Thorsten Klüner

The selective oxyfunctionalization of C(sp3)–H bonds remains a central challenge in chemical synthesis. Although oxygenases and peroxygenases provide biocatalytic alternatives to metal-based chemical methods, their practical use is constrained by costly cofactor regeneration, toxic co-substrates, or limited selectivity. Molybdenum (Mo)-dependent alkyl dehydrogenases circumvent these limitations by employing water, rather than O2 or H2O2, as the oxygen source for hydroxylation in conjunction with an electron acceptor. Here, we combine enzymatic, structural, and computational analyses to characterize a Mo-dependent p-cymene dehydrogenase (pCDH) from an anaerobic hydrocarbon-degrading bacterium. Isolated pCDH selectively hydroxylates a variety of benzylic and allylic C(sp3)–H bonds. A 2.0 Å cryo-EM structure of the heterotrimeric enzyme in complex with p-cymene captures key states of the catalytic cycle. Structure-guided QM/MM modelling and docking rationalize the substrate scope and radical mechanism. These results identify water-dependent Mo-dehydrogenases as promising catalysts for selective C(sp3)–H oxyfunctionalization.

The dominance of inexpensive ferrites and high-performance rare-earth-based magnets on the global market causes a significant performance gap between these materials. Fe₂P-based materials are promising rare-earth-free candidates to bridge this gap, offering high magnetization and uniaxial anisotropy. In this study, density functional theory was employed to systematically analyze the influence of Si and Co substitution on the phase stabilities of such Fe_2−yCo_yP_1−xSi_x compounds. At 0 K, Si substitution destabilizes the compounds; however, this trend is reversed at elevated temperatures, where Si significantly enhances phase stability. In contrast, Co substitution reduces competition energies at 0 K but promotes instability with increasing temperature. For quaternary Fe_2−yCo_yP_1−xSi_x compounds, the combined presence of Si and Co leads to a pronounced expansion of the stability range of the hexagonal crystal structure, in reasonable agreement with available experimental observations. Starting from temperatures above 1000 K, several quaternary compounds exhibit negative competition energies, indicating thermodynamic stability. Among all investigated compositions, Fe_1.84Co_0.16P_0.84Si_0.16 stands out, combining particularly low competition energies with a previously reported mean-field Curie temperature of 557 K and a high magnetic hardness factor. These results identify Fe_1.84Co_0.16P_0.84Si_0.16 as a highly promising rare-earth-lean hard magnetic material for future applications.

Raman spectroscopy reveals low oxygen coverage on Pt sites, correlating with enhanced ORR activity. In line with DFT calculations, a clear weakening by ∼38 cm ⁻¹ ≈0.48 kJ mol ⁻¹ of Ir–O–Pt compared to the Ir–O–Ir bond results in lower OER activity.

Understanding the chemisorption of atoms on precious metal surfaces is of substantial interest for the rational design of heterogeneous and electrochemical catalysts. In this study, we report density functional theory (DFT) investigations of the chemisorption of atomic H and O on bimetallic Pt _x Ir _y (111) surfaces for bifunctional anode catalyst materials in polymer electrolyte membrane (PEM) fuel cells. We found that for both adsorbates, the adsorption on the Pt(111) surface is in general less exothermic than on the Ir(111) surface. Our study has revealed that chemisorption on the bimetallic surfaces becomes more stable with increasing number of Ir surface atoms at the adsorption site. While for hydrogen atoms the ONTOP sites yield the most negative adsorption energies, the chemisorption of oxygen atoms appears to be most stable on the FCC sites for both the mono- and bimetallic surfaces. Using the ab initio thermodynamics approach, we calculated phase diagrams for the chemisorption of H and O atoms on these metal surfaces in order to transfer our findings to finite temperature and pressure conditions. Our theoretical results may provide an improved understanding of the hydrogen oxidation reaction (HOR) and oxygen evolution reaction (OER) on intermetallic Pt _x Ir _y (111) surfaces and may be helpful for the rational design of new bifunctional PEM fuel cell anode catalyst materials.

Hybrid Density Functional Theory (DFT) calculations for multiple conformers of the insertion reactions of a methylenecyclopropane into the Ti−C bond of two differently α‐substituted titanaaziridines explain the experimentally observed differences in regioselectivity between catalytic hydroaminoalkylation reactions of methylenecyclopropanes with α‐phenyl‐substituted secondary amines and corresponding stoichiometric reactions of a methylenecyclopropane with titanaaziridines, which can only be achieved with α‐unsubstituted titanaaziridines. In addition, the lack of reactivity of α‐phenyl‐substituted titanaaziridines as well as the diastereoselectivity of the catalytic and stoichiometric reactions can be understood.

Nanoporous gold (NPG) is characterized by a bicontinuous network of nanometer-sized metallic struts and interconnected pores formed spontaneously by oxidative dissolution of the less noble element from gold alloys. The resulting material exhibits decent catalytic activity for low-temperature, aerobic total as well as partial oxidation reactions, the oxidative coupling of methanol to methyl formate being the prototypical example. This review not only provides a critical discussion of ways to tune the morphology and composition of this material and its implication for catalysis and electrocatalysis, but will also exemplarily review the current mechanistic understanding of the partial oxidation of methanol using information from quantum chemical studies, model studies on single-crystal surfaces, gas phase catalysis, aerobic liquid phase oxidation, and electrocatalysis. In this respect, a particular focus will be on mechanistic aspects not well understood, yet. Apart from the mechanistic aspects of catalysis, best practice examples with respect to material preparation and characterization will be discussed. These can improve the reproducibility of the materials property such as the catalytic activity and selectivity as well as the scope of reactions being identified as the main challenges for a broader application of NPG in target-oriented organic synthesis.