, Et-9-BBN, BPh₃, and B(C₆F₅)₃, were compared in their reactivity towards various dialkynyl(diorgano)tin compounds (R¹₂Sn(C≡C–R²)₂ with R¹₂ = –(CH₂)₅–, R² = H (a), R¹ = nBu, R² = H (b), R¹ = Ph, R² = H (c), R¹ = R² = nBu (d)). 1, 1-Carboboration took place readily in two consecutive steps (inter- and intramolecular), leading either to stannoles or to 1, 4-stannabora-cyclohexa-2, 5-dienes, or mixtures thereof. The weakest Lewis-acidic triorganoboranes BEt₃ and Et-9-BBN afford selectively stannoles with diethynyltin compounds, whereas the strongly electrophilic B(C₆F₅)₃ leads selectively to 1, 4-stannabora-cyclohexa-2, 5-dienes for all dialkynyltin compounds studied. In several cases, zwitterionic intermediates could be detected by multinuclear magnetic resonance spectroscopy (¹H, ¹¹B, ¹³C, and ¹¹⁹Sn NMR), and the molecular structure of such an intermediate as well as that of the final product, an 1, 4-stannabora-cyclohexa-2, 5-diene, could be determined by X-ray crystallography.

The determination of the phase diagram of the binary system sodium perchlorate – water is reported. Beside the eutectic point, two polymorph crystal structures of sodium perchlorate dihydrate were determined. The two crystal structures are discussed, compared to each other and to other known sodiumhalide dihydrate crystal structures. The two polymorphs of the perchlorate dihydrate represent the two variants of connected octahedra in the layer structure found for sodium halide dihydrates.

The coordination behavior of two Schiff base ligands, N,N′-bis(3-carboxysalicylidene)ethylenediamine (H₂L¹) and N,N′-bis(3-carboxysalicylidene)propylenediamine (H₂L²), towards magnesium ions is reported. The ligands show different binding site selectivity for Mg²⁺ depending on the solvent. In complexes isolated from aqueous or methanolic solutions the metal ion resides in the outer O₂O₂ compartment. The X-ray analysis of the complex of H₂L¹ showed the complex to be dimeric with magnesium being coordinated by two phenolate and two carboxylate oxygens, a bridging phenolate oxygen, and a water ligand. In aprotic solvents like dimethylsulfoxide (DMSO) and dimethylformamide (DMF) magnesium migrates to the inner N₂O₂ binding site. In DMSO solution containing small amounts of water, both isomers co-exist. A similar solvent-dependent site selectivity is not observed for zinc ions.

Crystalline CrOCl₃ contains [Cl₂OCr(μ-Cl)₂CrOCl₂] molecules with two square pyramidal CrOCl₄ units sharing a common edge and with the Cr–O arranged anti, a new structure type for transition metal MOX₃ compounds. Crystals are monoclinic with space group P2₁/c, Z = 4, with a = 5.735(5), b = 13.738(7), c = 11.318(4) Å, α = 90°, β = 98.346(6)°, γ = 90°. Its IR and UV/Vis spectra are reported and compared with those of the C_3v monomer found in the gas phase. Structures are also reported for M₂[CrOCl₅] (M = Cs or Rb) and show a pseudo-octahedral anion. Cs₂[CrOCl₅] adopts a K₂PtCl₆-type structure with [CrOCl₅]^2– ions randomly orientated, but Rb₂[CrOCl₅] is orthorhombic with space group Pnma with a = 13.6471(7), b = 9.9175(5), and c = 6.9562(4) Å. Rietveld refinement of the data on the rubidium salt gave Cr–O = 1.628(1), Cr–Cl_transO = 2.652(7), Cr–Cl_transCl = 2.239(8)–2.342(3) Å. Corresponding Cr^V oxide bromide species do not form.

On the basis of QTAIM and ELI-D partitioning of position space two- and three-center delocalization indices were calculated for fifteen MB₂ phases with the crystal structure of AlB₂ type. The bonding picture in main-group metal diborides is closest related to graphite with dominant covalent B–B bonding, albeit with lower effective bond order. For MgB₂ an exceptionally large distant electron sharing was found. Transition-metal diborides display smaller effective bond orders B–B but higher effective bond orders TM–B and TM–TM than main-group metal diborides. The large chemical flexibility of this structure type is caused by counterbalancing effects of B–B bonding vs. M–B and M–M bonding. Different three-center fluctuation channels of bonds B–B are found for main-group and transition-metal diborides, namely B–B–B for the former and B–B–M for the latter. With the technique of ELI-D/QTAIM intersection the increasing importance of B₂→4M bond charge fluctuations along each row of the periodic table can be recovered already at the topological level of analysis.

