ESR study on copper(II) macrocyclic polythia complexes

ESR measurements have been made on complexes formed by copper(II) with [12]anS4, [13]anS4, iso-[14]anS4, and [18]anS6; they show intramolecular reduction for the central ion by electron transfer from the donor sulfur atoms, and free cation-radicals are formed in solution. The covalency parameter α2 indicates that the copper-sulfur bonds are mainly covalent. The electronic structures are analogous to those of the active centers in copper-bearing blue proteins.