Unstable and Stable Thermal Hysteresis Under Thermal Triangle Waves

Arisawa, Mieko; Iwamoto, Rina; Yamaguchi, Masahiko

doi:10.1002/slct.202100089

Cited by 2 publications

(2 citation statements)

References 16 publications

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“…Recent work from the Yamaguchi laboratory ( 19 ) has explored how the spectra of slowly equilibrating, self-assembling systems respond to repeated heating and cooling cycles ( 36 ). Depending on the starting and ending temperatures and ramp rates, a rich diversity of shapes (TH loops) have been observed, providing qualitative information on the underlying assembly reactions.…”

Section: Resultsmentioning

confidence: 99%

Using transient equilibria (TREQ) to measure the thermodynamics of slowly assembling supramolecular systems

et al. 2022

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Supramolecular chemistry involves the noncovalent assembly of monomers into materials with unique properties and wide-ranging applications. Thermal analysis is a key analytical tool in this field, as it provides quantitative thermodynamic information on both the structural stability and nature of the underlying molecular interactions. However, there exist many supramolecular systems whose kinetics are so slow that the thermodynamic methods currently applied are unreliable or fail completely. We have developed a simple and rapid spectroscopic method for extracting accurate thermodynamic parameters from these systems. It is based on repeatedly raising and lowering the temperature during assembly and identifying the points of transient equilibrium as they are passed on the up- and down-scans. In a proof-of-principle application to the coassembly of polydeoxyadenosine (polyA) containing 15 adenosines and cyanuric acid (CA), we found that roughly 30% of the CA binding sites on the polyA chains were unoccupied, with implications for high-valence systems.

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Section: Resultsmentioning

confidence: 99%

Using transient equilibria (TREQ) to measure the thermodynamics of slowly assembling supramolecular systems

et al. 2022

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“…Unstable thermal hysteresis occurred in a mixture of ( M )- 1 and ( P )-hexamer ( P )- 3 , when repeated cooling/heating cycles were provided at a constant rate, which produced chemical oscillations with a 2-fold increase in Δε. , ( M )- 1 /( P )- 3 in toluene at 70 °C with fully dissociated A / A ′ (A) was cooled to −5 °C at a rate of 2.0 K min –1 , and the temperature was changed between 38 and −5 °C at the same rate. Different thermal hysteresis curves were obtained depending on the number of cycles, and Δε gradually increased with the number of cycles, which is unstable thermal hysteresis (Figure a).…”

Section: Thermal Hysteresis By Three-state Reversible Self-catalytic ...mentioning

confidence: 99%

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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Unstable and Stable Thermal Hysteresis Under Thermal Triangle Waves

Cited by 2 publications

References 16 publications

Using transient equilibria (TREQ) to measure the thermodynamics of slowly assembling supramolecular systems

Using transient equilibria (TREQ) to measure the thermodynamics of slowly assembling supramolecular systems

Thermal Hysteresis Involving Reversible Self-Catalytic Reactions

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