Formation of Graphitic Nanotubes with One-handed Helical Chirality

Significance

Graphitic nanotubes with right- and left-handed helical chirality were prepared, respectively, by self-assembly of (S)- and (R)-enan­tiomers of amphiphilic hexa-peri-hexabenzocoronene 2 having two chiral oxyalkylene side chains with two dodecyl side chains. These nanotubes had a uniform diameter of 20 nm and a wall thickness of 3 nm with an aspect ratio of more than 1000. In contrast, (S)- or (R)-3 with chiral lipophilic side chains did not form nanotubular assemblies. The authors have also found a novel nonlinear phenomenon for noncovalent, supramolecular polymers referred as ‘chiral amplification’, where the major enantiomer incorporated into each na­notube determined the helical sense. Thus, the mixtures of (S)- and (R)-enantiomers of 2 at varying mole ratios in methyl tetrahydrofuran were prepared to afford nanotubes with helical chirality, whose circular dichroism profiles were almost unchanged over a wide range of the enantiomeric excess (20-100% ee).