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Issue 24, 2004
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Deuteration effects on the vibronic structure of the fluorescence spectra and the internal conversion rates of triangular [4]phenylene

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Abstract

Deuteration effects on the vibronic structure of the emission and excitation spectra of triangular [4]phenylene (D3h [4]phenylene) were studied using laser-excited Shpol’skii spectroscopy (LESS) in an octane matrix at 4.2 K. For correct assignment of the vibrational modes, the experimental results were compared with calculated frequencies (B3LYP/6-31G*). CH vibrations were identified by their characteristic isotopic shifts in the spectra of deuterated triangular [4]phenylenes. Two CC stretching modes, at 100 cm−1 and 1176 cm−1, suitable as probes for bond strength changes in the excited state, were identified. The isotope effect on the internal conversion rates of triangular [4]phenylene was evaluated from measurements of temperature dependent lifetime. Isotope dependency and the magnitude of the internal conversion rates indicate that internal conversion in triangular [4]phenylene is most likely induced by CH vibrations. The results obtained by LESS and lifetime measurements were compared with PM3 PECI calculations of the excited state structure. The theoretical results and the relation between ground and excited state vibration energies of the 1176 cm−1 probe vibration indicate a reduction of bond alternation of the central cyclohexatriene ring in the excited state.

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Publication details

The article was received on 21 Sep 2004, accepted on 11 Oct 2004 and first published on 29 Oct 2004


Article type: Paper
DOI: 10.1039/B414545C
Citation: Phys. Chem. Chem. Phys., 2004,6, 5476-5483
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    Deuteration effects on the vibronic structure of the fluorescence spectra and the internal conversion rates of triangular [4]phenylene

    C. Dosche, M. U. Kumke, H.-G. Löhmannsröben, F. Ariese, A. N. Bader, C. Gooijer, O. Š. Miljanić, M. Iwamoto, K. P. C. Vollhardt, R. Puchta and N. J. R. van Eikema Hommes, Phys. Chem. Chem. Phys., 2004, 6, 5476
    DOI: 10.1039/B414545C

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