title: Aromaticity Reversal in the Lowest Excited Triplet State of Archetypical Möbius Heteroannulenic Systems.
abstract: The aromaticity reversal in the lowest triplet state (T1 ) of a comparable set of Hückel/Möbius aromatic metalated expanded porphyrins was explored by optical spectroscopy and quantum calculations. In the absorption spectra, the T1 states of the Möbius aromatic species showed broad, weak, and ill-defined spectral features with small extinction coefficients, which is in line with typical antiaromatic expanded porphyrins. In combination with quantum calculations, these results indicate that the Möbius aromatic nature of the S0 state is reversed to Möbius antiaromaticity in the T1 state. This is the first experimental observation of aromaticity reversal in the T1 state of Möbius aromatic molecules.
authors.affiliation: Department of Chemistry, Spectroscopy Laboratory for Functional π-Electronic Systems, Yonsei University, Seoul, 120-749, Korea.
authors.forename: Juwon
authors.initials: J
authors.lastname: Oh
authors.affiliation: Department of Chemistry, Spectroscopy Laboratory for Functional π-Electronic Systems, Yonsei University, Seoul, 120-749, Korea.
authors.forename: Young Mo
authors.initials: YM
authors.lastname: Sung
authors.affiliation: Department of Chemistry, Spectroscopy Laboratory for Functional π-Electronic Systems, Yonsei University, Seoul, 120-749, Korea.
authors.forename: Woojae
authors.initials: W
authors.lastname: Kim
authors.affiliation: Department of Chemistry, Graduated School of Science, Kyoto University, Kyoto, 606-8502, Japan.
authors.forename: Shigeki
authors.initials: S
authors.lastname: Mori
authors.affiliation: Department of Chemistry, Graduated School of Science, Kyoto University, Kyoto, 606-8502, Japan. osuka@kuchem.kyoto-u.ac.jp.
authors.forename: Atsuhiro
authors.initials: A
authors.lastname: Osuka
authors.affiliation: Department of Chemistry, Spectroscopy Laboratory for Functional π-Electronic Systems, Yonsei University, Seoul, 120-749, Korea. dongho@yonsei.ac.kr.
authors.forename: Dongho
authors.initials: D
authors.lastname: Kim
keywords: Baird's rule; antiaromaticity; aromaticity; electronic structure; porphyrinoids