SPECTROSCOPIC STUDY OF CROWN-ETHERS CONTAINING FLUORESCENT SUBSTITUENTS

The selective complex formation of two new benzo[ls]crown-5 ethers wit h alkali ions has been studied by fluorescence spectroscopy. The crown ether BI-B15C5 contains benzimidazole as a fluorescent substituent wh ereas BPY-B15C5 is a 2-benzopyrylium perchlorate derivative. The long- wavelength absorption bands of both crown ethers show a hypochromic an d a hypsochromic shift after complexation with lithium or sodium perch lorate in acetonitrile. The fluorescence intensity of BI-B15C5 decreas es but the shape of the fluorescence excitation and emission spectra d oes not change. On the other hand, the fluorescence intensity of BPY-B 15C5 increases with complexation and the emission maximum shifts towar ds shorter wavelengths. (C) 1997 Elsevier Science B.V.