Crystalline hosts sandwich water sheets
A fluorine-containing copper complex (a clathrate hydrate) that sandwiches water sheets between its layers during crystallisation has been made.
Isamu Kinoshita from Osaka City University, Japan, and James Wright, at the University of Auckland, New Zealand, are interested in water confined to small spaces, and used x-ray analysis to decipher their sandwich structure.
Water behaves differently when it is in a confined environment
They found that each water layer is sandwiched between two planar arrays of the copper complex, and all the fluoride ligands point towards each other. This arrangement is retained when toluene-water solutions are used for crystallisation.
The distance between the layers can be adjusted, and toluene molecules are spaced at regular intervals within each water sheet. It is also possible to include other aromatic molecules such as benzene and xylene in the clathrate.
Wright thinks the water sandwich is caused by hydrogen bonding between molecules, and electronic stacking effects between layers.
This, the first example of a crystalline, two-dimensional toluene clathrate hydrate, will hopefully give some insight into the behaviour of water in closely confined environments.
R Miyamoto et al, Chem. Commun., 2005 (DOI: 10.1039/b505681k)