Energy Aspects of Thermal Molecular Switching: Molecular Thermal Hysteresis of Helicene Oligomers

Shigeno, Masanori; Kushida, Yo; Yamaguchi, Masahiko

doi:10.1002/cphc.201500210

Cited by 32 publications

(56 citation statements)

References 83 publications

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“…The sharp peak in dissolution similar to melting is also notable. The large Δ H /Δ S and sharp peak in the dissolution are consistent with the sharp thermoresponse, which is due to a large structural change. The strong intermolecular van der Waals interactions between the methylene groups stabilize the extended structure in the solid state; a large entropic gain Δ S makes the globular structure thermodynamically favorable in solution.…”

Section: Resultssupporting

confidence: 67%

“…During the solid–liquid transition, a large change occurs in the shape of the extremely long polymethylene molecule from an extended structure in the solid state to a globular structure in solution. Substantial change of free energy, Δ G =Δ H − T Δ S , from competition of the large enthalpic loss Δ H and large entropic gain Δ S results in a sharp thermoresponse . The discussions of the solid‐liquid phase transition can be applied to the dissolution phenomenon in solution,, and a notable thermal property, namely, the sharp increase in solubility for a small temperature increase, can appear, which has not been previously examined.…”

Section: Introductionmentioning

confidence: 99%

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Synthesis of 1,128‐Octacosahectanediol and Its Sharp Thermoresponse in Solution with Concomitant Structural Change

et al. 2017

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1,128-Octacosahectanediol, which has an extremely long polymethylene chain, was synthesized. The heptaene C 128 intermediate with both ends silylated was synthesized by the sequence of the Wittig reaction and acetal deprotection in a two-directional manner. The unsaturated compound was converted to a saturated disilyl ether by homogeneous hydrogenation under toluene reflux, and was subsequently desilylated under THF/toluene/12 M HCl refluxing conditions to yield a C 128 diol. High-temperature conditions were employed to dissolve the substrates, and cooling liberated the products, which were isolated by filtration. 1,128-Octacosahectanediol showed a sharp increase in solubility in organic solvents with temperature changes of 10 K along with thermal hysteresis, which was ascribed to the concomitant structural change. The extended structure in the solid state was converted to a globular structure in solution, which involved large enthalpic loss and entropic gain.

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Section: Resultssupporting

confidence: 67%

Section: Introductionmentioning

confidence: 99%

Synthesis of 1,128‐Octacosahectanediol and Its Sharp Thermoresponse in Solution with Concomitant Structural Change

et al. 2017

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“…As noted in section 2, when ¦H and ¦S are the same signs and their absolute values are large, the relative thermodynamic stability of A and B can invert. 6,7 In reversible nonequilibrium-to-equilibrium chemical reactions with temperature changes during the reaction, macroscopic multiplepaths are enhanced, and the complexity drastically increases compared to the irreversible chemical reactions, which is the subject of this article. Consider an irreversible nonequilibrium-to-equilibrium chemical reaction with temperature change from a metastable state at T 1 to a chemical equilibrium at T 2 .…”

Section: Reversible Nonequilibrium-to-equilibrium Chemical Reactionsmentioning

confidence: 99%

Equilibrum and Nonequilibrium Chemical Reactions of Helicene Oligomers in the Noncovalent Bond Formation

Yamaguchi¹,

Arisawa²,

Shigeno³

et al. 2016

Bulletin of the Chemical Society of Japan

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Chemical reactions involving noncovalent bond formation are discussed with regard to the equilibrium and nonequilibrium states: An equilibrium-to-equilibirum chemical reaction involves change of equilibrium states by changing the environment; a nonequilibrium-to-equilibrium reaction involves change of metastable state to equilibrium. Complex nature of the chemical reactions, especially in the latter, is shown in terms of the multiple-path nature in the microscopic molecular structure changes and macroscopic concentration changes. Irreversible and reversible nonequilibrium-to-equilibrium chemical reactions are also compared in terms of the multiple-path. Helicene oligomers, which reversibly form double-helix and random-coil by temperature changes, are discussed with regard to the reversible nonequilibrium-to-equilibrium chemical reaction with self-catalysis, where notable chemical phenomena appear under nonequilibrium conditions.

