Comparative study by electron spin resonance, ENDOR, and TRIPLE resonance of the radical cations of isomeric (1,4)-pyridinophanes and the analogous compound N,N′-dibenzyl-4,4′-bipyridylium

Abstract

The e.s.r., ENDOR, and TRIPLE resonance spectra are reported for the radical cations of isomeric orthocyclo- and metacyclo-pyridinophanes. Evidence is presented which suggests that while both are doublet states, there is rapid inter-annular electron movement between the bipyridylium moieties only in the latter. Multiple resonance spectra of the straight-chain model N,N′-dibenzyl-4,4′-bipyridylium (benzylquat) show the previously undetected phenyl couplings and reveal discrete signals from the ortho- and meta-bipyridyl protons (previously thought equivalent).