As a widely-used sunscreen compound, the caffeic acid (CA) shows the strong UV absorption, while the photoinduced reaction mechanisms behind its photoprotection ability are not fully understood. We try to investigate the photoinduced internal conversion dynamics of CA in order to explore the photoprotectiodn mechanism. The most stable CA isomer is selected to examine its nonadiabatic dynamics using the on-the-fly surface hopping simulations at the semi-empirical level of electronic-structure theory. The dynamics starting from different electronic states are simulated to explore the dependence of the photoinduced reaction channels on the excitation wavelengths. Several S1/S0 conical intersections, driven by the H-atom detachments and the ring deformations, have been found to be responsible for the nonadiabatic decay of the CA. The simulation results show that the branching ratio towards these intersections are modified by the light with different excitation energies. This provides the valuable information for the understanding of the photoprotection mechanism of the CA compound.
The
impact of mode-specific vibrational excitations on
initial-preparation
conditions was studied by examining the excited-state population decay
rates in the nonadiabatic dynamics of methyl nitrate (CH3ONO2). In particular, exciting a few specific modes by
adding a single quantum of energy clearly decelerated the nonadiabatic
dynamics population decay rates. The underlying reason for this slower
population decay was explained by analyzing the profiles of the excited-state
potential energy surfaces in the Franck–Condon regions and
the topology of the S1/S0 conical intersection.
This study not only provides physical insights into the key mechanisms
controlling nonadiabatic dynamics but also shows the possibility of
controlling nonadiabatic dynamics via mode-specific vibrational excitations.
The analysis of the leading active molecular motions in the on-the-fly trajectory surface hopping simulation provides the essential information to understand the geometric evolution in nonadiabatic dynamics. When the ring...
Although the effects of electron-deficient group substitution on isoindigo on the corresponding conjugated polymers are extensively studied, the modification of isoindigo core with electron-rich groups has not been investigated. It is envisioned that the introduction of the methoxy group on isoindigo will not only tune the highest occupied molecular orbital (HOMO) energy level of the corresponding polymers but also introduce O•••S "conformation lock" to increase the coplanarity of the polymers, which should facilitate hole transport. Herein, the syntheses of two methoxylated isoindigos and the investigations on the charge transport behaviors of their copolymers with bisthiophene (2T) and bisthiazole (2Tz) are reported. It is found that the substitution positions have a drastic influence on the UV-vis absorption and electrochemical properties for both monomers and polymers. Theoretical calculations and single crystal structure analysis confirm the existence of O•••S "conformation lock", however, both methoxy substitutions also change the aggregation behaviors of the corresponding polymers to a mixed face-on/edge-on orientation which has an adverse effect for charge transport. Among the four polymers, the polymer of 5,5'-methoxylated isoindigo and 2T exhibit the best hole mobility of 1.9 × 10 −1 cm 2 V −1 s −1 .
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.