Iridium and Rhodium Complexes within a Macroreticular Acidic Resin: A Heterogeneous Photocatalyst for Visible‐light Driven H₂ Production without an Electron Mediator

Abstract

Direct ion exchange of cyclometalated iridium(III) and tris-2,2'-bipyridyl rhodium(III) complexes, of which the former acts as a photosensitizer and the latter as a proton reduction catalyst, within a macroreticular acidic resin has been accomplished with the aim of developing a photocatalyst for H2 production under visible-light irradiation. Ir L(III)-edge and Rh K-edge X-ray absorption fine structure (XAFS) measurements suggest that the Ir and Rh complexes are easily accommodated in the macroreticular space without considerable structural changes. The photoluminescence emission of the exchanged Ir complex due to a triplet ligand charge-transfer ((3)LC) and metal-to-ligand charge-transfer ((3)MLCT) transition near 550 nm decreases with increasing the amount of the Rh complex, thus suggesting the occurrence of an electron transfer from Ir to Rh. The Ir-Rh/resin catalyst behaves as a heterogeneous photocatalyst capable of both visible-light sensitization and H2 production in an aqueous medium in the absence of an electron mediator. The photocatalytic activitity is strongly dependent on the amount of the components and reaches a maximum at a molar ratio of 2:1 of Ir/Rh complexes. Moreover, leaching and agglomeration of the active metal complexes are not observed, and the recovered photocatalyst can be recycled without loss in catalytic activity.

Poly(ethyleneimine)‐tethered Ir Complex Catalyst Immobilized in Titanate Nanotubes for Hydrogenation of CO2 to Formic Acid

“…The shapes and edge positions correspond well with those of IrCl 3 (Figure A), indicating that Ir atoms coordinated to PN ligand are present as monomeric Ir III species. In general, the white line absorption peaks of oxidized Ir species are stronger than those of reduced species . The intensities of the Ir white line in Ir‐PN‐PEI and Ir‐PN‐PEI@TNT both agree well with that of IrCl 3 , suggesting that the oxidation state of Ir is unchanged upon coordination and even after immobilization in the TNT support.…”

Metal Complexes Supported on Solid Matrices for Visible‐Light‐Driven Molecular Transformations

“…[54] XAFS results suggest that the Ir and Rh complexes are accommodated without structural change of the local metal surroundings. The accommodated Ir complex gave rise to a predominant emission near 550 nm due to 3 LC state receiving considerable contribution from close-lying 3 MLCT levels, [55] which is gradually quenched as the loading of adjacent Rh complex increases (Figure 12).…”

Visible light mediated cyclization of tertiary anilines with maleimides using a supported iridium complex catalyst

“…35 Despite the signicant advantages of supported complex catalyst, the synthesis and use of them in C-H bond activation and C-C and C-heteroatom bond formation are still quite limited. [38][39][40][41][42][43][44][45] Here the novel supported iridium complex catalyst was synthesized by the immobilization of the iridium onto the pyridine modi-ed PDVB (Scheme 1). Iridium was chelated with pyridine, which conrmed the strong interaction between active sites and the support, resulting in high stability.…”