Effect of Successive Meso-Phenyl Substitution on the Dissociation Kinetics of Copper(II) Octaethylporphyrin

We have synthesized complexes of copper(II) with octaethyl-, 5-phenyl octaethyl-, 5,15-diphenyl octaethyl-, and 5,10,15,20-tetraphenyl octaethylporphyrins. We have studied their dissociation kinetics in mixed solvents AcOH – H₂SO₄ at temperatures of 298 K to 343 K. We have determined the complete kinetic equations for dissociation of copper porphyrins for different compositions of the binary solvent AcOH – H₂SO₄. We provide a rational basis for electronic and steric effects on the stability of copper(II) octaethylporphyrin upon meso-phenyl substitution as a function of the degree of substitution.     

Photocatalysis of Reduction of the Dye Methylene Blue by Bi2S3/CdS Nanocomposites

We have determined the optimal conditions for synthesis of Bi₂S₃/CdS nanocomposites and we have determined their photocatalytic activity in the reaction of reduction of methylene blue as a function of composition. We suggest a possible mechanism for the photocatalytic action of the nanocomposites.     

The synthesis of symmetrical bis-1,2,5-thiadiazole ligands

We have been engaged in a search for coordination catalysts for the copolymerization of polar monomers (such as vinyl chloride and vinyl acetate) with ethylene. We have been investigating complexes of late transition metals with heterocyclic ligands. In this report we describe the synthesis of a symmetrical bis-thiadiazole. We have characterized one of the intermediates using single crystal X-ray diffraction. Several unsuccessful approaches toward 1 are also described, which shed light on some of the unique chemistry of thiadiazoles.     

Effect of Various Factors on the Reaction of 2-Aminobenzothiazoles with Propylene Oxide

We have shown that when 2-substituted 2-aminobenzothiazoles react with propylene oxide in proton-donor solvents, products of hydroxyalkylation of both the heterocycle and o-aminothiophenol formed as a result of its cleavage are synthesized. We have traced the effect of the nature of the solvent, various additives, the reaction temperature, and the heating time on this process.     

Syntheses of glycodendrimers having scyllo-inositol as the scaffold

Synthetic glycoconjugated dendrimers have emerged as important functional glycomimetics for studying multivalency effects in the cell-cell communications. We report herein, a synthetic route to functionalized glycodendrimers with scyllo-inositol as the scaffold, which have a directed geometry; one side of the dendrimers is designed for ready attachment to the AFM probe/solid matrix, and the other to have a varying number of a sugar.     

Quartz crystal microbalance determination of organophosphorus and carbamate pesticides

We have developed a quartz crystal microbalance (QCM) biosensor for the determination of organophosphorus and carbamate pesticides. A change in resonant frequency is observed as a result of mass adsorption, and we have used this as the basis for sensor development. Specifically, we have used a two-enzyme system (acetylcholine-esterase and choline oxidase) which converts acetylcholine to betaine producing hydrogen peroxide as a by-product. In a third enzyme reaction (peroxidase), the peroxide is able to oxidise benzidines (3,3′-diaminobenzidine) into an insoluble product that precipitates out and can adsorb to surfaces. Non-ionic surfactants have been used for the first time to enhance the surface deposition of suspended precipitate, thereby improving sensor sensitivity. Pesticides are known to inhibit esterase activity (thereby reducing the amount of QCM-detectable precipitate produced). We have shown that the QCM-enzyme sensor system can be used to determine carbaryl and dichlorvos down to 1 ppm.     

The expansion of hydrogen states in Gaussian orbitals

The convergence properties of Gaussian orbitals are studied by considering a very simple system, the hydrogen atom. We have variationally optimized even-tempered basis sets containing up to 60 s functions for the ground state and the first excited S state of the hydrogen atom, to an accuracy of 10^–15E_h. In addition, we have freely optimized the exponents in basis sets containing up to 12 Gaussians. We have studied the convergence of the total energy, the kinetic energy, the extent of the atom as measured by r², and the Fermi-contact interaction at the nucleus in these basis sets as well as in basis sets augmented with additional diffuse or steep functions.     

