title: [Kinetics of rearrangement of solvation sheath of an excited molecule of the fluorescent probe 4"-dimethylaminochalcone].
abstract: Processes accompanying the quenching of the fluorescent probe 4"-dimethylaminochalcone by hydroxyl groups of the proton-donor solvent 1-butanol have been studied. The kinetics of the deactivation of the excited state of 4"-dimethylaminochalcone has been monitored from the transition absorption spectra at a time resolution of 50 fs and fluorescence decay at a time resolution of 30 ps. The data obtained allow thinking that the next picture occurs in 1-butanol. At first stage, the 4"-dimethylaminochalcone molecule in its ground state forms a hydrogen bond with an alcohol molecule. At the second stage, the absorption of light quantum and corresponding rise of the dipole moment of 4"-dimethylaminochalcone take place, the initially existing hydrogen bond is retained. The third stage consists in the rearrangement of the 4"-dimethylaminochalcone solvation shell formed by alcohol dipole molecules due to an increase of the dipole of moment 4"-dimethylaminochalcone; this rearrangement takes an energy of about 24 kJ/mol, the arrangement time constant is close to 40 ps; the initial hydrogen bond is retained. The fourth stage involves processes that lead to fluorescence quenching; their time constant is about 200 ps. Taking into account that the quenching is a much slower process than the relaxation of the solvation shell, it was supposed that the quenching is not a direct consequence of the solvation shell relaxation or the existence of the hydrogen bond formed prior to excitation. Then the fluorescence quenching of 4"-dimethylaminochalcone can be accomplished through some other processes that are observed in other fluorescent molecules: (a) rearrangement of the initial hydrogen bond from a conformation that cannot quench the fluorescence of 4"-dimethylaminochalcone to a more "effective" conformation, (b) charge transfer between the excited of molecule 4"-dimethylaminochalcone and alcohol, or (c) solvent-induced twist of the 4"-dimethylaminochalcone amino group (its withdrawal from the molecule plane) by the action of the solvent.
authors.forename: G E
authors.initials: GE
authors.lastname: Dobretsov
authors.forename: S K
authors.initials: SK
authors.lastname: Gularian
authors.forename: O M
authors.initials: OM
authors.lastname: Sarkisov
authors.forename: F E
authors.initials: FE
authors.lastname: Gostev
authors.forename: A N
authors.initials: AN
authors.lastname: Petrukhin
authors.forename: A A
authors.initials: AA
authors.lastname: Titov
authors.forename: V Iu
authors.initials: VIu
authors.lastname: Svetlichnyĭ
authors.forename: T I
authors.initials: TI
authors.lastname: Syreĭshchikova
mesh_terms: D020001:1-Butanol / Q000737:chemistry*; D047188:Chalcones / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000737:chemistry*; D007700:Kinetics; D013050:Spectrometry, Fluorescence
chemical_list: D047188:Chalcones; D005456:Fluorescent Dyes; C016396:dimethylaminochalcone; D020001:1-Butanol