New fluorescent ionophores containing the 1-naphthylacetanilide moiety based on oligo-ethylene oxide (14 and 15) have been synthesized, and their photochemical behaviors have been studied. In the absence of a metal ion, the 1-naphthylacetanilide moiety showed a weak fluorescence emission (fluorescence “off state”). However, complexation with Ca2+ induced a large enhancement effect on the fluorescence intensity of 14 and 15 from the naphthalene ring (fluorescence “on” state). This behavior can be explained in terms of a similar twisted intramolecular charge-transfer relaxation mechanism. Such “off-on” fluorescence responses of 14 and 15 provide the digital detection of alkaline earth metal ions.
2006 by The Japan Society for Analytical Chemistry