“Off-on” aggregation-based fluorescent sensor for the detection of chloride in water

Abstract

Receptors selective for anions in aqueous media are a crucial component in the detection of anions for biological and environmental applications. Recent sensor designs have taken advantage of systems known to aggregate in solution, eliciting a fluorescent response. Herein, we demonstrate a chloride-selective fluorescent response of receptor 1+, based on our well-established class of 2,6-bis(2-anilinoethynyl)pyridine bisureas. The fluorescence intensity ratio of 1+·Cl− aggregates in water is four times larger than the next most fluorescent anion complex, 1+·ClO4−. In addition, 1H NMR spectroscopic titrations demonstrate 1+ binds chloride more strongly than other biologically relevant anions in solutions of both DMSO-d6 and 50/50 DMSO-d6/MeCN-d3.

Anion-directed self-assembly of a 2,6-bis(2-anilinoethynyl)pyridine bis(amide) scaffold

“…The large family of compounds cited above, along with 3 , are accessible by Sonogashira cross-coupling a suitable 2-ethynylaniline to a haloarene core (18-25). Amide condensation of 3 with the commercially available 3,5-dinitrobenzoyl chloride furnishes bis(amide) 2 in moderate yield (Scheme 1) after recrystallization from hot EtOAc.…”

“…We have previously reported on a family of modular arylethynyl receptors for anion binding and fluorescent sensing using 2,6-bis(2-anilinoethynyl)pyridine (18-25), -bipyridine (24, 26-28), -phenanthroline (28), -benzene (29-30), and -thiophene (24) scaffolds. The anilines are further functionalized with amide (20), sulfonamide (18, 24), or urea (19, 21-23, 25-30) groups to provide capabilities such as anion selectivity for nitrate (30) and H 2 PO 4 − (26), water solubility (25) or metal coordination (27). An example of a pyridine receptor with sulfonamide arms (e.g., 1 ) is shown in Figure 1.…”

What biologists want from their chloride reporters – a conversation between chemists and biologists

“…Acid-sensing ion channels (ASICs) that elicit inwardly rectifying cation currents have long been implicated in these signal transductions (Wemmie et al, 2013). However, acid-sensitive outwardly rectifying (ASOR) currents have also been associated with acidosis-induced cell death, albeit by a less-understood molecular mechanism (Wang et al, 2007). ASOR currents were first described in rat Sertoli cells and HEK-293 cells, and subsequently in diverse mammalian tissues (Auzanneau et al, 2003;Nobles et al, 2004).…”

Switchable Optical Probes for Simultaneous Targeting of Multiple Anions

“…[147] Recently, Johnson and his group devised a new kind of sensory system incorporating 2,6-bis(2-anilinoethynyl)pyridine bisurea as the binding motif (66). [148] The compound could adopt 'U' or 'W' conformation in water with 5-and 7-point hydrogen bonding sites respectively. The anion-dependent assembly of the probe molecules in water generated a diverse range of optical signals (green emission for Cl À , white for ClO 4 À , cyan for F À etc.)…”