Architecture of Hydrogen-Bonded Three-Dimensional NbO Net Based on Hydrogen Carbonate or Trimesic Acid Using a Hydrophobic, Predesigned, Cubic Cation [Co(H<sub>2</sub>O)<sub>6</sub>⊂Co<sub>8</sub>L<sub>12</sub>] as a Template

2009-01-07T00:00:00Z (GMT) by Man-Li Cao Hao-Jun Mo Bao-Hui Ye
A nanocage complex [Co(H<sub>2</sub>O)<sub>6</sub>⊂Co<sub>8</sub>L<sub>12</sub>](NO<sub>3</sub>)<sub>6</sub>·12H<sub>2</sub>O (<b>1</b>) (HL = 2-amino-4,6-bis(2-pyridyl)-1,3,5-triazin) has been synthesized under solvothermal conditions and characterized by single-crystal X-ray diffraction. A [Co(H<sub>2</sub>O)<sub>6</sub>]<sup>2+</sup> ion as a guest is included in the central cavity of the cubelike nanocage [Co(H<sub>2</sub>O)<sub>6</sub>⊂Co<sub>8</sub>L<sub>12</sub>]<sup>6+</sup> cation, assembled by 8 cobalt ions at the corners and 12 bis-bidentate ligands L at the edges, via the formation of 12-fold strong hydrogen bonds between the six coordinated water molecules and the nitrogen atoms of 12 L ligands. When compound <b>1</b> cocrystalizes with KHCO<sub>3</sub> and trimesic acid (H<sub>3</sub>TMA), complexes [Co(H<sub>2</sub>O)<sub>6</sub>⊂Co<sub>8</sub>L<sub>12</sub>](HCO<sub>3</sub>)<sub>6</sub>·24H<sub>2</sub>O (<b>2</b>) and [Co(H<sub>2</sub>O)<sub>6</sub>⊂Co<sub>8</sub>L<sub>12</sub>](H<sub>2</sub>TMA)<sub>6</sub>·6EtOH·3H<sub>2</sub>O (<b>3</b>) are obtained, respectively. In <b>2</b>, a planar [(HCO<sub>3</sub>)<sub>2</sub>]<sup>2−</sup> dimer motif <i>R</i><sub>2</sub><sup>2</sup>(8) synthon plus six lattice water molecules constitute a planar supramolecular synthon <i>R</i><sub>8</sub><sup>8</sup>(20), which acts as a 4-connector, generating a three-dimensional (3D) hydrogen-bonded NbO net with an approximately 20 Å diameter cavity. In <b>3</b>, the <i>R</i><sub>4</sub><sup>4</sup>(24) synthon, regarded as a 4-connector, connects each other via the phenyl ring of H<sub>3</sub>TMA as a spacer into a NbO net with a cavity of ∼20 Å diameter. The hydrophobic, cubic, nanosize cations [Co(H<sub>2</sub>O)<sub>6</sub>⊂Co<sub>8</sub>L<sub>12</sub>]<sup>6+</sup> embed in the cavities of NbO nets as templates and play an indispensable role in the formation of 3D hydrogen-bonded networks. The work presented here seems to suggest that the nanosize complex as a template plays a crucial role in the formation and stabilization of supramolecular architecture and crystal engineering.