Ultrafast Ring-Closure Reaction of Photochromic Indolylfulgimides Studied with

Journal of Physical Chemistry A, 2008, 112, 210-4 published on 21.12.2007
Journal of Physical Chemistry A, online article

The ring-opening and ring-closure reactions of a photochromic indolylfulgimide are investigated with femtosecond vibrational spectroscopy. Spectral signatures due to excited-state decay and vibrational cooling are seen in the mid-IR region. For the ring-opening reaction triggered with visible pulses, a lifetime of the excited electronic state of 4 ps was obtained in polar solution. In a nonpolar solvent, this time constant is reduced to 2 ps. The ring-closure reaction induced with UV pulses displays an excited-state lifetime and thus a building of the photoproduct of roughly 0.5 ps. For all processes, the subsequent cooling occurs on a 15-ps time scale lasting up to around 50 ps. The time-resolved IR measurements do not support the existence of any long-living intermediate states.

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