Conformational analysis of N-methylformamide in ground S0 and excited S1 and T1 electronic states

Conformational analysis of N-methylformamide in ground S0 and excited S1 and T1 electronic states For conformers of the N-methylformamide (HCONHCH3) molecule, calculations of equilibrium geometry parameters, harmonic vibration frequencies, energy differences and potential barriers to conformational transitions were performed in the ground (S0) and lowest excited singlet (S1) and triplet (T1) electronic states. In the S0 state, the molecule exists in trans and cis stable conformations (having Cs symmetry). Our calculations show that the electronic excitations T1←S0 and S1←S0 cause changes in the structure of conformers: both HCON and HNCC fragments become pyramidal and rotate around the CN bond. As a result, in each excited electronic state under consideration, there are 12 minima forming six pairs of equivalent conformers separated by relatively small potential barriers. One- and two-dimensional potential energy surface sections corresponding to different intramolecular large-amplitude motions were calculated using the MP2/aug-cc-pVTZ (S0) and CASPT2/cc-pVTZ (S1 and T1) methods. Anharmonic vibrational problems for large-amplitude motions were solved, and the corresponding frequencies were estimated. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Quantitative Spectroscopy & Radiative Transfer Elsevier

Conformational analysis of N-methylformamide in ground S0 and excited S1 and T1 electronic states

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Publisher
Elsevier
Copyright
Copyright © 2016 Elsevier Ltd
ISSN
0022-4073
eISSN
1879-1352
D.O.I.
10.1016/j.jqsrt.2016.02.012
Publisher site
See Article on Publisher Site

Abstract

For conformers of the N-methylformamide (HCONHCH3) molecule, calculations of equilibrium geometry parameters, harmonic vibration frequencies, energy differences and potential barriers to conformational transitions were performed in the ground (S0) and lowest excited singlet (S1) and triplet (T1) electronic states. In the S0 state, the molecule exists in trans and cis stable conformations (having Cs symmetry). Our calculations show that the electronic excitations T1←S0 and S1←S0 cause changes in the structure of conformers: both HCON and HNCC fragments become pyramidal and rotate around the CN bond. As a result, in each excited electronic state under consideration, there are 12 minima forming six pairs of equivalent conformers separated by relatively small potential barriers. One- and two-dimensional potential energy surface sections corresponding to different intramolecular large-amplitude motions were calculated using the MP2/aug-cc-pVTZ (S0) and CASPT2/cc-pVTZ (S1 and T1) methods. Anharmonic vibrational problems for large-amplitude motions were solved, and the corresponding frequencies were estimated.

Journal

Journal of Quantitative Spectroscopy & Radiative TransferElsevier

Published: Jul 1, 2016

References

  • Theoretical studies on the stability of N-methylformamide in both liquid and gas phases
    Cordeiro, J.M.M.; Cordeiro, M.A.M.; Bosso, A.R.S.A.; Politi, J.R.S.
  • The very low methyl group V3 barrier of cis N-methylformamide: A–E doubling from the free jet rotational spectrum
    Fantoni, A.C.; Caminati, W.; Hartwig, H.; Stahl, W.

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