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 alpha-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 appearing during the irradiation of the molecule was due to a Norrish-II reaction (beta-cleavage), which induced the release of the BM-DBM enol form and 1-decene. Then, we established a kinetic model for the photochemistry of C10-DBM and fitted the variation of UV absorption spectra to confirm the proposed mechanism.

Optical and Electron Paramagnetic Resonance Studies of the Excited States of 4-tert-Butyl-4′-Methoxydibenzoylmethane and 4-tert-Butyl-4′-Methoxydibenzoylpropane

“…8 They reported that the photochemical -cleavage reaction of C10-BM-DBM possessing γ-hydrogen atoms produces the enol form of BM-DBM and 1-decene by the Norrish-II mechanism. As is known, this reaction is efficient if the T 1 state has an nπ* character.…”

Tautomeric and conformational properties of dibenzoylmethane, C6H5–C(O)–CH2–C(O)–C6H5: gas-phase electron diffraction and quantum chemical study

“…Because of antitumor and anti-inflammatory effects, dibenzoylmethane and its derivatives have attracted attention considering their potential use as a chemopreventive agents [2]. Furthermore, powerful sunscreen activity of DBM derivatives allows to use these compounds in the cosmetic industry as sunscreen agents [3,4]. The keto-enol tautomerization of b-diketones has attracted great interest and has been investigated extensively.…”

Construction of reversible hydration–dehydration system by a model compound and a novel polymer bearing vicinal tricarbonyl structure

“…IR and UV–vis spectra of poly (VDBM) are shown in Figures S4 and S5 (in Supporting Information), respectively. In the UV–vis spectrum, a strong absorption with maximum at around 350 nm was observed to confirm the presence of the enol form of 1,3‐diketone moiety 25. The temperatures for 5 and 10% weight loss ( T d5 and T d10 ) of poly(VDBM) were estimated by thermal gravimetric analysis (TGA) to be 328 and 356 °C, respectively.…”