On-the-Fly Nonadiabatic Dynamics of Caffeic Acid Sunscreen Compound



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.


Supplementary material

Supporting Information for: On-the-Fly Nonadiabatic Dynamics of Caffeic Acid Sunscreen Compound
Several relevant information: the isomers of caffeic acid (CA) and corresponding energies, active orbitals in the OM2/MRCI calculations, all relevant CI geometries and their energies, CI-IV seam along the C2-C3-C10-C12 torsional coordinate, additional results when the larger active space is used, vertical excitation energies (eV) with different active spaces, the branching ratio in the case that the high-frequency vibration modes are frozen in the initial samplings, the Cartesian coordinates of all important geometries.