Time‐resolved spectroscopic and density functional theory investigation of the photochemistry of suprofen

The photochemistry of suprofen (SPF) was investigated by femtosecond transient absorption (fs‐TA), resonance Raman (RR) and nanosecond time‐resolved resonance Raman (ns‐TR 3 ) spectroscopic methods to gain additional information so as to better elucidate the possible photochemical reaction mechanism of suprofen in several different solvents. In neat acetonitrile (MeCN), the fs‐TA and ns‐TR 3 experimental data indicated that the lowest lying excited singlet state S 1 (nπ*) underwent an efficient intersystem crossing process (ISC) to the excited triplet state T 3 (ππ*), followed by an internal conversion (IC) process to T 1 (ππ*). In the aqueous solution, a triplet biradical species ( 3 ETK‐1) was obtained as the product of a decarboxylation process from triplet suprofen anion ( 3 SPF − ) and the reaction rate of the decarboxylation process was determined by the concentration of H 2 O. A protonation process for 3 ETK‐1 leads to formation of a neutral species ( 3 ETK‐3) that was directly observed by ns‐TR 3 spectra, then this 3 ETK‐3 species decayed via ISC process to generate final product. Copyright © 2014 John Wiley & Sons, Ltd.