35Cl NQR spectra, structure, and mutual influence of substituents in the series of chlorine-containing organic compounds of pentavalent phosphorus

Regularities of transmission of the effect of equatorial and axial substituents were established for a number of chlorine-containing organic compounds of pentatalent phosphorus using³⁵Cl NQR spectra. The field constants of³⁵Cl NQR frequencies of the chlorine atoms participating in the P−Cl bond were estimated for a series of tetrahedral phosphorus ions. The³⁵Cl NQR frequencies of chlorine atoms in tetracoordinated ions of pentavalent phosphorus and in analogous isoelectronic silicon compounds are related by a linear dependence. Deceased Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 915–922, May, 1999.     

Relationship between the 79Br NQR frequencies of crystallographically Inequivalent bromine atoms in CBr4 and their field constants

For the crystallographically Inequivalent positions of the bromine atoms in CBr₄, there exists an equation that relates the frequencies v of ⁷⁹Br NQR to their field constants α = dv/dE _z . This equation can be used to determine the strength of the local electric fields.     

On the estimation of the field constant of 35Cl nuclear quadrupole resonance frequency in the series of [R1R2R3AsCl]+M? compounds

The field constant of the NQR frequency of a chlorine atom (³⁵Cl) in a series of arsenic derivatives [R¹R²R³AsCl]⁺M⁻ was estimated from correlations. The field frequency is ∼41.5±3.5 Hz cm kV⁻¹, which is nearly twice as much as that in analogous phosphorus compounds. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1758–1760, August, 2005.     

Molecules under external electric field: On the changes in the electronic structure and validity limits of the theoretical predictions

A detailed analysis of the electronic structure of the ground and first excited spin state of three diatomic molecules ( and ) under static applied electric field is performed at CCSD(T), DFT, MRCI and MRCI(Q) levels of theory. Our findings have revealed that by boosting the applied field one induces changes in the occupation numbers of molecular orbitals, giving rise to changes in the equilibrium geometry and in the HOMO–LUMO energy gap. Specifically, singlet to triplet spin transition can be induced by increasing the applied electric field beyond a critical value. Accordingly, affecting the accuracy of the widely used expression of energy expanded in Taylor series with respect to the applied electric field. © 2018 Wiley Periodicals, Inc.     

Theoretical study of electric field‐induced intramolecular electron transfer in donor–acceptor pairs via the rigid space and their suitability as molecular electronic devices

The geometries of two reaction systems have been optimized under the constraint of C_2ν symmetry, using the UHF/6‐31G method. The potential energy surfaces (PES) of the two systems in different external electric field have been constructed using a linear reaction coordinate. It is concluded that the reorganization energies and electron transfer matrix elements for both systems are almost independent of the external electric field. However, the standard Gibbs energy difference changes remarkably with the change of the external electric field. Hence, the applied electric field leads to the variation of rate constant of electron transfer reaction. The threshold field, where the electron transfer becomes barrier free, is obtained to be 0.0015 a.u. for the anion system 1, and 0.00097 a.u. for the anion system 2. The threshold field for modified system 1, in which the hydrogen atoms linking to benzene rings are replaced by fluorine atom, is 0.0018 a.u. The calculations show that the best way to adjust the threshold field is to adjust the dipole moment of the reaction system by changing the length of the bridge. As the rate constant in field‐free case is taken into account, neither reaction systems could be used as molecular electronic device. But if the bridge consists of three or four HCTDs, the rate constant and threshold field will satisfy the practical demand. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006     

Study of charges on heteroatoms in organic compounds of the second-row elements by X-ray fluorescence spectroscopy

The characteristic features of the electronic structure of SbCl₅L complexes has been studied in comparison with those of the SnCl₄L₂ and TiCl₄L₂ complexes. The results of X-ray structural analysis were correlated with the heats of complexation, the data of Mössbauer spectroscopy, derivatography, quantum-chemical PM3 calculations, and stretching frequencies of the donor-acceptor bonds. Based on these data, the contributions of different effects to the stabilities of complexes were determined, complexation enthalpies previously unknown were calculated, and a conclusion was drawn that the electron density transfer from the donor to the acceptor is small. The charge effect of the donor consists primarily in polarization of the acceptor bonds; this polarization decreases as a result of (he change in the geometry of the acceptor upon complexation. The relative stabilities of the complexes with dimethyl sulfide were determined using a unique internal standard technique.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1465–1470, June, 1996.     

