Inter-enantiomer conversion dynamics and Johari–Goldstein relaxation of benzophenones

We employ temperature- and pressure-dependent dielectric spectroscopy, as well as differential scanning calorimetry, to characterize benzophenone and the singly-substituted ortho-bromobenzophenone derivative in the liquid and glass states, and analyze the results in terms of the molecular conformati...

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Detalles Bibliográficos
Autores: Romanini, Michela|||0000-0002-1685-855X, Macovez, Roberto|||0000-0001-5026-9372, Tamarit Mur, José Luis|||0000-0002-7965-0000
Tipo de recurso: artículo
Fecha de publicación:2021
País:España
Institución:Universitat Politècnica de Catalunya (UPC)
Repositorio:UPCommons. Portal del coneixement obert de la UPC
Idioma:inglés
OAI Identifier:oai:upcommons.upc.edu:2117/360015
Acceso en línea:https://hdl.handle.net/2117/360015
https://dx.doi.org/10.1038/s41598-021-99606-0
Access Level:acceso abierto
Palabra clave:Crystals
Cristalls
Àrees temàtiques de la UPC::Física
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spelling Inter-enantiomer conversion dynamics and Johari–Goldstein relaxation of benzophenonesRomanini, Michela|||0000-0002-1685-855XMacovez, Roberto|||0000-0001-5026-9372Tamarit Mur, José Luis|||0000-0002-7965-0000CrystalsCristallsÀrees temàtiques de la UPC::FísicaWe employ temperature- and pressure-dependent dielectric spectroscopy, as well as differential scanning calorimetry, to characterize benzophenone and the singly-substituted ortho-bromobenzophenone derivative in the liquid and glass states, and analyze the results in terms of the molecular conformations reported for these molecules. Despite the significantly higher mass of the brominated derivative, its dynamic and calorimetric glass transition temperatures are only ten degrees higher than those of benzophenone. The kinetic fragility index of the halogenated molecule is lower than that of the parent compound, and is found to decrease with increasing pressure. By a detailed analysis of the dielectric loss spectra, we provide evidence for the existence of a Johari–Goldstein (JG) relaxation in both compounds, thus settling the controversy concerning the possible lack of a JG process in benzophenone and confirming the universality of this dielectric loss feature in molecular glass-formers. Both compounds also display an intramolecular relaxation, whose characteristic timescale appears to be correlated with that of the cooperative structural relaxation associated with the glass transition. The limited molecular flexibility of ortho-bromobenzophenone allows identifying the intramolecular relaxation as the inter-enantiomeric conversion between two isoenergetic conformers of opposite chirality, which only differ in the sign of the angle between the brominated aryl ring and the coplanar phenyl-ketone subunit. The observation by dielectric spectroscopy of a similar relaxation also in liquid benzophenone indicates that the inter-enantiomer conversion between the two isoenergetic helicoidal ground-state conformers of opposite chirality occurs via a transition state characterized by a coplanar phenyl-ketone moiety.Peer ReviewedNature20212021-10-1220222022-01-19journal articlehttp://purl.org/coar/resource_type/c_6501VoRhttp://purl.org/coar/version/c_970fb48d4fbd8a85info:eu-repo/semantics/articleapplication/pdfhttps://hdl.handle.net/2117/360015https://dx.doi.org/10.1038/s41598-021-99606-0reponame:UPCommons. Portal del coneixement obert de la UPCinstname:Universitat Politècnica de Catalunya (UPC)InglésengAgencia Estatal de Investigación http://doi.org/10.13039/501100011033 Plan Estatal de Investigación Científica y Técnica y de Innovación 2013-2016 FIS2017-82625-P VIDRIOS ORGANICOS Y METALICOS: DINAMICA, RECRISTALIZACION Y PROPIEDADES VIBRACIONALESopen accesshttp://purl.org/coar/access_right/c_abf2Attribution-NonCommercial-NoDerivs 3.0 Spainhttp://creativecommons.org/licenses/by-nc-nd/3.0/es/info:eu-repo/semantics/openAccessoai:upcommons.upc.edu:2117/3600152026-05-27T15:37:01Z
dc.title.none.fl_str_mv Inter-enantiomer conversion dynamics and Johari–Goldstein relaxation of benzophenones
title Inter-enantiomer conversion dynamics and Johari–Goldstein relaxation of benzophenones
spellingShingle Inter-enantiomer conversion dynamics and Johari–Goldstein relaxation of benzophenones
Romanini, Michela|||0000-0002-1685-855X
Crystals
Cristalls
Àrees temàtiques de la UPC::Física
title_short Inter-enantiomer conversion dynamics and Johari–Goldstein relaxation of benzophenones
