Electron Spin Resonance of the Aromatic-Alkali Metal System. II

Abstract

A theoretical investigation is made to interpret the Na hyperfine splittings .in electron spin resonance of the aromatic-Na system in solution. In calculating the odd electron density on the Na nucleus, one assumes the charge transfer mechanism that the odd electron, in the first approximation, ~ccomodated in the n-molecular orbital of the aromatic migrates to the Na atom through overlapping between orbitals. The result obtained shows fairly good agreement with observation. § I. Introduction A recent development of the high resolution ESR (electron spin resonance) technique made it possible to observe the precise hfs (hyperfine splittiJ?-g) in ESR of radicals and ions. Here we shall discuss the hfs due to the coupling between the odd electron spin and the Na nuclear spin in ESR of the aromatic­ Na system in solution. Atherton and Weissman1l observed the ESR spectra of the naphthalene-Na system, in which each line of 25 hf lines due to the naphtha­ lene negative ion is split into four equally spaced components of equal intensities. These four lines caused by the Na nucleus of spin 3/2 have a coupling constant of about 1 gauss. According to Atherton and Weissman, Robertson has calculated with success the values of this coupling constant from the same mechanism as we present in this article. We hope our independent calculation might open a little more general scope on such problems. Deguchi et al. 11 l are performing