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Ionic Liquids as a Novel Medium for Photochemical Reactions. Ru(bpy)32+/Viologen in Imidazolium Ionic Liquid as a Photocatalytic System Mimicking the Oxido-Reductase Enzyme

Authors

  • Mercedes Álvaro,

    1. Instituto de Tecnología Química y Departamento de Química, Universidad Politécnica de Valencia, Camino de Vera s/n, 46022 Valencia, Spain
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  • Esther Carbonell,

    1. Instituto de Tecnología Química y Departamento de Química, Universidad Politécnica de Valencia, Camino de Vera s/n, 46022 Valencia, Spain
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  • Belen Ferrer,

    1. Instituto de Tecnología Química y Departamento de Química, Universidad Politécnica de Valencia, Camino de Vera s/n, 46022 Valencia, Spain
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  • Hermenegildo Garcia,

    Corresponding author
    1. Instituto de Tecnología Química y Departamento de Química, Universidad Politécnica de Valencia, Camino de Vera s/n, 46022 Valencia, Spain
    • To whom correspondence should be addressed: Instituto de Tecnología Química y Departamento de Química, Universidad Politécnica de Valencia, Camino de Vera s/n, 46022 Valencia, Spain. Fax: 34-96-3879349; e-mail: hgarcia@qim.upv.es

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  • José R. Herance

    1. Universidad Autónoma de Barcelona, Unidad Química Orgánica, 08193 Bellaterra, Barcelona, Spain
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  • This paper is part of a special issue dedicated to Professor J. C. (Tito) Scaiano on the occasion of his 60th birthday.

ABSTRACT

Ionic liquids are suitable media which stabilize charged intermediates favoring those mechanisms that occur through charge separation. We have used ionic liquids to develop a photocatalytic system to perform the reduction of a carbonyl group to alcohol, thus mimicking the behavior of the reductase enzymes. The photochemical cycle is based on the well-known electron transfer from the Ru(bpy)32+ complex in its excited state, acting as electron donor to MV2+, which acts as electron acceptor. The initial electron transfer process can be promoted upon selective Ru(bpy)32+ excitation by visible light. By means of laser flash photolysis we have provided evidence of the nature and lifetimes of the intermediates involved in the photocatalytic system. Thus, the initial electron transfer between Ru(bpy)32+ triplets and viologen MV2+ forms the MV*+ radical cation, which upon accepting an H* atom from a suitable hydrogen atom donor, forms the corresponding dihydropyridine MVH+ reducing agent.

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