Synthesis, structural investigations, and in vitro biological activity of Co(II) and Fe(III) mixed ligand complexes of 1,10-phenanthroline and 2,2'-bipyridine.

Herein, we report, four new mixed ligand complexes of Cobalt(II) and Iron(III), viz., [Co(L1 )(L2 )(H2 O)2 ]Cl2 (1), [Co(L1 )(L2 )(L3 )(H2 O)]Cl2 (2), [Fe(L1 )(L2 )(H2 O)2 ]Cl3 (3), and [Fe(L1 )(L2 )(L3 )(H2 O)]Cl3 (4), where L1  = 1,10-phenanthroline (C12 H8 N2 ), L2  = 2,2'-bipyridine (C10 H8 N2 ), and L3  = acetamide (C2 H5 NO)). They were synthesized and characterized using spectroscopic analysis (ESI-MS, ICP-OES, FT-IR, and UV-Vis), elemental analysis, melting point determination, and conductance measurement. The in vitro antibacterial activity was tested on two Gram-positive Staphylococcus aureus (S. aureus) and Streptococcus pyogenes (S. pyogenes) and two Gram-negative Escherichia coli (E. Coli)and Klebsiella pneumoniae (K. pneumoniae) bacteria using the disc diffusion method. Based on the analytical and spectroscopic data, octahedral geometries are assigned to the complexes. Co(II) complexes were found more active against K. pneumoniae than the corresponding Fe(III) complexes which indicated that antibacterial activities of metal complexes have tuned with the nature of the metal. The results provide an insight to design and readily prepare task-specific metal-based drugs for interaction with particular bacterial strains.