Chemphyschem最新文献

The Cover Feature shows that the biochemical production of nitric oxide significantly affects various biological functions. For Cr^IIIL(ONO)₂]⁺, a decrease in the Cr^III−O with an increase of the Cr^IIIO−NO bond triggers NO delivery during excitation. There is also a significant change in the bond angle (Cr−O−NO) at S=3/2, enlarging the O−NO bond for the β-cleavage of NO. This reflects the energy difference observed between the low-spin doublet and high-spin quartet due to spin crossover (SCO). The pendant chromophore′s role in generating NO effectively enhances light absorption. More information can be found in the Research Article by J. Guadalupe Hernández and P. Thangarasu (DOI: 10.1002/cphc.202400700).

In this study, we systematically explored the stability and isomerism of neutral and dehydrogenated polycyclic aromatic hydrocarbons (PAHs) in various charge states, focusing on anthracene, acridine, and phenazine. Our findings highlight key aspects that deepen the understanding of these molecules' reactivity and stability, relevant in both laboratory and astrophysical contexts. Structural symmetry and the presence of nitrogen atoms significantly impact PAH stability and reactivity. The optimal site for the first dehydrogenation varies with charge state, with notable differences in stability observed across different positions and charge states. For the loss of two hydrogens, there is a clear competition between low and high spin states, influenced by the positions of the hydrogens lost. Infrared spectral analysis reveals characteristic frequencies of conjugated C_sp2-C_sp2 bonds and variations across different charge states. The elimination of H₂ typically occurs at adjacent carbons, forming bonds similar to triple bonds. Reaction networks for anthracene, acridine, and phenazine indicate preferred pathways for hydrogen loss, driven by the need to minimize charge repulsion and maintain aromaticity. Adjacent hydrogen loss is predominant in neutral and singly charged states, shifting to non-adjacent loss in higher charge states.

To date, preparing materials with highly dispersed metal nanoparticles without metal agglomeration on a solid support is challenging. This work presents an alternative approach for synthesizing NiCo species on hierarchical ZSM-5 materials derived from a ZSM-5@NiCoAl-LDHs composite. The designed material was prepared by the growth of a NiCo-layered double hydroxides (LDHs) precursor on the surface of hierarchical ZSM-5 nanosheets. The effect of the weight ratio of NiCo-LDHs precursor to ZSM-5 on the composite properties has been studied. The results show that 45 wt.% LDHs (ZSM-5@NiCoAl-LDHs-45) is the most suitable condition for preparing NiCoAl-LDHs/ZSM-5 composite, which promotes a strong interaction between bimetallic NiCo and hierarchical ZSM-5. The ZSM-5@NiCoAl-LDHs-45 showed a BET surface of 386 m² g^-1, in which the surface area has been re-allocated between microspores and mesopores due to the presence of NiCoAl-LDHs composite. The catalyst was also tested for CO₂ methanation at 380 °C under atmospheric hydrogen pressure. The results show that the catalyst could provide CO₂ conversion of up to 40 % at WSHV of 2.91 h^-1. Interestingly, it could not only promote methane but also provide a high selectivity of ethane, approximately 20.4 %. Moreover, the excellent catalytic stability of ethane production was illustrated over 24 hours of time-on-stream (TOS).

Presently, a sustainable electrochemical Nitrogen Reduction Reaction (NRR) has been essentially found to be viable on transition metal-based catalysts. However, being cost-effective and non-corrosive, metal-free catalysts present an ideal solution for a sustainable world. Herein, through a DFT-based study, we demonstrate metal-free NRR catalysts, boron quantum dots with 13 atoms as a case study and their chemically modified counterparts when anchored on graphitic carbon nitride (g-C₃N₄) surface. The best catalyst among the studied, a silicon-doped boron quantum dot with a cagelike structure, is found to favour the dinitrogen to ammonia reaction pathway with a low liming potential and potential rate-determining step (PDS) of -0.11 V and 0.27 eV, respectively. The present work demonstrates as to how boron quantum dots, which are reported to be experimentally synthesised, can be exploited for ammonia synthesis when supported on the surface. These catalysts effectively suppress the HER, thus establishing its suitability as an ideal catalyst. The work also represents a futuristic pathway towards a metal-free catalyst for NRR.

The spike protein is a vital target for therapeutic advancement to inhibit viral entrance. Given that the connection between Spike and ACE2 constitutes the initial phase of SARS-CoV-2 pathogenesis, obstructing this interaction presents a promising therapeutic approach. This work aims to find compounds from DrugBank that can modulate the stability of the spike RBD-ACE2 protein-protein complex. Employing a therapeutic repurposing strategy, we conducted molecular docking of over 9000 DrugBank compounds against the Spike RBD-ACE2 complex, on ten variants, including the wild-type. We also evaluated the intricate stability of the RBD-ACE2 proteins by molecular dynamics simulations, hydrogen bond analysis, RMSD analysis, radius of gyration analysis, and the QM-MM approach. We assessed the efficacy of the top ten candidates for each variant as an inhibitor. Our findings demonstrated for the first time that DrugBank small molecules can interact in three distinct modalities inside the extensive protein-protein interface of RBD and ACE2 complexes. The top ten analyses identified specific DrugBank candidates for each variant and molecules capable of binding to multiple variants. This comprehensive computational technique enables the screening and forecasting of hits for any big and shallow protein-protein interface drug targets.

