Atomically Precise Bimetallic Au₁₉Cu₃₀ Nanocluster with an Icosidodecahedral Cu₃₀ Shell and an Alkynyl-Cu Interface

Bimetallic nanoclusters Au₁₉Cu₃₀ with chemical composition of [Au₁₉Cu₃₀(C≡CR)₂₂(Ph₃P)₆Cl₂](NO₃)₃ (where RC≡C is from 3-ethynylthiophene (H₃C₄S-3-C≡CH) or ethynylbenzene (PhC≡CH)) has been synthesized. Single X-ray structural analysis reveals that Au₁₉Cu₃₀ has a multishelled core structure of Au@Au₁₂@Cu₃₀@Au₆, comprising a centered icosahedral Au₁₃ (Au@Au₁₂) surrounded by an icosidodecahedral Cu₃₀ shell and an outmost shell of a chairlike hexagonal Au₆. The alkynyl carbon is bound to the hollow sites on the Au₁₉Cu₃₀ nanocluster surface, which is a novel interfacial binding mode in alkynyl-protected alloy nanoclusters. The Cu₃₀ icosidodecahedron is unprecedented and Au₁₉Cu₃₀ represents the first alkynyl-protected Au-Cu alloy nanocluster.