Evolution of Transient Luminescent Assemblies Regulated by Trace Water in Organic Solvents.

Abstract

Trace water in organic solvents can play a crucial role in the construction of supramolecular assemblies, which has not gained enough attention until very recent years. Herein, we demonstrate that residual water in organic solvents plays a decisive role in the regulation of the evolution of assembled structures and their functionality. By adding Mg(ClO4)2 into a multi-component organic solution containing terpyridine-based ligand 3Tpy and monodentate imidazole-based ligand M2, the system underwent an unexpected kinetic evolution. Metallo-supramolecular polymers (MSP) formed first by the coordination of 3Tpy and Mg2+, but they subsequently decomposed due to the interference of M2, resulting in a transient MSP system. Further investigation revealed that this occurred because residual water in the solvent and M2 cooperatively coordinated with Mg2+. This allowed M2 to capture Mg2+ from MSP, which led to depolymerization. However, owing to the slow reaction between trace water/M2/Mg2+, the formation of MSP still occurred first. Therefore, water regulated both the thermodynamics and kinetics of the system and was the key factor for constructing the transient MSP. Fine-tuning the water content and other assembly motifs regulated the assembly evolution pathway, tuned the MSP lifetime, and made the luminescent color of the system undergo intriguing transition processes over time.