The influence of hydrogen bonding on the photoinduced interaction of 9anthracenecarboxylic acid and xanthene dye esters

The interaction of 9-anthracenecarboxylic acid with xanthene esters in chloroform solution was studied using emission spectra, fluorescence lifetime, IR spectra and 1H NMR spectra. The results show that there exists both dynamic and static fluorescence quenchings. Dynamic quenching is a diffusion controlled process while static quenching is affected by hindrance of substituents adjacent to the hydroxyl groups in the xanthene moiety. Thus an intermolecular hydrogen bond interaction model between the hydroxyl groups of xanthene dye esters and 9-anthracenecarboxylic acid is proposed, and this is supported by IR and 1H NMR spectra data. The binding constant for fluorescein and 9-anthracene carboxylic acid is 982 M-1, while it is only 81 M-1 for the eosin ester and 9-anthracenecarboxylic acid. No apparent static interaction was observed in methanol solution. This may be explained in terms of hydrogen bonding between the hydroxyl group of methanol to anthracenecarboxylic acid, being in competition with that from the hydroxy group of the xanthene dye esters to 9anthracene carboxylic acid.