Syntheses, crystal structures and conducting properties of new homoleptic copper (II) dithiocarbamate complexes

Abstract

Five new homoleptic dithiocarbamate complexes of the general formula [Cu(L)2] [L = L1 (N-benzyl-N-furfuryl dithiocarbamate) (1); L2 (N,N-difurfuryldithiocarbamate) (2); L3 (4-ethoxycarbonylpiperidine-1-dithiocarbamate) (3); L4 (4-ethoxycarbonylpiperazine-1-dithiocarbamate) (4) and L5 (N-benzyl-N-3-methylpyridyl dithiocarbamate) (5) have been prepared and characterized by elemental analysis, spectroscopy (IR, UV-Vis, EPR), magnetic moment determination and cyclic voltammetry; their structures have been elucidated by X-ray crystallography. Variations in sterically demanding substituents on the dithiocarbamate units lead to different structures. 1, 2, 3 and 4 are Cu(dtc)2 moieties in which the copper atoms occupy square planar environments which are connected via weak interactions in axial positions to form centrosymmetric dimers. The weak Cuâ̄S distances vary significantly in the four complexes. By contrast 5 is a monomer with two molecules in the asymmetric unit. The supramolecular architecture in the five complexes has been sustained in the solid state by, C-Hâ̄S, C-Hâ̄O, πâ̄π and C-Hâ̄π (chelate, CuS2C) interactions. The electrical properties of all the complexes studied by the impedance spectroscopic technique in the 303-373 K temperature range show semiconducting properties with σrt = 10 -7-10-5 S cm-1 and Ea = 0.23-0.66 eV. The dielectric properties of the complexes have been measured at variable frequency (100 Hz-5 MHz) in the 303-373 K range; and show notably that complex 3 has a high dielectric constant. © 2013 Elsevier B.V. All rights reserved.