Syntheses, Structures, and Properties of Coordination Polymers with 2,5-Dihydroxy-1,4-Benzoquinone and 4,4′-Bipyridyl Synthesized by In Situ Hydrolysis Method

Abstract

The coordination polymers (CPs) with binary ligands, including 2,5-dihydroxy-1,4-benzoquinone (H2DHBQ) and 4,4′-bipyridyl (bpy), were synthesized using in situ hydrolysis of 2,5-dimethoxy-1,4-benzoquinone (DMBQ). Three kinds of CPs were obtained depending on the metal ions. For M = Mn and Zn, a 1D zigzag chain structure with cis conformation ( cis -1D-M ) was obtained, whereas Co, Ni, and Cu compounds afforded a 2D net structure with trans conformation ( trans -2D-M ) with a 1D pore. A linear chain structure was also obtained for M = Cu. Magnetic susceptibility (χ M T ) at 300 K in cis -1D-Mn and trans -2D-Co was evaluated to be 4.421 and 2.950 cm 3 K mol –1 , respectively, indicating that both compounds are in the high-spin state. According to the N 2 adsorption isotherms at 77 K, trans -2D-Ni showed microporosity with the BET surface area of 177 m 2 g –1 , whereas the isomorphic trans -2D-Co rarely adsorbed N 2 at 77 K. This phenomenon was explained by the difference of diffusion kinetics of the adsorbent molecules, which was supported by the CO 2 adsorption isotherms at 195 K. The optical band gaps of cis -1D-Mn , cis -1D-Zn , trans -2D-Co , and trans -2D-Ni were estimated to be 1.6, 1.8, 1.0, and 1.1 eV, respectively, by using UV–vis–NIR spectroscopy.