An electron spin resonance, ENDOR, TRIPLE resonance, and INDO study of the radicals formed by the reduction of monoquaternised N-alkyl- and N-aryl-4,4′-bipyridylium salts

Abstract

The radicals formed by the reduction of N-monoquaternised-4,4′-bipyridylium salts (both alkyl and aryl) were studied by electron spin and multiple resonance and INDO calculations. Unlike the diquaternised salts reported previously, the radicals formed by monoquaternary salts are highly dependent on both the solvent and the reductant used and this behaviour is described in terms of the possible complexes formed. The neutral radicals of N-methyl- and N-phenyl-4,4′-bipyridylium are compared with the related N-methyl-N′-phenyl-4,4′-bipyridylium diquaternised radical cation.