Synthesis, Characterization, and Biological Activity of Mixed Ligand Co(II) Complexes of 8‐Hydroxyquinoline and Some Amino Acids

Abstract

Chiral mixed ligand (CML) metal complexes of the type MQL · H2O, where M is Co(II), HQ is 8‐hydroxyquinoline and HL is a chiral amino acid such as L(−)‐alanine, L(−)‐valine, L(−)‐leucine, L(−)‐phenylalanine, L(−)‐cysteine and L(+)‐glutamic acid, have been synthesized. Some of these CML metal complexes could also be synthesized from racemic amino acids using M(II) : 8‐hydroxyquinoline : racemic amino acids in 1:1:2 proportion by in situ stereoselective complexation. The metal complexes obtained from pure chiral amino acids have been characterized by elemental analyses and various physico‐chemical techniques such as molar conductance, magnetic susceptibility, electronic absorption, infrared spectral studies and thermal analysis. Room temperature magnetic susceptibility measurements of these complexes are indicative of a tetrahedral geometry. The molar conductance studies of the complexes in methanol solution at the range of 10–3 M concentration indicate their non‐electrolytic nature. Electronic absorption/reflectance spectra of the complexes show intra‐ligand, charge transfer, and the d–d transitions, consistent with their proposed geometry. Thermal studies show the presence of lattice water in the complexes. The bondings and structures of the complexes are discussed in detail on the basis of the results of various physico‐chemical studies. All of these metal complexes have been screened for their biological activity against selected microbial strains.