Studies on the reactivity of the novel bis(phosphine) platinum complex [Pt{P(CH₂Cy)₃}₂] towards haloboranes are presented. The resulting complexes of the general formula trans-[Pt{B(R)R′}X{P(CH₂Cy)₃}₂] were isolated in good to excellent yields (82–91 %) and the molecular structure of trans-[Pt{B(Br)Fc}Br{P(CH₂Cy)₃}₂] is reported. The reactions of 1, 4-(Br₂B)₂C₆H₄ and 1, 3, 5-(Br₂B)₃C₆H₃ with two and three equivalents of the platinum precursor yield the corresponding di- and trinuclear boryl platinum complexes, respectively. The structural characterization of the first trinuclear triboryl complex 1, 3, 5-trans-[Pt(BBr)Br{P(CH₂Cy)₃}₂]₃C₆H₃ extends the number of possible structural motifs in boryl platinum chemistry by a noteworthy example and confirms that P(CH₂Cy)₃ has flexible steric bulk.

N-methyl-1, 3-propylenediaminoboryl ferrocene (1-H) was obtained by a three-step synthesis: i) At first ferrocene was reacted with BBr₃ to give dibromoboryl ferrocene (FcBBr₂). ii) In a second step FcBBr₂ was transformed into FcB(OMe)₂ by treatment of FcBBr₂ with Me₃SiOMe. iii) Finally reaction of FcB(OMe)₂ with H₂NCH₂CH₂CH₂NMeH yielded the boryl ferrocene 1-H. In addition we examined the metalation of 1-H with magnesium 2, 2, 6, 6-tetramethylpiperidide (TMP) and mixtures of Li(TMP)/Mg(TMP)₂. The reaction of 1-H with 0.5 equivalent of Mg(TMP)₂ yielded quantitatively the homoleptic complex Mg[1]₂ whereas metalation of 1-H with 1.5 and 2 equivalents of Mg(TMP)₂ gave product mixtures. However, N,N'-dimethyl-1, 3-propylenediaminoboryl ferrocene (1-Me) and the ortho-methylated derivatives 2-Me and 3-Me (3-Me bears additionally one Me group in 1′-postion) could be identified after derivatization with Me₂SO₄. The metalated ferrocene derivative (Li₂(THP)₂Mg₃(TMP)₂[3]₂) which is bearing one Li and one Mg atom in the ortho-position and a further two Mg atoms in N- and 1′-positions, was formed in good yield by treatment of 1-H with an excess of a 1:2 mixture of Li(TMP) and Mg(TMP)₂ in tetrahydropyran (THP). Single crystals of the racemic complex Li₂(THP)₂Mg₃(TMP)₂[3]₂ were available by gas-phase diffusion of hexane into a concentrated THP solution at ambient temperature (space group C2/c). The crystal structure of Li₂(THP)₂Mg₃(TMP)₂[3]₂ displays a racemic dimer of the R_p- and the S_p-enantiomer.

This study features the preparation of three new energetic C-azido-1,2,4-triazoles, with the anion of one being a new binary C–N compound. 5-Azido-1H-1,2,4-triazole-3-carbonitrile (1) was prepared from 5-amino-1H-1,2,4-triazole-3-carbonitrile and further derivatized to 5-azido-1H-1,2,4-triazole-3-carbohydroximoyl chloride (5) with 3-azido-1H-1,2,4-triazole-5-carboxamidoxime (3) as an intermediate. The ability of 1 and 3 for salt formation was shown with the respective silver salts 2 and 4. All compounds were well characterized by various means, including IR and multinuclear NMR spectroscopy, mass spectrometry, and DSC. The molecular structures of 1, 3, and 5 in the solid state were determined by single-crystal X-ray diffraction. The sensitivities towards various outer stimuli (impact, friction, electrostatic discharge) were determined according to BAM standards. The silver salts were additionally tested for their potential as primary explosives.

Neutral halogenido nitrosyl metal complexes and their history are reviewed. The mass spectra indicate the dimeric nature of [(ON)Ni(μ-I)₂Ni(NO)] and of [(ON)Pd(μ-Cl)Pd(NO)] whereas hitherto a tetramer was favored for nitrosyl nickel iodide.

