Assembly of a Cubic Nanocage Co₈L₁₂ and a Hydrogen-Bonded 3D NbO Net Based on the [(HCO₃)₂]²⁻ Synthon and Water

Two new complexes [Co(H2O)6⊂Co8(L1)12]X6·nH2O (X = NO3−, n = 12 (1); X = HCO3−, n = 24, (2); HL1 = 4,6-bis(2-pyridyl)-1,3,5-triazin-2-ol) have been synthesized and characterized by single-crystal X-ray diffraction. A [Co(H2O)6]2+ ion is encapsuled in the central cavity of the cubelike nanocage [Co(H2O)6⊂Co8(L1)12]6+ cation, assembled by eight cobalt ions at the corners and twelve bis-bidentate ligands L1 as the edges, via the formation of 12-fold strong hydrogen bonds between the six coordinated water molecules and the oxygen atoms of twelve L1 as a guest. Complex 1 crystallizes in a centrosymmetric space group P1̅, while 2 is in a very high symmetric space group Im3̅. In 2, a planar [(HCO3)2]2− dimer motif R22(8) synthon plus six lattice water molecules constitute a planar supramolecular synthon R88(20), which acts as a four connector, generating a 3D hydrogen-bonded NbO net with cubelike host cavities of ∼20 Å diameter. Interestingly, the cubelike nanocage [Co(H2O)6⊂Co8(L1)12]6+ cations fill in the cavities as templates. The magnetic properties of 1 have also been studied in the temperature range of 2−300 K, and its magnetic susceptibility obeys the Curie−Weiss law, showing antiferromagnetic coupling.