Synthesis, characterization, and biological investigation of new mixed‐ligand complexes

A novel series of mixed‐ligand complexes of 5,5′‐{(1E,1E′)‐1,4‐phenelynebis(diazene‐2,1‐diyl)}bis(quinolin‐8‐ol) (H 2 L 1 ) as a primary ligand and 4‐aminoantipyrine(L 2 ) as a secondary ligand with Mn(II) ion were prepared using two general formulae: [Mn 2 (H 2 L 1 ) 2 (L 2 ) 2 X 4 ].4Cl (X = OH 2 ( 1 ), ONO 2 − ( 2 ), Cl=nil; OAc( 3 ), Cl = nil) and [Mn 2 (H 2 L 1 )(L 2 ) 2 (O 2 SO 2 ) 2 ]( 4 ). Free ligands and their complexes were characterized. Electronic absorption spectra of the mixed‐ligand complexes indicate a distorted octahedral geometry around the central metal ion, and the anions X − are in the axial positions for all compounds. The ligands behave in a neutral bidentate manner, through nitrogen atoms and oxygen atoms of the carbonyl group (L 2 ), whereas H 2 L 1 coordinated through nitrogen and OH groups as a neutral bidentate ligand. All complexes do not contain coordinated water molecules, but complex ( 1 ) contains four water molecules. The water molecules are removed in a single step. The complexes exhibited magnetic susceptibility corresponding to five unpaired electrons. The antimicrobial activity of the Mn(II) mixed‐ligand complexes ( 1–4 ) against two gram‐positive bacteria, three local gram‐negative bacteria, and three fungi species was tested. Mn(II) mixed‐ligand complex ( 2 ) exhibited significant antibacterial activity against Bacillus cereus , Staphylococcus aureus , Escherichia coli , Klebsiella pneumoniae , and Pseudomonas sp. Mixed‐ligand complex ( 2 ) exhibited a high potential cytotoxicity against the growth of human lung cancer cells.