Coordination Compounds of Silver and Copper with S- and N-donor Ligands for Potential Biological Application

Abstract

This study deals with the complexes of copper and silver with nitrogen and sulphur donor ligands for potentional biological applications. Our main research was focused onthe synthesisof various ligands containing sulphur and nitrogen donor atoms and some commercially available ligands were also used in complexation with different metal ions such as copper and silver. In most of the cases, we got our expected products with no side reactions, for purification of organic derivatives column chromatography was extensively used. Different ligands which contained sulphur and nitrogen donor sites were synthesized and coupled with different metal salts of the above mentioned metals including pallidium and cobalt in few cases. These ligands can be divided into three different groups 1) quinoline based ligands 2) tetrahydroindazole based ligands 3) thiazole based ligands. The quinoline based ligands were synthesized by multistep reactions. All the reactions gave expected products with negligible side reactions. Compounds 1-9 in the following text are quinoline based ligands and their complexes. All the qunoline based complexes were tested for antifungal, antibacterial, antioxidant and enzymes inhibition activities. The best antibacterial agents among quinoline based complexes waspalladium based compound 7. Similarly the best antifungal agent among quinoline based complexes is compound 6. The antioxidant study showed that compound 7 hasthe highest antioxidant activity among quinoline based complexes, against both ABTS and DPPH. Similarly compounds 7 also showed highest enzymes inhibation against AChE and BChE. Two compounds 10 and 11 are ligands containing N and O donor sites, but at ordinary condition, their complexation with a suitable metal ion was not feasible. Compounds 12-16 are indazole complexes of copper and silver and they were checked for their antifungal, antibacterial, antioxidant and enzymes inhibition activities. Compound 12 was found most effective agent against E.coli, compound 13 was efficient against K. Pneumoniaboth exhibiting 16 mm zone of inhibition. Compounds 12 and 13 showed good activity against A. fumegatus. The antioxidant test of the indazole based complexes showed that compound 15 had better anti-oxidant activity, up to 73% (IC50 value 94µg/mL) and was most effective antioxidant among compounds of the series. Similarly in thiazole complexes17-20, the most active against E.coli and K. Pneumonia was compound 17 which exhibited 19 and 14 mm zone of inhibition, respectively. The antifungal test of the thiazole compounds showed that compounds 18 and 19 were comparatively more active against A. fumegatusas compared to other members of the series. In thiazole complexes 18 was better anti-oxidant agent, exhibiting IC50 value 69µg/mL for ABTS and 50µg/mL for DPPH. Compound 19 had low antioxidant activity IC50= 314µg/mL. Compound 20 was very active AChE inhibitor with 77% activity at 1000 µg/mL. Compound 18 inhibited BchEupto 74% (caculated IC50= 147 µg/mL).