Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan.
Chirality. 2020 Jun;32(6):824-832. doi: 10.1002/chir.23224. Epub 2020 Apr 6.
A 1:1 mixture of pseudoenantiomer ethynylhelicene (P)-pentamer and (M)-tetramer in toluene formed hetero-double-helix and their self-assembled gels. Kinetic analysis under isothermal conditions showed a complex nonlinear nature with regard to temperature changes. At 60°C, sigmoidal kinetics were observed, which disappeared after seeding with the self-assembled gels. These findings indicate the involvement of self-catalytic reaction I, in which a hetero-double-helix catalyzes the reaction to form a hetero-double-helix from random-coils. At 20°C, stairwise biphasic kinetics were observed, which disappeared after seeding. This phenomenon was explained by the involvement of two reactions with sigmoidal kinetics, namely, the formation of self-assembled gel I from hetero-double-helix by self-catalytic reaction II and the formation of self-assembled gel II by self-catalytic reaction III. Constant-rate temperature change experiments between 90 and 5°C showed nonsigmoidal thermal hysteresis in accordance with the involvement of sequential self-catalytic reactions with different reaction rates.
在甲苯中,1:1 比例的伪对映体乙炔基螺旋(P)-五聚体和(M)-四聚体形成杂双螺旋及其自组装凝胶。在等温条件下的动力学分析显示出与温度变化有关的复杂非线性性质。在 60°C 下,观察到了类正弦曲线动力学,在自组装凝胶接种后消失。这些发现表明涉及自催化反应 I,其中杂双螺旋催化反应,从无规线团形成杂双螺旋。在 20°C 下,观察到阶梯式两相动力学,在接种后消失。这种现象可以通过涉及两个具有类正弦曲线动力学的反应来解释,即自催化反应 II 从杂双螺旋形成自组装凝胶 I 以及自催化反应 III 从自组装凝胶 I 形成自组装凝胶 II。在 90 到 5°C 之间进行的恒速率温度变化实验显示出非类正弦曲线热滞后,这与具有不同反应速率的顺序自催化反应有关。