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Conformational behaviors of trans-2,3- and trans-2,5-dihalo-1,4-diselenanes. A complete basis set, hybrid-density functional theory study and natural bond orbital interpretations

BROWSE_DETAIL_TITLE_ALTERNATE: Conformational behaviors of trans-2,3- and trans-2,5-dihalo-1,4-diselenanes. A complete basis set, hybrid-density functional theory study and natural bond orbital interpretations

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BROWSE_DETAIL_TYPE: Article

BROWSE_DETAIL_PUBLISH_STATE: Published

BROWSE_DETAIL_FORMAT: No File

BROWSE_DETAIL_LANG: English

BROWSE_DETAIL_REFEREED: YES

BROWSE_DETAIL_ISIWOS: YES

BROWSE_DETAIL_CREATORS: Nori-Shargh, Davood (Author), Mousavi, Seiedeh Negar (Author), KAYI, Hakan (Author),

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BROWSE_DETAIL_DOI: 10.1007/s00894-014-2249-x

BROWSE_DETAIL_URL: http://link.springer.com/article/10.1007%2Fs00894-014-2249-x

BROWSE_DETAIL_SOURCE: http://link.springer.com/article/10.1007%2Fs00894-014-2249-x


BROWSE_DETAIL_PUBLISHER: Journal of Molecular Modeling BROWSE_DETAIL_PUBLICATION_NAME: Conformational behaviors of trans-2,3- and trans-2,5-dihalo-1,4-diselenanes. A complete basis set, hybrid-density functional theory study and natural bond orbital interpretations BROWSE_DETAIL_PUBLICATION_LOCATION: Journal of Molecular Modeling BROWSE_DETAIL_PUBLICATION_DATE: 10-05-2014 BROWSE_DETAIL_PUBLICATION_VOLUME: 20 BROWSE_DETAIL_PUBLICATION_PAGE: 2249


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Complete basis set CBS-4, hybrid-density functional theory (hybrid-DFT: B3LYP/6-311+G**) based methods and natural bond orbital (NBO) interpretations have been used to examine the contributions of the hyperconjugative, electrostatic, and steric effects on the conformational behaviors of trans-2,3-dihalo-1,4-diselenane [halo = F (1), Cl (2), Br (3)] and trans-2,5-dihalo-1,4-diselenane [halo = F (4), Cl (5), Br (6)]. Both levels of theory showed that the axial conformation stability, compared to its corresponding equatorial conformation, decreases from compounds 1 → 3 and 4 → 6. Based on the results obtained from the NBO analysis, there are significant anomeric effects for compounds 1-6. The anomeric effect associated with the electron delocalization is in favor of the axial conformation and increases from compounds 1 → 3 and 4 → 6. On the other hand, dipole moment differences between the axial and equatorial conformations [Δ(μ eq - μ ax)] decrease from compounds 1 → 3. Although Δ(μ eq-μ ax) parameter decreases from compound 1 to compound 3, the dipole moment values of the axial conformations are smaller than those of their corresponding equatorial conformations. Therefore, the anomeric effect associated with the electron delocalizations (for halogen-C-Se segments) and the electrostatic model associated with the dipole-dipole interactions fail to account for the increase of the equatorial conformations stability on going from compound 1to compound 3. Since there is no dipole moment for the axial and equatorial conformations of compounds 4-6, consequently, the conformational preferences in compounds 1-6 is in general dictated by the steric hindrance factor associated with the 1,3-syn-axial repulsions. Importantly, the CBS-4 results show that the entropy difference (∆S) between the equatorial axial conformations increases from compounds 1 → 3 and 4 → 6. This fact can be explained by the anomeric effectassociated with the electron delocalization which affects the C2-Se bond orders and increase the rigidity of the corresponding rings. The Gibbs free energy difference values between the axial and equatorial conformations (i.e. ΔG ax-ax and ΔG eq-eq) of compounds 1 and 42 and 5 and also 3 and6 have been calculated. The correlations between the anomeric effectelectrostatic model, ΔG eq-ax, ΔG ax-ax, ΔG eq-eq, bond orders, dipole-dipole interactions, structural parameters and conformational behaviors of compounds 1-6 have been investigated.


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