Energy transfer in rhodium-ruthenium dimer-of-dimer assemblies.

A synthetic route to linear pairs of dirhodium tetracarboxylate 'paddlewheel' dimers bridged by Ru(II) complexes of tridentate 'terpyridine-like' ligands is presented. Three dimer-of-dimer assemblies were synthesized as well as two monomer-of-dimer assemblies. A bis(4'-(4-carboxyphenyl)terpyridine)Ru(II) complex spanning two dirhodium dimers displays a 26. {\AA} sepn. between the dimers in its x-ray crystal structure. Increased electronic interaction is found for the dimer of dimers without the Ph groups using bis(4'-(4-carboxy)-terpyridine)Ru(II) as the bridging complex. The addn. of one or two of the dirhodium dimers to the Ru photosensitizer increases the molar absorptivity in an additive fashion. In the emission profile, the dirhodium tetracarboxylates act as energy transfer traps as the Ru-based 3MLCT (MLCT = metal-to-ligand charge-transfer) excited state is efficiently quenched by energy transfer from the Ru core to the dirhodium periphery, both at room temp. and low (77 K) temp. [on SciFinder(R)]


Soumis le 12 avril 2018