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.

Graphical abstractReactions of Cd(II) and Ni(II) with picolinic acid (Hpcl) and sodium dicyanamide (Nadca) result in the formation of two new coordination complexes with different structures. The complex {[Cd(pcl)(H2O)2]2[Cd(pcl)2(dca)2]} (1) forms a 2D network with honeycomb-like cavites, whereas [Ni(pcl)(dca)(H2O)]2 (2) forms a channel-like supramolecular structure based on a dinuclear unit.Figure optionsDownload full-size imageDownload as PowerPoint slide