The structures and properties of zinc(II) and cadmium(II) coordination polymers based on semi-rigid phenylenediacetate and 1,4-bis(2-methylimidazol-1-ylmethyl)benzene linkers

A systematic investigation into the reactions of o- and p-phenylenediacetic acid with zinc(II) and cadmium(II) salts in the presence of the semi-rigid 1,4-bis(2-methylimidazol-1-ylmethyl)benzene (pbmeix) co-ligand is reported. Five new coordination polymers – [Zn(μ-opda)(μ-pbmeix)_0.5]_n 1, {[Zn(μ-ppda)(μ-pbmeix)]·H₂O}_n 2, {[Zn(μ-ppda)(μ-pbmeix)]∙0.5pbmeix·H₂O}_n 3, {[Cd(μ-opda)(μ-pbmeix)]·0.5DMF}_n 4 and [Cd(μ-ppda)(μ-pbmeix)_0.5]_n 5 (o/ppda = 1,2-/1,4-phenylenediacetate) – have been prepared and structurally characterised. Compounds 1 and 5 were found to form three-dimensional coordination networks, 2 forms a two-dimensional structure whereas both 3 and 4 form one-dimensional nanotubular structures. Compounds 1 and 4 are opda complexes in which the dicarboxylate shows a tridentate coordination mode in 1 and a tetradentate coordination mode in 4. Compounds 2, 3 and 5 are ppda complexes in which the dicarboxylate adopts bidentate (2, 3) and hexadentate (5) coordination modes. The structure of 2 contains interpenetrated 2D frameworks and is a polycatenane with ppda linkers from one framework passing through Zn₂(μ-pbmeix)₂ rings from a neighbouring framework. The thermal stability of complexes 1–4 and luminescence properties of complexes 1 and 4 are also reported.