Industrial dinitrogen (N-2) reduction to ammonia in the Haber-Bosch synthesis is essential for producing fertilizers and, consequently, food. Methods wherein the energy for nitrogen activation is supplied by light could provide more sustainable alternatives to existing ones. The combination of a photosensitizer and a lanthanide catalyst is reported for an effective >2e(-) reduction of N-2 in what is the first transition-metal-free molecular photocatalyst for ammonia synthesis. The lanthanide is Earth-abundant Sm. The reaction proceeds at ambient pressure and temperature, with high turnover numbers (up to 98), with visible light irradiation in aqueous solvent mixtures and even pure water, and it uses an environmentally benign non-metallic sacrificial reductant. Nitrite and nitrate were also efficiently reduced to ammonia. Thus, the first photocatalytic co-reduction of nitrite and bicarbonate to urea using an Sm-based photocatalyst was achieved.

Various metal–organic frameworks (MOFs) containing trivalent cations (such as Fe3+, Al3+, and Cr3+) have been reported and have shown great potential in applications. However, the high structural diversity and strong electronic interactions between metal centers and their ligands make the molecular dynamics simulations of MOFs challenging. In this work, we developed new dummy atom models for Fe3+, Al3+, and Cr3+ cations, which can be used in classical molecular dynamics simulations of MOFs. In our models, the correct solvation free energies and metal–ligand distances can be simultaneously reproduced. Furthermore, the usefulness and transferability of our models were validated using the commonly studied MIL-100(M) (M = Fe3+, Al3+, Cr3+) and MIL-88B(Fe3+) systems. Our developed models offer a valuable tool for simulating complex systems containing Fe3+, Al3+, and Cr3+ cations with octahedral coordination structures.

Alcohols are highly common organic compounds but remain scarce as alkyl donors in synthetic procedures. Here, we describe an electrochemical procedure for their deoxygenative cross-electrophile coupling with hydrosilanes, furnishing organosilane products in good to excellent yields. Mechanistic studies provide insights into the operating pathways of this semi-paired electrolytic transformation, suggesting that silyl ethers are likely reaction intermediates. Furthermore, a unified mechanistic proposal is presented that accounts for observed reactivity differences with analogous deoxygenative electrocarboxylation.

Metal (hydro)oxides are among the most effective heterogeneous water oxidation catalysts. Elucidating the interactions between oxygen-bridged metal sites at a molecular level is essential for developing high-performing electrocatalysts. Here we demonstrate that adjacent metal-hydroxyl groups function as intramolecular proton–electron transfer relays to enhance water oxidation kinetics. We achieved this using a well-defined molecular platform with an aza-fused π-conjugated microporous polymer that coordinates molecular Ni or Ni–Fe sites that emulate the structure of the most active edge sites in Ni–Fe materials for studying the heterogeneous water oxidation mechanism. We combine experimental and computational results to reveal the origin of pH-dependent reaction kinetics for O–O bond formation. We find both the anions in solution and the adjacent Ni3+–OH site act as proton transfer relays, facilitating O–O bond formation and leading to pH-dependent water oxidation kinetics. This study provides significant insights into the critical role of electrolyte pH in water oxidation electrocatalysis and enhancement of water oxidation activity in Ni–Fe systems. (Figure presented.)

Ascorbic Acid (AA) has been the center of controversial dialogues and studies when it comes to cancer research, though recently it has gained interest as an anti-tumor agent. Here, we present an electroanalytical concept to determine AA based on a new fundamental finding: the reversible interaction of AA with carbon nanotubes (CNTs) under zero-current measurements (potentiometry). This interaction is systemically studied under several experimental conditions, aiming to provide specificity with the combination of a thin film of CNTs with a nanometer-sized plasticized polymeric membrane (ca. 300 nm in thickness). The resulting sensor shows a consistent sensitivity to AA of –33.53 ± 2.57 mV/decade (n = 17), presenting a linear range of response that includes from normal physiological to pharmacological AA concentrations (10–200 μM and 0.2–1 mM, respectively). Importantly, interferences such as uric acid (UA), sodium ion and lactate have a limited influence on the potentiometric response, in contrast to previously published sensors. In addition to the experimental evidence, computational simulations on the interactions of AA and UA with a graphene-based model were performed to provide insights in describing the very distinct experimental responses that were observed. Thus, the formulated hypothesis is supported by both experimental data and simulations, which has not been reported before, to the best of our knowledge. Furthermore, we demonstrate the suitability of the developed sensor for real sample analysis (undiluted human serum, saliva and urine). The significance of the developed sensor is three-fold: 1) analytical performance addressing several applications, 2) enhanced selectivity, specially towards UA, 3) simplicity of the concept in terms of materials and preparation that makes it compatible with micro- and nano-electrodes for further analytical applications never explored until now (e.g., intracellular measurements, nanoelectrochemistry, etc.)