title_full Inter-enantiomer conversion dynamics and Johari–Goldstein relaxation of benzophenones
title_fullStr Inter-enantiomer conversion dynamics and Johari–Goldstein relaxation of benzophenones
title_full_unstemmed Inter-enantiomer conversion dynamics and Johari–Goldstein relaxation of benzophenones
title_sort Inter-enantiomer conversion dynamics and Johari–Goldstein relaxation of benzophenones
dc.creator.none.fl_str_mv Romanini, Michela|||0000-0002-1685-855X
Macovez, Roberto|||0000-0001-5026-9372
Tamarit Mur, José Luis|||0000-0002-7965-0000
author Romanini, Michela|||0000-0002-1685-855X
author_facet Romanini, Michela|||0000-0002-1685-855X
Macovez, Roberto|||0000-0001-5026-9372
Tamarit Mur, José Luis|||0000-0002-7965-0000
author_role author
author2 Macovez, Roberto|||0000-0001-5026-9372
Tamarit Mur, José Luis|||0000-0002-7965-0000
author2_role author
author
dc.subject.none.fl_str_mv Crystals
Cristalls
Àrees temàtiques de la UPC::Física
topic Crystals
Cristalls
Àrees temàtiques de la UPC::Física
description We employ temperature- and pressure-dependent dielectric spectroscopy, as well as differential scanning calorimetry, to characterize benzophenone and the singly-substituted ortho-bromobenzophenone derivative in the liquid and glass states, and analyze the results in terms of the molecular conformations reported for these molecules. Despite the significantly higher mass of the brominated derivative, its dynamic and calorimetric glass transition temperatures are only ten degrees higher than those of benzophenone. The kinetic fragility index of the halogenated molecule is lower than that of the parent compound, and is found to decrease with increasing pressure. By a detailed analysis of the dielectric loss spectra, we provide evidence for the existence of a Johari–Goldstein (JG) relaxation in both compounds, thus settling the controversy concerning the possible lack of a JG process in benzophenone and confirming the universality of this dielectric loss feature in molecular glass-formers. Both compounds also display an intramolecular relaxation, whose characteristic timescale appears to be correlated with that of the cooperative structural relaxation associated with the glass transition. The limited molecular flexibility of ortho-bromobenzophenone allows identifying the intramolecular relaxation as the inter-enantiomeric conversion between two isoenergetic conformers of opposite chirality, which only differ in the sign of the angle between the brominated aryl ring and the coplanar phenyl-ketone subunit. The observation by dielectric spectroscopy of a similar relaxation also in liquid benzophenone indicates that the inter-enantiomer conversion between the two isoenergetic helicoidal ground-state conformers of opposite chirality occurs via a transition state characterized by a coplanar phenyl-ketone moiety.
publishDate 2021
dc.date.none.fl_str_mv 2021
2021-10-12
2022
2022-01-19
dc.type.none.fl_str_mv journal article
http://purl.org/coar/resource_type/c_6501
VoR
http://purl.org/coar/version/c_970fb48d4fbd8a85
dc.type.openaire.fl_str_mv info:eu-repo/semantics/article
format article
dc.identifier.none.fl_str_mv https://hdl.handle.net/2117/360015
https://dx.doi.org/10.1038/s41598-021-99606-0
url https://hdl.handle.net/2117/360015
https://dx.doi.org/10.1038/s41598-021-99606-0
dc.language.none.fl_str_mv Inglés
eng
language_invalid_str_mv Inglés
language eng
dc.relation.none.fl_str_mv Agencia Estatal de Investigación http://doi.org/10.13039/501100011033 Plan Estatal de Investigación Científica y Técnica y de Innovación 2013-2016 FIS2017-82625-P VIDRIOS ORGANICOS Y METALICOS: DINAMICA, RECRISTALIZACION Y PROPIEDADES VIBRACIONALES
dc.rights.none.fl_str_mv open access
http://purl.org/coar/access_right/c_abf2
Attribution-NonCommercial-NoDerivs 3.0 Spain
http://creativecommons.org/licenses/by-nc-nd/3.0/es/
dc.rights.openaire.fl_str_mv info:eu-repo/semantics/openAccess
rights_invalid_str_mv open access
http://purl.org/coar/access_right/c_abf2
Attribution-NonCommercial-NoDerivs 3.0 Spain
http://creativecommons.org/licenses/by-nc-nd/3.0/es/
eu_rights_str_mv openAccess
dc.format.none.fl_str_mv application/pdf
dc.publisher.none.fl_str_mv Nature
publisher.none.fl_str_mv Nature
dc.source.none.fl_str_mv reponame:UPCommons. Portal del coneixement obert de la UPC
instname:Universitat Politècnica de Catalunya (UPC)
instname_str Universitat Politècnica de Catalunya (UPC)
reponame_str UPCommons. Portal del coneixement obert de la UPC
collection UPCommons. Portal del coneixement obert de la UPC
repository.name.fl_str_mv
repository.mail.fl_str_mv
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