Abstract: A rapid, efficient, clean and environmentally benign exclusive synthesis of Schiff bases as new ligands has been developed using condensation of 2-aminonicotinic acid with salicyldehyde, 5-nitrosalicyldehyde, 5-bromosalicyldehyde and 5-methoxysalicyldehyde efficiently in a water suspension medium using acid catalyst with excellent yields under microwaves irradiation. The results are compared with conventional methods. All the Schiff bases were tridentate (NNO donor) ligands that were used for complexation with Co²⁺, Ni²⁺ and Zn²⁺ ions. All the ecofriendly synthesized Schiff bases and their metal complexes were characterized by analytical and spectral methods. The synthesized Schiff bases and their transition metal complexes were evaluated for their in vitro antibacterial activity against four gram-negative and two gram-positive bacterial stains by the agar-well diffusion method. Schiff bases were found to exhibit either no or low to moderate activity but all the complexes exhibited varied vigorous activity against different bacteria. Schiff bases which were inactive before complexation became active and less active became more active upon coordination with mentioned bivalent transition metal ions.

KEYWORDS: Microwave irradiation, Schiff bases, Coordination compounds, Antibacterial activity.