Synthesis, Characterization and Antioxidant Activity of Mixed–Ligand Complexes of Mn(Ii), Co(Ii), Ni(Ii), Cu(Ii) And Zn(Ii) Ions with Nicotinic Acid and Phenylalanine

Abstract

Mixed ligand metal complexes of nicotinic acid and phenylalanine with Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) have been synthesized and characterized using infrared spectroscopy, electronic spectra, conductivity, melting point, and solubility. Nicotinic acid and phenylalanine were reacted with some metal (II) chloride salts in the molar ratio of 1:2:1 (M: NA: Phe) which produced the complexes with various colours and a percentage yield range of 58 97%. The melting points of the compounds ranged from 320 to 348 oC, with conductivities ranging from 9.01-26.4 Scm-2mol-1. The infrared spectra of the ligands and metal complexes revealed that nicotinic acid is a monodentate ligand that coordinates to the metal via the nitrogen of the pyridine ring, whereas phenylalanine is a bidentate ligand that coordinates to the metal via the carbonyl oxygen v(C=O) and nitrogen of the amine v(N-H) groups. The electronic spectra of the compounds are compatible with an octahedral geometry, except for the zinc complex, which probably has a tetrahedral structure. All the complexes were slightly soluble in some of the organic solvents used, methanol, ethanol, dimethylformide (DMF), acetone, chloroform, ethyl acetate, and benzene. The ligands and complexes were evaluated for antioxidant activity in vitro using the DPPH and hydrogen peroxide methods. According to the findings, all the complexes have higher activity than the ligand (nicotinic acid) but were less active than the standard (ascorbic acid). This indicates, the complexes have strong antioxidant properties.