Theoretical Description of R–X⋯NH<sub>3</sub> Halogen Bond Complexes: Effect of the R Group on the Complex Stability and Sigma-Hole Electron Depletion
In the present work, a number of R−X⋯NH<sub>3</sub> (X = Cl, Br, and I) halogen bonded systems were theoretical studied by means of DFT calculations performed at the ωB97XD/6-31+G(d,p) level of theory in order to get insights on the effect of the electron-donating or e...
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MDPI AG
2020-01-01
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| Series: | Molecules |
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| Online Access: | https://www.mdpi.com/1420-3049/25/3/530 |
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| author | Juan Zurita Vladimir Rodriguez Cesar Zambrano Jose Ramón Mora Luis Rincón F. Javier Torres |
| author_facet | Juan Zurita Vladimir Rodriguez Cesar Zambrano Jose Ramón Mora Luis Rincón F. Javier Torres |
| author_sort | Juan Zurita |
| collection | DOAJ |
| description | In the present work, a number of R−X⋯NH<sub>3</sub> (X = Cl, Br, and I) halogen bonded systems were theoretical studied by means of DFT calculations performed at the ωB97XD/6-31+G(d,p) level of theory in order to get insights on the effect of the electron-donating or electron-withdrawing character of the different R substituent groups (R = halogen, methyl, partially fluorinated methyl, perfluoro-methyl, ethyl, vinyl, and acetyl) on the stability of the halogen bond. The results indicate that the relative stability of the halogen bond follows the Cl < Br < I trend considering the same R substituent whereas the more electron-withdrawing character of the R substituent the more stable the halogen bond. Refinement of the latter results, performed at the MP2/6-31+G(d,p) level showed that the DFT and the MP2 binding energies correlate remarkably well, suggesting that the Grimme’s type dispersion-corrected functional produces reasonable structural and energetic features of halogen bond systems. DFT results were also observed to agree with more refined calculations performed at the CCSD(T) level. In a further stage, a more thorough analysis of the R−Br⋯NH<sub>3</sub> complexes was performed by means of a novel electron localization/delocalization tool, defined in terms of an Information Theory, IT, based quantity obtained from the conditional pair density. For the latter, our in-house developed C++/CUDA program, called KLD (acronym of Kullback−Leibler divergence), was employed. KLD results mapped onto the one-electron density plotted at a 0.04 a.u. isovalue, showed that (i) as expected, the localized electron depletion of the Br sigma-hole is largely affected by the electron-withdrawing character of the R substituent group and (ii) the R−X bond is significantly polarized due to the presence of the NH<sub>3</sub> molecule in the complexes. The afore-mentioned constitutes a clear indication of the dominant character of electrostatics on the stabilization of halogen bonds in agreement with a number of studies reported in the main literature. Finally, the cooperative effects on the [Br—CN]<sub>n</sub> system (<i>n</i> = 1−8) was evaluated at the MP2/6-31+G(d,p) level, where it was observed that an increase of about ~14.2% on the complex stability is obtained when going from <i>n</i> = 2 to <i>n</i> = 8. The latter results were corroborated by the analysis of the changes on the Fermi-hole localization pattern on the halogen bond zones, which suggests an also important contribution of the electron correlation in the stabilization of these systems. |
| first_indexed | 2024-12-10T13:54:43Z |
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| last_indexed | 2024-12-10T13:54:43Z |
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| spelling | doaj.art-053d2dcfa84444e79fd5bcdf70e96ef32022-12-22T01:46:00ZengMDPI AGMolecules1420-30492020-01-0125353010.3390/molecules25030530molecules25030530Theoretical Description of R–X⋯NH<sub>3</sub> Halogen Bond Complexes: Effect of the R Group on the Complex Stability and Sigma-Hole Electron DepletionJuan Zurita0Vladimir Rodriguez1Cesar Zambrano2Jose Ramón Mora3Luis Rincón4F. Javier Torres5Instituto de Simulación Computacional (ISC-USFQ), Universidad San Francisco de Quito, Diego de Robles y Vía Interoceánica, Quito 17-1200-841, EcuadorInstituto de Simulación Computacional (ISC-USFQ), Universidad San Francisco de Quito, Diego de Robles y Vía Interoceánica, Quito 17-1200-841, EcuadorInstituto de Simulación Computacional (ISC-USFQ), Universidad San Francisco de Quito, Diego de Robles y Vía Interoceánica, Quito 17-1200-841, EcuadorInstituto de Simulación Computacional (ISC-USFQ), Universidad San Francisco de Quito, Diego de Robles y Vía Interoceánica, Quito 17-1200-841, EcuadorInstituto de Simulación Computacional (ISC-USFQ), Universidad San Francisco de Quito, Diego de Robles y Vía Interoceánica, Quito 17-1200-841, EcuadorInstituto de Simulación Computacional (ISC-USFQ), Universidad San Francisco de Quito, Diego de Robles y Vía Interoceánica, Quito 17-1200-841, EcuadorIn the present work, a number of R−X⋯NH<sub>3</sub> (X = Cl, Br, and I) halogen bonded systems were theoretical studied by means of DFT calculations performed at the ωB97XD/6-31+G(d,p) level of theory in order to get insights on the effect of the electron-donating or electron-withdrawing character of the different R substituent groups (R = halogen, methyl, partially fluorinated methyl, perfluoro-methyl, ethyl, vinyl, and acetyl) on the stability of the halogen bond. The results indicate that the relative stability of the halogen bond follows the Cl < Br < I trend considering the same R substituent whereas the more electron-withdrawing character of the R substituent the more stable the halogen bond. Refinement of the latter results, performed at the MP2/6-31+G(d,p) level showed that the DFT and the MP2 binding energies correlate remarkably well, suggesting that the Grimme’s type dispersion-corrected functional produces reasonable structural and energetic features of halogen bond systems. DFT results were also observed to agree with more refined calculations performed at the CCSD(T) level. In a further stage, a more thorough analysis of the R−Br⋯NH<sub>3</sub> complexes was performed by means of a novel electron localization/delocalization tool, defined in terms of an Information Theory, IT, based quantity obtained from the conditional pair density. For the latter, our in-house developed C++/CUDA program, called KLD (acronym of Kullback−Leibler divergence), was employed. KLD results mapped onto the one-electron density plotted at a 0.04 a.u. isovalue, showed that (i) as expected, the localized electron depletion of the Br sigma-hole is largely affected by the electron-withdrawing character of the R substituent group and (ii) the R−X bond is significantly polarized due to the presence of the NH<sub>3</sub> molecule in the complexes. The afore-mentioned constitutes a clear indication of the dominant character of electrostatics on the stabilization of halogen bonds in agreement with a number of studies reported in the main literature. Finally, the cooperative effects on the [Br—CN]<sub>n</sub> system (<i>n</i> = 1−8) was evaluated at the MP2/6-31+G(d,p) level, where it was observed that an increase of about ~14.2% on the complex stability is obtained when going from <i>n</i> = 2 to <i>n</i> = 8. The latter results were corroborated by the analysis of the changes on the Fermi-hole localization pattern on the halogen bond zones, which suggests an also important contribution of the electron correlation in the stabilization of these systems.https://www.mdpi.com/1420-3049/25/3/530sigma-holehalogen bondfermi-holeconditional pair densitykullback–leibler divergence |
| spellingShingle | Juan Zurita Vladimir Rodriguez Cesar Zambrano Jose Ramón Mora Luis Rincón F. Javier Torres Theoretical Description of R–X⋯NH<sub>3</sub> Halogen Bond Complexes: Effect of the R Group on the Complex Stability and Sigma-Hole Electron Depletion Molecules sigma-hole halogen bond fermi-hole conditional pair density kullback–leibler divergence |
| title | Theoretical Description of R–X⋯NH<sub>3</sub> Halogen Bond Complexes: Effect of the R Group on the Complex Stability and Sigma-Hole Electron Depletion |
| title_full | Theoretical Description of R–X⋯NH<sub>3</sub> Halogen Bond Complexes: Effect of the R Group on the Complex Stability and Sigma-Hole Electron Depletion |
| title_fullStr | Theoretical Description of R–X⋯NH<sub>3</sub> Halogen Bond Complexes: Effect of the R Group on the Complex Stability and Sigma-Hole Electron Depletion |
| title_full_unstemmed | Theoretical Description of R–X⋯NH<sub>3</sub> Halogen Bond Complexes: Effect of the R Group on the Complex Stability and Sigma-Hole Electron Depletion |
| title_short | Theoretical Description of R–X⋯NH<sub>3</sub> Halogen Bond Complexes: Effect of the R Group on the Complex Stability and Sigma-Hole Electron Depletion |
| title_sort | theoretical description of r x⋯nh sub 3 sub halogen bond complexes effect of the r group on the complex stability and sigma hole electron depletion |
| topic | sigma-hole halogen bond fermi-hole conditional pair density kullback–leibler divergence |
| url | https://www.mdpi.com/1420-3049/25/3/530 |
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