title: Radiationless deactivation of 6-aminocoumarin from the S1-ICT state in nonspecifically interacting solvents.
abstract: This paper presents the results of a spectral (absorption and emission) and photophysical study of 6-aminocoumarin (6AC) in the solvents with which this molecule interacts only nonspecifically (n-alkanes, tetrachloromethane and 1-chloro-n-alkanes) and in nitriles. The strong effects of the solvents on the emission spectra, fluorescence quantum yield and lifetime of 6AC were observed. The results of the steady-state and time-resolved photophysical study suggest the presence of very fast nonradiative deactivation processes. It is concluded that besides fluorescence, the efficient S(1)-ICT → S(0) internal conversion in nonpolar aprotic solvents arises from vibronic interactions between close-lying S(1)-ICT(π,π*) and S(2)(n,π*) states. Moreover, unexpectedly efficient triplet state formation occurs. In nitriles the intermolecular hydrogen-bonding interactions with solvent molecules also facilitate the nonradiative decay process involving the S(1)-exciplex.
authors.affiliation: Department of Chemistry, Adam Mickiewicz University, Poznań, Poland. ewakryst@amu.edu.pl
authors.forename: Ewa
authors.initials: E
authors.lastname: Krystkowiak
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Dobek
authors.forename: Gotard
authors.initials: G
authors.lastname: Burdziński
authors.forename: Andrzej
authors.initials: A
authors.lastname: Maciejewski
mesh_terms: D000042:Absorption; D003374:Coumarins / Q000737:chemistry*; D004579:Electron Transport; D012997:Solvents / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
chemical_list: D003374:Coumarins; D012997:Solvents; C067496:6-amino-1,2-benzopyrone