Stepwise assembly of rhombic Cu2 building blocks enables the construction of dimension-tunable luminescent copper nanoclusters.

Elucidating the atomic-level growth mechanisms and structure-property correlations of copper nanoclusters remains challenging. Here, we demonstrate that the stepwise assembly of rhombic Cu2S2 building blocks enables the construction of dimensionally tunable, luminescent copper nanoclusters. Three atomically precise copper nanoclusters, Cu2(p-MBT)2(dppBz)2, Cu4(p-MBT)4(PPh3)4, and Cu8(p-MBT)8(PPh3)4 (abbreviated as Cu2, Cu4, and Cu8, respectively; p-MBT = p-methylbenzenethiol; dppbz = bis(diphenylphosphino)benzene) were controllably synthesized, which are structurally characterized as the monomer, dimer, and tetramer of Cu2S2 subunits, respectively. Specifically, a single Cu2S2 block forms the Cu2 cluster; two blocks undergo planar fusion to produce a Cu4S4 skeleton for the Cu4 cluster; and four blocks vertically stack to yield a double-layer Cu8S8 framework for the Cu8 cluster. The bidentate ligand dppBz restricts the cluster growth by stabilizing the Cu2S2 seed, whereas monodentate PPh3 in conjunction with solvent effects modulates the stacking dimensionality. Crystalline-state photophysical analyses reveal their distinct phosphorescence emissions at 540 nm (Cu2, yellow-green), 480 nm (Cu4, blue-green), and 510 nm (Cu8, green). This dimensionality-dependent Cu2S2 assembly pattern elucidates the growth mechanism of copper nanoclusters and provides an atomic-level platform for rational luminescence engineering.