Synthesis, X-ray crystallography and electrochemistry of three novel copper complexes with imidazole-containing hydantoin and thiohydantoins

The reactions of imidazolemethylene-substituted thiohydantoins with copper(II) chloride yield three kinds of complexes with different copper coordination mode. Binuclear complexes Cu2(L1-H)2Cl2 (5), Cu2(L2-H)2Cl (6) and polymeric complex [Cu(L2-H)Cl(H2O)]n (7) (L1 = (4Z)-2-thioxo-4-[(1-methyl-1H-imidazol-2-yl)methylene]-1-allylimidazol-5(4H)-one, L2 = (4Z)-2-thioxo-4-[(1-methyl-1H-imidazol-2-yl)methylene]-1-(n-propyl)imidazol-5(4H)-one) were synthesized and characterized by X-ray diffraction, IR and UV–Vis spectroscopy, and cyclic voltammetry. The crystal structures of homovalent dicopper(II,II) complex 5, mixed-valence [Cu+1.5, Cu+1.5] complex 6 and polymeric copper(II) complex 7 were refined from X-ray powder and single crystal data. Complexes 5–7 undergo eight-step quasi-reversible electrochemical reduction at +0.42 to −2.23 V to stable intermediates, which do not dissociate into free ligand and metal in the conditions of cyclic voltammetry experiments.

Graphical abstractCopper complexes of three different type were obtained using two structurally similar imidazole-containing hydantoin and thiohydantoin ligands. All complexes undergo multi-step quasi-reversible electrochemical reduction at +0.42 to −2.23 V with the formation of stable intermediates.Figure optionsDownload full-size imageDownload as PowerPoint slide