Open AccessExcited-State Decay Paths in Tetraphenylethene Derivatives
Author(s) -
YuanJun Gao,
Xue-Ping Chang,
Xiangyang Li,
Quan-Song Li,
Ganglong Cui,
Walter Thiel
Publication year - 2017
Publication title -
the journal of physical chemistry. a/the journal of physical chemistry. a.
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.756
H-Index - 235
eISSN - 1520-5215
pISSN - 1089-5639
DOI - 10.1021/acs.jpca.7b00197
Subject(s) - photoisomerization , photoexcitation , excited state , quantum yield , chemistry , photochemistry , fluorescence , yield (engineering) , conical intersection , aggregation induced emission , isomerization , atomic physics , materials science , physics , organic chemistry , quantum mechanics , metallurgy , catalysis
The photophysical properties of tetraphenylethene (TPE) compounds may differ widely depending on the substitution pattern, for example, with regard to the fluorescence quantum yield ϕ f and the propensity to exhibit aggregation-induced emission (AIE). We report combined electronic structure calculations and nonadiabatic dynamics simulations to study the excited-state decay mechanisms of two TPE derivatives with four methyl substituents, either in the meta position (TPE-4mM, ϕ f = 0.1%) or in the ortho position (TPE-4oM, ϕ f = 64.3%). In both cases, two excited-state decay pathways may be relevant, namely, photoisomerization around the central ethylenic double bond and photocyclization involving two adjacent phenyl rings. In TPE-4mM, the barrierless S 1 cyclization is favored; it is responsible for the ultralow fluorescence quantum yield observed experimentally. In TPE-4oM, both the S 1 photocyclization and photoisomerization paths are blocked by non-negligible barriers, and fluorescence is thus feasible. Nonadiabatic dynamics simulations with more than 1000 surface hopping trajectories show ultrafast cyclization upon photoexcitation of TPE-4mM, whereas TPE-4oM remains unreactive during the 1 ps simulations. We discuss the chances for spectroscopic detection of the postulated cyclic photoproduct of TPE-4mM and the relevance of our findings for the AIE process.