A hybrid carboxylate-water decamer with a discrete octameric water moiety self-assembled in a 2D copper(II) coordination polymer

An octameric water moiety which consists of a chairlike water hexamer and two pendent water molecules in the 1,4-diaxial positions and shows a similar structure to the hydrocarbon (1r,4r)-1,4-dimethylcyclohexane, is unambiguously trapped in a 2D Cu(II) mixed-ligand coordination polymer, {[Cu-2(bpp)(2)(H2O)(2)(bpda)(2)]center dot 6H(2)O} (n) (1) (bpp = 1,3-bis(4-pyridyl)propane and H(2)bpda = 2,2'-biphenyldicarboxylic acid). The water octamer can be extended into a hybrid carboxylate-water decamer when carboxylic oxygen atoms from bpda(2-) are involved. Interestingly, the present hybrid decamer bears a similar structural topology to a butterfly (H2O)(10) cluster. The reversible dehydration/hydration of 1 is determined by X-ray powder diffraction studies.