Figure-eight thermal hysteresis of aminomethylenehelicene oligomers with terminal C<sub>16</sub> alkyl groups during hetero-double-helix formation

Sawato, Tsukasa; Iwamoto, Rina; Yamaguchi, Masahiko

doi:10.1039/c9sc06496f

Cited by 6 publications

(16 citation statements)

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“…A related system of (P)-tetramer (P)-1-C 16 with C 16 alkyl groups and (M)-pentamer (M)-2 (Figure 1c) exhibited a figure-eight stable thermal hysteresis, in which the hysteresis curve overlapped with the equilibrium curve at high temperatures and contained fully dissociated 2 A (Figure 1a, black lines and blue square). [7] In this work, we examined the properties of unstable thermal hysteresis under thermal triangle waves using (P)-1-C 16 /(M)-2. (P)-1-C 16 /(M)-2 exhibited relatively a simple behavior than (P)-1/(M)-3; therefore, it was considered a suitable system for the analysis of unstable thermal hysteresis.…”

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Unstable and Stable Thermal Hysteresis Under Thermal Triangle Waves

2021

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A 1 : 1 mixture of aminomethylenehelicene (P)-tetramer with C 16 alkyl groups (P)-1-C 16 and (M)-pentamer (M)-2 in fluorobenzene forms hetero-double-helices, and the processes of formation and dissociation exhibit thermal hysteresis on cooling and heating. When thermal triangle waves with repeated cooling and heating cycles are applied, unstable thermal hysteresis appears, which becomes a stable thermal hysteresis after sufficient numbers of cycles. The phenomenon of middle-range stable thermal hysteresis is observed in this case. Properties of unstable and stable thermal hysteresis are examined under various thermal triangle waves.

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Unstable and Stable Thermal Hysteresis Under Thermal Triangle Waves

2021

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“…This (Figure 26b), and thermal hysteresis (Figure 26c). [40,41] The involvement of the self-catalytic 2A(A) + C(A)-to-2C(A) reaction was also determined by sigmoidal kinetics under isothermal condition (Figure 27a) and seeding experiment by mixing 2A(A) and C(A) (Figure 27b). [40] Cooling of 2A(A) solution to 40°C at a rate of 1 K min À 1 provided a small amount of B(A), and cooling to 5°C at a rate of 0.067 K min À 1 provided C(A) (Figure 27c).…”

Section: Two Competitive Self-catalytic Reactions To Form Hetero-doubmentioning

confidence: 99%

“…[42] Figure-eight thermal hysteresis appeared, in which cooling and heating curves crossed (Figure 28c). [41]…”

Section: Two Competitive Self-catalytic Reactions To Form Hetero-doubmentioning

confidence: 99%

“…The difference between self-catalytic reactions and molecular self-assembly is derived from the nature of B-B: Rapid dissociation provides 2B; slow dissociation provides A-B-B and B-B-B-B… Self-catalytic phenomena may also be involved in molecular assembly by fragmentation, which increases the number of B-B-B-B… units. [40,41,42] with permission from the Royal Society of Chemistry. Figure 29.…”

Section: Hetero-double-helix Formation and Molecular Self-assemblymentioning

confidence: 99%

“…Green arrows are indications of self-catalytic reactions. Reproduced from Ref [40,41]. with permission from the Royal Society of Chemistry.…”

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Synthetic Chemical Systems Involving Self‐Catalytic Reactions of Helicene Oligomer Foldamers

Sawato

Yamaguchi

2020

ChemPlusChem

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Self‐catalysis is defined as catalysis by a product of a chemical reaction, that causes a significant increase in reaction rate in terms of the progress of the reaction. When a self‐catalytic reaction is involved in a reversible nonequilibrium‐to‐equilibrium chemical reaction, notable kinetic phenomena appear including sigmoidal kinetics, the seeding effect, thermal hysteresis, and chiral symmetry breaking. The nature of self‐catalytic reactions is characterized by microscopic mechanisms involving pathways of molecular structural changes and by macroscopic mechanisms involving molecular flux. Reversible self‐catalytic reactions, which exhibit notably high sensitivity to environmental changes, are also observed. In this Review, reversible self‐catalytic reactions of helicene oligomer foldamers during formation of homo‐ and hetero‐double‐helices are discussed, which exhibit the properties outlined above.

