Electron spin resonance of 1,4-diazabutadiene alkali metal chelates

Abstract

n-Alkyl substituted 1,4-diazabutadienes form, in ethereal solvents, chelate complexes with lithium, sodium and potassium. The e.s.r. spectra of these complexes have been recorded at different temperatures. The spectra show a selective broadening of the spectral lines which is caused by the modulation of the anisotropic hyperfine and g tensor interactions. An accurate analysis of the linewidth of the single hyperfine components allows us to obtain the g tensor components and the anisotropic part of the nitrogen hyperfine coupling. The latter is in fair agreement with values of the nitrogen coupling of alkali earth biradical chelates of the same ligands, as obtained from the e.s.r. spectra of glassy solutions.

The g factors are compared with the values expected on the basis of Stone's theory. The mutual interaction of the lone pair orbitals of the two nitrogen atoms seems to be important in explaining the experimental results.