The corrole derivative meso-oxoisocorrole has been theoretically predicted to be antiaromatic, despite its formally cross conjugated electronic system. In this study, this prediction has been experimentally proven by the facile preparation of meso-oxoisocorrole via the oxidation of a meso free corrole with MnO2 and its comprehensive characterization using NMR, UV/vis absorption, FT-IR, and transient-absorption spectroscopy, cyclic voltammetry, and X-ray diffraction analysis. Furthermore, the free base meso-oxoisocorrole was metalated by treatment with Ni(acac)2, PdCl2(PhCN)2, and Zn(OAc)2 to give the corresponding metal complexes. These complexes are more strongly antiaromatic, and their degree of paratropicity depends on their planarity. Thus, fine tuning of their antiaromaticity was achieved with concomitant modulation of their HOMO-LUMO gaps. In the presence of tris(pentafluorophenyl)borane, their antiaromaticity is significantly enhanced due to the elongation of the C═O bond, which promotes the polarized C+-O- resonance state. Furthermore, a distinct frequency shift of the C═O vibrational mode in the triplet state was observed in the time-resolved IR spectra in accordance with the Baird rule, which indicates aromaticity reversal in the excited state.
|Number of pages||10|
|Journal||Journal of the American Chemical Society|
|Publication status||Published - 2021 Jun 2|
Bibliographical noteFunding Information:
The work was supported by Grants-in-Aid from the JSPS KAKENHI (JP18K14199, JP18H03910, and JP20K05463). K.U., S.O., and A.N. gratefully acknowledge JSPS Research Fellowships for Young Scientists. T.T. thanks the Asahi Glass Foundation for financial support. The works at Yonsei University and Pusan National University were supported by the National Research Foundation of Korea (NRF) grants funded by the Korean government (MSIT) (Nos. 2020R1A5A1019141 and NRF-2020R1A2B5B01001934).
© 2021 American Chemical Society.
All Science Journal Classification (ASJC) codes
- Colloid and Surface Chemistry