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The Extension of Baird's Rule to Twisted Heteroannulenes: Aromaticity Reversal of Singly and Doubly Twisted Molecular Systems in the Lowest Triplet State
Author(s) -
Hong Yongseok,
Oh Juwon,
Sung Young Mo,
Tanaka Yasuo,
Osuka Atsuhiro,
Kim Dongho
Publication year - 2017
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201611431
Subject(s) - antiaromaticity , aromaticity , chemistry , computational chemistry , crystallography , molecule , organic chemistry
We have investigated the aromaticity of singly twisted Möbius aromatic and doubly twisted Hückel antiaromatic bis(palladium(II)) [36]octaphyrins in the lowest triplet state (T 1 ) by spectroscopic measurements and quantum calculations. The T 1 state of the singly twisted Möbius [36]octaphyrin shows broad and weak absorption spectral features that are analogous to those of antiaromatic expanded porphyrins while the T 1 state of the doubly twisted Hückel [36]octaphyrin exhibits intense and distinct spectral features, indicating the aromatic nature. These results along with theoretical calculations support the hypothesis that the aromaticity is reversed in the T 1 state. Furthermore, we show that the degree of structural smoothness affects the aromaticity reversal in the T 1 state.