The photophysical properties of S-flurbiprofen [S-2-fluoro-alpha-methyl-4-biphenylacetic acid], a nonsteroidal anti-inflammatory drug, have been examined using steady-state and time-resolved spectroscopic techniques. The energy of its first singlet excited state is 99 kcal mol(-1). The fluorescence quantum yields and lifetimes (at 300 nm) have been determined in acetonitrile, methanol, hexane and PBS; they are in the range 0.15

The intramolecular OH ؒ ؒ ؒ interactions of the phenolic and olefinic chromophores in o-propenyl and o-butenyl phenols 1a-d in the ground and excited states have been studied by (a) ab initio Hartree-Fock calculations using the 3-21G and 6-31G** basis sets, (b) FTIR spectral measurements in the gas phase, (c) fluorescence emission studies and (d) product studies. Such interactions appear to play a key role in the photochemical behaviour of the four compounds.

Irradiation of trans-2-cinnamylphenol (2a) in hexane, under argon, led to the cis isomer 2b, 2-benzyl-2,3-dihyrobenzofuran (3), and 2-phenyl-3,4-dihydro-2if-benzopyran (4). The presence of oxygen produced a marked decrease of the 2b yield, with a parallel enhancement of the pathway leading to 3 and 4. In benzene, the cyclization process was enhanced, together with the 3:4 ratio. The latter was less favored in the presence of photosensitizers with lower singlet energies, such as toluene, methyl benzoate, or p-dichlorobenzene. In the acetone-photosensitized reaction, a clean and efficient isomerization to 2b took place. These results, together with CNDO/S calculations, suggested involvement of the phenolic or the styrenic singlets in the cyclization to 3 or 4, respectively, and the styrenic triplet (partially quenched by oxygen) in the double bond isomerization to 2b. Addition of methanol to the benzene solutions of 2a partially quenched the photocyclization. By contrast, the formation of 4 was markedly enhanced in the presence of trimethylamine or triethylamine, which were also efficient fluorescence quenchers. The above observations evidenced a new route to product 4 involving electron transfer from the tertiary amine to excited trons-2-cinnamylphenol (2a). The key step in the photocyclization must be intramolecular excited-state proton transfer (ESPT) and appears to involve «--complexes of the type I, Ha, and lib. Accordingly, direct irradiation of the o-acetyl derivative 9a resulted exclusively in isomerization to 9b, owing to chelation of the hydroxy group, which should prevent formation of the «--complexes and facilitate deactivation of the phenolic singlet, via intramolecular proton exchange.

A new 1-(9-anthryl)-4-ferrocenyl-2-aza-1,3-butadiene showing selective fluorescence enhancement upon binding to lithium cations over other alkaline cations in aqueous environment has been conveniently synthesized and characterized. [structure: see text]