Release Time:2019-03-09  Hits:

Indexed by: Journal Article

Date of Publication: 2012-03-01

Journal: DYES AND PIGMENTS

Included Journals: EI、SCIE

Volume: 92

Issue: 3

Page Number: 1361-1369

ISSN: 0143-7208

Key Words: Coumarin; ESIPT; Fluorescence; Density functional theory; Photochemistry; Photophysics

Abstract: Coumarin derivatives containing 8-benzothiazole (C-2) and its difluoroboron bound derivative (C-3) were prepared. Both derivatives show dual emission at 322 nm and 513 nm and large Stokes shift (188 nm), compared to the unsubstituted coumarin (C-1), which shows emission a: 356 nm with small Stokes shift of 46 nm. C-2 and C-3 show fluorescence in solid state, in contrast the C-1 is non-fluorescent in the solid state. The excited state intramolecular proton transfer (ESIPT) process of C-2 was fully rationalized by DFT/TDDFT calculations with optimization of the ground state (S-0) and excited state (S-1) geometries. TDDFT calculations propose that the large Stokes shift of C-2 and C-3 are due to the re-distribution of the frontier molecular orbitals at excited states. Study of the potential energy curve of C-2 indicated that the dual emission of the C-2 is due to the simultaneous S-1 and S-3 emission, not the rotamer of the enol form. (C) 2011 Elsevier Ltd. All rights reserved.