Sun Yonghui, Liu Lijuan, Jiang Linnan, Chen Yong, Zhang Hengyue, Xu Xiufang, Liu Yu
College of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, P. R. China.
J Am Chem Soc. 2023 Aug 2;145(30):16711-16717. doi: 10.1021/jacs.3c04430. Epub 2023 Jul 24.
Intelligent molecular machines that are driven by light, electricity, and temperature have attracted considerable interest in the fields of chemistry, materials, and biology. Herein, a unimolecular chiral stepping inversion molecular machine (SIMM) was constructed by a coupling reaction between dibromo pillar[5]arene and a tetrathiafulvalene (TTF) derivative (PT3 and PT5). Compared with the longer aliphatic linker PT5, PT3 with a shorter aliphatic linker shows chiral stepping inversion, achieving chiral inversion under a two-electron redox potential. Benefiting from the successive reversible two-electron redox potential of TTF, the self-exclusion and self-inclusion conformational transformations of SIMM can proceed in two steps under redox, leading to the chirality step inversion in the pillar[5]arene core. Electrochemical experiments and circular dichroism (CD) spectra show that the redox processes can cause SIMM CD signaling to reversibly switch. More importantly, as the oxidant Fe(ClO) was increased from 0.1 to 1 equiv, the CD spectral signal of SIMM disappeared at 1 equiv, and further addition of Fe(ClO) resulted in the CD signal reversed from positive to negative at 309 nm, indicating that the chirality was reversed after chemical oxidation and reached a negative maximum with the addition of 2 equiv Fe(ClO); thus, redox-triggered chiral stepping inversion was achieved. Furthermore, the chiral inversion can be restored to its original state after the addition of 2 equiv of reducing agent, sodium ascorbate. This work demonstrates unimolecular chiral stepping inversion, providing a new perspective on stimulus-responsive chirality in molecular machines.
由光、电和温度驱动的智能分子机器在化学、材料和生物学领域引起了广泛关注。在此，通过二溴柱[5]芳烃与四硫富瓦烯（TTF）衍生物（PT3和PT5）之间的偶联反应构建了一种单分子手性步进反转分子机器（SIMM）。与具有较长脂肪族连接基的PT5相比，具有较短脂肪族连接基的PT3表现出手性步进反转，在双电子氧化还原电位下实现手性反转。受益于TTF连续可逆的双电子氧化还原电位，SIMM的自排斥和自包结构象转变在氧化还原条件下可分两步进行，导致柱[5]芳烃核心中的手性步进反转。电化学实验和圆二色性（CD）光谱表明，氧化还原过程可使SIMM的CD信号可逆切换。更重要的是，随着氧化剂Fe(ClO)从0.1当量增加到1当量，SIMM的CD光谱信号在1当量时消失，进一步添加Fe(ClO)导致在309 nm处CD信号从正反转到负，表明化学氧化后手性反转，并在添加2当量Fe(ClO)时达到负最大值；因此，实现了氧化还原触发的手性步进反转。此外，添加2当量的还原剂抗坏血酸钠后，手性反转可恢复到原始状态。这项工作展示了单分子手性步进反转，为分子机器中刺激响应手性提供了新的视角。
