Benzothiazolylhydrazone-Based Turn-on Fluorescent Probe for Detecting Cu2+: S-donor as a Cu2+-induced Fluorescence Quenching Inhibitor

Qiao Li,Yang Zhao,Enju Wang

doi:10.17344/acsi.2020.6324

Abstract

The fluorescent turn-on detection of metal ions is highly desirable for public health and environmental security. Herein, we report a rationally designed fluorescent probe (1) for the detection of Cu2+ synthesized by integrating 2-hydrazinylbenzothiazole with 3-acetyl-7-hydroxycoumarin. The probe alone is non-fluorescent due to the isomerization of C=N in the excited state. The addition of Cu2+ can cause a delayed fluorescence enhancement. A comparative study of 1 and its analogues indicated that the turn-on fluorescence response was thanks to the sulfur atom coordinating to Cu2+. The response delay of 1 in sensing Cu2+ was ascribed to the gradual transition from N-coordination to S-coordination (N and S in thiazole moiety). The proposed new function of S-donor would provide a new approach for the turn-on fluorescence sensation of Cu2+.

Highlights

Copper is an essential trace element important for the function of enzymes
During the course of our ongoing efforts to develop fluorescent probes for mental ions[9,10,11], we have firstly found that some probes containing S-donor show turn on fluorescence responses to Cu2+, and so the S-donor may play an important role in protecting from Cu2+-induced fluorescence quenching.[12,13,14]
With the compound 1 in hand, its fluorescence responds to various metal ions, including Ba2+, Ca2+, Mg2+, K+, Al3+, Na+, Zn2+, Ag+, Fe3+, Mn2+, Cd2+, Ni2+, Pb2+, Co2+, Cr3+, Hg2+ and Cu+, were examined

Summary

Introduction

Copper is an essential trace element important for the function of enzymes. It plays a pivotal role in cell physiology as a catalytic cofactor in the cellular redox reactions. The function of S-donor in protecting from fluorescence quenching was affirmed by control experiments using the analogues of 1 (2a and 2b in Scheme 1). Besides preventing from fluorescence quenching, S-donor should be helpful for the improvement of Cu2+-selective binding.[15]

Experimental

Results and Discussion

Conclusion