Computational studies, NMR, Raman and infrared spectral analysis of centrosymmetric (2Z,4Z)-Hexa-2,4-dienedinitrile

Tarek A. Mohamed, Ibrahim A. Shaaban, Usama A. Soliman, Wajdi Zoghaib

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

The Raman (50-3500cm-1) and infrared (200-3500cm-1) spectra of (2Z,4Z)-Hexa-2,4-dienedinitrile (C6H4N2; cis,cis-HDDN) have been recorded. Initially, three conformers were proposed based on following point groups: C2h, C2v and C2 (gauche). For comparison purposes, M05-2X, M06-2X method were used in addition to B3LYP, MP2=full and MP4=full quantum mechanical calculations employing 6-31G(d) and 6-311+G(d,p) basis sets using Gaussian 09 program. Aided by potential energy surface scan, the C2h conformer is verified as a global minimum and the gauche (C2) being a local minimum with an energy barrier of 2.82kcal/mol. The energy difference ranged from 4.87 to 13.70kcal/mol favors the C2h conformer in good agreement with Raman and infrared spectral analysis. These results were also supported by the observed J value (H9-H10) at 10.8Hz which is consistent to 10.19Hz estimated for centrosymmetric conformer (C2h) rather than 4.81Hz predicted for gauche (C2). Complete vibrational assignments are proposed herein based on normal coordinate analysis (NCA) and potential energy distributions (PEDs) combined with theoretical vibrational frequencies and force constants in internal coordinates. It is crucial that NCA using VEDA 4 program with mixing shows large deviations from ours due to neglecting symmetry elements while mixing molecular vibrational motions. The results of these spectroscopic and theoretical studies are reported herein and compared with similar molecules whenever appropriate.

Original languageEnglish
Article number1950011
JournalJournal of Theoretical and Computational Chemistry
Volume18
Issue number2
DOIs
Publication statusPublished - Mar 1 2019

Fingerprint

Spectrum analysis
spectrum analysis
Nuclear magnetic resonance
Infrared radiation
Point groups
Potential energy surfaces
nuclear magnetic resonance
Energy barriers
Vibrational spectra
Potential energy
potential energy
Molecules
energy distribution
deviation
energy
symmetry
molecules

Keywords

  • (2Z
  • 4-dienedinitrile
  • 4Z)-Hexa-2
  • conformational stability
  • infrared and Raman spectra
  • quantum mechanical calculations
  • vibrational assignments

ASJC Scopus subject areas

  • Computer Science Applications
  • Physical and Theoretical Chemistry
  • Computational Theory and Mathematics

Cite this

Computational studies, NMR, Raman and infrared spectral analysis of centrosymmetric (2Z,4Z)-Hexa-2,4-dienedinitrile. / Mohamed, Tarek A.; Shaaban, Ibrahim A.; Soliman, Usama A.; Zoghaib, Wajdi.

In: Journal of Theoretical and Computational Chemistry, Vol. 18, No. 2, 1950011, 01.03.2019.

Research output: Contribution to journalArticle

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AU - Mohamed, Tarek A.

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AU - Soliman, Usama A.

AU - Zoghaib, Wajdi

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AB - The Raman (50-3500cm-1) and infrared (200-3500cm-1) spectra of (2Z,4Z)-Hexa-2,4-dienedinitrile (C6H4N2; cis,cis-HDDN) have been recorded. Initially, three conformers were proposed based on following point groups: C2h, C2v and C2 (gauche). For comparison purposes, M05-2X, M06-2X method were used in addition to B3LYP, MP2=full and MP4=full quantum mechanical calculations employing 6-31G(d) and 6-311+G(d,p) basis sets using Gaussian 09 program. Aided by potential energy surface scan, the C2h conformer is verified as a global minimum and the gauche (C2) being a local minimum with an energy barrier of 2.82kcal/mol. The energy difference ranged from 4.87 to 13.70kcal/mol favors the C2h conformer in good agreement with Raman and infrared spectral analysis. These results were also supported by the observed J value (H9-H10) at 10.8Hz which is consistent to 10.19Hz estimated for centrosymmetric conformer (C2h) rather than 4.81Hz predicted for gauche (C2). Complete vibrational assignments are proposed herein based on normal coordinate analysis (NCA) and potential energy distributions (PEDs) combined with theoretical vibrational frequencies and force constants in internal coordinates. It is crucial that NCA using VEDA 4 program with mixing shows large deviations from ours due to neglecting symmetry elements while mixing molecular vibrational motions. The results of these spectroscopic and theoretical studies are reported herein and compared with similar molecules whenever appropriate.

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