A Uniquely Structured Heteronuclear Cluster Cage with Anion-Templated Pentagons and Hexagons

Constructing structurally sophisticated molecules with interesting properties is the goal of supramolecular chemistry. Herein, two heterometallic clusters, formulated respectively as [Gd136Ni84L106(μ6-C2O4)12(μ5-NO3)12(μ3-OH)176(μ-OH)26(μ4-C2O4)3(H2O)106]Cl120·49H2O·90MeOH (Gd136Ni84, H2L = N-methyliminodiacetic acid) and [Tb136Ni84L106(μ6-C2O4)12(μ5-NO3)12(μ3-OH)176(μ-OH)26(H2O)114]Cl126·50H2O·130MeOH (Tb136Ni84), were obtained by the cohydrolysis of Ln3+ (Ln = Gd, Tb) and Ni2+ in the presence of H2L and triethylamine. The essentially isostructural cationic cluster cages are constructed by coexisting pentagons and hexagons whose formation is respectively templated by nitrate and oxalate ions. Rather than the desired buckminsterfullerene structure, the clusters are of a truncated tetrahedral structure due to the unique disposition of the polygonal building units that are structurally distinct from those in a regular fullercage. Cluster Gd136Ni84 maintains its structural integrity in solution as evidenced by the results of mass spectroscopic and electron microscopic studies. Its isothermal magnetic entropy change is 43.91 J·kg-1·K-1 at 3.0 K and 7.0 T, placing it among the high-performing lanthanide-containing clusters possibly useful for magnetic cooling.