HYDROPHOBIC EFFECTS ON PHOTOCHEMICAL AND PHOTOPHYSICAL PROCESSES - EVIDENCE FOR AGGREGATION OF PERFLUOROCARBON IN AQUEOUS-ORGANIC SOLVENTS

The emission spectra and photodimerization of fluorinated alkyl 2-naph thoates (NpFCn) and 9-anthrylmethyl perfluoroalkanoates (AnFC(n)) in a queous-organic binary solvents have been investigated. The fluorescenc e spectra of NpFCn in dimethyl sulfoxide-water mixture (DMSO-H2O) are dominated by excimer emission. Addition of long chain fluorocarbon com pounds to the solution results in a reduction in the excimer emission and an enhancement of monomer emission. Selective excitation of the na phthalene moiety in the mixture solution of NpFCn and AnFC(n) leads to strong emission from AnFC(n). Photoirradiation of NpFCn yields a 'cub ane-like' photodimer with a relatively high quantum yield. All these o bservations suggest that hydrophobic interactions force molecules with long fluorocarbon chains to form aggregates in aqueous-organic binary solvents.