IN SITU SYNTHESES AND CHARACTERIZATION OF TWO PHASES OF A COPPER COMPLEX: STRUCTURAL DIFFERENCE LEADING TO DIFFERENT PROPERTIES

A copper complex possessing two phases, i.e. alpha phase 2,2'-dimethyl-2,2'-bipyridinium tetrachloro-copper(ii) alpha-CuCl4(N,N'-dimethyl-2,2'-H(2)bipy) (1) and beta phase 2,2'-dimethyl-2,2'-bipyridinium tetrachloro-copper(ii) beta-CuCl4(N,N'-dimethyl-2,2'-H(2)bipy) (2) has been synthesized via solvothermal reactions and structurally characterized by single-crystal X-ray diffraction. Complex 1 crystallizes in the space group C2/c of the monoclinic system with four formula units in a cell: a = 16.4981(12), b = 7.9064(4), c = 13.2230(7) angstrom, beta = 116.967(6)degrees, V = 1537.27(16) angstrom(3), Dc = 1.701 g/cm(3), S = 1.062, R = 0.0264 and wR = 0.0659. Complex 2 crystallizes in the space group Fdd2 of the orthorhombic system with sixteen formula units in a cell: [a = 25.625(2)], b = 31.7054(15), c = 7.7164(4) angstrom, V = 6269.1(7) angstrom(3), Dc = 1.668 g/cm(3), S = 1.030, R = 0.0305 and wR = 0.0695. Complex 1 is characteristic of an isolated structure and a two-dimensional (2-D) supramolecular layer, while complex 2 features an isolated structure and a three-dimensional (3-D) supramolecular framework. Photoluminescent investigation reveals that they display emissions in the green (1) and red (2) regions. Optical absorption spectra reveal the presence of an energy band gap of 1.53 eV and 2.23 eV for 1 and 2, respectively.