A coumarin-based near-infrared fluorescent probe with a large stokes shift for the sequential recognition of Ni2+ and CN- : Performance research and quantum calculation

The design and synthesis of bifunctional probes have gradually become a new research focus in the field of fluorescent probes. In this work, a reversible colorimetric and NIR fluorescent probe (Ni-3) for the sequential detection of Ni2+ and CN- was developed based on 3-benzothiazolyl-7-hydroxycoumarin. This probe featured a large Stokes shift (145 nm) and excellent anti-fatigue performance for the sequential detection of Ni2+ and CN-. Ni-3 showed a highly colorimetric response to Ni2+ and the selectivity could be distinguished by naked eyes. Besides, Ni-3 also exhibited selective NIR fluorescence response toward Ni2+ due to the paramagnetic effect and the chelation-enhanced quenching (CHEQ) effect. Additionally, the in situ generated complex [2 Ni - 3 + Ni2+] showed highly sensitive and selective sensing ability for CN- via Ni2+ displacement approach. The limit of detection toward CN- (1.29 mu M) was lower than the maximum acceptable concentration level of cyanide in drinking water (1.9 mu M) set by WHO. Furthermore, a paralleled-coordination mode between Ni - 3 and Ni2+ was proposed and demonstrated with the aid of quantum calculations.