Synthesis of novel mononuclear and dinuclear ruthenium(II) complexes with terpyridine and acetylacetonate ancillary ligands and cyanamide derivative ligands

International audienceSeveral new mononuclear and dinuclear ruthenium(II) complexes – incorporating 2,2′:6′,2″-terpyridine and acetylacetonate as ancillary ligands and phenylcyanamide derivative ligands – of the type [Ru(tpy)(acac)(L)] and [{Ru(tpy)(acac)}2(μ-L′)] (where tpy = 2,2′:6′,2″-terpyridine, acac = acetylacetonate, L = hmbpcyd = 4-(3-hydroxy-3-methylbutynyl)phenylcyanamide anion (2) and epcyd = 4-ethynylphenylcyanamide anion (3) and L′ = bcpda = bis(4-cyanamidophenyl)diacetylene dianion (4) and bcpea = 9,10-bis(4-cyanamidophenylethynyl)anthracene dianion (5)) were synthesized in a stepwise manner starting from [Ru(tpy)(acac)(Ipcyd)] (1), where Ipcyd = 4-iodophenylcyanamide anion. Tetraphenylarsonium salts of the phenylcyanamide derivative ligands were also prepared. The four complexes have been characterized by UV–Vis, IR, ES-MS, electrochemistry and 1H NMR. Mononuclear complexes 2 and 3 were further characterized by 13C NMR. The single crystal X-ray structure of 2 was determined, it crystallized with one molecule of water with empirical formula of C32H31N5O5Ru, in a monoclinic crystal system and space group of P21/n with a = 17.642(5) Å, b = 9.634(2) Å, c = 20.063(7) Å, β = 92.65(3)°, V = 3406(2) Å3 and Z = 4. The structure was refined to a final R factor of 0.040. The Ru(III/II) couple of 1–3 appeared around 0.34 V versus the saturated calomel electrode in dimethylformamide and at a slightly higher potential, around 0.36–0.37 V for 4 and 5. Spectroelectrochemical studies were also performed for 4 and 5, no intervalence transition was observed despite all attempts