An AIE‐Active Tetraphenylethylene‐Based Cyclic Urea as a Selective and Efficient Optical and Colorimetric Chemosensor for Fluoride Ions. Issue 28 (24th July 2020)

• Record Type: Journal Article
• Authors: Nadimetla, Dinesh N.; Zalmi, Geeta A.; Bhosale, Sheshanath V.
• Is Part Of: ChemistrySelect. Volume 5:Issue 28(2020)
• Page Start: 8566
• Page End: 8571
• Publication Date: 2020-07-24
• Subjects: colorimetric chemosensor -- cyclic urea -- fluoride ions -- nuclear magnetic resonance -- tetraphenylethylene; Chemistry -- Periodicals; 540.5
• DOI: 10.1002/slct.202002126
• Languages: English
• ISSNs: 2365-6549

Abstract

Abstract: Anion sensing is a very challenging and important issue in many diverse fields, including biological, medical and environmental sciences. In this paper, we report the serendipitous synthesis of a tetraphenylethylene (TPE) bearing a cyclic urea (coded as: 1 ). This easy‐to‐make, simple chemosensor shows high selectivity towards fluoride (F − ) ions. Importantly, this work demonstrates two important factors: firstly, the use of cyclic urea for ion sensing and secondly, the use of aggregation induced emission (AIE)‐ TPE signalling units. This selective fluoride sensing can be observed by the naked eye, UV‐vis absorption, fluorescence spectroscopy, and 1 H‐NMR spectroscopy. Solutions of sensor 1 are fluorescent in DMSO with fluorescence quantum yield Φ=1.3 and upon addition of fluoride ions the emission is quenched with ΦF =0.07. Notably, other anions, such as CN −, AcO −, NO3 −, H2 PO4 −, HSO4 −, I −, OH −, ClO4 −, SCN − and Cl −, do not show any quenching effect. The binding constant (K) between sensor 1 and fluoride was found to be 4.90×10 8 M −2 with a detection limit of 30 μM. We also studied AIE‐activity of 1 in THF/water mixture. As such the fluorescence quantum yield (Φ F ) of 1 in pure THF solution shown to be 0.05 % which was enhanced 22‐fold to 1.98 and 6.65 % at f w =90 and 99 %, respectively. This is clear confirmation that compound 1 is AIE active due to decreased solubility and increased molecular self‐assembly as the water fraction is increased. Abstract : Fluoride detection is a very challenging and important issue in many fields, including biological, medical and environmental sciences. We report the accidental synthesis of a tetraphenylethylene‐bearing cyclic urea moiety which shows efficient reversible chemosensing towards fluoride (F − ) ions. The binding constant (K) fluoride was found to be 4.90×10 8 M −2 with a detection limit of 30 μM. Thus, these types of urea derivatives may have real practical applications in the future.