With state-of-the-art modulation of the electronic structure, novel physiochemical properties are anticipated for two-dimensional (2D) materials for a wide variety of potential applications. Due to the presence of charge transfer from transition metal guests and 2D material hosts, intercalation of zero-valent transition metal atoms into the van-der Waals gap of 2D materials are ideal approach to tuning the electronic structure of 2D materials. In this paper, several electronic structure and activity investigations of zero-valent transition metal intercalations of 2D materials, as well as the general concepts behind the experimental exploration were introduced. Specifically, the transition metal intercalation render 2D materials novel physicochemical properties with potential applications ranges from electrocatalysis, small molecule identification to spintronics. Based on the works and concepts introduced in this paper, several challenges and opportunities related to this field were proposed from our perspective.

To mitigate the adverse effects of CO₂ emissions, CO₂ electroreduction to small organic products is a preferable solution and potential catalysts include the single-atom catalyst (SAC) which comprises individual atoms dispersed on 2D materials. Here, we used aluminum and phosphorus as the active sites for CO₂ electroreductions by embedding them on the 2D graphitic carbon nitride (g-C₃N₄) nano-surface. The resulting M-C₃N₄ (M=Al and P) SACs were computationally studied for the CO₂ electroreduction using density functional theory (DFT) and ab-initio molecular dynamics (AIMD) simulations. Computations showed that CO₂ can be adsorbed to the active sites in forms of a frustrated Lewis pair (Al/N or P/N) or single atom Al or P. The adsorbed CO₂ can be converted to various intermediates by gaining proton and electron (H⁺+e^-) pairs, a process simulated as electroreduction. While both SACs prefer to produce HCOOH with low potential determining steps (PDSs) and small overpotential values of 0.25 V and 0.08 V for Al-C₃N₄ and P-C₃N₄ respectively, to produce CH₄, P-C₃N₄ exhibits a lower potential barrier of 0.9 eV than Al-C₃N₄ (1.07~1.17 eV).

Infrared probes are chemical moieties whose vibrational modes are used to obtain spectroscopic information about structural dynamics of complex systems; in particular, of biomacromolecules. Here, we explore the vibrational spectroscopy and dynamics of a reagent, 3-(4-azidophenyl)propiolonitrile (AzPPN), for selectively tagging thiols in protein environments with a multifunctional infrared probe containing both, an azide and a nitrile chromophore. The linear infrared spectrum of AzPPN is heavily perturbed in the antisymmetric azide stretching region as a result of accidental Fermi resonances. Isotopically labeling the azide group at the β-position deperturbs the spectrum considerably and reveals two combination tones that mix with the antisymmetric stretching fundamental into a Fermi triad of hybrid vibrational excitations. Moreover, two-dimensional infrared (2DIR) spectra were recorded for ¹⁵N_β-labeled AzPPN, which reveal waiting-time-dependent spectral shifts of diagonal peaks and dynamic buildups of cross peaks. The 2DIR-spectral evolution is indicative of intramolecular distribution of the pump-induced excess vibrational energy into low-frequency modes of the molecule that are coupled to either the azide or the nitrile stretching transition dipoles. Finally, IR-pump/IR-probe spectra with selective narrowband excitation reveal a time constant of 2.3 ps for intramolecular vibrational redistribution (IVR) and 18 ps for the final energy dissipation into the solvent. The cross-peak dynamics corroborate a notion in which IVR within the AzPPN-molecule is an irreversible process.

Combinatorial effects of small molecules provide newer avenues to improve protein stability. The combined effect of two different classes of ILs on the stability and fibrillation propensity of lysozyme (Lyz) was investigated. Imidazolium-ILs (an aromatic moiety) with varying alkyl chains, methyl (MIC), butyl (BMIC) and hexyl (HMIC), and pyrrolidinium-IL (alicyclic moiety) with butyl substitution (BPyroBr) were chosen. The fibrillation was delayed by the addition of any of the IL. While added as a mixture with varying molar ratios, the presence of HMIC with MIC or BMIC at the ratio of 2:1 increased the fibrillation time synergistically by increasing lag time and reducing elongation rate. The protein stability was significantly reduced in these conditions compared to lower molar ratios of HMIC with MIC or BMIC. Molecular dynamics simulation studies indicated that upon adding Im-ILs water molecules were reduced around Lyz, whereas BPyroBr slightly increased the water around Lyz. Preferential interaction studies suggest that the preferential binding of HMIC with the protein was the most favored and it synergistically facilitated the preferential binding of MIC. Though BMIC was preferentially binding to the protein, it disfavoured the interaction of MIC. BMIC and BPyroBr had a competitive binding on the surface of Lyz. The results suggested that the mixture of ILs containing the longer alkyl chain destabilizes the protein and delays the fibril formation to a larger extent than the shorter alkyl chain ILs. Further, the effect of aromatic ILs could be greater than alicyclic ILs having the same alkyl chain length.

A new class of cyclic dipeptide-isatin hybrids was synthesized using 2,5-diketopiperazine and various isatin derivatives bearing flexible chains and extended aromatic rings in a double Knoevenagel condensation process. These new series demonstrate high solubility and good thermal stability with decomposition temperatures exceeding 370 °C, especially the molecular design with efficient space-filling (CI5 and CI6) stabilized columnar liquid crystalline phase. The hole and electron carrier mobility of the CI5 compound, measured using the space charge limited current (SCLC) technique, were found to be 9.46×10^-4 cm²/V.s and 7.88×10^-4 cm²/V.s respectively. The stabilization of columnar self-assembly and observation of ambipolar charge carrier mobility in cyclic dipeptide-isatin hybrids make them a promising class of self-assembling organic semiconductors.