Title:Efficient Fluorescent Detection of Mercuric Ions Based on 2-Thienyl
benzimidazole/Cucurbit[7]uril Complexes
Volume: 2
Issue: 2
Author(s): Marieh B. Al-Handawi, John P. Graham, Hany A. Eldeab and Na'il Saleh*
Affiliation:
- Department of Chemistry, College of Science, United Arab Emirates University, Al Ain 15551, United Arab Emirates
Keywords:
Mercuric ions recovery, host-guest chemistry, fluorescence, static quenching, DFT calculations, host-induced pKa shifts.
Abstract:
Aims and objective: 2-Thienylbenzimidazole (TBI)/cucurbit[7]uril (CB7) host/guest
complex was used to significantly improve the detection of Hg2+ in water samples.
Methods: The unique mechanism of the sensing process is based on the binding of CB7 host to TBI
guest. The host-guest complexation was confirmed by UV-visible absorption, time-resolved fluorescence,
and proton NMR spectroscopy. The complexations of TBI and TBI/CB7 with Hg2+ ions in
solid-state were confirmed by FTIR, mass, and TGA. The most stable structures were unfolded by
DFT calculations.
Results: In an aqueous solution, a five-fold higher stability constant of the protonated TBIH+/CB7
complex was observed when compared to the neutral TBI/CB7 complex as manifested in an increase
in pKa values by ~ 0.5 unit in an excited state. The static fluorescence quenching of TBI on
binding to Hg2+ ions was significantly enhanced in the presence of CB7.
Conclusion: Macrocycles are useful additives for the highly sensitive recovery of mercury ions in
water samples.