A Novel L-Shaped Fluorescent Probe for AIE Sensing of Zinc (II) Ion by a DR/NIR Response.

Rosita Diana,Francesco Silvio Gentile,Barbara Panunzi,Ugo Caruso,Luigi Di Costanzo

doi:10.3390/molecules26237347

Rosita Diana, Francesco Silvio Gentile + Show 3 more

Open Access

https://doi.org/10.3390/molecules26237347

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Abstract

In the field of optical sensors, small molecules responsive to metal cations are of current interest. Probes displaying aggregation-induced emission (AIE) can solve the problems due to the aggregation-caused quenching (ACQ) molecules, scarcely emissive as aggregates in aqueous media and in tissues. The addition of a metal cation to an AIE ligand dissolved in solution can cause a “turn-on” of the fluorescence emission. Half-cruciform-shaped molecules can be a winning strategy to build specific AIE probes. Herein, we report the synthesis and characterization of a novel L-shaped fluorophore containing a benzofuran core condensed with 3-hydroxy-2-naphthaldehyde crossed with a nitrobenzene moiety. The novel AIE probe produces a fast colorimetric and fluorescence response toward zinc (II) in both in neutral and basic conditions. Acting as a tridentate ligand, it produces a complex with enhanced and red-shifted emission in the DR/NIR spectral range. The AIE nature of both compounds was examined on the basis of X-ray crystallography and DFT analysis.

Highlights

Advanced bioimaging technology and optoelectronics have encouraged the quick advancement of fluorophores with deep red/near-infrared (DR/NIR) emission, which could enhance the penetration and avoid the spectral auto-fluorescence overlapping in the living tissues [1,2,3]
Commerciallyavailable available starting products purchased from Sigma
The nitro group is widely recognized as a strong fluorescence quencher, usually lowering lowest unoccupied molecular orbital (LUMO) energy and causing the intramolecular photoinduced electron transfer (PET) process from the excited fluorophore to the electron-withdrawing nitro-aryl moiety

Summary

Introduction

Selective real-time response to metal ions attracts interests, due to their role in chemical and biological processes, and to their environmental impact [7,8]. In this context, organic fluorophores exhibiting fluorescence “turn-on” are highly sought-after tools. The addition of a metal cation to the organic AIEgen dissolved in solution can cause a “turn-on” of the fluorescence by different mechanisms, involving the formation of emissive aggregates and implying the restriction of intramolecular motions and the metal-caused blocking of nonradiative pathways [9,17,22,23]

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Conclusion