### Abstract

The electronic structure of diazepam was analyzed by pulsed ^{14}N nuclear quadrupole resonance (NQR) spectroscopy and density functional theory (DFT) calculations using the hybrid method B3PW91 with the 6-31G(d,p) basis set. Before searching for ^{14}N NQR spectra, a ^{35}Cl NQR line in diazepam was recorded to evaluate the degree of disorder in the crystal lattice and thus the chances to find much weaker NQR spectra of nitrogen-14 in this substance. In order to speed up the detection of weak NQR spectra, the spin-locked spin-echo multipulse sequence had to be applied. Despite the expected chemical inequivalence of the two nitrogen atoms in the diazepam molecule, only two resonance lines ν _{+} and ν _{-} were then found for this compound at 77 K. Possible reasons for this anomaly are discussed. From the experimental frequencies, the quadrupole coupling constant, the asymmetry parameter and the principal components of the electric field gradient tensor were determined. Those parameters were compared with the results of theoretical DFT calculations showing a reasonable accuracy of the DFT model used.

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

Pages (from-to) | 183-191 |

Number of pages | 9 |

Journal | Applied Magnetic Resonance |

Volume | 34 |

Issue number | 1-2 |

DOIs | |

Publication status | Published - Jul 2008 |

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### ASJC Scopus subject areas

- Atomic and Molecular Physics, and Optics

### Cite this

^{35}Cl NQR,

^{14}N NQR and DFT calculations to study the

^{14}N NQR spectrum of diazepam.

*Applied Magnetic Resonance*,

*34*(1-2), 183-191. https://doi.org/10.1007/s00723-008-0093-9

**Using the combined approach of ^{35}Cl NQR, ^{14}N NQR and DFT calculations to study the ^{14}N NQR spectrum of diazepam.** / Bronisz, K.; Ostafin, M.; Poleshchuk, O. Kh; Mielcarek, J.; Nogaj, B.

Research output: Contribution to journal › Article

^{35}Cl NQR,

^{14}N NQR and DFT calculations to study the

^{14}N NQR spectrum of diazepam',

*Applied Magnetic Resonance*, vol. 34, no. 1-2, pp. 183-191. https://doi.org/10.1007/s00723-008-0093-9

^{35}Cl NQR,

^{14}N NQR and DFT calculations to study the

^{14}N NQR spectrum of diazepam. Applied Magnetic Resonance. 2008 Jul;34(1-2):183-191. https://doi.org/10.1007/s00723-008-0093-9

}

TY - JOUR

T1 - Using the combined approach of 35Cl NQR, 14N NQR and DFT calculations to study the 14N NQR spectrum of diazepam

AU - Bronisz, K.

AU - Ostafin, M.

AU - Poleshchuk, O. Kh

AU - Mielcarek, J.

AU - Nogaj, B.

PY - 2008/7

Y1 - 2008/7

N2 - The electronic structure of diazepam was analyzed by pulsed 14N nuclear quadrupole resonance (NQR) spectroscopy and density functional theory (DFT) calculations using the hybrid method B3PW91 with the 6-31G(d,p) basis set. Before searching for 14N NQR spectra, a 35Cl NQR line in diazepam was recorded to evaluate the degree of disorder in the crystal lattice and thus the chances to find much weaker NQR spectra of nitrogen-14 in this substance. In order to speed up the detection of weak NQR spectra, the spin-locked spin-echo multipulse sequence had to be applied. Despite the expected chemical inequivalence of the two nitrogen atoms in the diazepam molecule, only two resonance lines ν + and ν - were then found for this compound at 77 K. Possible reasons for this anomaly are discussed. From the experimental frequencies, the quadrupole coupling constant, the asymmetry parameter and the principal components of the electric field gradient tensor were determined. Those parameters were compared with the results of theoretical DFT calculations showing a reasonable accuracy of the DFT model used.

AB - The electronic structure of diazepam was analyzed by pulsed 14N nuclear quadrupole resonance (NQR) spectroscopy and density functional theory (DFT) calculations using the hybrid method B3PW91 with the 6-31G(d,p) basis set. Before searching for 14N NQR spectra, a 35Cl NQR line in diazepam was recorded to evaluate the degree of disorder in the crystal lattice and thus the chances to find much weaker NQR spectra of nitrogen-14 in this substance. In order to speed up the detection of weak NQR spectra, the spin-locked spin-echo multipulse sequence had to be applied. Despite the expected chemical inequivalence of the two nitrogen atoms in the diazepam molecule, only two resonance lines ν + and ν - were then found for this compound at 77 K. Possible reasons for this anomaly are discussed. From the experimental frequencies, the quadrupole coupling constant, the asymmetry parameter and the principal components of the electric field gradient tensor were determined. Those parameters were compared with the results of theoretical DFT calculations showing a reasonable accuracy of the DFT model used.

UR - http://www.scopus.com/inward/record.url?scp=59849101151&partnerID=8YFLogxK

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U2 - 10.1007/s00723-008-0093-9

DO - 10.1007/s00723-008-0093-9

M3 - Article

VL - 34

SP - 183

EP - 191

JO - Applied Magnetic Resonance

JF - Applied Magnetic Resonance

SN - 0937-9347

IS - 1-2

ER -