Jiao Yang, Đorđević Luka, Mao Haochuan, Young Ryan M, Jaynes Tyler, Chen Hongliang, Qiu Yunyan, Cai Kang, Zhang Long, Chen Xiao-Yang, Feng Yuanning, Wasielewski Michael R, Stupp Samuel I, Stoddart J Fraser
Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States.
Center for Bio-inspired Energy Science, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States.
J Am Chem Soc. 2021 Jun 2;143(21):8000-8010. doi: 10.1021/jacs.1c01493. Epub 2021 May 24.
Colored charge-transfer complexes can be formed by the association between electron-rich donor and electron-deficient acceptor molecules, bringing about the narrowing of HOMO-LUMO energy gaps so that they become capable of harnessing visible light. In an effort to facilitate the use of these widespread, but nonetheless weak, interactions for visible light photocatalysis, it is important to render the interactions strong and robust. Herein, we employ a well-known donor-acceptor [2]catenane-formed by the mechanical interlocking of cyclobis(paraquat--phenylene) and 1,5-dinaphtho[38]crown-10-in which the charge-transfer interactions between two 4,4'-bipyridinium and two 1,5-dioxynaphthalene units are enhanced by mechanical bonding, leading to increased absorption of visible light, even at low concentrations in solution. As a result, since this [2]catenane can generate persistent bipyridinium radical cations under continuous visible-light irradiation without the need for additional photosensitizers, it can display good catalytic activity in both photo-reductions and -oxidations, as demonstrated by hydrogen production-in the presence of platinum nanoparticles-and aerobic oxidation of organic sulfides, such as l-methionine, respectively. This research, which highlights the usefulness of nanoconfinement present in mechanically interlocked molecules for the reinforcement of weak interactions, can not only expand the potential of charge-transfer interactions in solar energy conversion and synthetic photocatalysis but also open up new possibilities for the development of active artificial molecular shuttles, switches, and machines.
富电子供体分子与缺电子受体分子之间可以形成有色电荷转移络合物，使最高占据分子轨道（HOMO）与最低未占分子轨道（LUMO）之间的能隙变窄，从而使其能够利用可见光。为了便于利用这些广泛存在但却较弱的相互作用进行可见光光催化，增强这些相互作用并使其稳定牢固很重要。在此，我们使用一种著名的供体-受体[2]轮烷，它由环双（百草枯-对亚苯基）和1,5-二萘并[38]冠-10通过机械互锁形成，其中两个4,4'-联吡啶鎓单元与两个1,5-二氧萘单元之间的电荷转移相互作用通过机械键合得到增强，即使在溶液中浓度较低时，也能增加对可见光的吸收。因此，由于这种[2]轮烷在连续可见光照射下无需额外的光敏剂就能产生持久的联吡啶鎓自由基阳离子，它在光还原和光氧化反应中均能表现出良好的催化活性，分别如在铂纳米颗粒存在下制氢以及对有机硫化物（如L-甲硫氨酸）的有氧氧化所证明的那样。这项研究突出了机械互锁分子中纳米限域对增强弱相互作用的有用性，不仅可以拓展电荷转移相互作用在太阳能转换和合成光催化方面 的潜力，还为开发活性人工分子穿梭体、开关和机器开辟了新的可能性。
