Calculated Nuclear Magnetic Resonance Spectra of Polytwistane and Related Hydrocarbon Nanorods

Maryasin, Boris; Olbrich, Martin; Trauner, Dirk; Ochsenfeld, Christian

doi:10.1021/ct5011505

Cited by 9 publications

(16 citation statements)

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“…(Note also that the chemical shifts for tube (3, 0), polytwistane and polymer I are consistent with those calculated previously using the gauge-including atomic orbital approach). 11 This discrepancy suggests that it is unlikely for the nanothread sample to contain predominantly tube (3,0) and/or polytwistane as sp 3 components. The multiple chemical shifts for polymer I and stiffchiral-4 (see Figure S5 for the structures) are not symmetrically distributed with respect to the maximum of the experimental peak (the peak at 57 ppm for polymer 1 is offset significantly from the center peak of the experimental spectrum); thus, they are also less plausible to be the primary components of the nanothread sample (stiffchiral-4 can also be ruled out as a dominant component on the basis of chemical shift anisotropy, as discussed later).…”

Section: Nano Lettersmentioning

confidence: 99%

“…The 13 C magic-angle spinning (MAS) solid-state nuclear magnetic resonance (NMR) spectra of 13 C-enriched samples have revealed 80−85% sp 3 carbon content, with the remainder being sp 2 carbon, 7,10 and the 1D NMR response of a limited set of high-symmetry nanothread structures has been calculated. 11 Isolated double bonds as well as aromatic rings have been identified by two-dimensional NMR, and the length of pure sp 3 -hybridized segments with multiple nonequivalent sites, which account for 25−50% of the nanothreads, has been estimated at >2.5 nm based on 13 C NMR with spin diffusion. 10 Further experimental 12 and theoretical 13−15 work has explored more deeply the composition and properties of these fascinating nanothread geometries.…”

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confidence: 99%

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Constraining Carbon Nanothread Structures by Experimental and Calculated Nuclear Magnetic Resonance Spectra

Wang

Duan

et al. 2018

Nano Lett.

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A one-dimensional (1D) sp carbon nanomaterial with high lateral packing order, known as carbon nanothreads, has recently been synthesized by slowly compressing and decompressing crystalline solid benzene at high pressure. The atomic structure of an individual nanothread has not yet been determined experimentally. We have calculated the C nuclear magnetic resonance (NMR) chemical shifts, chemical shielding tensors, and anisotropies of several axially ordered and disordered partially saturated and fully saturated nanothreads within density functional theory and systematically compared the results with experimental solid-state NMR data to assist in identifying the structures of the synthesized nanothreads. In the fully saturated threads, every carbon atom in each progenitor benzene molecule has bonded to a neighboring molecule (i.e., 6 bonds per molecule, a so-called "degree-6" nanothread), while the partially saturated threads examined retain a single double bond per benzene ring ("degree-4"). The most-parsimonious theoretical fit to the experimental 1D solid-state NMR spectrum, constrained by the measured chemical shift anisotropies and key features of two-dimensional NMR spectra, suggests a certain combination of degree-4 and degree-6 nanothreads as plausible components of this 1D sp carbon nanomaterial, with intriguing hints of a [4 + 2] cycloaddition pathway toward nanothread formation from benzene columns in the progenitor molecular crystal, based on the presence of nanothreads IV-7, IV-8, and square polymer in the minimal fit.

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Section: Nano Lettersmentioning

confidence: 99%

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confidence: 99%

Constraining Carbon Nanothread Structures by Experimental and Calculated Nuclear Magnetic Resonance Spectra

Wang

Duan

et al. 2018

Nano Lett.

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“…Production of nanothreads from molecules other than benzene suggests that physical organic principles such as electron delocalization and steric/substitution effects govern their reaction, as opposed to topochemistry . Nuclear magnetic resonance spectroscopic studies suggest that nanothread formation begins with a [4 + 2] cycloaddition between two molecules of furan, leading to regions of sp 3 character, along with further polymerizable sp 2 segments. , If so, molecules with decreased electron delocalization and thus lessened aromatic character will lead to more mild reaction conditions, thus achieving product scalability.…”

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confidence: 99%

“…27 Nuclear magnetic resonance spectroscopic studies suggest that nanothread formation begins with a [4 + 2] two molecules of furan, leading to regions of sp 3 character, along with further polymerizable sp 2 segments. 28,29 If so, molecules with decreased electron delocalization and thus lessened aromatic character will lead to more mild reaction conditions, thus achieving product scalability. Benzene and pyridine are stable molecules not known for aromaticity-breaking reactions due to their intrinsic delocalized resonance energies of ∼0.060 eV per π electron.…”

