The Extension of Baird's Rule to Twisted Heteroannulenes: Aromaticity Reversal of Singly and Doubly Twisted Molecular Systems in the Lowest Triplet State.
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 (T1) by spectroscopic measurements and quantum calculations. The T1state 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 T1state 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 T1state. Furthermore, we show that the degree of structural smoothness affects the aromaticity reversal in the T1state.
Department of Chemistry, Spectroscopy Laboratory for Functional π-Electronic Systems, Yonsei University, Seoul, 120-749, Korea.
Yongseok
Y
Hong
Department of Chemistry, Spectroscopy Laboratory for Functional π-Electronic Systems, Yonsei University, Seoul, 120-749, Korea.
Juwon
J
Oh
Department of Chemistry, Spectroscopy Laboratory for Functional π-Electronic Systems, Yonsei University, Seoul, 120-749, Korea.
Young Mo
YM
Sung
Department of Chemistry, Graduated School of Science, Kyoto University, Kyoto, 606-8502, Japan.
Yasuo
Y
Tanaka
Department of Chemistry, Graduated School of Science, Kyoto University, Kyoto, 606-8502, Japan.
Atsuhiro
A
Osuka
Department of Chemistry, Spectroscopy Laboratory for Functional π-Electronic Systems, Yonsei University, Seoul, 120-749, Korea.
Dongho
D
Kim
Baird's rule; aromaticity; electronic structure; porphyrinoids; spectroscopy