Isostructural Nanocluster Manipulation Reveals Pivotal Role of One Surface Atom in Click Chemistry

Elucidating single-atom effects on the fundamental properties of nanoparticles is challenging because single-atom modifications are typically accompanied by appreciable changes to the overall particle's structure. Herein, we report the synthesis of a [Cu₅₈H₂₀PET₃₆(PPh₃)₄]²⁺ (Cu₅₈; PET: phenylethanethiolate; PPh₃: triphenylphosphine) nanocluster—an atomically precise nanoparticle—that can be transformed into the surface-defective analog [Cu₅₇H₂₀PET₃₆(PPh₃)₄]⁺ (Cu₅₇). Both nanoclusters are virtually identical, with five concentric metal shells, save for one missing surface copper atom in Cu₅₇. Remarkably, the loss of this single surface atom drastically alters the reactivity of the nanocluster. In contrast to Cu₅₈, Cu₅₇ shows promising activity for click chemistry, particularly photoinduced [3+2] azide-alkyne cycloaddition (AAC), which is attributed to the active catalytic site in Cu₅₇ after the removal of one surface copper atom. Our study not only presents a unique system for uncovering the effect of a single-surface atom modification on nanoparticle properties but also showcases single-atom surface modification as a powerful means for designing nanoparticle catalysts.