Alex Kitaygorodskiy

Photoinduced inter- and intra-molecular electron transfer reactions of [60]fullerene and a tertiary amine. Formation of the cycloadduct N-ethyl-trans-2′,5′-dimethylpyrrolidino[3′,4′:1,2][60]fullerene

The photoreduction of [60]fullerene by triethylamine results in the formation of a cycloadduct N-ethyl-trans-2′, 5′-dimethylpyrrolidino[3′,4′: 1,2][60]fullerene, which is probably due to sequential intermolecular and intramolecular processes and argues strongly for the presence of ion pairs as intermediates in a room temperature toluene solution.

Fullerene-based macromolecules from photochemical reactions of [60]fullerene and triethylamine

Abstract [60]fullerene-triethylamine macromolecules are obtained from photoinduced electron transfer-proton transfer reactions. The material is characterized by photon correlation spectroscopy of quasi-elastic light scattering, matrix-assisted laser desorption ionization time-of-flight mass spectrometry, NMR and FT-IR techniques. The electronic absorption and emission properties of the material are studied. Because the macromolecules likely contain intramolecular redox pairs, the possibility of intramolecular exciplexes is examined and discussed.

Perfluoroalkyl Phosphonic and Phosphinic Acids as Proton Conductors for Anhydrous Proton‐Exchange Membranes

A study of proton-transport rates and mechanisms under anhydrous conditions using a series of acid model compounds, analogous to comb-branch perfluorinated ionomers functionalized with phosphonic, phosphinic, sulfonic, and carboxylic acid protogenic groups, is reported. Model compounds are characterized with respect to proton conductivity, viscosity, proton, and anion (conjugate base) self-diffusion coefficients, and Hammett acidity. The highest conductivities, and also the highest viscosities, are observed for the phosphonic and phosphinic acid model compounds. Arrhenius analysis of conductivity and viscosity for these two acids reveals much lower activation energies for ion transport than for viscous flow. Additionally, the proton self-diffusion coefficients are much higher than the conjugate-base self-diffusion coefficients for these two acids. Taken together, these data suggest that anhydrous proton transport in the phosphonic and phosphinic acid model compounds occurs primarily by a structure-diffusion, hopping-based mechanism rather than a vehicle mechanism. Further analysis of ionic conductivity and ion self-diffusion rates by using the Nernst-Einstein equation reveals that the phosphonic and phosphinic acid model compounds are relatively highly dissociated even under anhydrous conditions. In contrast, sulfonic and carboxylic acid-based systems exhibit relatively low degrees of dissociation under anhydrous conditions. These findings suggest that fluoroalkyl phosphonic and phosphinic acids are good candidates for further development as anhydrous, high-temperature proton conductors.

First separation and characterization of cis and trans 1,2-bisaryloxy perfluorocyclobutanes

Abstract 4-Bromotrifluorovinyloxybenzene (4-Br-TFVE) undergoes cyclodimerization upon heating at 150xa0°C affording cis and trans isomers of 1,2-bis(4-bromophenoxy)hexafluorocylcobutane. Stereoisomers were separated by selective crystallization, confirmed by single crystal X-ray, and further characterized by NMR. Remarkable difference in the solid state structures include aryl to aryl dihedral angles of 12° for the trans isomer and 88° for the cis isomer. Polymers containing roughly equal amounts of cis and trans fused perfluorocyclobutyl (PFCB) rings should be expected to have low crystallinity due to the marked difference in the two unit cells as is observed.

Oxidations by the reagent "O2–H2O2–vanadium derivative–pyrazine-2-carboxylic acid". Part 12.1 Main features, kinetics and mechanism of alkane hydroperoxidation

Various combinations of vanadium derivatives (n-Bu4NVO3 is the best catalyst) with pyrazine-2-carboxylic acid (PCA) catalyse the oxidation of saturated hydrocarbons, RH, with hydrogen peroxide and air in acetonitrile solution to produce, at temperatures <40xa0°C, alkyl hydroperoxides, ROOH, as the main primary products. These compounds are easily reduced with triphenylphosphine to the corresponding alcohols, which can then be quantitatively determined by GLC. Certain aminoacids similar to PCA can play the role of co-catalyst; however the oxidation rates and final product yields are lower for picolinic and imidazole-4,5-dicarboxylic acids, while imidazole-4-carboxylic and pyrazole-3,5-dicarboxylic acids are almost inactive. The oxidation is induced by the attack of a hydroxyl radical on the alkane, RH, to produce alkyl radicals, R˙. The latter further react rapidly with molecular atmospheric oxygen. The peroxyl radicals, ROO˙, thus formed can be converted to alkyl hydroperoxides. We conclude on the basis of our kinetic investigation of the oxidation of cyclohexane that the rate-limiting step of the reaction is the monomolecular decomposition of the complex containing one coordinated PCA molecule: VV(PCA)(H2O2)xa0→xa0VIV(PCA)xa0+xa0HOO˙xa0+xa0H+. The VIV species thus formed reacts further with a second H2O2 molecule to generate the hydroxyl radical according to the equation VIV(PCA)xa0+xa0H2O2xa0→xa0VV(PCA)xa0+xa0HO˙xa0+xa0HO−. The concentration of the active species in the course of the catalytic process has been estimated to be as low as [V(PCA)H2O2]xa0≊xa03.3xa0×xa010−6 mol dm−3. The effective rate constant for the cyclohexane oxidation (d[ROOH]/dtxa0=xa0keff[H2O2]0[V]0) is keffxa0=xa00.44 dm3 mol−1 s−1 at 40xa0°C, the effective activation energy is 17xa0±xa02 kcal mol−1. It is assumed that the accelerating role of PCA is due to its facilitating the proton transfer between the oxo and hydroxy ligands of the vanadium complex on the one hand and molecules of hydrogen peroxide and water on the other hand. For example: (pca)(O)V⋯H2O2xa0→xa0(pca)(HO–)V–OOH. Such a “robot’s arm mechanism” has analogies in enzyme catalysis.

Effect of perfluoroalkyl chain length on proton conduction in fluoroalkylated phosphonic, phosphinic, and sulfonic acids.

The effects of increasing perfluoroalkyl chain length on the molecular properties of viscosity, diffusivity, and ionic conductivity of a series of acid model compounds analogous to comb-branch perfluorinated ionomers functionalized with phosphonic, phosphinic, and sulfonic protogenic groups are reported. Anhydrous proton transport by a Grotthuss-like hopping mechanism was observed to occur efficiently in phosphorus-based fluoroalkylated model acids but only when there is a relatively low perfluoroalkyl content. The decrease in degree of dissociation of the protogenic groups follows the order phosphonic > phosphinic > sulfonic, and the degree of dissociation and the magnitude of ion-ion correlations are approximately independent of chain length.

Novel O-glycosidic gossypol isomers and their bioactivities.

Novel glycosidic gossypol analogs, 7,7-gossypol diglucoside tetraacetate GS1, 6,7-gossypol diglucoside tetraacetate GS2, 7,7-gossypol diglycoside GS1, 6,7-gossypol diglycoside GS2 were obtained by the ultrasound-assisted reaction of the potassium salt of gossypol with 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide under PTC conditions and were fully characterized by 1D NMR ((1)H NMR, (13)C NMR, DEPT, 1D NOE), 2D NMR (HMBC, HMQC), FTIR, HRMS and HPLC. The anticancer activities, cytotoxic effects as well as anti-trypanosomal activities of these novel glycosidic gossypols were explored and suggest that gossypol glycosides could be used to develop new candidates for anticancer drugs and anti-trypanosomal agents.