Electrochemical Ferrier Rearrangement of Glycals.

The Ferrier rearrangement (FR) is a well-documented reaction that relies on strong acids or oxidants to convert glycals into unsaturated glycosyl derivatives. In this work, we introduce an electrochemical variant of the FR, offering a broad substrate compatibility. Various nucleophiles and glycal derivatives afford 2,3-unsaturated glycosyl derivatives in high yields with excellent diastereoselectivities.

Electrochemical Asymmetric Radical Functionalization of Aldehydes Enabled by a Redox Shuttle.

Aminocatalysis is a well-established tool that enables the production of enantioenriched compounds under mild conditions. Its versatility is underscored by its seamless integration with various synthetic approaches. While the combination of aminocatalysis with metal catalysis, photochemistry, and stoichiometric oxidants has been extensively explored, its synergy with electrochemical activation remains largely unexplored.

A breath of sunshine: oxygenic photosynthesis by functional molecular architectures.

The conversion of light into chemical energy is the game-changer enabling technology for the energetic transition to renewable and clean solar fuels. The photochemistry of interest includes the overall reductive/oxidative splitting of water into hydrogen and oxygen and alternatives based on the reductive conversion of carbon dioxide or nitrogen, as primary sources of energy-rich products. Devices capable of performing such transformations are based on the integration of three sequential core functions: light absorption, photo-induced charge separation, and the photo-activated breaking/making of molecular bonds specific catalytic routes.

Unveiling the impact of the light-source and steric factors on [2+2] heterocycloaddition reactions.

Information gained from in-depth mechanistic investigations can be used to control the selectivity of reactions, leading to the expansion of the generality of synthetic processes and the discovery of new reactivity. Here, we investigate the mechanism of light-driven [2+2] heterocycloadditions (Paternò-Büchi reactions) between indoles and ketones to develop insight into these processes. Using ground-state UV-Vis absorption and transient absorption spectroscopy (TAS), together with DFT calculations, we found that the reactions can proceed via an exciplex or electron-donor-acceptor (EDA) complex, which are key intermediates in determining the stereoselectivity of the reactions.

A Proton-Coupled Electron Transfer Strategy to the Redox-Neutral Photocatalytic CO Fixation.

Herein, we report our study on the design and development of a novel photocarboxylation method. We have used an organic photoredox catalyst (PC, 4CzIPN) and differently substituted dihydropyridines (DHPs) in combination with an organic base (1,5,7-triazabicyclodec-5-ene, TBD) to access a proton-coupled electron transfer (PCET) based manifold. In depth mechanistic investigations merging experimental analysis (NMR, IR, cyclic voltammetry) and density-functional theory (DFT) calculations reveal the key activity of a H-bonding complex between the DHP and the base.

The Rational Design of Reducing Organophotoredox Catalysts Unlocks Proton-Coupled Electron-Transfer and Atom Transfer Radical Polymerization Mechanisms.

Photocatalysis has become a prominent tool in the arsenal of organic chemists to develop and (re)imagine transformations. However, only a handful of versatile organic photocatalysts (PCs) are available, hampering the discovery of new reactivities. Here, we report the design and complete physicochemical characterization of 9-aryl dihydroacridines (9ADA) and 12-aryl dihydrobenzoacridines (12ADBA) as strong reducing organic PCs.

Photoelectrochemical C-H Activation Through a Quinacridone Dye Enabling Proton-Coupled Electron Transfer.

Dye-sensitized photoanodes for C-H activation in organic substrates are assembled by vacuum sublimation of a commercially available quinacridone (QNC) dye in the form of nanosized rods onto fluorine-doped tin oxide (FTO), TiO , and SnO slides. The photoanodes display extended absorption in the visible range (450-600 nm) and ultrafast photoinduced electron injection (<1 ps, as revealed by transient absorption spectroscopy) of the QNC dye into the semiconductor. The proton-coupled electron-transfer reactivity of QNC is exploited for generating a nitrogen-based radical as its oxidized form, which is competent in C-H bond activation.

