### Abstract

Infrared and Raman spectra are reported for the isotopic species of pyrrolidine-d_{0} (PY) and -d_{1} and for N-methylpyrrolidine-d_{0} (NMP), -d_{2}, -d_{3} and -d_{8}. A complete assignment of the experimentally observed bands to normal modes is presented and discussed in particular in the CH/CD stretching region. The molecular structures and harmonic force fields were calculated ab initio at the Hartree-Fock (HF), the second order Møller-Plesset (MP2) and the density functional theory (DFT) level with the 6-31G* basis set. The force fields were fitted by use of 7 (PY) and 4 (NMP) independent scale factors. The spectra calculated with the DFT force fields are in better agreement with the experiment than those calculated by the MP2 and HF force fields. Though some scaled fundamental frequencies show larger deviations from the experimental ones, the mean percentage deviations of calculated frequencies from experimental fundamentals are less than 2.6% for all isotopic species of PY and NMP under study. The results indicate that density functional theory is a reliable tool to get a deeper insight in the assignment of vibrational spectra and the nature of normal modes of pyrrolidine derivatives.

Original language | English |
---|---|

Pages (from-to) | 2537-2551 |

Number of pages | 15 |

Journal | Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy |

Volume | 53 |

Issue number | 14 |

Publication status | Published - Dec 1997 |

### Fingerprint

### Keywords

- Assignment of fundamentals
- Density functional theory
- Pyrrolidine derivatives
- Scale factors
- Vibrational analysis

### ASJC Scopus subject areas

- Spectroscopy

### Cite this

**Vibrational spectra and harmonic force fields of pyrrolidine derivatives : Comparison between HF, MP2 and DFT force fields.** / Billes, F.; Geidel, Ekkehard.

Research output: Contribution to journal › Article

*Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy*, vol. 53, no. 14, pp. 2537-2551.

}

TY - JOUR

T1 - Vibrational spectra and harmonic force fields of pyrrolidine derivatives

T2 - Comparison between HF, MP2 and DFT force fields

AU - Billes, F.

AU - Geidel, Ekkehard

PY - 1997/12

Y1 - 1997/12

N2 - Infrared and Raman spectra are reported for the isotopic species of pyrrolidine-d0 (PY) and -d1 and for N-methylpyrrolidine-d0 (NMP), -d2, -d3 and -d8. A complete assignment of the experimentally observed bands to normal modes is presented and discussed in particular in the CH/CD stretching region. The molecular structures and harmonic force fields were calculated ab initio at the Hartree-Fock (HF), the second order Møller-Plesset (MP2) and the density functional theory (DFT) level with the 6-31G* basis set. The force fields were fitted by use of 7 (PY) and 4 (NMP) independent scale factors. The spectra calculated with the DFT force fields are in better agreement with the experiment than those calculated by the MP2 and HF force fields. Though some scaled fundamental frequencies show larger deviations from the experimental ones, the mean percentage deviations of calculated frequencies from experimental fundamentals are less than 2.6% for all isotopic species of PY and NMP under study. The results indicate that density functional theory is a reliable tool to get a deeper insight in the assignment of vibrational spectra and the nature of normal modes of pyrrolidine derivatives.

AB - Infrared and Raman spectra are reported for the isotopic species of pyrrolidine-d0 (PY) and -d1 and for N-methylpyrrolidine-d0 (NMP), -d2, -d3 and -d8. A complete assignment of the experimentally observed bands to normal modes is presented and discussed in particular in the CH/CD stretching region. The molecular structures and harmonic force fields were calculated ab initio at the Hartree-Fock (HF), the second order Møller-Plesset (MP2) and the density functional theory (DFT) level with the 6-31G* basis set. The force fields were fitted by use of 7 (PY) and 4 (NMP) independent scale factors. The spectra calculated with the DFT force fields are in better agreement with the experiment than those calculated by the MP2 and HF force fields. Though some scaled fundamental frequencies show larger deviations from the experimental ones, the mean percentage deviations of calculated frequencies from experimental fundamentals are less than 2.6% for all isotopic species of PY and NMP under study. The results indicate that density functional theory is a reliable tool to get a deeper insight in the assignment of vibrational spectra and the nature of normal modes of pyrrolidine derivatives.

KW - Assignment of fundamentals

KW - Density functional theory

KW - Pyrrolidine derivatives

KW - Scale factors

KW - Vibrational analysis

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M3 - Article

VL - 53

SP - 2537

EP - 2551

JO - Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy

JF - Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy

SN - 1386-1425

IS - 14

ER -