The photophysical properties of menthyl anthranilate: A UV-A sunscreen

The results of a comprehensive investigation of the photophysical propertie s of the sunscreen agent menthyl anthranilate in various solvent systems ar e reported. Luminescence studies reveal that this ester is highly fluoresce nt (Phi(f) = 0.64 +/- 0.06 in ethanol) and has a solvent-dependent emission maximum in the range of 390-405 nm, Phosphorescence has also been detected in low-temperature glasses with an emission maximum at 445 nm and a lifeti me of 2.5 s, Kinetic UV-visible absorption measurements revealed a transien t species with absorption maxima at 480 nm and solvent-dependent lifetimes of 26-200 mu s that are attributed to the triplet state. The triplet state is efficiently quenched by oxygen, leading to the formation of singlet oxyg en in all of the solvent systems studied. The singlet-oxygen quantum yields (Phi(Delta)) determined by time-resolved near-infrared luminescence measur ements were determined to be in the range 0.09-0.12 for all systems.