Three Novel Metal-Organic Frameworks with Different Topologies Based on 3,3′-Dimethoxy-4,4′-biphenyldicarboxylic Acid: Syntheses, Structures, and Properties

A series of three novel metal-organic frameworks, [CdL] n ( 1 ), [ZnL] n ( 2 ), and [Cu 2 L 2 (DMF) 2 ]·6H 2 O ( 3 ), were successfully prepared by a solvothermal method using 3,3′-dimethoxy-4,4′-biphenyldicarboxylic acid (H 2 L) as the ligands. X-ray crystallography analysis reveals that complex 1 exhibits a 3D framework with sra topology and a rare eight-coordinated Cd(II) with two bound methoxy groups as secondary building unit (SBU). For complex 2, a 2D coordination network with a four-coordinated Zn(II) as SBU was observed. Complex 3 also shows a 2D layered architecture with 4 4 square lattice topology and a paddle-wheel Cu 2 (−CO 2 ) 4 as SBU. 113 Cd NMR spectrum of 1 showed that the chemical shift of eight-coordinated Cd(II) appeared at δ −108.9 ppm. In addition, both 1 and 2 are robust coordination polymers with high thermal stabilities (>380 °C). Fluorescence measurements of 1 and 2 display medium strong emission peaks at 403 and 401 nm, respectively. Magnetic study of 3 exhibits a strong antiferromagnetic interaction between two Cu(II) ions with −2 J = 286 cm −1 .