[Cu-15(PPh3)(6)(PET)(13)](2+): a Copper Nanocluster with Crystallization Enhanced Photoluminescence

Due to their atomically precise structure, photoluminescent copper nanoclusters (Cu NCs) have emerged as promising materials in both fundamental studies and technological applications, such as bio-imaging, cell labeling, phototherapy, and photo-activated catalysis. In this work, a facile strategy is reported for the synthesis of a novel Cu NCs coprotected by thiolate and phosphine ligands, formulated as [Cu-15(PPh3)(6)(PET)(13)](2+), which exhibits bright emission in the near-infrared (NIR) region (approximate to 720 nm) and crystallization-induced emission enhancement (CIEE) phenomenon. Single crystal X-ray crystallography shows that the NC possesses an extraordinary distorted trigonal antiprismatic Cu-6 core and a, unique among metal clusters, tri-blade fan-like structure. An in-depth structural investigation of the ligand shell combined with density functional theory calculations reveal that the extended C-H center dot center dot center dot pi and pi-pi intermolecular ligand interactions significantly restrict the intramolecular rotations and vibrations and, thus, are a major reason for the CIEE phenomena. This study provides a strategy for the controllable synthesis of structurally defined Cu NCs with NIR luminescence, which enables essential insights into the origins of their optical properties.

Automated summary

This study presents a novel synthesis method for Cu NCs with bright emission in the near-infrared region and crystallization-induced emission enhancement phenomena, providing essential insights into the origins of their optical properties.