A New Family of Ruthenium (II) Polypyridine Complexes Bearing 5-Aryltetrazolate Ligands as Systems for Electrochemiluminescent Devices

A new family of mono- and dinuclear ruthenium polypyridyl complexes containing 5-aryl-tetrazolate ligands such as the deprotonated form of 4-(1,H-tetrazol-5 –yl)-benzonitrile [4-TBNH] and bis-(1,H-tetrazol-5-yl)-benzene [BTBH2], have been synthesized and thoroughly characterized. The reactivity of the mononuclear species towards different electrophiles such as H+ and CH3+, has been investigated and the effects of the resulting regioselective electrophilic attacks on the electronic and structural properties of the tetrazolate ligand, have been studied by NMR (1H, 13C) spectroscopy and X-ray crystal structures. Absorption and emission spectroscopy, together with an electrochemical and UV-Vis-NIR spectroelectrochemical investigation of the uncoordinated ligand and complexes have been performed, highlighting a rather good luminescence efficiency and a poor bridge-mediated electronic communication between the metal centres of the dinuclear complexes. The electrogenerated chemiluminescence (ECL) of the dinuclear species has been explored and, for one of these, an exceptionally high ECL efficiency has been observed, comparable to that of [Ru(bpy)3]2+ which is considered a standard in ECL studies.