Charge transfer switching in photoexcited Ru(II) porphyrins: A time-resolved resonance Raman and spectroelectrochemical study
Journal Article
·
· Journal of Physical Chemistry
- Princeton Univ., NJ (United States)
The charge transfer (CT) excited states of Ru(II)OEP(Py){sub 2} and Ru(II)TPP(Py){sub 2} (TPP=tetraphenylporphyrin, OEP=octaethylporphyrin, and Py=pyridine) have been investigated by nanosecond time-resolved resonance Raman(TR{sup 3}) spectroscopy. The spectra reveal unexpected differences between the two species. The TR{sup 3} spectrum of [Ru(II)TPP(Py){sub 2}]{sup *} resembles the resonance Raman (RR) spectrum of the RuTPP(Py){sub 2} radical anion. Both spectra show strong enhancement of nontotally symmetric modes, resulting from a Jahn-Teller distortion due to the e{sub g}{sup *} orbital degeneracy. The band frequencies are slightly higher in the CT state than in the radical anion, reflecting the effect of the Ru(II) oxidation. Thus, the TR{sup 3} spectral features support a {sup 3}(d{pi},{pi}{sup *}) excited state assignment, with an electron transferred from Ru(II) to the porphyrin. In contrast, the TR3 spectrum [Ru(II)OEP(Py){sub 2}]{sup *} does not resemble the RR spectra of the Ru(II)OEP radical anion. Rather, it contains totally symmetric modes, at frequencies close to those of Ru(II)OEP(Py){sub 2}. In addition, bound pyridine modes appear at 1208 and 1603 cm{sup -1} in the TR{sup 3} spectrum and they shift upon pyridine perdeuteration. These characteristics imply electron transfer from Ru(II) to bound pyridine, instead of porphyrin, for the CT state of Ru(II)OEP(Py){sub 2}. 38 refs., 11 figs., 4 tabs.
- DOE Contract Number:
- FG02-88ER13876
- OSTI ID:
- 226752
- Journal Information:
- Journal of Physical Chemistry, Journal Name: Journal of Physical Chemistry Journal Issue: 10 Vol. 100; ISSN JPCHAX; ISSN 0022-3654
- Country of Publication:
- United States
- Language:
- English
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