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

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 C2 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 C2 enantiomers (with a low
activation barrier) and a slower C2−D3 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 C2 geometry
with 60° end-to-end twist.