Fluorescence of crowned butadienyl dye and its metal complexes

The absorption and fluorescence spectra of complexes of butadienyl dye (1) with lithium, sodium, magnesium, and calcium cations in MeCN were investigated. The addition of Li, Na, Mg, and Ca perchlorates to the solution of dye 1 in acetonitrile results in a significant (up to 5900-cm(-1)) short-wavelength shift of the absorption spectrum and a small (about 200-cm(-1)) short-wavelength shift of the fluorescence spectrum. The recoordination reaction in metal complexes of 1 takes place by intramolecular mechanism. The fluorescence quantum yield of 1Li(+), 1Na(+), and 1Ca(2 divided by) is approximately two times higher than that for 1. It was supposed that Li+ cation coordinates predominantly with oxygen atoms of macrocycle and, hence, influences weakly macrocycle nitrogen atoms conjugated with a molecule pi-system.