Hydrophobic effects on photochemical and photophysical processes: evidence for aggregation of perfluorocarbon in aqueous–organic solvents

Abstract

The emission spectra and photodimerization of fluorinated alkyl 2-naphthoates (NpFC_n) and 9-anthrylmethyl perfluoroalkanoates (AnFC_n) in aqueous–organic binary solvents have been investigated. The fluorescence spectra of NpFC_n in dimethyl sulfoxide–water mixture (DMSO–H₂O) are dominated by excimer emission. Addition of long chain fluorocarbon compounds to the solution results in a reduction in the excimer emission and an enhancement of monomer emission. Selective excitation of the naphthalene moiety in the mixture solution of NpFC_n and AnFC_n leads to strong emission from AnFC_n. Photoirradiation of NpFC_n yields a ‘cubane-like’ photodimer with a relatively high quantum yield. All these observations suggest that hydrophobic interactions force molecules with long fluorocarbon chains to form aggregates in aqueous–organic binary solvents.