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 [Cu2L2(DMF)(2)]center dot 6H(2)O (3), were successfully prepared by a solvothermal method using 3,3'-dinietlioxy-4,4'-biphenyldicarboxylic acid (H2L) 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(-CO2)(4) as SBU. Cd-113 NMR spectrum of 1 showed that the chemical shift of eight-coordinated Cd(II) appeared at delta - 108.9 ppm. In addition, both 1 and 2 are robust coordination polymers with high thermal stabilities (> 380 degrees C). Fluorescence measurements of 1 and 2 display medium strong emission peaks at 403 and 401 nm, respectively. Magnetic study of 3 exhibits it strong antiferromagnetic interaction between two Cu(II) ions with -2J = 286 cm(-1).