Two Zn(II) and Co(II) compounds with dicarboxylates and curved 4,4′-azopyridine ligands: Syntheses, crystal structures and gas sorption properties

Two new compounds Zn(PDA)(AZPY)·4H2O (1) and [Co(NDC)(AZPY)]2·2H2O·DMF (2) (H2PDA = pyridine-2,6-dicarboxylic acid, AZPY = 4,4′-azopyridine, H2NDC = 2,6-naphthalenedicarboxylic acid) were prepared through solvothermal reactions and characterized. Single crystal X-ray diffraction analysis indicates that compound 1 exhibits a one-dimensional chain structure, while compound 2 features a three-dimensional framework. Notably the bridged AZPY ligands involved in both compounds exhibit rare bent configurations. The thermal stability and gas sorption properties of compound 2 have also been studied. A normal amount (2.8 mmol g−1) of hydrogen uptake at 1 atm and −196 °C for compound 2 were observed, which can be attributed to the presence of micropores.

Graphical abstractTwo new compounds (1 and 2) constructed by aromatic dicarboxylic acids and AZPY linkers, in which the AZPY units are unusually bent. The ultramicropores involved in the structure of compound 2 are responsible for the higher uptake of H2 over N2.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Two new Zn(II) and Co(II) compounds containing mixed ligands were prepared through solvothermal methods. ► The Zn(II) and Co(II) compounds display 1D chain and 3D porous structures, respectively. ► The bridged AZPY ligands involved in both compounds exhibit rare bending configurations. ► The Co(II) compound has a higher uptake of H2 over N2 due to the presence of ultramicropores involved in the structure.