Azobenzene-based photoresponsive ionic liquids (ILs) exhibit unique light-modulated properties, yet the structural determinants of their isomerization and aggregation remain underexplored. Density functional theory (DFT) calculations were employed to systematically investigate the substituent effects, positions and cis/trans-isomerism of azobenzene-functionalized ILs ([XAzoC2DMEA]Br, X = CH3/CN/NH2/NO2/OCH3/OH). Key findings reveal that substituent electronic nature and positional isomerism critically regulate electrostatic potential (ESP) distribution, molecular volume, and hydrogen bond strength. Electron-withdrawing groups (CN, NO2) enhance anion-cation interactions by intensifying charge polarization, whereas electron-donating groups (NH2, OCH3) reduce interaction energies through electron density redistribution. Para-substituted trans-isomers demonstrate enhanced thermodynamic stability owing to optimized conjugation effects and minimized steric hindrance. Hydrogen bond networks stabilize ionic pairs, with Br− forming multiple interactions. Cluster analysis reveals cooperative stabilization in multi-ion aggregates, with cis-clusters achieving marginally stronger interactions at larger sizes due to adaptive hydrogen-bond networks. Electrostatic forces dominate ILs stabilization, while hydrogen bonds modulate dynamic aggregation processes. These insights advance the molecular-level design of photoresponsive ILs for applications in sensors, photo-switchable devices, and sustainable chemistry.
The luminescence characteristics of small molecules excited BN superatoms remain unexplored, despite their potential applications in material luminescence. In this study, we investigated the absorption and fluorescence emission spectra of three small molecules (pyrazine, pyridine, and benzene) adsorbed on B16N16 using first principle. Our results reveal that pyridine and pyrazine form stable chemisorption structures, namely pyrazine-B16N16 and pyridine-B16N16, while benzene forms a physisorption structure, benzene-B16N16-4V, upon adsorption. Both the chemisorption of pyrazine and pyridine and the physisorption of benzene strengthen the emission spectrum intensity of B16N16, but the enhancement effect of the former is more pronounced. Additionally, the influence of varying numbers of small molecule adsorption on spectral characteristics is discussed, noting that the adsorption of multi-small molecules weakens the absorption and emission spectra. The optical band gap analysis indicates that pyrazine-B16N16 has a narrower optical band gap than B16N16, pyridine-B16N16, and benzene-B16N16-4V, suggesting that the pyrazine-adsorbed system is more readily excited. These findings present a strategic approach to luminescent materials and serve as a theoretical foundation for experimental investigations.
The catalytic reduction of CO2 into high-value carbon-based compounds presents a promising strategy for sustainable energy supply and industrial applications. In this work, inspired by the experimentally synthesized Ga-N3S-PC catalyst, a catalyst for single-atom Ga doped graphene and modified with N/P/S atoms, which demonstrates outstanding performance in CO2 reduction reactions (CO2RR), we constructed 27 transition metal-doped TM-N3S-PC (TM = transition metal) catalysts to systematically explore their catalytic properties. Through first-principles calculations, we evaluated the structural stability of the catalysts, CO2 adsorption configurations, reaction mechanisms for four C1 products (CO, HCOOH, CH3OH, and CH4), and the competing hydrogen evolution reaction (HER). Among the designed catalysts, 23 exhibit high stability, while 22 demonstrate effective CO2 adsorption; the adsorption energy varies periodically with properties of transition metals: electronegativity and d-band center. Notably, Pt-N3S-PC may have selectivity for HCOOH production at a low limiting potential (UL = −0.21 V), while Mo-N3S-PC may selectively yield CH4 at UL = −0.29 V. Additionally, Fe-N3S-PC catalyzes the formation of HCOOH, CH3OH, and CH4 at UL = −0.15 V, and Cd-N3S-PC facilitates CO, CH3OH, and CH4 generation at UL = −0.38 V. Their catalytic performance is superior to that of the experimentally synthesized Ga-N3S-PC catalyst. These findings provide valuable insights for the rational design and synthesis of graphene-supported single-atom catalysts for efficient CO2 conversion.
Structures, energetics and chemical bonding in molecular and ionic complexes of diatomic halogens and interhalogens XX′ (X, X′ = Cl, Br, I) with hexamethylenetetramine (HMTA) were computationally studied at the M06-2X/def2-TZVP level of theory. The stability of the molecular HMTA·nXX′ complexes decreases with increasing n: 1 > 2 > 3 > 4 for all XX′. The bonding between HMTA and XX′ in molecular complexes is best described as donor–acceptor interaction. Complexes with interhalogens, in particular with ICl, feature stronger donor–acceptor interactions and their dissociation is predicted to be endergonic at room temperature. In contrast, the intermolecular interactions are predominantly van der Waals type or electrostatic. Intermolecular N…X interactions are too weak for building coordination polymers based on HMTA and molecular halogens.
