Exchange interaction in oxygen-bridged dimers of copper (II) with aromatic N-oxides. I. Method of calculation and application to di-μ-(pyridine N-oxide)-bis [dichlorocopper(II)

Abstract

A method, based on the Dirac–Van Vleck–Serber permutation degeneracy model, for the estimation of the exchange integral J in oxygen-bridged dimers of copper (II) with aromatic N-oxides is demonstrated for the case of the dimer di-μ-(pyridine N-oxide)-bis (dichlorocopper II), [(C6H5NO)CuCl2]2. The calculations are limited to the planar three-center, four-electron system Cu(↑)–O(↑↓)–Cu(↑), with due account of the second bridging oxygen and all omitted atoms or electrons. The computational details and approximations are discussed. It is found that J is sensitive to the structural data, the atomic orbitals and functions used, the ionic state of copper, and configuration interaction (inclusion of excited, charge-transfer configurations). The exchange interaction is mediated by a σ superexchange pathway, all π pathways being excluded. Finally, both the oxygen 2s and 2p orbitals contribute to J.