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MO: Fachverband Molekülphysik
MO 17: Elektronische Spektroskopie
MO 17.3: Poster
Tuesday, March 11, 2008, 14:00–19:00, Poster C1
Transient Spectroscopy of UV excited flavone and substituted porphyrins: Triplet-Triplet absorption and comparison with theory — •Gernot Engler1, Dennis Löwenich1, Karl Kleinermanns1, Martin Kleinschmidt2, Christel Marian2, and Sergej Kovalenko3 — 1Institute for Physical Chemistry, Heinrich-Heine-University, Universitätsstr. 1, D-40225 Düsseldorf, Germany — 2nstitute for Theoretical Chemistry, Heinrich-Heine-University, Universitätsstr. 1, D-40225 Düsseldorf, Germany — 3Institute for Chemistry, Humboldt University of Berlin, Brook-Taylor-Strasse 2, D-12489, Berlin, Germany
We reinvestigated the triplet absorption of flavone in solvents with different polarity at excitation wavelengths of 266 nm and 355 nm. Strong solvent dependent shifts of the transient absorption spectrum can be explained by comparison with TDDFT/MRCI calculations. We also investigated the triplet absorption of tetraphenylporphyrin (TPP), tetracarboxyphenylporphyrin (TCPP) and tetrahydroxyphenylporphyrin (THPP) in cyclohexane and ethanol in the spectral range 280-800 nm and observed T1-TN absorption at 320, 370, 440 and 470 nm which could be assigned to specific transitions by comparison with TDDFT/MRCI calculations. TCPP and THPP showed transient absorption at similar wavelengths and similar T1- lifetimes of a few us. The rise times both of the flavone and porphyrin transients are < 20 ns pointing to very efficient S1-T1 intersystem crossing.