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.