Coordination-Directed Stacking and Aggregation-Induced Emission Enhancement of the Zn(II) Schiff Base Complex

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• 作者：Dan Wang ; Shu-Mu Li ; Jian-Quan Zheng ; Duan-Yang Kong ; Xiang-Jun ZhengDe-Cai Fang ; Lin-Pei Jin
• 刊名：Inorganic Chemistry
• 出版年：2017
• 出版时间：January 17, 2017
• 年：2017
• 卷：56
• 期：2
• 页码：984-990
• 全文大小：463K
• ISSN：1520-510X

文摘

2-(Trityliminomethyl)-quinolin-8-ol (HL) and its Zn(II) complex were synthesized and characterized by single-crystal X-ray diffraction. HL is an unsymmetrical molecule and coordinated with Zn(II) ion to form ZnL<sub>2sub> in the antiparallel-mode arrangement via Zn—O (hydroxyl group) and Zn—N (quinoline ring) of HL. A high degree of ZnL<sub>2sub> molecules ordering stacking is formed by the coordination bonds and intermolecular π–π interactions, in which head-to-tail arrangement (J-mode stacking) for L<sup>–sup> is found. HL is nonfluorescent and ZnL<sub>2sub> is weakly fluorescent in THF. The fluorescence emission of ZnL<sub>2sub> enhances in THF/H<sub>2sub>O as H<sub>2sub>O% (volume %) is above 60% and aggregates particles with several hundred nanometers are formed, which is confirmed by DLS data and TEM images. The J-aggregates stacking for L<sup>–sup> in ZnL<sub>2sub> results in aggregation-induced emission enhancement (AIEE) for ZnL<sub>2sub> in THF/H<sub>2sub>O. Theoretical computations based on B3LYP/6-31G(d, p) and TD-B3LYP/6-31G(d, p) methods were carried out. ESIPT is the supposed mechanism for fluorescent silence of HL, and fluorescence emission of ZnL<sub>2sub> is attributed to the restriction of ESIPT process. The oscillator strength of ZnL<sub>2sub> increases from 0.017 for monomer to 0.032 for trimer. It indicates that a high degree of ZnL<sub>2sub> molecules ordering stacking in THF/H<sub>2sub>O is of benefit to fluorescence enhancement. HL is an ESIPT-coupled AIEE chemosensor for Zn(II) with high selectivity and sensitivity in aqueous medium. HL can efficiently detect intracellular Zn(II) ions because of ESIPT-coupled AIEE property of ZnL<sub>2sub> in mixed solvent.