Synthesis, Structures And Properties Of The Metal-Organic Frameworks Constructed By2-(3,4-dimethylphenyl)-imidazole Dicarboxylate

With the development of crystal engineering, the design and self-assembly of metal-organic frameworks (MOFs) have attracted much attention. Based on our previous findings on2-position substituted imidazole dicarboxylates, we carry on the study of coordination features of the newly designed ligand,2-(3,4-dimethylphenyl)-imidazole4,5-dicarboxylic acid (H3DMPpIDC).First, we calculated the natural bond orbital (NBO) charge distributions of H3DMPhIDC, and predicted its coordination ability. Then, we selected H3DMPpIDC as bridging ligand to react with metal ions under hydro(solvo)thermal conditions. By controlling the temperature, pH value, solvent used and the auxiliary ligands, and so on, thirteen polymers with unique structures have been synthesized.Polymer{[Co3(DMPhIDC)2(H2O)6]·2H2O}n (1) is a windmill-shape3D structure bearing [Co2(DMPhIDC)]6cages.[Mn3(H2DMPhIDC)2(HDMPhIDC)2(bpp)]n (bpp1,3-di(4-pyridyl)propane)(2) is also a3D structure showing{103}4{10} topology.{[Mn5(DMPhIDC)2(HDMPhIDC)2(Phen)5]·2CH3OH-3H2O}n (3) is a2D structure.{[Mn3(DMPhIDC)2(H2O)6]-2H2O}n (4) and{[Zn3(DMPhIDC)2(H2O)6]-2H2O}n (5) are isomorphism with1.[Zn(HDMPhIDC)(Phen)]n (6) is a1D helix chain.[Cd(HDMPhIDC)(Py)]n (7) is a3D structure.[Cd(HDMPhIDC)(en)]n (8) is also a helix chain as6.{[Cu3(HDMPhIDC)3(py)3]-H2O}n(9) is a1D chain with the pyridine rings appending in the side chain.[Pb2(DMPhIDC)(OH)]n (10) is a2D structure. Three main-group metal polymers [Sr(HDMPhIDC)(H2O)]n (11),[Ca(HDMPhIDC)(H2O)2]n (12) and [Mg(HDMPhIDC)(H2O)2]n (13) are2D structures. We found that the H3DMPhIDC ligand shows strong coordination ability and various coordination modes, which confirm our predication.The thermal stabilities of2,3,8and9are stronger than those of other polymers. Fluorescence studies show that the fluorescence intensity of Ca(II) polymer is stronger than the Mg and Sr polymers. The purities of the thirteen polymers were verified by XRPD.