Intercalation is a robust method for tuning the physical properties of a vast number of van der Waals (vdW) materials. However, the prospects of using intercalation to modify magnetism in van der Waals (vdW) systems and the associated mechanisms have not been adequately studied. In this work, we modulated magnetic order in XY antiferromagnet NiPS₃ single crystals by introducing pyridine molecules into the vdW’s gap under different thermal conditions. X-ray diffraction measurements indicated pronounced changes in the lattice parameter β, while magnetization measurements at in-plane and out-of-plane configurations exposed reversal trends in the crystals’ Néel temperatures through intercalation/deintercalation processes. The changes in magnetic ordering were also supported by three-dimensional thermal diffusivity experiments. The preferred orientation of the pyridine dipoles within the vdW gaps was deciphered via polarized Raman spectroscopy. The results highlighted the relationship between the preferential alignment of the intercalants, thermal transport, and crystallographic disorder, along with the modulation of anisotropy in the magnetic order. DFT + U calculations indicated that the varying interlayer exchange interactions, regulated by intercalants, were responsible for modulating samples’ magnetic ordering. The study uncovers the possible merit of intercalation for manipulating spin orientations in spin electronics and advanced quantum devices.

The mechanochemistry of small molecules is an exponentially growing area of investigation relevant to developing sustainable synthesis to reduce waste and energy consumption, with great potential in large-scale chemical manufacturing. Occasionally, mechanochemical processes exhibit different reactivities, resulting in varying product selectivity compared to solution processes. In this study, we investigate the catalytic mechanism of a solvent-free one-pot acylation reaction of dimedone and 3-phenylpropanoic acid using a solvent-free ball-mill approach. The mechanochemical procedure afforded complete chemoselectivity towards a single acylation product after short milling, contrary to solution studies that previously reported product mixtures. Selectivity towards a single acylation product is controlled by the choice of the catalytic base. Under these mechanical process conditions, 4-dimethylaminopyridine (DMAP) is the only base that promotes the formation of the more desirable C-acylation product, whereas other bases exclusively afford the O-acylation product. Based on experimental findings, supported by theoretical modeling, we provide a mechanistic understanding of the base-dependent chemoselectivity, which leads to an enolate esterification that, in the case of DMAP, is converted to the thermodynamic product via Fries rearrangement. Finally, we explore the reaction scope with additional dicarbonyl compounds and carboxylic acids.

Bicyclo[1.1.0]butane, the smallest and most strained (64 kcal/mol) saturated bicycle, often exhibits olefin-like reactivity despite containing only σ-bonds. Nucleophilic ring opening to cyclobutanes typically requires a bridgehead electron-withdrawing group (EWG). Our group recently reported a cyclopropene carbometallation-based route to stereodefined tri-, tetra-, and pentasubstituted bicyclobutanes. Utilizing the exceptional nucleophilicity of silyllithium reagents, we have developed a diastereoselective method to transform in situ generated highly substituted arylbicyclobutanes lacking EWGs into tetra/pentasubstituted silyl cyclobutanes.

Viscosity modifying agents (VMA) and superplasticizers (SP) are two common macromolecular admixture types for cementitious materials. VMAs are used to stabilize fresh cementitious materials, while SPs are used to disperse them. Most VMAs are bio-based polysaccharides that act in the water phase between particles; while most SPs are synthetic comb polymers, consisting of negatively charged backbones that help their adsorption to the cement particles' surface. The molecular structure of DNA contains elements of VMA – as it is a polysaccharide – and SP – as it is a polyanion. In this study, rheological measurements are used to compare how these three types of macromolecules (VMA, SP, and DNA) affect cementitious materials. It is found that DNA shows the combined effects of VMAs and SPs on cement paste: it lowers yield stress while at the same time maintaining or even increasing its viscosity, which permits reducing water content while avoiding bleeding or segregation of samples. Yet, the presence of DNA has a significant retardation impact on cement hydration, which is also a common side effect of VMAs and SPs.

Aromaticity is a fundamental concept in organic chemistry that has gradually been extended to many other areas in the chemical sciences, including organometallic chemistry. By replacing a CH unit in an aromatic hydrocarbon (e.g., benzene) with an organometallic fragment, novel metallaaromatic compounds with intriguing physicochemical properties can be synthesized. Yet, despite intense research efforts, the synthesis of their macrocyclic congeners remains challenging, mainly due to a lack of straightforward synthetic strategies. Here we report the synthesis of a carbene analog of the well-known PyBOX pincer ligand, termed CarBOX, that upon coordination to a low-valent metal center (e.g., Co or Rh) results in the formation of a bespoke macrocyclic metallaaromatic complex. 1H NMR analysis of the resulting cobalt complexes reveals a downfield chemical shift (Δδ ≈ 8.5 ppm) of a diagnostic methyl resonance, indicative of strong diatropic ring currents. The electronic properties of the resulting pincer complexes were further confirmed by density functional theory (DFT), including nucleus independent chemical shift (NICS), isomer stabilization energy (ISE), and the magnetically induced origin-independent electron current density, all of which support the metallaaromatic nature of the cobalt complexes. Overall, these findings establish a generalizable platform for accessing metallaaromaticity through coordination chemistry, expanding the design principles of aromatic systems to include through-metal π-delocalization opening up new avenues for electronic materials design and function.