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“…For example, states B and C occur only during cooling from state A but not by directly heating state D, because states B and C are formed by departure from equilibrium state A (Fig. 23b) (76,77). Because molecular events are considered to be reversible (microscopic reversibility) under equilibrium (80), the generation of the molecular memory effect at the molecular level is unusual.…”

Section: Sulfonamidohelicene Oligomersmentioning

confidence: 96%

“…Molecular thermal hysteresis can be used to develop a function to count the numbers 1 and 2 by molecules (77,78) high temperature were cooled, they remained in this state in the first cooling; molecules in the helix-dimer state were formed in the second cooling (Fig. 25).…”

Section: Sulfonamidohelicene Oligomersmentioning

confidence: 99%

Structure and Property Diversity of Chiral Helicene Oligomers

Saito

Shigeno

Yamaguchi

2015

Encyclopedia of Polymer Science and Technology

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alkylthio, and perfluoroalkyl groups. In addition, cyclization of helicene oligomers provides another method of obtaining diversity.A notable aspect in the diversity of helicene oligomers is that they can be connected to provide multidomain oligomers (Fig. 4). When two helicene oligomers are connected, they are referred to herein as homo-bidomain oligomers. Cyclic homo-bidomain oligomers are also conceivable. Hetero-multidomain oligomers can be obtained by connecting different structures of oligomers. Such manipulations provide a large diversity of structures.Because helicene can generate characteristic π−π interactions, helicene oligomers often form bimolecular, trimolecular, tetramolecular, and polymolecular aggregates in which homoaggregation and heteroaggregation can also occur. Such aggregates self-assemble to form fibrils, vesicles, liquid crystals, and surface monolayers. These noncovalent bonding interactions provide diversity of the structure of helicene oligmers. Diverse Properties of Helicene OligomersStructural diversity is directly related to diversity of properties, and the properties of a helicene oligomer can be varied by structural modifications. In addition, multidomain oligomers can be designed, in which properties A and B of each domain can be combined. Such compounds exhibit property A + B or even another property C, a result regarded as the "synthesis of a property or function." Aggregation and self-assembly of helicene oligomers further increase property diversity, which covers materials with a broad range of sizes from subnanometersized molecules through nano-and micrometer-sized molecular aggregates and molecular self-assemblies to macroscopic bulk materials. Helicene oligomers are sensitive to changes in the environment such as temperature, solvent, and concentration. Different properties appear in dilute solution, in concentrated Amidohelicene oligomers: (a) acylcic oligomers (P)-1 (n = 1−9) with dianiline spacer, cyclic oligomers (P)-2 (n = 1−10) with dianiline spacer, (b) acyclic oligomers (P)-3 (n = 1−9) with m-phenylene spacer, and acyclic reverse oligomers (P)-4 (n = 1−4). (c) Schematic representation of reversible change between helix dimer and random coils of (P)-3 and (P)-4. solution, in the crystalline state, in the amorphous state, on the solid surface, at the solid-liquid interface, in fiber assemblies, in liquid crystals, and in gels. Dynamic properties of helicene oligomers are also interesting, and structural changes are largely affected by the environment, providing a stimulus response or possible molecular switching materials. It is also noteworthy that the process of a structure change can produce unusual transient phenomena. Amidohelicene OligomersStudies on helicene oligomers were initiated with amide derivatives (Fig. 5a, top), in which the spacer has a bent shape and includes both hydrogen bonding donor and acceptor moieties (24). (P)-5,8-Helicenedicarboxylate was reacted with bis(2,6-dimethylanilino)cyclohexane to give a series of acyclic helicene oligomers 1 up t...

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Energy Aspects of Thermal Molecular Switching: Molecular Thermal Hysteresis of Helicene Oligomers

Cited by 32 publications

References 83 publications

Synthesis of 1,128‐Octacosahectanediol and Its Sharp Thermoresponse in Solution with Concomitant Structural Change

Synthesis of 1,128‐Octacosahectanediol and Its Sharp Thermoresponse in Solution with Concomitant Structural Change

Equilibrum and Nonequilibrium Chemical Reactions of Helicene Oligomers in the Noncovalent Bond Formation

Structure and Property Diversity of Chiral Helicene Oligomers

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