A Dinuclear Ruthenium-Based Water Oxidation Catalyst: Use of Non-Innocent Ligand Frameworks for Promoting Multi-Electron Reactions

Electrochemical water oxidation by a copper complex with an N4-donor ligand under neutral conditions

A mononuclear copper(ii) complex [Cu(H2L)](NO3)2 with an N4-donor redox-active ligand is found to be an efficient homogeneous catalyst for electrochemical water oxidation with the assistance of ligand oxidation.

Mononuclear Ruthenium-Based Water Oxidation Catalyst Supported by Anionic, Redox-Non-Innocent Ligand: Heterometallic O-O Bond Formation via Radical Coupling Pathway

Cerium(IV)-driven water oxidation catalysis mediated by a mononuclear ruthenium(III) complex, [Ru(L)(pic)₃] (H₃L = 2,2'-iminodibenzoic acid, pic = 4-methylpyridine), has been demonstrated in this work. The mechanistic details of water oxidation have been investigated by the combined use of spectroscopy, electrochemistry, kinetic analysis, and computational studies. It was found that water oxidation proceeds via formal high-valent Ru^VII species. The capability of accessing such a high-valent state is derived from the non-innocent behavior of the anionic tridentate ligand frame which helps in accumulation of oxidative equivalents in cooperation with metal center. This metal-ligand cooperation facilitates the multi-electron-transfer reaction such as water oxidation. Kinetic analysis suggests water oxidation at a single site of Ru where O-O bond formation occurs via radical-radical coupling pathway between the oxygen atom of ruthenium-oxo species and the oxygen atom of the hydroxocerium(IV) ion.

Computational Design of Functionalized Metal-Organic Framework Nodes for Catalysis

Recent progress in the synthesis and characterization of metal-organic frameworks (MOFs) has opened the door to an increasing number of possible catalytic applications. The great versatility of MOFs creates a large chemical space, whose thorough experimental examination becomes practically impossible. Therefore, computational modeling is a key tool to support, rationalize, and guide experimental efforts. In this outlook we survey the main methodologies employed to model MOFs for catalysis, and we review selected recent studies on the functionalization of their nodes. We pay special attention to catalytic applications involving natural gas conversion.

Quantum Chemical Modeling of Homogeneous Water Oxidation Catalysis

The design of efficient and robust water oxidation catalysts has proven challenging in the development of artificial photosynthetic systems for solar energy harnessing and storage. Tremendous progress has been made in the development of homogeneous transition-metal complexes capable of mediating water oxidation. To improve the efficiency of the catalyst and to design new catalysts, a detailed mechanistic understanding is necessary. Quantum chemical modeling calculations have been successfully used to complement the experimental techniques to suggest a catalytic mechanism and identify all stationary points, including transition states for both O-O bond formation and O₂ release. In this review, recent progress in the applications of quantum chemical methods for the modeling of homogeneous water oxidation catalysis, covering various transition metals, including manganese, iron, cobalt, nickel, copper, ruthenium, and iridium, is discussed.

Water oxidation mediated by ruthenium oxide nanoparticles supported on siliceous mesocellular foam

An efficient catalyst for chemical and photochemical water oxidation was developed by immobilization of RuO₂ nanoparticles on pyridine-functionalized mesoporous silica.

Chemical and Photochemical Water Oxidation Mediated by an Efficient Single-Site Ruthenium Catalyst

Water oxidation is a fundamental step in artificial photosynthesis for solar fuels production. In this study, we report a single-site Ru-based water oxidation catalyst, housing a dicarboxylate-benzimidazole ligand, that mediates both chemical and light-driven oxidation of water efficiently under neutral conditions. The importance of the incorporation of the negatively charged ligand framework is manifested in the low redox potentials of the developed complex, which allows water oxidation to be driven by the mild one-electron oxidant [Ru(bpy)3 ]3+ (bpy=2,2'-bipyridine). Furthermore, combined experimental and DFT studies provide insight into the mechanistic details of the catalytic cycle.

Theoretical study on photooxidation mechanism of ruthenium complex [Ru(II)-(bpy)2 (TMBiimH2 )](2+) with molecular oxygen

Photoinduced reactions of ruthenium complexes with molecular oxygen have attracted a lot of experimental attention; however, the reaction mechanism remains elusive. In this work, we have used the density functional theory method to scrutinize the visible-light induced photooxidation mechanism of the ruthenium complex [Ru(II)-(bpy)2 (TMBiimH2 )](2+) (bpy: 2, 2-bipyridine and TMBiimH2 : 4, 5, 4, 5-tetramethyl-2, 2-biimidazole) initiated by the attack of molecular oxygen. The present computational results not only explain very well recent experiments, also provide new mechanistic insights. We found that: (1) the triplet energy transfer process between the triplet molecular oxygen and the metal-ligand charge transfer triplet state of the ruthenium complex, which leads to singlet molecular oxygen, is thermodynamically favorable; (2) the singlet oxygen addition process to the S0 ruthenium complex is facile in energy; (3) the chemical transformation from endoperoxide to epidioxetane intermediates can be either two- or one-step reaction (the latter is energetically favored). These findings contribute important mechanistic information to photooxidation reactions of ruthenium complexes with molecular oxygen. © 2016 Wiley Periodicals, Inc.

Water oxidation catalysis with ligand substituted Ru–bpp type complexes

The influence of electronic effects over Ru–bpp water oxidation catalysts.

A ruthenium water oxidation catalyst based on a carboxamide ligand

Herein is presented a single-site Ru complex bearing a carboxamide-based ligand that efficiently manages to carry out the four-electron oxidation of H₂O.

On the mechanism of water oxidation catalyzed by a dinuclear ruthenium complex: a quantum chemical study

The development of efficient and robust catalysts for water oxidation is an essential element in solar water splitting. In the present paper, the reaction mechanism for a dinuclear Ru water oxidation catalyst has been investigated in detail through quantum chemical calculations.

Incorporation of a ruthenium–bis(pyridine)pyrazolate (Ru–bpp) water oxidation catalyst in a hexametallic macrocycle

New terpyridine-functionalised analogues of the in,in-[{Ru^II(trpy)}₂(μ-bpp)(H₂O)₂]³⁺ water oxidation catalyst (bpp = bis-(2-pyridyl)pyrazolate) have been synthesised and used to create a hexametallic {Fe₂Ru₄} macrocycle.

Water oxidation using earth-abundant transition metal catalysts: opportunities and challenges

Catalysts for the oxidation of water are a vital component of solar energy to fuel conversion technologies. This Perspective summarizes recent advances in the field of designing homogeneous water oxidation catalysts (WOCs) based on Mn, Fe, Co and Cu.