Photochemical Behavior of a New Long-chain UV Absorber†, Derived from 4-tert-Butyl-4′-Methoxydibenzoylmethane¶

Abstract A new UV filter, the 1-(4-tert-butylphenyl)-2-decanyl-3-(4′-methoxyphenyl)-propane-1,3-dione, called C10-DBM, was prepared by grafting a 10-carbon aliphatic chain to the α-carbonyl position of 4-tert-butyl-4′-methoxydibenzoylmethane (BM-DBM), a well-known and often used UV filter. The UV-A absorption efficiency of organic solutions containing the new filter was tested and compared with identical solutions containing BM-DBM with or without irradiation (xenon lamp). The originality of this new filter is that its UV-A absorbance appeared during irradiation of the molecule. Although the molar absorption coefficient of C10-DBM in the UV-A domain was lower than that of BM-DBM, the solutions absorption exhibited a much more photostable behavior under irradiation. In this study, we first demonstrated that C10-DBM was a precursor of BM-DBM (enol isomer) by means of high-performance liquid chromatography followed by mass spectrometry. Indeed, we showed that the UV-A absorption of C10-DBM solutions appearin...