Four chromophores in one building block: synthesis, structure and characterization of trans-[Ru(MQ)4Cl2]4+ and trans-[Ru(4,4?-bpy)4Cl2] (MQ+ = N-methyl-4,4?-bipyridinium, bpy = bipyridine)

ALEJANDRO CADRANEL; JOSÉ H. HODAK

JOURNAL OF COORDINATION CHEMISTRY

TAYLOR & FRANCIS LTD

Lugar: Londres; Año: 2015 vol. 68 p. 1452 - 1464

0095-8972

We report the synthesis, crystal structure, electrochemical and spectroscopic properties of trans-[Ru(MQ)4Cl2]4+ (14+), where MQ+ = N-methyl-4,4′-bipyridinium. The crystal structure of 14+ shows thepyridinic rings bound in a trans fashion to the Ru ion. In 14+ and in its analog trans-[Ru(4,4′-bpy)4Cl2] (2, bpy = bipyridine), the electrochemical reduction waves of the four iminic ligands occurat very closely spaced potentials. In comparison with previously reported analogues, 14+ and 2 presenthigh molar extinction coefficients (ε = 20,000?50,000 M?1cm?1), and red-shifted absorptions (upto 800 nm for 14+ and up to 600 nm for 2) in acetonitrile. Upon protonation of the four exposednitrogens of 2 and electrochemical reduction of the ligands in 14+ and 2, spectral changes occur withretention of isosbestic points, revealing the presence of four independent chromophores. Theseresults suggest poor electronic communication between the aromatic ligands within each compound,in contrast to related complexes such as cis-[Ru(2,2′-bpy)2Cl2] (3).