Understanding the Structure of Reversible Coordination Polymers Based on Europium in Electrostatic Assemblies Using Time-Resolved Luminescence

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• 作者：Limin Xu ; Mengqi Xie ; Jianbin Huang ; Yun Yan
• 刊名：Langmuir
• 出版年：2016
• 出版时间：June 14, 2016
• 年：2016
• 卷：32
• 期：23
• 页码：5830-5837
• 全文大小：462K
• 年卷期：0
• ISSN：1520-5827

文摘

In situ characterization of the structure of reversible coordination polymers remains a challenge because of their dynamic and concentration-responsive nature. It is especially difficult to determine these structures in their self-assemblies where their degree of polymerization responds to the local concentration. In this paper, we report on the structure of reversible lanthanide coordination polymers in electrostatic assemblies using time-resolved luminescence (TRL) measurement. The reversible coordinating system is composed of the bifunctional ligand 1,11-bis(2,6-dicarboxypyridin-4-yloxy)-3,6,9-trioxaundecane (L₂EO₄) and europium ion Eu³⁺. Upon mixing with the positively charged diblock copolymer poly(2-vinylpyridine)-b-poly(ethylene oxide) (P2VP₄₁-b-PEO₂₀₅), electrostatic polyion micelles are formed and the negatively charged L₂EO₄–Eu coordination complex simultaneously transforms into coordination “polymers” in the micellar core. By virtue of the water-sensitive luminescence of Eu³⁺, we are able to obtain the structural information of the L₂EO₄–Eu coordination polymers before and after the formation of polyion micelles. Upon analyzing the fluorescence decay curves of Eu³⁺ before and after micellization, the fraction of Eu³⁺ fully coordinated with L₂EO₄ is found to increase from 32 to 83%, which verifies the occurrence of chain extension of the L₂EO₄–Eu coordination polymers in the micellar core. Our work provides a qualitative picture for the structure change of reversible coordination polymers, which allows us to look into these “invisible” structures.