Perfect and defective 13C-furan-derived nanothreads from modest-pressure synthesis analyzed by 13C NMR
Summary¶
Solid-state \(^{13}\)C NMR (including 2D \(^{13}\)C–\(^{13}\)C and \(^1\)H–\(^{13}\)C correlation, spectral editing, CODEX/rotational-echo techniques) characterizes nanothreads obtained by compressing \(^{13}\)C\(_4\)-labeled furan. Quantitative bonding statistics show overwhelmingly CH environments, minor CH\(_2\)/C=O/CH\(_3\) defects, trapped furan, and distinct anti vs syn-thread motifs; highly ordered saturated segments exhibit unusually slow spin exchange, implying extended regular segments (≥14 bonds). Quantum-chemical shift calculations match experimental \(^{13}\)C shifts for anti-thread models better than competing complex syn/anti hybrids, supporting anti connectivity as the dominant ordered backbone. The study is primarily experimental NMR plus quantum chemistry, with van Duin listed among computational contributors for shift assignment support.
Methods¶
This is an experimental solid-state NMR study of nanothreads from compressed \(^{13}\)C\(_4\)-labeled furan, with quantum-chemical shift calculations used to interpret \(^{13}\)C chemical-shift tensors. MD / reactive MD — N/A — not used.
Synthesis and experiments. The Experimental Section describes slow compression polymerization of labeled furan to a solid nanothread product. Multinuclear \(^{13}\)C NMR (including 2D \(^{13}\)C–\(^{13}\)C and \(^1\)H–\(^{13}\)C correlation, spectral editing, CODEX/rotational-echo based methods) characterizes bonding statistics, domain sizes via spin exchange, and dynamics (e.g. T\(_1\), partial inversion recovery to highlight “perfect” segments).
Static QM / DFT (for NMR assignment). The article uses DFT-based NMR chemical-shift methods (GIAO or equivalent) on candidate anti vs syn thread segment models, compared to measured \(^{13}\)C tensors. Functional and dispersion — see article and Supporting Information for the exact functional, dispersion treatment (if any), and basis set; this wiki note does not duplicate SI tables. k-sampling: for periodic DFT cell models, the SI lists k-point / k-mesh (or Γ-only) choices as appropriate to the supercell; N/A in p1–2 to restate the mesh. Structures / pathways: models of anti vs syn connectivity and related segment geometries underpin shift assignment; this is not a gas-phase reaction-path study. Properties: computed NMR shielding tensors, chemical shift tensors, and total energy / electronic energy differences between candidate models, plus NMR-related frequency-domain targets as tabulated, for comparison to experiment; numerical tables in SI.
Findings¶
Outcomes and mechanisms. Quantitative bonding statistics from spectral editing show overwhelmingly CH environments, with minor CH\(_2\), C=O, and CH\(_3\) defects, residual furan, and distinct anti vs syn-thread motifs. Highly ordered saturated segments show unusually slow inter-segment \(^{13}\)C spin exchange, consistent with long regular runs (the article discusses segment lengths on the order of many bonds).
Comparisons. Quantum-chemical shift calculations match experimental \(^{13}\)C data better for anti-thread models than for competing complex syn/anti hybrid scenarios, supporting anti connectivity as the dominant ordered backbone. CODEX-type analysis rules out a simple syn-tetrad picture with four distinct CH environments.
Corpus / KB honesty. The corpus pdf_path is a galley PDF; for final pagination, figure quality, and any post-galley corrections, use the version-of-record J. Am. Chem. Soc. article (DOI 10.1021/jacs.1c03671).
Limitations¶
Galley PDF in corpus; cite the journal version of record for final page numbers and any structure revisions. van Duin’s role is computational support alongside DFT/NMR interpretation (not ReaxFF MD in the abstract-level description). Solid-state NMR assignments can shift with magic-angle settings, probe architectures, and sample hydration—compare experimental conditions before drawing structure conclusions from shift matching alone. Nanothread products can be heterogeneous at micron scales; bulk NMR reports ensemble averages that may hide minor phases. JACS SI typically contains full computational details for shift tensors referenced in the main text. Experimental synthesis logs in SI also clarify pressure schedules that control thread conversion extent.
Relevance to group¶
Carbon nanothread chemistry paper with van Duin as co-author on modeling support.
Citations and evidence anchors¶
- JACS article DOI 10.1021/jacs.1c03671 — Abstract, Results, Supporting Information for computational detail.