title: Stacked antiaromatic porphyrins.
abstract: Aromaticity is a key concept in organic chemistry. Even though this concept has already been theoretically extrapolated to three dimensions, it usually still remains restricted to planar molecules in organic chemistry textbooks. Stacking of antiaromatic π-systems has been proposed to induce three-dimensional aromaticity as a result of strong frontier orbital interactions. However, experimental evidence to support this prediction still remains elusive so far. Here we report that close stacking of antiaromatic porphyrins diminishes their inherent antiaromaticity in the solid state as well as in solution. The antiaromatic stacking furthermore allows a delocalization of the π-electrons, which enhances the two-photon absorption cross-section values of the antiaromatic porphyrins. This feature enables the dynamic switching of the non-linear optical properties by controlling the arrangement of antiaromatic π-systems on the basis of intermolecular orbital interactions.
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Nozawa
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan.
authors.forename: Hiroko
authors.initials: H
authors.lastname: Tanaka
authors.affiliation: Department of Chemistry, Yonsei University, Seoul 120-749, Korea.
authors.forename: Won-Young
authors.initials: WY
authors.lastname: Cha
authors.affiliation: Department of Chemistry, Yonsei University, Seoul 120-749, Korea.
authors.forename: Yongseok
authors.initials: Y
authors.lastname: Hong
authors.affiliation: Department of Material and Life Science, Graduate School of Engineering, Osaka University, Osaka 565-0871, Japan.
authors.forename: Ichiro
authors.initials: I
authors.lastname: Hisaki
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Kyushu University, Fukuoka 819-0395, Japan.
authors.forename: Soji
authors.initials: S
authors.lastname: Shimizu
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan.
authors.forename: Ji-Young
authors.initials: JY
authors.lastname: Shin
authors.affiliation: Department of Chemistry, Advanced Materials Science and Engineering Center, and Institute for Energy Studies, Western Washington University, Bellingham, Washington 98225, USA.
authors.forename: Tim
authors.identifier: 0000-0003-1806-059X
authors.initials: T
authors.lastname: Kowalczyk
authors.affiliation: Department of Chemistry, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan.
authors.forename: Stephan
authors.identifier: 0000-0003-4995-4991
authors.initials: S
authors.lastname: Irle
authors.affiliation: Department of Chemistry, Yonsei University, Seoul 120-749, Korea.
authors.forename: Dongho
authors.initials: D
authors.lastname: Kim
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Nagoya University, Nagoya 464-8603, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Shinokubo