ESR Studies of Some Copper(II) β-Diketone Chelate Complexes in Heterocyclic Basic Solvents

Abstract

Abstract Three representative copper(II) β-diketone chelate complexes, bis-(ethylacetoacetato)copper-(II), bis-(salicylaldehydato)copper(II), and bis-(acetylacetonato)copper(II), have been investigated by the ESR method in order to estimate their structures in various solvents. The super-hyperfine structures due to the equal coupling of the unpaired electron with two nitrogen atoms were clearly observed for the first two complexes dissolved in pyridine or γ-picoline. The structures of these two complexes in pyridine or γ-picoline could be estimated to be as follows; a new square-planar coordination occurs through two nitrogen atoms of these basic solvent molecules and two oxygen atoms of the four originally-coordinating ligand oxygen atoms, and the other oxygen atoms are coordinated as apical ligand atoms with less strength. On the other hand, the ESR spectra of the latter complex dissolved in pyridine or γ-picoline show a significantly strong ligand field only in the axis normal to the molecular plane; this indicates that the coordination of the basic solvent molecules along the axis normal to the molecular plane occurs.