120th General Meeting of the KCS

Type Poster Presentation
Area Physical Chemistry
Room No. Exhibition Hall 2+3
Time 10월 20일 (금요일) 13:00~14:30
Code PHYS.P-81
Subject Intramolecular charge transfer reaction dynamics investigated by femtosecond stimulated Raman spectroscopy
Authors Sebok Lee, kooknam jeon1, Myungsam Jen2, YOONSOO PANG*
Division of Physical Chemistry, Gwangju Institute of Science and Technology, Korea
1Department of Chemistry, Gwangju Institute of Science and Technology, Korea
2Division of Physical Chemistry Department of Chemi, Gwangju Institute of Science and Technology, Korea
Abstract 4-Dicyanomethylene-2-methyl-6-p-dimethylaminostryryl-4H-pyran (DCM) is well known to form the intramolecular charge transfer (ICT) between the dimethylamino (donor) and the cyanomethylene (acceptor) in the excited states. Although DCM has been widely used in many fluorescence applications and many experimental and theoretical investigations have been performed, no experimental evidence on the structure of the ICT state such as “twisted” (in the dimethylamino or dimethylanilino group)_and “planar” geometry has been revealed. In this work, the structural changes of DCM in the excited-state were directly observed by femtosecond stimulated Raman spectroscopy with both high temporal (<50 fs) and spectral (<10 cm-1) resolutions. In DMSO solution, the ICT process of DCM occurring in ~1 ps and the following vibrational relaxation of ~5 ps were confirmed by the population changes and frequency shifts of the excited state Raman bands of DCM including (CN), (C=C/C-C), and (CH3). The vibrational band at 1470 cm-1 tentatively assigned as (C=C) of dicyanomethylene group showed a major peak shift (1467 → 1490 cm-1) upon the ICT, which may implicate therotation of the dimethylamino group during the ICT process. For comparison, the excited state Raman spectra of DCM in CHCl3 will also be investigated, where the ICT process does not occur.
E-mail leesebok@gist.ac.kr