An Ultrafast Molecular‐Rotor‐Based Fluorescent Turn‐On Sensor for the Perrhenate Anion in Aqueous Solution

Abstract

Devising sensors for the perrhenate anion in aqueous media is extremely challenging, and has seldom been reported in the literature. Herein, we report a fluorescence turn‐on sensor for the perrhenate anion in aqueous media based on the aggregation‐induced emission of a popular ultrafast molecular rotor dye, Thioflavin‐T. The selective response towards the perrhenate anion has been rationalized in terms of matching water affinity, with the weakly hydrated perrhenate anion spontaneously forming a contact ion pair with the weakly hydrated ultrafast molecule‐rotor‐based organic cation, Thioflavin‐T, which in turn leads to an aggregate assembly that provides a fluorescence turn‐on response towards perrhenate. The sensing response of Thioflavin‐T has been found to be quite selective towards the perrhenate anion when tested against anions that are ubiquitously present in the environment, such as chloride, nitrate, and sulfate anions. The formation of self‐assembled Thioflavin‐T aggregates has also been investigated by time‐resolved emission and temperature‐dependent measurements.

Advances in fluorescent and colorimetric sensors for anionic species

“…Singh et al have reported the use of thioflavin-T 45 (Fig. 37a) as a selective fluorescence turn-on chemosensor for perrhenate anion (ReO4 − ) recognition in water [102]. The authors ascribed the selectivity of the molecular rotor 45 towards perrhenate in aqueous solution to the contact ion pair interaction between the weakly hydrated perrhenate ion and compound 45.…”

“…The authors ascribed the selectivity of the molecular rotor 45 towards perrhenate in aqueous solution to the contact ion pair interaction between the weakly hydrated perrhenate ion and compound 45. This resulted in aggregation, assembly formation, and therefore an enhancement in fluorescence [102]. Upon addition of other anions such as sulfate, chloride and nitrate, to an aqueous solution of compound 45, no fluorescence response was recorded even at high anion concentrations (10 equiv.)…”

Recent Advances in Aggregation-Induced Emission Chemosensors for Anion Sensing

“…Due to its danger, access to pertechnetate for research purpose is unfortunately restricted, which prompted Singh et al to devise a chemosensor for the detection of a chemically-similar but non-radioactive oxoanion, perrhenate (ReO 4 − ), to mimic potential environment-sensing of pertechnetate. Singh et al reported thioflavin-T ( F2 ) to sense perrhenate via the formation of contact ion pairs, which resulted in aggregation and hence the turning-on of emission [121]. An enhancement of emission peaking at 520 nm indeed arose from the aggregation of F2 with perrhenate in water, which gave a detection limit of 260 μM.…”

“…Therefore, the sensing of L-lactate, an important biomarker, is crucial. Ng et al developed a sensitive and selective detection method for sensing L-lactate involving TPE-boronic ester derivative F3 and L-lactate oxidase (LOx), for a duration of 20–60 min [121]. LOx is an enzyme that converts L-lactate to pyruvate in the presence of oxygen.…”

Molecular Rotor based on an Oxidized Resorcinarene

“…[30][31][32] Rotor activity signified by variation in fluorescence output wavelength of certain molecule types can be harnessed to reveal local viscosity in biological membranes or models thereof, [33][34][35][36] while rotation rate modulation also signalled by fluorescence emission characteristics can also be used to indicate the presence of analytes. [37][38][39] Molecules having several proximal component moieties are suitable archetypes of rotors because of intramolecular interactions that govern the mutual motion of substituents. However, although macrocycles such as porphyrins [40][41][42] and calixarenes 43 or highly-substituted hydrocarbons 44,45 have been extensively used, resorcinarenes [46][47][48][49][50] have hardly been studied for this purpose, and in cases where they have been used, they are usually operating only as a supramolecular host where an encapsulated guest rotates.…”