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

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.