Helix Sense-Selective Supramolecular Polymerization Seeded by a One-Handed Helical Polymeric Assembly

Helix sense-selective supramolecular polymerization was achieved using a one-handed helical nanotubular polymeric assembly as a seed. First, bipyridine (BPY)-appended achiral hexabenzocoronene (^BPYHBC) was copolymerized noncovalently with chiral ^BPYHBC_<i>S</i> (or ^BPYHBC_<i>R</i>) 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 Cu²⁺ to transform into structurally robust ^(BPY)CuNT_(<i>P</i>) (or ^(BPY)CuNT_(<i>M</i>)) with a Cu²⁺/BPY coordination polymer shell. Helical seeds ^(BPY)CuNT_(<i>P</i>) and ^(BPY)CuNT_(<i>M</i>) brought about the controlled assembly of fluorinated chiral FHBC_<i>S</i> and FHBC_<i>R</i> 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_<i>S</i> and FHBC_<i>R</i> alone without the helical seeds form ill-defined agglomerates. Attempted supramolecular polymerization of a racemic mixture of FHBC_<i>S</i> and FHBC_<i>R</i> from ^(BPY)CuNT_(<i>P</i>) (or ^(BPY)CuNT_(<i>M</i>)) resulted in its chiral separation, affording <i>P</i>-helical (or <i>M</i>-helical) diastereomeric block segments composed of FHBC_<i>S</i> and FHBC_<i>R</i> with different thermodynamic properties

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-<i>peri</i>-hexabenzocoronene (HBC) derivative carrying a chiral (BINAP)­Pt­(II)-appended coordination metallacycle (HBC^Py_{[(<i>R</i>)‑Pt]} or HBC^Py_{[(<i>S</i>)‑Pt]}), screw-sense-selective assembly took place to give optically active nanotubes (NT^Py_{[(<i>R</i>)‑Pt]} or NT^Py_{[(<i>S</i>)‑Pt]}) with helical chirality, which were enriched in either left-handed (<i>M</i>)-NT^Py_{[(<i>R</i>)‑Pt]} or right-handed (<i>P</i>)-NT^Py_{[(<i>S</i>)‑Pt]}, 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^Py_{[(<i>R</i>)‑Pt]} or NT^Py_{[(<i>S</i>)‑Pt]} with ethylenediamine yielded metal-free nanotubes (NT^Py) that remained optically active even upon heating without any change in the circular dichroism spectral profile. No helical inversion took place when NT^Py derived from HBC^Py_{[(<i>R</i>)‑Pt]} or HBC^Py_{[(<i>S</i>)‑Pt]} was allowed to complex with (BINAP)­Pt­(II) with an absolute configuration opposite to the original one

Size-Selective Recognition by a Tubular Assembly of Phenylene–Pyrimidinylene Alternated Macrocycle through Hydrogen-Bonding Interactions

Study of artificial tubular assemblies as a useful host scaffold for size-selective recognition and release of guest molecules is an important subject in host–guest chemistry. We describe well-defined self-assembled nanotubes (<b>NT</b>_<b>6mer</b>) formed from π-conjugated <i>m</i>-phenylene–pyrimidinylene alternated macrocycle <b>1</b>_<b>6mer</b> that exhibit size-selective recognition toward a specific aromatic acid. In a series of guest molecules, a size-matched trimesic acid (<b>G3</b>) gives inclusion complexes (<b>NT</b>_<b>6mer</b>⊃<b>G3</b>) in dichloromethane resulting in an enhanced and red-shifted fluorescence. ¹H nuclear magnetic resonance (NMR) titration experiments indicated that the complex was formed in a 1:1 molar ratio. Density functional theory (DFT) calculations and the binding constant value (<i>K</i> = 1.499 × 10⁵ M^–1) of <b>NT</b>_<b>6mer</b> with <b>G3</b> suggested that the complex involved triple hydrogen-bonding interactions. The encapsulated guest <b>G3</b> molecules can be readily released from the tubular channel through the dissociation of hydrogen bonding by the addition of a polar solvent such as dimethylsulfoxide (DMSO). In contrast, <b>1</b>_<b>6mer</b> could not form self-assembled nanotubes in CHCl₃ or tetrahydrofuran (THF) solution, leading to weak or no size-selective recognizability, respectively