X-ray and DFT studies of a mono- and binuclear copper(II) ionic compound containing a Schiff base

In the structure of trans-bis(ethanol-kappa O) tetrakis(1H-imidazole-kappa N-3)copper(II) bis[mu-N-(2-oxidobenzylidene)-D,L-glutamato]-kappa O-4(1),N,O-2\u27:O-2\u27;kappa O-4(2)\u27:O-1,N,O-2\u27-bis[(1H-imidazole-kappa N-3)cuprate(II)], [Cu(C3H4N2)(4)(C2H6O)(2)][Cu-2(C15H14N3O5)(2)], both ions are located on centres of inversion. The cation is mononuclear, showing a distorted octahedral coordination, while the anion is a binuclear centrosymmetric dimer with a square-pyramidal copper(II) coordination. An extensive three-dimensional hydrogen-bonding network is formed between the ions. According to B3LYP/6-31G* calculations, the two equivalent components of the anion are in doublet states (spin density located mostly on Cu II ions) and are coupled as a triplet, with only marginal preference over an open-shell singlet