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

Abstract

A series of three novel metal-organic frameworks, [CdL]n (1), [ZnL]n (2), and [Cu2L2(DMF)2]·6H2O (3), were successfully prepared by a solvothermal method using 3,3′-dimethoxy-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 44 square lattice topology and a paddle-wheel Cu2(−CO2)4 as SBU. 113Cd 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 −2J = 286 cm−1.