Coordination polymer gels with modular nanomorphologies, tunable emissions, and stimuli-responsive behavior based on an amphiphilic tripodal gelator

Abstract

The recent upsurge in research on coordination polymer gels (CPGs) stems from their synthetic modularity, nanoscale processability, and versatile functionalities. Here we report self-assembly of an amphiphilic, tripodal low-molecular weight gelator (L) that consists of 4,4′,4-[1,3,5-phenyl-tri(methoxy)]-tris-benzene core and 2,2′:6′,2″-terpyridyl termini, with different metal ions toward the formation of CPGs that show controllable nanomorphologies, tunable emission, and stimuli–responsive behaviors. L can also act as a selective chemosensor for Zn^II with very low limit of detection (0.18 ppm) in aqueous medium. Coordination-driven self-assembly of L with Zn^II in H₂O/MeOH solvent mixture results in a coordination polymer hydrogel (ZnL) that exhibits sheet like morphology and charge-transfer emission. On the other hand, coordination of L with Tb^III and Eu^III in CHCl₃/tetrahydrofuran solvent mixture results in green- and red-emissive CPGs, respectively, with nanotubular morphology. Moreover, precise stoichiometric control of L/Eu^III/Tb^III ratio leads to the formation of bimetallic CPGs that show emissions over a broad spectral range, including white-light-emission. We also explore the multistimuli responsive properties of the white-light-emitting CPG by exploiting the dynamics of Ln^III-tpy coordination.