2012
DOI: 10.1038/pj.2012.70
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Chiral amplification in double-stranded helical polymers through chiral and achiral amidinium–carboxylate salt bridges

Abstract: A series of m-terphenyl-based random copolymers of chiral and achiral amidines, and their complementary homopolymers of achiral carboxylic acids were prepared by the copolymerization of a p-diiodobenzene derivative, with the diethynyl monomers containing a chiral or achiral amidine group and a carboxyl group using the Sonogashira coupling reaction. The obtained chiral/achiral amidine copolymers assembled into a double-stranded helical structure upon complexation with the complementary achiral homopolymer of ca… Show more

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Cited by 6 publications
(6 citation statements)
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“…m -Terphenyl-based random copolymers bearing chiral and achiral amidine pendants ( R )- 522 also form an excess handed double-helix upon complexation with their complementary homopolymers with achiral carboxy pendants 521 through interstrand salt bridges between the amidinium and carboxylate units (Figure D) . The CD and absorption spectra revealed that the ( R )- 522 · 521 duplex shows the “sergeants and soldiers” effect, and its macromolecular helicity is significantly amplified by the chirality transfer from the chiral amidine moieties to the neighboring achiral ones upon complementary double-helix formation with the achiral carboxylic acid strand.…”
Section: Helical Polymers and Their Assembliesmentioning
confidence: 99%
“…m -Terphenyl-based random copolymers bearing chiral and achiral amidine pendants ( R )- 522 also form an excess handed double-helix upon complexation with their complementary homopolymers with achiral carboxy pendants 521 through interstrand salt bridges between the amidinium and carboxylate units (Figure D) . The CD and absorption spectra revealed that the ( R )- 522 · 521 duplex shows the “sergeants and soldiers” effect, and its macromolecular helicity is significantly amplified by the chirality transfer from the chiral amidine moieties to the neighboring achiral ones upon complementary double-helix formation with the achiral carboxylic acid strand.…”
Section: Helical Polymers and Their Assembliesmentioning
confidence: 99%
“…Owing to significant changes in the CD spectral patterns and intensities of the gels at different ( R )‐ 1⋅2 and 3⋅2 contents, quantitative evaluation of the chirality transfer ability of the chiral amidine residues to the achiral ones along the supramolecular double‐helix backbones may be difficult, although strong chiral amplification was observed when the second Cotton effect intensities were plotted against the molar ratio of ( R )‐ 1⋅2 (Figure 6 E). 17 However, it should be noted that the mixtures of ( R )‐ 1⋅2 and 3⋅2 before gelation displayed a weak, but clear, positive nonlinear relationship between the molar ratios of the ( R )‐ 1⋅2 fraction and the CD intensities at λ =285 and 311 nm immediately after preparation of the samples (Figure 7 C and D), whereas dilute solution of those in chloroform showed a completely linear relationship between them (Figure 7 A and B). These results suggest that chiral ( R )‐ 1 and achiral 3 coassemble to form helical assemblies in the presence of complimentary carboxylic acid strand 2 in the mixture of THF/ n ‐hexane at least at the initial stage of gelation; this also supports the formation of supramolecular double‐stranded helical polymers with amplification of the helical chirality.…”
Section: Resultsmentioning
confidence: 95%
“…This increase can be clearly interpreted as a cooperative effect within the molecular structure, often termed “helical amplification” or “chiral amplification”, [ 28 ] that saturates with 2–3 helix turns ( Figure ). It is remarkable that the transition from the dimer 12 to the hexamer ( S , S )‐ TP‐LPP 1 ‐C 13 (i.e., with approximately one turn of the helix) is accompanied by a three to fourfold increase of g abs .…”
Section: Resultsmentioning
confidence: 99%