CF3 -Inspired Synthesis of Air-Tolerant 9-Phosphaanthracenes that Feature Fluorescence and Crystalline Polymorphs

Shigekazu Ito; Kota Koshino; Koichi Mikami

doi:10.1002/asia.201701669

CF₃ -Inspired Synthesis of Air-Tolerant 9-Phosphaanthracenes that Feature Fluorescence and Crystalline Polymorphs

Chem Asian J. 2018 Apr 4;13(7):830-837. doi: 10.1002/asia.201701669. Epub 2018 Feb 27.

Authors

Shigekazu Ito¹, Kota Koshino¹, Koichi Mikami¹

Affiliation

¹ Department of Chemical Science and Engineering, School of Materials and Chemical Technology, Tokyo Institute of Technology, 2-12-1-H113 Ookayama, Meguro, Tokyo, 152-8552, Japan.

PMID: 29377570
DOI: 10.1002/asia.201701669

Abstract

9-Phosphaanthracene (dibenzo[b,e]phosphorin, acridophosphine) has attracted interest as one of the heavier acenes. Herein, we demonstrate an efficient synthetic process that provides air-tolerant 1,8-bis(trifluoromethyl)-9-phosphaanthracenes. The sterically encumbered and electron-withdrawing trifluoromethyl (CF₃ ) groups are quite advantageous not only to stabilize the intrinsically unstable heavier unsaturated phosphorus atom but also to facilitate construction of the phosphinine skeleton based on a putative increase in aromaticity. The isolated 9-phosphaanthracenes allowed characterization of their fluorescence functionality and planar heteroanthracene frameworks. The crystal structures of 9-phosphaanthracenes are remarkably dependent on the aryl substituents at the 10 position; anthryl-substituted 9-phosphaanthracene showed unique polymorphs that induced different-colored crystals.

Keywords: acenes; fluorescence; heterocycles; phosphaalkenes; polymorphism.