Syntheses, Structures,\nand Characteristics\nof Four New Metal–Organic Frameworks Based on Flexible Tetrapyridines\nand Aromatic Polycarboxylate Acids

Abstract

Solvothermal reactions of tetrakis­(4-pyridyloxymethylene)­methane\n(TPOM) with deprotonated isophthalic acid (1,3-H₂bdc),\n5-hydroxyisophthalic acid (5-OH-H₂bdc), benzene-1,3,5-tricarboxylic\nacid (H₃btc), and benzene-1,2,4,5-tetracarboxylic acid\n(H₄btc) in the presence of zinc and cobalt salts produce\nfour new complexes, namely, {[Co₂(TPOM)­(bdc)₂(H₂O)₂]·(H₂O)₃}_<i>n</i> (<b>1</b>), {[Zn₂(TPOM)­(5-OH-bdc)₂]·(DMF)­(H₂O)₂}_<i>n</i> (<b>2</b>), {[Co₃(TPOM)­(btc)₂(H₂O)]·(H₂O)₄}_<i>n</i> (<b>3</b>), and {[Zn₂(TPOM)­(btc)₂]_<i>n</i> (<b>4</b>). Complexes <b>1</b> and <b>2</b> possess similar 2-fold interpenetrating\nthree-dimensional (3D) framework with bbf topology, but <b>1</b> crystallizes in an achiral space group, and <b>2</b> crystallizes\nin chiral space group and displays ferroelectric behavior. Complex <b>3</b> reveals a 3D framework with biunclear Co clusters, which\ndisplays weak antiferromagnetic character. In complex <b>4</b>, only H₄btc links Zn­(II) to generate a 3D porous framework,\nwith TPOM occupying the void space as countercation and template.\nIn addition, photochemical and ferroelectric properties of these new\ncomplexes in the solid state have been studied.