Sterically crowded chelate complexes of copper(II) with phenoxazinyl ligands: ESR study

A copper complex with 1-H-1-oxo-2,4,6,8-tetrakis(tert-butyl)phenoxazinyl free radical ligands was synthesized, and its magnetic properties and ESR spectra were measured at 77–290 K. It was shown that a ground electron state with one unpaired electron is typical of this complex at 77–290 K. The magnetoresonance parameters of this complex are characterized by ag-factor value (1.978) that is rather unusual for copper-containing compounds and by hyperfine coupling due to Cu nuclei. The considerable broadening of ESR spectral lines with increasing temperature is probably not due to the formation of a quartet state (S=3/2). A model of electron states of the compound investigated was developed in the framework of ligand field theory, which made it possible to explain the pattern of the ESR spectra, which were untypical of copper complexes.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 894–899, May, 1995.This study was financially supported by the International Science Foundation (Grant NRT 000).