Bis(diamino-diamido)-tetrathiafulvalene, a redox active sensor for proton, anions, and cations

Abstract

A bis(diamino-diamido) tetrathiafulvalene (TTF) derivative H₄L² has been designed and synthesized. Experiments of pH titration reveal that integrating the redox active TTF unit with the diamino-diamido moiety adds new properties to the traditional ligand. Oxidation of the TTF moiety increases the acidity of the amido group, and the coordination of metal ions is also sensitive to the oxidation state of the ligand. This compound is capable of acting as a leaving or accepting ligand for proton and metal ions. The electrochemistry of the protonated TTF derivative of H₄L² was studied in the presence of a series of oxo anions and metal cations. The results indicate that the redox potentials selectively respond to HC₂O₄⁻ and SO₄²⁻ anions, and Ni(II) and Cu(II) cations. Solid-state structures of a cation–anion salt H₈L²·2SO₄·8H₂O and a nickel coordination compound [Ni₂L²]·2DMF have been characterized by means of X-ray crystallography which are helpful in understanding the inter-ion interactions.