• Heidar Raissi

      Articles written in Journal of Chemical Sciences

    • Theoretical study on β-aminoacroleine; Density functional theory, atoms in molecules theory and natural bond orbitals studies

      Heidar Raissi Mehdi Yoosefian Effat Moshfeghi Farzaneh Farzad

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      The characteristics of the intramolecular hydrogen bonding for a series of 19 different derivatives of 𝛽-aminoacroleine have been systematically analysed at the B3LYP/6-31G∗∗ level of theory. The topological properties of the electron density distributions for N-H$\cdots$O intramolecular bridges have been analysed by the Bader theory of atoms in molecules. The electron density (𝜌) and Laplacian ($\nabla^2 \rho$) properties at critical points of the relevant bonds, estimated by AIM calculations, showed that N-H$\cdots$O have low and positive character ($\nabla^2 \rho > 0$), consistent with electrostatic character of the hydrogen bond. The vibrational study of the hydrogen bonded systems showed negative (red) shifts for the $\nu_{(N−H)}$ stretching mode. The 𝜋-electron delocalization parameter (𝑄) as a geometrical indicator of a local aromaticity and the geometry-based HOMA have also been calculated. Furthermore, the analysis of hydrogen bond in this molecule and its derivatives by natural bond orbital (NBO) methods support the DFT results. The results of AIM and NBO analysis as well as $\nu_{(N−H)}$ were further used for estimation of the hydrogen bonding interactions and the forces driving their formation. The various correlations were found between geometrical, energetic and topological parameters. The substituent effect was also analysed and it was found that the strongest hydrogen bonds exist for N+(CH3)3 and Cl substituents while the weakest ones for COOCH3.

    • A comprehensive study of the structure, tautomeric properties, and conformational flexibility of 3-Hydroxy-propeneselenal

      Mehdi Yoosefian Heidar Raissi Saeedeh Soheili

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      In the present work, a conformational analysis of 3-Hydroxy-propeneselenal is performed using several computational methods, including HF, DFT (B3LYP), and G2MP2 levels of theory. The relative electronic energies, the molecular structure, and intramolecular hydrogen bond energies are reported. Twenty different conformers were obtained, the most stable ones being planar. The conformational preference of this molecule was found to be mainly determined by the formation of Se…H-O and Se-H…O intramolecular hydrogen bonds, which are assisted by 𝜋-electron resonance. The atoms in molecules (AIM) theory of Bader, which is based on topological properties of the electron density, was used to analyze critical points and to study the nature of hydrogen bonds in these systems. NMR and natural bond orbital (NBO) analyses were also performed for a better understanding of the nature of intramolecular interactions in 3-Hydroxy-propeneselenal. Furthermore, calculations for all the possible conformations of the title compound in solution were also carried out at the B3LYP/6-311++G(d,p) level of theory (in three models such as polarizable continuum model (PCM), IEFPCM, and self−consistent isodensity polarized continuum model (SCIPCM).

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