Supramolecular Engineering of Cluster-Assembled Materials for Amplification and Dynamic Modulation of Chiral Luminescence

Abstract

Chiral metal clusters have garnered significant research interest in recent years due to their unique photophysical and chiroptical properties. Increased attention is directed toward bimetallic systems, as the synergistic effect of two different metal centers often yields enhanced properties. Despite this progress, obtaining optically active bimetallic clusters with pronounced chirality, both in their ground and excited states, has remained a challenge. Herein, an efficient strategy is formulated for the controlled aggregation of gold(I)-silver(I) coordination clusters leading to enhanced and tunable optical activity. Interactions with chiral and achiral additives resulted in cluster-assembled materials (CAMs) exhibiting morphology-dependent chiroptical responses. The assembly process, in addition to facilitating aggregation-induced enhanced emission (AIEE), generated inverted and amplified chiroptical responses. Interestingly, the resultant Au(I)Ag(I) composite materials exhibited prolonged excited state lifetimes, indicating the possibility of near room temperature thermally activated delayed fluorescence (TADF) and lower temperature phosphorescence. Circularly polarized luminescence with a dissymmetry factor as high as (±)0.05 could be achieved, the highest reported for any metal cluster to date. The enhanced anisotropy highlights the effectiveness of this strategy in modulating excited-state chirality through hierarchical assembly, opening potential for the nanocomposites as chiral light-emitting materials.

Keywords: Chiral nanoassemblies; Circular dichroism; Circularly polarized luminescence; Cluster‐assembled materials; Nanoscale chirality.