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MO: Molekülphysik

MO 4: Femtosekundenspektroskopie: Elektrontransfer

MO 4.5: Talk

Monday, March 22, 2004, 12:00–12:15, HS 315

Ultrafast intramolecular electron transfer dynamics in crystal violet lactone — •Jerzy Karpiuk¹, Uli Schmidhammer², Stefan Lochbrunner², and Eberhard Riedle² — ¹Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland — ²Lehrstuhl für BioMolekulare Optik, Sektion Physik, Ludwig-Maximilians-Universität München, Germany

Dual fluorescence of crystal violet lactone (CVL) in polar solvents comes from two different excited states: (i) a moderately polar, optically generated excited state CT_A localized on the 6-DMAPd subunit (µ_e ≅ 10 D), and (ii) a highly polar excited state CT_B (µ_e ≅ 25 D) populated upon ultrafast electron transfer (ET) from one of the dimethylanilino groups to the phthalide moiety [1]. The CT_B state is formed only if it is sufficiently stabilized by solvent polarity. The kinetics in various aprotic and protic media have been studied using fs transient absorption spectroscopy with 386 nm excitation. It has been found that the build up rate of the CT_B state is faster than that of solvation and that the equilibrium between the CT_A and CT_B is established at a rate comparable to the solvent longitudinal dielectric relaxation time. Fast excited state deactivation in protic media (50 ps in methanol) due to hydrogen bonding with the solvent indicates a significant role of the C-O bond cleavage and opening of the lactone ring.

[1] J. Karpiuk, Annales of the Polish Chemical Society 2001, 271.