. (F₅C₆)₂BNMe₂ (1) was prepared and (F₃C)₂BNMe₂ (2) was resynthesized. The crystal structures of both compounds were determined. In contrast to 2, compound 1 does not react with diazomethanes under carbine insertion into the BN bond. In this way the known (F₃C)₂BCH(SiMe₃)NMe₂ (3) was resynthesized from 2 and its solid-state structure was determined. The electron densities of compounds 1, 2, and 3 and those of the simpler model compound (F₃C)₂BCH₂NMe₂ (4) as well as that of the BN/CC isoelectronic compound (F₃C)₂CCH₂CMe₂ (5) for comparison were calculated and their topologies analysed in terms of the Quantum Theory of Atoms in Molecules (QTAIM). Despite 2 has a shorter B–N bond in calculations and in the crystal than 1, the atomic charges and electron density parameters to QTAIM are very similar for both compounds and cannot explain the different reactivity. The three-membered rings 3 and 4 do not show bond-critical points for their B–N bonds. The nature of the B–N bond region was also analysed in terms of the source function contributions in QTAIM, which demonstrated the importance of the close proximity of a third atom in three-membered rings for the charge density topologies in such systems.

This Research Report provides an overview on synthesis, structure, and reactivity of the recently discovered carboranylamidinate ligands. Carboranylamidinate anions of the type [(o-C₂B₁₀H₁₀C(NHR)(=NR)]^– (R = iPr, cyclohexyl) are readily accessible via addition of o-lithiocarborane to N,N′-carbodiimides R–N=C=N–R. They combine the highly versatile characteristics of both amidinates and carboranes in one unique ligand system. Unlike simple amidinate anions, the carboranylamidinates coordinate to metal ions not as typical N,N′-chelating ligands but adopt an unexpected κ²C, N-bonding mode. The free imine functionality in carboranylamidinates can be further deprotonated. The resulting dianions were demonstrated to be excellent starting materials for novel boron-rich heterocycles incorporating e.g. Si, Sn, P, or transition metals such as Ti, Zr, Rh, and Ir. Further modification of the carboranylamidinate cage structure includes the introduction of additional functional groups like –SH or –SeH as well as the selective removal of a boron atom with formation of novel nido-type dicarbollylamidinate ligands. An initial study already showed that transition metal carboranylamidinates are potentially useful as polymerization catalysts.

A new low-temperature synthesis route of the strongly red-emitting Eu²⁺ activated nitride phosphor CaAlSiN₃ is presented. The fluorides CaSiF₆ and AlF₃ were used as a source of metal ions and Li₃N as a nitrogen source. A KCN/LiCl flux system was employed to lower the temperature of the reaction from 1100 to 750 °C. The course of the reaction was studied by differential thermal analysis, and the product of the reaction was inspected by X-ray powder diffraction and luminescence measurements of CaAlSiN₃:Eu.

Potassium hexafluoridotechnetate(IV), K₂[TcF₆], slowly reacts in aqueous solution with acetohydroxamic acid with formation of the ammine nitrosyltechnetium(I) complex [Tc(NO)(NH₃)₄F]⁺. The product crystallizes as mixed TcF₆^2–/HF₂^– salt of the composition [Tc(NO)(NH₃)₄F]₄[TcF₆][HF₂]₂. [Tc(NO)(NH₃)₄F]⁺ represents the first nitrosyltechnetium complex with a fluorido ligand in its coordination sphere. The Tc–F bonds in two crystallographically independent species are 1.987(2) and 2.034(2) Å, respectively. This is slightly longer than in the [TcF₆]^2– counterion.

The phenol-tailed porphyrin ligand, H₃L was synthesized as a model compound for catalases. H₃L and its corresponding iron complex [Fe(L)] were synthesized by using the precursor, 5-(8-ethoxycarbonyl-1-naphthyl)-10, 15, 20-triphenyl porphyrin (ENTPP). They were characterized by ¹H NMR spectroscopy, mass spectrometry, X-ray crystallography, and cyclic voltammetry. All the results have confirmed that the phenol group is covalently attached to the porphyrin. In the iron complex, phenolate oxygen is coordinated to iron(III) as the fifth ligand, leading to the five-coordinate high-spin iron(III) species.

Sodium 5-nitrotetrazolate dihydrate (NaNT) is a useful precursor compound for the synthesis of lead-free primary explosives; however, currently employed syntheses for the compound are tedious, dangerous, and plagued by impurities. Through comprehensive analysis, we elucidate the identity of the most detrimental impurities and further report an improved procedure for preparation of NaNT, which greatly improves the purity, while avoiding the handling of acid copper(II) nitrotetrazolate, a highly sensitive explosive intermediate. In the new procedure, 5-aminotetrazole is diazotized with sodium nitrite, cupric sulfate, and nitric acid. Copper is precipitated as its oxide and the aqueous solution evaporated. After soxhlet extraction with acetone, large crystals of NaNT are obtained. The prepared material is suitable for preparation of lead azide replacement DBX-1 [copper(I) 5-nitrotetrazolate] as evidenced by successful use in M55 stab detonators.

