جستجوی مقالات مرتبط با کلیدواژه « QTAIM analysis » در نشریات گروه « علوم پایه »

In this paper, NMR and QTAIM analysis for three substituted of T2SA complex was investigated in the gas and four solvents at DFT level. Intermolecular O–H…N hydrogen bonds between 1,2,4,5-Tetrazine and Sulphurous acids enhance the stability of complex.1,2,4,5 Tetrazine is a highly reactive diene for [4] inverse-Diels–Alder cycloaddition processes and an excellent precursor to attain the pyridazine ring. 1,2,4,5-Tetrazines have been very widely utilized for the highly effective synthesis of natural products, bioactive compounds and ligands. The comparison between the donor and attractive group on hydrogen bonding intermolecular systems is discussed. The deshielding effects on hydrogen nucleus of this compound in solvents are referred to intermolecular hydrogen bonds which are controlled by dielectric constants. Dielectric constant increased the hydrogen atoms are deshielded, in the DMSO and water, the changes is small, because in theses polarity of solvent is very high. When donor group is substituted in this complex electron density is increased. The QTAIM results show that in the DMSO and water, the changes is small, because in theses polarity of solvent is very high. The NMR and QTAIM results are harmonious together in all cases. All calculations were performed using B3LYP method and 6- 311** basis set in GAUSSIAN09W and AIM2000 programs .

The main purpose of this research is to investigate computationally the tautomeric reaction pathway of 5-methyl-3-methylthio-1,2,4-triazole from the thermodynamical and mechanistical viewpoints. In this respect, density functional theory (DFT) in conjunction with the quantum theory of atoms in molecule (QTAIM) has been employed to model the energetic and electronic features of tautomeric mechanism in the gas phase. Moreover, the effect of two different solvents, dimethylformamide (DMF) and H2O, has been examined via the polarized continuum model (PCM) calculations. Then we have presented the potential energy profile for the two-step tautomeric reaction in the gas and solution phases and analyzed comparatively the energetic aspects of tautomers, intermediate and transition states. On the other hand, we have concentrated on the survey of tautomerism by means of topological electronic indices. Strictly speaking, QTAIM calculations have been performed to explore the variation of electronic density and its laplacian at some key bond critical points of tautomers, intermediate and transition states and also to interpret the proposed tautomeric mechanism.

The B3LYP/6-31++G** density functional calculations were used to obtain minimum geometries and interaction energies between the molecular hydrogen and nanostructures of fullerenes, C20 (cage), C20 (bowl), C19Si (bowl, penta), C19Si (bowl, hexa). The H2 molecule is set as adsorbed in the distance of 3Å at vertical position from surface above the pentagonal and hexagonal sites of nanostructures. By comparing of gap energies, electronic chemical potential, hardness and results of QTAIM (Quantum  Theory of Atom in Molecules) analysis, the Si atom substitution in hexa two- fold position of C20 (bowl)may be suitable for the adsorption of hydrogen molecule.