Preparation, Characterization and Biological Activity of New Nickel(II) Complexes Containing Mixed Ligands

Nickel(II) complexes containing mixed ligands; semicarbazone (SCH) {benzaldehyde semicarbazone (BSCH) or 2-fluorobenzaldehyde semicarbazone (FSCH)} and salicylaldehyde (SH) or anthranilic acid (AH) or 2\ methylaminofuran (FH) have been prepared and characterized physicochemically. Complexes of the type [Ni(SCH)(LH)2](N03) 2 {where SCH = BSCH or FSCH, LH = SH or AH or FH} have been proposed . The biological activities of the resulted complexes have been evaluated by agar plate diffution technique against five human pathogenic bacterial strains: Bacillus subtilis, Streptococcus pyogenes, Staphylococcus aureus, Pseudomonas aeruginosa and Proteus vulgaris. The complexes were found •Presented at the first conference on Biology , University of Mosul ,college of Education , 4-5 September 2007 Preparation, Characterization and to have antimicrobial activity on some gram-positive and gram-negative bacteria, in vitro. The effective concentrations ranging between 31.25-500 J.lg/ml. Pseudomonas aeruginosa and Staphylococcus aureus were the most sensitive bacteria followed by Proteus vulgaris. INTRODUCTION Nickel complexes occurred in several nickel-containing enzymes and have been proposed to be involved in catalytic reaction. Nickel complexes with macrocyclic ligands have been prepared, and some of them are forming a coordination polymer [1-3]. A good deal of work has been reported on the preparation and structural investigation of semicarbazone and their complexes [ 4-6]. This is due partially to their capability of acting as multidentate, NO, NNO, ONNO, donor with the fonnation of either monoor bior poly-nuclear complexes [7 ,8]. In addition to their interesting ligational propetiies, semicarbazones and their complexes have important biological applications [9-1 0] . There has been growing interest in the formation of mixed ligands chelates involving ligands containing different functional groups and transition metals of different oxidation states which can form chelates with ligands containing different donation sites [11]. On the other hand, coordination compounds with mixed ligands are of considerable importance in the field of metalloenzymes and other biological activities [ 12, 13]. Hence a large body of the coordination chemistry of mixed ligands with transition and non-transition metal ions have been reported recently [ 14, 15]. Due to the impmiance of mixed ligands complexes, we took a humble pmi in the chemistry of mixed ligands containing semicarbazones and their complexes, and some articles have been published on their coordination chemistry with transition and non-transition metal ions [ 16-18] . In view of this, and since mixed ligands complexes of semicarbazones and salicylaldehyde or anthranilic acid or 2-methylaminofuran with nickel (II) ion have not yet been reported, it is a matter of interest to determine the extent to which the biological properties of these ligands would be affected by incorporating nickel (II). ion. In the present work, nickel (II) complexes with mixed ligands { semicarbazones and salicylaldehyde or anthranilic acid or 2-methylaminofuran} have been prepared and characterized physicochemically. Also this work includes the study of antimicrobial activity of these complexes against Streptococcus pyogenes, Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa and Proteus vulgaris.