Protonated Adenine and Cytosine Ribbons Stabilized by Dipicolinato Metal Frameworks

Stabilization of protonated adenine (ade) and cytosine (cyt) ribbons through hydrogen bonding interactions in a series of bis-dipicolinato metal(II) (metal = manganese, copper, zinc at +2 oxidation state) complexes are studied. Protonated assemblies of adenine as infinite chains in [1H, 9H-ade][3H, 7H-ade][MnL2]·3H2O and [1H, 9H-ade][3H, 7H-ade][CuL2]·3H2O (L = dipicolinato anion) are structurally characterized. The one-dimensional (1D) zigzag ribbons are comprised of alternate nonequivalent [1H, 9H-ade] and [3H, 7H-ade] adeninium cations. Protonated cytosinium cation aggregates with neutral cytosine to form pairs, and such pairs form tetrameric units with a length of 33.45 Å in the lattice of the seven coordinated manganese(II) complex [1H, 3H-cyt]2[MnL2(H2O)]·2cyt·6H2O. The discrete cations of cytosine stabilized by electrostatic, hydrogen bond, and stacking interactions within the inorganic layers build the closely packed organic−inorganic hybrid materials in the crystal lattice of the complexes [1H, 3H-cyt]2[CuL2]·5H2O and [1H, 3H-cyt]2[ZnL2]·5H2O.