Synthesis, Properties, and Two-Dimensional Adsorption Characteristics of 5-Aminohexahelicene
A convergent synthesis of racemic 5-aminohexahelicene is described. Cross-coupling reactions are used to assemble a pentacyclic framework, and a metal-catalyzed ring-closure comprises the final step. The enantiomers were separated by means of chromatography and the absolute configurations were assigned by comparison of the CD spectra with hexahelicene. The t(1/2) value for racemization at 210 degrees C was approximately 1 hour. Scanning tunneling microscopy (STM) measurements were carried out on enantiopure and racemic samples of aminohelicene on Au(111) under ultrahigh vacuum (UHV) conditions.