Supramolecular architectures built of chain-like [PnCl5]2− (Pn = Sb, Bi) and protonated 2,2′-biimidazole: Synthesis, crystal structures and characterizations

A series of supramolecular species, PnCl5·(H4biim)·2H2O (Pn = Sb, 1; Bi, 2), [PnCl5]n·nH4bbim·2nH2O (Pn = Bi, 3; Sb, 4) (H2biim = 2,2′-biimidazole, H2bbim = 2,2′-bibenzimidazole) have been synthesized by the reactions of H2biim or H2bbim with PnCl3. Complexes 1–3 have been characterized by X-ray single crystal diffraction and IR analyses. Their structures feature the infinite [PnCl5]2− zigzag chains formed by the distorted corner-sharing PnCl6 octahedra. The hydrogen bonds of the bridging Cl atoms, which depend on the size of the protonated biimidazole counter-cations, have been found to play a crucial role in the extent of the octahedral distortion. The extensive XH···Cl (X = O, C) and NH···O hydrogen bonds between the infinite chains and the protonated biimidazole derivatives link the anionic and cationic parts into 3-D framework structures.

► PnCl5·L·2H2O (Pn = Sb, Bi, L = H4biim, H4bbim) were obtained by the reactions of L and PnCl3.
► They contained the [PnCl5]n2– chains formed by the distorted corner-sharing PnCl6 octahedra.
► The cation-dependent Cl bridging···H2O hydrogen bonds determined the extent of the octahedral distortion.
► The extensive XH···Cl (X = O, C) and NH···O hydrogen bonds constituted their 3-D framework structures.