Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acscatal.1c02475

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/D1CC00903F

Language：English   Publishing type：Research paper (scientific journal)  

© The Royal Society of Chemistry 2021. The catalytic performance of a photochemical H2evolution system made up of EDTA (ethylenediaminetetraacetic acid disodium salt), [Ru(bpy)3]2+(bpy = 2,2′-bipyridine) and a macrocyclicN-heterocyclic carbene cobalt (Co-NHC-1) catalyst has been examined at pH 5.0 (E(2H+/H2) = −0.54 Vvs.SCE) by using six electron relays (ERs) having different first reduction potentials (Ered) in the range −0.69 <Ered< −1.08 V. Compared to the photosystem using the conventional methylviologen (i.e.,N,N′-dimethyl-4,4′-bipyridinium;MV2+), the overall catalytic performance is dramatically improved by employing the ERs having the reduction potentials by 0.08-0.24 V more negative than that ofMV2+(Ered= −0.69 V), revealing that the overall rate is limited by the electron transfer (ET) from the one-electron reduced ER toCo-NHC-1, correlated to hydrogen evolution reaction (HER), rather than that from [Ru*(bpy)3]2+(triplet excited state) to ER, since the driving force for the HER (DFHER) predominates that for the ET from [Ru*(bpy)3]2+to ER (DFET). The optimum condition was realized by selecting one of the viologen derivatives with a medium reduction potential (N,N′,2,2′,6,6′-hexamethyl-4,4′-bipyridinium;tmMV2+;Ered= −0.85 V), leading to afford the initial rate of HER (55-57 μmol h−1) 70 times higher than that obtained by usingMV2+(0.79 μmol h−1). The stability of each one-electron reduced ER under the photolysis conditions has been also examined spectrophotometrically, clarifying that some ERs rather decompose rapidly upon reduction and cannot effectively participate in HER. This study successfully demonstrates for the first time that the overall catalytic performance of the present photosystem cannot be only controlled by the tuning of DFETand DFHERbut also be affected by the stability of the one-electron reduced form of ER.

DOI： 10.1039/d0se01597k

Language：English   Publishing type：Research paper (scientific journal)  

A nickel pyrazinedithiolate ([Ni(dcpdt)2]2−; dcpdt=5,6-dicyanopyrazine-2,3-dithiolate), bearing a NiS4 core similar to the active center of [NiFe] hydrogenase, is shown to serve as an efficient molecular catalyst for the hydrogen evolution reaction (HER). This catalyst shows effectively low overpotentials for HER (330–400 mV at pH 4–6). Moreover, the turnover number of catalysis reaches 20000 over the 24 h electrolysis with a high Faradaic efficiency, 92–100 %. The electrochemical and DFT studies reveal that diprotonated one-electron-reduced species forms at pH < 6.4 via ligand-based proton-coupled electron-transfer (PCET) pathways, leading to electrocatalytic HER without applying the highly negative potential required to generate low-valent nickel intermediates. This is the first example of catalysts exhibiting such behavior.

DOI： 10.1002/anie.201700927

Language：Others  

DOI： 10.26434/chemrxiv-2024-vlcxx

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acs.orglett.3c04013

Language：Others   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/jacsau.3c00218

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.ica.2020.120117

Language：English   Publishing type：Research paper (scientific journal)  

In the quest for efficient metal catalysts for hydrogen production, a new dinuclear nickel complex of formula [{(μ-2-thiazolethiolate)Ni(1,3-bis(diphenylphosphino)propane)}₂](BF₄)₂ (2) has been synthesized. Complex 2 shows electrochemical catalytic behavior for hydrogen production with a overpotential of 0.26 V, a current efficiency of 59%, and a turnover number of 6.4. The lack of catalytic behavior of a related mononuclear complex under the same conditions suggests that the cooperation between the two Ni centers plays a pivotal role in the catalytic behavior.

