LnIII/CuI Bimetallic Nanoclusters with Enhanced NIR-II Luminescence

Coinage-metal clusters with excellent luminescence properties have attracted considerable interest due to their intriguing structures and potential applications. However, achieving strong near-infrared (NIR) luminescence in these clusters is highly challenging. Here, we have successfully synthesized the first Ln(III)/Cu-I bimetallic clusters, formulated as [LnCu(54)O(6)Cl(3)(2-MeO-PhC C)(36)] (ClO4)(6) (Ln = Yb for YbCu54, Er for ErCu54, and Gd for GdCu54). Single crystal X-ray diffraction showed that the LnCu(54) clusters have a three-layered core-shell structure, consisting of (LnO(6))@Cu18Cl3@Cu-36 units protected by 36 2-MeO-PhC C- ligands. Notably, the YbCu54 cluster exhibits significant NIR-II luminescence at 986 nm with the solid quantum efficiency of 33.3%, the highest among Cu clusters with NIR-II emission. This work not only reports the first category of Ln(III)/Cu-I clusters but also presents a method to enhance NIR luminescence in coinage-metal clusters through the incorporation of Ln(III) ions.