Olga D. Fominykh

Redox trends in cyclometalated palladium( ii ) complexes

A series of diverse binuclear and mononuclear cyclometalated palladium(ii) complexes of different structure was investigated by electrochemical techniques combined with density functional theory (DFT) calculations. The studies including cyclic and differential pulse voltammetry, X-ray structure analysis and quantum chemical calculations revealed a regularity of the complexes oxidation potential on the metal-metal distance in the complexes: the larger Pd-Pd distance, the higher oxidation potentials. The reduction potentials feature unusually high negative values while no correlation depending on the structure could be observed. These results are in a good agreement with the electron density distribution in the complexes. Additionally, ESR data obtained for the complexes upon oxidation is reported.

Ab initio calculation of 14N and 35Cl nuclear quadrupole coupling constants in aziridine and Cl-aziridine

Abstract Ab initio calculations of electric field gradients (EFG) at 14 N and 35 Cl nuclei and conversion to the corresponding nuclear quadrupole coupling constants are reported for aziridine and Cl-aziridine molecules. The structural parameters for Cl-aziridine used for these calculations are obtained as a result of gradient optimization at the HF/4–31G ∗ level. The mutual orientation of the molecular axes and principal axes of the EFG tensor is presented. To evaluate the main contribution from various bonds and lone pairs to the EFG tensor components, a localized molecular orbital (LMO) analysis is made. The comparison of the results of the calculation with experiment is discussed.

Nonempirical calculations of NQR parameters in some three-membered rings

Abstract Ab initio calculations (RHF/6–31G∗) of the electric field gradients (EFGs) at 14N,17O, 2H and 33S and the corresponding nuclear quadrupole coupling constants (NQCCs) are reported for a number of three-membered rings containing atoms of the first and the second rows. The results of the calculations are in good agreement with the available experimental data. The orientations of the principal axes of the EFG tensor at the quadrupole nuclei are determined. The origin of the EFG is analyzed within the framework of the LMO approach. To compare the charge density distributions in aziridine and Cl-aziridine, the charge density maps are obtained using the canonical molecular orbitals.

Nonempirical calculations of NQR spectrum parameters of azetidine

The components of the14N electric field gradient (EFG) tensor, the corresponding nuclear quadrupole coupling constant (NQCC) χ, and the asymmetry parameter η of azetidine were calculated using the restricted Hartree-Foek-Roothaan method, The geometry of azetidine was optimized with the 4–31G basis set, and the values of the ring puckering angle (θ) and the angle between the N-H bond and the CNC plane (β) were refined with the 6–31G* basis set. The effect of choice of geometry on calculated NQR parameters was studied. To clarify the origin of EFG at the nitrogen atom nucleus, the contributions from individual bond orbitals and lone electron pairs to the EFG tensor componentseqii were calculated in the framework of the LMO approach. It was demonstrated that the 4-31G + 6–31G*//6–31G* level calculations give NQCC and η values of azetidine that are in good agreement with the results of MW spectroscopy.