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(mu(2)-pytrz)(2)]- (ClO4)(SO4)0.5 center dot C2H5OH-0.25H(2)O} (1), {[Cu-3(mu(3)-pytrz)(4)(mu(2)-Cl)(2)(H2O)(2)]-(ClO4)(2)Cl-2 center dot 2H(2)O}(n) (2), and {[Cu-3(mu(3-)pytrz)(3)(mu(3)-O)(H2O)(3)](ClO4)(2.5)- (BF4)(1.5)center dot 5.25H(2)O}(n) (3) have been synthesized with different copper(II) salts. Complex I represents the second example of a M6L12 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 M6L12. 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 M24L12 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)(2), and possesses a CaB6 topology. The mixed anions ClO4- and BF4- in 3 are both included in the inner cavity of the cage and can be completely exchanged by ClO4- through the open windows of the cage, as evidenced by the crystal structure of the 3D MOF {[Cu-3(mu(3)-pytrz)(3)(mu(3)-O)- (H2O)(3)](ClO4)(4)center dot 4.5H(2)O}(n) (4). Complex 4 can also be synthesized when employing I 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.