Synthesis, structural versatility and magnetic properties of a series of copper(II) coordination polymers based on bipyrazole and various dicarboxylate ligands

Seven new copper(II) coordination networks combining flexible 3,3', 5,5'-tetramethyl-4,4'-bipyrazole (bpz) and diverse dicarboxylates, [Cu(bpz)(0.5)(adip)](n) (1), [Cu-2(bpz)(4)(sub)(2)](n) (2), [Cu-4(bpz)(1.5)(aze)center dot H2O] n (3), [Cu-2(bpz)(pta)(2)(H2O)center dot H2O](n) (4), [Cu-2(bpz)(ipa)](n) (5), [Cu-2(bpz)(o-pda)(2)center dot H2O](n) (6), and [Cu-2(mu(3)-OH)(bpz)(p-pda)(1.5)center dot H2O](n) (7) (H(2)adip = adipic acid, H(2)sub = suberic acid, H(2)aze = azelaic acid, H(2)pta = phthalic acid, H(2)ipa = isophthalic acid, H(2)o-pda = o-henylenediacetic acid, H(2)p-pda = p-phenylenediacetic acid), have been obtained under solvothermal conditions and structurally verified by single-crystal X-ray diffraction analyses and further characterized by elemental analyses, powder X-ray diffraction (PXRD), infrared spectroscopy (IR), UV-vis spectroscopy and thermogravimetric analyses (TGA). Single crystal X-ray diffraction analysis revealed that both 1 and 6 are 6-connected pcu networks (point symbol: {4(12).6(3)}) based on paddle-wheel [Cu-2(COO)(4)] secondary building units (SBU). Complexes 2 and 4 are 2D 44-sql networks based on a single metal ion node and a binuclear [Cu-2(COO)(4)(H2O)] SBU, respectively, while complex 3 features an extremely rare 3D 5-connected hxg-d-5-C2/c (point symbol: {4(2).6(7).8}) network. Complex 5 shows a 1D tape structure built from bpz sealed 1D helical Cu-2(ipa) chains along the b axis, and 7 is a 3D 8-connected hex (point symbol: {3(6).4(18).5(3).6}) network based on a centrosymmetric [Cu-4(mu(3)-OH)(2)(COO)(4)] SBU. A thorough structural comparison of these coordination networks suggests that the coordination fashions, conformations of dicarboxylates along with the different inorganic Cu(II) SBUs simultaneously play a significant role in constructing the diverse networks. Variable-temperature magnetic susceptibility data denote that 4 and 7 display antiferromagnetic interactions in binuclear [Cu-2(COO)(4)(H2O)] and [Cu-4(mu 3-OH)(2)(COO)(4)] SBUs. Moreover, the thermal stability and UV-vis spectra of 1-7 are discussed in detail.