Substituent position effects on sunscreen photodynamics: a closer look at methyl anthranilate

Towards the development of a bottom-up rationale for sunscreen design, the effects of substituent position on the ultrafast photodynamics of the sunscreen precursor methyl anthranilate (MA, an ortho compound) were evaluated by studying para- and meta-MA in vacuum. Time-resolved ion yield (TR-IY) measurements reveal a long-lived S1 excited state (≫ 1.2 ns) for para-MA, proposed to be the result of a weakly fluorescent, bound excited state. In the case of meta-MA, TR-IY transients reveal a much faster (~2 ns) excited state relaxation, possibly due to multiple low-lying S1/S0 conical intersections of prefulvenic character. While meta-MA may not be an ideal sunscreen ingredient due to a low ultraviolet absorbance, its comparatively efficient relaxation mechanism may constitute an alternative to common sunscreen relaxation pathways.

This archive contains example computational input and output files for both species, including:

TD-DFT files for use with NWChem

SA-CASSCF conical intersection search files for use with Gaussian 03

CASPT2 files for use with Gaussian 03

DFT relaxed geometries for para-MA and meta-MA  (e.g. para_0_opt.xyz)

SA-CASSCF conical intersection geometries from both molecules as (e.g. p1.xyz)