Transmission mechanisms of NMR long-range J(13C,19F) scalar couplings in 1-F,4-X-cubanes: A DFT and experimental study

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In order to get insight into transmission mechanisms of the title spin-spin coupling constants, nJ(C, F<inf>1</inf>) couplings (n=4, 5) were calculated at the DFT-B3LYP-6-311-G/EPR-III level, and 5J(Cα, F<inf>1</inf>) couplings were measured in 9 members of the series 1-F,4-X...

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Autor principal:	Contreras, Rubén Horacio
Publicado:	2006
Materias:	Atoms Couplings Coupling constants Halogen atoms Hyperconjugative interactions Scalar coupling Spin-spin coupling constants Substituent effect Three-fold symmetry Transmission mechanisms Fluorine
Acceso en línea:	https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00268976_v104_n4_p485_Contreras http://hdl.handle.net/20.500.12110/paper_00268976_v104_n4_p485_Contreras
Aporte de:	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires

id	paper:paper_00268976_v104_n4_p485_Contreras
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spelling	paper:paper_00268976_v104_n4_p485_Contreras2023-06-08T14:53:59Z Transmission mechanisms of NMR long-range J(13C,19F) scalar couplings in 1-F,4-X-cubanes: A DFT and experimental study Contreras, Rubén Horacio Atoms Couplings Coupling constants Halogen atoms Hyperconjugative interactions Scalar coupling Spin-spin coupling constants Substituent effect Three-fold symmetry Transmission mechanisms Fluorine In order to get insight into transmission mechanisms of the title spin-spin coupling constants, nJ(C, F<inf>1</inf>) couplings (n=4, 5) were calculated at the DFT-B3LYP-6-311-G/EPR-III level, and 5J(Cα, F<inf>1</inf>) couplings were measured in 9 members of the series 1-F,4-X-cubanes, where the α atom of the X group is a carbon atom. Hyperconjugative interactions were evaluated within the NBO approach, using the same level of theory as that employed for calculating spin-spin coupling constants. The unusual 4J(C<inf>4</inf>, F<inf>1</inf>) spin-spin coupling constants known in 1-F,4-Xcubanes are rationalized in this work as originating mainly due to two factors, namely, (i) the strong σ-hyperconjugative interactions involving as donors the cage C-C bonds; (ii) the particular arrangement of cage bonds not involving either the C<inf>1</inf> or the C<inf>4</inf> carbon atoms, C<inf>i</inf> and C<inf>j</inf>. For linear X substituents, the direction F<inf>1</inf>-C<inf>1</inf> ...C<inf>4</inf>-X is a three-fold symmetry axis and there are six C<inf>i</inf>-C<inf>j</inf> equivalent cage bonds, which are involved in (C<inf>i</inf>-C<inf>j</inf>)→(C<inf>1</inf>-F<inf>1</inf>)and (C<inf>i</inf>-C<inf>j</inf>)→(C<inf>4</inf>-X)hyperconjugative interactions. This means that coupling pathways involving such interactions are amplified six times, rendering the substrate very efficient for transmitting 'trans-cage' coupling constants. The large halogen substituent effects observed for 4J(C<inf>4</inf>, F<inf>1</inf>) spin-spin coupling constants in 1-F,4-X-cubanes (X = halogen atom) are rationalized in terms of interactions between σ-hyperconjugative (involving C-C bonds) and negative hyperconjugative interactions involving the halogen lone-pairs. © 2006 Taylor & Francis. Fil:Contreras, R.H. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. 2006 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00268976_v104_n4_p485_Contreras http://hdl.handle.net/20.500.12110/paper_00268976_v104_n4_p485_Contreras
institution	Universidad de Buenos Aires
institution_str	I-28
repository_str	R-134
collection	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic	Atoms Couplings Coupling constants Halogen atoms Hyperconjugative interactions Scalar coupling Spin-spin coupling constants Substituent effect Three-fold symmetry Transmission mechanisms Fluorine
