Structure of a biohybrid photosystem I-platinum nanoparticle solar fuel catalyst.

Biohybrid solar fuel catalysts leverage natural light-driven enzymes to produce valuable fuel products. One useful biological platform for such a system is photosystem I, a pigment-protein complex that captures sunlight and converts it into chemical energy with near unity quantum efficiency, which generates low potential reducing equivalents for metabolism. Realizing and understanding the molecular basis for an approach that utilizes those electrons and stores solar energy as a fuel is therefore appealing.

Modeling Electrochemical Vacancy Regeneration in Single-Walled Carbon Nanotubes.

Synthesis-induced defects in single-walled carbon nanotubes (SWCNTs) enable diverse catalytic reactions, but the nature of catalytic intermediates and how active species regeneration occurs are unclear. Using a quantum mechanics/molecular mechanics (QM/MM) hybrid methodology based on density functional theory (DFT) and a classical force-field, we explore the reactivity and electrochemical regeneration of a vacancy defect in a zigzag SWCNT. Our findings indicate that hydrolysis of the defect forms a ketone group on one carbon atom and C-H bonds on two adjacent carbons.

Breaking a Molecular Scaling Relationship Using an Iron-Iron Fused Porphyrin Electrocatalyst for Oxygen Reduction.

The design of efficient electrocatalysts is limited by scaling relationships governing trade-offs between thermodynamic and kinetic performance metrics. This ″″ of electrocatalysis arises from synthetic design strategies, where structural alterations to a catalyst must balance nucleophilic versus electrophilic character. Efforts to circumvent this fundamental impasse have focused on bioinspired applications of extended coordination spheres and charged sites proximal to a catalytic center.

BODIPY Chemisorbed on SnO and TiO Surfaces for Photoelectrochemical Applications.

Advancement toward dye-sensitized photoelectrochemical cells to produce solar fuels by solar-driven water splitting requires a photosensitizer that is firmly attached to the semiconducting photoelectrodes. Covalent binding enhances the efficiency of electron injection from the photoexcited dye into the metal oxide. Optimization of charge transfer, efficient electron injection, and minimal electron-hole recombination are mandatory for achieving high efficiencies.

Feed-Forward Neural Network for Predicting Enantioselectivity of the Asymmetric Negishi Reaction.

Density functional theory (DFT) is a powerful tool to model transition state (TS) energies to predict selectivity in chemical synthesis. However, a successful multistep synthesis campaign must navigate energetically narrow differences in pathways that create some limits to rapid and unambiguous application of DFT to these problems. While powerful data science techniques may provide a complementary approach to overcome this problem, doing so with the relatively small data sets that are widespread in organic synthesis presents a significant challenge.

Ozone-enabled fatty acid discovery reveals unexpected diversity in the human lipidome.

Fatty acid isomers are responsible for an under-reported lipidome diversity across all kingdoms of life. Isomers of unsaturated fatty acids are often masked in contemporary analysis by incomplete separation and the absence of sufficiently diagnostic methods for structure elucidation. Here, we introduce a comprehensive workflow, to discover unsaturated fatty acids through coupling liquid chromatography and mass spectrometry with gas-phase ozonolysis of double bonds.

Ligand Rigidity Steers the Selectivity and Efficiency of the Photosubstitution Reaction of Strained Ruthenium Polypyridyl Complexes.

While photosubstitution reactions in metal complexes are usually thought of as dissociative processes poorly dependent on the environment, they are, in fact, very sensitive to solvent effects. Therefore, it is crucial to explicitly consider solvent molecules in theoretical models of these reactions. Here, we experimentally and computationally investigated the selectivity of the photosubstitution of diimine chelates in a series of sterically strained ruthenium(II) polypyridyl complexes in water and acetonitrile.

Correction: Automated assessment of redox potentials for dyes in dye-sensitized photoelectrochemical cells.

Correction for 'Automated assessment of redox potentials for dyes in dye-sensitized photoelectrochemical cells' by Jelena Belić , , 2022, , 197-210, https://doi.org/10.1039/D1CP04218A.

Establishing carbon-carbon double bond position and configuration in unsaturated fatty acids by gas-phase infrared spectroscopy.

