Molecular recognition of protonated cytosine ribbons by metal-oxalato frameworks

A series of inorganic-organic hybrid materials, (1H,3H-cyt)(2)[M(ox)(2)(H2O)(2)] [M(II) = Mn (1), Co (2), Cu (3), Zn (4)] have been synthesized by the reaction of cytosine with water-soluble oxalato complexes at acidic pH. Crystallographic studies reveal that all compounds display a supramolecular three-dimensional lamellar structure knitted by wide layers of metal-oxalato complexes and planar hydrogen-bonded one-dimensional (1D) ribbonlike aggregates of protonated cytosine. The crystal building resembles that previously reported (Garcia-Teran, J. P., et al. Inorg. Chem. 2007, 46, 3596) for the analogous 1H,9H-adeninium compound, and it is driven, in addition to electrostatic forces, by a complex network of hydrogen bonds. Nevertheless, the smaller size of the nucleobase and its different self-assembling ID pattern lead to dissimilar molecular recognition interactions between the organic and the inorganic frameworks, which are discussed in detail.