Mesomorphic and electrooptical properties of viologens based on non-symmetric alkyl/polyfluoroalkyl functionalization and on an oxadiazolyl-extended bent core

Ivana Pibiri, Alessio Riccobono, Girolamo Casella, Andrea Pace, Amerigo Beneduci, Valerio Causin, Giacomo Saielli, Mauro Carraro, Giuseppe Chidichimo, Girolamo Casella, Giuseppina Anna Corrente

Risultato della ricerca: Article

6 Citazioni (Scopus)

Abstract

Two different sets of ionic liquid crystals based on bistriflimide salts of non-symmetrically substituted polyfluorinated bipyridinium (viologens) and bent symmetrically substituted dialkyl-oxadiazolyl-bipyridinium have been synthesized, in order to study the effect on the mesomorphic and electrooptical properties of the non-symmetric functionalization (alkyl chain and fluoroalkyl chains of different lengths) on the two pyridinium rings and additionally the effect of a bent conjugated spacer among the two pyridinium units of the viologen. POM and DSC characterization show that the synthesized salts have a mesomorphic and, in some cases, polymesomorphic behaviour in a wide thermal range, also encompassing room temperature. Some of the compounds exhibit an SmA phase in addition to more ordered smectic phases at lower temperature.The presence of a fluorinated chain on one side seems to generally increase the stability of the SmA phase of the ionic liquid crystal compared to alkylated analogues of viologens. Moreover, the insertion of the bent oxadiazolyl spacer between the two pyridinium units, has a significant effect on the mesophase behaviour leading to dendritic textures recalling that of banana phases. Electrochemical characterization by cyclic voltammetry shows that the presence of a fluorinated moiety causes an easier reduction compared to typical alkyl viologens while the oxadiazolyl-bipyridinium derivatives have more negativereduction potentials. Spectroelectrochemical experiments show that in contrast to classic viologens showing a typical electrochromic band of their radical cation, the oxadiazolyl insertion between the two pyridinium moieties hampers electrochromism due to absence of resonance coupling between the N redox centers. Interestingly, electrochromism of the polyfluorinated viologens, besides being observed in solution is observed in the ionic liquid crystal smectic phase of some of the salts of this series, upon radical cation formation the spectrum exhibits a further electrochromic band in the near infrared range which is not observed in solution.
Lingua originaleEnglish
pagine (da-a)7974-7983
Numero di pagine10
RivistaJOURNAL OF MATERIALS CHEMISTRY. C
Volume7
Stato di pubblicazionePublished - 2019

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Viologens
Ionic liquids
Electrochromism
Liquid crystals
Salts
Ionic Liquids
Liquid Crystals
Positive ions
Cyclic voltammetry
Cations
Textures
Infrared radiation
Derivatives
Temperature
Experiments

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Materials Chemistry

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Mesomorphic and electrooptical properties of viologens based on non-symmetric alkyl/polyfluoroalkyl functionalization and on an oxadiazolyl-extended bent core. / Pibiri, Ivana; Riccobono, Alessio; Casella, Girolamo; Pace, Andrea; Beneduci, Amerigo; Causin, Valerio; Saielli, Giacomo; Carraro, Mauro; Chidichimo, Giuseppe; Casella, Girolamo; Corrente, Giuseppina Anna.

In: JOURNAL OF MATERIALS CHEMISTRY. C, Vol. 7, 2019, pag. 7974-7983.

Risultato della ricerca: Article

Pibiri, Ivana ; Riccobono, Alessio ; Casella, Girolamo ; Pace, Andrea ; Beneduci, Amerigo ; Causin, Valerio ; Saielli, Giacomo ; Carraro, Mauro ; Chidichimo, Giuseppe ; Casella, Girolamo ; Corrente, Giuseppina Anna. / Mesomorphic and electrooptical properties of viologens based on non-symmetric alkyl/polyfluoroalkyl functionalization and on an oxadiazolyl-extended bent core. In: JOURNAL OF MATERIALS CHEMISTRY. C. 2019 ; Vol. 7. pagg. 7974-7983.
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title = "Mesomorphic and electrooptical properties of viologens based on non-symmetric alkyl/polyfluoroalkyl functionalization and on an oxadiazolyl-extended bent core",
abstract = "Two different sets of ionic liquid crystals based on bistriflimide salts of non-symmetrically substituted polyfluorinated bipyridinium (viologens) and bent symmetrically substituted dialkyl-oxadiazolyl-bipyridinium have been synthesized, in order to study the effect on the mesomorphic and electrooptical properties of the non-symmetric functionalization (alkyl chain and fluoroalkyl chains of different lengths) on the two pyridinium rings and additionally the effect of a bent conjugated spacer among the two pyridinium units of the viologen. POM and DSC characterization show that the synthesized salts have a mesomorphic and, in some cases, polymesomorphic behaviour in a wide thermal range, also encompassing room temperature. Some of the compounds exhibit an SmA phase in addition to more ordered smectic phases at lower temperature.The presence of a fluorinated chain on one side seems to generally increase the stability of the SmA phase of the ionic liquid crystal compared to alkylated analogues of viologens. Moreover, the insertion of the bent oxadiazolyl spacer between the two pyridinium units, has a significant effect on the mesophase behaviour leading to dendritic textures recalling that of banana phases. Electrochemical characterization by cyclic voltammetry shows that the presence of a fluorinated moiety causes an easier reduction compared to typical alkyl viologens while the oxadiazolyl-bipyridinium derivatives have more negativereduction potentials. Spectroelectrochemical experiments show that in contrast to classic viologens showing a typical electrochromic band of their radical cation, the oxadiazolyl insertion between the two pyridinium moieties hampers electrochromism due to absence of resonance coupling between the N redox centers. Interestingly, electrochromism of the polyfluorinated viologens, besides being observed in solution is observed in the ionic liquid crystal smectic phase of some of the salts of this series, upon radical cation formation the spectrum exhibits a further electrochromic band in the near infrared range which is not observed in solution.",
author = "Ivana Pibiri and Alessio Riccobono and Girolamo Casella and Andrea Pace and Amerigo Beneduci and Valerio Causin and Giacomo Saielli and Mauro Carraro and Giuseppe Chidichimo and Girolamo Casella and Corrente, {Giuseppina Anna}",
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T1 - Mesomorphic and electrooptical properties of viologens based on non-symmetric alkyl/polyfluoroalkyl functionalization and on an oxadiazolyl-extended bent core

