Synthesis and structure of a mixed ligand copper(II) compound based on a distorted {CuN2O3} square pyramid

The synthesis, spectra, thermal study and crystal structure of a mixed ligand copper(II) compound viz. [Cu(biq)(acac)(NO 3 )] 1 (biq = 2,2′-biquinoline, acac = acetylacetonate) are reported. The {CuN 2 O 3 } coordination sphere is made up of two oxygen atoms of an unique acac ligand, an oxygen of the nitrate group and one N atom of biq ligand which form the basal plane {CuNO 3 } of a square pyramid. A second nitrogen atom of the biq ligand occupies the apical position resulting in a distorted square pyramidal {CuN 2 O 3 } polyhedron. In the crystal structure, each neutral square pyramidal copper(II) species is linked with two symmetry related molecules with the aid of intermolecular C-H×××O hydrogen bonding interactions. A study of fifteen mixed ligand copper(II) acetylacetonates reveals that in this series of compounds, 1 exhibits maximum deviation of the {CuN 2 O 3 } polyhedron from square pyramidal towards trigonal bipyramidal geometry.