Synthesis, electrochemical, and molecular inclusion properties of ‘canopied’ trinuclear ruthenium complexes with six anchoring groups on an ITO electrode

Abstract

New trinuclear Ru complexes bearing both 1,3,5-tris(2,2′:6′,2″-terpyridyl)benzene and bis(benzimidazol-2-yl)pyridine with six phosphonate anchors were synthesised and immobilised on an ITO electrode. The ‘canopied’ structure was proved by AFM measurements. The immobilised Ru trinuclear complex revealed a one step three-electron oxidation process for the Ru(II/III) couple at around +0.9 V vs.Ag/AgCl, indicating that the Ru–Ru interaction is small. For the Ru immobilised ITO surface, the electron transfer blocking and the electron mediation of [Fe(CN)₆]⁴⁻oxidation through the Ru(III) ↔ Ru(II) catalytic cycle are strongly dependent on the alkyl chain length. The spectroelectrochemistry of the Ru trinuclear complex monolayer on the ITO electrode showed a stable electrochromic response under the potential pulse. The present ‘canopied’ Ru trinuclear complexes hold a small cavity that encapsulates tetrathiafulvalene molecules, which can be proved by a cyclic voltammogram.