Synthesis, characterization and arsenate binding events of new mononuclear copper(II) complexes

Abstract

Two new mononuclear copper (II) complexes [Cu(L)(H2O)Cl] (1) and [Cu(L)(H2O)(SCN)] (2) (HL = 2-[1-(2-dimethylamino-ethylimino)-ethyl]-phenol) have been synthesized and characterized in order to investigate their binding interaction with arsenate ions. Complexes 1 and 2 were synthesized by performing reaction of CuCl2·2H2O or CuCl2·2H2O/NH4SCN, respectively, with HL using Et3N as mild base in MeOH solution at room temperature, and characterized by employing a number of analytical techniques, for example, elemental analysis, molar electrical conductivity, FTIR, UV–Vis and mass spectrometry. Their structures, optimized at DFT/B3LYP/6-311G level, show that the copper atom in 1 and 2 exhibits a distorted square pyramidal geometry. In H2O/MeOH (3:1; v/v) solution, complexes 1 and 2 were examined for their binding affinity towards arsenate ions. The UV–Vis spectroscopic results specify that the arsenate group binds with 1 and 2 in 1:1 M ratio. The UV–Vis titration data were successfully utilized to calculate the binding constants of arsenate-bound Cu(II) complexes, and the values are found to be 1.723 × 104 M−1 and 2.161 × 104 M−1, corresponding to 1/AsO43− and 2/AsO43− assemblies, respectively.