Two New (3,6)-Connected Frameworks Based on an Unsymmetrical Tritopic Pyridyldicarboxylate Ligand and CO2 Dimer: Structures, Magnetic, and Sorption Properties

By reacting a tritopic ligand S-(4-carboxyphenyl)-nicotinic acid (H(2)cpna) with Co(NO3)(2) under different conditions, two new three-dimensional (3D) frameworks, [Co-2(cpna)(2)(H2O)(3)]-DMF.9(H2O) (1) and [Co-4(cpna)(4)(H2O)(8)] (2), have been obtained. They exhibit (3,6)-connected topological nets based on Co-2 clusters and Y-shaped trinodal cpna(2-) linkers. I presents a chiral anh net with the right-handed helical channels, while 2 shows an achiral framework with a rtl topology. The whole structures of 1 and 2 are constructed from 2D achiral layers interconnected by triangular cpna(2-) nodes. Notably, these layers contain two heterochiral vertical and parallel 2(1), helical chains for 1 and 2, respectively, and those chains are constructed with 4-connected tetrahedral or square planar centers in their respective layers. The magnetic studies indicate that 1 and 2 show antiferromagnetic and weak ferromagnetic exchanges transmitted through mu(2)-O-water/mu(1,3)-carboxylate bridges and carboxylate single mu(2)-O bridges between Co2+ ions in the Co-2 dimers, respectively. In addition, 1 displays microporous sorption for N-2 and CO2.