Chemistry – An Asian Journal

Two BODIPY dyes with increasingly rigid conformations were synthesized from the conformationally unconstrained 3,5-di-(2-bromophenoxy)-4,4-difluoro-8-(4-methylphenyl)-4-bora-3a,4a-diaza-s-indacene through palladium-catalyzed intramolecular benzofuran formation. In their Full Paper on page 2016 ff., W. Qin, W. Dehaen et al. report how restricted bond rotation of the phenoxy fragments led to more-intense absorption and fluorescence signals at longer wavelengths relative to the unconstrained dye. X-ray diffraction analysis showed progressively more-extended planarity of the chromophore with increasing conformational restriction. These conclusions were confirmed by quantum chemical calculations of the lowest electronic excitations.

The magical nanopore: This Focus Review highlights the technical details of biological nanopores, especially α-hemolysin, in the detection of peptides or proteins from the technique point of view. The set-up, interference, and data analysis of biological nanopores by different methods are discussed briefly.

Model complex: An Fe^II complex bearing a thiolate, 2-methoxy-pyridine, and three facially arranged CO ligands was synthesized as a structural analogue of the active site of a CO-inhibited form of [Fe] hydrogenase, from the reaction of [FeBr₂(CO)₄] with NaS{2,6-(mesityl)₂C₆H₃} and the successive treatment with 2-methoxy-pyridine.

There′s just NO SNAP! Ru^III complexes of macrocyclic tertiary amines, especially trans-[Ru(14-TMC)Cl₂]Cl (1), could mediate nitric oxide (NO) release from S-nitrosothiols in the presence of biological reductants. Interestingly, complex 1 was found to enhance rat aorta relaxation in the presence of S-nitroso-N-acetylpenicillamine (SNAP) under in vivo conditions.

Green epoxides! A novel and simple ionic liquid/manganese acetate catalytic system has been developed for the rapid and selective oxidation of aliphatic terminal alkenes to epoxides. It provides an efficient, reusable, and scalable protocol for the green synthesis of epoxides from various aliphatic terminal alkenes.

Ba Ba black sheep: We have developed novel barium/binol catalysts prepared from alkaline earth metal amides and chiral binaphthol ligands. These catalysts effectively promoted the asymmetric Friedel–Crafts–type alkylation reactions of indoles with chalcone derivatives. This is the first example of asymmetric Friedel–Crafts–type alkylation reactions using chiral Brønsted bases.

Keep it clean! The extraordinary antibacterial property of mesoporous titania films is discovered. The inactivation effect of bacteria is determined by several significant factors such as surface area, titania phase, anatase crystallinity, and surface morphology, which can be controlled by the applied calcination temperatures.

Layered tubes: The giant nanoporous molybdenum-oxide based polyoxometalates of the wheel and Keplerate type with unique features, which can be considered as the basis of a new type of nanochemistry and nanomaterials science and find a variety of applications, can be easily incorporated into nanotubular arrays with well defined wall thickness and aperture.

I hope you like bamim too: Anthracene derivatives attached to functionalized single-walled carbon nanotubes through Coulombic interactions undergo a partial (and reversible) photodimerization process upon irradiation with UV light of appropriate wavelengths.

A coat with arms! A fast and efficient approach to terminal-functionalized linear polyglycerols for subsequent surface modification is described. The resulting biocompatibility of the functionalized surfaces in comparison to a PEG-functionalized surface is demonstrated by protein adsorption and cell-adhesion testing.

Making hybrids: Mesoporous hybrid materials containing covalently grafted phenothiazines have been synthesized by the direct condensation of TEOS and appropriate silicon derivatives. Upon oxidation with (NO)BF₄ or SbCl₅, stable phenothiazine radical cations are generated in the pores of the materials, which can be detected by means of UV/Vis, emission, and EPR spectroscopies. The electron transfer into and out of these materials has been investigated by cyclic voltammetry.

To close to color: A sequence of nucleophilic aromatic substitution and palladium catalyzed ring formation yields conformationally restricted BODIPY dyes with large red shifts of the absorption and emission spectra (see figure).

Sizzling silylation! Simple zinc complexes generated in situ catalyze the hydrosilylation of aliphatic and aromatic ketones with silanes as the hydride source with excellent turnover frequencies (>999 h⁻¹) and broad group tolerance.

Sensitivity issue: Emission from dipyrrin complexes displays a remarkable sensitivity on the structure of the 5-aryl substituent. The first resonance Raman study of a novel nonemissive heteroleptic ruthenium(II) dipyrrin species demonstrates that this sensitivity arises from the large scale torsional motion of the phenyl substituent in the Frank–Condon region. DFT calculations reveal the origin of these dynamics in the delocalization of charge onto the phenyl ring.

Go organic! Organocatalytic alkylation of aldehydes is realized with relatively stable isolated carbocations (see scheme; TFA=trifluoroacetic acid). Moderate to good enantioselectivities (up to 92 % ee) are observed. Reaction with stereogenic carbocation (flavilium fluoroborate) shows a moderate diastereoselectivity (up to 9:1).

Following fireflies: We systematically synthesized novel bioluminogenic substrates bearing an amino group on benzothiazole, quinoline, naphthalene, and coumarin scaffolds. They emitted bioluminescence in various colors. The coumarylluciferin derivative was applied as an energy donor substrate for a bioluminescence resonance energy transfer system system utilizing firefly luciferin–luciferase reaction with yellow fluorescent protein.

The power of powder! Powder X-ray diffraction was used to characterize intractable polymeric solids, chain-like metal coordination polymers with tuneable optical band gaps perturbed by d⁸ transition metal(II) ions and Group 6 donor atoms.

Show me the way: The analogies and differences in the solvent-dependent fluorescence and E–Z isomerization quantum yields between the N-arylamino-derived fluorescent protein chromophores and trans-aminostilbenes reveal the relative efficiencies of the three nonradiative decay pathways, the τ and ω torsions, and hydrogen-bonding-induced internal conversion (see scheme).

Gaining control: Thermal stability and oxidizing reactivity of nickel(II)–alkylperoxo species can be controlled by tuning the electronic property of the ligand without changing the coordination structure. Thermal stability of the brominated ligand complex is higher than that of the prototype non-brominated ligand complex.

See deep blue: Two new bipolar compounds that combine triphenylamine and benzimidazole moieties have been synthesized and characterized. The results reveal that the bipolar compound 1 can be a potential multifunctional material as both deep-blue emitter and host for the phosphorescent dopant in organic light-emitting diodes (OLEDs; see image).

Framing polymers: A new model of polymer mobility restriction using mesoporous silica with a large pore space is proposed. The mesopores are easily penetrated by polymer chains owing to the capillary force during mechanical composite processing. The robust inorganic frameworks covering the polymer effectively restrict polymer mobility against thermal energy, which should contribute to low thermal expansion properties.

Prim and proper: The combined magnetic anisotropic effects generated by two auxiliary moieties of 2-methoxy-2-phenylacetic acid (MPA) allows the establishment of a methodology for the determination of the absolute configuration of terminal prim/sec and sec/prim 1,2-amino alcohols (see image).

From lactone to lactam: The synthesis of azalamellarins (see scheme), a new series of lactam analogue of biologically active lamellarins, was studied using Cu^I-mediated, microwave-assisted CN_amide bond formation. Seventeen azalamellarins were synthesized and evaluated for their cytotoxicity against a panel of four human tumor cell lines.