One-, Two-, and Three-Dimensional Coordination Polymers of Stilbenedicarboxylate with Different Metal Ions

Using trans-stilbene-4,4'-dicarboxylic acid (H2STDC) as bridging ligand, we have prepared four new coordination polymers with different transition metal ions, [Cu(STDC)(H2O)(py)(2)]center dot 2py (1), [Cd(STDC)(py)(2)]center dot 0.5py (2), [Co(STDC)(py)(2)]center dot 0.5py (3), and [Ni-2(STDC)(2)(py)(4)(H2O)]center dot py center dot 0.5H(2)O (4), by hydrothermal reactions in the presence of pyridine (py). In compound 1, single metal ions are linked into quasi-linear coordination chains by the organic ligand, and the chains are further assembled into 3D supermolecular architectures through strong O-H (coordinate water)center dot center dot center dot O (carboxylate) and weak C-H (py)center dot center dot center dot pi (benzene) hydrogen bonds. In compounds 2 and 3, which are isomorphous, binuclear motifs with double carboxylate bridges are linked into two-dimensional (4,4) coordination layers exhibiting 2-fold inclined interpenetration. The last compound exhibits an abnormal 5-fold interpenetration of diamond networks, in which the tetrahedral building unit is defined by a binuclear motif with triple (two carboxylates and a water) bridges. Although it is impossible to rationalize the formation of these distinct structures, the differences can be related to the different disposition of the coordinated py (and water in 1) molecules around metal ions. All these coordination polymers contain voids occupied by guest molecules. The stability and guest inclusion properties of 2, 3, and 4 have been investigated. While 3 and 4 undergo permanent framework collapse upon evacuation by heating, 2 exhibits reversible framework transformation upon evacuation/absorption of the guest molecules.