Syntheses, crystal structures, photoluminescent/magnetic properties of four new coordination polymers based on 2,3′,4,5′-biphenyltetracarboxylic acid

Abstract

Hydrothermal reactions of 2,3′,4,5′-biphenyltetracarboxylic acid (H₄bptc) with divalent copper, cobalt and nickel salts afford four novel coordination polymers, namely, {[Cu_2.5(μ₃-OH⁻)(bptc⁴⁻)(4,4′-bpy)(H₂O)]·1.5H₂O}_n (1), {[Cu₂(bptc⁴⁻)(H₂O)₄]·4H₂O}_n (2), {[Co_1.5(Hbptc³⁻)(1,4-bib)_0.5(H₂O)₅]·2H₂O}_n (3), and {[Ni₂(bptc⁴⁻)(1,4-bib)_1.5(H₂O)₅]·5H₂O}_n (4), in the presence of ancillary ligands (4,4′-bpy = 4,4′-bipyridine, 1,4-bib = 1,4-bis(1-imidazolyl)benzene). Their structures were determined by single-crystal X-ray diffraction analyses and further characterized by IR spectra, elemental analyses, powder X-ray diffraction (PXRD), and thermogravimetric (TG) analyses. Complex 1 exhibits a 3D framework with one-dimensional channels along the [111] direction, which can be defined as a (4,10)-connected deh1 net with the point Schläfli symbol of {3·4⁵}₂{3⁴·4¹²·5¹⁰·6¹⁴·7³·8²}. Compound 2 contains two interpenetrated 3D networks, each of which can be viewed as a (4,4)-connected mog moganite network with the point Schläfli symbol of {4·6⁴·8}₂{4²·6²·8²}. In Complex 3, both the Hbptc³⁻ and the 1,4-bib show μ₂ coordination mode, the former of which links two Co2 cations to form a 1D anionic chain and the latter of which links two Co1 cations to generate a 1D cationic chain. Interestingly, the 1D anionic chains are assembled through abundant strong hydrogen bonds to generate a 3D supermolecular structure with large one-dimensional channels occupied by the 1D cationic chains along the c axis. Complex 4 consists of two interpenetrated 3D networks, each of which can be simplified as a novel (3,4,4)-connected framework with the point Schläfli symbol of {4·6·8}{4·6³·8²}{6⁴·8·10}. In addition, the magnetic properties for 1, 2 and the photoluminescent properties for 3, 4 were investigated. The magnetic results show that there exist antiferromagnetic interactions between Cu(II) ions in 1 and 2.