Cu(ii) and Ni(ii) dioxotetraamine complexes integrated with tetrathiafulvalene moiety; structures and solution chemistry

A new bifunctional tetrathiafulvalene (TTF) derivative has been designed and synthesized, in which the TTF moiety (a redox functional group) is integrated with a dioxotetraamine (a coordination functional group) structure. Like other dioxotetraamine compounds, it is capable of acting as an ion leaving and accepting ligand for protons and Cu(II) and Ni(II) ions in solution. Experiments of pH titration have shown that the TTF unit adds new redox properties to the traditional ligand. Oxidation of the ligand increases the acidity of the imido group and the coordination of metal ions is also sensitive to the oxidation state of the ligand. The ligand forms either a square coordinated Ni(II) complex with two deprotonated imido groups and two amino groups, or a pentacoordinated Cu(II) complex with an additional solvent molecule. The compounds form a belt structure with strong N–H⋯O hydrogen bonds, which is a basic character for this type of compound in the crystalline form.