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confidence: 99%

Scalable Synthesis of Crystalline One-Dimensional Carbon Nanothreads through Modest-Pressure Polymerization of Furan

Huss

Chen

et al. 2021

ACS Nano

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Carbon nanothreads, which are one-dimensional sp3-rich polymers, combine high tensile strength with flexibility owing to subnanometer widths and diamond-like cores. These extended carbon solids are constructed through pressure-induced polymerization of sp2 molecules such as benzene. Whereas a few examples of carbon nanothreads have been reported, the need for high onset pressures (≥17 GPa) to synthesize them precludes scalability and limits scope. Herein, we report the scalable synthesis of carbon nanothreads based on molecular furan, which can be achieved through ambient temperature pressure-induced polymerization with an onset reaction pressure of only 10 GPa due to its lessened aromaticity relative to other molecular precursors. When slowly compressed to 15 GPa and gradually decompressed to 1.5 GPa, a sharp 6-fold diffraction pattern is observed in situ, indicating a well-ordered crystalline material formed from liquid furan. Single-crystal X-ray diffraction (XRD) of the reaction product exhibits three distinct d-spacings from 4.75 to 4.9 Å, whose size, angular spacing, and degree of anisotropy are consistent with our atomistic simulations for crystals of furan nanothreads. Further evidence for polymerization was obtained by powder XRD, Raman/IR spectroscopy, and mass spectrometry. Comparison of the IR spectra with computed vibrational modes provides provisional identification of spectral features characteristic of specific nanothread structures, namely syn, anti, and syn/anti configurations. Mass spectrometry suggests that molecular weights of at least 6 kDa are possible. Furan therefore presents a strategic entry toward scalable carbon nanothreads.

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“…19 Nuclear Magnetic Resonance spectroscopic studies suggest that nanothread formation begins with a [4+2] cycloaddition between two molecules of furan, leading to regions of sp 3 character, along with further polymerizable sp 2 segments. 20,21 If so, molecules with decreased electron delocalization and thus lessened aromatic character will lead to more mild reaction conditions, thus achieving product scalability. Benzene and pyridine are stable molecules not known for aromaticity-breaking reactions due to their intrinsic delocalized resonance energies of ~0.060 eV per π electron.…”

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confidence: 99%

Scalable Synthesis of Crystalline One-Dimensional Carbon Nanothreads Through Modest-Pressure Polymerization of Furan

Huss¹,

Wu²,

Chen³

et al. 2020

Preprint

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<div><div><div><p>Carbon nanothreads, which are unique one-dimensional sp3-rich polymers, combine high tensile strength with flexibility owing to subnanometer widths and diamond-like cores. These extended carbon solids are constructed through pressure-induced polymerization of sp2 molecules such as benzene. Whereas a few examples of carbon nanothreads have been reported, the need for high onset pressures ( ≥ 17 GPa) to synthesize them precludes scalability and limits scope. Herein, we report the scalable synthesis of carbon nanothreads based on molecular furan, which can be achieved through ambient temperature pressure-induced polymerization with an onset reaction pressure of only 10 GPa due to its lessened aromaticity relative to other molecular precursors. When slowly compressed to 15 GPa and gradually decompressed to 1.5 GPa, a sharp six-fold diffraction pattern is observed in situ, indicating a well‐ordered crystalline material formed from liquid furan. Single-crystal X-ray diffraction of the reaction product exhibits three distinct d-spacings from 4.75 to 4.9 Å, whose size, angular spacing, and degree of anisotropy are consistent with our atomistic simulations for crystals of furan nanothreads. Further evidence for polymerization was obtained by powder XRD and Raman/IR spectroscopy. Comparison of the IR spectra with computed vibrational modes provides identification of spectral features characteristic of specific nanothreads, namely syn, anti, and syn/anti configurations. Furan therefore presents a strategic entry toward scalable carbon nanothreads.</p></div></div></div>

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Calculated Nuclear Magnetic Resonance Spectra of Polytwistane and Related Hydrocarbon Nanorods

Cited by 9 publications

References 36 publications

Constraining Carbon Nanothread Structures by Experimental and Calculated Nuclear Magnetic Resonance Spectra

Constraining Carbon Nanothread Structures by Experimental and Calculated Nuclear Magnetic Resonance Spectra

Scalable Synthesis of Crystalline One-Dimensional Carbon Nanothreads through Modest-Pressure Polymerization of Furan

Scalable Synthesis of Crystalline One-Dimensional Carbon Nanothreads Through Modest-Pressure Polymerization of Furan

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