An electron spin resonance study of substituent effects in adducts of cobalt(II) Schiff-base complexes with dioxygen

Abstract

E.s.r. spectral measurements have been made on dioxygen adducts [Co^IIL]·O₂ of certain quadridentate Schiff-base chelates (L) of Co^II in frozen chloroform solutions containing pyridine or 2,6-dimethylpyridine. The effects of variation of the substituent groups in the Schiff-base ligand on the magnetic and structural parameters of the dioxygen adduct–base complex have been determined. While there is some variation in the cobalt hyperfine parameters, the Co–O–O angle lies within the range 115–120°. The widely varying g values and hyperfine parameters for the chelate complexes themselves may be understood on the basis of recent calculations using the angular-overlap model.