Electron spin resonance study of the influence of the nitrogen substituent on the conformation and spin density distribution of phenothiazine derivatives

Abstract

The cation radicals of promethazine, isothiazine, and diethazine have been studied by e.s.r., and the results compared with those of other N-substituted phenothiazine derivatives. These results indicate that a position of the terminal amino centre closer to the ring system induces a cationic charge and spin density displacement in the heterocycle from nitrogen to sulphur. For short-chain derivatives with γ- branching, both electronic and steric effects can affect the spin density distribution. The correlation between the hyperfine couplings a_N and a(H_i,j) found in these species is interpreted as a modification of the relative weights of different resonant structures.