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-TR3) 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-TR3 experimental data indicated that the lowest lying excited singlet state S-1 (n*) underwent an efficient intersystem crossing process (ISC) to the excited triplet state T-3 (*), followed by an internal conversion (IC) process to T-1 (*). In the aqueous solution, a triplet biradical species ((ETK)-E-3-1) was obtained as the product of a decarboxylation process from triplet suprofen anion ((SPF-)-S-3) and the reaction rate of the decarboxylation process was determined by the concentration of H2O. A protonation process for (ETK)-E-3-1 leads to formation of a neutral species ((ETK)-E-3-3) that was directly observed by ns-TR3 spectra, then this (ETK)-E-3-3 species decayed via ISC process to generate final product. Copyright (c) 2014 John Wiley & Sons, Ltd.