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) (H2L1) as a primary ligand and 4‐aminoantipyrine(L2) as a secondary ligand with Mn(II) ion were prepared using two general formulae: [Mn2(H2L1)2(L2)2X4].4Cl (X = OH2(1), ONO2−(2), Cl=nil; OAc(3), Cl = nil) and [Mn2(H2L1)(L2)2(O2SO2)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 (L2), whereas H2L1 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. The treated cells of Bacillus cereuswith Mn(II) mixed‐ligand complex(2) (A and B; control, C and D; Bacillus cereus affected with DMF, E and F; Bacillus cereus affected with complex) revealed that almost all cells were lysed and void of cytoplasmic fluid with completely shrinkage of cytoplasmic membrane (F), also the presence of an increase in vacuolization and corresponding disorganization of the cytoplasm was observed (E). The cells treated with DMF were observed slightly visible alterations (C and D).