Ken Sakai

Three water-soluble cobalt porphyrins have been investigated as water oxidation catalysts via photo-initiation using Ru(II)(bpy)3(2+)/Na2S2O8. The pH dependence of the turnover frequency revealed maximum activity at pH 11. Based on the second order dependence on catalyst concentration for the rate of water oxidation, we suggest a bimolecular radical coupling process as the rate determining step.

The performance of a water-soluble cobalt porphyrin ([{meso-tetra(4-sulfonatophenyl)porphyrinato}cobalt(III)], CoTPPS) as a catalyst for the photoreduction of CO2 in fully aqueous media has been investigated under visible light irradiation using [Ru(bpy)3]2+ as a photosensitizer and ascorbate as a sacrificial electron donor. CO is selectively produced (>82%) with high efficiency (926 TONCO; TONCO = turnover number for CO). Upon optimization, selectivities of at least 91% are achieved. Efficienci

The Mo-based polyoxometalates containing mono- and dicobalt(III) catalyst cores, [CoMo(6)O(24)H(6)](3-) and [Co(2)Mo(10)O(38)H(4)](6-), were found to serve as O(2)-evolving catalysts in a system consisting of tris(2,2'-bipyridine)ruthenium(II) (Ru(bpy)(3)(2+)) and sodium persulfate (S(2)O) in an aqueous borate buffer solution at pH 8.0. Kinetics of O(2) evolution reveals that the higher cobalt nuclearity is not necessary to attain the highly active nature of the catalyst.

The evolution of H2 by near-infrared light irradiation is an unprecedented phenomenon that makes use of an extended wavelength range of the solar spectrum. In their Communication on page 208 ff., K. Sakai et al. report photocatalytic H2 evolution using a polypyridyl triruthenium photosensitizer with light-harvesting properties. The photosensitizer promotes H2 evolution under light irradiation at 700–800 nm.

Without using precious elements, a highly efficient and selective molecular-based photocatalytic system for CO2-to-CO conversion in fully aqueous media has been developed. Our copper(I)-based water-soluble photosensitizer (CuPS) preserves its highly luminescent and long-lived excited state even in aqueous media. The CuPS-driven CO2 reduction catalyzed by a water-soluble cobalt porphyrin possessing four N-methylpyridinium acceptors at the meso positions (CoTMPyP) achieves the highest catalytic ac

Abstract This minireview provides a brief overview of the progress that has been made in developing homogeneous water oxidation catalysts based on base metals (manganese, iron, cobalt, nickel, and copper) from the 1990s to mid‐2014. The impact of each contribution is analyzed, and opportunities for further improvement are noted. In addition, the relative stabilities of the base‐metal catalysts that have been reported are compared to illustrate the importance of developing more robust catalytic s

The Ru(V)==O species and other intermediates in O(2) evolution from water catalyzed by [Ru(terpy)(bpy)(OH(2))](2+) were spectrophotometrically characterized, and the spectral components observed were identified based on the TD-DFT calculations. Moreover, important insights into the rapid paths after the RDS were given by the DFT studies.

Eight new crystalline α-pyrrolidinonate-bridged homo- and mixed-valence cis-diammineplatinum dimers and tetramers, HT-[Pt(2.0+)2(NH3)4(μ-C4H6NO)2](ClO4)2 (2), HH-[Pt(2.25+)2(NH3)4(μ-C4H6NO)2]2(ClO4)5 (4), HH-[Pt(2.25+)2(NH3)4(μ-C4H6NO)2]2(PF6)3(NO3)2 (5), {HH-[Pt(2.25+)2(NH3)4(μ-C4H6NO)2]2}{HH-[Pt(2.5+)2(NH3)4(μ-C4H6NO)2(NO3)]2}(PF6)2(NO3)7·6H2O (7), HH-[Pt(2.5+)4(NH3)8(μ-C4H6NO)4(Cl)](ClO4)3Cl2 (9), HH-[Pt(3.0+)2(NH3)4(μ-C4H6NO)2(Cl)2](NO3)2 (11), HH-[Pt(3.0+)2(NH3)4(μ-C4H6NO)2(Cl)(NO3)](NO3)2·

Enabling the production of solar fuels on a global scale through artificial photosynthesis requires the development of water oxidation catalysts with significantly improved stability. The stability of photosystems is often reduced owing to attack by singlet oxygen, which is produced during light harvesting. Here, we report photochemical water oxidation by CoFPS, a fluorinated Co-porphyrin designed to resist attack by singlet oxygen. CoFPS exhibits significantly improved stability relative to its

[PtCl(terpy)]Cl x 2 H(2)O (terpy = 2,2':6',2''-terpyridine) (1Cl x 2 H(2)O) is the first example serving as a bifunctional system promoting both photosensitization and hydrogenic activation as an H(2)-evolving catalyst in aqueous media in the presence of a sacrificial electron donor (EDTA) under visible-light illumination. The rate of H(2) formation has turned out to be quadratic to the concentration of 1, suggesting that a bimolecular path determines the overall reaction rate for the photoinduc

To stop global warming and climate changes, substantial efforts have been made to diminish CO2 emission. Photocatalytic and electrocatalytic CO2 reduction into fuels has thus become a highly important topic. Our recent interest has been to develop earth-abundant and environmentally friendly photocatalytic systems consisting of a non-precious-metal molecular CO2 reduction catalyst combined with subcomponents, especially using aqueous conditions without any organic solvents. However, CO2 reduction

Bovine beta-lactoglobulin A assumes a dimeric native conformation at neutral pH, while the conformation at pH 2 is monomeric but still native. Beta-lactoglobulin A has a free thiol at Cys121, which is buried between the beta-barrel and the C-terminal major alpha-helix. This thiol group was specifically reacted with 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) in the presence of 1.0 M Gdn-HCI at pH 7.5, producing a modified beta-lactoglobulin (TNB-bIg) containing a mixed disulfide bond with 5-thio-

Mimicking nature: The photochemical H2 evolution from water catalyzed by a platinum(II)-based metalloviologen (PV2+) proceeds via the photoexcited state of the one-electron-reduced species (PV+.; see picture, EDTA=ethylenediaminetetraacetic acid). This artificial photosynthesis is reminiscent of the “Z-scheme photosynthesis” in green plants.