Design of Viologen-Based Liquid Crystals Exhibiting Bicontinuous Cubic Phases and Their Redox-Active Behavior

Kobayashi, Tetsuo; Ichikawa, Takahiro

doi:10.3390/ma10111243

Cited by 11 publications

(8 citation statements)

References 30 publications

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“…As anion species, tetrafluoroborate (BF 4 ), trifluoromethanesulfonate (Tf), and bis(trifluoromethane)sulfonimide (Tf 2 N) have been selected because they are known as useful anions for designing ionic liquids with a low glass transition temperature (T g ) [32]. As a cation part, a pyridinium cation has been employed since there have been several reports on the exhibition of Cub bi phases for pyridinium-based amphiphiles [33][34][35][36][37]. As a linker, we have selected a hexyl chain according to several researches on gemini-type amphiphiles [26][27][28][29][30][31].…”

Section: Resultsmentioning

confidence: 99%

Design of Ionic Liquid Crystals Forming Normal-Type Bicontinuous Cubic Phases with a 3D Continuous Ion Conductive Pathway

et al. 2019

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We have prepared a series of pyridinium-based gemini amphiphiles. They exhibit thermotropic liquid–crystalline behavior depending on their alkyl chain lengths and anion species. By adjusting the alkyl chain lengths and selecting suitable anions, we have obtained an ionic amphiphile that exhibits a normal-type bicontinuous cubic phase from 38 °C to 12 °C on cooling from an isotropic phase. In the bicontinuous cubic liquid–crystalline assembly, the pyridinium-based ionic parts align along a gyroid minimal surface forming a 3D continuous ionic domain while their ionophobic alkyl chains form 3D branched nanochannel networks. This ionic compound can form homogeneous mixtures with a lithium salt and the resultant mixtures keep the ability to form normal-type bicontinuous cubic phases. Ion conduction measurements have been performed for the mixtures on cooling. It has been revealed that the formation of the 3D branched ionophobic nanochannels does not disturb the ion conduction behavior in the ionic domain while it results in the conversion of the state of the mixtures from fluidic liquids to quasi-solids, namely highly viscous liquid crystals. Although the ionic conductivity of the mixtures is in the order of 10–7 S cm–1 at 40 °C, which is far lower than the values for practical use, the present material design has a potential to pave the way for developing advanced solid electrolytes consisting of two task-specific nanosegregated domains: One is an ionic liquid nano-domain with a 3D continuity for high ionic conductivity and the other is ionophobic nanochannel network domains for high mechanical strength.

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Section: Resultsmentioning

confidence: 99%

Design of Ionic Liquid Crystals Forming Normal-Type Bicontinuous Cubic Phases with a 3D Continuous Ion Conductive Pathway

et al. 2019

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“…Usually, ILCs are composed of an organic cation and an inorganic anion, as found in ionic liquids (ILs): besides the already mentioned imidazolium cations, several other systems have been investigated, such as guanidinium [19,20], pyrrolidinium [21] and bipyridinium (viologens) [22][23][24][25][26][27][28]. In all cases, the key molecular feature which is necessary in order to have ionic liquid crystal behavior is a relatively long alkyl chain attached to the ionic part.…”

Section: Introductionmentioning

confidence: 99%

Comparison of the Ionic Liquid Crystal Phase of [C12C1im][BF4] and [C12C1im]Cl by Atomistic MD Simulations

Saielli

2020

Crystals

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We present fully atomistic molecular dynamics (MD) simulations at 450 K of two ionic liquid crystals in the smectic phase: 1-dodecyl-3-methylimidazolium tetrafluoroborate ([C12C1im][BF4]) and 1-dodecyl-3-methylimidazolium chloride ([C12C1im]Cl). The two systems experimentally exhibit different ranges of thermal stability of the ionic smectic phase: The chloride salt has a more stable LC phase, between 270.3 K and 377.6 K, with a range of SmA of more than 107 K. In contrast, the tetrafluoroborate salt has a smectic phase between 299.6 K and 311.6 K, with a range of mesophase of just 12 K. The MD simulations show that the chloride system is stable in the smectic phase for the 5 ns of simulation, while the tetrafluoroborate salt melts into an isotropic ionic liquid, in qualitative agreement with the experiments. Comparison of the electrostatic and van der Waals energetic contributions enables one to rationalize the observed behavior as being due to the large size of the [BF4] anion: a larger size of the anion means a lower charge density, and therefore a weaker electrostatic interaction in the ionic layer.

