Syntheses, Structures, and Characteristics of Four New Metal–Organic Frameworks Based on Flexible Tetrapyridines and Aromatic Polycarboxylate Acids

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