Atomically Precise Cu₁₂ Nanoclusters with Thermally Activated Delayed Fluorescence Properties

Ligand-stabilized metal nanoclusters with atomic precision are considered to be promising materials in the field of light-emitting and harvesting. Among these, nanoclusters with thermally activated delayed fluorescence (TADF) properties are highly sought after. While several gold and silver nanoclusters with TADF properties have been reported in recent years, research on copper counterparts has significantly lagged behind. In this study, we present the synthesis, total structure determination, and photoluminescent properties of a copper cluster with TADF properties. The cluster, with the molecular formula (PPh₄)[Cu₁₂(NO₃)₆(AdmS)₆] (PPh₄ is tetraphenylphosphine tetraphenylboron, and AdmSH is adamantanethiol), was obtained in a single reaction in the presence of air and fully characterized using electrospray ionization mass spectroscopy (ESI-MS), X-ray photoelectron spectroscopy, nuclear magnetic resonance, and ultraviolet-visible spectroscopy (UV-vis). The molecular structure of the cluster, as determined by X-ray crystallographic analysis, reveals the stabilization of a Cu₁₂ core (layer-by-layer growth mode of Cu₃@Cu₆@Cu₃) with 6 NO₃^- and 6 AdmS^- ligands acting as stabilizing ligands. Interestingly, the cluster exhibits photoluminescence in both crystalline and solution states and displays typical TADF characteristics within the temperature range of 163-243 K. This study not only presents a pioneering example of copper nanoclusters with TADF properties but also highlights the promising future of copper clusters in material science.