Accordion-like Oscillation of Contracted and Stretched Helices of Polyacetylenes Synchronized with the Restricted Rotation of Side Chains

Yoshida, Yoshiaki; Mawatari, Yasuteru; Motoshige, Asahi; Motoshige, Ranko; Hiraoki, Toshifumi; Wagner, Manfred; Müllen, Kläus; Tabata, Masayoshi

doi:10.1021/ja4004987

Cited by 76 publications

(74 citation statements)

References 56 publications

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“…60,61 In a helical poly[(S)-2-octyl propiolate], they proposed an accordion-like helix oscillation (HELIOS) of one contracted cis−cisoid block and two stretched cis−transoid blocks along a single main chain, as evinced by NMR spectroscopy. 62 To obtain a stable cis−cisoid helix of PPA in solution, strong intramolecular hydrogen bonds are usually indispensable. Based on PPAs bearing (S)-α-methoxy-α-phenylacetic acid or (R)-α-methoxy-α-trifluoromethylphenylacetic acid pendants, Riguera et al obtained stable cis−cisoid helices in low polar solvents due to the strong intramolecular hydrogen bonds, and carefully investigated the solvent and ion effects as well as assembly behaviors.…”

Section: ■ Introductionmentioning

confidence: 99%

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Helical Conformations of Poly(3,5-disubstituted phenylacetylene)s Tuned by Pendant Structure and Solvent

et al. 2017

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A series of novel cis poly(phenylacetylene)s (PPAs) substituted at the meta-position(s) by both achiral alkoxycarbonyl and chiral alkylamide groups, i.e., rP-I, sP-I to sP-V, or by just a chiral alkylamide group, i.e., rP-VI, were synthesized under catalysis of [Rh(nbd)Cl] 2 . The dependence of the elongation, screw sense, and stimuli response of helical polyene backbone on the structure and number of substituent was systematically investigated in both solution and solid states. Stretched cis−transoid helices with opposite signs coexisted in the DMF solution of either sP-I or rP-I, but a single handed, contracted cis−cisoid one formed in the mixture of DMF/THF (10/90, v/v). Increasing the substituent size made the polymers sP-III, sP-IV, and sP-V to take only single handed stretched cis−transoid helical conformations regardless of the solvent polarity. The N-methylation of the amide group in sP-II caused a similar effect. With the removal of achiral methoxycarbonyl substituent, rP-VI took just a stretched cis−transoid helical conformation in polar DMF, whereas it existed as a mixture in equilibrium of stretched cis−transoid and contracted cis−cisoid helices with identical screw sense in less polar solvents such as dioxane, THF, and chloroform. The twisting directions of substituent array and polyene backbone were found to be coincident in a dynamic, contracted helix, but the opposite in a less dynamic, stretched helix. These results suggested that the 3,5-disubstitution, strong intramolecular hydrogen bonding, and small substituent favored the formation of contracted cis−cisoid helices for PPAs. ■ INTRODUCTIONHelix is the central structural motif in biomacromolecules such as genes and proteins, which plays vital roles in their fundamental and sophisticated biological activities. 1−5 Motivated by Nature, chemists have designed and prepared various synthetic polymers with helical main chains [e.g., poly-(isocyanide)s, 6−10 poly(isocyanate)s, 11−13 polyacetylenes, 14−18 poly(silane)s, 19,20 poly(methyl methacrylate)s, 21,22 polystyrenes, 23−26 polyguanidines, 27−29 and foldmers, 30,31 etc.]. Unlike nonhelical polymers, the materials based on helical polymers exhibit unique superiority in multichannel sensors, 32−34 enantioselective separation, 35−39 asymmetric catalysis, 40−44 among others. 45−49 Regulating the conformations of helical polymers at will would not only deepen our understanding of living systems 50 but also promote the development of novel materials. 5 As a result, control over the helical sense (lefthanded/right-handed) and the elongation (contracted/ stretched) has received ever-increasing attention in the last few decades. 51−53 Poly(phenylacetylene)s (PPAs) are a typical type dynamic helical polymers. 54−56 A PPA molecule possesses at least four possible conformers: cis−transoid, cis−cisoid, trans−cisoid, and trans−transoid. With rhodium diene complexes as the polymerization catalysts, PPAs with cis−transoid or cis−cisoid structures can be obtained. The former is a stretched structure, while the ...

