Photophysical Properties of Bimetallic and Trimetallic Cyanide-Bridged Ru(II) Polypyridines. Evidence of Delocalization in the Excited State

OVIEDO, PAOLA S.; CADRANEL, ALEJANDRO; PIESLINGER, GERMAN; HODAK, JOSÉ H.; BARALDO, LUIS M.

Filadelfia

Conferencia; 252th Congreso de la A. C. S; 2016

ACS

We present the photophysical properties of a family of cyanide-bridged ruthenium polipyridines, [(bpy)(tpy)Ru(µ-CN)Ru(bpy)2L]2+/3+ (tpy = 2,2?;6?,2??-terpyridine; bpy = 2,2?-bipyridine; L= acetonitrile(ACN, Fig. 1), thiocyanate, 4-Dimethylaminopyridine (DMAP) or chloro and a system of higher nuclearity, [(tpm)(bpy)Ru(µ-CN)Ru(bpy)2(µ-NC)Ru(tpm)(bpy)]4+ (tpm = tris(1-pyrazolyl)methane). The transient absorption of these complexes reveal the presence of excited states with a transition in the NIR that suggest a mixed-valence character for these states. This transition shifts to the red as the L ligand becomes a better donor. Comparison of the spectroscopy of these excited states with the spectroscopy of related mixed-valence complexes point to a delocalized nature for these species. These results make these complexes interesting candidates as molecular antennae for sunlight harvesting.