title: Coordination-Directed Stacking and Aggregation-Induced Emission Enhancement of the Zn(II) Schiff Base Complex.
abstract: 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 ZnL2in the antiparallel-mode arrangement via Zn-O (hydroxyl group) and Zn-N (quinoline ring) of HL. A high degree of ZnL2molecules ordering stacking is formed by the coordination bonds and intermolecular π-π interactions, in which head-to-tail arrangement (J-mode stacking) for L-is found. HL is nonfluorescent and ZnL2is weakly fluorescent in THF. The fluorescence emission of ZnL2enhances in THF/H2O as H2O% (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-in ZnL2results in aggregation-induced emission enhancement (AIEE) for ZnL2in THF/H2O. 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 ZnL2is attributed to the restriction of ESIPT process. The oscillator strength of ZnL2increases from 0.017 for monomer to 0.032 for trimer. It indicates that a high degree of ZnL2molecules ordering stacking in THF/H2O 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 ZnL2in mixed solvent.
authors.affiliation: Beijing Key Laboratory of Energy Conversion and Storage Materials, College of Chemistry, Beijing Normal University , Beijing 100875, P. R. China.
authors.forename: Dan
authors.initials: D
authors.lastname: Wang
authors.affiliation: Key Laboratory of Green Printing, Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, P. R. China.
authors.forename: Shu-Mu
authors.initials: SM
authors.lastname: Li
authors.affiliation: Beijing Key Laboratory of Bioactive Substances and Functional Foods, Beijing Union University , Beijing 100191, P. R. China.
authors.forename: Jian-Quan
authors.initials: JQ
authors.lastname: Zheng
authors.affiliation: Beijing Key Laboratory of Energy Conversion and Storage Materials, College of Chemistry, Beijing Normal University , Beijing 100875, P. R. China.
authors.forename: Duan-Yang
authors.initials: DY
authors.lastname: Kong
authors.affiliation: Beijing Key Laboratory of Energy Conversion and Storage Materials, College of Chemistry, Beijing Normal University , Beijing 100875, P. R. China.
authors.forename: Xiang-Jun
authors.identifier: http://orcid.org/0000-0002-7720-9000
authors.initials: XJ
authors.lastname: Zheng
authors.affiliation: Beijing Key Laboratory of Energy Conversion and Storage Materials, College of Chemistry, Beijing Normal University , Beijing 100875, P. R. China.
authors.forename: De-Cai
authors.initials: DC
authors.lastname: Fang
authors.affiliation: Beijing Key Laboratory of Energy Conversion and Storage Materials, College of Chemistry, Beijing Normal University , Beijing 100875, P. R. China.
authors.forename: Lin-Pei
authors.initials: LP
authors.lastname: Jin