Enhancing Oxygenic Photosynthesis by Cross-Linked Perylenebisimide "Quantasomes".

As the natural-born photoelectrolyzer for oxygen delivery, photosystem II (PSII) is hardly replicated with man-made constructs. However, building on the "quantasome" hypothesis ( 1964, 144, 1009-1011), PSII mimicry can be pared down to essentials by shaping a photocatalytic ensemble (from the Greek term "soma" = body) where visible-light quanta trigger water oxidation. PSII-inspired quantasomes (QS) readily self-assemble into hierarchical photosynthetic nanostacks, made of bis-cationic perylenebisimides (PBI) as chromophores and deca-anionic tetraruthenate polyoxometalates (RuPOM) as water oxidation catalysts ( 2019, 11, 146-153).

Beyond Water Oxidation: Hybrid, Molecular-Based Photoanodes for the Production of Value-Added Organics.

The political and environmental problems related to the massive use of fossil fuels prompted researchers to develop alternative strategies to obtain green and renewable fuels such as hydrogen. The light-driven water splitting process (i.e.

Basicity as a Thermodynamic Descriptor of Carbanions Reactivity with Carbon Dioxide: Application to the Carboxylation of α,β-Unsaturated Ketones.

The utilization of carbon dioxide as a raw material represents nowadays an appealing strategy in the renewable energy, organic synthesis, and green chemistry fields. Besides reduction strategies, carbon dioxide can be exploited as a single-carbon-atom building block through its fixation into organic scaffolds with the formation of new C-C bonds (carboxylation processes). In this case, activation of the organic substrate is commonly required, upon formation of a carbanion C, being sufficiently reactive toward the addition of CO.

Transparent Polymeric Formulations Effective against SARS-CoV-2 Infection.

The main route of the transmission of the SARS-CoV-2 virus is through airborne small aerosol particles containing viable virus as well as through droplets transmitted between people within close proximity. Transmission via contaminated surfaces has also been recognized as an important route for the spread of SARS-CoV-2 coronavirus. Among a variety of antimicrobial agents currently in use, polymers represent a class of biocides that have become increasingly important as an alternative to existing biocidal approaches.

Artificial photosynthesis: photoanodes based on polyquinoid dyes onto mesoporous tin oxide surface.

Dye-sensitized photoelectrochemical cells represent an appealing solution for artificial photosynthesis, aimed at the conversion of solar light into fuels or commodity chemicals. Extensive efforts have been directed towards the development of photoelectrodes combining semiconductor materials and organic dyes; the use of molecular components allows to tune the absorption and redox properties of the material. Recently, we have reported the use of a class of pentacyclic quinoid organic dyes (KuQuinone) chemisorbed onto semiconducting tin oxide as photoanodes for water oxidation.

Water-Assisted Concerted Proton-Electron Transfer at Co(II)-Aquo Sites in Polyoxotungstates With Photogenerated Ru (bpy) Oxidant.

The cobalt substituted polyoxotungstate [Co (H O) (α-B-PW O ) (PW O )] (Co6) displays fast electron transfer (ET) kinetics to photogenerated Ru (bpy) , 4 to 5 orders of magnitude faster than the corresponding ET observed for cobalt oxide nanoparticles. Mechanistic evidence has been acquired indicating that: (i) the one-electron oxidation of Co6 involves Co(II) aquo or Co(II) hydroxo groups (abbreviated as Co6(II)-OH and Co6(II)-OH, respectively, whose speciation in aqueous solution is associated to a pK of 7.6), and generates a Co(III)-OH moiety (Co6(III)-OH), as proven by transient absorption spectroscopy; (ii) at pH>pK , the Co6(II)-OH→Ru (bpy) ET occurs via bimolecular kinetics, with a rate constant k close to the diffusion limit and dependent on the ionic strength of the medium, consistent with reaction between charged species; (iii) at pH View Article and Find Full Text PDF

Carbon Dioxide Reduction Mediated by Iron Catalysts: Mechanism and Intermediates That Guide Selectivity.

