Solid-State Structures of Three Zinc(II) Coordination Polymers with 3-(1H-Imidazol-1-yl)propanoate Linkers Prepared in Water

Abstract

Coordination polymers of zinc(II) with three readily accessible 3-(1H-imidazol-1-yl)propanoate ligands are prepared by combining aqueous solutions of the ligands and zinc(II) salts, resulting in a precipitation of the respective coordination polymers. While sodium 3-(1H-imidazol-1-yl)propanoate and sodium 3-(2-phenyl-1H-imidazol-1-yl)propanoate initially yield amorphous precipitates that can be converted to crystalline materials upon prolonged heating, the use of sodium 3-(2-methyl-1H-imidazol-1-yl)propanoate results in the immediate formation of a crystalline coordination polymer. All three coordination polymers are structurally characterized by single-crystal X-ray diffraction. The crystal water in one coordination polymer can be removed without losing the crystallinity of the sample and this process is studied by infrared spectroscopy. The interpretation of the corresponding infrared spectra is supported by theoretical calculations. Furthermore, the solubility in water and buffer solutions and the potential porosity of the coordination polymers are investigated, revealing their nonporous character for CO₂, N₂, and CH₄.