All-Calixarene-Protected Silver Nanocluster with All Silver Atoms in a Face-Centered Cubic Arrangement

Tailoring the surface ligands of metal nanoclusters is important for engineering unique configurations of metal nanoclusters. Thiacalix[4]arene has found extensive applications in the construction of metal nanoclusters. In this investigation, we present the synthesis and characterization of the first all-calixarene-protected silver nanoclusters, [Ag(CH₃CN)₄]₂[Ag₄₄(BTCA)₆] (Ag₄₄, H₄BTCA = p-tert-butylthiacalix[4]arene). Single-crystal X-ray structural analysis reveals that all silver atoms are in a face-centered cubic (fcc) arrangement. The formation of such an fcc structure is attributed to the selectively passivation on {100} facets by BTCA^4-. Thiacalixarene substantially facilitates the stability of Ag₄₄ due to its multiple coordination sites and bulkiness. Mass spectrometry and theoretical calculations reveal that Ag₄₄ is a superatomic silver nanocluster with 22 free electrons in the following configuration: 1S²1P⁶1D⁶1F²2S²1D⁴. This work not only elucidates the impact of macrocyclic ligands on the stabilization of silver clusters but also furnishes an approach for assembling atomically precise fcc nanoclusters.