A successful mechanochemical synthesis of strontium terephthalate trihydrate is described for the first time. The dehydration of Sr(C₈H₄O₄)·3H₂O occurs at about 100 °C and results in a well-defined strontium terephtalate, Sr(C₈H₄O₄), thermally stable up to 550 °C. Both compounds are not described so far in the literature. Their structures were solved by ab initio structure determination and subsequent Rietveld refinement of the powder diffraction data. Further methods like DTA-TG, MAS NMR and FT-IR spectroscopy, and BET measurements were used to characterize these compounds.

Along with X-ray diffraction measurements, ²⁵Mg solid state NMR experiments were performed in natural abundance at 9.4 T on crystalline and mechanically milled samples of MgO, Mg(OH)₂, MgF₂, and magnesium hydroxide fluorides Mg(OH)_xF_2–x prepared on mechanochemical and sol-gel syntheses routes. In addition to single pulse and spin-echo sequences, both static ¹H-²⁵Mg CP and ¹⁹F-²⁵Mg CP measurements allowed the registration of ²⁵Mg spectra in attractive short measurement times. Although an assignment of different magnesium species in magnesium hydroxide fluorides is only hardly possible, position and line shapes of ²⁵Mg spectra of magnesium hydroxide fluorides reflect chemically reliable trends. All samples studied here show a sixfold fluorine, oxygen, or mixed fluorine / oxygen coordination of magnesium, also in highly disordered samples.

Several novel materials were investigated as energetic chlorine donors, specifically for the preparation of perchlorate-free pyrotechnic formulations with low-smoke output. The novel compounds, 2-chloromethyl-2-methyl-5,5-dinitro-1,3-dioxane (1-CDN), 2,2-bis(chloromethyl)-5,5-dinitro-1,3-dioxane (13-CDN), and 2-(dichloromethyl)-2-methyl-5,5-dinitro-1,3-dioxane (11-CDN), were formulated with a variety of fuels and oxidizers and their resulting colored flames analyzed for color quality. The preparation and preliminary characterization of these energetic chlorine donors are described.

The alkaline earth metal compounds AETMg₂ and AETCd₂ (AE = Ca, Sr; T = Pd, Ag, Pt, Au) were synthesized by induction-melting (or in muffle furnaces) of the elements in sealed niobium ampoules. The new phases were characterized by powder X-ray diffraction. The structures of SrPdMg₂ and SrPdCd₂ were investigated by X-ray diffraction on single crystals: MgCuAl₂ type, Cmcm, a = 436.42(4), b = 1130.1(1), c = 820.54(7) pm, wR₂ = 0.0115, 511 F² values for SrPdMg₂ and a = 443.5(2), b = 1063.0(2), c = 810.2(2) pm, wR₂ = 0.0296, 386 F² values for SrPdCd₂ with 16 variables for each refinement. The magnesium and cadmium atoms build up [TMg₂] and [TCd₂] polyanionic networks, which leave cavities for the calcium and strontium atoms. The bonding variations within the polyanions, which are mainly influenced by the length of the b axis are discussed. Ab initio calculations of electronic structure, charge densities, and chemical bonding, characterize SrPdMg₂ with a larger cohesive energy than SrPdCd₂. This is illustrated by larger bonding Pd–Mg interactions, opposite to compensating Pd–Cd between bonding and antibonding states.

The synthesis, spectroscopic and structural characterisation of a series of [M(hfip)₆]^– (M = Nb, Ta; hfip = O–C(H)(CF₃)₂) salts that are the typical starting materials to introduce these weakly coordinating anions by metathesis reactions into a given system is described. The salts Li[Nb(hfip)₆] and Li[Ta(hfip)₆] formed in 65 to 77 % yield from freshly sublimed MCl₅ and Li[hfip]. By contrast, several attempts to synthesize Li[Sb(hfip)₆] on the similar route (replace NbCl₅ by SbCl₅) failed to yield a pure product. Upon metathesis of the Li-niobate with AgF in CH₂Cl₂, the pure Ag[Nb(hfip)₆] formed. Mixing Li[Nb(hfip)₆] with an equimolar amount of Cl–CPh₃ in CH₂Cl₂ gave the yellow [CPh₃][Nb(hfip)₆]. Several of the compounds were characterized by X-ray analysis. Thus, the crystal structures of the Li⁺- and Ag⁺-solvates 1, 2-C₆H₄F₂{LiNb(hfip)₆}₂, [Li(H₂O)][Ta(hfip)₆], and [Ag(C₆H₅F)][Nb(hfip)₆] as well as that of [CPh₃][Nb(hfip)₆] were solved and are described in this work.

