Four cobalt(II) complexes constructed from a butterfly-shaped tetracarboxylic acid with N-donor ligands: Structures, magnetism and influence of coordination modes on dihedral angles

Four coordination complexes based on (1,1′,2′1″-terphenyl)-4,4′4″,5′-tetracarboxylic acid (H4ttac), {[Co2(H2ttac)2(H2O)5]·(H2O)10}n (1), [Co2(ttac)(pyridine)(H2O)3]n (2), {[Co2(ttac)(4,4′-bipy)1.5(H2O)]·(H2O)}n (3), and {[Co3(ttac)2(bpe)3(H2O)2]·(H2O)6}n (4), (bpe = 1,2-bis(4-pyridyl)ethene, 4,4′-bipy = 4,4′-bipyridine), have been hydrothermally synthesized and structure characterization. Complex 1 exhibits a one-dimension chain with a cavity of 12.75 × 12.84 Å2, and further stacks into a 3D framework through hydrogen bonds. 2 forms a (4,6)-connected 2D layer with the symbol of (32.42.5.6)2(32.46.52.64.7). 3 Is a 3D (4,4,4,5)-connected framework with the Schlafli symbol of (42.6.82.10)2(42.63.85)2(62.83.12)2. 4 displays a 2D double-layered grid with trinuclear units to construct a (4,4,6)-connected net marking the symbol of (4.84.12)2(43.62.8)2(44.62.88.12). The study on dihedral angles between the two monocarboxylic benzene rings in H4ttac ligands in complexes 1–4 shows that the change of dihedral angles from 62.85°, 66.24°, 56.41° to 59.69° mainly originated from the coordination numbers of their monocarboxylic groups from 3, 4, 2 to less than 2. Temperature-dependent magnetism susceptibility measurements show a ferromagnetic behavior for complex 4 and antiferromagnetic characters for complexes 1–3.