This article summarizes the ongoing studies on the photo-hydrogen-evolving molecular devices (PHEMDs) made up of polypyridyl Ru(II) photosensitizers and Pt(II)-based molecular catalysts, carried out in the authors' group in the last two decades. The H(2)-evolving activities of Pt(II)-based molecular catalysts demonstrated by various experimental evidences are first described. Then the structure-activity relationship, some important factors required for the higher catalytic activity, and several important insights into the mechanism of photochemical H(2) evolution catalyzed by the Ru(II)Pt(II)-based PHEMDs will be discussed in detail.
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Redox tuning in Pt(bpy)-viologen catalyst-acceptor dyads enabling photocatalytic hydrogen evolution from water.
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May 2021
Department of Chemistry, Faculty of Science, Kyushu University, Motooka 744, Nishi-ku, Fukuoka, 819-0395, Japan.
A Pt(ii)-based photo-hydrogen-evolving molecular device tethered to dimethyl-substituted viologens (Pt(bpy)(dmMV)), providing higher driving force for hydrogen evolution reaction (HER) than the non-methylated analogue (Pt(bpy)(MV)), is found to exhibit improved photocatalytic performance. The observed behaviors are explained by the multiple HER pathways taken by evolving H by the doubly and triply reduced species generated via consecutive photo-driven steps. Although the activity is still killed by the Dexter-type energy transfer quenching, our results provide new design strategies towards the development of more finely tuned molecular devices controlling the photocatalytic HER.
View Article and Find Full Text PDFMechanistic studies of photoinduced intramolecular and intermolecular electron transfer processes in RuPt-centred photo-hydrogen-evolving molecular devices.
Phys Chem Chem Phys
January 2014
Department of Chemistry, Faculty of Sciences, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan.
The photoinduced electron transfer properties of two photo-hydrogen-evolving molecular devices (PHEMDs) [(bpy)2Ru(II)(phen-NHCO-bpy-R)Pt(II)Cl2](2+) (i.e., condensation products of [Ru(bpy)2(5-amino-phen)](2+) and (4-carboxy-4′-R-bpy)PtCl2; bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline; RuPt-COOH for R = COOH and RuPt-CN for R = CN) were investigated.
View Article and Find Full Text PDFLight-induced charge separation and photocatalytic hydrogen evolution from water using Ru(II)Pt(II)-based molecular devices: effects of introducing additional donor and/or acceptor sites.
Dalton Trans
April 2011
Department of Chemistry, Faculty of Science, Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka 812-8581, Japan.
In our hopes to improve the photocatalytic efficiency of photo-hydrogen-evolving molecular devices, several new dyads and triads possessing a photosensitizing Ru(bpy)(phen)(2)(2+) (or Ru(phen)(3)(2+)) chromophore (abbreviated as Ru(II)) attached to both/either a phenothiazine moiety (abbreviated as Phz) and/or H(2)-evolving PtCl(2)(bpy) units (abbreviated as Pt), such as Phz-Ru(II)-Pt2 (triad), Ru(II)-Pt2 (dyad), and Ru(II)-Pt3 (dyad), were synthesized and their basic properties together with the photo-hydrogen-evolving characteristics were investigated in detail. The (3)MLCT phosphorescence from the Ru(II) moiety in these systems is substantially quenched due to the highly efficient photoinduced electron transfer (PET). Based on the electrochemical studies, the driving forces for the PET were estimated as -0.
View Article and Find Full Text PDFPhoto-hydrogen-evolving molecular devices driving visible-light-induced water reduction into molecular hydrogen: structure-activity relationship and reaction mechanism.
Chem Commun (Camb)
February 2011
Department of Industrial Chemistry, Faculty of Engineering, Tokyo University of Science, 12-1 Ichigaya Funagawara-machi, Shinjuku-ku, Tokyo 162-0826, Japan.
This article summarizes the ongoing studies on the photo-hydrogen-evolving molecular devices (PHEMDs) made up of polypyridyl Ru(II) photosensitizers and Pt(II)-based molecular catalysts, carried out in the authors' group in the last two decades. The H(2)-evolving activities of Pt(II)-based molecular catalysts demonstrated by various experimental evidences are first described. Then the structure-activity relationship, some important factors required for the higher catalytic activity, and several important insights into the mechanism of photochemical H(2) evolution catalyzed by the Ru(II)Pt(II)-based PHEMDs will be discussed in detail.
View Article and Find Full Text PDFSyntheses, characterization, and photo-hydrogen-evolving properties of tris(2,2'-bipyridine)ruthenium(II) derivatives tethered to an H2-evolving (2-phenylpyridinato)platinum(II) unit.
Molecules
July 2010
Department of Chemistry, Faculty of Science, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan.
With the aim of developing new molecular devices having higher photo-hydrogen-evolving activity, Pt(ppy)ClX units (ppy = 2-phenylpyridinate, X = Cl(-) or DMSO; DMSO = dimethylsulfoxide) have been employed as an H(2)-evolving site, as the catalytic activity of [Pt(ppy)Cl(2)](-) was confirmed to be higher than those of other mononuclear platinum(II) complexes. In the present study, two new heterodinuclear Ru(II)Pt(II) complexes, produced by condensation of [Ru(bpy)(2)(5-amino-phen)](2+) (bpy = 2,2'-bipyridine, phen = 1,10-phenanthroline) with [Pt(cppy)Cl(2)](-) and Pt(cppy)(DMSO)Cl (cppy = 9-carboxy-phenylpyridinate), respectively, have been prepared and their photo-hydrogen-evolving activities have been evaluated in detail. The ineffectiveness of these systems as photo-hydrogen-evolving molecular devices are interpreted in terms of their negative driving forces for the photoinduced electron transfer from the triplet MLCT excited state of the Ru chromophore to the pi*(ppy) orbital of the catalyst moiety.
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