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Abstract

Zinc ions play an important role in many biological processes in human body [1]. To
recognize Zn2+ over other metal ions, two novel EuDO3A-based complexes EuL1-2
(DO3A – 1,4,7,10-tetraazacyclododecane-1,4,7-tricarboxylic acid) appended with the
tyrosine as chromophore and dipicolylamine as recognition moiety were developed as
suitable luminescent sensors. Without Zn2+, only weak luminescence of each complex
was observed due to the luminescence quenching by the photoinduced electron transfer
mechanism. After addition of Zn2+, both probes displayed large increase in the Eucentered
luminescent emission; in specific, the emission intensity reached 7-fold and
5-fold enhancement at 617 nm for EuL1 and EuL2, respectively (Figure 1). The ion
selectivity experiments demonstrated specificity of our probes toward Zn2+ over
other metal ions. Two additional complexes EuL3-4 without a
dipicolylamine-moiety were synthesized as references. Both of them did not show
obvious luminescent enhancement for any of the studied metal ions, showing the
essential role of the dipicolylamines for the recognition of Zn2+. The induced emission
changes of the Eu3+ allow precise quantitative analysis of this ion, establishing these
lanthanide-based complexes as useful chemosensors for potential biological applications.