Reactivity of Rhodium(I) Complexes Bearing Nitrogen-Containing Ligands toward CH(3)I: Synthesis and Full Characterization of Neutral cis-[RhX(CO)(2)(L)] and Acetyl [RhI(μ-I)(COMe)(CO)(L)](2) Complexes

The neutral rhodium(I) square-planar complexes [RhX(CO)(2)(L)] [X = Cl (3), I (4)] bearing a nitrogen-containing ligand L [diethylamine (a), triethylamine (b), imidazole (c), 1-methylimidazole (d), pyrazole (e), 1-methylpyrazole (f), 3,5-dimethylpyrazole (g)] are straightforwardly obtained from L and [Rh(μ-X)(CO)(2)](2) [X = Cl (1), I (2)] precursors. The synthesis is extended to the diethylsulfide ligand h for 3h and 4h. According to the CO stretching frequency of 3 and 4, the ranking of the electronic density on the rhodium center follows the order b > a ≈ d > c > g > f ≈ h > e. The X-ray molecular structures of 3a, 3d-3f, 4a, and 4d-4f were determined. Results from variable-temperature (1)H and (13)C{(1)H} NMR experiments suggest a fluxional associative ligand exchange for 4c-4h and a supplementary hydrogen-exchange process in 4e and 4g. The oxidative addition reaction of CH(3)I to complexes 4c-4g affords the neutral dimeric iodo-bridged acetylrhodium(III) complexes [RhI(μ-I)(COCH(3))(CO)(L)](2) (6c-6g) in very good isolated yields, whereas 4a gives a mixture of neutral 6a and dianionic [RhI(2)(μ-I)(COCH(3))(CO)][NHMeEt(2)](2) and 4h exclusively provides the analogue dianionic complex with [SMeEt(2)](+) as the counterion. X-ray molecular structures for 6d(2) and 6e reveal that the two apical CO ligands are in mutual cis positions, as are the two apical d and e ligands, whereas isomer 6d(1) is centrosymmetric. Further reactions of 6d and 6e with CO or ligand e gave quantitatively the monomeric complexes [RhI(2)(COCH(3))(CO)(2)(d)] (7d) and [RhI(2)(COCH(3))(CO)(e)(2)] (8e), respectively, as confirmed by their X-ray structures. The initial rate of CH(3)I oxidative addition to 4 as determined by IR monitoring is dependent on the nature of the nitrogen-containing ligand. For 4a and 4h, reaction rates similar to those of the well-known rhodium anionic [RhI(2)(CO)(2)](-) species are observed and are consistent with the formation of this intermediate species through methylation of the a and h ligands. The reaction rates are reduced significantly when using imidazole and pyrazole ligands and involve the direct oxidative addition of CH(3)I to the neutral complexes 4c-4g. Complexes 4c and 4d react around 5-10 times faster than 4e-4g mainly because of electronic effects. The lowest reactivity of 4f toward CH(3)I is attributed to the steric effect of the coordinated ligand, as supported by the X-ray structure.     

Investigation of reactions postulated to occur during inhibition of ribonucleotide reductases by 2′-azido-2′-deoxynucleotides

Model 3′-azido-3′-deoxynucleosides with thiol or vicinal dithiol substituents at C2′ or C5′ were synthesized to study reactions postulated to occur during inhibition of ribonucleotide reductases by 2′-azido-2′-deoxynucleotides. Esterification of 5′-(tert-butyldiphenylsilyl)-3′-azido-3′-deoxyadenosine and 3′-azido-3′-deoxythymidine (AZT) with 2,3-S-isopropylidene-2,3-dimercaptopropanoic acid or N-Boc-S-trityl-L-cysteine and deprotection gave 3′-azido-3′-deoxy-2′-O-(2,3-dimercaptopropanoyl or cysteinyl)adenosine and the 3′-azido-3′-deoxy-5′-O-(2,3-dimercaptopropanoyl or cysteinyl)thymidine analogs. Density functional calculations predicted that intramolecular reactions between generated thiyl radicals and an azido group on such model compounds would be exothermic by 33.6–41.2 kcal/mol and have low energy barriers of 10.4–13.5 kcal/mol. Reduction of the azido group occurred to give 3′-amino-3′-deoxythymidine, which was postulated to occur with thiyl radicals generated by treatment of 3′-azido-3′-deoxy-5′-O-(2,3-dimercaptopropanoyl)thymidine with 2,2′-azobis-(2-methyl-2-propionamidine) dihydrochloride. Gamma radiolysis of N₂O-saturated aqueous solutions of AZT and cysteine produced 3′-amino-3′-deoxythymidine and thymine most likely by both radical and ionic processes.     

