2021
DOI: 10.1002/anie.202014780
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Photochemical Electrocyclization of Poly(phenylacetylene)s: Unwinding Helices to Elucidate their 3D Structure in Solution

Abstract: Photochemical electrocyclization of poly(phenylacetylene)s (PPAs) is used for the structural elucidation of apolyene backbone.This method not only allows classification of PPAs in cis-cisoidal (w 1 < 908 8)o rc is-transoidal structures (w 1 > 908 8), but also approximating w 1 .APPAs olution is illuminated with visible light and monitoring the photochemical electrocyclization of the PPAhelix by measuring the ECD spectra at different times.P PAsw ith ac is-cisoidal structure show ar eduction of the ECD signal o… Show more

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Cited by 23 publications
(19 citation statements)
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“…Chiroptical properties of PG1 were investigated in aqueous solutions at room temperature (25 °C) in the presence of different anions; the circular dichroism (CD) spectra are shown in Figure a. Obvious Cotton effects were observed with the first positive peak around 370 nm and the second negative peak around 310 nm in the wavelength range of 290–430 nm, suggesting that the polymer main chain adopts a preferred right-handed helix conformation. , Surprisingly, PG1 showed nearly identical Cotton effects at 25 °C, irrelevant to the presence of either salt-in or salt-out anions, although these anions exhibit large differences for T cp . Since the chirality of PPAs is dependent mainly on the ordered orientation of OEG pendants around the backbone through cooperative H bonding in the neighboring units, these unvaried CD spectra indicate that, at room temperature, added anions can only interact differently with OEG moieties (to afford different thermoresponsiveness) but not with the inner part of the polymer chains to exert influence on the backbone chirality.…”
Section: Results and Discussionmentioning
confidence: 99%
“…Chiroptical properties of PG1 were investigated in aqueous solutions at room temperature (25 °C) in the presence of different anions; the circular dichroism (CD) spectra are shown in Figure a. Obvious Cotton effects were observed with the first positive peak around 370 nm and the second negative peak around 310 nm in the wavelength range of 290–430 nm, suggesting that the polymer main chain adopts a preferred right-handed helix conformation. , Surprisingly, PG1 showed nearly identical Cotton effects at 25 °C, irrelevant to the presence of either salt-in or salt-out anions, although these anions exhibit large differences for T cp . Since the chirality of PPAs is dependent mainly on the ordered orientation of OEG pendants around the backbone through cooperative H bonding in the neighboring units, these unvaried CD spectra indicate that, at room temperature, added anions can only interact differently with OEG moieties (to afford different thermoresponsiveness) but not with the inner part of the polymer chains to exert influence on the backbone chirality.…”
Section: Results and Discussionmentioning
confidence: 99%
“…As with PPAs, PDPAs are made up of two coaxial Angewandte Chemie helices, one described by the polyene backbone and the other described by the pendants. [70] In order to stablish a relationship between internal and external helices, computational studies [TD-DFT(CAMÀ B3LYP)/3-21G] [103][104][105][106] were performed on a P helix (n = 20 m.r.u.) for a PDPA with trans-transoidal skeleton, ω 1 = À 165°, ω 2 = 180°, ω 3 = 40°(Figure 4a, d).…”
Section: Methodsmentioning
confidence: 99%
“…Therefore, as model compounds we chose poly‐( 3 – 6 ) (Figure 2a). Poly‐ 3 [100] and poly‐ 4 [54] were selected due to their resemblance with poly‐ 1 and poly‐( S )‐ 2 , while poly‐ 5 [70] and poly‐ 6 were chosen due to the possibility of generating a trans ‐PPA ( E ‐PPA, poly‐ 6 ) by isomerization of a cis ‐PPA ( Z ‐PPA, poly‐ 5 ) (Figure 2a). The isomerization of the polyene backbone proceeds through the generation of a delocalized radical cation in the polyene when the anilide group of the PPA interacts with Au 3+ (see Supporting Information).…”
Section: Resultsmentioning
confidence: 99%
“…By combining the information obtained from the ECD and AFM studies of poly‐( S )‐ 2 in DMF, we can state that the first positive Cotton band (CD 400 >0) corresponds to a P helical structure described by the pendant groups (external helix). As with PPAs, PDPAs are made up of two coaxial helices, one described by the polyene backbone and the other described by the pendants [70] …”
Section: Resultsmentioning
confidence: 99%