Dibenzoarsepins: Planarization of 8π-Electron System in the Lowest Singlet Excited State

Ikuo Kawashima; Hiroaki Imoto; Masatoshi Ishida; Hiroyuki Furuta; Shunsuke Yamamoto; Masaya Mitsuishi; Susumu Tanaka; Toshiki Fujii; Kensuke Naka

doi:10.1002/anie.201904882

Dibenzoarsepins: Planarization of 8π-Electron System in the Lowest Singlet Excited State

Angew Chem Int Ed Engl. 2019 Aug 19;58(34):11686-11690. doi: 10.1002/anie.201904882. Epub 2019 Jul 24.

Authors

Ikuo Kawashima¹, Hiroaki Imoto¹, Masatoshi Ishida², Hiroyuki Furuta², Shunsuke Yamamoto³, Masaya Mitsuishi³, Susumu Tanaka¹, Toshiki Fujii¹, Kensuke Naka¹

Affiliations

¹ Faculty of Molecular Chemistry and Engineering, Graduate School of Science and Technology, Kyoto Institute of Technology, Goshokaido-cho, Matsugasaki, Sakyo-ku, Kyoto, 606-8585, Japan.
² Department of Chemistry and Biochemistry, Graduate School of Engineering and Center for Molecular Systems, Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka, 819-0395, Japan.
³ Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan.

PMID: 31251829
DOI: 10.1002/anie.201904882

Abstract

Dibenzo[b,f]arsepins possessing severely distorted cores compared to those of other heteropins were synthesized. These derivatives exhibited dual photoluminescence in the green-to-red region (500-700 nm) and the near-ultraviolet region (<380 nm), which could be attributed to the planarization of the arsepin core in the lowest singlet excited (S₁ ) state. The computational approach for the assessment of the aromatic indices revealed that the dibenzoarsepins studied show aromaticity (8π system) in the S₁ states in line with Baird's rule. The lone pair electrons of the arsenic atoms play a crucial role in the aromaticity in the S₁ states.

Keywords: Baird's rule; aromaticity; arsepins; excited-state aromaticity.