Early excited state dynamics of 6-styryl-substituted pyrylium salts exhibiting dual fluorescence.
A series of 6-styryl-2,4-diphenylpyrylium salts exhibiting dual fluorescence has been investigated by fluorescence up-conversion in conjunction with quantum chemical calculations. The short-wavelength emission is due to an excited state localized on the pyrylium fragment and the long-wavelength emission arises from a charge-transfer state delocalized over the whole molecule. The two fluorescing states do not exhibit a precursor-successor relationship. The rise time of the short-wavelength fluorescence is smaller than 200 fs, and that of the long-wavelength emission depends on the electron-donating property of the styryl group substituent. The rise is almost prompt with the weaker donors but is slower, wavelength and viscosity dependent with the strongest electron-donating group. A model involving a S(2)/S(1) conical intersection is proposed to account for these observations.
Pigliucci
Anatolio
A
Department of Physical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, CH-1211 Geneva, Switzerland.
Nikolov
Peter
P
Rehaman
Abdul
A
Gagliardi
Laura
L
Cramer
Christopher J
CJ
Vauthey
Eric
E