610
F.Y. Wu et al. / Chinese Chemical Letters 23 (2012) 607–610
group, thereis oneestergroupin1 and twoestergroups in2. Thus, the electronclouddensity of N in thep-dimethylamino
moiety in 1 is larger than that in 2. The affinity of 1 toward Cu2+ is stronger than that of 2. Further, the fluorescence
quenching of 1 with the addition of Cu2+ was assumed to undergo isc by excitation from S1 to T1 state of the fluorophore,
that is deactivated by bimolecular non-radiative processes.
The fluorescence intensity change of 3 with the addition of metal ions is also studied and presented in Fig. 2b. For
most metal ions such as Hg2+, Fe3+, Pb2+, Cd2+, Ca2+, Mg2+, Co2+, except Cu2+ and Ag+, the presence of the above ions
initiates a decrease in the LE and CT fluorescence intensity of 3. The carboxyl groups in 3 possessed strong affinities
toward metal ions compared with nitrogen atom. Thus, 3 could bind with many metal ions. Obviously, the sensitivities
of 3 to Hg2+, Cd2+, and Co2+ were higher than that of Cu2+.
3. Conclusions
A simple compound, 4-dimethylaminobenzoylaminoacetic acid ethyl ester, was obtained. The total fluorescence
intensity, intensity ratio, and absorbance changes could act as indexes for the determination of Cu2+. The binding site
was assumed to play a key role in the selectivity of 1 to Cu2+.
Acknowledgments
This work is supported by Natural Science Foundation of China (No. 20965006).
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