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Home > Teams > Theoretical and Computational Photochemistry (PTC) > Research projects > Ruthenium cyclometallated complexes

Ruthenium cyclometallated complexes

Isabelle M. Dixon, Jean-Louis Heully

Ruthenium(II) polypyridine complexes are largely studied for their photophysical properties and their potential use for photoinduced electron and energy transfer. Experimental data span over 50 years, while specific theoretical studies have bloomed in the last decade, particularly thanks to the recent developments of density functional theory. Besides, spectroscopies of increasing complexity are also developed and show a recent revival of the topic, allowing the investigation of multistep mechanisms.

In this context, we got interested in bis(tridentate) polypyridine ruthenium(II) complexes containing N- or C-bound cycles, which were theoretically unexplored when this project was started. Terpy is the reference ligand (2,2’:6’:2"-terpyridine, L1) and is compared with 6-phenyl-2,2’-bipyridine (L2) and 1,3-di(2-pyridyl)benzene (L3). Complexes Ru(tpy)(L1)2+, Ru(tpy)(L2)+ and Ru(tpy)(L3)+ were first studied, as well as the homoleptic Ru(L2)2 and Ru(L3)2 (the latter two being unknown experimentally).

We perform DFT and TD-DFT calculations in order to model the complexes’ geometries, absorption and emission properties, as well as their redox properties. Frontier orbitals and natural charge analysis (NBO) are efficient tools to visualize and rationalize these properties. In complexes such as [RuN5C]+ or [RuN4C2], the presence of one or two covalent Ru-C bonds greatly modifies the classical [RuN6]2+ MO diagram, which typically gives rise to excited states of MLCT (metal-to-ligand charge transfer) or MC (metal centred) type. As a consequence of the stronger ligand field provided by the cyclometallating ligand to the metal, no 3MC minima could be localized, which is beneficial to the photophysical properties.

This project has led to one publication :

Dalton Trans. 2010, 39, 10959 link