Isolation of a chiral anthracene cation radical: X-ray crystallography and computational interrogation of its racemization

Abstract

Chiral cation-radical salts hold significant promise as charge-transfer materials, chiroptical switches, and electron-transfer catalysts for enantioselective synthesis. Herein we demonstrate that the readily-available chiral 9,10-diphenyleanthracene derivative (i.e.^SANT) forms a robust cation radical, whose structure was elucidated by X-ray crystallography and DFT calculations. While ^SANT was observed to racemize on a timescale (t_1/2) of 1.1 hours, a computational conformational search and kinetic analysis of the racemization pathway led us to identify a simple methyl substituted ^SANT derivative, which does not racemize (racemization t_1/2 10¹³–10¹⁷ years).