The reduction of carbon dioxide represents an ambitious target, with potential impact on several of the United Nations' sustainable development goals including climate action, renewable energy, sustainable cities, and communities. This process shares a common issue with other redox reactions involved in energy-related schemes (i.e.

Electrochemical Conversion of CO to CO by a Competent Fe Intermediate Bearing a Schiff Base Ligand.

Iron complexes with a N O -type N,N'-bis(salicylaldehyde)-1,2-phenylenediamine salophen ligand catalyze the electrochemical reduction of CO to CO in acetonitrile with phenol as the proton donor, giving rise to 90-99 % selectivity, faradaic efficiency up to 58 %, and turnover frequency up to 10  s at an overpotential of 0.65 V. This novel class of molecular catalyst for CO reduction operate through a mononuclear Fe intermediate, with phenol being involved in the process with first-order kinetics.

Novel iridium complexes with N-heterocyclic dicarbene ligands in light-driven water oxidation catalysis: photon management, ligand effect and catalyst evolution.

Iridium complexes [IrClCp*diNHC]PF6, with N-heterocyclic dicarbene (diNHC) and pentamethylcyclopentadienyl (Cp*) ligands, have been investigated in light driven water oxidation catalysis within the Ru(bpy)32+/S2O82- cycle (bpy = 2,2'-bipyridine). In particular, the effect of different diNHC ligands was evaluated by employing the complex 1a (diNHC = 1,1'-dimethyl-3,3'-ethylenediimidazol-2,2'-diylidene) and the novel and structurally characterised 2 (diNHC = 1,1'-dimethyl-3,3'-ethylene-5,5'-dibromodiimidazol-2,2'-diylidene) and 3 (diNHC = 1,1'-dimethyl-3,3'-ethylene-dibenzimidazol-2,2'-diylidene). The presented results include: (i) a photon management analysis of the 1a/Ru(bpy)32+/S2O82- system, revealing two regimes of O2 evolution rate, being dependent on the light intensity at low photon flux, where the system reaches an overall quantum yield up to 0.

Photoanodes for water oxidation with visible light based on a pentacyclic quinoid organic dye enabling proton-coupled electron transfer.

A pentacyclic quinoid dye, KuQ(O)3OH, combining (i) extended visible absorption up to 600 nm, (ii) excited state reduction potential >2 V vs. NHE, and (iii) a photoinduced proton-coupled electron transfer mechanism, has been used for the fabrication of dye-sensitized SnO2 photoanodes integrating a ruthenium polyoxometalate water oxidation catalyst. The resulting photoelectrode SnO2|KuQ(O)3OH|Ru4POM displays a light harvesting efficiency up to 90% in the range 500-600 nm, an onset potential as low as 0.

Light-Driven Water Oxidation with the Catalyst and the Ru(bpy)/SO Cycle: Photogeneration of Active Dimers, Electron-Transfer Kinetics, and Light Synchronization for Oxygen Evolution with High Quantum Efficiency.

Light-driven water oxidation is achieved with the Ru(bpy)/SO cycle employing the highly active water oxidation catalyst, namely, an Ir(pyalc) μ-oxo-dimer [pyalc = 2-(2'-pyridyl)-2-propanoate]. is readily formed by stepwise oxidation of the monomeric Ir(III) precursor by the photogenerated Ru(bpy), with a quantum yield ϕ of up to 0.10.

Naphthochromenones: Organic Bimodal Photocatalysts Engaging in Both Oxidative and Reductive Quenching Processes.

Twelve naphthochromenone photocatalysts (PCs) were synthesized on gram scale. They absorb across the UV/Vis range and feature an extremely wide redox window (up to 3.22 eV) that is accessible using simple visible light irradiation sources (CFL or LED).

