Ion-responsive fluorescent compounds VI. Coumarin 153 linked to rigid crowns for improvement of selectivity

The photophysical and complexing properties of fluoroionophores consisting of the coumarin C153 linked to dibenzo-16-crown-5 (C153-DBC) and tribenzo-1 9-crown-6 (C153-TBC) are described in acetonitrile and ethanol. The carbony l group of the coumarin moiety is in direct interaction with a bound cation . The selectivity of these compounds for a given alkali or alkaline earth m etal ion was found to be better than that of previously reported crowned co umarins owing to the rigidity of dibenzo- and tribenzocrowns. In acetonitri le, a very high selectivity for Ca2+ versus Mg2+ has been found. In ethanol , C153-DBC is selective for Na+ and C153-TBC is selective for K+, as expect ed from the relative size of the crown cavity. (C) 2000 Elsevier Science S. A. All rights reserved.