EPR studies on copper and cobalt triazene-1-oxide complexes in a frozen nematic medium

Abstract

EPR spectra of copper and cobalt complexes of certain triazene-1-oxide ligands have been measured in frozen nematic liquid crystal glasses in order to identify the principal directions of the magnetic interaction tensors. It is pointed out that the nature of solute alignment is primarily determined by its molecular shape and any chemical interaction between the metal complex and the functional groups of the solvent molecules. Once these factors are properly understood, oriented glass spectra can be used to identify the principal axes of the g and A tensors even for systems which deviate considerably from gross molecular planarity. The spin Hamiltonian parameters are discussed on the basis of the ligand field model. It is pointed out that all the cobalt complexes reported here have the unpaired electron in the dyz orbital.