Clean rhodium nanoparticles prepared by laser ablation in liquid for high performance electrocatalysis of the hydrogen evolution reaction.

Rhodium nanoparticles (NPs) were prepared by a one-step, green and facile procedure consisting in laser ablation of a bulk Rh target immersed in pure water (W-Rh-NPs) or ethanol (E-Rh-NPs). When embedded in mesoporous carbon based inks, both W-Rh-NPs and E-Rh-NPs show excellent activity towards the hydrogen evolution reaction in acidic media, operating close to the thermodynamic potential with 85-97% faradaic yields and low Tafel slopes of 50-54 mV per decade in the low overpotential region ( < 20 mV). A superior activity of W-Rh-NPs with respect to E-Rh-NPs is ascribed to the absence of surface carbon reducible species derived from the synthesis in organic solvent, and thus confirms the importance of the use of water as the preferred medium for laser synthesis of clean nanocrystals in liquid environment.

Fluorinated Zn Porphyrins for Dye-Sensitized Aqueous Photoelectrosynthetic Cells.

Three perfluorinated Zn porphyrins were evaluated as n-type sensitizers in photoelectrosynthetic cells for HBr and water splitting. All the dyes are featured by the presence of pentafluorophenyl electron-withdrawing groups to increase the ground-state oxidation potential and differ for the nature and position of the π-conjugate linker between the core and anchoring group tasked to bind the metal oxide, in order to assess the best way of coupling with the semiconductor. A phenyl-triazole moiety was used to link the carboxylic anchoring group onto the position, while an ethynyl-phenyl linker was chosen to bridge carboxylic and cyanoacrylic groups onto the β-pyrrolic position.

Publisher Correction: Hierarchical organization of perylene bisimides and polyoxometalates for photo-assisted water oxidation.

In the version of this Article originally published, in the graphical abstract the y-axis units of the plot read 'mA cm, but should have read 'μA cm. Additionally, an erroneous gap appeared in the red trace. These errors have now been corrected.

Hierarchical organization of perylene bisimides and polyoxometalates for photo-assisted water oxidation.

The oxygen in Earth's atmosphere is there primarily because of water oxidation performed by photosynthetic organisms using solar light and one specialized protein complex, photosystem II (PSII). High-resolution imaging of the PSII 'core' complex shows the ideal co-localization of multi-chromophore light-harvesting antennas with the functional reaction centre. Man-made systems are still far from replicating the complexity of PSII, as the majority of PSII mimetics have been limited to photocatalytic dyads based on a 1:1 ratio of a light absorber, generally a Ru-polypyridine complex, with a water oxidation catalyst.

Visible Light Driven Photoanodes for Water Oxidation Based on Novel r-GO/β-Cu₂V₂O₇/TiO₂ Nanorods Composites.

This paper describes the preparation and the photoelectrochemical performances of visible light driven photoanodes based on novel r-GO/β-Cu₂V₂O₇/TiO₂ nanorods/composites. β-Cu₂V₂O₇ was deposited on both fluorine doped tin oxide (FTO) and TiO₂ nanorods (NRs)/FTO by a fast and convenient Aerosol Assisted Spray Pyrolysis (AASP) procedure. Ethylenediamine (EN), ammonia and citric acid (CA) were tested as ligands for Cu ions in the aerosol precursors solution.

Hydrogen Evolution by Fe Molecular Electrocatalysts Interconverting between Mono and Di-Nuclear Structures in Aqueous Phase.

A new FeL/Fe L manifold, with HL=2-({[di(2-pyridyl)methyl](methyl)amino}methyl)phenol, was prepared in gram scale (>50 % yield) and characterized in solution and solid state. The monomer/dimer interconversion is controlled in aqueous phase, upon varying the pH conditions. The electrocatalytic hydrogen evolution reaction (HER) occurs through the FeL monomer with added trifluoroacetic acid (TFA) and through the Fe L μ-oxo dimer in acetate buffer (pH 4.