Cation Binding of Benzo Crown Ethers in acetonitrile using Fluorescence Spectroscopy, Part II

Abstract

The effects of Na+, K+, Li+ and Mg2+ cations on the fluorescence spectra of benzo[12]Crown-4, benzo[15]Crown-5, and benzo[18]Crown-6 were investigated in dry acetonitrile. The alkali cation coused the complexation enhanced quenched fluorescence (CEQF) by increasing the fluorescence quenching rates of the cationic fluoroionophores. The 1:1 stoichiometry of ion association constants, lnKa have been obtained. The results were ruled out by compatibility of cationic radii and macrocycle size. The order of lnKa found for benzo[15]crown-5 was Mg+>Na+>Li+ for the cations and the Na+>Li+ was found for benzo[18]crown-6. The most of the cations have slight effects on the fluorescence spectra of benzol[12]crown-4 in acetonitrile.