Two acentric (6,3) topological 2-D frameworks with imidazole-containing tripodal ligand and their ferroelectric properties

Hydrothermal reaction of three-connecting ligands 1,3,5-tris(1-imidazolyl) benzene (tib) and MnSO4 or CoSO4 center dot 7H(2)O provides two new metal-organic frameworks, {[Mn(tib)(2)(H2O)(4)]SO4}(n) (1) and {[Co(tib)(2)(H2O)(4)]SO4}(n) (2). Single-crystal X-ray diffraction studies reveal that complexes 1 and 2 belong to the polar point group 3m, and have the same two-dimensional honeycomb networks with (6, 3) topology. The ferroelectric behavior investigation indicates that both compounds are typical ferroelectrics with an electric hysteresis loop showing a remnant polarization (P-r) of ca. 0.586 mu C cm(-2) and a coercive field (E-c) of 2000 V cm(-1) for 1 and P-r of ca. 0.208 mu C cm(-2) and a coercive field (E-c) of 2600 V cm(-1) for 2.