spellingShingle	Atoms Couplings Coupling constants Halogen atoms Hyperconjugative interactions Scalar coupling Spin-spin coupling constants Substituent effect Three-fold symmetry Transmission mechanisms Fluorine Contreras, Rubén Horacio Transmission mechanisms of NMR long-range J(13C,19F) scalar couplings in 1-F,4-X-cubanes: A DFT and experimental study
topic_facet	Atoms Couplings Coupling constants Halogen atoms Hyperconjugative interactions Scalar coupling Spin-spin coupling constants Substituent effect Three-fold symmetry Transmission mechanisms Fluorine
description	In order to get insight into transmission mechanisms of the title spin-spin coupling constants, nJ(C, F<inf>1</inf>) couplings (n=4, 5) were calculated at the DFT-B3LYP-6-311-G/EPR-III level, and 5J(Cα, F<inf>1</inf>) couplings were measured in 9 members of the series 1-F,4-X-cubanes, where the α atom of the X group is a carbon atom. Hyperconjugative interactions were evaluated within the NBO approach, using the same level of theory as that employed for calculating spin-spin coupling constants. The unusual 4J(C<inf>4</inf>, F<inf>1</inf>) spin-spin coupling constants known in 1-F,4-Xcubanes are rationalized in this work as originating mainly due to two factors, namely, (i) the strong σ-hyperconjugative interactions involving as donors the cage C-C bonds; (ii) the particular arrangement of cage bonds not involving either the C<inf>1</inf> or the C<inf>4</inf> carbon atoms, C<inf>i</inf> and C<inf>j</inf>. For linear X substituents, the direction F<inf>1</inf>-C<inf>1</inf> ...C<inf>4</inf>-X is a three-fold symmetry axis and there are six C<inf>i</inf>-C<inf>j</inf> equivalent cage bonds, which are involved in (C<inf>i</inf>-C<inf>j</inf>)→(C<inf>1</inf>-F<inf>1</inf>)and (C<inf>i</inf>-C<inf>j</inf>)→(C<inf>4</inf>-X)hyperconjugative interactions. This means that coupling pathways involving such interactions are amplified six times, rendering the substrate very efficient for transmitting 'trans-cage' coupling constants. The large halogen substituent effects observed for 4J(C<inf>4</inf>, F<inf>1</inf>) spin-spin coupling constants in 1-F,4-X-cubanes (X = halogen atom) are rationalized in terms of interactions between σ-hyperconjugative (involving C-C bonds) and negative hyperconjugative interactions involving the halogen lone-pairs. © 2006 Taylor & Francis.
author	Contreras, Rubén Horacio
author_facet	Contreras, Rubén Horacio
author_sort	Contreras, Rubén Horacio
title	Transmission mechanisms of NMR long-range J(13C,19F) scalar couplings in 1-F,4-X-cubanes: A DFT and experimental study
title_short	Transmission mechanisms of NMR long-range J(13C,19F) scalar couplings in 1-F,4-X-cubanes: A DFT and experimental study
title_full	Transmission mechanisms of NMR long-range J(13C,19F) scalar couplings in 1-F,4-X-cubanes: A DFT and experimental study
title_fullStr	Transmission mechanisms of NMR long-range J(13C,19F) scalar couplings in 1-F,4-X-cubanes: A DFT and experimental study
title_full_unstemmed	Transmission mechanisms of NMR long-range J(13C,19F) scalar couplings in 1-F,4-X-cubanes: A DFT and experimental study
title_sort	transmission mechanisms of nmr long-range j(13c,19f) scalar couplings in 1-f,4-x-cubanes: a dft and experimental study
publishDate	2006
url	https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00268976_v104_n4_p485_Contreras http://hdl.handle.net/20.500.12110/paper_00268976_v104_n4_p485_Contreras
work_keys_str_mv	AT contrerasrubenhoracio transmissionmechanismsofnmrlongrangej13c19fscalarcouplingsin1f4xcubanesadftandexperimentalstudy
_version_	1768546481186275328

Transmission mechanisms of NMR long-range J(13C,19F) scalar couplings in 1-F,4-X-cubanes: A DFT and experimental study

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