International Journal of Quantum Chemistry最新文献

The high nitrogen and high oxygen content of energetic dioxadiazine compounds makes them exhibit high detonation performance and good stability, showing possible application in both military and civilian fields. Energetic dioxadiazine compounds with intramolecular hydrogen bonds were designed and optimized, while introducing —NH₂, —NHNO₂, —CH₃, —NO₂, and —OH as modified groups. The bond order, density, enthalpy of formation, stability, detonation performance and inter/intramolecular interactions were analyzed. Results showed that the skeleton of 1,4,2,6-dioxadiazine and 1,4,2,5-dioxadiazine had good stability and symmetrical structure. Analysis of bond length revealed the strong hydrogen bonding between the hydroxyl group and dioxadiazine ring. The introduction of —NH₂ and —OH groups proved beneficial in increasing molecular planarity. Bond order analysis, molecular electrostatic potential (ESP) analysis and detonation parameter calculations showed that B5 and C5 have good stability and detonation properties. Crystal structure prediction suggested that B5 would most likely crystallize in monoclinic (P2₁ space group) while C5 would crystallize in orthorhombic (Pbca space group). Hirshfeld surface analysis indicated strong O···H and N···H interactions for compounds B5 and C5. The above results have a positive promoting effect on obtaining high-energy dioxadiazine compounds with high stability.

This theoretical investigation aims to evaluate the influence of iodine substitutions on the phenolic moiety of the pyridine Schiff bases harboring an intramolecular hydrogen bond (PSB-IHB) ancillary ligand within the monocationic. fac-[Re(CO)₃(N,N)(PSB-IHB)]⁺ architecture on photophysical properties, particularly emission range. Optimized structures of two Re(I) tricarbonyl complexes (C1 and C2) were analyzed, revealing a distorted octahedral coordination geometry. Geometric parameters were compared with experimental data from analogous complexes. NBO analysis confirmed the presence of intramolecular hydrogen bonds (IHBs) in both singlet and triplet states, providing significant stabilization. Theoretical calculations predicted three distinct absorption bands for all complexes in dichloromethane, indicating substantial electronic delocalization between the pyridinic and phenolic rings via the azomethine group. These findings underscore the crucial role of delocalization and donor–acceptor interactions in stabilizing Re(I) tricarbonyl complexes and their impact on photophysical properties. Emissions calculated for the C1 and C2 complexes were observed within the range of 632–643 nm. The presence of IHBs was found to be essential for modulating photophysical properties, with emissions attributed to ligand-to-ligand charge transfer transitions.

This study presents a comprehensive theoretical investigation into the scattering of electrons and positrons from nitrogen dioxide (NO₂) molecules across a broad energy ranging from 1 eV to 1 MeV. The focus of the analysis encompasses a variety of cross-sections, including differential, integrated elastic, inelastic, total ionization, total, momentum transfer and viscosity. Additionally, the study explores the spin polarization effects within electron/positron-NO₂ scattering events. Utilizing a combination of relativistic Dirac partial wave analysis, the independent atom model (IAM), and the screening adjusted independent atom model (IAMS), this research achieves a refined understanding of scattering mechanisms. Comparative assessments with prior theoretical and empirical findings reveal that the IAM approach yields lesser accuracy at lower energies, while maintaining commendable agreement with existing data at medium to high energies. The insights and methodologies developed herein are anticipated to contribute significantly to the advancement of future research in this domain.

