A novel ferrocenic copper(II) complex Salen-like, derived from 5-chloromethyl-2-hydroxyacetophenone and N-ferrocenmethylaniline: Design, spectral approach and solvent effect towards electrochemical behavior of Fc+/Fc redox couple

Abstract

This paper reports the synthesis, spectroscopic characterizations and electrochemical behavior of the obtained tetradentate copper (II)-Schiff base complex with its two wings as ferrocenylaniline moieties. This new ferrocenic derivative with two ferrocenylaniline entities surrounding the copper (II)-Salen complex (5) was synthesized by reacting N-ferrocenmethyl-N-phenyl-5-aminomethyl-2-hydroxyacetophenone (3) with one half equivalent of 1,2-diaminoethane in absolute ethanol. As for the intermediates involved in this synthetic sequence, the compound (3) was prepared in tetrahydrofuran (THF) by reacting N-ferrocenmethylaniline (2) with 5-chloromethyl-2-hydroxyacetophenone (1) in presence of sodium hydrogenocarbonate (NaHCO3). The compound (3) condensed on the diamine yields the Schiff base ligand (4). Under a nitrogen atmosphere and stirring at 50 °C, the ligand dissolved in absolute ethanol with stoichiometric amount of copper acetate monohydrate (Cu(COOCH3)2·H2O) formed the expected tetradentate Cu(II)-Schiff base complex (5) after 6 h of reaction. All these synthesized compounds gave yields varying from 50 to 90%. Their purities were estimated from elemental analysis while the molecular structures were elucidated with FT-IR, UV–Vis, 1H- and 13C- NMR. For the obtained copper complex, it is tetracoordinated in a distorted square planar environment with two nitrogen and two oxygen atoms as donor sites. The electrochemical behaviors of the synthesized compounds were explored using cyclic voltammetry. This investigation showed an important anodic shifting of the Epc and Epa potential waves for the Fc+/Fc redox couple of compound (3) in dichloromethane (DC) medium, compared to other polar media like acetonitrile (AN), dimethylformamide (DMF) and dimethylsulfoxide (DMSO). This behavior was also observed for the tetradentate copper (II)-Salen complex with its different metallic centers.