Conformational state of benzilidene aniline derivatives from ab initio calculation and NMR spectroscopy data

Quantum chemical calculations of the structure and conformational state of a number of Shiff bases have been performed. ¹³C NMR spectra of investigated molecules were calculated and compared with experimental data to test verification of the used calculation model. The effect of terminal substituents on the conformation of azomethines and a relation between the conformation and ¹³C NMR chemical shift were examined.     

Synthesis and Properties of Tetra(4-<Emphasis Type="Italic">tert</Emphasis>-butyl-5-phenylsulfanyl)phthalocyanines and Their Derivatives

The methods of synthesis of 4-tert-butyl-5-sulfanylphenyl-and 4-tert-butyl-5-(4'-carboxyphenylsulfanyl) phthalonitriles have been developed and on their basis the corresponding octa-substituted phthalocyanines have been prepared. The effect of the structure of the above phthalocyanine derivatives on their electronic absorption spectra and parameters of thermal degradation in the presence of air oxygen were studied.     

Influence of 4-[(E)-(4′-Heptyloxyphenyl)diazenyl]phthalonitrile on the Properties of a Cyanobiphenyl Liquid Crystal Mixture

Russian Journal of General Chemistry - The mesomorphic properties of 4-[(E)-(4′-heptyloxyphenyl)diazenyl]phthalonitrile (7O-AB-CN2) were studied by polarization microscopy and DSC method....     

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.     

Dephosphorylation of pyridoxal 5′-phosphate-derived Schiff bases in the presence of bovine alkaline phosphatase

The present paper reports on the study of the dephosphorylation of pyridoxal 5′-phosphate and four derived hydrazones (containing the residues of pyrazine, 2-furan, 2-thiophene, 3-pyridine carboxylic acids) induced by bovine alkaline phosphatase from intestinal mucosa at 298.2 K and pH 10 (0.05 m Tris–HCl buffer). We observed and discussed characteristic changes in the UV–vis and fluorescent spectra of substrates. Michaelis–Menten parameters of the enzymatic dephosphorylation are calculated. The stability of alkaline phosphatase in the presence of hydrazones is confirmed. The dephosphorylation of the Zn(II) complex with pyridoxal 5′-phosphate-derived hydrazone is analyzed.     

Synthesis and Spectral Characteristics of Unsymmetrical Porphirazines with Triphrnylmethyl Groups

Condensation of 4-(p-triphenylmethylphenoxy)-1,2-dicyanobenzene with 1,2-di(methylthio)maledinitrile or 2,3-dicyano-5,6-diphenylpyrazine afforded symmetric and unsymmetrical porphirazines. The effect of their structural modification on the spectral characteristics was investigated.     

Mesomorphic and Dielectric Properties of Supramolecular 3,5-Diamino-1-dodecyl-1,2,4-triazole

The formation of a thermotropic smectic phase in 3,5-diamino-1-dodecyl-1,2,4-triazole was revealed by polarizing microscopy and DSC. Depending on heating and cooling conditions, transitions between different types of layered packings occur, which was evidenced by dielectric measurements. Quantum-chemical simulation established that the mesomorphism of 1,2,4-triazole derivatives is associated with the formation of supramolecules with a higher polarizability anisotropy. The calculation results confirmed the possibility of lateral hydrogen bonding which favors layered smectic packing.

     

Effects of nonmesomorphic substituted benzonitriles on the dielectric properties of cyanobiphenyl liquid crystals

The effects of the cyano-substituted aromatic nonmesomorphic additives N-(3,4-dicyanophenyl)-4′-nonyloxybenzamide (I), 3,4-dicyanophenyl-4′-nonyloxybenzoate (II), 3,4-dicyanophenyl-3′,4′,5′-tris-(4″-undecyloxyphenylbenzoate)benzoate (III), and 4-(6-hydroxyhexyloxy)benzonitrile (IV) on the dielectric properties of 4-hexyloxy-4′-cyanobiphenyl and a liquid-crystal mixture E3 were studied. Dielectric anisotropy, birefringence, and orientational ordering were studied to show that monocyano derivative IV most strongly increased the dielectric anisotropy of mesomorphic compositions because of its effective incorporation into the liquid crystal matrix.     

Nicotinamide solvation state in aqueous dimethyl sulfoxide

The solvation state of biologically active compound vitamin B₃, viz., 3-pyridinecarboxamide, in an aqueous-dimethyl sulfoxide solvent of a variable composition was studied by ¹H and ¹³C NMR and IR spectroscopy. Below X _DMSO ?0.65 molar fraction, the solvation of the N heteroatom due to hydrogen bonds with water molecules weakens. At X _DMSO > 0.65 molar fraction, almost no changes are observed in the solvate state of the N heteroatom. The ¹H NMR spectra indicate that the degree of conjugation of the carbamide group with the heterocycle increases with an increase in the DMSO concentration. The structures of the dimethyl sulfoxide and mixed aqueous-dimethyl sulfoxide solvates of nicotinamide were optimized by the B3LYP/6311++(DP) method, and their ¹³C chemical shifts (GIAO) and IR spectra were obtained. According to the IR spectroscopic data, the number of hydrogen bonds involving the carbamide group decreases on going from H₂O to DMSO.