Intramolecular Excited State Decay

Intramolecular Excited State Decay 1.6.1 Vibrational Relaxation... 

The discussion in this section has been oriented toward the use of intramolecular reactions and excited state decay to test... 

Intramolecular electron transfer in cytochrome c has been investigated by attaching photoactive Ru complexes to the protein surface. Ru(bpy)2(C03) (bpy = 2,2 -bipyridine) has been shown to react with surface His residues to yield, after addition of excess imidazole (im), Ru(bpy)2(im)(His) +. The protein-bound Ru complexes are luminescent, but the excited states ( Ru ) are rather short lived (r 100 ns). When direct electron transfer from Ru to the heme cannot compete with excited-state decay, electron-transfer quenchers (e.g., Ru(NH3)6 + ) are added to the solution to intercept a small fraction (1-10%) of the excited molecules, yielding (with oxidative quenchers) Ru ". If, before laser excitation of the Ru site, the heme is reduced, then the Fe to Ru + reaction (ket) can be monitored by transient absorption spectroscopy. The ket values for five different modified cytochromes have been reported (Ru(His-33), 2.6(3) xlO Ru(His-39), 3.2(4) xlO Ru(His-62), 1.0(2) x 10 Ru(His-... 

Abstract. In this contribution some recent developments in the area of intramolecular excited state interactions will be discussed. In a first part the power of global compartmental analysis of fluorescence decays of intramolecular exciplex forming systems is exemplified. In a second part the use of photoacoustic spectroscopy in the study of intramolecular back electron transfer is illustrated and in a last part the alternative linking of a donor and an acceptor with a flexible silane chain will be compared with a similar donor and acceptor linked by an alkane chain. 

Coe JD, Martinez TJ (2005) Competitive decay at two- and three-state conical intersections in excited-state intramolecular proton transfer. J Am Chem Soc 127 4560... 

Ge(TPP)R2, Ge(TPP)(Fc)Ph, and Ge(TPP)Fc2) the spectrum after 2 /us was consistent with a triplet excited state, although this decayed much faster for the fer-rocenyl complexes. Addition of ferrocene to Ge(TPP)R2 also quenches triplet lifetimes. A similar situation was observed for the indium complexes In(Por)R, and the triplet-state quenching was attributed to an energy transfer process from the excited-state triplet to ferrocene. In the case of the germanium porphyrins, the longer-lived triplet state in Ge(TPP)R2 is responsible for the Ge—C bond homolysis, and both inter- and intramolecular quenching by ferrocene is observed. 

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