Single-crystal electronic and e.s.r. spectra of bis-(aquo)monoacetylacetonatocopper(II) picrate

Abstract

The polarised single-crystal electronic spectra and e.s.r. spectra of bis(aquo)monoacetylacetylacetonatocopper(II) picrate have been measured. The correlation of the single-crystal g-values and the crystallographic data suggest a d_xy ground state for the approximately square-pyramidal CuO₅ chromophore. The polarised single-crystal electronic spectra are interpreted in C2_v effective symmetry and yield a tentative partial one-electron orbital sequence d_xy > d_yz > d_xz with the position of the d_z² and d_x²–y² orbitals uncertain, but probably near to the d_yz and d_xz orbitals. The combined spin-orbit and orbital-reaction parameters are evaluated and suggest substantial π-bonding between the d_yz orbital and the acetylacetone ligand. The sequence of one-electron orbitals for this square-pyramidal complex is discussed in relation to the sequences for the square-coplanar and tetragonal-octahedral stereochemistries.