DOI： 10.1016/j.ica.2020.119498

Language：English   Publishing type：Research paper (scientific journal)  

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 activity among those reported for aqueous systems: TON_CO = 2680 and TOF_CO ^max = 1600-2600 h^-1 with Sel_CO2 = 77-90% (selectivity for CO vs H₂). The observed photocatalytic enhancement is discussed in terms of the 6-electron chargeable character of CoTMPyP, permitting its rapid release of CO via reduction of Co^II to Co^I by intramolecular electron transfer from the reducing equivalent stored at one of the acceptors.

DOI： 10.1021/acscatal.9b04023

Language：English   Publishing type：Research paper (scientific journal)  

There is a demand to develop molecular catalysts promoting hydrogen evolution reaction (HER) with a high catalytic rate together with high tolerance to various inhibitors, such as CO and O2. Here we report a cobalt catalyst possessing a penta‐dentate macrocyclic ligand (1‐Co), which exhibits a fast catalytic rate (TOF = 2210 s‐1) in aqueous pH 7.0 phosphate buffer solution, where proton transfer from dihydrogen phosphate anion (H2PO4‐) plays a key role in catalytic enhancement. It turns out an outstanding electrocatalyst exhibiting high tolerance to inhibitors, displaying over 90% retention in its activity under either CO or air atmosphere. Its high tolerance to CO is concluded to arise from the kinetically labile character of undesirable CO‐bound species due to the geometrical frustration posed by the ligand, prohibiting an ideal trigonal bipyramid to be established.

Language：English   Publishing type：Research paper (scientific journal)  

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. Efficiencies up to 4000 TONCO and 2400 h–1 TOFCO (TOFCO = turnover frequency for CO) are reached at low catalyst loadings, albeit with loss in selectivity. This work successfully demonstrates the ability of CoTPPS to perform highly efficient photoreduction of CO2 in water while retaining its high selectivity for CO formation.

Language：English   Publishing type：Research paper (scientific journal)  

Proton abstraction leading to the formation of a hydride species required to evolve H
₂
largely relies on the basicity of d orbital of the metal responsible for this action. Here we report that a square-planar Ni
^II
(bpy)(dcbdt) hydrogen evolution catalyst shows substantial acceleration in the proton abstraction rate due to the increased basicity at the filled Ni d
_z
2 orbital after formation of [Ni
^I
(bpy
^−.
)(dcbdt)]
²⁻
via consecutive two one-electron reductions (bpy=2,2′-bipyridine; dcbdt=4,5-dicyanobenzene-1,2-dithiolate). The catalyst is likely to adopt the EECC′ mechanism in which the rate of the first protonation step is by far higher than that of the second step, even though an alternative path requiring another reduction (i. e., ECEC′) remains unexcluded. Our DFT calculations reveal that the first and second reductions are correlated with the electron injection into the metal-ligand anti-bonding and π*(bpy) orbitals, respectively, where the latter orbital shows non-negligible hybridization with the nickel d orbital. In addition, a homoleptic catalyst [Ni
^II
(dcbdt)
₂
]
²⁻
is shown to adopt the EC′EC mechanism with the rate-determing step being a hydride forming step, consistent with the largely delocalized nature of the injected electron over the two dcbdt ligands (π*(dcbdt) orbital). This work demonstrates the importance of raising the basicity of the metal d orbital, relevant to promote the proton-coupled electron transfer (PCET).

DOI： 10.1002/celc.201900400

Language：English   Publishing type：Research paper (scientific journal)  

Our DFT results demonstrate that hydrogen evolution from water catalyzed by a nickel pyradinedithiolate (dcpdt) molecular hydrogen evolution catalyst [Ni
^II
(dcpdt)
₂
]
²⁻
proceeds via the formation of a square-planar nickel(ii) hydride intermediate which is given by unprecedented structural transformation of a doubly reduced triply protonated species [Ni
^II
(dcpdtH
₂
)(dcpdtH)]
⁻
, afforded as a result of two consecutive ligand-based reductions of [Ni
^II
(dcpdt)(dcpdtH)]
⁻
through proton-coupled electron transfer (PCET) pathways.

