1-D Open-channeled 3-D supramolecular self-assembled frameworks encapsulating unprecedented cyclic (H2O)8 clusters or solvent molecules

Two novel 1-D coordination polymers, {[Cu(Hhbd)(bpy)]center dot 3H(2)O}(n) (1) and {[Cu(Hhbd)(phen)]center dot H2O-MeOH}(n) (2) [Hhbd = alpha-hydroxybutanedioicate dianion, bpy = 2,2'-bipyridine, phen = 1,10-phenanthroline], were rationally designed and synthesized with an identical construction strategy, using Hhbd ligands as bridges and chelating aromatic ligands as terminal ligands. Interestingly, the chelating aromatic ligand and the -OH groups of the Hhbd ligand play an important role in the self-assembly of the polymeric coordination chain by providing potential supramolecular recognition sites for pi-pi aromatic stacking and hydrogen-bond interactions, resulting in the self-assembly of the molecular double chains to give a 3-D supramolecular framework with 1-D open channels. More significantly, in 1 the host framework encapsulates unprecedented centrosymmetric cyclic (H2O)(8) clusters that have a chair conformation and are connected into 1-D arrays by supramolecular association along the 1-D open channels. In contrast, the channels of 2 contain lattice water and disordered methanol molecules. TGA and XRPD show that the host frameworks of 1 and 2 are stable when the guest solvent molecules are removed from the channels. Variable-temperature magnetic susceptibility measurements for both complexes indicate the presence of weak antiferromagnetic exchange interactions between adjacent copper(II) ions. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005).