Solvent Induced Transformation of Homoleptic Alkynyl-Protected Large Silver Nanoclusters

Structural transformation of high-nuclearity nanoclusters is of significant interest because of its relevance to the formation mechanisms and stability of metal clusters. Herein, we report three large homoleptic alkynyl-protected silver nanoclusters, [Ag₉₈(2-CH₃C₆H₄C≡C)₅₂](BF₄)₂, [Ag₈₆(2-CH₃C₆H₄C≡C)₅₀](BF₄)₄, and [Ag₇₄(2-CH₃C₆H₄C≡C)₄₄](BF₄)₂, synthesized from the same precursor 2-CH₃C₆H₄C≡CAg via fine-tuning the reduction rate. X-ray crystallography demonstrates that Ino decahedral Ag₁₃ units serve as building blocks in all three nanoclusters. Remarkably, Ag₉₈ undergoes an intercluster transformation in methanol. It initially converts into Ag₇₄, then Ag₇₄ reacts with Ag₉₈ to form Ag₈₆, which eventually is transformed into the thermodynamically stable Ag₇₄. Time-dependent electrospray ionization mass spectrometry (ESI-MS) confirms such a multi-step reaction process during the transformation, identifying Ag₈₆ as the key intermediate. Our findings not only provide new insights into the structural transformation pathways of nanoclusters but also enhance the understanding of transformation mechanisms, contributing to the rational synthesis of high-nuclearity nanoclusters.