Self-Healing Heterometallic Supramolecular Polymers Constructed by Hierarchical Assembly of Triply Orthogonal Interactions with Tunable Photophysical Properties.

Abstract

Here, we present a method for the building of new bicyclic heterometallic cross-linked supramolecular polymers by hierarchical unification of three types of orthogonal noncovalent interactions, including platinum(II)-pyridine coordination-driven self-assembly, zinc-terpyridine complex, and host-guest interactions. The platinum-pyridine coordination provides the primary driving force to form discrete rhomboidal metallacycles. The assembly does not interfere with the zinc-terpyridine complexes, which link the discrete metallacycles into linear supramolecular polymers, and the conjugation length is extended upon the formation of the zinc-terpyridine complexes, which red-shifts the absorption and emission spectra. Finally, host-guest interactions via bis-ammonium salt binding to the benzo-21-crown-7 (B21C7) groups on the platinum acceptors afford the cross-linked supramolecular polymers. By continuous increase of the concentration of the supramolecular polymer to a relatively high level, supramolecular polymer gel is obtained, which exhibits self-healing properties and reversible gel-sol transitions stimulated by various external stimuli, including temperature, K+, and cyclen. Moreover, the photophysical properties of the supramolecular polymers could be effectively tuned by varying the substituents of the precursor ligands.