CO2 conversion to value-added chemicals is a crucial technology toward carbon-neutral fuels. Photocatalysis using sunlight is an energy-efficient alternative to electrochemical and thermal CO2 reduction. Photocatalysts usually yield either CO or formate with varying degrees of selectivity. Herein, a lanthanide-based photocatalytic platform producing CO with the highest turnover to date is reported. The catalyst consists of a pendant amine for CO2 capture and a light-harvesting sensitizer that generates the reactive divalent lanthanide center. CO2 reduction to CO was possible with high selectivity and reactivity by virtue of a distinct mechanistic pathway involving Sm(II), carbamate, and CO2,- as identified intermediates. Attractive (bi)carbonate CO2 feedstocks were efficiently converted to CO. Depending on the conditions, the selective synthesis of formate, methane, and methanol was also possible, demonstrating the wide utility of the platform.

Being a program written primarily in Python that strictly adheres to modern object-oriented software engineering and parallel programming practices, VeloxChem is shown to be suitable for the development of (semi)automatized workflows that extend its scope from first-principles quantum chemical purism to hybrid quantum-classical interoperability and some degree of semiempiricism. Methods are presented for building complex systems such as metal-organic frameworks, constructing molecular mechanics and interpolation mechanics force fields, conformer searches, system solvation, determining free energies of solvation, and determining free energy profiles of reaction pathways using the empirical valence bond method. The implementations are made intuitive with opportunities for interactive plotting and 3D molecular structure illustrations through the use of Jupyter notebooks.

An analysis of an out-of-equilibrium cyclic reaction network which continuously converts a minor undesired product enantiomer to the desired major enantiomer by irreversible addition of chemical fuel and irreversible elimination of spent fuel is presented. The reaction network is maintained as long as fuel is added; interrupted fuel addition drives the system towards equilibrium, but the cyclic process restarts upon resumed fuel addition, as demonstrated by three consecutive fuel cycles. The process is powered by the hydrolysis of methyl cyanoformate to HCN and monomethyl carbonic acid, which decomposes to CO<inf>2</inf> and MeOH. The time it takes to reach steady state depends on the rate of conversion of the fuel and decreases with increased conversion rate. Three catalysts, one metal catalyst and two enzymes, together constitute an efficient regulation system allowing control of the forward, backward and waste-forming steps, thereby assuring the production of high yields of products with high enantiopurity.

The increasing concentration of CO₂ in the atmosphere and its impact on the climate are matters of significant concern. Extensive research is being conducted on molecular catalysts to electrochemically reduce CO₂ into valuable products to disrupt the unidirectional carbon flow. This study compares two manganese bipyridine catalysts, tailored with four or two benzylic diethylamine groups in the secondary coordination sphere. Either of these amine-bearing scaffolds positioned close to the Mn center serves as effective proton relays to facilitate the formation of the corresponding Mn hydride intermediate. Alongside competitive H₂ evolution, the reaction of this crucial intermediate with CO₂ leads to formate. Our findings underscore the pronounced influence of external Brønsted acids on product selectivity. Notably, when employing the catalyst bearing four amine groups, the HCOO⁻/H₂ ratio varies from 81 : 3 with 1.0 M iPrOH to 16 : 64 with 1.0 M PhOH, while the Mn complex adorned with two amine pendant groups consistently favors HCOO⁻, irrespective of the utilized proton sources. Infrared spectroelectrochemistry and density-functional theory calculations unveil distinct disparities in the reactivity of the Mn hydrides toward CO₂ due to the change of ligand bulkiness in the two cases. This work substantiates the importance of modulating spatial accessibility while modifying the second sphere encompassing molecular catalysts.

A range of derivatives of an iridium pincer complex with a bis-trifluoromethyl-substituted ligand have been studied to determine how their properties differ from those of similar systems. The emphasis is on derivatives valuable for catalytic acceptorless dehydrogenation, including intermediates and deactivation products. The studies highlight small but important differences in the electron richness of the metal, as indicated by CO-stretching frequencies and hydride structures, as well as their impact on the equilibria between dihydride and tetrahydride species. T1, 1JHD NMR studies and computational results highlight the effect of the electron-withdrawing groups on tetrahydride structures, indicating shortened H–H distances. Further, the equilibria of di- and tetrahydride species have been deduced using 2D-EXSY NMR spectroscopy, showing faster hydrogen elimination in the complex with electron-withdrawing groups incorporated into the ligand.