Excited State Dynamics of Cyanide-Bridged Ru Polypyridines

OVIEDO, PAOLA S.; CADRANEL, ALEJANDRO; PIESLINGER, GERMAN E.; BARALDO VICTORICA, LUIS MARIO

Cancún

Conferencia; Frontiers in Photochemistry Conference; 2018

Fusion Conferences Limited

Picosecond time dynamics of a family of cyanide-bridged Ru polypyridines have been analyzed by means of transient absorption measurements and spectroelectrochemistry. The transient absorption experiment reveal the presence of long lived excited states with a very strong photo-induced absorption in the near infrared. The energy and shape of these bands indicate that these excited states can be described as mixed-valence complexes where the cyanide promotes a very strong coupling between the linked Ru moieties. Careful analysis of the decay of dynamics reveal that for some of these complexes, there are also excited states with little photo-induced absorption in the near infrared. Interestingly both types of states can coexist in nanosecond scale which indicates that the rate of interconversion between this states is very slow. This observation is reminiscent of the behavior that we have observed for the complexes [Ru(tpm)(bpy)(NCS)]+ and [Ru(tpm)(bpy)(CN)]+ (tpm = tris(1-pyrazolyl)methane, bpy = 2,2?-bipyridine), where we detected two MLCT excited states of low energy that interconvert into each other with a life-time of several hundred picoseconds. The properties of the observed excited states are very different. While the excited state that present a strong NIR PIA promotes a rapid energy transfer to a Cr acceptor, the other state seem to be inactive for this process.