Eu3+‐Directed Supramolecular Metallogels with Reversible Quadruple‐Stimuli Response Behaviors

Abstract

AbstractSmart luminescent materials that have the ability to reversibly adapt to external environmental stimuli and possess a wide range of responses are continually emerging, which place higher demands on the means of regulation and response sites. Here, europium ions (Eu3+)‐directed supramolecular metallogels are constructed by orthogonal self‐assembly of Eu3+ based coordination interactions and hydrogen bonding. A new organic ligand (L) is synthesized, consisting of crown ethers and two flexible amide bonds‐linked 1,10‐phenanthroline moieties to coordinate with Eu3+. Synergistic intermolecular hydrogen bonding in L and Eu3+‐L coordination bonding enable Eu3+ and L to self‐assemble into shape‐persistent 3D coordination metallogels in MeOH solution. The key to success is the utilization of crown ethers, playing dual roles of acting both as building blocks to build L with C2‐symmetrical structure, and as the ideal monomer for increasing the energy transfer from L to Eu3+’s excited state, thus maintaining the excellent luminescence of metallogels. Interestingly, such assemblies show K+, pH, F−, and mechano‐induced reversible gel‐sol transitions and tunable luminescence properties. Above findings are useful in the studies of molecular switches, dynamic assemblies, and smart luminescent materials.