Three isomorphous two-dimensional coordination polymers generated from a benzimidazole bridging ligand and ZnX₂ (X = Cl, Br and I)

A novel bridging asymmetric benzimidazole ligand, 4-{2-[3-(pyridin-4-yl)­phenyl]-1H-benzimidazol-1-yl­methyl}­benzoic acid, was used to construct three isomorphous two-dimensional coordination polymers, namely catena-poly[chlorido(μ₃-4-{2-[3-(pyridin-4-yl)­phenyl]-1H-benzimidazol-1-yl­methyl}­benzoato)­zinc(II)], [Zn(C₂₆H₁₈N₃O₂)Cl]_n, (I), and the bromide, (II), and iodide, (III), analogues. Neighbouring two-dimensional networks are stacked into three-dimensional frameworks via inter­layer π–π inter­actions. The luminescent properties of (I)–(III) were investigated and they display an obvious red-shift in the solid state at room temperature.

Two one-dimensional coordination polymers generated from a new benzimidazole bridging ligand and CdX₂ (X = Br and I)

The novel asymmetric bridging ligand 1-[(pyridin-3-yl)methyl]-2-[4-(pyridin-3-yl)phenyl]-1H-benzimidazole (L) has been used to construct the coordination polymers catena-poly[[[dibromidocadmium(II)]-μ₃-1-[(pyridin-3-yl)methyl]-2-[4-(pyridin-3-yl)phenyl]-1H-benzimidazole] monohydrate], {[CdBr₂(C₂₄H₁₈N₄)]·H₂O}_n, (I), and catena-poly[[diiodidocadmium(II)]-μ₃-1-[(pyridin-3-yl)methyl]-2-[4-(pyridin-3-yl)phenyl]-1H-benzimidazole], [CdI₂(C₂₄H₁₈N₄)]_n, (II). Com­pounds (I) and (II) are closely related one-dimensional polymers based on 16- and 20-membered macrocycles along the chains, but they are not isomorphous. The chains are crosslinked into a two-dimensional network via hydrogen bonds and π–π inter­actions in (I), and into a three-dimensional framework through π–π inter­actions in (II). One well-ordered solvent water mol­ecule per asymmetric unit is included in (I) and forms O...Br hydrogen bonds.