Intramolecular photodimerization of 2-naphthoates: successful application of hydrophobic forces in the preparation of large-ring compounds

Abstract

The fluorescence spectra and photodimerization of polymethylene bis(2-naphthoate)(N – M_n– N) in aqueous organic binary mixed solvents have been studied. Strong intramolecular excimer fluorescence was observed, suggesting that hydrophobic interactions force polymethylene chains to self-coil. Photoirradiation of these solutions resulted in intramolecular dimerization of 2-naphthoate groups to give ring-closure products. The quantum yields for the photodimerization are significantly greater than those in organic solvents. This work provides an example of the application of hydrophobic interactions in expediting the formation of macrocyclic entities.