Cocrystallization of Binary Silver Clusters Into Supramolecular Assembly to Regulate Aggregation-Induced Emission and Thermally Activated Delayed Fluorescence

Abstract

Aggregation-induced emission (AIE) and thermally activated delayed fluorescence (TADF) are two optoelectronic properties with great potential for applications. However, metal nanoclusters exhibiting both AIE and TADF characteristics have not been extensively studied. This study investigates a binary cocrystal system based on silver nanoclusters—Ag₆(Et₂NCS₂)₆·[Ag₁₁(AdmS)₃(Et₂NCS₂)₆]₂ (1-Ag₆·(Ag₁₁)₂), aiming to explore the synergistic effects between flexible-alkyl dithiol and rigid monothiol ligands. Due to the introduction of Ag₆ structures, the system exhibits enhanced stability and modulated optical properties. The binary tricluster 1-Ag₆·(Ag₁₁)₂ demonstrates significant AIE behavior, with an approximately 15-fold increase in intensity when the water volume fraction (f_w) is 60%. Single-crystal X-ray diffraction analysis indicates that the enhanced AIE effect originates from intercluster hydrogen bonding interactions, which drive the self-assembly of sub-clusters and form hierarchical structures, thereby suppressing ligand rotation. In addition, the system exhibits the TADF phenomenon in the temperature range of 100−175 K. In order to further investigate the effect of ligand variations on optical properties, two unitary clusters, Ag₁₁(AdmS)₃(Et₂NCS₂)₆ (2-Ag₁₁-AS) and Ag₁₁(^tBuS)₃(Et₂NCS₂)₆ (3-Ag₁₁-BS), are synthesized, and their roles in regulating optoelectronic properties are explored through ligand exchange reactions. This study provides important insights for the development of efficient luminescent materials with AIE and TADF properties, highlighting the critical roles of ligand exchange and structural configuration.

Keywords

aggregation-induced emission / cocrystallization / silver clusters / supramolecular assembly / thermally activated delayed fluorescence

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