Ruthenium tris bipyridine derivatives and their photocatalytic activity in [4+2] cycloadditions. An experimental and DFT study

[Display omitted] •Ruthenium derivatives with different bipyridine ligands are active species for [4+2] cycloaddition reactions.•Ru complexes are the photocatalyst for the cycloaddition reaction and not a photoinitiator as it has been proposed.•[4+2] cycloadditions can be performed with different su...

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Bibliographic Details
Published in:Catalysis today 2018-07, Vol.310, p.2-10
Main Authors: Rozenel, Sergio S., Azpilcueta, Carlos R., Flores-Leonar, Martha M., Rebolledo-Chávez, Juan P.F., Ortiz-Frade, Luis, Amador-Bedolla, Carlos, Martin, Erika
Format: Article
Language:English
Subjects:
[4 + 2] cycloaddition
Photocatalysis
Ruthenium bipyridine derivatives
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Summary:[Display omitted] •Ruthenium derivatives with different bipyridine ligands are active species for [4+2] cycloaddition reactions.•Ru complexes are the photocatalyst for the cycloaddition reaction and not a photoinitiator as it has been proposed.•[4+2] cycloadditions can be performed with different substrates and dienes, in either, acetonitrile or nitromethane•Studies show that the active species is [Ru(Bpy)3]3+ and the rate determining step is the formation of this species.•DFT calculations correctly predict redox potentials for different ligand environments. We report the study of a series of Ru-bipyridine (Ru-Bpy) complexes to correlate their photophysical and electrochemical properties to their performance in [4+2] cycloadditions, as a model reaction for electron transfer catalysis. Redox potentials, absorption and emission spectra, quantum yields and DFT calculations are presented to understand the catalytic transformation. The study shows that complex [Ru(Bpy)3](PF6)2 is the more active photocatalyst, giving complete conversion to the product after 2h reaction under white light. Any substitution in the para position of the Bpy ring decreases the reaction conversion. The [4+2] cycloaddition can be performed with different substrates and dienes, using either acetonitrile or nitromethane as solvents. Mechanistic studies suggest that the active catalyst for the transformation is [Ru(Bpy)3]3+ and that the rate determining step is the oxidation of [Ru(Bpy)3]2+ to generate the corresponding Ru3+ species.
ISSN:0920-5861
1873-4308
DOI:10.1016/j.cattod.2017.05.021