Synthesis, characterization and antimicrobial properties of cobalt(II) and cobalt(III) complexes derived from 1,10-phenanthroline with nitrate and azide co-ligands

Abstract Two complexes, a cobalt(II) complex [Co(phen)3(NO3)2]·2H2O (1) and a novel Co(III) complex with mixed ligands [diazido-bis(1,10-phenanthroline-κ2 N,N′)cobalt(III)]nitrate [Co(phen)2(N3)2]NO3 (2), have been synthesized and were characterized by physico-chemical and spectroscopic methods. The cobalt(III) complex (2) crystallizes in the orthorhombic crystal system with space group Iba2 with four formula units. The central Co(III) atom is six coordinate with four N atoms of two 1,10-phenanthroline (1,10-phen) molecules and two terminal N atoms from two azide anions giving a distorted octahedral geometry with a CoN6 chromophore. The molecular structure of the compound is consolidated by face-to-face π–π stacking between the aromatic rings of 1,10-phen ligand. The ligands, metal salt and the complexes were also evaluated for their antimicrobial activities in vitro against eight pathogens (four bacteria and four fungi species).