Two Cd(II) and Ni(II) complexes constructed with dicyanamide and picolinate ligands

Two new dianion metal–organic complexes {[Cd(pcl)(H2O)2]2[Cd(pcl)2(dca)2]} (1) and [Ni(pcl)(dca)(H2O)]2 (2) (dca = dicyanamide, Hpcl = picolinic acid) have been synthesized and characterized by IR spectra and X-ray diffraction. In complex 1, the pcl− ligand both acts as chelate and bridging coordination ligands, while in complex 2, which only acts as a chelate ligand. In both cases, μ-1, 5-dca ligands bridge the metal ions to form square-grid like [M(dca)2]2 dimers. In complex 1, four of the trinuclear second building units {[Cd(pcl)(H2O)2]2[Cd(pcl)2(dca)2]} formed a honeycomb-like cavity, which further bridged by pcl− and dca to give a 2D network. While in complex 2, a channel-like supramolecular structure is formed by the connection of numerous hydrogen-bond interactions and weak interactions among the dinuclear motifs. Thermally gravimetric analyses and differential thermal analyses indicate that the two complexes are thermal stable.