π-Electron ring currents and magnetic shielding in oxygen-containing unsaturated heterosystems

A procedure developed previously for the calculation of molecular magnetic characteristics has been applied to calculations of diamagnetic susceptibilities and the chemical shifts of protons and ¹³C nuclei of oxygen-containing heterocycles. The results are in accord with experimental data. The distributions of current that are used as the basis for such calculations are discussed, and a scale of aromaticity is given for the systems that have been investigated.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 3, pp. 293–302, May–June, 1985.     

Quantum-chemical interpretation of recyclization reactions. 10. Photoisomerization of six-membered heterocycles

Singlet photoisomerizations of a number of six-membered heterocycles have been described on the basis of the index approach in the framework of the coupled variant of perturbation theory for a one-electron transition density matrix in the Pariser-Parr-Pople method.For Communication 9, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 357–363, March, 1986.     

Pairing theorem and magnetic shielding of cations and anions of odd alternant hydrocarbons

A previously developed scheme for describing the diamagnetic characteristics of molecules with conjugated bonds has been generalized to the case of noncoplanar systems, and the¹H and¹³C chemical shifts of the benzyl, diphenylmethyl, triphenylmethyl, and - and -naphthyl anions and cations have been calculated on its basis and compared with experiment. It has been shown that the current contributions to the magnetic shielding for the anions and cations of odd alternant hydrocarbons of identical structure and charge multiplicity are equal to one another, while the charge contributions differ in sign. This has made it possible to find the experimental charge distribution of the cations investigated and to compare it with the results of quantum-chemical calculations.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 3, pp. 277–283, May–June, 1989.     

Quantum-chemical treatment of recyclization reactions. 9. Photoisomerization of five-membered heterocycles

The photoisomerization of a number of five-membered heterocycles has been considered in the framework of the coupled variant of perturbation theory for a one-electron transition density matrix in the -electronic approximation of the MO-LCAO-SCF method.For report 8 see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 173–180, February, 1986.     

Effect of the counterion on spin and charge density distribution in the phenanthroline radical anion

Institute of Physical Organic Chemistry and Carbon Chemistry, Academy of Sciences of the Ukrainian SSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 30, No. 2, pp. 194–197, March–April, 1989.