The organically templated pentaborate [C₁₀N₂H₉][B₅O₆(OH)₄]·H₃BO₃·H₂O (1a) was synthesized by boric acid and 4, 4′-bipyridine in aqueous solution and characterized by single-crystal X-ray diffraction, elemental analysis, FTIR spectroscopy, thermogravimetric analysis, powder X-ray diffraction, and photoluminescence spectroscopy. The compound crystallizes in the triclinic system with space group P (a = 9.196(3) Å, b = 9.822(3) Å, c = 12.113(3) Å, α = 66.243(3)°, β = 76.998(3)°, γ = 75.067(3)°, V = 958.4(5) ų, and Z = 2). The polyanions form a novel 3D supramolecular network with three kinds of channels by extensive hydrogen bonds. The title compound shows a UV photoluminescence with an emission maximum at 372 nm upon excitation at 248 nm, and the photoluminescence can be modified from UV to blue by means of a simple heat-treatment process. The pentaborate could be a promising blue component for possible application in the white LED.

Although terminal chalcogeno ligands are well known for the group 5 and 6 transition metals, they are highly unusual for the oxophilic group 4 metals and unknown so far for the lanthanides or actinides. Cs₃UP₂S₈, is the first actinide compound containing a terminal M=S group. It was synthesized by reacting uranium metal, Cs₂S, S, and P₂S₅ in a 4:1:8:3 ratio at 700 °C in an eutectic LiCl/CsCl mixture. The crystal structure was determined by single-crystal X-ray diffraction techniques. Cs₃UP₂S₈ crystallizes in the rhombohedral space group R [a = 15.5217(8) Å; c = 35.132(2) Å, V = 8305.0(8) ų, Z = 18]. The crystal structure is based on a tetrahedral network type, wherein the uranium atoms are coordinated by a unusual sulfido moiety and thiophosphate groups in a pseudo-tetrahedral fashion. The U=S distance of 2.635(3) Å observed in the sulfide moiety is approx. 0.2 Å shorter than the average U–S single bond length, indicating a double-bond type character.

Three new metal complexes were synthesized by reactions of [bis(2-amino-ethyl)-amino]-acetic acid (HL) and different metal salts at different pH values. Their structures were characterized by X-ray crystallography. Interestingly, under acidic conditions, the dinuclear structure {Cu₂[H(L)]₂Cl₂}(ClO₄)₂ (1) was obtained, whereas under alkaline conditions, the complexes {[Cu(L)](ClO₄)}_n (2) and [Cd(L)Cl]_n (3), which exhibit distinct one-dimensional (1D) structures, were obtained. The results indicate that the pH value, metal ions, and anions have remarkable influence on the formation and structure of the complexes.

Ytterbium complexes supported by a linked bis(β-ketoiminato) ligand, N,N′-ethylenebis(benzoylacetoimine) (H₂L), were synthesized and their catalytic behavior was explored. The reaction of YbCl₃ with 1 equiv. of LLi₂ afforded the mononuclear ytterbium chloride LYbCl(THF)₂ (1) in high yield. Complex 1 can be used as starting material to prepare β-ketoiminate-ytterbium derivatives. Treatment of complex 1 with NaN(SiMe₃)₂ produced the dimeric ytterbium amide {LYb[N(SiMe₃)₂]}₂ (2), while the similar reaction of complex 1 with NaOAr (ArO = 2, 6-tBu-4-MeC₆H₂O) led to the mononuclear ytterbium aryloxide LYbOAr(THF) (3). The three complexes were well detected by elemental analysis and single-crystal X-ray analysis. It was found that complexes 2 and 3 can initiate the ring-opening polymerization of ϵ-caprolactone with moderate activity.

Three new metal–nitroxide complexes {[Ni(NIT4Py)₂(obb)(H₂O)₂]·1.5H₂O}_n (1), {[Co(NIT4Py)₂(obb)(H₂O)₂]·2H₂O}_n (2), and [Co(IM4Py)₂(obb)₂(H₂O)₂][Co(IM4Py)₂(H₂O)₄]·10H₂O (3) with the V-shaped 4,4′-oxybis(benzoate) [NIT4Py = 2-(4′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, IM4Py = 2-(4′-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxide, and obb = 4, 4′-oxybis(benzoate) anion] were synthesized and structurally characterized. Single-crystal X-ray analyses indicate that complexes 1 and 2 crystallize in neutral one-dimensional (1D) zigzag chains, in which the nitroxide–metal–nitroxide units are linked by the V-shaped 4,4′-oxybis(benzoate) anions, whereas complex 3 consists of isolated mononuclear [Co(IM4Py)₂(obb)₂(H₂O)₂]^2– anions and [Co(IM4Py)₂(H₂O)₄]²⁺ ions. Magnetic measurements show that complexes 1 and 2 both exhibit weak antiferromagnetic interactions between the metal ions and the nitroxides.

