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

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

Philadelphia

Congreso; 252nd American Chemical Society National Meeting & Exposition; 2016

American Chemical Society

We present the photophysical properties of a family of cyanide-bridged ruthenium polypyridines, [(bpy)(tpy)Ru(µ-CN)Ru(bpy)2L]2+/3+ (tpy = 2,2?;6?,2??-terpyridine; bpy = 2,2?-bipyridine; L= acetonitrile (1, Fig. 1), 4-dimethylaminopyridine (2), thiocyanate (3) or chloride (4). Near infrared transient absorption spectra of these complexes reveal that the first populate state present a band that we assign as a metal to metal charge transfer (MMCT) and indicates a mixed-valence character for this state. This transition shifts to the red as the L ligand becomes a better donor. By comparison with the properties of related mixed-valence complexes a delocalized nature can be assigned to the excited state of (4). It is interesting to note that the reverse tendency is observed for the ground state mixed-valence form of these complexes reveling the role of the radical-anion in the photoinduced state. This first state decays to the emissive state that do not present a transition in the NIR pointing to a different configuration for the latter.