A combined experimental and theoretical charge density study of the chemical bonding and magnetism in 3-amino-propanolato Cu(II) complexes containing weakly coordinated anions.

The experimental (100 K) and theoretical charge densities in the binuclear complexes [Cu2(ap)2(L)2] (ap = 3-aminopropanolate) 1 (L = nitrite), 2 (L = nitrate), and 3 (L = formate) have been examined. These complexes contain the same centrosymmetric alkoxy-bridged motif, where each strongly Jahn−Teller distorted Cu(II) ion is ligated to three O atoms and one N atom in a square-planar arrangement. This primary coordination sphere is augmented by a long contact with the O atom of a pendant L anion from an adjacent molecule in the crystal lattice. Topological analyses of the experimental and theoretical densities according to the quantum theory of atoms in molecules (QTAIM) are in excellent agreement. Consideration of a number of topological indicators including ρ(r), ▽2ρ(r), the delocalization indices δ(A,B), and the integral ∮A∩B ρ(r) of the density over the zero flux surface shared by the two atoms confirms that the Cu−O and Cu−N bonding in the primary coordination sphere has a strong covalent component, b...