ESR Studies of Copper(II) Complexes of Ethylenediamine and Its Analogues

The ESR spectra of the copper(II) complexes of ethylenediamine, 1,2-diaminopropane, meso-2,3-diaminobutane, 1,3-diaminopropane, and ammonia were measured in methanolic and aqueous solutions at room temperature and in frozen solutions at the temperature of liquid nitrogen. The covalency of the bonding of the copper atom to the ligand atoms in these complexes was evaluated from the g values, the copper hyperfine constants, and the nitrogen super-hyperfine constants. Even in the case of amino groups which were coordinating groups, the π bonding seemed to be as important in determining the properties of the complexes as the σ bonding.