Generalized Synthesis of Calixarene-Based High-Nuclearity M4n Nanocages (M = Ni or Co; n = 2–6)

A family of high-nuclearity M4n (M = Ni or Co, n = 2–6) coordination nanocages constructed by M4–calix­[4]­arene molecular building blocks (MBBs) with inorganic phosphate or organic phosphonate ligands have been isolated by solvothermal syntheses and characterized by single-crystal X-ray diffraction. This family can be divided into five structural types with an increase in the number of M4–calix­[4]­arene MBBs, including Ni8 (1 and 2, n = 2), M12 (M = Ni (3) and Co (4), n = 3), M16 (M = Ni (5) and Co (6), n = 4), Co20 (7, n = 5), and Co24 (8, n = 6) coordination nanocages. Structural analyses reveal that the metallic cores of 1 and 2 are arranged in chair conformation, while compounds 36 with closed-shell structures, where their ports are sealed by sodium ions, present the first examples of 2p-3d heterometallic metal–calixarene nanocages to our knowledge. The novel helmet-like Co20 (7) is the only one in this family with an open-shell structure, which can be thought of as a truncated octahedral Co24 (8) nanocage cutting one face. Furthermore, the magnetic behaviors of 18 have been investigated, suggesting the existence of strong antiferromagnetic interactions between magnetic centers for all title coordination cages.