title: Effect of hydrogen-bonding on the excited-state reactivity of fullerene derivatives and its impact on the control of the emission polarisation from photopolic single crystals.
abstract: The kinetics of the irreversible photoinduced switch in polarisation (p) observed in single crystals of a fullerene derivative possessing hydrogen-bonding barbiturate units were investigated using confocal fluorescence microscopy. In the samples investigated, it was found that the maximum luminescence polarisation (p = 0.78) is obtained for an orientation of ca. 60° from the long axis of the crystal. Upon irradiation at 385 nm, the maximum luminescence polarisation undergoes a rotation of ca. 70° with respect to the initial orientation and reaches a new value of p = 0.40. The results indicate that the process is not dependent on the orientation of the incident polarised excitation beam and that it is not accompanied by a noticeable change in the photophysical properties of the crystal. Based on these observations, a mechanism is proposed in which photoinduced dimerisation occurs from the lowest energy emissive excimer-like state that acts as a sink for the excitation energy.
authors.affiliation: Univ. Bordeaux, CNRS, ISM UMR 5255 351, Cours de la Libération, 33400 Talence, France.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Raffy
authors.forename: Debdas
authors.initials: D
authors.lastname: Ray
authors.forename: Cheng-Che
authors.initials: CC
authors.lastname: Chu
authors.forename: André
authors.initials: A
authors.lastname: Del Guerzo
authors.forename: Dario M
authors.initials: DM
authors.lastname: Bassani