Ruthenium tris(bipyridine) chloride
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| Rubipy | |
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![[Ru(bipy)3]2+.](../../../upload/shared/thumb/f/fd/Rubipy.png/120px-Rubipy.png) ![[Ru(bipy)3]2+](../../../upload/shared/thumb/9/9a/Delta-ruthenium-tris%28bipyridine%29-cation-3D-balls.png/150px-Delta-ruthenium-tris%28bipyridine%29-cation-3D-balls.png) |
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| General| | |
| Systematic name | Ruthenium tris(2,2’-bipyridine)- dichloride hexahydrate |
| Other names | Ru-bipy Ruthenium-tris(2,2’-bipyridyl) dichloride Tris(bipyridine)ruthenium(II) chloride |
| Molecular formula | C30H24N6Cl2Ru.6H2O |
| Molar mass | 748.62 g/mol |
| Appearance | red-orange solid |
| CAS number | [50525-27-4] |
| Properties | |
| Density and phase | solid |
| Solubility in water | Soluble |
| Other solvents | Alcohols |
| Melting point | >300 °C |
| Structure | |
| Molecular shape | Octahedral |
| Dipole moment | 0 D |
| Hazards | |
| Main hazards | mildly toxic |
| R/S statement | R: none S: 22-24/25 |
| RTECS number | VM2730000 |
| Supplementary data page | |
| Spectral data | UV λmax = 428 nm (ε = 11,700), 454 nm (ε = 14,000) |
| Related compounds | |
| Related compounds | Ruthenium trichloride |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references |
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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−.
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[edit] 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.[1]. [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.
[edit] Photochemistry of [Ru(bipy)3]2+
Distinctively, [Ru(bipy)3]2+ absorbs UV 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 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.[2]
[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.[3] 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).
[edit] Safety
Metal bipyridine as well as related phenanthroline complexes are generally bioactive.
[edit] References
- ^ Broomhead, J. A.; Young, C. G. “Tris(2,2’-bipyridine)Ruthenium(II) Dichloride Hexahydrate” Inorganic Syntheses, 1990, volume 28, ISBN 0-471-52619-3
- ^ Bard, A. J.; Fox, M. A. “Artificial Photosynthesis: Solar Splitting of Water to Hydrogen and Oxygen” Accounts of Chemical Research 1995, volume 28, pages 141-145. DOI:10.1021/ar00051a007
- ^ Hara, M.; Waraksa, C.C.; Lean, J. T.; Lewis, B. A.; Mallouk, T. E. “Photocatalytic Water Oxidation in a Buffered Tris(2,2'-bipyridyl)ruthenium Complex-Colloidal IrO2 System” Journal of Physical Chemistry A, 2000, volume 104, pages 5275 - 5280. DOI:10.1021/jp000321x 10.1021/jp000321x
