1D chains, 2D networks and 3D interdigitated frameworks of isoorotic acid or 4,4'-bipyridyl and isoorotic acid: syntheses, structures, and sorption properties

Abstract

Five new coordination polymers, {[Cu(H(2)iso)(2)]center dot 2H(2)O}(n) (1), {Mn(Hiso)(H2O)(3)}(n) (2), {Mn(Hiso)(H2O)(2)}(n) (3), {[Cu(Hiso)(4,4'-bipy)(H2O)]center dot 2H(2)O}(n) (4) and {[Ni(Hiso)(4,4'-bipy)(H2O)}]center dot 0.5(4,4'-bipy)}(n) (5) (H(3)iso = 2,4-dihydroxypyrimidine-5-carboxylic acid or isoorotic acid; 4,4'-bipy = 4,4'-bipyridyl), have been synthesized using hydrothermal as well as room temperature solvent diffusion techniques and structurally characterized. Compounds 1 and 2 are 1D coordination polymers which are further connected by O-H center dot center dot center dot N, O-H center dot center dot center dot O hydrogen bonding interactions forming 3D supramolecular frameworks. Compound 3 is a 2D coordination polymer where 1D chains of {Mn(Hiso)(H2O)(2)} are linked by an oxo (mu(2)-O) bridge. Compound 4 consists of isoorotic acid and 4,4'-bipy, a mixed linker system. It forms a 2D sheet like extended structure and these sheets stack on each other to give a 3D supramolecular porous structure. In case of 5, Ni(Hiso) 1D chains are bridged by 4,4'-bipy forming a 2D network and networks are further interdigitated through hydrogen bonding interactions resulting in a 3D supramolecular framework with a 1D channel where 4,4'-bipy molecules are accommodated as guests. Compound 5 undergoes a structural contraction after the removal of the guest 4,4'-bipy and metal bound water molecules and shows a non-porous behaviour toward N-2 at 77 K. However, at 195 K, it shows a stepwise uptake for both CO2 and C2H2, suggesting the flexible nature and polar pore surface of the framework.