Structure and assembly mechanism of a centipede-shaped high-nuclear Dy14Cu12 heterometallic nanocluster

Abstract

The assembly studies of high-nuclear clusters have received much interest in recent years due to their targeted synthesis for some special usages. A Schiff base ligand 2-[N-(2-hydroxynaphthylidene)amino]-2-(hydroxymethyl)propane-1,3-diol (H₄L) was thus prepared in this work and was allowed to react with [Cu₂(OAc)₄(H₂O)₂] and Dy(NO)₃·6H₂O, giving a high-nuclear 3d–4f heterometallic Cu₁₂Dy₁₄ nanocluster (1) with the formula [(C₂H₅)₃NH]₄[Cu₁₂Dy₁₄O(OH)₁₆(H₂L)₈(HL)₄(HL′)₄(OAc)₁₀](NO₃)₄(OAc)₂·6CH₃CN·5EtOH·1.5H₂O (H₃L′ = 1,1,1-tris-(hydroxymethyl)methanamine). It features a centipede-shaped structure constructed from eight Dy₃Cu cubanes sharing the Dy(III) vertices. Its assembly mechanism was explored through time-dependent high-resolution electrospray ionization mass spectrometry (HRESI-MS). This revealed that the hierarchical assembly of 1 undergoes two possible routes: H₄L → DyCuL → Dy₂CuL → Dy₃Cu₂L₂ → Dy₄Cu₂L₂ → Dy₄Cu₃L₃ → Dy₅Cu₄L₄→ Dy₁₄Cu₁₂L₁₂L′₄ and H₄L → DyCuL → DyCu₂L → Dy₂Cu₂L₂ → Dy₂Cu₃L₄ → Dy₃Cu₄L₄ → Dy₅Cu₄L₄ → Dy₁₄Cu₁₂L₁₂L′₄. These results not only provide solid evidence for understanding the assembly mechanism of high-nuclear 3d–4f clusters, but also help to give some hints for designing and preparing new high-nuclear clusters.