A library of eight new fluoroquinolone–nuclease conjugates containing a guanidinoethyl or aminoethyl auxiliary pendant on the 1,4,7-triazacyclononane (TACN) moiety was designed and synthesized to investigate their potential as catalytic antibiotics. The Cu(II) complexes of the designer structures showed significant in vitro hydrolytic and oxidative DNA cleavage activity and good antibacterial activity against both Gram-negative and Gram-positive bacteria. The observed activity of all the Cu(II)–TACN–ciprofloxacin complexes was strongly inhibited in the presence of Cu(II)-chelating agents, thereby demonstrating “vulnerability” under physiological conditions. However, selected TACN–ciprofloxacin conjugates in their metal-free form efficiently cleaved plasmid DNA under physiological conditions. The lead compound 1 showed good DNase activity which was retained in the presence of strong metal chelators and exhibited excellent antibacterial activity against both Gram-negative and Gram-positive bacteria. Density functional theory calculations combined with quantum mechanics/molecular mechanics simulations suggest a general base–general acid mechanism for the hydrolytic DNA cleavage mechanism by compound 1.

Pyrene is a central building block in organic materials chemistry, valued for its rigid aromatic core, high fluorescence, and rich capacity for structural elaboration. However, the fundamental relationship between its annelation pattern and resulting electronic properties remains underexplored. In this work, we present a comprehensive computational study of 4,766 pyrene-based polybenzenoid hydrocarbons from the COMPAS-3D dataset. By systematically categorizing annelation patterns based on the positions of fused benzene rings, we uncover clear structure–property trends governing key electronic parameters, including molecular orbital energies and oxidation and reduction potentials. We find that annelations at different positions exert different effects, which combine additively, and that these trends correlate with the distribution of fixed versus migrating Clar sextets. We further show that extended linear annelation can dominate electronic behavior, superseding local pyrene effects. Additionally, we evaluate the effect of torsional strain, revealing a clear link between annelation patterns and molecular destabilization. These insights provide a framework for the rational design of functional pyrene-based molecules.

CO₂-containing synthesis gas is a relevant feedstock for the production of synthetic fuels using Fischer–Tropsch synthesis (FTS). We report the role of CO₂ in CO₂, CO, and H₂ mixed feeds over a cobalt-based catalyst at 220 °C and 21 bar in a packed bed reactor and define the process boundary conditions where CO₂ switches from an inert to a reactive gas in FTS. The C₅₊ selectivity remains above 78% even for CO₂-rich synthesis gas with 75% CO₂/(CO + CO₂). Using ¹³CO₂ isotopic labeling, the increase in methane selectivity is attributed to both CO and CO₂ methanation, which is limited by maintaining a H₂/CO outlet ratio below 10 and an outlet CO partial pressure above 0.2 bar, respectively. CO and CO₂ are proposed to adsorb on the same Co sites, and with CO adsorption being more favorable, we postulate that sufficient CO prevents CO₂ adsorption and reaction. These results overturn the prevailing assumption that C₅₊ selectivity is dictated by the CO₂ partial pressure or the CO₂/CO ratios. In situ modulated diffuse reflectance infrared Fourier transform spectroscopy confirms a positive relationship between CO surface coverage and CO partial pressure. From DFT and microkinetic modeling, enhanced CO and CO₂ methanation could be attributed to a lower surface coverage and a higher H₂ surface coverage. This work identifies boundaries for efficient cobalt-catalyzed mixed-feed FTS for synthetic fuel production.

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.

High-harmonic generation (HHG), the hallmark effect of attosecond science, is a nonperturbative nonlinear process leading to the emission of high harmonic light from gases and solids. In gases, extreme driving laser pulse intensities can deplete the ground state, suppressing harmonic emission during the trailing edge of the pulse. Here, we report pronounced ultrafast depletion dynamics during HHG in a gapless Dirac semimetal -- highly oriented pyrolytic graphite (HOPG). Remarkably, HOPG supports nonperturbative harmonic generation at laser intensities as low as $10^{10}$ W cm$^{-2}$, facilitated by its vanishing bandgap. Using two-color spectroscopy, we reveal the excitation dynamics of Dirac electron-hole pairs as it affects the emission of harmonics during the presence of the driving laser pulse. Notably, valence band depletion near the Dirac points leads to a marked suppression of interband harmonics and induces measurable temporal shifts. These observations are supported by simulations based on semiconductor Bloch equations. Our findings uncover a new regime of strong-field light-matter interaction in gapless solids and establish HHG as a sensitive, all-optical probe of ultrafast carrier dynamics, offering new opportunities for ultrafast optoelectronics in Dirac materials.

We report a method for the direct palladium-catalyzed cross coupling reactions of cyclopropenyl esters bearing a variety of substitution patterns with Csp² iodides. This reaction is largely insensitive to the electronic nature of the coupling partner. Tetramethylammonium acetate, a halide sequestrant, was exceptionally effective as an organic base. An observed KIE of 2.5 revealed C–H bond cleavage to be involved in the turnover-limiting step. This method enables the rapid assembly of cyclopropenes whose preparation previously required the use of toxic tin and arsenic reagents.