In the past decade, metal-catalyzed [2π + 2π] cycloaddition reactions have gained significant momentum for the synthesis of substituted cyclobutanes and bicyclo[3.2.0]-heptanes. To date, earth-abundant metals that contain redox non-innocent (radical)-type ligands are most commonly used in these cycloaddition reactions, whereby the redox non-innocent ligand plays a crucial role in stabilizing the oxidation and spin-state of the metal center. Classical π-accepting ligands, however, are inactive for these transformations. Here, we report efficient [2π + 2π] cycloaddition reactions that are catalyzed by a cobalt(I) complex containing a traditional π-accepting but redox innocent PC_NHCP pincer ligand. Mechanistic and computational investigations revealed a classical Co(I)–Co(III) redox cycle on the singlet spin manifold, where oxidative cyclization is the rate-limiting step. Overall, the herein developed methodology exhibits a wide substrate scope and low catalyst loadings (<1 mol %) and is compatible with a variety of functional groups while occurring under mild conditions (40–60 °C, N₂) with short reaction times.

Catalytic conversion of NO_x into ammonia is a significant step towards sustainable energy, requiring efficient materials for environmental NO_x detection and its subsequent reduction to amines. While chemiresistive sensing has been realized as technically distinct from the conventional oxygen reduction reaction (ORR), the development of smart catalytic materials which can detect trace-level NO_x and also demonstrate efficient ORR capabilities is crucial. In this proof-of-concept work, Sb single atoms (SAs) have been monodispersed on a nitrobenzene-intercalated few-layered MnPS₃ crystal-surface, for efficient room-temperature NO₂ detection. The sensing properties have been found to be influenced by polarized-monochromatic light and SA loading, with the response being maximum at an ∼50° polarization angle for green light and 3.5% SA content. Under controlled experimental conditions of humidity and pressure, the abovementioned novel composition exhibited ORR response, with ammonia generated at a weight hourly space velocity of 40 000 ml g_cat⁻¹ h⁻¹ and a rate of 4700 μmol g⁻¹ h⁻¹. X-ray absorption spectroscopy revealed the atomic environment of Sb SAs. Quasi-operando micro-photoluminescence combined with Raman spectroscopy identified the role of the MnPS₃ network in facilitating surface NO₂ adsorption. Theoretical calculations delineated the selective and energetic role of Sb SAs in sensing and initiating the ORR, elucidating the reaction pathway in terms of a reduction in Gibbs energy.

Porphyrins are involved in numerous and very different chemical and biological processes, due to the sensitivity of their application-relevant properties to subtle structural changes. Applying modern machine learning methodology is very appealing for discovering structure–activity relationships that can be used for design of tailor-made porphyrins for specific purposes. For achieving this goal, a high-quality set consisting of 425 metal porphyrins was established via curation of 7590 porphyrin structures from the Cambridge crystallographic database. Using data-driven techniques for analyzing nonplanarity and “structural aromaticity” allowed for validation of common knowledge in the field as well as discovery of new relations. Aromaticity was found to be influenced differently by distinct nonplanar distortions. Nonplanarity is more sensitive to macrocycle substitutions than to metal or axial ligand effects, while ruffled distortions are dominated by axial ligand size and metal properties. These findings offer new insights into structure–property relationships in porphyrins, providing a data-driven foundation for targeted synthesis to tune aromaticity and nonplanarity. Despite data set limitations, this work demonstrates the value of machine learning in uncovering complex chemical trends.

Two-dimensional (2D) hexagonal materials have been intensively explored for multiple optoelectronic applications such as spin current generation, all-optical valleytronics, and topological electronics. In the realm of strong-field and ultrafast light-driven phenomena, it was shown that tailored laser driving such as polychromatic or few-cycle pulses can drive robust bulk photogalvanic (BPG) currents originating from the K/K' valleys. We here explore the BPG effect in 2D systems in the strong-field regime and show that monochromatic elliptical pulses also generically generate such photocurrents. The resultant photocurrents exhibit both parallel and transverse (Hall-like) components, both highly sensitive to the laser parameters, providing photocurrent control knobs. Interestingly, we show that the photocurrent amplitude has a distinct behavior vs. the driving ellipticity that can be indicative of material properties such as the gap size at K/K', which should prove useful for novel forms of BPG-based spectroscopies. We demonstrate these effects also in benchmark ab-initio simulations in monolayer hexagonal boron-nitride. Our work establishes new paths for controlling photocurrent responses in 2D systems that can also be used for multi-dimensional spectroscopy of ultrafast material properties through photocurrent measurements.

The Haber-Bosch process has provided an energy-intensive way to produce ammonia for over 100 years. However, alternative methods are required to lower pollution and enhance energy efficiency. Unfortunately, key mechanistic insights into the heterogeneous reduction of nitrogen and its intermediates are lacking. The nitrite reduction reaction (NO₂RR) is an important electrochemical reaction in the nitrogen cycle, playing a significant role in ammonia-based energy storage and wastewater remediation. Although the NO₂RR involves the transfer of multiple protons competing with the hydrogen evolution reaction (HER), the effect of the proton donor has not been investigated in heterogeneous electrocatalysis. We now present an electrochemical study of nitrite reduction in four buffer systems acting as proton donors: citrate, phosphate, 2-(N-morpholino)ethanesulfonic acid, and borate buffers. The chosen catalyst was a typical iron- and nitrogen-codoped carbon (FeNC) with atomically dispersed FeN₄ sites. All buffers except borate enhanced the NO₂RR considerably, while the reduction mechanism was independent of buffer identity. The kinetics of the reaction depended more strongly on buffer concentration than on the ${\mathrm{NO}}_2^{-}$ concentration. Furthermore, we propose a double role for the protonated buffer species: a crucial proton donor during the rate-determining reduction of an NO_x intermediate and an efficient pH regulator near the electrode. These key mechanistic insights into heterogeneous nitrite reduction help to understand proton-coupled electrocatalysis and contribute to the development of alternative nitrogen-based fuels.