Fatty acids are an abundant class of lipids that are characterised by wide structural variation including isomeric diversity arising from the position and configuration of functional groups. Traditional approaches to fatty acid characterisation have combined chromatography and mass spectrometry for a description of the composition of individual fatty acids while infrared (IR) spectroscopy has provided insights into the functional groups and bond configurations at the bulk level. Here we exploit universal 3-pyridylcarbinol ester derivatization of fatty acids to acquire IR spectra of individual lipids as mass-selected gas-phase ions.

Identification of Carbon-Carbon Double Bond Stereochemistry in Unsaturated Fatty Acids by Charge-Remote Fragmentation of Fixed-Charge Derivatives.

Separation and identification of fatty acid (FA) isomers in biological samples represents a challenging problem for lipid chemists. Notably, FA regio- and stereo-isomers differing in the location or () geometry of carbon-carbon double bonds are often incompletely separated and ambiguously assigned in conventional chromatography-mass spectrometry analyses. To address this challenge, FAs have been derivatized with the charge-switch derivatization reagents -methyl-pyridinium-3-methanamine and -(4-aminomethylphenyl)pyridinium and subjected to reversed-phase liquid chromatography-tandem mass spectrometry.

In Silico Optimization of Charge Separating Dyes for Solar Energy Conversion.

Dye-sensitized photoelectrochemical cells are promising devices in solar energy conversion. However, several limitations still have to be addressed, such as the major loss pathway through charge recombination at the dye-semiconductor interface. Charge separating dyes constructed as push-pull systems can increase the spatial separation of electron and hole, decreasing the recombination rate.

Automated assessment of redox potentials for dyes in dye-sensitized photoelectrochemical cells.

Sustainable solutions for hydrogen production, such as dye-sensitized photoelectrochemical cells (DS-PEC), rely on the fundamental properties of its components whose modularity allows for their separate investigation. In this work, we design and execute a high-throughput scheme to tune the ground state oxidation potential (GSOP) of perylene-type dyes by functionalizing them with different ligands. This allows us to identify promising candidates which can then be used to improve the cell's efficiency.

Efficient workflow for the investigation of the catalytic cycle of water oxidation catalysts: Combining GFN-xTB and density functional theory.

Photocatalytic water oxidation remains the bottleneck in many artificial photosynthesis devices. The efficiency of this challenging process is inherently linked to the thermodynamic and electronic properties of the chromophore and the water oxidation catalyst (WOC). Computational investigations can facilitate the search for favorable chromophore-catalyst combinations.

Laser Photodissociation Action Spectroscopy for the Wavelength-Dependent Evaluation of Photoligation Reactions.

The nitrile imine-mediated tetrazole-ene cycloaddition is a widely used class of photoligation. Optimizing the reaction outcome requires detailed knowledge of the tetrazole photoactivation profile, which can only partially be ascertained from absorption spectroscopy, or otherwise involves laborious reaction monitoring in solution. Photodissociation action spectroscopy (PDAS) combines the advantages of optical spectroscopy and mass spectrometry in that only absorption events resulting in a mass change are recorded, thus revealing the desired wavelength dependence of product formation.

Predicting wavelength-dependent photochemical reactivity and selectivity.

Predicting the conversion and selectivity of a photochemical experiment is a conceptually different challenge compared to thermally induced reactivity. Photochemical transformations do not currently have the same level of generalized analytical treatment due to the nature of light interaction with a photoreactive substrate. Herein, we bridge this critical gap by introducing a framework for the quantitative prediction of the time-dependent progress of photoreactions via common LEDs.

Systematic Computational Design and Optimization of Light Absorbing Dyes.

We present a workflow to aid the discovery of new dyes for the role of a photosensitive unit in the dye-sensitized photo-electrochemical cells (DS-PECs). New structures are generated in a fully automated way using the Compound Attachment Tool (CAT) introduced in this work. These structures are characterized with efficient approximate density functional theory (DFT) methods, and molecules with favorable optical properties are suggested for possible further use in DS-PECs.

Lithium, sodium, potassium and calcium amine-bis(phenolate) complexes in the ring-opening polymerization of rac-lactide.

