Collect. Czech. Chem. Commun. 1981, 46, 1318-1323

CNDO/S CI calculation of spin-orbit coupling and intersystem crossing in photochemical biradical formation reaction

Boris F. Minaeva and David M. Kižnerb

a The J. Heyrovský Institute of Physical Chemistry and Electrochemistry, Czechoslovak Academy of Sciences, 121 38 Prague 2, Czechoslovakia
b Tomsk State University, 634 010 Tomsk, U.S.S.R.


The CNDO/S CI method has been employed to calculate potential curves for singlet and triplet states along reaction path for photolysis of cyclopentanone (dissociation of the C-C bond and biradical formation). Spin-orbit coupling between these two states and the probability of intersystem crossing (ISC) in Landau-Zener approximation were calculated. This probability has proved enough to compete with nuclear spin induced ISC process. In this way some peculiarities of chemically induced dynamic nuclear polarization in formation of products via biradicals can be qualitatively understood.