Four Transition Metal Coordination Polymers based on an Aromatic Multi‐carboxylic Acid as Ligand: Syntheses, Crystal Structures, and Fluorescent/Magnetic Properties

Abstract

AbstractFour compounds, namely, [Zn(H2L)2·4H2O] (1), [Cu(HL)·(H2O)]·H2O (2), [Ni3L2(bpy)2·12H2O]·4H2O (3), and [Co3L2(bpy)2·12H2O]·4H2O (4) [H3L = 4, 4′‐[(5‐carboxy‐1, 3‐phenylene)bis(oxy)]dibenzoic acid], were synthesized under solvothermal conditions by employing a semi‐rigid aromatic multi‐carboxylic acid ligand (H3L) and ancillary nitrogen ligand (bpy = 4, 4′‐bipyridine). X‐ray diffraction studies revealed that complexes 1, 3, and 4 show zero‐dimensional (0D) structures, which were further extended to distinct 3D supramolecular nets by extensive hydrogen‐bond interactions. However, in compound 2, 1D chains of square‐shaped pores were linked together by HL2– ligands to generate a 2D porous layer along the ac plane. Comparison of the structures indicated that not only the conformation of the functional ligand, but also the ancillary ligand helped in structural determination of the compounds. Compound 1 exhibited solid fluorescence emission originating from an intraligand π→π* transition. Magnetic susceptibility measurements demonstrated that compound 2 exhibited antiferromagnetic coupling between adjacent copper(II) ions, with the corresponding J values of –141.84 cm–1. Furthermore, the thermal behaviors of the complexes 1–4 were studied by thermogravimetric analysis.