Switching between Aromatic and Antiaromatic 1,3-Phenylene-Strapped [26]- and [28]Hexaphyrins upon Passage to the Singlet Excited State

Young Mo Sung; Juwon Oh; Woojae Kim; Hirotaka Mori; Atsuhiro Osuka; Dongho Kim

doi:10.1021/jacs.5b04047

Switching between Aromatic and Antiaromatic 1,3-Phenylene-Strapped [26]- and [28]Hexaphyrins upon Passage to the Singlet Excited State

J Am Chem Soc. 2015 Sep 23;137(37):11856-9. doi: 10.1021/jacs.5b04047. Epub 2015 Sep 10.

Authors

Young Mo Sung¹, Juwon Oh¹, Woojae Kim¹, Hirotaka Mori², Atsuhiro Osuka², Dongho Kim¹

Affiliations

¹ Spectroscopy Laboratory for Functional π-Electronic Systems and Department of Chemistry, Yonsei University , Seoul 120-749, Korea.
² Department of Chemistry, Graduate School of Science, Kyoto University , Sakyo-ku, Kyoto 606-8502, Japan.

PMID: 26340352
DOI: 10.1021/jacs.5b04047

Abstract

We have demonstrated aromaticity reversal in the singlet excited states of internally 1,3-phenylene-strapped [26]- and [28]hexaphyrins (P26H and P28H). P26H displays a broad and reduced singlet-excited-state absorption spectrum, whereas P28H exhibits a sharp and intense singlet-excited-state absorption spectrum; both are in contrast to the ground-state absorption spectra, strongly indicating aromaticity reversal in the singlet excited state. Furthermore, magnetic and topological indices of aromaticity such as nucleus-independent chemical shift and harmonic oscillator model of aromaticity values for P26H and P28H also suggest that their singlet excited states become antiaromatic and aromatic, respectively.