Alzheimer's disease (AD) is a chronic neurodegenerative disorder characterized by progressive cognitive and behavioral decline. In this study, 2,4-dichloro-6,7-dimethoxyquinazoline (DCDQ) was extensively analyzed using a combination of spectroscopic and computational approaches. Geometric parameters and vibrational modes were computed using DFT/B3LYP/6-311++G(d,p), and experimental FT-IR, FT-Raman, and UV–vis spectrum confirmed the compound's structural properties. Time-dependent DFT (TD-DFT) calculations provided insights into the electronic structure, including HOMO-LUMO energies and global reactivity descriptors. Molecular electrostatic potential (MEP) analysis and Mulliken population studies identified reactive sites and bonding characteristics, while NBO analysis revealed significant hyperconjugative interactions contributing to stability. Advanced topological analyses (ELF, LOL, NCI, and RDG) and QTAIM studies were performed using Multiwfn software to explore the compound's electron density distribution. Biological relevance was established through molecular docking studies, which highlighted a strong binding affinity of DCDQ with the 4EY7 protein (binding energy: −8.2 kcal/mol), suggesting its potential as a potent acetylcholinesterase (AChE) inhibitor. Molecular dynamics simulations further validated the stability of the protein-ligand interaction. ADMET predictions also supported favorable pharmacokinetic and safety profiles of DCDQ. These findings collectively demonstrate the potential of DCDQ as a promising lead compound for the treatment of Alzheimer's disease, offering a solid foundation for future therapeutic development.

Configurational and conformational assignments of 11 Corynanthe-Tryptamine alkaloids (usambarane skeleton) were performed based on the correlation of the high-level calculated and experimental ¹H and ¹³C NMR chemical shifts. For some compounds, the reassignment of a number of individual signals together with spectral assignment of experimentally unresolved peaks was suggested. The different conformations of the C/D quinolizidine ring system appear strictly dependent of the structure of the side chain (ethyl-, vinyl- or ethylidenic); in the latter case, the configuration (E or Z) of the 19-20 double bond of the ethylidenic chain is determinant to establish a cis- or a trans-quinolizidine system of rings C/D. The conformation is also influenced by the equatorial or axial conformation of (C15) substituents.

Theoretical study on the structure and electronic properties of small Ni_n (n ≤ 15) clusters has been carried out in the framework of density functional theory. The equilibrium geometries, the bond length, average binding energy, and magnetic moment per atom of these clusters were calculated in detail. The clusters constitute an intermediate state of matter between the isolated atoms and the massive condensed phase, and they do not mimic the bulk structure and shows significant geometrical changes with size. The binding energy per atom increases monotonically with size, and the magnetic moment oscillates with the size. The more stable structures are closed structures with inter atomic distances between 2.13 and 2.76 Å. The Ni₂, Ni₇, Ni₉, Ni₁₂, and Ni₁₄ clusters are more stable than their neighboring clusters, and the most favorable channel for nickel clusters is the Ni₁₄ cluster.

We theoretically studied the triplet formation efficiency in positional isomers of bromine-substituted 3-Hydroxythiochromones. Dynamics simulations with relevant spin-orbit coupling parameters show ultrafast triplet formation with S₁ as the donor singlet and upper triplet excited states as receiver states. The near-degeneracy of S₂ with S₁ promotes nonadiabatic population transfer from S₁ to S₂ in isomers with bromine substitution at the 5th position of the parent molecule. This population transfer unfurls an additional intersystem crossing pathway involving S₂ and T₄, enabling this isomer to show a higher triplet efficiency. The excited-state intramolecular proton transfer process, promoted by low barrier energy, is operative and can affect the isomers' triplet formation efficiency. Moreover, the timescales of proton transfer and triplet formation can overlap, necessitating thorough experimental investigations to uncover the competitiveness of these simultaneous events.

Phenylene, a significant structural motif in organic chemistry, exhibits remarkable electron delocalization and stability. In this paper, we first present reduction formulas for computing the matching polynomial and the independence polynomial of any phenylene chain using the transfer matrix technique. We then derive computational formulas for the Hosoya index and the Merrifield–Simmons index of phenylene chains. Additionally, we obtain the expected values of the Hosoya index and the Merrifield–Simmons index for a random phenylene chain.

The main goal is to use the fractional natural decomposition approach to solve diffusion equations related to oil pollution. We examine a model that depicts the evolution of chemical processes in a network that burns helium. Elegant consolidations of nature transform with Adomian decomposition method are made possible by the Caputo operator with fractional order taken into consideration and hired algorithm. We looked at the expected model in a different sequence using fraction to show the expected algorithm's proficiency. Moreover, plots for various arbitrary orders have taken use of the physical characteristics of the obtained results. The obtained findings verify that the algorithm under consideration is highly efficient, methodical, straightforward to use, and accurate in examining the characteristics of the fractional differential system connected to related fields.