ESIPT-Active 8-Hydroxyquinoline-Based Fluorescence Sensor for Zn(II) Detection and Aggregation-Induced Emission of the Zn(II) Complex

Abstract

A D−π–A type quinoline derivative, 2-(((4-(1, 2, 2-triphenylvinyl)phenyl)imino)methyl)quinolin-8-ol ( HL ), was synthesized and structurally characterized. The five-membered ring formed by the O–H···N hydrogen bond in HL contributed to the excited-state intramolecular proton transfer (ESIPT) behavior of HL , which was further verified by theoretical computations. Upon coordination with Zn 2+ , the hydroxyl proton in HL was removed, resulting in the inhibition of ESIPT. In the meanwhile, the formed Zn 2 L 4 complex displayed aggregation-induced emission (AIE) character in THF/H 2 O mixtures, which is conducive to the fluorescence enhancement in aqueous media. Structure analysis suggested that the origin of the AIE characteristic was attributed to restriction of intramolecular rotations along with the formation of J -aggregates. Based on ESIPT coupled with AIE, HL could recognize Zn(II) in aqueous media via an orange fluorescence turn-on mode. Benefitting from the AIE property, chemosensor HL was successfully applied to fabricate test strips for rapid sensing of Zn(II) ions.

On structural factors determining the nature of the fluorescent properties of OIHMs based on 8-hydroxyquinoline

“…The complete quenching of fluorescence in the solid 8hq is explained by the ESIPT process resulting from the formation of intramolecular O–H⋯N hydrogen bonding. 67 Therefore, creating an intermolecular ionic system capable of facilitating charge transfer between its constituent units is impossible. In the 8hq salts, the fluorescence is associated with the electron transition from lone electron pairs of the respective halide anions (chlorides or bromides) to the antibonding π orbital of 8hqH + , which further undergoes relaxation (Table 2, Fig.…”

AIE -active TPA modified Schiff base for successive sensing of Cu2+ and His via an on–off–on method and its application in bioimaging

“…4, both the DLS and SEM results revealed that the particle size reduced with increasing water content from 85% to 95%, which agreed with many reported AIE systems. 16 Fluorescence enhancement in this phase could be explicated by restricting intramolecular rotations (RIR) in the aggregates of HL . HL displayed distinct orange fluorescence in the solid state (Fig.…”

“…They have drawn much attention in the field of fluorescence sensing owing to their superior photostabilities. [16][17][18][19] Most AIEgens exhibit "always bright" or even brighter in aqueous media because of their aggregation in aqueous solutions. This optical signal amplification effect makes them suitable for constructing "turn-off" fluorescence probes.…”

ESIPT-based probes for cations, anions and neutral species: recent progress, multidisciplinary applications and future perspectives

“…Ma et al 48 synthesized D-p-A type probe 20 for Zn 2+ sensing with ESIPT-active and acceptor 8-hydroxyquinoline group and TPE group as the electron donor group (Fig. 15(i)).…”