Interligand electron transfer

Fig. 7. Excited-state interligand electron transfer in fac-[Re(MQ)(CO)3(dmb)]2+. Reproduced from Ref. (15) by permission of the Royal Society of Chemistry.

Spectroscopic properties of [Ru(bpy)3] " ", and the effects of varying the diimine ligands in [Ru(bpy)3 L ] + (L = diimine) on the electronic spectra and redox properties of these complexes have been reviewed. The properties of the optical emission and excitation spectra of [Ru(bpy)3] +, [Ru(bpy)2(bpy-d )] + and [Ru(bpy-d )3] " " and of related Os, Rh , and Pt and Os species have been analyzed and trends arising from changes in the metal d or MLCT character in the lowest triplet states have been discussed. A study of the interligand electron transfer and transition state dynamics in [Ru(bpy)3] " " has been carried out. The results of X-ray excited optical luminescence and XANES studies on a fine powder film of [Ru(bpy)3][C104]2 show that C and Ru localized excitation enhances the photoluminescence yield, but that of N does not. 

Experimental data for the interligand electron transfer kinetics following photoexcitation of [Os(bpy)3] " " are in agreement with a reaction/diffusion model measurements were made in a range of solvents. The variable parameters in the model are interligand electronic coupling and solvent polarization barrier height. 

TRIR and TR3 spectra were used to study the dynamics and mechanism of metal-to-ligand and interligand electron transfer in /uc-[Re(-MQ+)(CO)3(dmb)]2+, where MQ+ = V-methyl-4,4 -bipyridinium, dmb = 4,4,-dimethyl-2,2,-bipyridine.191,192... 

Benko G., Kallioinen J., Myllyperkio P., Trif F., Korppi-Tommola J. E. I., Yartsev A. P. and Sundstrom V. (2004), Interligand electron transfer determines triplet excited state electron injection in RuN3-sensitized TiOi films , J. Phys. Chem. B 108, 2862-2867. 

Doom and Hupp have used preresonance Raman spectra in an analysis of the vibronic components which contribute to the intervalence absorption maximum of [(CN)5Ru -CN-Ru (NH3)5] and to the MLCT absorption maximum of [(bpy)Ru(NH3)4] ". These authors employ the time-dependent scattering approach of Heller to obtain the nuclear displacements of several vibrational modes coupled to the electronic transitions. They find in each case that several vibrational modes, spanning a wide range of frequencies, do contribute significantly to the photoinduced electron transfer processes. Hopkins and co-workers have used a two-color, ps Raman technique to investigate interligand electron transfer in Ru(II)-tn5-polypyridyl complexes, and they find vibrational relaxation of the electronically excited mole ule occurs within about 30 ps of excitation, after which interligand equilibration occurs more slowly than 5 x 10 s. 

In what follows we will summarize the results that lead to the conclusion that electron transfer between the pyridyl ligands of the RuN3 sensitizer (interligand electron transfer, ILET) is the rate-limiting process... 

In conclusion, photoinduced electron transfer fi om the sensitizer RuN3 to nanostructured Ti02 occurs along two pathways. The major part of the molecules ( 60 %) inject directly fiom the non-thermalized MLCT state prior to IVR and intersystem crossing, while the remaining part inject from the thermalized triplet state of the non-attached ligand, in a process controlled by interligand electron transfer. 

Malone, R.A., Kelley, D.F. Interligand electron transfer and transition state dynamics in Ru (Il)trisbipyridine. J. Chem. Phys. 95, 8970-8976 (1991)... 

In order to explain this increase in electron transfer rate and to elucidate which pathway was followed (intraligand or interligand), a rotaxane structure was elaborated171,721 (Figure 6). Here, the principle of construction of the architecture was again based on the 3-dimensional template effect of copper (i). 

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