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Ruthenium tris(bipyridine) chloride
Ruthenium(II) tris(bipyridine) dichloride is the chemical compound with the formula [Ru(bipy)3]Cl2. This salt is obtained as the hexahydrate, although all of the properties of interest are in the cation [Ru(bipy)3]2+, which has received much attention because of its distinctive optical properties. The chlorides can be replaced with other anions, such as PF6−.
Additional recommended knowledge
Synthesis and structure
This orange crystalline salt is prepared by treating aqueous solution of ruthenium trichloride with 2,2'-bipyridine. In this conversion, Ru(III) is reduced to Ru(II), and hypophosphorous acid is typically added as a reducing agent.. [Ru(bipy)3]2+ is an octahedral coordination complex. The complex is chiral, with D3 symmetry. It has been resolved into its enantiomers, which are kinetically stable.
Photochemistry of [Ru(bipy)3]2+
Distinctively, [Ru(bipy)3]2+ absorbs UV light and visible light to give an excited state with a comparatively long lifetime of 600 nanoseconds. The excited state relaxes to the ground state by emission of a photon at the wavelength of 600 nm. The long lifetime of the excited state is attributed to the fact that it is triplet, whereas the ground state is a singlet state and in part due to the fact that the structure of the molecule allows for charge separation. Singlet-triplet transitions are often slow.
The triplet excited state has both oxidizing and reducing properties. This unusual situation arises because the excited state can be described as an Ru3+ complex containing a bipy- ligand. Thus, the photochemical properties of [Ru(bipy)3]2+ are reminiscent of the photosynthetic assembly, which also involves separation of an electron and a hole.
[Ru(bipy)3]2+ has been examined as a photosensitiser for both the oxidation and reduction of water. Upon absorbing a photon, [Ru(bipy)3]2+ converts to the aforementioned triplet state, denoted [Ru(bipy)3]2+*. This species transfers an electron, located on one bipy ligand, to a sacrificial oxidant such as [persulfate|S2O8]2-. The resulting [Ru(bipy)3]3+ is a powerful oxidant and oxidizes water into O2 and protons via a metal oxide catalyst. Alternatively, the reducing power of [Ru(bipy)3]2+* can harnessed to reduce methylviologen, a recyclable carrier of electrons, which in turn reduces protons at a platinum catalyst. For this process to be catalytic, a sacrificial reductant, such as EDTA4- or triethanolamine is provided to return the Ru(III) back to Ru(II).
The family of derivatives of [Ru(bipy)3]2+ is enormous. These complexes are widely used in biodiagnostics, photovoltaics and organic light-emitting diode.
Metal bipyridine as well as related phenanthroline complexes are generally bioactive.
Categories: Ruthenium compounds | Photochemistry | Coordination compounds
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Ruthenium_tris(bipyridine)_chloride". A list of authors is available in Wikipedia.|