DOI: 10.1002/chem.200801790 Microwave Synthesis of a Rare [Ru 2 L 3 ] 4 + Triple Helicate and Its Interaction with DNA Christopher R. K. Glasson, [a] George V. Meehan,* [a] Jack K. Clegg, [b] Leonard F. Lindoy,* [b] Jayden A. Smith, [a] F. Richard Keene, [a] and Cherie Motti [c] Polypyridyl ruthenium(II) complexes display a range of characteristic properties that include inertness, redox prop- erties, excited state reactivity, luminescence emission, and excited state lifetimes. [1, 2] As a consequence metallosupra- molecular examples incorporating polypyridyl ruthenium(II) moieties have been incorporated into molecular machines, [3] molecular electronic components, [4–6] solar cell dye sensitiz- ers, [5, 7] luminescence sensors, [5] novel drug analogues, and DNA binders. [5, 8] A range of reports have described the syn- thesis of ruthenium(II) structures using self-assembly pro- cesses. These include metallocycles, [9] cubes, [10] heterometal- lic, [11, 12] and homometallic [13] helicates. It is now well established that di-bidentate ligand systems may interact with octahedral metal ions to yield triple-heli- cal species of the type [M 2 L 3 ] n + . [14] However, helicate forma- tion may be hindered when employing inert metal ions by the kinetic formation of polymeric material. In a paper by Pascu et al. [13] the interaction of ruthenium(II) with a bis-di- imine ligand led to the formation of the only [Ru 2 L 3 ] 4 + heli- cate reported so far. This reaction gave the product in 1 % yield, reflecting the inherent difficulty of working with this kinetically-inert metal ion. To combat such low yields, a number of elegant synthetic strategies have been successful- ly employed. Fletcher et al. [15] utilized a tethered tris-bipyr- idyl ligand to kinetically enhance the formation of the facial geometric isomer in a stepwise synthetic approach to a het- erometallic helicate. In further reports Torelli et al. [11, 12] out- lined the use of a trisACHTUNGTRENNUNG(diimine)ruthenium(II) complex as a novel labile partner to synthesize several Ru II -f-block het- erometallic helicates in high yield. Recently, we reported the successful synthesis of an [Fe 4 L 6 ] 8 + tetrahedron based on the interaction of iron(II) and the rigid quaterpyridine derivative L (Figure 1). [16] This result prompted an investigation of the use of other transi- tion-metal ions in analogous metal-directed assembly pro- cesses with L. We now report the synthesis and characteriza- tion of a new [Ru 2 L 3 ] 4 + helicate based on the interaction of ruthenium(II) and L (Figure 1). The results of DNA binding experiments with [Ru 2 L 3 ] 4 + are also presented. Initially, a self-assembly reaction was attempted by em- ploying RuCl 3 and L in a 2:3 ratio in ethanol under reflux for two weeks. This approach led to the production of a complex mixture of products that included brown intracta- ble polymeric material. When the reaction was repeated [a] C. R. K. Glasson, Prof. G. V. Meehan, Dr. J. A. Smith, Prof. F. R. Keene School of Pharmacy and Molecular Sciences James Cook, University, Townsville 4811, (Australia) E-mail: george.meehan@jcu.edu.au [b] Dr. J. K. Clegg, Prof. L. F. Lindoy School of Chemistry, University of Sydney, Sydney 2006 (Australia) E-mail : lindoy@chem.usyd.edu.au [c] C. Motti The Australian Institute of Marine Science Townsville 4810 (Australia) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.200801790. Figure 1. The interaction of L with RuCl 3 and FeCl 2 to yield the helicate [Ru 2 L 3 ] 4 + and the tetrahedron [Fe 4 L 6 ] 8 + , respectively. Chem. Eur. J. 2008, 14, 10535 – 10538  2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 10535 COMMUNICATION