This study aims to show that the symmetry-breaking charge transfer (SBCT) in a donor-acceptor-donor (DAD) porphyrin triad occurs via solvent and structural fluctuations measured by using femtosecond broadband fluorescence upconversion spectroscopy, which can directly trace the origin of the emitting state by monitoring its emission dipole moment as a function of time. While the emission dipole moment of the triad in the excited state remains nearly unchanged in nonpolar solvents such as cyclohexane and toluene, it is significantly reduced in polar solvents such as benzonitrile due to a change in the emitting state from quadrupolar (the exciton coupled state) to dipolar symmetry (the relaxed S1 state). The latter state is formed by the SBCT process of DAD via a combination of solvent and structural fluctuations.
Bibliographical noteFunding Information:
This research at Yonsei University was supported by the Global Research Laboratory Program (2013K1A1A2A02050183) funded by the Ministry of Science, ICT & Future, Korea (D.K.). The quantum mechanical calculations were supported by the National Institute of Supercomputing and Network (NISN)/Korea Institute of Science and Technology Information (KISTI) with supercomputing resources including technical support (KSC-2018-C3-0008). The work at Kyoto was supported by JSPS KAKENHI Grant Numbers 25220802, 16K13952, and 18H03910 (A.O.).
Copyright © 2018 American Chemical Society.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films