A novel salicylaldehyde Schiff-base-functionalized 1,8-naphthalimide luminophore with controllable aggregation/solid/film fluorescence and reversible acid/base stimuli-responsive film fluorescence

IF 4.7 2区化学 Q2 CHEMISTRY, PHYSICAL Journal of Molecular Structure Pub Date : 2025-07-05 Epub Date: 2025-02-27 DOI:10.1016/j.molstruc.2025.141888

Mingguang Zhu , Jinghui Zeng , Xinyu Ye , Jiali Hu , Yuanbin Wu , Meihui Chen , Donghong Xie , Huihua Gong , Zhenye Wang , Liu Yang , Yaohui You

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Abstract

In the quest to engineer multifunctional fluorescent materials, 1,8-naphthalimide (NPI) and salicylaldehyde Schiff base molecules were considered as the promising fluorophores because of their fascinating vistas. Herein, from 1,8-naphthalic anhydride precursor, a novel salicylaldehyde Schiff-base-functionalized 1,8-naphthalimide (NPI) luminophore, where NPI core and salicylaldehyde Schiff base were judiciously integrated through a flexible methylene spacer, was elaborately designed and successfully synthesized in a high yield of 90 %. The structure-property relationship was meticulously lucubrated by comparing the photophysical properties of it and its analogues. Mainly, it enjoyed excited-state intramolecular proton transfer (ESIPT) process upon photoexcitation in solution state. Interestingly, it showed the vividly fluorochromic behaviours at the unimolecular level in the aggregation/solid/film states. Specifically, it exhibited multiple self-assembly stages in the proportionally mixed solutions of THF/H₂O with different water fractions (f_w), accompanying fluorescence transitions from aggregation-induced emission (AIE)+ESIPT-based emission to J-type aggregation-induced emission to H-type aggregation caused quenching. Moreover, its film fabricated by casting EtOH solution (10⁻⁵ M) onto the glass slide displayed thickness-dependent fluorescence colour changes and reversible acid/base stimuli-responsive fluorescence. Furthermore, its solid obtained by crystallization in the EtOH/water (1/1, v/v) mixtures (approximately 10⁻² M) exhibited the reversible mechanochromic luminescence. This work not only realized efficient and controllable aggregation/solid/film fluorescence from a salicylaldehyde Schiff-base-functionalized 1,8-naphthalimide luminophore but also provided a strategy for constructing NPI-based smart fluorescent materials.

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一种新型水杨醛席夫碱功能化1,8-萘酰亚胺发光团，具有可控制的聚集/固体/膜荧光和可逆的酸/碱刺激响应膜荧光

在设计多功能荧光材料的过程中，1,8-萘酰亚胺（NPI）和水杨醛希夫碱分子被认为是有前途的荧光团，因为它们具有迷人的前景。本文以1,8-萘酸酐前体为原料，精心设计并合成了一种新型的水杨醛席夫碱功能化的1,8-萘酰亚胺发光基团，该发光基团通过柔性亚甲基间隔剂巧妙地将NPI核与水杨醛席夫碱相结合，收率高达90%。通过比较其光物理性质，仔细研究了其结构-性能关系。主要表现为溶液态光激发后发生激发态分子内质子转移（ESIPT）过程。有趣的是，它在聚集/固体/膜态的单分子水平上表现出生动的荧光行为。具体来说，它在不同水分数（fw）的THF/H2O比例混合溶液中表现出多个自组装阶段，伴随着荧光从聚集诱导发射(AIE)+基于esipt的发射到j型聚集诱导发射到h型聚集猝灭的转变。此外，通过将EtOH溶液（10−5 M）浇铸到玻片上制备的膜显示出厚度依赖的荧光颜色变化和可逆的酸/碱刺激响应荧光。此外，在EtOH/水（1/1,v/v）混合物（约10−2 M）中结晶得到的固体表现出可逆的机械致变色发光。本研究不仅实现了水杨醛席夫碱功能化1,8-萘酰亚胺发光团高效可控的聚集/固体/薄膜荧光，而且为构建基于npi的智能荧光材料提供了一种策略。

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来源期刊

Journal of Molecular Structure 化学-物理化学

CiteScore

7.10

自引率

15.80%

发文量

2384

审稿时长

45 days

期刊介绍： The Journal of Molecular Structure is dedicated to the publication of full-length articles and review papers, providing important new structural information on all types of chemical species including: • Stable and unstable molecules in all types of environments (vapour, molecular beam, liquid, solution, liquid crystal, solid state, matrix-isolated, surface-absorbed etc.) • Chemical intermediates • Molecules in excited states • Biological molecules • Polymers. The methods used may include any combination of spectroscopic and non-spectroscopic techniques, for example: • Infrared spectroscopy (mid, far, near) • Raman spectroscopy and non-linear Raman methods (CARS, etc.) • Electronic absorption spectroscopy • Optical rotatory dispersion and circular dichroism • Fluorescence and phosphorescence techniques • Electron spectroscopies (PES, XPS), EXAFS, etc. • Microwave spectroscopy • Electron diffraction • NMR and ESR spectroscopies • Mössbauer spectroscopy • X-ray crystallography • Charge Density Analyses • Computational Studies (supplementing experimental methods) We encourage publications combining theoretical and experimental approaches. The structural insights gained by the studies should be correlated with the properties, activity and/ or reactivity of the molecule under investigation and the relevance of this molecule and its implications should be discussed.