V. V. Aleksandriiskii

Mesomorphic and dielectric properties of the systems based on nematic cyanobiphenyls

Nematic cyanobiphenyls have been modified with small amount of polar additives. Phase transition temperatures as a function of composition of the prepared mixtures have been determined by polarization thermomicrscopy. The dielectric constant as a function of temperature has been determined via dielcometry measurements, and the dielectric anisotropy of the studied mixtures has been revealed. Broadening of the mesophase existence temperature range and enhancement of the dielectric anisotropy of the nematic biphenyls upon addition of polar dopants results from the supramolecular self-assembly via hydrogen bonding.

Mesogenic 4-alkoxy-2-hydroxy-4’-formylazobenzenes

Homologous 4-alkoxy-2-hydroxy-4’-formylazobenzenes (Alk = C3H7, C6H11, C8H17) were synthesized and were shown to produce monotropic nematic liquid crystalline phase. The products were characterized by electron absorption and 1H and 13C NMR spectra. The effect of lateral hydroxy group on their mesomorphic properties was analyzed.

Structure of pyridoxine solvates in aqueous solution from quantum-chemical calculations and NMR spectroscopy

A geometric optimization is performed for the neutral, zwitterionic, and protonated forms of pyridoxine in vacuum and in water with a solvent within the polarizable continuum model (PCM). The structural parameters are optimized for pyridoxine complexes in the neutral and zwitterionic forms with 4-10 water molecules. An analysis is performed of how the number of molecules of the solvent set by the model affects the agreement between the calculated and experimental NMR spectra.

Optically active 4-(4-{4-[(2S)-(2-methylbutoxy)]benzoyloxy}-phenyldiazenyl)benzaldehyde

Abstract4-(4-{4-[(2S)-(2-methylbutoxy)]benzoyloxy}phenyldiazenyl)benzaldehyde was synthesized and its structure was identified.

Mesogenic 4-acryloyloxy- and 4-(2,3-epoxypropoxy)phenyl 4-alkoxybenzoates

Procedures were developed which made it possible to synthesize in good yields homologs of 4-acryloyloxyphenyl 4-alkoxybenzoates (C3, C5, C7, C8) and of 4-(2,3-epoxypropoxy)phenyl 4-alkoxybenzoates (C5, C7). The substituted phenylbenzoates obtained exhibit the enantiotropic nematic mesomorphism in a sufficiently wide temperature range. The studied compounds have absorption maxima in the near UV region and a high temperature of decomposition beginning.

Complexation between nickel(II), cobalt(III) and hydrazones derived from pyridoxal 5’-phosphate and hydrazides of 2-,3-,4-pyridinecarboxylic acids in aqueous solution

abstract The present work reports on stoichiometry, apparent stability constants of biologically relevant complexes of nickel(II), cobalt(III) with hydrazones derived from pyridoxal 5′-phosphate and hydrazides of 2-,3-,4-pyridinecarboxylic acids at pH 7.4, T = 25.0 °C, I = 0.25 determined using UV-Vis spectroscopy. The thermodynamic constants of some complexes formation (NiL, NiL2, NiL2H) were estimated. Cobalt(II) ion was found to be oxidized to cobalt(III). Co(II) and Co(III) form low-spin state complexes. Hydrazones binding ability (pL0.5) in the medium mimicking biological ones towards Ni(II) and Co(III) was estimated. Graphical abstract

The Schiff bases of pyridoxal-5-phosphate and hydrazides of certain pyrazoles: Stability, kinetics of formation, and synthesis

The interaction of pyridoxal-5-phosphate with 3-methyl-1Н-pyrazole-5-carbohydrazide, 2-(3,5-dimethyl-1Н-pyrazol-4-yl)acetohydrazide, and 1Н-pyrazole-3-carbohydrazide has yielded Schiff bases; the products have been characterized by 1Н NMR and IR spectra. The binding ability of these pyrazoles with respect to pyridoxal-5-phosphate under conditions modeling the living tissues has been evaluated. Rate constants of the formation of the Schiff bases have been determined.

Synthesis, mesomorphic and dielectric properties of 4-(cyanomethoxy)phenyl 4-alkoxybenzoates, 4-(cyanomethoxy)-4′-alkoxyazo- and -azoxybenzenes

Preparation methods were developed for homologs of 4-(cyanomethoxy)phenyl 4-alkoxybenzoates (C7, C8, C9), 4-(cyanomethoxy)-4′-alkoxyazo (C2, C3, C6), -azoxybenzenes (C3, C6) whose composition and structure were proved by elemental analysis and 1H NMR spectra. 4-(Cyanomethoxy) group destabilizes the mesophase, consequently, only four among the compounds obtained exhibit the thermotropic nematic mesomorphism.