Auxiliary ligand-directed and counter anion-templated effects on coordination networks based on semirigid 2-aminodiacetic terephthalic acid ligand

Reactions of the semirigid polycarboxylate ligand, 2-aminodiacetic terephthalic acid (H(4)adtp), with Zn(II) and Cd(II) salts resulted in {[Zn-2(adtp)(H2O)(2)]center dot 2H(2)O}(n) (1) and [Cd-2(adtp)(mu(2)-H2O)(H2O)(3)](n) (3), respectively. By introducing auxiliary ligand 4,4'-bipyridine (bpy), two 3D regularly arranged pillared-layered frameworks {[Zn-3(adtp)(bpy)(1.5)(mu(3)-OH)(H2O)]center dot NO3 center dot 3H(2)O}(n) (2a) and {[Cd-4(adtp)(2)(bpy)(H2O)(4)]center dot 2.5H(2)O}(n) (4) were obtained. Complex 1 is characterized as a two-dimensional (2D) layer structure, whereas complex 3 features a three-dimensional (3D) framework with two types of alternately arrayed channels. In complex 2a, the one-dimensional (1D) zinc chains built up of alternately interlinked tetranuclear and dinuclear units are cross-linked into 2D layers, which are further pillared by bpy into a 3D cationic framework with NO3- as counterions. As for 4, a 3D pillared-layer framework is observed and comprises carboxylic mu(2)-O bridged - M-O-M-chains. The auxiliary ligand bpy exerts a structure-directing effect on the resultant 3D pillared-layer architectures in 2a and 4, wherein mu(3)-OH bridged tetranuclear metal units or carboxylic mu(2)-O bridged -M-O-M-chains appear. Additionally, the cationic framework in 2a is strongly dependent on counter anions and the concentration of bpy ligand. The isomorphic {[Zn-3(adtp)(bpy)(1.5)(mu(3)-OH)(H2O)]center dot clO(4)center dot 3H(2)O}(n) (2b) with ClO4- as template and counterions is also obtained. The luminescent properties of 1, 2a, 3 and 4 are investigated in detail. Compared with free H(4)adtp, complex 3 exhibits a larger blue-shifted emission band. Complex 2a displays tunable photoluminescence by variation of excitation light and temperature due to multi-centers emissions.