Proton-coupled electron transfer (PCET) is an important chemical and biological phenomenon. It is attractive as an on-off switching mechanism for redox-active synthetic systems but has not been extensively exploited for this purpose. Here we report a core-modified planar weakly antiaromatic/nonaromatic octaphyrin, namely, a octaphyrin(22.214.171.124.126.96.36.199) (1) derived from rigid naphthobipyrrole and dithienothiophene (DTT) precursors, that undergoes proton-coupled two-electron reduction to produce its aromatic congener in the presence of HCl and other hydrogen halides. Evidence for the production of a [4n + 1] π-electron intermediate radical state is seen in the presence of trifluoroacetic acid. Electrochemical analyses provide support for the notion that protonation causes a dramatic anodic shift in the reduction potentials of octaphyrin 1, thereby facilitating electron transfer from halide anions (viz. I-, Br-, and, Cl-). Electron-rich molecules, such as tetrathiafulvene (TTF), phenothiazine (PTZ), and catechol, were also found to induce PCET in the case of 1. Both the oxidized and two-electron reduced forms of 1 were characterized by X-ray diffraction analyses in the solid state and in solution via spectroscopic means.
Bibliographical noteFunding Information:
The authors are grateful to Shanghai University and the National Natural Science Foundation of China (grant 21672141 to Z.Z.) for financial support. The work in Austin was supported by the U.S. National Science Foundation (grant CHE-142004 to J.L.S.) and the Robert A. Welch Foundation (F-0018). The work at Yonsei was supported by the Global Research Laboratory (GRL) Program funded by the Ministry of Science, ICT and Future, Korea (2013K1A1A2A02050183).
© 2018 American Chemical Society.
All Science Journal Classification (ASJC) codes
- Colloid and Surface Chemistry