Intermolecular interactions in the liquid crystal-fullerene C70 system

The formation of complexes in the fullerene C₇₀-toluene-liquid crystal system is investigated. The precision study of spectral manifestations of the intermolecular interaction in this system is performed for two low-frequency absorption bands of C₇₀. These manifestations are found to be specific for each of the bands analyzed.     

Laboratory Physical Simulation of Acoustic Wave Propagation on the Shelf

Acoustical Physics - In laboratory conditions, the vertical structure of short mode pulses was studied near the critical thicknesses of hydroacoustic waveguides of constant and variable depth with...     

DFT study of substitution effect on the geometry, IR spectra, spin state and energetic stability of the ferrocenes and their pentaphospholyl analogues

Optimal structures, vibrational spectra and thermochemical characteristics of ferrocenes and pentaphosphaferrocenes containing up to five methyl substituents in the cyclopentadienyl ring are found with the use of DFT computations. It is shown that the non-substituted ferrocenes and pentaphosphaferrocenes as well as the species with small number of methyl substituents adopt eclipsed conformations. Increasing the number of the methyl substituents results either in the conformational equilibria between the eclipsed and staggered forms or in complete shift to the staggered conformations. These effects, as well as elongation of CC bonds of the Cp ring and growth of Fe-Cp and Cp-P₅ distances with growing number of methyl groups can be explained by repulsive interactions of the methyl groups with each other or with phosphorus atoms of the pentaphospholyl ligands. The pentaphosphaferrocenes are predicted to be stable towards disproportionation to homoleptic sandwich complexes. This stability grows as the number of methyl substituents in cyclopentadienyl ring increases, which is a result of stronger Fe-P₅ bonding in the methyl substituted pentaphosphaferrocenes relative to the non-substituted species, and destabilization of the homoleptic ferrocenes because of Me?Me repulsion. A huge energy gap between the low- and high-spin states of the ferrocenes and pentaphosphoferrocenes is predicted, though introduction of methyl substituents causes a moderate decrease of the gap. Transition from low- to high-spin state should result in pronounced changes of geometry and IR spectra of the ferrocenes, which suggests that IR spectroscopy can be used for diagnostics of spin state of iron complexes.     

Nonlinear luminescence of high-concentration rhodamine solutions: On the problem of pulsed laser cooling

The conditions of occurrence of collective photoinduced luminescence in model solutions are determined. The transmittance and luminescence of concentrated solutions of rhodamine 101 under excitation by laser pulses in the Stokes and anti-Stokes spectral ranges are studied. It is shown that, at high pump energies, collective photoinduced luminescence, which competes with induced radiation, plays a significant role in luminescence generation. Temperatures of heating and cooling of solutions are estimated. The photodynamics of cooling of solutions of complex molecules under their pulsed (Stokes and anti-Stokes) excitation is analyzed.     

Electrocatalytic fluoroalkylation of olefins. Nickel-catalyzed polyfluoroalkylation of allylisocyanurates

Electrochemical co-reduction of allylisocyanurates and polyfluoroalkyl halides in the presence of nickel complexes with α-diimine ligands results in the addition of the polyfluoroalkyl group to the C=C bond followed by dimerization of the intermediate adducts.     

Electrochemistry of nitronyl and imino nitroxides

Redox potentials of a wide group of azolyl-substituted nitronyl and imino nitroxides were determined by classic cyclic voltammetry (CV). Conclusions have been made for this group of compounds, and their peculiarities were emphasized in comparison with methyl-, phenyl-, iodo-, and cyano-substituted nitroxides.     

Electrochemical nickel-induced fluoroalkylation: synthetic, structural and mechanistic study

Electrocatalytic generation of nickel catalysts in low oxidation states by reduction of nickel complexes with various ligands (2,2'-bipyridine, 2,2':6',2'-terpyridine, (S,S)-2,6-bis(4-phenyl-2-oxazolin-2-yl)-pyridine) in the presence of olefinic substrates and fluoroalkyl halides leads to new organic products derived from addition-dimerization processes. Due to the presence of two stereocenters in the dimerization products two diastereomers were characterized by a variety of analytical techniques including multi-dimensional NMR methods and X-ray single crystal diffraction. The formation of dimers was prevented by the inclusion of the hydrogen atom donor tributyltin hydride. The cyclic voltammetry study of selected nickel complexes along with fluoroalkyl halides demonstrated that Ni(I)L is the active form of the catalyst.     

Structure of the tetrakis(benzoylacetonate) compound of europium used to obtain the laser effect

The spatial symmetry group of unit cells of diethylammonium and plperidinium europium tetrakis(benzoylactonate) B₄EuHD and B₄EuHP, and also the structure of the B₄Eu^– anion in B₄EuHD, which belongs to the C₂ symmetry group and exists as the cis, cis, cis isomer, have been determined. On the basis of an analysis of the luminescence spectra and structure of the B₄Eu^– anion it has been shown that the splitting of the levels of the ground state of the europium ion formally corresponds to C₂ symmetry, but may be determined by the C₄ symmetry of the immediate oxygen environment of europium EuO₈. Both complexes give a stable laser effect at a wavelength of 613 nm, corresponding to the transition from the ⁵D₀ level to the x- or y-component of the ⁷F₂ level, split by a crystal field with C₂ or C₄ symmetry.