Synthesis of [N,P] ligands based on pyrrole. Application to the total synthesis of arnottin I

This paper describes the synthesis of a new class of [N,P] ligands based on pyrrole with a dimethylamino group as hard donor and a phosphine moiety as soft base. We have also modified the phosphine fragment to change the electronic and steric properties of these ligands. Palladium complex 3a proved to be very efficient in Heck cross-coupling reactions and in intramolecular aryl–aryl couplings of esters and amides. We have demonstrated the applicability and efficiency of this novel catalyst in the total synthesis of the natural product arnottin I.     

Hydrocarbon Molecular Weight Distribution and Mechanism of the Fischer — Tropsch Synthesis on Cobalt Catalysts

We have carried out a quantitative analysis of the molecular weight distribution of hydrocarbons formed at different pressures. We have shown that a change in the distribution of hydrocarbons formed at elevated pressures occurs as a result of a change in the ratio between the rates of the individual reactions with preservation of the mechanism as a whole, while the difference between the distributions obtained at high and low pressures is explained by a change in mechanism for secondary reactions.__________Translated from Teoreticheskaya i Eksperimental’naya Khimiya, Vol. 41, No. 2, pp. 115–120, March–April, 2005.     

Effect of the Nature of Organic Templates and Alkali Metal Cations on the Phase Composition and Adsorption Properties of Novel High-Silica Zeolites IPC-1 And IPC-2

We have obtained novel high-silica zeolites IPC-1 and IPC-2 and we have determined the effect of the nature and concentration of organic templates, including specially synthesized templates, and alkali metal cations as well as other factors on their phase composition and adsorption properties. We have noted that a decisive role is played by the balance between the structure-directing effects of the templates and the cations. Using temperature programmed desorption of ammonia (TPDA) and temperature- programmed cumene cracking, we have determined that strong acid sites are present in IPC-1 and IPC-2 zeolites. __________ Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 41, No. 4, pp. 236–241, July–August, 2005.     

Synthesis of organomercury compounds of the benzyl series

Conclusions We have synthesized several organomercury compounds of the benzyl series, including 2,6-dimethyl-and 2,4,6-trimethylbenzylmercurichloride, which have a steric hindrance, as well as of 2-chloromercurimethylnaphthalene.Translated from Izvestiya Akademii Nauk SSSE, Seriya Khimicheskaya, No. 6, pp. 1389–1390, June, 1969.     

Role of coupling operators on open shell RHF equations

We have derived the expressions for the extremum condition of E, corresponding to any wave function. These expressions are given as a function of the spin orbitals. We have carried out the derivation considering the spin orbitals as vectors belonging to an orthonormal basis. The corresponding variational equations have been derived introducing the condition that the norm of the wave function is constant, as the only additional constraint.From the expression obtained for the first variation of the matrix elements of H, as a function of the spin orbitals, we have derived the RHF equations for a simple case.In the present procedure, the couplings between orbitals of different shells appear directly, being defined explicitly, and they may be taken as corresponding with the elements of a Hermitian matrix.The calculations that we have carried out show that the coupling operators defined in the paper give results which are variationally correct.     

Single chain conformations in the system of symmetric and asymmetric diblock copolymers

A theory which describes a local structure and global properties of a diblock copolymer melt has been developed in the framework of the one‐loop self‐consistent approximation. We have derived expressions for the sizes of a single diblock macromolecule and its parts. Two different behaviors of single macromolecule conformations in the disordered melt have been obtained depending on the asymmetry of chains and morphologies occurring in ordered states after the order‐disorder transition (ODT). In the nearly symmetric melt, 0.35 < f ⪇ 0.5 (f is a composition), the blocks of both types shrink a little initially as the temperature decreases and then, at some temperature, they begin to swell. In strongly asymmetric melts, f < 0.35, the block of a macromolecule which consists of the monomers of minority type shrinks monotonically, while the other block monotonically swells. We have found nearly Gaussian behavior of the individual blocks and stretching near the chemical bond joining the blocks. Near the ODT the chains are stretched with a magnitude which is of the order of a few percent of their Gaussian sizes. We have calculated the peak position in the scattering curve as a function of the Flory‐Huggins interaction parameter, composition and degree of polymerization. Less then 5% change in the size of copolymer molecules lead to a 25% shift of the scattering peak in comparison to the Gaussian limit. We have found a good quantitative agreement of our theoretical results with the experimental neutron scattering data.     

