The preparation, characterization, crystal structure and biological activities of some copper(II) complexes of the 2-benzoylpyridine Schiff bases of S-methyl- and S-benzyldithiocarbazate

The complexes [Cu(NNS)X] (HNNS represents the 2-benzoylpyridine Schiff bases of S-methyl- or S-benzyldithiocarbazate; X = Cl, Br, NO3) have been prepared and characterized by a variety of physico-chemical techniques. Magnetic and spectral evidence support a square-planar structure for the [Cu(Bp-SR)X] (Bp-SR=the benzoylpyridine Schiff bases; R = CH3, CH2C6H5; X = Cl, Br) and [Cu(Bp-SMe)NO3] complexes and a five-coordinate distorted square-pyramidal structure for the [Cu(Bp-SBz)NO3] complex. The crystal structures of [Cu(Bp-SMe)NO3] and [Cu(Bp-SBz)NO3] have been determined by X-ray diffraction studies. The complex [Cu(Bp-SMe)NO3] crystallizes in the triclinic space group P1 with a = 7.600(3), b = 10.5346(2), c = 11.564(3) Angstrom, alpha = 116.0033(14), beta = 103.91(3), gamma = 91.55(3)degrees, V = 798.3(4) Angstrom(3) and Z = 2. The complex has a distorted square-planar geometry with the copper ion lying in an approximate plane of four coordinating atoms, three of which come from the 2-benzoylpyridine Schiff base of S-methyldithiocarbazate while the fourth coordination site is occupied by an oxygen from the nitrate ligand. The complex, [Cu(Bp-SBz)NO3] crystallizes in the monoclinic space group P2(1)/a with a = 9.0124(19), b = 18.501(5), c = 13.0642(24) Angstrom, beta = 106.377(15)degrees, V = 2089.9(9) Angstrom(3) and Z = 4. The coordination environment around the copper(II) ion is a distorted square-pyramid with three donor atoms (NNS) coming from the 2-benzoylpyridine Schiff base and the fourth and fifth atoms (oxygen) coming from the bidentate NO3- ion. The antifungal and antibacterial properties of the copper(II) complexes have been evaluated against three pathogenic fungi and two bacteria. The Schiff bases and copper (II) complexes display moderate antifungal activities but their activities are less than that of the commercially important antifungal agent nystatin.