Experimental and computational studies on transition metals interaction with Leucine and Isoleucine

Abstract

In this study, we reported the leucine and isoleucine based metal complexes with Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II). The complexes were synthesized in an aqueous medium followed by characterization with various experimental techniques. Besides experimental investigation, the density functional theory (DFT) calculation is performed which confirms a square planar structure for the Co, Ni and Cu complexes whereas Zn, Cd and Hg complexes adopt the distorted tetrahedral structure. The stability of the complexes is ensured by some calculated thermodynamic parameters. In addition, the elemental and thermos-gravimetric study are also conducted. Metal chelating affects the frontier molecular orbital energies of the ligand and reduces the HOMO-LUMO gap. The complexes are more reactive than the parent ligand. The FT-IR, UV-Visible and NMR spectral analysis of the complexes are reported. The experimental FT-IR and the electronic absorption properties agree with the calculated values. The presence of the characteristic metal-ligand charge transfer and d-d transitions in the complexes is confirmed through photo-excitation study. The UV-Visible reflectance spectral analysis indicates good conducting behavior of the complexes. The differential scanning calorimetry (DSC) analysis shows that the complexes undergo endothermic phase transition. The magnetic moment value agrees with the paramagnetic behavior of Co, Ni and Cu complexes but diamagnetic behavior of Zn, Cd and Hg complexes.