Abstract
Sinapoyl malate is a natural plant sunscreen molecule which protects leaves from harmful ultraviolet radiation. Here, the ultrafast dynamics of three sinapoyl malate derivatives, sinapoyl L‐dimethyl malate, sinapoyl L‐diethyl malate and sinapoyl L‐di‐t‐butyl malate, have been studied using transient electronic absorption spectroscopy, in a dioxane and methanol solvent environment to investigate how well preserved these dynamics remain with increasing molecular complexity. In all cases it was found that, upon photoexcitation, deactivation occurs via a trans‐cis isomerisation pathway within ∼20–30 ps. This cis‐photoproduct, formed during photodeactivation, is stable and longed‐lived for all molecules in both solvents. The incredible levels of conservation of the isomerisation pathway with increased molecular complexity demonstrate the efficacy of these molecules as ultraviolet photoprotectors, even in strongly perturbing solvents. As such, we suggest these molecules might be well‐suited for augmentations to further improve their photoprotective efficacy or chemical compatibility with other components of sunscreen mixtures, whilst conserving their underlying photodynamic properties.
UV‐visible pump‐probe spectroscopy is used to understand the photodeactivation mechanism in a series of sinapoyl malate derivatives. In sinapoyl malate, this photodeactivation occurs via a trans‐cis isomeration pathway within ∼20–30 ps. This pathway appears remarkably well‐conserved even in the most augmented system studied, sinapoyl L‐di‐t‐butyl malate. As such, these molecules might be well‐suited for further augmentation to improve their efficacy or chemical compatibility within sunscreen mixtures.