Reductant-selected formation of copper nanoclusters with crystallization-induced emission enhancement performance

The rational design of emissive copper nanoclusters presents a significant challenge due to their inherent instability and complex coordination chemistry. In this study, we propose a reductant-mediated strategy to precisely regulate the atomic structure and photophysical properties of copper nanoclusters. The strong reductant sodium borohydride (NaBH₄) yields a non-emissive Cu₁₄(DMP)₆(PPh₂py)₈ species, while the mild reductant borane tert-butylamine complex leads to the formation of a tetrahedral Cu₄(PPh₂py)₄Cl₂ cluster, which exhibits a remarkable crystallization-induced emission enhancement (CIEE). Hirshfeld surface analysis of the Cu₄ nanocluster indicates that multiple non-covalent interactions-such as H⋯H, C-H⋯π, and Cl⋯H contacts-stabilize the molecular packing, effectively suppressing non-radiative decay pathways and contributing to the CIEE phenomenon. This work highlights the crucial role of reductants in modulating copper nanocluster structures and offers novel insights into the design of efficient copper-based emitters.