A Novel Water Octamer in Ce(dipic)2(H2O)3·4H2O: Crystallographic, Thermal, and Theoretical Studies

The crystal structure of Ce(dipic)2(H2O)3·4H2O reveals an unusual hydrogen-bonded water octamer. The centrosymmetric octamer is built by bridging two water molecules to the chair form of a water hexamer. The structure, predicted to be unstable relative to other octameric structures, is stabilized by hydrogen bonding with the carboxylate groups lining the cavity in the host crystal. The water cluster is removed by heating at 100 °C but can be reassembled by exposing the dehydrated form to an atmosphere saturated with water vapor.