Spacer length effect on the formation of different zinc coordination polymers of 1,4-benzenedicarboxylate and flexible bipyrazolyl ligands

The solvothermal reactions of Zn(NO3)2∙6H2O with 1,4-benzenedicarboxylic acid (1,4-H2bdc) and 1,4-bis(3,5-dimethyl-1H-pyrazol-1-yl)butane (dmpzb) or 1,6-bis(3,5-dimethyl-1H-pyrazol-1-yl)hexane (dmpzh) afforded two three-dimensional coordination polymers [Zn3(1,4-bdc)3(dmpzb)]n (1) and [Zn2(1,4-bdc)2(dmpzh)]n (2), respectively. Compounds 1 and 2 were characterized by elemental analysis, IR, powder X-ray diffraction, and single crystal X-ray diffraction. Compound 1 has an 8-connected 3D net (a 364185262 Schläfli symbol) assembled from trinuclear [Zn3(1,4-bdc)3] units and 1,4-bdc and dmpzb bridges. Compound 2 has a 6-connected 3D net (with a 485463 Schläfli symbol) constructed from binuclear [Zn2(1,4-bdc)2] units and 1,4-bdc and dmpzh linkers. The solid state luminescent and thermal stability properties of 1 and 2 at ambient temperature were also investigated. The results showed that the spacer lengths of bipyrazol-based ligands did affect the topological structures of zinc(II) coordination polymers.