Molecules confined in a coordination cage show unusual physical behaviour, claim researchers in Japan. 

Makoto Fujita at the University of Tokyo and colleagues say molecular cages, made using the metal coordination of multi-dentate ligands, can force encapsulated molecules to interact.  The coordination cages are water soluble and have an inner hydrophobic cavity.  According to Fujita, the cavity can recognise and encapsulate organic guest molecules.

The cavity effectively creates a reaction vessel in which guest molecules are forced into close proximity to each other allowing them to interact or react, said Fujita.

Team member Michito Yoshizawa said, 'the control of the organization of molecules inside these cavities and, by this way, the control of these interactions will allow us to tune and exhibit new physical properties.' 

Michael Ward, a supramolecular chemist at the University of Sheffield, UK, said the assemblies are beautiful structures in their own right. 'Unusual physical behaviour is emerging from the closely-packed guests that would not occur under normal conditions,' said Ward. 'The design, synthesis and beautiful structures of these cages would be remarkable enough; but their additional applications in substantially modifying the reactivity of small compounds by confinement make them some of the most exciting compounds currently being studied.'

Ian Gray