Photoinduced processes in Fe(III) complexes with the pentadentate Schiff-base ligand Salten (N,N-bis[(2-hydroxyphenyl)methylene]-4-azaheptane-1,7-diamine), [Fe(Salten)Him]BPh4 (Him = imidazole, I) and Fe(Salten)Cl (II), were investigated. Photoinduced signals associated with heating of the sample and photoswitching of Fe(III) from the high-spin state (HS, S = 5/2) to the low-spin state (LS, S = 1/2) were detected using time-resolved electron paramagnetic resonance (TR EPR) spectroscopy at low temperatures (60 K for I, 40 K for II). It was found that the efficiency of photoinduced spin transition in the complex with chlorine ligand is higher than with imidazole ligand. Molecular structures of both spin states were optimized by density functional theory using the B3LYP* functional and def2-TZVP basis set. The calculations showed that the imidazole-containing complex has a larger HS–LS energy gap than the chlorine-containing complex. The results demonstrate a significant influence of the axial ligand on the electronic structure of Fe(III) complexes and photoinduced processes.
Clay minerals on celestial bodies such as Mars undergo irradiation by solar wind protons, leading to alterations in their structure and properties. This presents a significant challenge in remote sensing for identification and quantification of these clay minerals on celestial bodies. This study has investigated the effects of 5 MeV protons at a fluence level of 1010 protons/cm2 on the properties of water-intercalated halloysite. The absorption coefficient, refractive index and permittivity before and after irradiation have been compared and analyzed under terahertz frequency band. Following protons deposition into the halloysite, the absorption coefficient and refractive index both show a decrease trend. And both the absorption coefficient and refractive index much more relate with the sample thickness. Fitting permittivity with a double Debye model reveals that relaxation time τD decreases from 0.898 to 0.007 ps, and τ1 prongs from 0.008 ps to 0.892 ps, which strongly associated with proton-induced disruption of the hydrogen bond network within the interlayer water. Those results contribute to a deeper understanding of solar-wind effects on clay mineral properties, aiding their remote sensing identification on celestial bodies and providing insights into potential environment evolution.
Based on density functional theory, the catalytic mechanism of methanol oxidation reaction (MOR) on Pt electrodes is systematically investigated. Water activation and depoisoning are main factors in performance controlling of MOR. Pt electrodes exhibit activities in water activation via thermodynamic pathway, thereby facilitating methanol oxidation at low potentials. We proposed the reasonable reaction network and revealed the MOR are regulated by depoisoning steps. Methanol dehydrogenation becomes achievable at a low potential, manifesting itself through multiple pathways, with the elevated overpotential in MOR primarily attributed to water decomposition. Crucially, the depoison involving carbon-containing intermediates and OH/O emerge as the rate-limiting steps.
A first-principles investigation of the adsorption of Riparin I, II and III molecules on a zigzag boron nitride nanotube BNNT (5,0), together with a quantum-chemical characterization of the isolated molecules, was performed. The isolated Riparins exhibit increasing dipole moment (2.15−3.83 D), polarizability (199.63−210.76 a.u.), and electrophilicity (1.53−1.72 eV) from Riparin I to III, indicating enhanced reactivity. Stable BNNT–Riparin complexes are formed, with adsorption energies ranging from −0.661 to −0.777 eV and equilibrium adsorption distances of 2.34−2.68 Å, corroborated by charge analysis. Adsorption significantly modifies the electronic structure, producing charge redistribution, orbital hybridization, and band-gap reductions of up to 37% while preserving the structural stability of the nanotube. Riparin III exhibits the strongest interaction, consistent with the trends predicted from the isolated molecule properties. These findings highlight BNNT–Riparin systems as promising candidates for nanoscale sensing, drug delivery, and bio-nanoelectronic applications.
This study investigates stereodynamical characteristics of the Ca(1S) + H2 (v0 = 0, j0 = 1) → CaH (v’, j’) + H reaction by varying collision energy and initial H2 alignment. As a typical strong endothermic reaction, its reactivity increases monotonically with collision energy and initial H2 alignment effectively control the reaction. Perpendicular configuration shows the strongest promotion at low collision energies and parallel configuration gradually become the most pronounced configuration as collision energy increases. Higher rotational states are preferentially populated via the parallel configuration at low collision energies, while lower vibrational states dominate the product population at high collision energies, with perpendicular configuration exerting opposite effects. Parallel configuration enhances forward and backward scattering, while perpendicular configuration favors sideways scattering at higher collision energies.
With the development of intelligent agriculture, achieving highly sensitive and reliable detection of various hazardous gases in greenhouse environments has become a critical challenge. Here, this work employs density functional theory (DFT) to investigate the adsorption characteristics and gas sensing mechanisms of NO2, NH3, SO2 and H2S on the ZnO/WSSe heterojunction, and its environmental adaptability under coexisting H2O/O2 conditions is further assessed. The results indicate that all gas molecules preferentially adsorb on the ZnO side and exhibit strong chemisorption characteristics, with adsorption energies ranging from −1.153 to −1.286 eV, accompanied by significant charge transfer and orbital hybridization. At room temperature, the ZnO/WSSe heterojunction is more suitable as an adsorbent for the four target gases. However, with increasing temperature, the target gases can still desorb from the material surface within a relatively short time, indicating a certain recovery capability. Further analysis shows that H2O competes with the target gases for adsorption, whereas O2 promotes the adsorption of the target gases. Under complex environments with coexisting H2O and O2, the target gases can still be stably adsorbed and effectively identified through variations in the band gap and work function, demonstrating that the ZnO/WSSe heterojunction possesses excellent anti-interference ability and gas selectivity. This study provides a theoretical basis for the application of ZnO/WSSe heterojunctions in harmful gas adsorption and sensing under complex greenhouse environments.
The spin dynamics of water ice in the presence of external magnetic fields are investigated. The employed model is based on the approach introduced by Buntkowsky et al. (2008), which considers two nearest-neighbor water molecules and yields a four-spin system, as the abundant oxygen isotope has zero nuclear spin. The model is extended to include coupling to external magnetic fields, allowing us to analyze the interplay between magnetic dipole–dipole interactions and magnetic field coupling. Two types of configurations are examined: (i) static, homogeneous fields, corresponding to a time-independent interaction, and (ii) spatially varying sinusoidal fields in relative motion with the molecules, leading to a time-dependent interaction. All computations are performed within the density operator formalism. The ortho/para populations and the total spin projections are evaluated during the first tens of milliseconds following the gas-to-solid phase transition. For static homogeneous fields, we show that increasing field strength suppresses dipolar-induced depolarization. Assuming that all molecules are initially in the para state, we show that static homogeneous fields can drive the ortho population up to approximately 50%, whereas suitably chosen sinusoidal-field configurations can increase it beyond 90%. These results are relevant for schemes aiming to preserve or manipulate nuclear-spin polarization during deposition.
