Electron spin resonance study of 10-(3-dimethylamino-2-methylpropyl)phenothiazine cation radical in solution

Abstract

The e.s.r. spectrum of the cation radical of 10-(3-dimethylamino-2-methylpropyl)phenothiazine in sulphuric solution has been studied in the temperature range 233–333 K, with the help of computer simulation. The analysis at 293 K indicates the non-equivalence of the β-protons of the side-chain. Furthermore, the changes observed with the temperature affect both the linewidth and the hyperfine splittings of the β-protons. These results are interpreted on the basis of the branching of the side-chain at the γ-position and the resulting unsymmetrical character of the γ-carbon. The hyperfine splitting constant values a_(β-H1) and a_(β-H2) measured at 233 K have allowed us to calculate the dihedral angles between the 2p(π) orbital of the heterocyclic nitrogen and the β-H–C bonds.