Highly Dispersed TiO6 Units in a Layered Double Hydroxide for Water Splitting

A family of photocatalysts for water splitting into hydrogen was prepared by distributing TiO₆ units in an MTi‐layered double hydroxide matrix (M=Ni, Zn, Mg) that displays largely enhanced photocatalytic activity with an H₂‐production rate of 31.4 μmol h^?1 as well as excellent recyclable performance. High‐angle annular dark‐field scanning transmission electron microscopy (HAADF‐STEM) mapping and XPS measurement reveal that a high dispersion of TiO₆ octahedra in the layered doubled hydroxide (LDH) matrix was obtained by the formation of an M²⁺‐O‐Ti network, rather different from the aggregation state of TiO₆ in the inorganic layered material K₂Ti₄O₉. Both transient absorption and photoluminescence spectra demonstrate that the electron–hole recombination process was significantly depressed in the Ti‐containing LDH materials relative to bulk Ti oxide, which is attributed to the abundant surface defects that serve as trapping sites for photogenerated electrons verified by positron annihilation and extended X‐ray absorption fine structure (EXAFS) techniques. In addition, a theoretical study on the basis of DFT calculations demonstrates that the electronic structure of the TiO₆ units was modified by the adjacent MO₆ octahedron by means of covalent interactions, with a much decreased bandgap of 2.1 eV, which accounts for its superior water‐splitting behavior. Therefore, the dispersion strategy for TiO₆ units within a 2D inorganic matrix can be extended to fabricate other oxide or hydroxide catalysts with greatly enhanced performance in photocatalysis and energy conversion.     

Honeycomb micropatterning of proteins on polymer films through the inverse microemulsion approach

Here we report the rapid and convenient patterning of proteins on porous polymer film using the inverse microemulsion approach. Following this method, proteins, which were dissolved in water, were transferred into dichloromethane solution of polymers through the formation of inverse microemulsion by mixing the two solutions. The protein-containing microemulsion droplets accumulated automatically into large and stable ones on the surface of organic solution casting on solid substrates, and formed tightly packed microemulsion droplet arrays driven by surface tension. With the evaporation of organic solvent and water, the microemulsion droplet arrays, which act as the template, turn to honeycomb patterned pores bearing proteins in them. The formed protein patterns can be locally applied for the detection of other proteins through specific recognition. The generality and reproducibility for the formation of BSA/PS microporous film and protein patterning by using different polymers and solvents were demonstrated by investigating surfactant addition, polymer and solvent types, and casting volume on the morphology of the microporous films. A preliminary mechanism for the protein patterning is discussed based on the analysis of the experimental results.     

CT complexes in radiation polymerisation processes including grafting, curing and hydrogel formation

Parameters influencing the grafting of a typical charge transfer (CT) complex, maleic anhydride /triethylene glycol divinyl ether, to representative substrates, cellulose and polypropylene, initiated by UV and ionising radiation have been investigated. The variables studied include effect of solvent, role of donor involving the type of ether and the nature of the acceptor including the use of common monomers like methyl methacrylate. A novel application of this CT grafting work is reported involving hydrogel formation with subsequent controlled release of incorporated reagent.     

Theoretical insights into the host–guest interactions between [6]cycloparaphenyleneacetylene and its anthracene‐containing derivative and fullerene C70

The host–guest complexes formed with [6]cycloparaphenyleneacetylene ([6]CPPA) and its anthracene‐containing derivative ([6]CPPAs) hosts and fullerene C₇₀ guest were explored by density functional calculations. Besides two previously reported configurations in which C₇₀ guest is standing or lying in the cavity of the host, we found a new kind of configuration in which C₇₀ guest is half‐lying in the cavity of the host. More interestingly, the calculated results revealed that the fine‐tuning deformations occur readily during the formations of the complexes, suggesting that both [6]CPPA and [6]CPPAs are highly elastic host molecules. The large host–guest binding energies indicate that both two host molecules, [6]CPPA and [6]CPPAs, have excellent encapsulation ability for C₇₀ guest, and the [6]CPPAs even has much better encapsulation ability for C₇₀ than [6]CPPA. Furthermore, the host–guest interactions regions were detected and visualized in real space based on the electron density and reduced density gradient. Additionally, ¹H NMR spectra of those three different kinds of configurations mentioned earlier have been calculated with gage‐independent atomic orbital method, which may be helpful for further experimental characterizations in future. Copyright © 2014 John Wiley & Sons, Ltd.     

Bilinear decompositions for the product space

In this paper, we improve a recent result by Li and Peng on products of functions in and , where is a Schrödinger operator with V satisfying an appropriate reverse Hölder inequality. More precisely, we prove that such products may be written as the sum of two continuous bilinear operators, one from into , the other one from into , where the space is the set of distributions f whose grand maximal function satisfies