[RhIII(dmbpy)2Cl2]+ as a Highly Efficient Catalyst for Visible‐Light‐Driven Hydrogen Production in Pure Water: Comparison with Other Rhodium Catalysts1. Issue 2 (21st November 2012)

• Record Type: Journal Article
• Authors: Stoll, Thibaut; Gennari, Marcello; Serrano, Isabel; Fortage, Jérôme; Chauvin, Jérôme; Odobel, Fabrice; Rebarz, Mateusz; Poizat, Olivier; Sliwa, Michel; Deronzier, Alain; Collomb, Marie‐Noëlle
• Is Part Of: Chemistry. Volume 19:Issue 2(2013)
• Page Start: 782
• Page End: 792
• Publication Date: 2012-11-21
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201202555
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>We report a very efficient homogeneous system for the visible‐light‐driven hydrogen production in pure aqueous solution at room temperature. This comprises [Rh<sup>III</sup>(dmbpy)<sub>2</sub>Cl<sub>2</sub>]Cl (<bold>1</bold>) as catalyst, [Ru(bpy)<sub>3</sub>]Cl<sub>2</sub> (<bold>PS1</bold>) as photosensitizer, and ascorbate as sacrificial electron donor. Comparative studies in aqueous solutions also performed with other known rhodium catalysts, or with an iridium photosensitizer, show that 1) the <bold>PS1</bold>/<bold>1</bold>/ascorbate/ascorbic acid system is by far the most active rhodium‐based homogeneous photocatalytic system for hydrogen production in a purely aqueous medium when compared to the previously reported rhodium catalysts, Na<sub>3</sub>[Rh<sup>I</sup>(dpm)<sub>3</sub>Cl] and [Rh<sup>III</sup>(bpy)Cp*(H<sub>2</sub>O)]SO<sub>4</sub> and 2) the system is less efficient when [Ir<sup>III</sup>(ppy)<sub>2</sub>(bpy)]Cl (<bold>PS2</bold>) is used as photosensitizer. Because catalyst <bold>1</bold> is the most efficient rhodium‐based H<sub>2</sub>‐evolving catalyst in water, the performance limits of this complex were further investigated by varying the <bold>PS1</bold>/<bold>1</bold> ratio at pH 4.0. Under optimal conditions, the system gives up to 1010 turnovers versus the catalyst with an initial turnover frequency as high as 857 TON h<sup>−1</sup>. Nanosecond transient absorption spectroscopy measurements show that the initial step of the photocatalytic H<sub>2</sub>‐evolution mechanism is a reductive quenching of the <bold>PS1</bold> excited state by ascorbate, leading to the reduced form of <bold>PS1</bold>, which is then able to reduce [Rh<sup>III</sup>(dmbpy)<sub>2</sub>Cl<sub>2</sub>]<sup>+</sup> to [Rh<sup>I</sup>(dmbpy)<sub>2</sub>]<sup>+</sup>. This reduced species can react with protons to yield the hydride [Rh<sup>III</sup>(H)(dmbpy)<sub>2</sub>(H<sub>2</sub>O)]<sup>2+</sup>, which is the key intermediate for the H<sub>2</sub> production.</p> </abstract>