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 （lr,4r）-1,4-dimethylcyclohexane, is unambiguously trapped in a 2D Cu（II） mixed-ligand coordination polymer, {[Cu2（bpp）2（HzO）2（bpda）2]＇6H2O}n （1） （bpp = 1,3-bis（4-pyridyl）propane and H2bpda = 2,2＇-biphenyldicarboxylic acid）. The water octamer can be extended into a hybrid carboxylate-water decamer when carboxylic oxygen atoms from bpda2- 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.