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

摘要

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. ^S>ANT) forms a robust cation radical, whose structure was elucidated by X-ray crystallography and DFT calculations. While ^S>ANT was observed to racemize on a timescale (t1/2 ) of 1.1 hours, a computational conformational search and kinetic analysis of the racemization pathway led us to identify a simple methyl substituted ^S>ANT derivative, which does not racemize (racemization t1/2 ≃ 10¹³–10¹⁷ years).