DOI： 10.1039/c8dt04497j

Language：English   Publishing type：Research paper (scientific journal)  

Herein we report an earth-abundant photocatalytic system for CO₂ reduction to CO based on an iron catalyst combined with a Cu^I photosensitizer. Under visible light irradiation CO is produced as the main product (TON_CO = 565, TOFmaxCO = 114 h^-1) with a high selectivity over H₂ production (Sel_CO2 = 84%).

DOI： 10.1039/c9cc04191e

Language：English   Publishing type：Research paper (scientific journal)  

Two new nickel dithiolate derivatives have been examined for their electrocatalytic activity for the hydrogen evolution reaction (HER) in attempts to clarify whether the overpotential for the HER can be tuned upon varying the ligand-centered reduction potential that triggers the HER by the catalysts. We demonstrate the validity of this approach to achieve desirable tunability in the overpotential for the HER.

DOI： 10.1039/C8CC07467D

Language：English   Publishing type：Research paper (scientific journal)  

For the complete structure elucidation of an endogenous sperm-activating and -attracting factor isolated from eggs of the ascidian Ascidia sydneiensis (Assydn-SAAF), its two possible diastereomers with respect to C-25 were synthesized. Starting from ergosterol, the characteristic steroid backbone was constructed by using an intramolecular pinacol coupling reaction and stereoselective reduction of a hydroxy ketone as key steps, and the side chain was introduced by Julia-Kocienski olefination. Comparison of the NMR data of the two diastereomers with those of the natural product led to the elucidation of the absolute configuration as 25S; thus the complete structure was determined and the first synthesis of Assydn-SAAF was achieved.

DOI： 10.1021/acs.jnatprod.7b01052

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

A PtCl₂(bpy) derivative tethered to two viologen (MV²⁺) moieties drives photochemical H₂ evolution via forming a three-electron-reduced species possessing a bpy^--based (or MV⁰-based) reducing equivalent. Such species can only form after one electron reduction of both the MV²⁺ sites because of rapid intramolecular electron transfer from bpy^- to MV²⁺.

DOI： 10.1039/c5cc03558a

Language：English   Publishing type：Research paper (scientific journal)  

The first negatively charged PtCl(tpy) (tpy = 2,2′:6′,2′′-terpyridine) derivative, formulated as Na₂[PtCl(tctpy)]·5H₂O (tctpy = 2,2′:6′,2′′-terpyridine-4,4′,4′′-tricarboxylate), was prepared, characterized, and investigated in detail for its activity as a single-component photocatalyst that drives water reduction to H₂ in the presence of a sacrificial electron donor (EDTA). This compound was confirmed to exist in its fully deprotonated form [PtCl(tctpy)]^2- in aqueous media at pH > 4.4. Despite its dianionic character, [PtCl(tctpy)]^2- was found to form a specific adduct with anionic EDTA (i.e., YH₂ ^2- and YH^3-, where YH₄ is a fully protonated form of EDTA), enabling reductive quenching of the triplet metal-to-ligand charge transfer excited state within the adduct, leading to subsequent electron transfer steps correlated with Pt(ii)-catalyzed H₂ evolution from water. Electrochemical studies also reveal that the compound exhibits a unique pH-dependent first reduction (i.e., tctpy-centered reduction), leading to our realization of the first example of a Pt(ii)-based molecular system that photocatalyzes the H₂ evolution reaction accompanied by a ligand-based proton-coupled electron transfer (PCET) process.

DOI： 10.1039/c5dt00425j

Language：English   Publishing type：Research paper (scientific journal)  

A macrocyclic N-heterocyclic carbene (NHC)-cobalt complex was found to act as an improved H₂-evolving catalyst in a [Ru(bpy)₃] ²⁺-sensitized photosystem using methylviologen as a redox acceptor (MV²⁺ + e^- → MV^+•, MV²⁺ = N,N'-dimethyl-4,4′-bipyridinium), which provides a driving force of only 150 meV for H₂ evolution at pH 5.0.

