Tris(bipyridine)ruthenium(II) chloride

Chembox new
IUPACName =
ImageFile = Tris(bipyridine)ruthenium(II) chloride.png OtherNames = Ru-bipy
Ruthenium-tris(2,2’-bipyridyl) dichloride

Section1 = Chembox Identifiers
CASNo = 50525-27-4
RTECS = VM2730000
Section2 = Chembox Properties
Formula = C₃₀H₂₄N₆Cl₂Ru·6H₂O
Section2 = Chembox Properties
MolarMass = 748.62 g/mol
Appearance = red-orange solid
Density = solid
Solubility = Soluble
MeltingPt = >300 °C
Section3 = Chembox Structure
MolShape = Octahedral
Dipole = 0 D
Section7 = Chembox Hazards
MainHazards = mildly toxic
RPhrases = none
SPhrases = 22-24/25
Section8 = Chembox Related
OtherCpds = Ruthenium trichloride

Tris(bipyridine)ruthenium(II) 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⁻.

ynthesis 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. [Broomhead, J. A.; Young, C. G. “Tris(2,2’-bipyridine)Ruthenium(II) Dichloride Hexahydrate” Inorganic Syntheses, 1990, volume 28, ISBN 0-471-52619-3] . [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.(<- in which solvent? in water it was measured to about 400ns) 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. [cite journal | author = A. J. Bard and M. A. Fox | title = Artificial Photosynthesis: Solar Splitting of Water to Hydrogen and Oxygen | year = 1995 | journal = Acc. Chem. Res. | volume = 28 | issue = 3 | pages = 141–145 | doi=10.1021/ar00051a007]

[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. [cite journal | author = M. Hara, C. C. Waraksa, J. T. Lean, B. A. Lewis and T. E. Mallouk | title = Photocatalytic Water Oxidation in a Buffered Tris(2,2'-bipyridyl)ruthenium Complex-Colloidal IrO2 System | year = 2000 | journal = J. Phys. Chem. A | volume = 104 | issue = 22 | pages = 5275–5280 | doi=10.1021/jp000321x] 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 EDTA^4- or triethanolamine is provided to return the Ru(III) back to Ru(II).

Derivatives

The family of derivatives of [Ru(bipy)₃] ²⁺ is enormous. These complexes are widely used in biodiagnostics, photovoltaics and organic light-emitting diode.

afety

Metal bipyridine as well as related phenanthroline complexes are generally bioactive.

UV-Vis Spectrum

At C = 0.01 g/L in Water -> E(452 +/- 3 nm)= 11,500 (Minimum)

References