Triptycene-Based Ladder Polymers with One-Handed Helical Geometry

Here we report an
efficient synthesis of optically active ladder-type
molecules and polymers through intramolecular cyclization of chiral
triptycenes containing bis­[2-(4-alkoxyphenyl)­ethynyl]­phenylene units.
The electrophile-induced cyclization reactions are directed away from
the bridgehead carbon atoms of triptycene by steric factors, thereby
producing one-handed twisted ladder units without any detectable byproducts.
Moreover, the quantitative and regioselective nature of this intramolecular
cyclization allowed us to synthesize optically active ladder polymers
with a well-defined one-handed helical geometry in which homoconjugated
dibenzo­[a,h]­anthracene units are
helically arranged along the main chain. This synthesis route enables
the construction of a variety of nanoscale helical ladder architectures
and provides an entry into new chiroptical materials.