物理化学学报2020，Vol.36Issue(9)：117-123,7.DOI:10.3866/PKU.WHXB201912002
氧化还原对Lindqvist型多金属氧簇复合物自组装的动态调控
Redox-Regulated Dynamic Self-Assembly of a Lindqvist-Type Polyoxometalate Complex
摘要
Abstract
Dynamic regulation of self-assembly is of vital importance in chemistry,biology and material science thanks to its great potential for development of smart materials and devices.Polyoxometalates (POMs) are a class of functional inorganic nanoclusters,which has become one of the excellent building blocks for supramolecular self-assemblies,especially when covalently or non-covalently modified by organic species.As typical stimuli-responsive functional clusters,the POMs could be photochemically or electrochemically reduced to mixed-valence states,of which the structural integrity remains even after encountering stepwise multi-electron redox process.The intriguing photochromism of the POMs in different states exhibits distinct photophysical properties,which motivates us to exploit the dynamic self-assemblies of POM-based complexes.The divalent Lindqvisttype hexamolybdate cluster[Mo6O19]2-is one of the least negative-charged POMs,which is the ideal building blocks to construct novel assembly structures.Based on this motivation,herein,a single chain surfactant-encapsulated polyoxometalats (POM) complex (ODTA)2[Mo6O19]was prepared by simple counterion replacement of Lindqvist-type (TBA)2[Mo6O19]with octadecyltrimethylammonium (ODTA) in acetonitrile solution.The structure of the POM complex was confirmed by 1H nuclear magnetic resonance (NMR),Fourier transform infrared (FT-IR) spectroscopy,thermogravimetric analysis (TGA) and elemental analysis.The solution of complex (ODTA)2[Mo6O19]in the mixed solvents of acetonitrile and isopropanol with the volume ration of 4 to 1 exhibited reversible photochromism upon altemate UV light irradiation and air exposure.Upon UV light irradiation,the light yellow transparent solution of (ODTA)2[Mo6O19]turned into blue quickly.The new broad absorption band appearing at ca.751 nm assigned to the Mov → MoⅥ intervalence charge-transfer (IVCT) transition,indicated the formation of reduced POM,as revealed by UV-Vis absorption spectra.After exposed to air,the blue solution was bleached.The alternate photochromism could be conducted for multiple cycles.Helical self-assembled morphology of (ODTA)2[Mo6O19]was formed in acetonitrile/isopropanol,characterized by scanning electron microscope (SEM),transmission electron microscopy (TEM) and X-ray diffraction (XRD) methods.More interestingly,morphology transformation of the complex from helical strips to spherical assemblies occurred accompanied by photochromism occurrence.The morphology evolution during the photochromism process experienced from shortened helical strips through sea urchin-like aggregates to spherical assemblies.Most significantly,the helical assemblies could be recovered again after air oxidation,implying the reversible morphology transformation driven by redox stimulus.The redox-modulated reversible self-assembly is driven by the variation of electrostatic attraction between organic cations and inorganic anions as well as the electrostatic repulsion between inorganic ionic clusters,proved by X-ray photoelectron spectroscopy (XPS) and 1H NMR spectra.The results will contribute to better understanding the mechanism of dynamic assemblies and inspire the precise fabrication of advanced smart materials.关键词
多金属氧簇/形貌调控/氧化还原/光致变色/动态自组装Key words
Polyoxometalate/Morphology control/Redox/Photochromism/Dynamic self-assembly分类
化学化工引用本文复制引用
张静,王丽娜,陈晓飞,王玉峰,牛成艳,吴立新,唐智勇..氧化还原对Lindqvist型多金属氧簇复合物自组装的动态调控[J].物理化学学报,2020,36(9):117-123,7.基金项目
The project was supported by the National Key Basic Research Program of China (2016YFA0200700),the National Natural Science Foundation of China (21972081,21890381,21721002,21502107),the Frontier Science Key Project of Chinese Academy of Sciences (QYZDJ-SSW-SLH038),and the K.C.Wong Education Foundation.国家重点基础研究计划(2016YFA0200700),国家自然科学基金(21972081,21890381,21721002,21502107),中国科学院前沿科学重点项目(QYZDJ-SSW-SLH038)和王宽诚教育基金资助项目 （2016YFA0200700）
