Coordination behavior of 3-amino-5,5′-dimethylhydantoin towards Ni(II) and Zn(II) ions: Synthesis, spectral characterization and DFT calculations

Abstract

The interaction of 3-amino-5,5′-dimethylhydantoin with nickel and zinc ions was investigated at different conditions by means of UV–Vis, FTIR spectroscopy and electrochemical methods as well as DFT quantum chemical calculations. Through calculated DFT frequencies and experimental FTIR spectra of the complexes the correlation analysis has been made. NBO analysis of the ligand and complexes provides the information about intramolecular resonance stabilization energy and charge transfer between ligand and metal ions. First derivative UV–Vis spectra were done in order to resolve the π→π* and n→π* carbonyl electron transitions of the ligand and complexes. We have shown that complexes with 1:2 stoichiometry were formed at pH closed to physiological. The stability constant was determined for 3-amino-5,5′-dimethylhydantoin (L) and Ni(II) ions using differential pulse polarography data. The existence of one complex (n¯ = 2) is proved in the presence of high ligand concentration (CL = 2 × 10−3 ÷ 6 × 10−3 mol L−1) and the values of the total constant is: lgβNI(II)-L=9.5±0.4 (I = 0.1). The UV–Vis spectroscopy and DFT calculations confirm the stoichiometry of the complexes. The results of the study are useful for incorporation with chemical equilibrium models for evaluation of the speciation and the reactions of metals with hydantoin derivatives in order to develop methods for determination of these metals in different milieu.