Self‐Assembly and Anion‐Exchange Properties of a Discrete Cage and 3D Coordination Networks Based on Cage Structures

By using tridentate ligand 4‐(3‐pyridinyl)‐1,2,4‐triazole (pytrz), cage‐like complexes of {[Cu(μ 2 ‐pytrz) 2 ](ClO 4 )(SO 4 ) 0.5 ⋅ C 2 H 5 OH ⋅ 0.25 H 2 O} 6 ( 1 ), {[Cu 3 (μ 3 ‐pytrz) 4 (μ 2 ‐Cl) 2 (H 2 O) 2 ](ClO 4 ) 2 Cl 2 ⋅ 2 H 2 O} n ( 2 ), and {[Cu 3 (μ 3 ‐pytrz) 3 (μ 3 ‐O)(H 2 O) 3 ](ClO 4 ) 2.5 (BF 4 ) 1.5 ⋅ 5.25 H 2 O} n ( 3 ) have been synthesized with different copper(II) salts. Complex 1 represents the second example of a M 6 L 12 metal–organic octahedron with an overall T h symmetry. Complex 2 is constructed from a 3 8 cage‐building unit (CBU) and each CBU connects six neighboring cages to give the first 3D metal–organic framework (MOF) based on octahedral M 6 L 12 . Complex 3 is built from Cu 24 (pytrz) 12 CBUs with the trinuclear copper clusters serving as second building units (SBUs) and decorating each corner of the M 24 L 12 polyhedron. The Cu 24 (pytrz) 12 building unit is linked by extra ligands to give an extended 3D framework that has the formula Cu 24 (pytrz) 24 and possesses a CaB 6 topology. The mixed anions ClO 4 − and BF 4 − in 3 are both included in the inner cavity of the cage and can be completely exchanged by ClO 4 − through the open windows of the cage, as evidenced by the crystal structure of the 3D MOF {[Cu 3 (μ 3 ‐pytrz) 3 (μ 3 ‐O)(H 2 O) 3 ](ClO 4 ) 4 ⋅ 4.5 H 2 O} n ( 4 ). Complex 4 can also be synthesized when employing 1 as a precursor in an extensive study of the anion‐exchange reaction. This represents the first successful conversion of a discrete cage into a 3D coordination network based on a cage structure. Complex 2 remains invariable during anion‐exchange reactions because uncoordinated Cl − ions are located in the comparatively small inner cavity.