chemistry

Tris(bipyridine)ruthenium(II) chloride

Tris(bipyridine)ruthenium(II) chloride is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Tris(bipyridine)ruthenium(II) chloride rather than just read about it. In short: Tris(bipyridine)ruthenium(II) chloride is the chloride salt coordination complex with the formula [Ru(bpy)3]Cl2. This polypyridine complex is a red crystalline salt obtained as the hexahydrate, although all of the properties of interest are in the cation [Ru(bpy)3]2+, which has received much attention because of its distinctive optical properties.

Key takeaways

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Reference excerpt

Tris(bipyridine)ruthenium(II) chloride is the chloride salt coordination complex with the formula [Ru(bpy)3]Cl2. This polypyridine complex is a red crystalline salt obtained as the hexahydrate, although all of the properties of interest are in the cation [Ru(bpy)3]2+, which has received much attention because of its distinctive optical properties. The chlorides can be replaced with other anions, such as PF6−.

Synthesis and structure

This salt is prepared by treating an 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(bpy)3]2+ is octahedral, containing a central low spin d6 Ru(II) ion and three bidentate bpy ligands. The Ru-N distances are 2.053(2), shorter than the Ru-N distances for [Ru(bpy)3]3+. The complex is chiral, with D3 symmetry. It has been resolved into its enantiomers. In its lowest lying triplet excited state the molecule is thought to attain lower C2 symmetry, as the excited electron is localized primarily on a single bipyridyl ligand.

Photochemistry of [Ru(bpy)3]2+

[Ru(bpy)3]2+ absorbs ultraviolet and visible light. Aqueous solutions of Ru(bpy)3Cl2 are orange due to a strong MLCT absorption at 452 ± 3 nm (extinction coefficient of 14,600 M−1cm−1). Further absorption bands are found at 285 nm corresponding to ligand centered π*← π transitions and a weak transition around 350 nm (d-d transition). Light absorption results in formation of an excited state have a relatively long lifetime of 890 ns in acetonitrile and 650 ns in water. The excited state relaxes to the ground state by emission of a photon or non-radiative relaxation. The quantum yield is 2.8% in air-saturated water at 298 K and the emission maximum wavelength is 620 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 forbidden and therefore often slow. Like all molecular excited states, the triplet excited state of [Ru(bpy)3]2+ has both stronger oxidizing and reducing properties than its ground state. This situation arises because the excited state can be described as an Ru3+ complex containing a bpy•− radical anion as a ligand. Thus, the photochemical properties of [Ru(bpy)3]2+ are reminiscent of the photosynthetic assembly, which also involves separation of an electron and a hole. [Ru(bpy)3]2+ has been examined as a photosensitizer for both the oxidation and reduction of water. Upon absorbing a photon, [Ru(bpy)3]2+ converts to the aforementioned triplet state, denoted [Ru(bpy)3]2+*. This species transfers an electron, located on one bpy ligand, to a sacrificial oxidant such as peroxodisulfate (S2O82−). The resulting [Ru(bpy)3]3+ is a powerful oxidant and oxidizes water into O2 and protons via a catalyst. Alternatively, the reducing power of [Ru(bpy)3]2+* can be 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). Derivatives of [Ru(bpy)3]2+ are numerous. Such complexes are widely discussed for applications in biodiagnostics, photovoltaics and organic light-emitting diode, but no derivative has been commercialized. Application of [Ru(bpy)3]2+ and its derivatives to fabrication of optical chemical sensors is arguably one of the most successful areas so far.

[Ru(bpy)3]2+ and photoredox catalysis Photoredox catalysis exploits [Ru(bpy)3]2+ as a sensitizer as a strategy for organic synthesis. Many analogues of [Ru(bpy)3]2+ are employed as well. These transformations exploit the redox properties of [Ru(bpy)3]2+* and its reductively quenched derivative [Ru(bpy)3]+.

Safety Metal bipyridine as well as related phenanthroline complexes are generally bioactive, as they can act as intercalating agents.

See also Primogenic Effect Tris(bipyridine)iron(II) chloride

References

Illustrations

Worked examples

Example 1 — a first encounter with Tris(bipyridine)ruthenium(II) chloride

Start with the simplest possible case. Write down what Tris(bipyridine)ruthenium(II) chloride claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Tris(bipyridine)ruthenium(II) chloride before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Tris(bipyridine)ruthenium(II) chloride ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Tris(bipyridine)ruthenium(II) chloride

In research: Tris(bipyridine)ruthenium(II) chloride appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Tris(bipyridine)ruthenium(II) chloride in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Tris(bipyridine)ruthenium(II) chloride is common in secondary-school and first-year university syllabi. It links to neighbouring topics Bipyridine complexes, Chlorides, Photochemistry, so understanding it makes those chapters shorter.
In everyday life: Look for Tris(bipyridine)ruthenium(II) chloride outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Tris(bipyridine)ruthenium(II) chloride in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Tris(bipyridine)ruthenium(II) chloride means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
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Frequently asked questions

What is Tris(bipyridine)ruthenium(II) chloride in simple terms?

Why does Tris(bipyridine)ruthenium(II) chloride matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Tris(bipyridine)ruthenium(II) chloride?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Tris(bipyridine)ruthenium(II) chloride.