Synthesis, Structure, and Magnetic Properties of a Copper(II) Metal-Organic Framework with Biphenyl-2,2′,4,4′-tetracarboxylic Acid

The 2D Cu^II metal-organic framework [Cu₂(bptc)(H₂O)₄]_n·4nH₂O (1) (H₄bptc = biphenyl-2,2′,4,4′-tetracarboxylic acid) was hydrothermally synthesized and characterized by single-crystal X-ray diffraction and magnetic measurements. In the structure, bptc^4– serves as a twisted Π-shaped organic building block to connect paddlewheel [Cu₂(COO)₄] dinuclear units and mononuclear units through 2-/2′-carboxylate and 4-/4′-carboxylate, respectively. According to the magnetic analysis using a dimer-plus-monomer model, strong antiferromagnetic coupling is operative within the dinuclear unit (J = –311 cm^–1 based on H = –JS₁S₂), and the compound behaves like a mononuclear molecule at low temperature.