Theoretical study of molecular conduction: I. Effective Green's function based on perturbation theory

There have been many experimental and theoretical studies on molecular conduction, as it is a fundamental parameter in the study of molecular‐scale electronics. We have investigated the features of molecular conduction using a Green's function method, which has often been used to solve problems in quantum transport and is also effective in elucidating electron transport in molecules. We have obtained the novel effective Green's functions, including the first‐order energy corrections, by accommodating the self‐energy of the electrodes as perturbation terms. Although these approximate Green's functions only provide information on the first‐order energy corrections, they can involve the elementary properties of molecular conduction. We propose a scheme for the analysis of the relations between molecular orbitals and their roles in molecular conduction and present analytical calculations for normal and cyclic polyenes. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006     

Pd(0)‐Catalyzed Dearomative Diarylation of Indoles

We have developed a protocol for a Pd(0)‐catalyzed dearomative syn 1,2‐diarylation of indoles using readily available boroxines (dehydrated boronic acids) as coupling partners. This reaction proceeds efficiently using PtBu₃ as the ligand to divergently access to fused indolines while minimizing the extent of direct Suzuki coupling. The scope of the reaction is remarkably broad and all products are obtained as single diastereomers in moderate to excellent yields. We have also compiled data which parallels the steric and electronic properties of both substrate and boroxine with the propensity to undergo the desired dearomative process over direct Suzuki coupling.     

Gallium‐Assisted Transfer Hydrogenation of Alkenes

We report a rare case of alkene transfer hydrogenation using a main‐group compound instead of a transition‐metal complex as catalyst. We disclosed that 1,4‐cyclohexadiene can be used as H₂ surrogate towards olefin reduction in the presence of [IPrGaCl₂][SbF₆]. Hydrogenative cyclizations have also been carried out because this cationic gallium complex is also a potent hydroarylation catalyst.     

Quantitative investigation of spatiotemporal chaos in the ferroin-catalyzed Belousov-Zhabotinskii reaction in a batch reactor

We have analyzed experimental data on the time dependence of the potentials of 16 platinum point-contact electrodes for spatiotemporal chaos in the Belousov-Zhabotinskii reaction. We show that the largest Lyapunov exponent is a convenient characteristic for spatiotemporal chaos. We found that in going from temporal to spatiotemporal chaos, the embedding dimension of the system increases by a factor of three. We have observed that as the largest Lyapunov exponent increases, we observe a decrease in the degree of spatial correlation of the process.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 31, No. 1, pp. 34–39, January–February, 1995.We would like to thank the Foundation for Basic Research of the State Science and Technology Committee of Ukraine for financial support of this work (Project 3.3/87).     

Photovoltaic performance of nanostructured zinc oxide sensitised with xanthene dyes

The photovoltaic properties of nanostructured ZnO electrodes prepared from commercially available ZnO nanoparticles (Degussa) and sensitised with xanthene dyes are explored. We have used Eosin Y, Eosin B and Mercurochrome and compared their performance to that of the more common N719 dye. We observe that these dyes efficiently sensitise commercial ZnO nanopowder and yield efficiencies that are very competitive with respect to those provided by N719. Local photocurrent and transmittance measurements as a function of the wavelength confirm the good performance of the xanthene dyes in the absorption maxima. We have prepared polymer-sealed cells and measured the short-circuit current of the devices under continuous illumination at 200 mW/cm² corresponding to twice the standard solar light intensity. The organic dyes show very good stability properties under these conditions. The combination of a versatile metal oxide such as ZnO and inexpensive organic dyes should be considered as a promising alternative in the field of dye-sensitised solar cells.