Influence of surface properties of the titanium dioxide porous films on the characteristics of solar cells

Porous films formed by cylindrical geometrically anisotropic fragments of TiO₂ have been produced by electrochemical anodization of titanium. The specific surface area and pore volume of the samples were determined by the BET method. It is shown that the samples have a bimodal pore-size distribution with maxima depending on the anodization voltage: by increase in voltage the inner diameter of the cylindrical pores grows, which leads to a decrease in the specific surface area. Dye sensitized solar cells were assembled on the basis of the obtained materials to study the effect of certain characteristics on the efficiency of solar energy conversion. The electrical transport properties of the films were studied by impedance spectroscopy.     

Quantum chemical studies of azoles

The results of theoretical search for model transition states of the electrophilic substitution reaction in 2H-tetrazole (1) without the preliminary formation of N-protonated azolium salts are presented for two routes that were previously suggested by the authors and thermodynamically investigated: A, the attack of molecule 1 by the nucleophile (HO^–(aq)) to form the anion to which the electrophile H₃O⁺(aq)) is added and B, the attack of molecule 1 by the same electrophile followed by the addition of the same nucleophile to the specifically solvated protonated species formed in the preceding reaction step. The calculations were performed using the DFT/B3LYP/6-31G(d) method and the scanning procedure of the potential energy surface (PES). Both steps of route A turned out to be nearly barrierless, while in route B only its first step is barrierless and the second one is conjugated with passing an activation barrier of ～45 kcal mol^–1 between non-interacting or weakly interacting reactants and electrophilic substitution products. Unlike the specifically solvated protonated species of 1H-tetrazole in an aqueous solution, a similar species of 2H-tetrazole does not form a prereaction complex with the attacking nucleophile (HO^–(aq)) and the five-membered ring is destroyed in fact in the nitrogen-containing reaction product formed after passing the activation barrier. The optimized structure of the transition state differs strongly from the nitrogen-containing structure of the reaction product with the destroyed ring, which was found by scanning of the PES.     

Asymmetric Ir-catalyzed hydrogenation of 1,5-benzodiazepinones using mixtures of ligands

The catalytic hydrogenation of benzodiazepinones using metal complexes with phosphite and phosphoramidite ligands was carried out for the first time. The mixed-ligand catalytic systems containing a chiral phosphoramidite or phosphite in combination with an achiral phosphine were shown to exhibit a higher enantioselectivity compared to catalysts containing homocombinations of chiral ligands.     

Addition of phenylacetylene and camphor to the complex [(dpp-bian)Eu(dme)<Subscript>2</Subscript>] (dpp-bian is the 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene dianion)

The reduction of 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-bian) with an excess of europium metal in 1,2-dimethoxyethane (dme) produces a divalent europium complex with the dpp-bian dianion, [(dpp-bian)Eu(dme)₂] (1). The reactions of 1 with phenyl-acetylene and camphor proceed via protonation of the diimine ligand to form the monomeric amido-amino complexes of divalent europium — [H(dpp-bian)Eu(C≡CPh)(dme)₂] (2) and [H(dpp-bian)Eu(camphor)(dme)₂] (3), respectively. Compounds 2 and 3 were characterized by IR spectroscopy and elemental analysis. Their molecular structures were determined by X-ray diffraction. Compounds 2 and 3 were shown to be monomeric seven-coordinate europium(ii) complexes with terminal phenylethynyl and enol ligands, respectively. According to the IR spectroscopic data, the terminal ligands in complexes 2 and 3 undergo tautomerization involving backward proton transfer from the amido-amino ligand to the substrate. The magnetic moment of compound 2 (8.03 μB) remains constant in the temperature range of 4—300 К and confirms the presence of divalent europium.     

Functional copolymers with triazole and acetate fragments

New functional copolymers of different composition with triazole and acetate fragments in the macromolecules were synthesized by free radical copolymerization of 1-vinyl-1,2,4-triazole with vinyl acetate. The reactivity of the comonomers was studied and the monomer copolymerization constants were calculated. The structure and composition of the copolymers were determined by elemental analysis, IR and ¹H NMR spectroscopy.     

Fe-containing nanocomposites based on a biocompatible copolymer 1-vinyl-1,2,4-triazole with <Emphasis Type="Italic">N</Emphasis>-vinylpyrrolidone

New polymer nanocomposites containing iron oxide nanoparticles stabilized with a biocompatible copolymer of 1-vinyl-1,2,4-triazole with N-vinylpyrrolidone were produced. The synthesis was conducted using the method of chemical reduction of iron ions with hydrazine hydrate in an aqueous medium in the presence of a polymer matrix. The ESR spectroscopy data showed that the core—shell type nanoparticles were obtained. The core generally consistsed of zero-valence iron coated with an oxide shell. According to the data of transmission electron microscopy, the obtained polymer nanocomposites consisted of nanoparticles of mainly spherical shape with a diameter from 1 to 14 nm. Aggregates formed from individual stabilized nanoparticles of up to 75 nm in size (in most cases) were also observed. These aggregated particles were found to self-organize and form branched chains. Nanocomposites were characterized by a different particle-size distribution, which was determined by the initial ratio of the copolymer and the precursor of iron nanoparticles.     

Synthesis of complexes of N-vinylpyrrolidone–vinylamine or N-vinylpyrrolidone–allylamine containing macrocyclic polyligand 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate (DOTA) with gallium-68 isotope and estimation of their in vivo distribution

Russian Chemical Bulletin - A method for radiolabeling the water-soluble N-vinylpyrrolidone copolymers with N-vinyl- and N-allylamine containing bifunctional chelation unit...     

Carane amino alcohols as organocatalysts in asymmetric aldol reaction of isatin with acetone

Carane-derived β-amino alcohols with amino and hydroxy groups at positions 3 and 4 differing in their mutual arrangement and configuration were synthesized. Their application as organocatalysts in the asymmetric aldol reaction of isatin with acetone allowed one to obtain adducts with up to 84% enantiomeric excess.     

Electrochemical oxidation of thrombin on carbon screen printed electrodes

The electrochemical oxidation of thrombin on the surface of carbon screen printed electrodes was studied. The electrochemical activity of thrombin was predicted, using bioinformation analysis, based on the data about the electrochemical properties of amino acids. The number of potentially electroactive amino acid residues, namely, tyrosine (Tyr), tryptophan (Trp), cysteine (Cys), histidine (His), methionine (Met), and cystine (Cys-Cys) located on the protein surface and orientated by their electroactive groups toward the electrode surface, i.e., accessible for electrochemical oxidation was calculated. The theoretical data were confirmed experimentally by cyclic and square-wave voltammetry. The available data on the protein structure allowed us to attribute the recorded electrochemical signals of thrombin oxidation to certain types of amino acid residue: the oxidation peak with a potential maximum at 0.7–0.8 V (vs. Ag/AgCl) was attributed to the oxidation of the Trp and Tyr residues; the wave in the range 1.0–1.2 V, to the oxidation of His; and the wave at 1.2–1.5 V, to the oxidation of Met and Cys-Cys. The electroanalysis based on the oxidation peak of the Tyr and Trp amino acid residues allowed to detect thrombin up to the concentration of 10^–7 M. The suggested strategy for predicting the electrochemical activity can be used for investigating the properties of many other proteins and peptides and serve as a basis for their quantitative determination when developing various sensor and biosensor devices.