The single-crystal electronic and electron spin resonance spectra of trans-bis(monochloroacetato)bis-(2-methylpyridine)copper(II)

Abstract

The single-crystal polarised electronic and e.s.r. spectra of bis(monochloroacetato)bis(2-methylpyridine)copper(II) have been measured. The single-crystal g-values correlate with the in-plane copper–ligand directions and suggest a d_x²–y² ground state. The polarised single-crystal electronic spectra are interpreted in D_2h symmetry and yield the tentative one-electron orbital sequence: d_x²–y² > d_xy > d_yz > d_z² > d_xz. The combined spin–orbit and orbital reduction parameters are evaluated and suggest a small but significant amount of in-plane π-bonding. The nature of the in-plane copper–nitrogen and copper–oxygen bonding is discussed and the role of the long-bonded carboxylate oxygen ligands in determining the tetragonality present is discussed.