Structural evolution and magnetic properties of CoII coordination polymers varied from 1D to 3D constructed by 1,4-bis(1,2,4-triazol-1-ylmethyl)benzene

Abstract

Seven Co^II coordination polymers, [Co(btx)₃(H₂O)₂](ClO₄)₂·(btx)·2H₂O (1), [Co(btx)₃(H₂O)₂](BF₄)₂·(btx)·2H₂O (2), [Co(btx)₂(H₂O)₂](NO₃)₂·2H₂O (3), [Co(btx)₂Cl₂] (4), [Co(btx)(BA)₂(H₂O)₂]·2HBA (5), [Co(btx)(IPA)] (6) and [Co₃(btx)₃(BTA)₂(H₂O)₂] (7) (btx = (1,4-bis(1,2,4-triazol-1-ylmethyl)benzene), HBA = benzoic acid, H₂IPA = isophthalic acid, H₃BTA = benzene-1,3,5-tricarboxylic acid), have been hydrothermally synthesized and characterized. 1 and 2 are isostructural and show a 1D Co–μ₂-btx–Co chain structure, in which btx acts as both a bridging and terminal ligand. 3 is also a 1D chain structure but different from 1 and 2. The Co^II ions are bridged by double μ₂-btx to form Co₂–btx₂ rings, which were further connected into 1D chains by sharing the Co^II ions of the rings. 4 exists as a 2D grid with (4,4) topology structure. When aromatic acid was introduced to the synthetic system, three other coordination polymers 5–7 were obtained. In 5, the 1D chain is as that of 1, except that the terminal ligand was replaced by BA⁻. 6 shows a two-fold parallel interpenetration framework featuring a 6-c uninodal net with (3³,4⁶,5⁵,6) Schlafli topological symbol. 7 is an interesting 3D framework, which contains a 2-nodal net motif with the unprecedented (3⁶,4²,5⁶,6)(3⁹,4⁹,5³)₂ topology structure. The influence of the varieties of the structures and magnetic properties are studied and discussed in detail.