Spin Densities in Odd Alternant Hydrocarbon Radicals

Abstract

The spin densities at the starred and unstarred carbon atoms of odd alternant hydrocarbon radicals have been calculated using the method of alternant molecular orbitals introduced by Löwdin. The spin densities at unstarred positions are shown to be negative in sign and to depend upon the electron correlation parameter θ. Observed spin densities on one carbon atom can be used to estimate θ and to calculate spin densities on other carbon atoms. Illustrative calculations for the cases of triphenylmethyl and perinaphthenyl are described.