Arene Ruthenium Cages: Boxes Full of Surprises

Self‐assembly of polypyridyl ligands with dinuclear arene ruthenium building blocks bridged by chlorido, oxalato or benzoquinonato ligands has allowed the construction of a wide range of cationic metalla complexes possessing different architectures and functionalities: (i) metalla‐rectangles showing host–guest possibilities and allowing intramolecular template‐controlled photochemical [2 + 2] dimerisation reactions; (ii) metalla‐prisms allowing encapsulation of molecules and giving rise to potential drug delivery systems; (iii) metalla‐boxes that can be used to stabilise the formation of G‐quadruplex DNA. This microreview covers the synthetic and structural aspects of these metalla complexes, as well as their most promising applications, with a particular focus on their potential biological applications. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)