Coordination-Assembly of Lanthanide Supramolecular Hydrogels with Luminescent Multi-stimulus Response

• Published in: Inorganic chemistry 2021-12, Vol.60 (23), p.18192-18198
• Main Authors: Wang, Zi-Cheng, Li, Xiao-Zhen, Liu, Jia-Hui, Zhou, Li-Peng, Guo, Xiao-Qing, Cheng, Xiu-Yan, Sun, Qing-Fu
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.1c02827

Luminescent supramolecular hydrogels have shown extensive potential for a variety of applications due to their unique optical properties and biocompatibility. Coordination self-assembly provides a promising strategy for the preparation of supramolecular hydrogels. In this contribution, a series of luminescent lanthanide (Ln) supramolecular hydrogels HG-Ln2n L3n 1/2 are synthesized by coordination self-assembly of Ln ions and V shaped bis-tetradentate ligands (H4L1 and H4L2) with different bent angles (∠B). Two rigid conjugated ligands H4L1 and H4L2 with bent angles (∠B ≈ 150°) featuring a 2,6-pyridine bitetrazolate chelating moiety were designed and synthesized, which generated hydrogels via the deprotonation self-assembly with lanthanide ions. Characteristic Eu3+ and Yb3+ emissions were realized in the corresponding hydrogels, with intriguing multi-stimulus response behaviors. The luminescence of the HG-Eu2n L3n 1 hydrogel can be enhanced or quenched when stimulated by diverse metal ions, attributed to the replacement of the coordinated lanthanide ions and changes in the intersystem crossing efficiency of the ligand. Furthermore, pH-responsive emission of the HG-Eu2n L3n 1 hydrogel has also been observed. Our work provides potential strategies for the design of next-generation smart responsive hydrogel materials with variable structures.