Electron spin resonance in the triplet states of naphthalene and azanaphthalenes with parallel polarization. observation of the proton hyperfine structure of ΔM S = ±2 transitions in glassy matrices and in stretched poly(vinyl alcohol) films

Abstract

By applying a microwave magnetic field ( B rf) parallel to an external magnetic field ( B), the ESR spectra of naphthalene (N), azanaphthalenes (AN's: 1- and 2-AN's), and diazanaphthalenes (DAN's: 1,3-, 1,4-, 1,5-, 1,6-, and 1,8-DAN'S) in the lowest excited triplet states have been studied in ethanol glasses and in stretched poly(vinyl alcohol) films at 77 K. In general, the observations in random rigid solutions do not permit one to observe the proton hyperfine structures when B rf is perpendicular to B. However, when B rf is parallel to B, the proton hyperfine structures are easily observed in random rigid solutions. The assignment of these ESR signals was carried out with the aid of the stretched-film method.