Dynamic or Nondynamic? Helical Trajectory in Hexabenzocoronene Nanotubes Biased by a Detachable Chiral Auxiliary

When ether vapor was allowed to diffuse into a CH2Cl2 solution of an enantiomer of a hexa-peri-hexabenzocoronene (HBC) derivative carrying a chiral (BINAP)Pt(II)-appended coordination metallacycle (HBC[(R)-Pt]Py or HBC[(S)-Pt]Py), screw-sense-selective assembly took place to give optically active nanotubes (NT[(R)-Pt]Py or NT[(S)-Pt]Py) with helical chirality, which were enriched in either left-handed (M)-NT[(R)-Pt]Py or right-handed (P)-NT[(S)-Pt]Py, depending on the absolute configuration of the (BINAP)Pt(II) pendant. When MeOH was used instead of ether for the vapor-diffusion-induced assembly, nanocoils formed along with the nanotubes. As determined by scanning electron microscopy, the diastereomeric excess of the nanocoils was 60% (80:20 diastereomeric ratio). Removal of the (BINAP)Pt(II) pendants from NT[(R)-Pt]Py or NT[(S)-Pt]Py with ethylenediamine yielded metal-free nanotubes (NTPy) that remained optically active even upon heating without any change in the circular dichroism spectral profile. No helical inversion took place when NTPy derived from HBC[(R)-Pt]Py or HBC[(S)-Pt]Py was allowed to complex with (BINAP)Pt(II) with an absolute configuration opposite to the original one.