The synthesis, structure, and physical properties of ionic liquids (IL) bearing the novel [Al(O–C₆H₄–CN)₄]^– ion as counterion to the commonly used [NR₄]⁺, [PR₄]⁺ and imidazolium ions are reported. Both the influence of the alkyl chain length as well as the functionalization with cyano groups is studied. These ILs are easily obtained by reaction of Ag[Al(O–C₆H₄–CN)₄] with the corresponding ammonium, phosphonium, and imidazolium halides. The stability towards electrophilic cations was investigated. All prepared salts have a window for the liquid phase of ca. 200 °C and are thermally stable up to 450 °C. The solid-state structures reveal only weak cation···anion and anion···anion interactions in accord with the observed low melting points (glass transition points).

Raman spectra of rare earth (REE: rare earth elements) trichloride (REE = Y, La, Ce, Pr, Sm, Gd, Dy, or Yb) dissolved in alkali chloride eutectic melts (LiCl-KCl, LiCl-RbCl, and LiCl-CsCl) were measured at 793 K. The spectra showed polarized peaks centered around 240–270 cm^–1, which were identified as the totally symmetric stretching vibration (ν₁) of the octahedral REECl₆^3–. The ν₁ frequency increased with the polarizing power of the trivalent REE ions. The change in the ν₁ frequency was found to be larger for lighter lanthanides. This was attributable to the distortion of the O_h symmetry of REECl₆^3–.

Formation, crystal structure, polymorphism, and transition between polymorphs are reported for M(thd)₃, (M = Al, Cr, Mn, Fe, Co, Ga, and In) [(thd)^– = anion of H(thd) = C₁₁H₂₀O₂ = 2, 2, 6, 6-tetramethylheptane-3, 5-dione]. Fresh crystal-structure data are provided for monoclinic polymorphs of Al(thd)₃, Ga(thd)₃, and In(thd)₃. Apart from adjustment of the M–O_k bond length, the structural characteristics of M(thd)₃ complexes remain essentially unaffected by change of M. Analysis of the M–O_k, O_k–C_k, and C_k–C_k distances support the notion that the M–O_k–C_k–C_k–C_k–O_k– ring forms a heterocyclic unit with σ and π contributions to the bonds. Tentative assessments according to the bond-valence or bond-order scheme suggest that the strengths of the σ bonds are approximately equal for the M–O_k, O_k–C_k, and C_k–C_k bonds, whereas the π component of the M–O_k bonds is small compared with those for the O_k–C_k, and C_k–C_k bonds. The contours of a pattern for the occurrence of M(thd)₃ polymorphs suggest that polymorphs with structures of orthorhombic or higher symmetry are favored on crystallization from the vapor phase (viz. sublimation). Monoclinic polymorphs prefer crystallization from solution at temperatures closer to ambient. Each of the M(thd)₃ complexes subject to this study exhibits three or more polymorphs (further variants are likely to emerge consequent on systematic exploration of the crystallization conditions). High-temperature powder X-ray diffraction shows that the monoclinic polymorphs convert irreversibly to the corresponding rotational disordered orthorhombic variant above some 100–150 °C (depending on M). The orthorhombic variant is in turn transformed into polymorphs of tetragonal and cubic symmetry before entering the molten state. These findings are discussed in light of the current conceptions of rotational disorder in molecular crystals.

The aluminosilicate Li₂Na₃AlSi₂O₈ was crystallized from the Li₂CO₃–H₃BO₃ flux system. It crystallizes in the orthorhombic space group Cmca, with cell dimensions a = 14.1045 (19) Å, b = 14.7054 (19) Å, c = 7.0635 (9) Å, and Z = 8. The crystal structure consists of a two-dimensional infinite layer, which is composed of [Al₂Si₂O₁₂] groups and [SiO₄] tetrahedra. The lithium and sodium atoms filling in the interlayer and intralayer link the layers together and balance the charge. IR spectroscopy and BVS calculations were used to verify the validity of the structure. The calculated band structures and the density of states of Li₂Na₃AlSi₂O₈ suggest that its direct gap is 4.28 eV.

Two new isostructural complexes, [Mn₃(L)₆(bipy)₂] (1) and [Co₃(L)₆(bipy)₂] (2) (L = 2,4-dichlorobenzoate, bipy = 2, 2′-bipyridine) were synthesized under the hydrothermal conditions and characterized by single-crystal X-ray diffraction, IR spectroscopy, EA (elemental analysis), and magnetic measurements. The two complexes are found to contain a trinuclear (M₃) unit that opens up a possibility of being magnetic materials. The magnetic measurements reveal that 1 exhibits the antiferromagnetic exchange interaction between metal ions and 2 presents a weak ferromagnetic interactions between the Co^II ions.