The role of mobile-phase pH in the determination of catecholamine-related compounds by reversed-phase liquid chromatography with amperometric detection

Summary A study was conducted for the optimization of the reversed-phase high performance liquid chromatographic separation of different types (acidic, basic, amphoteric and neutral) of catechol-related compounds by varying the pH. For pH to be used as the optimizing parameter, its effects on retention, peak width and peak shape had to be investigated. Therefore, the pH dependence of the amperometric detector response, as measured by the oxidation peak height or peak area, was taken into account.     

Theoretical study of electric field gradients at nitrogen nuclei in HNO,CH3NO and C2H3NO

Electric field gradients (EFGs) at the nitrogen nuclei of nitroxyl, nitrosomethane and nitrosoethylene were calculated by employing the complete-active-space self-consistent field (CASSCF), internally contracted multireference configuration interaction (icMRCI) and single-configuration coupled-cluster (CC) methods with correlation-consistent basis sets at the levels of attainable accuracy. Changes in the pσ and pπ atomic orbital populations were used to rationalize the differences between the N EFG tensor components related to the nitroso compound and separate nitric oxide. Calculated ¹⁴N nuclear quadrupole coupling constants were found in reasonable accord with experimental values. Comparison of electric dipole moments and potential energy characteristics with external values served to testify to good overall quality of the wave functions used in our calculations.     

Carbon black/alumina gel composite: Preparation by sol-gel process in the presence of polymer-grafted carbon black and its electric properties

The preparation of a novel carbon black/alumina gel composite by sol-gel reaction of aluminum isopropoxide (AIP) was investigated. When sol-gel reaction of AIP was carried out in the presence of untreated carbon black, a thin film of alumina gel was hardly obtained, because of the presence of aggregated carbon blacks. On the contrary, in the presence of poly(N-vinyl-2-pyrrolidone)-grafted, poly(2-methyl-2-oxazoline)-grafted, and poly(N,N-diethylacrylamide)-grafted carbon black, a deep-black, thin film of alumina gel, in which carbon blacks were uniformly incorporated, was obtained. Carbon black was incorporated into an alumina gel matrix by the hydrogen bond between carbonyl groups of the grafted polymer and the residual hydroxyl groups in the alumina gel. Electric resistance of the polymer-grafted carbon black/alumina gel composite was very sensitive to the vapor of solvents of the grafted polymer chains on carbon black surface: the electric resistance of the composite drastically decreased in humidity and N,N-dimethylformamide vapor, but not in n-hexane vapor. The logarithm of electric resistance of polymer-grafted carbon black/alumina gel composite linearly decreased in proportion to relative humidity. In addition, the electric resistance of poly(N,N-diethylacrylamide)-grafted carbon black/alumina gel composite under humidity decreased drastically at 32°C. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3591–3597, 1999     

Raman and infrared spectroscopic investigation of alkyl derivatives of arsenic acid: Part VI. On the AsO-bond - calculation of force constants and vibrational energy distribution in compounds of the type RAsO3X2 And R2A

Normal coordinate analyses and force constant calculations were carried out using frequencies of infrared and Raman-spectra of the molecules and ions RAsO₃^2?, RAs(O)(OR)₂, RAs(O)(OH)₂, RAs(OH)O₂^?, RzAsO₂^?, R₂As(O)OH, and [R'₂As(OH)₂]⁺ (R = CH₃, R' = C₂H₅). Comparing bond orders of the AsO bond with those in corresponding phosphorus, selenium and sulphur compounds, we found influences of the electron deficiency effect and of bond polarity.