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Section: ■ Introductionmentioning

confidence: 99%

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confidence: 99%

Helical Conformations of Poly(3,5-disubstituted phenylacetylene)s Tuned by Pendant Structure and Solvent

et al. 2017

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“…After drying the polymers, we took optical microscope images of the solid materials. As can be seen from Figure , PA 1–3 displayed a yellow/orange color and are present in the form of flakes. We proceeded with the morphological characterization of the polymers by using TEM.…”

Section: Resultsmentioning

confidence: 90%

“…In this work, we focused our attention on the chemical polymerizations of triple‐bond functionalized peptides that can produce colored (optical absorption above 380 nm) polymers with repeated peptide units joined together by conjugated double or alternating double–triple bonds . As a result, such peptide‐based polyacetylenes (PAs) or polydiacetylenes (PdAs) are expected to be electronically active and may be good candidates for the preparation of novel materials.…”

Section: Introductionmentioning

confidence: 99%

From self‐assembled peptide‐ynes to peptide polyacetylenes and polydiacetylenes

et al. 2018

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A set of four organogelators from an α‐amino acid derivative to a tetrapeptide, covalently linked to an acetylenic moiety, was studied in terms of polymerization efficiencies to afford peptide polyacetylenes and polydiacetylenes. Peptides were designed to improve the organogelator behavior via formation of intermolecular H‐bonding‐mediated β‐sheet networks as a function of their main‐chain length. The polymerization experiments were run under appropriate conditions for the various monomers with the aim at elucidating how the monomer self‐assembly process might influence polymer formation. Starting compounds and their corresponding polymers were characterized by a variety of spectroscopic and microscopic techniques.

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“…37 Three peaks of the branched methyl H e proton and its C h carbon seen at 0 C suggest three rotamers named A, B, and C, on the basis of the contracted helix and stretched one. The effect of temperature on UV-vis and CD spectra confirms the presence of contracted and stretched onehanded helical structures in which the helical pitches and their persistence lengths depend on the temperature.…”

Section: Thermoresponsive Pasmentioning

confidence: 99%

Stimuli-Responsive Polyacetylenes and Dendronized Poly(phenylacetylene)s

Masuda

Zhang

2016

Polymer Reviews

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Combination of stimuli responsiveness with p-conjugated polymers possesses probabilities not only to provide these polymers with unique interesting properties but also to promote new functions including various optoelectronic properties, catalysis, ionic sensing, and chiral recognition. In the former part of this review, recent developments of stimuli-responsive polyacetylenes are surveyed, which act as receptors towards external stimuli such as solvent, temperature, pH, chiral compounds, metal cations, various anions, electricity, light, etc., to transduce to other signals or energies, which leads to a wide range of intriguing properties to mimic biological processes or applications to smart or intelligent materials. In the latter part, we introduce dendronized poly(phenylacetylene)s (PPAs) exhibiting interesting thermoresponsive and chiroptical properties. Thermoresponsiveness of these dendronized conjugated polymers shows synchronous influence on their helical and hydrated conformations.

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Accordion-like Oscillation of Contracted and Stretched Helices of Polyacetylenes Synchronized with the Restricted Rotation of Side Chains

Cited by 76 publications

References 56 publications

Helical Conformations of Poly(3,5-disubstituted phenylacetylene)s Tuned by Pendant Structure and Solvent

Helical Conformations of Poly(3,5-disubstituted phenylacetylene)s Tuned by Pendant Structure and Solvent

From self‐assembled peptide‐ynes to peptide polyacetylenes and polydiacetylenes

Stimuli-Responsive Polyacetylenes and Dendronized Poly(phenylacetylene)s

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