New Zinc Phosphates Decorated by Imidazole-Containing Ligands

Four new zinc phosphates [Zn(HPO4)(C6H9N3O2)] (1), [Zn(HPO4)(C4H6N2)]·H2O (2), [Zn2(HPO4)2(C14H14N4)]·2H2O
(3), and [Zn(HPO4)(C14H14N4)] (4) were synthesized in the presence of d-histidine, 1-methylimidazole, 1,4-bis(imidazol-1-ylmethyl)benzene (L1), and 1,2-bis(imidazol-1-ylmethyl)benzene (L2), respectively, and their structures
were determined by X-ray crystallography. The inorganic framework of compounds 1, 2, and 3 is composed of
vertex-shared ZnO3N and HPO4 tetrahedra that form four rings, which, in turn, are linked to generate a one-dimensional ladder structure. In 1 and 2 the organic groups (monoimidazole ligand) are located at each side of the
ladders, while in 3 the bisimidazole ligand, 1,4-bis(imidazol-1-ylmethyl)benzene, links the ladders together to form
a novel 2D structure. Compound 1 is the first zinc phosphate framework to be templated by an N-bonded chiral
amino acid. In 4 the zero-dimensional four rings are joined together by the linear bridging ligand, 1,2-bis(imidazol-1-ylmethyl)benzene, to generate a one-dimensional framework with a new face-to-face structural motif. The 3D
structure of compound 4 is stabilized by hydrogen-bonding, π−π interactions, and C−H···π interactions. The
approach of incorporating multifunctional ligands into zinc phosphate frameworks and linking the inorganic zinc
phosphates subunits by an organic ligand provides opportunities for the design of new inorganic−organic open
frameworks.