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“…This effect was attributed to the aggregation occurring primarily in water-rich mixtures [102]. More recently, a multi-functional ILC material with aptitude to form bicontinuous cubic phases, based on a zwitterionic viologen was developed by Kobayashi and Ichikawa [103]. The amphiphilic zwitterionic viologen encompasses an ionic moiety and readily forms a 3D structure consisting of viologen layers.…”

Section: Ionic Liquid Crystalline Systems Involving Viologensmentioning

confidence: 99%

“…The amphiphilic zwitterionic viologen encompasses an ionic moiety and readily forms a 3D structure consisting of viologen layers. In their ionic state, the viologen units of the material are capable of undergoing one-electron reductions leading to a color change from colorless to purple (indicative of the formation of a radical cation (see also Figure 2), and this process can be triggered photochemically without disrupting the 3D structure [103].…”

Section: Ionic Liquid Crystalline Systems Involving Viologensmentioning

confidence: 99%

Mono- and Di-Quaternized 4,4′-Bipyridine Derivatives as Key Building Blocks for Medium- and Environment-Responsive Compounds and Materials

Papadakis

2019

Molecules

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Mono-and di-quaternized 4,4 -bipyridine derivatives constitute a family of heterocyclic compounds, which in recent years have been employed in numerous applications. These applications correspond to various disciplines of research and technology. In their majority, two key features of these 4,4 -bipyridine-based derivatives are exploited: their redox activity and their electrochromic aptitude. Contemporary materials and compounds encompassing these skeletons as building blocks are often characterized as multifunctional, as their presence often gives rise to interesting phenomena, e.g., various types of chromism. This research trend is acknowledged, and, in this review article, recent examples of multifunctional chromic materials/compounds of this class are presented. Emphasis is placed on solvent-/medium-and environment-responsive 4,4 -bipyridine derivatives. Two important classes of 4,4 -bipyridine-based products with solvatochromic and/or environment-responsive character are reviewed: viologens (i.e., N,N -disubstituted derivatives) and monoquats (i.e., monosubstituted 4,4 -bipyridine derivatives). The multifunctional nature of these derivatives is analyzed and structure-property relations are discussed in connection to the role of these derivatives in various novel applications.Molecules 2020, 25, 1 2 of 30 recent) underlining the high versatility of this class of compounds [9,10,[12][13][14][15]. Perhaps, the most reviewed subject regarding the viologens is their electrochromism [13,14,16]. Viologens are known to undergo one-electron reductions electrochemically ( Figure 2) yielding colorful radicals i.e., cations that are stable in the absence of O 2 . Yet, their chromism can also be triggered through various stimuli (including light, heat, solvents, presence of various chemical species, pressure, etc.). All these possibilities shape the very versatile "chromic character" of viologens and generally of 4,4 -bipyridine derivatives. Even though this "chromic character" has only recently started gaining more attention and there is an increasing number of research articles emphasizing on the alternative uses of 4,4 -bipyridine derivatives, there are no reviews in this growing area up until now. Such an attempt is presented in this review paper with an emphasis on medium-and environment-responsive compounds and materials based on 4,4 -bipyridine. Primary focus is placed on viologen-involving solvatochromic systems as well as materials and compounds of this class whose chromic behavior is dependent on various environment stimuli. Molecules 2018, 23, x 2 of 30 Figure 2. Schemes depicting (a) the electrochromic cycle (1) and (b) the photochromic cycle of paraquat (A, counter anion). Structure and Properties of Viologens The Strong Electron-Withdrawing Character of ViologensThe strong electron-withdrawing character of viologens has been widely exploited in numerous molecular architectures and materials. Viologens can undergo reversible one-electron reductions forming radical cations (Figure 2a), which are vividly colo...

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Design of Viologen-Based Liquid Crystals Exhibiting Bicontinuous Cubic Phases and Their Redox-Active Behavior

Cited by 11 publications

References 30 publications

Design of Ionic Liquid Crystals Forming Normal-Type Bicontinuous Cubic Phases with a 3D Continuous Ion Conductive Pathway

Design of Ionic Liquid Crystals Forming Normal-Type Bicontinuous Cubic Phases with a 3D Continuous Ion Conductive Pathway

Comparison of the Ionic Liquid Crystal Phase of [C12C1im][BF4] and [C12C1im]Cl by Atomistic MD Simulations

Mono- and Di-Quaternized 4,4′-Bipyridine Derivatives as Key Building Blocks for Medium- and Environment-Responsive Compounds and Materials

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