Substituent Position Effects On Sunscreen Photodynamics: A Closer Look At Methyl Anthranilate
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Towards the development of a <em>bottom-up</em> rationale for sunscreen design, the effects of substituent position on the ultrafast photodynamics of the sunscreen precursor methyl anthranilate (MA, an <em>ortho</em> compound) were evaluated by studying <em>para-</em> and <em>meta-</em>MA in vacuum. Time-resolved ion yield (TR-IY) measurements reveal a long-lived S<sub>1</sub> excited state (≫ 1.2 ns) for <em>para-</em>MA, proposed to be the result of a weakly fluorescent, bound excited state. In the case of <em>meta-</em>MA, TR-IY transients reveal a much faster (~2 ns) excited state relaxation, possibly due to multiple low-lying S<sub>1</sub>/S<sub>0</sub> conical intersections of prefulvenic character. While <em>meta-</em>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 <em>para</em>-MA and <em>meta-</em>MA (<em>e.g</em>. para_0_opt.xyz) SA-CASSCF conical intersection geometries from both molecules as (<em>e.g</em>. p1.xyz)
