Spectroscopic and theoretical studies of the excited states of fenofibric acid and ketoprofen in relation with their photosensitizing properties

A study of the different excited states of fenofibric acid (FB) and ketopro fen (KP), two aromatic acids derived from benzophenone, has been achieved b y absorbance and low temperature emission spectroscopy to take into account their photochemical reactivity and their in vitro and in vivo photosensiti zing properties. These experiments have shown that FB mainly exhibits a sin glet-singlet transition of pi pi* character, the n pi* transition being und etectable, in contrast with KP. In phosphate buffer as well as in ethanol o r in isopentane, the lowest triplet excited state of fenofibric acid appear s to be, as for KP, an n pi* triplet state with characteristics similar to those of benzophenone. These assignments were fairly well supported by theo retical calculations performed at the TD-DFT level. The transient formation of a ketyl radical detected in hash photolysis experiments performed in et hanol confirms that the photochemical reactivity of FB towards hydrogen abs traction in ethanol is typically that of an n pi* triplet state. The good a greement between the experimental and theoretical results is discussed with respect to those previously obtained by ether theoretical methods.