Ruthenium (II) polypyridine complexes have been the focus of considerable attention over the last two decades. Their rich photophysical properties make them attractive candidates for applications as photosensitisers in light-harvesting devices (LHDs). Although duplicating the structure of natural systems, such as photosystem II (PSII), with a LHD would be extremely difficult, artificial systems capable of duplicating its function, ie. generating a charge-separated state, are of increasing interest (1,2) From a structural point of view, Ru(II) complexes of tridentate ligands are the targets of choice for incorporation into LHDs as they are achiral as compared to complexes based on Ru(bpy)₃²⁺ (bpy = 2,2'-bipyridine). From a functional point of view, however, they are not as useful as they typically have short excited-state lifetimes at room temperature (r.t.). Recently, we introduced several design principles and synthetic methodologies that prolong the r.t. excited state lifetime of Ru(tpy)₂²⁺-like complexes (tpy = 2,2':6',2''-terpyridine) (3-4). With r.t. luminescent Ru(II) complexes in hand, we set out to assemble larger r.t. luminescent assemblies. Oligonuclear Ru(II) complexes were obtained by a novel synthetic approach incorporating the ‘paddlewheel' motif of metal-metal tetra-carboxylate dimers (5).

1. Baranoff, E. et. al. Chem. Soc. Rev., 2004, 147. 2. Medlycott, E. A. et. al. Coord. Chem. Rev. 2006, 250, 1763. 3. Fang, Y.-Q. et. al. 2006 submitted for publication. 4. Wang, J. et. al. Chem. Eur. J. 2006, in press. 5. Cooke, M. W. et. al. Angew. Chem. Int. Ed. 2005, 44, 4881.