Selective Fluorescence Turn‐On Sensing of Phosphate Anion in Water by Tetraphenylethylene Dimethylformamidine

Abstract

A tetraphenylethylene (TPE) derivative bearing two dimethylformamidine units was synthesized. The dihydrogen chloride salt of this TPE derivative was soluble in water and showed almost no emission. By addition of phosphate anions, the dihydrogen chloride salt could be transformed into the monohydrogen chloride salt, which was barely soluble and emitted strong fluorescence through aggregation‐induced emission (AIE), while many other anions could not bring about a fluorescence enhancement. Meanwhile, the dihydrogen chloride salt and monohydrogen chloride salt could be reversible transformed by addition of acid and base alternately in the presence of phosphate anion, which led to fluorescence turn‐on and turn‐off. Therefore, the TPE dimethylformamidine holds potential for selectively sensing phosphate anions in water and use as fluorescence pH switch. This study provided a new approach to AIEgen sensors by using formamidine groups.

Halogen Bonding Tetraphenylethene Anion Receptors: Anion‐Induced Emissive Aggregates and Photoswitchable Recognition

“… [13] TPE derivatives have also received significant interest in the development of supramolecular sensors which couple a luminescent response with molecular recognition events. [ 14 , 15 , 16 , 17 , 18 ] However, the considered employment of TPE‐derivatives within supramolecular host systems remains scarce,[ 19 , 20 , 21 , 22 ] with the overwhelming majority of reported examples reliant on irreversible chemical modification of the AIEgen core to sense the guest species. [23] …”

Recent Advances in Aggregation-Induced Emission Chemosensors for Anion Sensing

“…D2 ligand was found to selectively sense both PO 4 3− and HPO 4 2− anions by forming a complex with an anion-to-ligand ratio of 4:2 (Scheme 8), thereby triggering an enhancement of blue emission (27- and 20-fold, respectively) due to RIR mechanism of TPE, i.e., anion-coordination-induced emission [101]. More recently, Zheng et al reported selective fluorescence turn-on sensing of PO 4 3− in water by TPE-derivative D3 [102]. The emission response is due to the fact that PO 4 3− abstracts a proton from D3.2HCl to form D3.HCl , which then forms an insoluble hydrogen bond network with HPO 4 2− (Scheme 8) [102].…”

“…More recently, Zheng et al reported selective fluorescence turn-on sensing of PO 4 3− in water by TPE-derivative D3 [102]. The emission response is due to the fact that PO 4 3− abstracts a proton from D3.2HCl to form D3.HCl , which then forms an insoluble hydrogen bond network with HPO 4 2− (Scheme 8) [102]. This sensing process is highly reversible, with the addition of HCl resulting in the regeneration of D3 .…”

“…Chemical structures of AIE-based sensors for the phosphate sensing ( D1 – D4 ) and their sensing mechanisms. Chemical schemes for D2 and D3 reproduced with permission from [101,102]. Copyright 2014 and 2019, Wiley-VCH Verlag GmbH & Co. KGaA.…”

Halogen Bonding Tetraphenylethene Anion Receptors: Anion‐Induced Emissive Aggregates and Photoswitchable Recognition

“…TPE derivatives have also received significant interest in the development of supramolecular sensors which couple a luminescent response with molecular recognition events [14–18] . However, the considered employment of TPE‐derivatives within supramolecular host systems remains scarce, [19–22] with the overwhelming majority of reported examples reliant on irreversible chemical modification of the AIEgen core to sense the guest species [23] …”