Three 3D coordination polymers constructed by Cd(II) and Zn(II) with imidazole-4,5-dicarboxylate and 4,4′-bipyridyl building blocks

Three 3D coordination polymers of {(H(2)bpy)[Cd-9(HIDC)(4)(IDC)(4)(bpy)(4)]center dot 8H(2)O}(n) (1), [Zn-3(IDC)(2)(bpy)(H2O)(2)](n) (2), and {[Zn-3(IDC)(2)(bpy)(3)]center dot(bpy)center dot 8H(2)O}(n) (3) (H3IDC = imidazole-4,5-dicarboxylic acid, bpy = 4,4'-bipyridyl) were hydrothermally synthesized by controlling the final pH values of the solutions of ca. 6, and characterized by single-crystal X-ray diffraction. In compound 1, unprecedented double-square units of [Cd-4(mu(3)-HIDC)(2)(mu(4)-IDC)(mu(5)-IDC)(2)(4-) are linked by [Cd(bpy)(2)](2+) to generate a ID chain of {[Cd-8(mu(3)-HIDC)(4)(mu(4)-IDC)(2)(mu(5)-IDC)(2)]Cd(bpy)(2)}(n)(2-), and the 1D chains are further bridged by mu 2-bpy to form a 2D brick-wall-like network of [Cd-8(mu(3)-HIDC)(4)(mu(4)-IDC)(2)(mu(5)-IDC)(2)(mu(2)-bpy)(2)}Cd(bpy)(2)}(n)(2n-) (equivalent to[Cd-9(HIDC)(4)(IDC)(4)(bpy)(4)](n)(2n-)). Each brick contains one protonated bpy ion of H(2)bpy(2+) to get a neutral compound of {(H-2)bpy)[Cd-9(HIDC)(4)(IDC)(4)(bpy)(4)]center dot 8H(2)O}(n). The adjacent 2D brick walls are perpendicularly packed and interlinked by mu(4)-IDC3- and mu(5)-IDC3- bridges to generate a 3D open framework of 1. The species of mu(3)-HIDC2-, mu(4)-IDC3-, mu(5)-IDC3-, H(2)bpy(2+), mu(2)-bpy, and monodentate bpy coexist in compound 1. Compound 2 consists of 2D wavelike sheets of [Zn-3(mu(3)-IDC)(2)(H2O)(2)], which are further linked through mu(2)-bpy to generate a 3D structure. In 3, the 2D honeycomb-like sheets of [Zn-3(IDC)(2)](n) are bridged by mu(2)-bpy to result in a 3D open framework with hexagonal and tetragonal channels. Compounds 1 and 2 are stable up to 320 and 400 degrees C, respectively, and display strong blue fluorescent emission at room temperature.