The Antagonist Effect of Nitrogen Lone Pair: 3JHF versus 5JHF

Thaís M. Barbosa; Renan V. Viesser; Lucas G. Martins; Roberto Rittner; Cláudio F. Tormena

doi:10.1002/cphc.201800073

The Antagonist Effect of Nitrogen Lone Pair: ³J_HF versus ⁵J_HF

Thaís M. Barbosa, Renan V. Viesser, Lucas G. Martins, Roberto Rittner, Cláudio F. Tormena

Research output: Contribution to journal › Article (Contribution to Journal) › peer-review

7 Scopus citations

Abstract

The long-range scalar coupling constant between proton and fluorine nuclei, ⁵J_HF, is observed to be larger than ³J_HF in the pyrimidinyl moiety of voriconazole. A set of smaller molecules is chosen (fluorobenzene, N-methyl-2-fluoropyridine, N-methyl-3-fluoropyridine, 3-fluoropyridine, 5-pyrimidine, and 2-fluoropyridine) to evaluate the influence of the nitrogen atom in the experimental J_HF values. Spectral aliased pure shift heteronuclear single quantum coherence spectroscopy (SAPS-HSQC) is applied to determine the relative sign between the J_CF and J_HF scalar couplings. Theoretical calculations show that the ³J_HF and ⁵J_HF coupling constants can be described mainly by a Fermi contact (FC) transmission mechanism. A decomposition analysis of J_HF in terms of localized molecular orbital (LMO) contributions allows us to determine that the interaction involving the nitrogen lone pair (LPN) is the main reason for the larger ⁵J_HF compared to ³J_HF. Our analysis indicates that delocalization of LPN has a positive contribution to the long-range coupling, while a negative one is observed for ³J_HF.

Original language	English
Pages (from-to)	1358-1362
Number of pages	5
Journal	ChemPhysChem
Volume	19
Issue number	11
DOIs	https://doi.org/10.1002/cphc.201800073
State	Published - 5 Jun 2018
Externally published	Yes

Keywords

coupling constants
fluorinated compounds
NMR
orbital decomposition analysis
pyrimidinyl moiety

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title = "The Antagonist Effect of Nitrogen Lone Pair: 3JHF versus 5JHF",

abstract = "The long-range scalar coupling constant between proton and fluorine nuclei, 5JHF, is observed to be larger than 3JHF in the pyrimidinyl moiety of voriconazole. A set of smaller molecules is chosen (fluorobenzene, N-methyl-2-fluoropyridine, N-methyl-3-fluoropyridine, 3-fluoropyridine, 5-pyrimidine, and 2-fluoropyridine) to evaluate the influence of the nitrogen atom in the experimental JHF values. Spectral aliased pure shift heteronuclear single quantum coherence spectroscopy (SAPS-HSQC) is applied to determine the relative sign between the JCF and JHF scalar couplings. Theoretical calculations show that the 3JHF and 5JHF coupling constants can be described mainly by a Fermi contact (FC) transmission mechanism. A decomposition analysis of JHF in terms of localized molecular orbital (LMO) contributions allows us to determine that the interaction involving the nitrogen lone pair (LPN) is the main reason for the larger 5JHF compared to 3JHF. Our analysis indicates that delocalization of LPN has a positive contribution to the long-range coupling, while a negative one is observed for 3JHF.",

keywords = "coupling constants, fluorinated compounds, NMR, orbital decomposition analysis, pyrimidinyl moiety",

author = "Barbosa, {Tha{\'i}s M.} and Viesser, {Renan V.} and Martins, {Lucas G.} and Roberto Rittner and Tormena, {Cl{\'a}udio F.}",

note = "Publisher Copyright: {\textcopyright} 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim",

year = "2018",

month = jun,

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doi = "10.1002/cphc.201800073",

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T1 - The Antagonist Effect of Nitrogen Lone Pair

T2 - 3JHF versus 5JHF

AU - Barbosa, Thaís M.

AU - Viesser, Renan V.

AU - Martins, Lucas G.

AU - Rittner, Roberto

AU - Tormena, Cláudio F.

PY - 2018/6/5

Y1 - 2018/6/5

N2 - The long-range scalar coupling constant between proton and fluorine nuclei, 5JHF, is observed to be larger than 3JHF in the pyrimidinyl moiety of voriconazole. A set of smaller molecules is chosen (fluorobenzene, N-methyl-2-fluoropyridine, N-methyl-3-fluoropyridine, 3-fluoropyridine, 5-pyrimidine, and 2-fluoropyridine) to evaluate the influence of the nitrogen atom in the experimental JHF values. Spectral aliased pure shift heteronuclear single quantum coherence spectroscopy (SAPS-HSQC) is applied to determine the relative sign between the JCF and JHF scalar couplings. Theoretical calculations show that the 3JHF and 5JHF coupling constants can be described mainly by a Fermi contact (FC) transmission mechanism. A decomposition analysis of JHF in terms of localized molecular orbital (LMO) contributions allows us to determine that the interaction involving the nitrogen lone pair (LPN) is the main reason for the larger 5JHF compared to 3JHF. Our analysis indicates that delocalization of LPN has a positive contribution to the long-range coupling, while a negative one is observed for 3JHF.

AB - The long-range scalar coupling constant between proton and fluorine nuclei, 5JHF, is observed to be larger than 3JHF in the pyrimidinyl moiety of voriconazole. A set of smaller molecules is chosen (fluorobenzene, N-methyl-2-fluoropyridine, N-methyl-3-fluoropyridine, 3-fluoropyridine, 5-pyrimidine, and 2-fluoropyridine) to evaluate the influence of the nitrogen atom in the experimental JHF values. Spectral aliased pure shift heteronuclear single quantum coherence spectroscopy (SAPS-HSQC) is applied to determine the relative sign between the JCF and JHF scalar couplings. Theoretical calculations show that the 3JHF and 5JHF coupling constants can be described mainly by a Fermi contact (FC) transmission mechanism. A decomposition analysis of JHF in terms of localized molecular orbital (LMO) contributions allows us to determine that the interaction involving the nitrogen lone pair (LPN) is the main reason for the larger 5JHF compared to 3JHF. Our analysis indicates that delocalization of LPN has a positive contribution to the long-range coupling, while a negative one is observed for 3JHF.

KW - coupling constants

KW - fluorinated compounds

KW - NMR

KW - orbital decomposition analysis

KW - pyrimidinyl moiety

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DO - 10.1002/cphc.201800073

M3 - Artículo (Contribución a Revista)

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SN - 1439-4235

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JO - ChemPhysChem

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ER -

The Antagonist Effect of Nitrogen Lone Pair: ³J_HF versus ⁵J_HF

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