The branched triphosphanyltetrasilane PhSi(SiMe₂PH₂)₃ (1) could be obtained in a three-stage synthesis. It was characterised by multi-nuclear NMR spectroscopy, mass spectrometry and IR spectroscopy. Deprotonation of 1 with GaiPr₃ or [M{N(SiMe₃)₂}₂(thf)₂] (M = Ca, Sr, Ba) yields new phosphorus bridged polynuclear complexes of these metals with phosphorus atoms connected through tetrasilane fragments. While trinuclear complexes with single deprotonated phosphanyl groups could be obtained from the reactions of 1 with GaiPr₃, calcium or barium silazanide (compounds 2, 3 and 5), the tetranuclear complex [Sr₄{PhSi(SiMe₂PH)₂(SiMe₂P)}₂(dme)₆] (4) was formed in the reaction of 1 with strontium silazanide. In this compound, two of six phosphorus atoms are deprotonated twice. Compounds 2–5 were characterised by single-crystal X-ray diffraction, elemental analysis as well as IR spectroscopy and as far as possible by NMR spectroscopic techniques.

KSbWO₆ was prepared by sol-gel method. N-doped KSbWO₆ (KSbWO_6–xN_x) was obtained by heating KSbWO₆ and urea at 400 °C. Both the compounds are characterized by powder X-ray diffraction (XRD), TEM, SEM-EDS, X-ray photo electronic spectroscopy (XPS), and UV/Vis diffuse reflectance spectroscopy (UV-DRS). A shift in the peak positions of powder XRD and XPS spectra was observed. The band gap energy (E_g) of KSbWO₆ and N-doped KSbWO₆ was obtained from their diffused reflectance spectra.E_g was reduced from 3.17 eV to 2.56 eV upon nitrogen doping in KSbWO₆. The reduction of the E_g is attributed to the lifting of valence band of N-doped KSbWO₆, due to the mixing of O 2p states with N 2p states. The photocatalytic activity of both the samples was studied by degradation of methylene blue (MB). The nitrogen doped KSbWO₆ shows higher photocatalytic activity compared to that of KSbWO₆.

The intriguing multi-ligand compound [Cu(IMI)₄Cl]Cl (1) with the ligand imidazole (IMI) was synthesized and characterized by elemental analysis and FT-IR spectroscopy. The crystal structure was determined by X-ray single crystal diffraction and the crystallographic data showed that the compound belongs to the monoclinic P2₁/n space group [α = 8.847(2) Å, b = 13.210(3) Å, c = 13.870(3) Å, and β = 90.164(3)°]. Furthermore, the Cu^II ion is five-coordinated by four nitrogen atoms from four imidazole ligands and a chlorine atom. The thermal decomposition mechanism was determined based on differential scanning calorimetry (DSC) and thermogravimetric (TG-DTG) analysis. The non-isothermal kinetics parameters were calculated by the Kissinger's method and Ozawa's method, respectively. The energy of combustion, enthalpy of formation, critical temperature of thermal explosion, entropy of activation (ΔS^≠), enthalpy of activation (ΔH^≠), and free energy of activation (ΔG^≠) were measured and calculated.

The self-assembly of 1, 0-phenanthroline (phen) and 1,2,4,5-benzenetetracarboxylic acid(H₄btc) with Ca(NO₃)₂ gives rise to a two-dimensional network structure coordination polymer, [Ca(phen)(btc)_0.5(H₂O)] (1), which was characterized by elemental analysis, IR spectroscopy, and single-crystal X-ray diffraction. This compound is monoclinic, space group C2/c, with Z = 8 in a unit cell with dimensions a = 21.744(3) Å, b = 10.0151(12) Å, c = 14.7122(17) Å, β = 110.2850(10)°. The structure contains one crystallographic unique Ca^II atom, one phen coordinated molecule and a half of btc^4– anion. The phen molecule acts as a didentate ligand chelating with a Ca^II atom, whereas the btc^4– anion acts as a μ₆-bridge linking six different Ca^II atoms to form a two-dimensional network with (4, 4) topological structure. The three dimensional stacking structures are formed by C–H···O hydrogen bonding and π–π interaction. The thermal stability and fluorescent properties of 1 were investigated. Calcite particles are produced by calcination of compound 1 at 580 °C. The obtained calcite was characterized by XRD and SEM analyses.

