Synthesis, structure, and spectral luminescent properties of novel 1,2,4-triazole derivatives containing benzthiazole group

Novel derivatives of 1,2,4-triazol with benzthiazole fragment have been prepared, including Cu(II) and Be complexes. Their structure and spectral luminescent properties have been investigated. With ohydroxyphenylbenzthiazolyl-1,2,4-triazole as an example, the density functional theory has been applied to find the stable conformers with different structures of coordination nodes, stabilized by intramolecular hydrogen bonds between hydroxyl group hydrogen and either triazole of benzthiazole nitrogen.     

Structure and Tautomerism of Cyclopentadiene Derivatives: IX. Synthesis and Structure of Substituted N-Cyclopentadienyl Amidinium Ylides

A procedure has been developed for the synthesis of N-cyclopentadienyl amidinium ylides of the general formula C₅(CO₂Me)₄[ArNC(Ar')NHAr]. According to the X-ray diffraction data, ¹H and ¹³C NMR spectroscopy, and MNDO quantum-chemical calculations, the title compounds have a zwitterionic structure with the positive charge localized over the amidine NÄCÄN triad, and the negative charge, over the cyclopentadiene fragment. The configuration of the amidine moiety is stabilized by additional interaction of the NH hydrogen atom with the negatively charged cyclopentadiene ring (-bonding). The ylides are chiral due to atropoisomerism arising from a high energy barrier (G 298 >25 kcal/mol) to rotation of the Ar' substituent about the ordinary CÄC bond in the amidinium fragment.     

Sigmatropic hydrogen shifts in aryltetraphenylcyclopentadienes

Dynamic NMR has revealed intramolecular migrations of hydrogen atom over the periphery of the five-membered ring in 5-(p-tolyl)-1,2,3,4-tetraphenylcyclopentadiene in a deuteronitrobenzene solution with energy barrier ΔG ₁₈₀ ^≠ = 24.8 kcal/mol. Quantum-chemical DFT calculations B3LYP/6-311++G** have shown that such migrations in 1,2,3,4,5-pentaphenylcyclopentadiene in the gas phase occur in a chiral conformation of propeller type by the mechanism of 1,5-sigmatropic hydrogen shifts with retention of configuration through asymmetric transition state with energy barrier ΔE _ZPE ^≠ = 25.9 kcal/mol. Enantiomers P and M can readily interconvert into each other (ΔE _ZPE ^≠ = 3.9 kcal/mol) owing to synchronous flip rotations of the phenyl groups.     

Structural and stereochemical nonrigidity of 7-(heptaphenylcycloheptatrienyl) isothiocyanate

By means of DFT B3LYP/6-31G(d, p) calculations of 7-(heptaphenylcycloheptatrienyl) isothiocyanate, the dissociation–recombination mechanism for intramolecular migrations of the isothiocyanato group has been revealed, and the structure of the transition state preceding the formation of a tight ion pair has been found for the first time. According to calculations, the high activation barrier for displacements of the isothiocyanato group ΔE_ZPE^≠ = 21.3 kcal/mol is related to the stable conformation of the molecule with the equatorial–NCS group and the orthogonally located phenyl substituent in the axial position. The rearrangement of the molecule to the form favorable for migrations of the–NCS group involves the inversion of the seven-membered ring accompanied by rotation of the phenyl group.     

Spectral Luminescent Properties of 3-[5-(4-Methoxyphenyl)-1,3,4-oxadiazol-2-yl]acrylic Acid and Its Complex with Zn(II)

Russian Journal of General Chemistry - Zinc complex of (E)-3-[5-(4-methoxyphenyl)-1,3,4-oxadiazol-2-yl]acrylic acid has been prepared; its structure and composition have been elucidated by means of...     

Redox Processes in Amidinylcyclopentadiene Compounds and Thallium Complexes

Cyclic voltammetry at platinum and dropping mercury electrodes in acetonitrile suggests that the reduction of amidinylcyclopentadiene ligands involves generation of corresponding radical anions and the oxidation, radical cations, whereas the reduction of thallium complexes occurs through the deposition of the free metal (the process is affected by the complexing agent) and their oxidation leads to the ligand oxidation (the process is affected by the metal ions). Given cyclic voltammetric data on model compounds of rigid structure in solutions, amidinylcyclopentadiene ligands and thallium complexes exist in acetonitrile in a nondissociated covalent form with a bidentate metal (hydrogen) coordination with the complexing agent.     

Spectral and luminescent properties of 2-(2-hydroxyphenyl)-5-(2,6-difluorophenyl)-1,3,4-oxadiazole and its methoxy and benzyloxy derivatives

Russian Journal of General Chemistry -     

Features in constructing a certificate of strength of extraterrestrial material by the example of the Chelyabinsk meteorite

The mechanical properties of various components of the Chelyabinsk meteorite are studied. A measurement technique allowing one to obtain a strength certificate of the material by a minimum necessary number of samples with allowance for defectiveness is developed. Universal expressions for the chondritic component and impact melting have been obtained. The expressions allow one to make general estimates of the strength boundaries for LL type meteorites.