Dipartimento di Chimica, Università di Roma La Sapienza and ISB-CNR Sede Secondaria di Roma - Meccanismi di Reazione, P.le A. Moro 5, I-00185 Roma, Italy.
Dipartimento di Scienze e Tecnologie Chimiche, Università di Roma Tor Vergata, Via della Ricerca Scientifica, 00133 Roma, Italy.
J Org Chem. 2023 Apr 7;88(7):4379-4386. doi: 10.1021/acs.joc.2c02992. Epub 2023 Mar 16.
Temporal control of molecular motions is receiving increasing attention because it is central to the development of molecular switches and motors and nanoscopic materials with life-like properties. Inspired by previous studies, here, we report that acid can be used to temporally control the conformational freedom around the C-C bond connecting the two aromatic rings of the ditopic bases and . Consistent with NMR measurements and DFT calculations, before fuel addition, the conformational motion of the two aromatic rings of both and mainly consists of a large amplitude torsional oscillation spanning about 260° and passing for the conformation (the two nitrogen atoms at opposite sides). Immediately after the addition of , due to the protonation of one nitrogen and consequent formation of an N-H···N intramolecular hydrogen bond, the torsional oscillation in both H and H is not only restricted to a smaller range (about 100°) but explores the previously forbidden conformational space around the conformation (the two nitrogen atoms at the same side). However, the new state is an out-of-equilibrium state since decarboxylation of the conjugate base of takes place and, at the end of the process, the system reverts to the more conformationally mobile state.
时间控制分子运动受到越来越多的关注，因为它是发展分子开关和马达以及具有类似生命性质的纳米材料的核心。受先前研究的启发，在这里，我们报告酸可以用来暂时控制连接两个双位碱基的芳环的 C-C 键的构象自由度。与 NMR 测量和 DFT 计算一致，在燃料添加之前，两个芳环的构象运动主要由一个大振幅的扭转振荡组成，跨越约 260°，通过 构象（两侧的两个氮原子）。在 添加 后，由于一个氮原子的质子化和随之形成的 N-H···N 分子内氢键，H 和 H 的扭转振荡不仅受到更小范围（约 100°）的限制，而且还探索了 构象周围以前被禁止的构象空间（同一侧的两个氮原子）。然而，新的状态是一种非平衡状态，因为 的共轭碱发生脱羧反应，在过程结束时，系统恢复到更构象移动的状态。