We investigate the structural, elastic, and thermodynamic properties of spinel compounds MgSc2X4 (X = S, Se) under high pressure using first-principles calculations. The obtained equilibrium structures at zero pressure show good agreement with previous theoretical and experimental results. The elastic constants, bulk modulus, shear modulus, Young's modulus, Poisson's ratio, B/G ratio, sound velocity, and Debye temperature were calculated under zero pressure and high pressure conditions. The B/G ratio reveals that both materials exhibit ductility under high pressure. Based on the Born stability criteria for cubic crystals under pressure, MgSc2S4 and MgSc2Se4 demonstrate structural stability within the investigated pressure ranges (up to 14.5 GPa for MgSc2S4 and 11.5 GPa for MgSc2Se4), and are predicted to lose stability at 33.43 and 25.81 GPa, respectively. Calculated anisotropy factors indicate elastic anisotropy in these compounds. Furthermore, thermodynamic properties of MgSc2X4 (X = S, Se) under high temperature and pressure were investigated through the quasi-harmonic Debye model. This study provides theoretical foundations for potential high-pressure applications of MgSc2X4 (X = S, Se).
A global potential energy surface (PES) for the CH2(11A′) was constructed using neural network method based on high-level ab initio points. The topographic features of the PES were discussed and compared with available theoretical and experimental values. The results indicate that the present PES is accurate and reliable. To further clarify the reality of the PES, the dynamics calculations of the C(1D) + H2 → H + CH(X2Π) reaction were performed using time-dependent wave packet method. Some meaningful dynamic results including reaction probability, integral cross section, differential cross section, and rate constant were calculated and compared with previous theoretical and experimental values. The reasonable dynamics results indicate that the present PES can be used to perform any kind of dynamics studies.
Based on the newly reported nonadiabatic potential energy surfaces, comprehensive adiabatic and nonadiabatic dynamical calculations for the S+ + HD reaction were carried out within the collision energy range of 1.0–4.0 eV. To quantitatively evaluate the nonadiabatic effects, a systematic comparison was conducted between the adiabatic and nonadiabatic dynamical results. The analysis demonstrates that the nonadiabatic effect induces negligible variation on the reaction probabilities and total integral cross sections. However, significant nonadiabatic influences were observed in the vibrational-rotational state distributions of products. The differential cross section analysis unveiled a distinct reaction mechanism. The SH+ + D channel exhibited a strongly forward-peaked angular distribution, indicating predominant direct abstraction dynamics through collinear attack geometry. In contrast, the SD+ + H channel shows a prominent backward-scattering component, attributed to impulsive rebound dynamics characterized by hard-sphere collisions.
To elucidate the pressure dependence of orthorhombic Mo2BC properties, this study employs density functional theory (DFT) to investigate its mechanical, electronic, lattice dynamic, and thermal behavior. The obtained lattice parameters and elastic properties of Mo2BC exhibit strong agreement with existing theoretical findings. The band structure calculations reveal that orthorhombic Mo2BC maintains metallic behavior under pressures spanning 0–50 GPa. Mo2BC demonstrates mechanical (Born stability criteria) and dynamic stability up to 50 GPa, with elastic constants and moduli exhibiting a monotonic increase with applied pressure. Notably, pressure induces a brittle-to-ductile transition in Mo2BC within the 10–50 GPa. In-plane profiles of linear compressibility, shear modulus, and Young's modulus coupled with surface structural analyses highlight that anisotropy intensifies with increasing pressure. Furthermore, thermal properties (Gibbs free energy [F], internal energy [E], entropy [S], and heat capacity [CV]) under combined high-temperature and high-pressure conditions were systematically investigated.
B3LYP and M06-L density functional calculations have been performed to evaluate the binding phenomena of the Fe(II), Co(II), Ni(II), and Cu(II) ions with the biologically important mandelic acid (MA) ligand in the gas phase and in the aqueous PCM model. The influence of the metal nature, spin states, coordination mode, chelate effects, and ring strain was explored. The direct interactions of the Fe(II), Co(II), Ni(II), and Cu(II) ions with the deprotonated MA− ligand resulted in the stabilization of twenty-eight stable mandelate complexes. A similar chemical reactivity was observed for the Fe(II), Co(II), and Ni(II) ions towards the MA− form, with the highest ΔEBond values calculated for the Cu(II) complexes. The AIM, FMO, and NBO results indicate that the nature of all MO chemical bonds is partly ionic and covalent, with a medium strength bond. The IR and UV-Vis absorption spectra of MA− and mandelate complexes were calculated and compared to experimental spectra. The UV-Vis absorption bands of mandelate complexes involve metal-to-ligand charge transfer through d-π* electron transitions, particularly with relatively high intensities in the visible region of the spectrum for the five-coordinated Cu(II) complexes.
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