A two-dimensional mixed-valence CuII/CuIcoordination polymer constructed from 2-(pyridin-3-yl)-1H-imidazole-4,5-dicarboxylate
Coordination polymers are a thriving class of functional solid-state materials and there have been noticeable efforts and progress toward designing periodic functional structures with desired geometrical attributes and chemical properties for targeted applications. Self-assembly of metal ions and organic ligands is one of the most efficient and widely utilized methods for the construction of CPs under hydro(solvo)thermal conditions. 2-(Pyridin-3-yl)-1H-imidazole-4,5-dicarboxylate (HPIDC2−) has been proven to be an excellent multidentate ligand due to its multiple deprotonation and coordination modes. Crystals of poly[aquabis[μ3-5-carboxy-2-(pyridin-3-yl)-1H-imidazole-4-carboxylato-κ5N1,O5:N3,O4:N2]copper(II)dicopper(I)], [CuIICuI2(C10H5N3O4)2(H2O)]n, (I), were obtained from 2-(pyridin-3-yl)-1H-imidazole-4,5-dicarboxylic acid (H3PIDC) and copper(II) chloride under hydrothermal conditions. The asymmetric unit consists of one independent CuIIion, two CuIions, two HPIDC2−ligands and one coordinated water molecule. The CuIIcentre displays a square-pyramidal geometry (CuN2O3), with twoN,O-chelating HPIDC2−ligands occupying the basal plane in atransgeometry and one O atom from a coordinated water molecule in the axial position. The CuIatoms adopt three-coordinated Y-shaped coordinations. In each [CuN2O] unit, deprotonated HPIDC2−acts as anN,O-chelating ligand, and a symmetry-equivalent HPIDC2−ligand acts as an N-atom donorviathe pyridine group. The HPIDC2−ligands in the polymer serve as T-shaped 3-connectors and adopt a μ3-κ2N,O:κ2N′,O′:κN′′-coordination mode, linking one CuIIand two CuIcations. The Cu cations are arranged in one-dimensional –Cu1–Cu2–Cu3– chains along the [001] direction. Further crosslinking of these chains by HPIDC2−ligands along thebaxis in a –Cu2–HPIDC2−–Cu3–HPIDC2−–Cu1– sequence results in a two-dimensional polymer in the (100) plane. The resulting (2,3)-connected net has a (123)2(12)3topology. Powder X-ray diffraction confirmed the phase purity for (I), and susceptibilty measurements indicated a very weak ferromagnetic behaviour. A thermogravimetric analysis shows the loss of the apical aqua ligand before decomposition of the title compound.