The interaction of very low energy nitrogen with diamond is motivated by the need to chemically control its near surface region with high lateral and depth resolution while maintaining its crystalline structure. To this aim, the interaction of 100 eV N₂⁺ ions - 50 eV N species upon collision with the surface - at doses in the 1 × 10¹⁴–2 × 10¹⁵ ions cm⁻² range, was investigated with polycrystalline diamond surfaces by in situ X-ray photoelectron spectroscopy (XPS) and high-resolution electron energy loss spectroscopy (HREELS). The full width at half maximum (FWHM) of the N(1 s) and C(1 s) XP peaks measured upon implantation increases with ion dose, due to compressive stress created by the nitrogen population within the confined penetration depth of the impinging ions, however, nitrogen thermal desorption results in a reversible decrease of these peaks FWHM. Annealing to 1000 °C shows that the nitrogen concentration decreases slowly till 500–600 °C, followed by a faster decrease at further high temperature. The residual nitrogen concentration in diamond after 1000 °C increases with the initial ion dose. HREELS measurements show the presence of C=N and -CNH bonding states, and the latter may be preferentially desorbed by annealing to ~700 °C. The N(1s) and C(1s) XP spectral analysis suggests that upon implantation, most of the nitrogen occupies interstitial sites, N_i. Upon annealing above ~600 °C, in competition with desorption, it recombines with mobile carbon vacancies, resulting in the formation of thermally stable substitutional nitrogen, N_s, and recovery of the near-surface diamond structure.

Ubiquitination is a critical post-translational modification that regulates key cellular processes such as protein degradation and DNA damage repair. Targeting a specific type of ubiquitin chain (e.g., Lys48 or Lys63-linked ubiquitin chain) via cyclic peptides presents a new strategy to modulate biological processes with therapeutic potential for different diseases. However, such a strategy remains challenging due to the obstacles of cell permeability and bioactivity. Here, we report a new approach to directly examine these parameters by combining palladium-mediated Cys arylation with in situ cell-based screening. Using CP4, a previously identified cyclic peptide modulator of Lys63-linked ubiquitin chains, we generated a focused library of arylated analogues and optimized the Pd-mediated arylation for cell-based screening. We discovered a new analog, CP-P12-ArH, that demonstrated enhanced binding affinity and robust bioactivity, as evidenced by increased γ-H2AX phosphorylation and apoptosis induction in cancer cells. Furthermore, CP-P12- ArH effectively inhibited the in vitro formation of NF-κB essential modulator (NEMO) biomolecular condensates by disrupting the elongation of Lys63-linked ubiquitin chains, offering a novel way to modulate NF-κB signaling. This work establishes a generalizable platform for the rapid optimization of cyclic peptide therapeutics targeting protein-protein interactions.

The feasibility of a hydrogen-based economy critically depends on the development of catalysts for the hydrogen evolution reaction (HER) that do not rely on Pt or other noble metals. Contemporary efforts are focused on developing first-row transition metal complexes that will be operative at low overpotentials and catalyze the reaction with high efficacy and turnover rates. We now report a surprisingly strong effect of bromide substituents on the structure, coordination chemistry, electronic spectrum, reduction potentials, and catalytic activity of an already electron-poor cobalt corrole. The six-coordinate cobalt(III) complex of the brominated corrole displays a very nonplanar macrocycle, its axial pyridines are perpendicular to each other, the maxima in the electronic spectrum are red-shifted by almost 70 nm, and it is reduced by 600 mV less negative potentials. It catalyzes the HER from an organic acid in an organic solvent with a very low onset potential of −0.96 V vs. the Fc⁺/Fc couple and has been used for the preparation of a catalyst-modified cathode to produce hydrogen gas from acidic water with 97% Faradaic efficacy at potentials as low as −0.4 V vs. RHE.

We now report a surprisingly strong effect of bromide substituents on the structure, coordination chemistry, electronic spectrum, reduction potentials, and catalytic activity of an already electron-poor cobalt corrole.

We introduce OxPot, a comprehensive open-access data set comprising over 15 thousand chemically diverse organic molecules. Leveraging the precision of DFT-derived highest occupied molecular orbital energies (E_HOMO), OxPot serves as a robust platform for accelerating the prediction of oxidation potential (E_ox). Using the PBE0 hybrid functional and cc-pVDZ basis set, we establish a strong near-linear correlation between E_HOMO and experimental E_ox values, achieving an exceptional correlation coefficient (R²) of 0.977 and a low root-mean-square error (RMSE) of 0.064. The correlation highlights the accuracy of OxPot as a machine learning (ML)-ready resource for E_ox prediction. To further facilitate future development of ML models, we extensively tested various algorithms and conducted a thorough feature importance analysis. This analysis offers valuable insights into the key molecular descriptors that influence E_ox predictions, thereby enhancing model interpretability and guiding the design of more effective predictive models. Furthermore, the computational efficiency of the methodology ensures rapid predictions of E_ox for additional chemically similar molecules, thereby increasing its applicability for large-scale molecular screening and broader applications in chemical research.