New Complexes of Co(II) With Benzilbis (semicarbazone) & Amino Acids

New cobalt (II) complexes with mixed ligands including benzilbis(semicarbazone)-BscH2 and amino acids-AH {glycine (GlyH) or alanine (AlaH) or cysteine (CysH) or cystine (CyH) or tyrosine (TyrH) or histidine (HisH) or threonine (ThrH) or proline (ProH)} have been prepared and characterized physiccochemically. They have been found to have general formulas [Co(BscH2)(AH)(NO3)](NO3) or [Co(BscH2)(AH)](NO3)2 and [Co(BscH)(A)] in neutral and basic medium, respectively (where AH = any of the amino acid, A = deprotonated amino acid, BscH = deprotonated BscH2 ligand). The results supported that the complexes had high spin octahedral geometries. INTRODUCTION A good deal of work had been reported on the synthesis and characterization of semicarbazones and their complexes [1-4] due to their capability of acting as multidentate donor with the formation of either monoor bior poly-nuclear complexes [5,6]. In addition, semicarbazones and their complexes had important biological activities [7,8] and providing models for metal ligand bonding sites in several enzymes [9].Amino acids complexes with transition metal ions played an important New Complexes of Co(II) 2 role in biochemistry and biology. Great attention had been paid to elucidate and interprete the structural characteristics and the thermodynamic of these biologically ligand complexes [10-14]. The more common coordination of amino acids was as bidentate chelate through the N and O atoms which gave rise to a thermodynamically stable five-membered ring for α-amino acids (six-membered ring for β-amino acids). GlyH, AlaH, TyrH and ProH acted as bidentate chelating ligands. Wheras HisH and ThrH were acted as either tridentate or bidentate chelating ligands. CysH was a major metal binding site in proteins. It was ambidentate in that it could be tridentate or bidentate through combination of (S, N), (N,O) or (S,O) donor sets. The ligand CyH chelated through (N,O) donor atoms with first row transition elements [15]. There has been growing interest in the formation of mixed ligand complexes of transition and non transition metals [16-20] due to their importance in the field of metalloenzymes and other biological activities [21,22]. Due to the biological importance of mixed ligand complexes, we took a modest part in the coordination chemistry of mixed ligand complexes and some articles have been published on their coordination chemistry with transition and non-transition metal ions [23-27]. In the present work, new cobalt (II) complexes with mixed ligand benzilbis(semicarbazone) and amino acids (Figure1) have been synthesized and characterized physicochemically. Figure 1: Structures of the ligands EXPERIMENTAL C C Ph Ph