meso-Oxoisocorroles: Tunable Antiaromaticity by Metalation and Coordination of Lewis Acids as Well as Aromaticity Reversal in the Triplet Excited State

Kento Ueta; Jinseok Kim; Shota Ooi; Juwon Oh; Juhyang Shin; Akito Nakai; Manho Lim; Takayuki Tanaka; Dongho Kim; Atsuhiro Osuka

doi:10.1021/jacs.1c00476

meso-Oxoisocorroles: Tunable Antiaromaticity by Metalation and Coordination of Lewis Acids as Well as Aromaticity Reversal in the Triplet Excited State

J Am Chem Soc. 2021 Jun 2;143(21):7958-7967. doi: 10.1021/jacs.1c00476. Epub 2021 May 19.

Authors

Kento Ueta¹, Jinseok Kim², Shota Ooi¹, Juwon Oh³, Juhyang Shin⁴, Akito Nakai¹, Manho Lim⁴, Takayuki Tanaka¹, Dongho Kim², Atsuhiro Osuka¹

Affiliations

¹ Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
² Spectroscopy Laboratory for Functional π-Electronic Systems and Department of Chemistry, Yonsei University, Seoul 03722, Korea.
³ Department of Chemistry, Soonchunhyang University, Asan-si 31538, Korea.
⁴ Department of Chemistry and Chemistry Institute for Functional Materials, Pusan National University, Busan 46241, Korea.

PMID: 34009968
DOI: 10.1021/jacs.1c00476

Abstract

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.