International Journal of Quantum Chemistry最新文献

Anthocyanidins are natural compounds soluble in water and known for their various biological activities. They show potent antioxidant activity towards free radicals. Herein, we investigate the effects of different types of polar and nonpolar solvents on the antioxidant activity of pelargonidin 3-glucoside. Density functional theory calculation has been performed using the hybrid functional M052X and the basis set 6-31+G(d,p). The solvent effects were considered implicitly by using IEFPCM formalism where acetone, aniline, benzene, water, methanol, chloroform, and cyclohexane are the attested solvents. The antioxidant activity is evaluated by calculating bond dissociation enthalpies of different OH groups (BDEs) and ionization potentials (IP) of pelargonidin 3-glucoside. In addition, the dipole moment and gap energy in different solvents were determined. The results show that the antioxidant activity of the pelargonidin 3-glucoside increases with polarity and that water is the favored media for free radical scavenging. The results show that an exponential potential decays of ionization potential with the dielectric constant of the tilted solvent. The favorable mechanism involved in free radical scavenging of free radicals by anthocyanidin pelargonidin 3-glucoside may depend on both the environment and the reactants. Herein, the effect of the solvent polarity on the stability of the transition state, activation, and the rate constant of the PC-ET mechanism of OOCH3 free radical scavenging by the pelargonidin 3-glucoside have been investigated. The obtained results showed that the free radical scavenging by 3-glucoside may be strongly affected by the environmental media and the type of solvents, that is, polar or nonpolar solvents.

Anthocyanidins are natural compounds soluble in water and known for their various biological activities. They show potent antioxidant activity towards free radicals. Herein, we investigate the effects of different types of polar and nonpolar solvents on the antioxidant activity of pelargonidin 3-glucoside. Density functional theory calculation has been performed using the hybrid functional M052X and the basis set 6-31+G(d,p). The solvent effects were considered implicitly by using IEFPCM formalism where acetone, aniline, benzene, water, methanol, chloroform, and cyclohexane are the attested solvents. The antioxidant activity is evaluated by calculating bond dissociation enthalpies of different OH groups (BDEs) and ionization potentials (IP) of pelargonidin 3-glucoside. In addition, the dipole moment and gap energy in different solvents were determined. The results show that the antioxidant activity of the pelargonidin 3-glucoside increases with polarity and that water is the favored media for free radical scavenging. The results show that an exponential potential decays of ionization potential with the dielectric constant of the tilted solvent. The favorable mechanism involved in free radical scavenging of free radicals by anthocyanidin pelargonidin 3-glucoside may depend on both the environment and the reactants. Herein, the effect of the solvent polarity on the stability of the transition state, activation, and the rate constant of the PC-ET mechanism of OOCH3 free radical scavenging by the pelargonidin 3-glucoside have been investigated. The obtained results showed that the free radical scavenging by 3-glucoside may be strongly affected by the environmental media and the type of solvents, that is, polar or nonpolar solvents.

We present a modification of our recently described method for learning potential energy surfaces (PES) via the bond-order charge-density matrix (CDM) formalism which makes use of the Hartree-Fock expression for the electronic energy. The modified approach also employs permutationally invariant polynomials (PIP) as a fitting basis for the individual CDM elements P_μν with μ and ν as Cartesian components. The key difference introduced presently is in the representation of P_μν as linear combinations of orientation-independent intrinsic density elements weighted by the bond direction cosines forming a complete basis, in contrast to the direct space-fixed Cartesian representation employed by us previously. The new approach identically preserves PES's rotational invariance and has the same root-mean-square error as the original formulation with ∼2.2 times fewer linear variational parameters. We demonstrate its efficiency on the fitting quality of the PESs of cyclo[10]carbon singlet and linear triplet states in full permutational symmetry space.

We present a modification of our recently described method for learning potential energy surfaces (PES) via the bond-order charge-density matrix (CDM) formalism which makes use of the Hartree-Fock expression for the electronic energy. The modified approach also employs permutationally invariant polynomials (PIP) as a fitting basis for the individual CDM elements P_μν with μ and ν as Cartesian components. The key difference introduced presently is in the representation of P_μν as linear combinations of orientation-independent intrinsic density elements weighted by the bond direction cosines forming a complete basis, in contrast to the direct space-fixed Cartesian representation employed by us previously. The new approach identically preserves PES's rotational invariance and has the same root-mean-square error as the original formulation with ∼2.2 times fewer linear variational parameters. We demonstrate its efficiency on the fitting quality of the PESs of cyclo[10]carbon singlet and linear triplet states in full permutational symmetry space.

The global diabatic potential energy surfaces (PESs) of the BH₂ system were constructed using neural network method in conjunction with a specific function based on 11 553 ab initio points. We have carefully examined the diagonal elements V₁₁, V₂₂ and the off-diagonal element V₁₂ of the diabatic PESs matrix and compared them with the ab initio points. The theoretical results show that the diagonal elements V₁₁ and V₂₂ can reasonably describe the non-adiabatic processes between the electronic states. The shape of the off-diagonal element V₁₂ is regular and can satisfy the group symmetry operations. To clarify the influence of non-adiabatic effects in B(2p²P) + H₂ reaction, both adiabatic and non-adiabatic dynamics calculations were performed based on the newly constructed diabatic PESs. In addition, the adiabatic dynamical results are compared with the non-adiabatic ones. The results show that the non-adiabatic effects play an important role in the reaction process, while the adiabatic dynamical results are not reliable.

The pharmacological potential of marine alkaloids is enormous due to their diverse bioactivities. In this work, we performed a comprehensive computational analysis of marine alkaloids, including Calcardine C, Ernstine A, Naamine H, Naamine I, Naamidine J, Naamidine K, Phorbatopsin D, and Phorbatopsin E, in connection with Mycothiol S-conjugate amidase (MycoSCoA), an essential enzyme for Mycobacterium tuberculosis metabolism. Frontier molecular orbital (FMO) analysis and geometry optimization show that Naamidine J is the most stable compound; its low HOMO–LUMO gaps suggest high reactivity. According to electrostatic potential mapping, Naamidine K has the highest charge distribution, which is in line with a higher binding potential. The strong intramolecular charge transfer of the lead compounds was further confirmed by Natural Bond Orbital (NBO) analysis. Molecular docking studies show that Naamidine K and Naamidine J have the highest binding affinities with MycoSCoA (−10.6 and −9.3 kcal/mol, respectively). These substances use a range of hydrophobic and hydrogen bonding interactions to create stable complexes. It is noteworthy that Naamidine J exhibited superior binding to 4EWL (−9.3 kcal/mol), which was sustained by a network of hydrogen bonds and π-interactions. The selectivity of the marine alkaloids was highlighted by the weakest interactions, which were shown by BOG and GOL. This in silico study highlights Naamidine K and J as promising candidates for further anti-tuberculosis drug development in general.

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 (U_L = −0.21 V), while Mo-N₃S-PC may selectively yield CH₄ at U_L = −0.29 V. Additionally, Fe-N₃S-PC catalyzes the formation of HCOOH, CH₃OH, and CH₄ at U_L = −0.15 V, and Cd-N₃S-PC facilitates CO, CH₃OH, and CH₄ generation at U_L = −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.