Fluorescence enhancement of guests by the formation of inclusion complexes with p-tert-butylcalix[8]arene bearing polyoxyethylene chains in aqueous solution

Abstract

The reaction of p-tert-butylcalix[8]arene with ethylene oxide gives a water-soluble host compound bearing polyoxyethylene chains (C3). The polarity of the p-tert-butylcalix[8]arene cavity was determined by fluorescence measurements using pyrene (Py) as a probe. It was found that C3 has a hydrophobic cavity, with a polarity similar to that of 1-butanol, and can form host-guest complexes with Py, 1-anilino-8-naphthalenesulphonate (ANS) and N-phenyl-naphthylamine (NPN) in aqueous solution. A pronounced fluorescence enhancement of the guests on inclusion was observed. The results reveal that C3 can shield the guests from quenchers or the bulk solvent and can protect against the quenching of their excited states.