Influence of organic bases on constructing 3D photoluminescent open metal-organic polymeric frameworks

Four three-dimensional non-interpenetrating open coordination frameworks constructed from the CTC ligand (CTC=cis, cis-1,3,5-cyclohexanetricarboxylate) coordinated to metal ions (Mn(II) and Cd(II)): Mn-3(CTC)(2)(DMF)(2) (1); Cd-3(CTC)(2)(H2O)(3).H2O (2); Cd-3(CTC)(2)(4,4'-bpy)(2)(EG)(2) (3); Cd-3(CTC)(2)(mu(2)-hmt)(DMF) (C2H5OH)(H2O).2H(2)O (4) (DMF=dimethylformamide and EG=ethylene glycol) have been synthesized by slow evaporation of DMF-C2H5OH-H2O solutions of M(II) (Mn(II) or Cd(II)) and CTC in the presence of the organic bases TEA (triethylamine), TEA, 4,4'-bpy (4,4'-bipyridine) and hmt (hexamethylenetetramine), respectively, and structurally characterized by X-ray crystallography. The polymer 1 constructed by CTC and Mn(II) exhibits a 3-D architecture with 5x9 Angstromchannels; the polymer 2 formed by CTC and Cd(II) exists a 3-D extended framework with 9x9 Angstromchannels; wavelike sheet subunits of the polymer 3 are upheld by 4,4'-bpy ligands resulting in a 3-D framework with 4x10 Angstromchannels; two-fold alternate sheet subunits of the polymer 4 are interlinked by mu(2)-hmt ligands to form a novel 3-D architecture with 7x8 Angstromchannels. Polymers 2-4 exhibit their strongest excitation peaks at 391, 390 and 394 nm, respectively, and their main strong emission peaks are at 543, 460 (with a shoulder peak at about 570 nm) and 557 nm, respectively.