Synthesis of a zinc(II) cage-like structure based on 1,4-bis((1H-imidazoyl-1-yl)methyl)benzene and 5-sulfoisophthalic acid

The reaction of 1,4-bis((1H-imidazoyl-1-yl)methyl)benzene (BIB) and 5-sulfoisophthalic acid (SPA) in a 1:1:1 ratio with zinc(II) ions in water produced a supramolecular cage-like structure of the composition {[Zn2BIB1.5SPA(OH)(H2O)]·1.75H2O}n. The structure as determined by X-ray crystallography contains two zinc(II) ions; one zinc(II) is four coordinate and approximately tetrahedral, whereas the second zinc(II) is five coordinate and based on a trigonal bipyramid. The two zinc(II) ions are connected by a μ2-hydroxyl unit and a μ2-carboxylate unit. Two of the central di-zinc(II) motifs are coupled together by the bridging 5-sulfoisophthalate subunit and this feature extends along the a-axis. The 1,4-bis((1H-imidazoyl-1-yl)methyl)benzene act like pillars to connect the rows of zinc(II) ions as viewed down the c-axis. The cavity formed supports inclusion of water molecules and the water channel extends in one dimension through the structure. The water molecules can be removed on heating to T = 373 K, and N2-uptake adsorption studies reveal the pore volume is 1.8 × 10−2 cm3 g−1 with a total BET surface area of 51.2 m2 g−1.

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