Supramolecular isomerism in two nickel(II) coordination polymers constructed with the flexible 2-carboxyphenoxyacetate linker: Syntheses, structure analyses and magnetic properties

Two binary nickel (II) supramolecular isomers, namely 1D-Ni and 2D-Ni with the same formula [Ni(2-cpa)(2)(-H2O)](n) (2-H(2)cpa = 2-carboxyphenoxyacetic acid), have been prepared by different synthetic methods and systematically characterized. Single-crystal X-ray diffraction analysis shows that the central Ni-II ion of 1D-Ni is located in a deformed square-pyramid bonded by one water and two 2-cpa anionic ligands. Each 2-cpa exhibits tetradentate bridging chelate-mu(2) coordination mode and joins neighbouring Ni-II ions to form a 1-D zigzag chain structure. While for 2D-Ni, the Ni-II center is in a distorted octahedral geometry surrounded by one water and three 2-cpa. The 2-cpa displays pentadentate double bridging chelate-mu(3) coordination pattern and links adjacent Ni-II ions to generate a corrugated (4,4)-connected layer. The magnetic measurements indicated that there are both weak ferromagnetic coupling between neighbouring Ni(II )ions in 1D-Ni and 2D-Ni. In addition, the driving force for the formation of two isomers have been carefully analyzed and discussed.

Automated summary

Two binary nickel (II) supramolecular isomers, 1D-Ni and 2D-Ni, with the same chemical formula have been prepared and characterized, showing different structures through single-crystal X-ray diffraction analysis. Magnetic measurements indicate weak ferromagnetic coupling between the two isomers, driven by different synthetic methods and ligand coordination effects.