Excited state trans-cis photoisomerization via non-adiabatic dynamics of novel UVB protective sunscreens.

In this work, we verified that the newly synthesized octyl urocanate compounds (U1 and U2) can significantly absorb UVB and confirmed their excellent light stability. In addition, we combined the Proton Nuclear Magnetic Resonance (1HNMR) and Time-Dependent Density Functional Theory (TDDFT) calculation methods to clearly explain the UV protection mechanism of U1 and U2. Octyl urocanate can be excited to an excited state after absorbing ultraviolet light in the UVB region. After that, the isomerized molecules at the conical intersection point (CI) between the potential energy surfaces (PESs) of the S 1 and S 0 states, rapidly relax to the ground state from the S 1 excited state in the form of a non-radiative transition. Ultrafast trans -cis photoisomerization can be carried out in a very short time. We found the characteristic peak of cis -U1 from the NMR of trans -U1 after being irradiated by the laser. Therefore, the energy absorbed by U1 and U2 can be quickly consumed through the non-radiative photoisomerization process. Therefore, we believe that octyl urocanate U1 and U2 are very good potential sunscreen molecules that absorb UVB. [Display omitted] • The compounds U1 and U2 with ultraviolet light were prepared by a new octyl urocanate. • U1 and U2 are obtained by esterification on the basis of natural product urocanic acid. • The absorb of U1 and U2 mainly is in the UVB region, and the fluorescence emission intensity is very small. • U1 and U2 can undergo cis -trans isomerization to relax energy after absorbing ultraviolet light. [ABSTRACT FROM AUTHOR]