Two new metal-organic frameworks (MOF), [(CuCN)₂·(6-mquin)₂] (1) and [Me₃SnCu(CN)₂·(quina)₂(H₂O)₂] (2) (6-mquin = 6-methyl quinolone, quina = quinaldic acid) were synthesized and characterized. Single crystals of MOF 1 were characterized by IR and NMR spectroscopy, as well as X-ray single crystal analysis. The structure of MOF 2 was studied by IR and NMR spectroscopy as well as computational studies. The structure of MOF 1 consists of 1D (CuCN)_n chains, whereas the 6-mquin ligands alternate on both sides of the chain. Hydrogen bonds play an essential role for the construction of the 3D network structure. On the other hand, the theoretical structural analysis of MOF 2 indicated that the Cu(CN)₂ fragments represent the main building blocks of the structure, which are bridged by the Me₃Sn⁺ cations to construct 1D infinite parallel zigzag chains. MOFs 1 and 2 were used as heterogeneous catalysts for the oxidative discoloration of methylene blue dye (MB) by H₂O₂.

A series of Ln–Ni heterometallic coordination polymers, {[Ln₂Ni(MIDA)₄(H₂O)₆](H₂O)₄} (Ln = La (1), Ce (2), Pr (3), and Nd (4); H₂MIDA = N-methyl-iminodiacetic acid), were obtained under hydrothermal conditions. Single crystal X-ray diffraction revealed that they feature two-dimensional isomorphic frameworks, which could be viewed as the construction by one-dimensional {Ln}_n chain connecting by bridges of [Ni(MIDA)₂]². The magnetic measurements reveal that compounds 2–4 exhibit antiferromagnetic properties. TGA results indicate compounds 1 and 4 have good thermostability with the critical temperature of 375 °C.

To investigate the effect of organic anions on coordination frameworks, the complexes [Cd(2, 6-pydc)(bibix)₂(H₂O)₂]_n (1) and {[Cd₄(2, 5-pydc)₄(bibix)₄(H₂O)₄](H₂O)₈}_n (2) were isolated by the reactions of 1-{4-[(1H-benzoimidazol-1-yl)methyl]benzyl}-1H-benzoimidazole (bibix) and two distinct pyridyl-dicarboxylates as organic anions with d¹⁰ metal salts. In the resulting structures, bibix adopts different coordination modes affected by the aromatic anions, which have distinct geometric structure and bonding modes. Thus, complex 1 has a 1D chain structure, whereas complex 2 has a 2D architecture. Both complexes 1 and 2 have a strong fluorescence emission, which may be tentatively assigned to metal-perturbed intraligand interactions.

Two zinc(II) and cadmium(II) metal-organic frameworks with mixed ligands, {[Zn₂(biim-4)₂(TDC)₂]·2.5H₂O}_n (1) and {[Cd₂(biim-4)₂(TDC)₂·2H₂O]}_n (2) [biim-4 = 1,1′-(1,4-butanediyl)bis(imidazole); H₂TDC = thiophene-2,5-dicarboxylic acid], were hydrothermally synthesized. Both of them are characterized by elemental analysis, IR spectroscopy, and single crystal X-ray diffraction. In 1, the four-connected Zn^II nodes are connected by four linear ligands extending into a 3D network, which further integrates a fivefold interpenetrating diamond 3D topological network and the free water molecules distribute in void space, whereas in 2, the Cd^II ions are in a distorted octahedral arrangement linked by TDC^2– and biim-4 ligands to construct a 3D framework. In topology analysis, C11 and C14 are simplified as 3-connected nodes and the 3D framework displays a (3,5)-connected net. Furthermore, the thermal and photoluminescent properties of 1 and 2 were also studied.

The Schiff base ligand, 1-phenyl-3-methyl-5-hydroxypyrazole-4-methylene-8′-quinolineimine, and its Cu^II, Zn^II, and Ni^II complexes were synthesized and characterized. The crystal structure of the Zn^II complex was determined by single-crystal X-ray diffraction, indicating that the metal ions and Schiff base ligand can form mononuclear six-coordination complexes with 1:1 metal-to-ligand stoichiometry at the metal ions as centers. The binding mechanism and affinity of the ligand and its metal complexes to calf thymus DNA (CT DNA) were investigated by UV/Vis spectroscopy, fluorescence titration spectroscopy, EB displacement experiments, and viscosity measurements, indicating that the free ligand and its metal complexes can bind to DNA via an intercalation mode with the binding constants at the order of magnitude of 105–106 M^–1, and the metal complexes can bind to DNA more strongly than the free ligand alone. In addition, antioxidant activities of the ligand and its metal complexes were investigated through scavenging effects for hydroxyl radical in vitro, indicating that the compounds show stronger antioxidant activities than some standard antioxidants, such as mannitol. The ligand and its metal complexes were subjected to cytotoxic tests, and experimental results indicated that the metal complexes show significant cytotoxic activity against lung cancer A 549 cells.