Formation of nanocluster {Dy} containing Dy-exclusive vertex-sharing [Dy(μ-OH)] cubanes via simultaneous multitemplate guided and step-by-step assembly.

The formation of high-nuclearity clusters of lanthanide usually involves many complicated self-assembly processes. Thus, tracking the formation process is extremely difficult and research on the assembly mechanism is very rare. In this study, a Dy-exclusive nanocluster containing vertex-sharing [Dy(μ-OH)] cubanes, denoted as [Dy(L)(OH)(CHO)(HO)]·(CHO) (Dy, L = quinoline-2-carboxylate), was designed and synthesized from L and DyCl·6HO. Eight quinoline-2-carboxylate ligands were encapsulated on the periphery of the Dy cluster, which served to stabilize the core. The high stability of the Dy cluster core was further confirmed by high-resolution electrospray-ionization mass spectrometry (HRESI-MS). With increased ion-source energy, only CHO and OH bridging ligands were replaced inside the Dy cluster. Notably, eight intermediate fragments were successfully observed from the Dy cluster formation by time-dependent HRESI-MS. First, ligand L captured Dy to give Dy, which further formed Dy through μ-O bridging. The Dy cluster was constructed in one step with four Dy and four Dy as templates: L → Dy→ Dy→ Dy. Moreover, a series of Dy-Dy fragment peaks with relatively weak intensities were observed, and an alternative stepwise-assembly route was proposed: L → Dy→ Dy→ Dy→ Dy→ Dy→ Dy→ Dy. On comparing the two different assembly methods, the multitemplate guided assembly formed Dy was found to be dominant. To the best of our knowledge, this study was the first to propose the involvement of two self-assembly mechanisms in the construction of lanthanide clusters, as further confirmed by HRESI-MS. Magnetic studies further showed that Dy clusters exhibited field-induced single-molecule magnet behavior.