AU - Pibiri, Ivana

AU - Riccobono, Alessio

AU - Casella, Girolamo

AU - Pace, Andrea

AU - Beneduci, Amerigo

AU - Causin, Valerio

AU - Saielli, Giacomo

AU - Carraro, Mauro

AU - Chidichimo, Giuseppe

AU - Casella, Girolamo

AU - Corrente, Giuseppina Anna

PY - 2019

Y1 - 2019

N2 - Two different sets of ionic liquid crystals based on bistriflimide salts of non-symmetrically substituted polyfluorinated bipyridinium (viologens) and bent symmetrically substituted dialkyl-oxadiazolyl-bipyridinium have been synthesized, in order to study the effect on the mesomorphic and electrooptical properties of the non-symmetric functionalization (alkyl chain and fluoroalkyl chains of different lengths) on the two pyridinium rings and additionally the effect of a bent conjugated spacer among the two pyridinium units of the viologen. POM and DSC characterization show that the synthesized salts have a mesomorphic and, in some cases, polymesomorphic behaviour in a wide thermal range, also encompassing room temperature. Some of the compounds exhibit an SmA phase in addition to more ordered smectic phases at lower temperature.The presence of a fluorinated chain on one side seems to generally increase the stability of the SmA phase of the ionic liquid crystal compared to alkylated analogues of viologens. Moreover, the insertion of the bent oxadiazolyl spacer between the two pyridinium units, has a significant effect on the mesophase behaviour leading to dendritic textures recalling that of banana phases. Electrochemical characterization by cyclic voltammetry shows that the presence of a fluorinated moiety causes an easier reduction compared to typical alkyl viologens while the oxadiazolyl-bipyridinium derivatives have more negativereduction potentials. Spectroelectrochemical experiments show that in contrast to classic viologens showing a typical electrochromic band of their radical cation, the oxadiazolyl insertion between the two pyridinium moieties hampers electrochromism due to absence of resonance coupling between the N redox centers. Interestingly, electrochromism of the polyfluorinated viologens, besides being observed in solution is observed in the ionic liquid crystal smectic phase of some of the salts of this series, upon radical cation formation the spectrum exhibits a further electrochromic band in the near infrared range which is not observed in solution.

AB - Two different sets of ionic liquid crystals based on bistriflimide salts of non-symmetrically substituted polyfluorinated bipyridinium (viologens) and bent symmetrically substituted dialkyl-oxadiazolyl-bipyridinium have been synthesized, in order to study the effect on the mesomorphic and electrooptical properties of the non-symmetric functionalization (alkyl chain and fluoroalkyl chains of different lengths) on the two pyridinium rings and additionally the effect of a bent conjugated spacer among the two pyridinium units of the viologen. POM and DSC characterization show that the synthesized salts have a mesomorphic and, in some cases, polymesomorphic behaviour in a wide thermal range, also encompassing room temperature. Some of the compounds exhibit an SmA phase in addition to more ordered smectic phases at lower temperature.The presence of a fluorinated chain on one side seems to generally increase the stability of the SmA phase of the ionic liquid crystal compared to alkylated analogues of viologens. Moreover, the insertion of the bent oxadiazolyl spacer between the two pyridinium units, has a significant effect on the mesophase behaviour leading to dendritic textures recalling that of banana phases. Electrochemical characterization by cyclic voltammetry shows that the presence of a fluorinated moiety causes an easier reduction compared to typical alkyl viologens while the oxadiazolyl-bipyridinium derivatives have more negativereduction potentials. Spectroelectrochemical experiments show that in contrast to classic viologens showing a typical electrochromic band of their radical cation, the oxadiazolyl insertion between the two pyridinium moieties hampers electrochromism due to absence of resonance coupling between the N redox centers. Interestingly, electrochromism of the polyfluorinated viologens, besides being observed in solution is observed in the ionic liquid crystal smectic phase of some of the salts of this series, upon radical cation formation the spectrum exhibits a further electrochromic band in the near infrared range which is not observed in solution.

UR - http://hdl.handle.net/10447/365605

UR - https://pubs.rsc.org/en/content/articlelanding/2019/TC/C9TC01697J#!divAbstract

M3 - Article

VL - 7

SP - 7974

EP - 7983

JO - JOURNAL OF MATERIALS CHEMISTRY. C

JF - JOURNAL OF MATERIALS CHEMISTRY. C

SN - 2050-7526

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