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Synthesis and Catalytic Activity of Molybdenum Complexes Bearing Dihydroimidazole‐Based PCP‐Type Pincer Ligands Toward Nitrogen Fixation

Yamazaki, Yasuomi; Nakaya, Kaito; Otsuka, Hiroki; Nakamura, Taiji; Tanaka, Hiromasa; Yoshizawa, Kazunari; Nishibayashi, Yoshiaki

2026 ChemistryEurope

doi: 10.1002/ceur.202500494pmid: N/A

Ammonia is an essential compound that can be used as an ingredient for various chemicals and a next‐generation energy carrier for a carbon‐neutral society. Although the Haber‐Bosch process is the widely used industrial production method for ammonia, this method consumes a large amount of energy to conduct the catalysis under high pressure and temperature; therefore, the development of efficient catalysts for ammonia production under ambient reaction conditions should be one of the most important research topics for attaining carbon neutrality. In this study, we have developed a new series of molybdenum complexes bearing dihydroimidazole‐based PCP‐type pincer ligands, which can catalyze ammonia production from dinitrogen and water using samarium diiodide as a reductant under ambient conditions. Although the nonsubstituted complex did not exhibit efficient catalytic activity, introducing phenyl groups onto the dihydroimidazole skeleton substantially enhanced its catalytic activity. According to our electrochemical studies and density functional theory calculations, the phenyl groups effectively increased the electron‐accepting ability of the molybdenum complex, resulting in an increase in the strength of NH bonds (i.e., bond dissociation free energy (BDFENH)) in the corresponding imide complex, which is an important intermediate in the catalytic cycle for ammonia production, and its catalytic activity.

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Gold Nanoparticles–Dynamic Constitutional Frameworks as Adaptive Hybrid Conjugates for Enzyme Immobilization

Daakour, Sanaa; Mazzei, Rosalinda; Bazzarelli, Fabio; Vitola, Giuseppe; Giorno, Lidietta; Barboiu, Mihail

2026 ChemistryEurope

doi: 10.1002/ceur.202500252pmid: N/A

Dynamic constitutional frameworks (DCFs), connecting monomers via reversible covalent bonds, can initiate the assembly of gold nanoparticles (AuNps) with distinctive optoelectronic and surface chemical properties. A previous study indicated that these nanomaterials are particularly valuable for carbonic anhydrase immobilization and stabilization, with potential applications in biocatalysis and biosensing. However, further studies with different enzymes are needed to prove their universality. Therefore, this research focuses on immobilizing phosphotriesterase (PTE), an effective degrader of toxic organophosphates, on AuNp‐DCF conjugates. PTE is integrated with citrate‐ and PEG‐stabilized AuNps or imine‐based DCFs resulting in stable, homogeneous PTE‐AuNp‐DCF assemblies. The conjugates exhibit high bonding affinity and changes in the PTE's secondary structure, which did not deactivate the enzyme. The catalytic performance of immobilized PTE is evaluated by measuring the p‐nitrophenol (p‐NP) production in a similar way is sense the paraoxon during its enzymatic hydrolysis, used as a model organophosphate. PTE immobilized to PEG2000‐AuNps assembled with DCF‐PEG1500 shows the highest reaction rate (13.7 × 10−6 ± 0.82 M min−1), outperforming that immobilized to citrate‐stabilized AuNps (3.71 × 10−6 ± 0.21 M min−1). Furthermore, these PTE‐PEG‐AuNp‐DCF conjugates at a 1/25 molar ratio display a residual reaction rate, 3.6 times higher than that of all other conjugates. Free amino groups exposed on the surface of AuNps facilitate optimal assembly with DCF‐PEG through aldehyde/amino exchange reactions, preserving PTE activity. These results highlight the potential of PTE‐DCF‐AuNp conjugates to intercept and transform small molecules like paraoxon.

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Correlating Vibrational Spectra to C1 Surface Species on Nickel‐Based Hydrogenation Catalysts Using Density Functional Theory

Sterk, Ellen B.; Kappé, Bram T.; Monai, Matteo; Louwen, Jaap N.; Vogt, Eelco T. C.; Filot, Ivo A. W.; Weckhuysen, Bert M.

2026 ChemistryEurope

doi: 10.1002/ceur.202500338pmid: N/A

Understanding catalytic processes requires insights into the behavior of reactants, intermediates, and products at the surface of a solid catalyst. This is often studied via in situ or operando vibrational spectroscopy and by theoretical calculations. However, direct comparison between experimental and theoretical vibrational frequencies remains challenging and requires careful methodological treatment. Here, we present a systematic computational framework for calculating and scaling the fundamental vibrational frequencies of fourteen key intermediates involved in catalytic C1 reactions over nickel. Such intermediates were modeled on Ni(111), Ni(100), Ni(110), and Ni(211) crystal surfaces. Multiple density functional theory (DFT) methods and basis sets were benchmarked. Linear scaling equation (LSE) correction was applied to all computed wavenumbers. The result is a validated database of LSE‐corrected vibrational frequencies, designed to aid experimentalists in infrared (IR) spectral interpretation. We illustrate its application with a phenomenological evaluation of the CO adsorption region, comparing calculated spectra to IR spectra from CO2 methanation over four Ni/SiO2 catalysts. For this analysis, we used a dual‐model approach, computing CO∗ frequencies on both extended facets and a 1.439 nm Wulff‐constructed nanoparticle to account for size‐dependent effects. The analysis highlights how adsorption site and adsorbate interactions influence vibrational features, underscoring the need for both more complex models and complementary experiments to accurately capture effects, such as peak shifts, inhomogeneous broadening, and intensity transfer that govern the spectra of working catalyst surfaces.

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