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

Abstract

Hydrothermal reaction of three-connecting ligands 1,3,5-tris(1-imidazolyl) benzene (tib) and MnSO4 or CoSO4·7H2O 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 μC cm(-2) and a coercive field (E(c)) of 2000 V cm(-1) for 1 and P(r) of ca. 0.208 μC cm(-2) and a coercive field (E(c)) of 2600 V cm(-1) for 2.