DOI： 10.1039/c4cc03493g

Language：English  

Language：English   Publishing type：Research paper (scientific journal)  

The Ru^VO species and other intermediates in O₂ evolution from water catalyzed by [Ru(terpy)(bpy)(OH₂)]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.

DOI： 10.1039/c1cc15109f

Language：English   Publishing type：Research paper (scientific journal)  

To answer the question of whether Pt(ii)-based H₂-evolving catalysts are stable upon exposure to H₂, the behaviours of some platinum(ii) complexes in the presence of H₂ (5 × 10 ^-4 - 1 atm) have been followed spectrophotometrically. The results reveal that some catalysts are highly stable upon exposure to H₂.

DOI： 10.1039/c1dt11217a

Language：English   Publishing type：Research paper (scientific journal)  

A series of dinuclear Rh(ii) complexes, [Rh₂(μ-OAc) ₄(H₂O)₂] (HOAc = acetic acid) (1), [Rh ₂(μ-gly)₄(H₂O)₂] (Hgly = glycolic acid) (2), [Rh₂(μ-CF₃CO₂) ₄(acetone)₂] (3), and [Rh₂(bpy) ₂(μ-OAc)₂(OAc)₂] (4), were found to serve as H₂-evolving catalysts in a three-component system consisting of tris(2,2′-bipyridine)ruthenium(ii) (Ru(bpy)₃²⁺), methylviologen (MV²⁺), and ethylenediaminetetraacetic acid disodium salt (EDTA). It was also confirmed that thermal reduction of water into H ₂ by MV⁺, in situ generated by the bulk electrolysis of MV²⁺, is effectively promoted by 1 as a H₂-evolving catalyst. The absorption spectra of the photolysis solution during the photocatalysis were monitored up to 6 h to reveal that the formation of photochemical or thermal byproducts of MV⁺ is dramatically retarded in the presence of the Rh(ii)₂ catalysts, for the H₂ formation rather than the decomposition of MV⁺ becomes predominant in the presence of the Rh(ii)₂ catalysts. The stability of the Rh(ii)₂ dimers was confirmed by absorption spectroscopy, ¹H NMR, and ESI-TOF mass spectroscopy. The results indicated that neither elimination nor replacement of the equatorial ligands take place during the photolysis, revealing that one of the axial sites of the Rh₂ core is responsible for the hydrogenic activation. The quenching of Ru*(bpy)₃²⁺ by 1 was also investigated by luminescence spectroscopy. The rate of H₂ evolution was found to decrease upon increasing the concentration of 1, indicating that the quenching of Ru*(bpy)₃²⁺ by the Rh(ii)₂ species rather than by MV²⁺ becomes predominant at the higher concentrations of 1. The DFT calculations were carried out for several possible reaction paths proposed (e.g., [Rh^II₂(μ-OAc)₄(H ₂O)] + H⁺ and [Rh^II₂(μ-OAc) ₄(H₂O)] + H⁺ + e^-). It is suggested that the initial step is a proton-coupled electron transfer (PCET) to the Rh(ii)₂ dimer leading to the formation of a Rh(ii)Rh(iii)-H intermediate. The H₂ evolution step is suggested to proceed either via the transfer of another set of H⁺ and e^- to the Rh(ii)Rh(iii)-H intermediate or via the homolytic radical coupling through the interaction of two Rh(ii)Rh(iii)-H intermediates.

DOI： 10.1039/c0dt00741b

Language：English   Publishing type：Research paper (scientific journal)  

(Figure Presented) The one-electron-reduced form of methylviologen (MV ^+.), generated in situ by bulk electrolysis of methylviologen (MV²⁺), was for the first time reacted with various Pt(II) complexes in aqueous media without light irradiation to reveal that thermal reduction of water into molecular hydrogen is indeed highly promoted by the Pt(II)-based molecular catalysts.

DOI： 10.1021/ja902245e

Type：Competition, symposium, etc. 

Type：Competition, symposium, etc. 

Type：Competition, symposium, etc. 

Type：Competition, symposium, etc. 

Type：Competition, symposium, etc. 

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