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Thermal Hysteresis Involving Reversible Self-Catalytic Reactions

Yamaguchi

2021

Acc. Chem. Res.

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Conspectus Hysteresis is ubiquitous in nature and biology. It appears in ferromagnetism, ferroelectrism, traffic congestion, river sedimentation, electronics, thermoresponses, cell division, differentiation, and apoptosis. Hysteresis phenomena are beyond equilibrium and involve nonlinear, bistable, time delay, and memory events, which are described in input/output profiles by different outputs during continuous decreases and increases in input intensity. Although hysteresis profiles in these phenomena appear similar, the mechanisms underlying them are complex, and their basic understanding is desired. In this Account, I describe thermal hysteresis caused by molecules dispersed in dilute solutions containing optically active helicene oligomers, which form homo- and heterodouble helices, the cooling and heating processes of which cause different structural changes with regard to their relative concentrations. Reversible self-catalytic reactions are involved in the formation of a double helix, which catalyzes its own formation. The reactions accelerate as they progress, in contrast to ordinary reactions, which exhibit monotonic retardation as they progress. Thermal hysteresis involving reversible self-catalytic reactions exhibits notable phenomena, when various cooling/heating inputs are applied during the reaction; these phenomena are shown herein with profiles of experimental results of Δε outputs obtained by circular dichroism (CD) plotted against temperature inputs. Thermal hysteresis is discussed in terms of (1) two states of the homodouble helix and a random coil involving one reversible self-catalytic reaction and (2) three states of enantiomeric heterodouble helices and a random coil involving two reversible self-catalytic reactions. Repeated cooling and heating processes provide the same stable thermal hysteresis loops, when the initial and final high-temperature states are under equilibrium, and nonloop and unstable thermal hysteresis appears when whole the systems are beyond equilibrium. Diverse thermal hysteresis loops are obtained under different temperature change conditions for different oligomers. The mechanism of thermal hysteresis involves different macroscopic mechanisms at a fixed temperature, when the relative concentrations of substrates/products and the reaction direction differ. Microscopic mechanisms, which are shown by energy diagrams, are fixed at a temperature irrespective of cooling or heating. A comparison of thermal hysteresis loops and equilibrium curves provides distances to the metastable states on the loops from equilibrium, and reactions occur from the metastable states toward equilibrium. Notable phenomena described herein include bistability, high sensitivity to small concentration changes, equilibrium crossing, three-state one-directional structural change caused by a single heating procedure, reaction shortcuts, the memory effect on thermal history, figure-eight thermal hysteresis, chemical oscillation, stable and unstable thermal hysteresis, double-helix formation only under ...

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Figure-eight thermal hysteresis of aminomethylenehelicene oligomers with terminal C₁₆ alkyl groups during hetero-double-helix formation

Abstract: 1 : 1 mixtures of aminomethylenehelicene (P)-tetramer and (M)-pentamer with terminal C16 alkyl groups in fluorobenzene showed structural changes between hetero-double-helices B and C and random-coils 2A.

Cited by 6 publications

References 42 publications

Unstable and Stable Thermal Hysteresis Under Thermal Triangle Waves

Unstable and Stable Thermal Hysteresis Under Thermal Triangle Waves

Synthetic Chemical Systems Involving Self‐Catalytic Reactions of Helicene Oligomer Foldamers

Thermal Hysteresis Involving Reversible Self-Catalytic Reactions

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Figure-eight thermal hysteresis of aminomethylenehelicene oligomers with terminal C16 alkyl groups during hetero-double-helix formation

Abstract: 1 : 1 mixtures of aminomethylenehelicene (P)-tetramer and (M)-pentamer with terminal C16 alkyl groups in fluorobenzene showed structural changes between hetero-double-helices B and C and random-coils 2A.

Cited by 6 publications

References 42 publications

Unstable and Stable Thermal Hysteresis Under Thermal Triangle Waves

Unstable and Stable Thermal Hysteresis Under Thermal Triangle Waves

Synthetic Chemical Systems Involving Self‐Catalytic Reactions of Helicene Oligomer Foldamers

Thermal Hysteresis Involving Reversible Self-Catalytic Reactions

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Figure-eight thermal hysteresis of aminomethylenehelicene oligomers with terminal C₁₆ alkyl groups during hetero-double-helix formation