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CF3-Inspired Synthesis of Air-Tolerant 9-Phosphaanthracenes Featuring Fluorescence and Crystalline Polymorphs.

Research paper by Shigekazu S Ito, Kota K Koshino, Koichi K Mikami

Indexed on: 30 Jan '18Published on: 30 Jan '18Published in: Chemistry - An Asian Journal



Abstract

9-Phosphaanthracene (dibenzo[b,e]phosphorin, acridophosphine) has been of interest as one of the heavier acenes. In this paper, we demonstrate an efficient synthetic process providing air-tolerant 1,8-bis(trifluoromethyl)-9-phosphaanthracenes. The sterically encumbered and electron-withdrawing trifluoromethyl (CF3) groups were quite advantageous not only to stabilize the intrinsically unstable heavier unsaturated phosphorus atom but also to facilitate construction of the phosphinine skeleton based on the putative increase of aromaticity. The isolable 9-phosphaanthracenes were effective to characterize the fluorescence functionality and the planar heteroanthracene framework. The crystal structures of 9-phosphaanthracenes are remarkably dependent on the aryl substituents at the 10-position; The anthryl-substituted 9-phosphaanthracene showed the unique polymorphs inducing different colour of crystals.