Compounds of Li, Na, K and Ca of a tetradentate amino-bis(phenolato) ligand were prepared. Bimetallic compounds formulated as M[L](THF) (where M = Na, n = 1 (1·THF) or Li, n = 1 (2·THF)) were synthesized via the reaction of H[L] (where [L] = 2-pyridylmethylamino-N,N-bis(2-methylene-4-methoxy-6-tert-butylphenolato) with sodium hydride or n-butyllithium, respectively, in THF. Monometallic complexes MH[L](THF) (where M = Na, n = 1 (3·THF), Li, n = 0 (4) and K, n = 0 (5)) were obtained by reaction of H[L] with MN(SiMe) where M = Na, Li, or K.

Photoinduced Electron Transfer in Donor-Acceptor Complexes: Isotope Effect and Dynamic Symmetry Breaking.

Electron-nuclear (vibronic) coupling has emerged as an important factor in determining the efficiency of energy transfer and charge separation in natural and artificial photosynthetic systems. Here we investigate the photoinduced charge-transfer process in a hydrogen-bonded donor-acceptor molecular complex. By using real-time quantum-classical simulations based on time-dependent Kohn-Sham equations, we follow in detail the relaxation from the Franck-Condon point to the region of strong nonadiabatic coupling where electron transfer occurs.

Unprecedented Bifunctional Chemistry of Bis(acyl)phosphane Oxides in Aqueous and Alcoholic Media.

Tailor-made photoinitiators play an important role for efficient radical polymerisations in aqueous media, especially in hydrogel manufacturing. Bis(acyl)phosphane oxides (BAPOs) are among the most active initiators. Herein, we show that they display a remarkable photochemistry in aqueous and alcoholic media: Photolysis of BAPOs in the presence of water or alcohols provides a new delocalized π-radical, which does not participate in the polymerization.

Light-Controlled Orthogonal Covalent Bond Formation at Two Different Wavelengths.

We report light-induced reactions in a two-chromophore system capable of sequence-independent λ-orthogonal reactivity relying solely on the choice of wavelength and solvent. In a solution of water and acetonitrile, LED irradiation at λ =285 nm leads to full conversion of 2,5-diphenyltetrazoles with N-ethylmaleimide to the pyrazoline ligation products. Simultaneously present o-methylbenzaldehyde thioethers are retained.

Quantum dynamics studies of the dissociative chemisorption of CH on the steps and terraces of Ni(211).

The dissociative chemisorption of CH on the stepped Ni(211) surface is explored. The H and CH fragments preferentially bind to the surface along the step edge, and the barriers to dissociation are lowest over the step edge atoms, with activation energies of 0.57 and 0.

Visible Light-Induced Ligation via o-Quinodimethane Thioethers.

We introduce a photocaged diene system ( o-quinodimethane thioethers) based on o-methylbenzaldehydes ( o-MBAs) that can be activated with visible light. The pioneered system is accessible in a single step from commercially available starting materials in excellent yields. Variable synthetic handles can be attached to the photocaged diene, often without elaborate protecting group chemistry.

Photochemistry in Confined Environments for Single-Chain Nanoparticle Design.

Emulating nature's protein paradigm, single-chain nanoparticles (SCNP) are an emerging class of nanomaterials. Synthetic access to SCNPs is limited by ultralow concentrations, demanding reaction conditions, and complex isolation procedures after single-chain collapse. Herein, we exploit the visible light photodimerization of styrylpyrene units as chain folding mechanism.

Methane dissociation on the steps and terraces of Pt(211) resolved by quantum state and impact site.

Methane dissociation on the step and terrace sites of a Pt(211) single crystal was studied by reflection absorption infrared spectroscopy (RAIRS) at a surface temperature of 120 K. The C-H stretch RAIRS signal of the chemisorbed methyl product species was used to distinguish between adsorption on step and terrace sites allowing methyl uptake to be monitored as a function of incident kinetic energy for both sites. Our results indicate a direct dissociation mechanism on both sites with higher reactivity on steps than on terraces consistent with a difference in an activation barrier height of at least 30 kJ/mol.

Wavelength Dependence of Light-Induced Cycloadditions.

The wavelength-dependent conversion of two rapid photoinduced ligation reactions, i.e., the light activation of o-methylbenzaldehydes, leading to the formation of reactive o-quinodimethanes (photoenols), and the photolysis of 2,5-diphenyltetrazoles, affording highly reactive nitrile imines, is probed via a monochromatic wavelength scan at constant photon count.