Helix
Sense-Selective Supramolecular Polymerization
Seeded by a One-Handed Helical Polymeric Assembly
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Abstract
Helix
sense-selective supramolecular polymerization was achieved
using a one-handed helical nanotubular polymeric assembly as a seed.
First, bipyridine (BPY)-appended achiral hexabenzocoronene (<sup>BPY</sup>HBC) was copolymerized noncovalently with chiral <sup>BPY</sup>HBC<sub><i>S</i></sub> (or <sup>BPY</sup>HBC<sub><i>R</i></sub>) at a molar ratio of 9:1, which, via the sergeants-and-soldiers
effect, afforded a <i>P</i>-helical (or <i>M</i>-helical) nanotube, which was then treated with Cu<sup>2+</sup> to
transform into structurally robust <sup>(BPY)Cu</sup>NT<sub>(<i>P</i>)</sub> (or <sup>(BPY)Cu</sup>NT<sub>(<i>M</i>)</sub>) with a Cu<sup>2+</sup>/BPY coordination polymer shell. Helical
seeds <sup>(BPY)Cu</sup>NT<sub>(<i>P</i>)</sub> and <sup>(BPY)Cu</sup>NT<sub>(<i>M</i>)</sub> brought about the
controlled assembly of fluorinated chiral FHBC<sub><i>S</i></sub> and FHBC<sub><i>R</i></sub> as well as achiral FHBC
to yield one-handed helical nanotubular supramolecular block copolymers,
in which the helical senses of the newly formed block segments were
solely determined by those of the helical seeds employed. Noteworthy,
FHBC<sub><i>S</i></sub> and FHBC<sub><i>R</i></sub> alone without the helical seeds form ill-defined agglomerates. Attempted
supramolecular polymerization of a racemic mixture of FHBC<sub><i>S</i></sub> and FHBC<sub><i>R</i></sub> from <sup>(BPY)Cu</sup>NT<sub>(<i>P</i>)</sub> (or <sup>(BPY)Cu</sup>NT<sub>(<i>M</i>)</sub>) resulted in its chiral separation,
affording <i>P</i>-helical (or <i>M</i>-helical)
diastereomeric block segments composed of FHBC<sub><i>S</i></sub> and FHBC<sub><i>R</i></sub> with different thermodynamic
properties