New metal–organic frameworks based on 2,5-thiophenedicarboxylate and pyridine- or imidazole-based spacers: syntheses, topological structures, and properties

Abstract

Solvothermal reactions of 2,5-thiophenedicarboxylate (H₂tdc) and N-auxiliary ligands in the presence of cobalt(II), zinc(II) and cadmium(II) salts have given rise to seven new metal–organic frameworks, namely, [Co₂(tdc)₂(bpp)₂(H₂O)·(H₂O)]_n (bpp = 1,3-bis(4-pyridyl)propane) (1), [Cd(tdc)(bpp)(H₂O)·(H₂O)₂]_n (2), [Zn₂(tdc)₂(bbi)₂·(H₂O)₂]_n (bbi = 1,1′-(1,4-butanediyl)bis(imidazole)) (3), [Co₄(tdc)₃(bimb)₄(H₂O)₅·(tdc)·(DMF)·(H₂O)₂]_n (bimb = 4,4′-bis(1-imidazolyl)biphenyl) (4), [Zn₄(O)(tdc)₃(bimb)₄·(H₂O)_5.25·(CH₃OH)]_n (5), [Cd₄(tdc)₄(bimb)₆·(H₂O)₂·(CH₃OH)₂·(DMF)₄] (6) and [Co₂(tdc)₂(tib)₂·(H₂tdc)·(DMF)₂] (tib = 1,3,5-tris(1-imidazolyl)benzene) (7), which exhibit structural diversity. Compounds 1–3 display 3D 2-fold interpenetrating 8-connected tsi net, 2D 4-connected sql net, and 3D 5-fold interpenetrating 4-connected dia net, respectively; while compound 4 features an extremely rare 3D 7-connected hxg-d cationic net and compound 5 adopts a 3D trinodal (4,4,6)-connected net with a new topology structure. For compounds 6 and 7, the topology in the structures were determined as 3D 3-fold interpenetrating 5-connected bnn net and 3D 2-fold interpenetrating binodal (3,5)-connected net, respectively. In the solid state, complexes 1, 4 and 5 exhibit nonlinear optical properties, and complex 5 has also been evaluated as a promising visible-light-driven photocatalyst for degradation of organic pollutants. The magnetic investigation of complexes 1 and 4 shows that there exists spin-canted antiferromagnetism for 1, whereas strong antiferromagnetic interaction and/or the depopulation of the higher energy Kramers doublets of the Co(II) centers are dominant in 4.