1,4,5,8,9,12-Hexamethyltriphenylene. A Molecule with a Flipping Twist

摘要

The synthesis and characterization of 1,4,5,8,9,12-hexamethyltriphenylene (5) is described. In the solid state, X-ray crystallographic studies reveal that compound 5 presents a highly distorted C_2 geometry with a 53° end-to-end twist. In solution, variable-temperature ~1H NMR studies and molecular modeling present a story of rapid dynamic conformational interconversions between two C_2 enantiomers (with a low activation barrier) and a slower C_2-D_3 interconversion (with a relatively high barrier)—the first time clear evidence of conformational interchange for these hindered triphenylenes has been provided. Further studies have established that 5 is a fluorescent stable blue emitter, and that the compound undergoes an irreversible one-electron electrochemical oxidation. Calculations have predicted this to be a radical cation of C_2 geometry with 60° end-to-end twist.