Solid-State <sup>65</sup>Cu and <sup>31</sup>P NMR Spectroscopy of Bis(triphenylphosphine) Copper Species
Bibliographic record
Abstract
Frequency-stepped ultrawideline (UW) 65 Cu solid-state NMR (SSNMR) experiments have been performed on a series of nine bis(triphenylphosphine) copper(I) species, with eight of these having an oxyanion-based ligand and one a borohydride ligand. These copper atoms reside in spherically asymmetric environments featuring two covalent Cu−P bonds and coordination from single bidentate ligands. The QCPMG pulse sequence was utilized in NMR experiments on all of the samples, along with the WURST-QCPMG sequence on select samples, to acquire UWNMR spectra of high quality. In all cases, large 65 Cu quadrupolar coupling constants ( C Q ) between 40.8 and 51.7 MHz are observed, and are confirmed by NQR measurements. The immense quadrupolar interactions and their correspondingly large contributions to the central-transition powder patterns make accurate quantification of copper chemical shift anisotropy (CSA) difficult, though CSA effects are observed. 1 H− 31 P CP/MAS NMR spectra reveal one-bond J -couplings, 1 J ( 65/63 Cu, 31 P), for all complexes, as well as the presence of residual dipolar coupling, which enables determinations of both the sign of C Q and the orientation of the EFG tensor with respect to the Cu−P dipolar vector (both of which are unavailable from standard 65 Cu SSNMR experiments). The 65 Cu EFG parameters and 1 J ( 65/63 Cu, 31 P) coupling constants are sensitive to the local geometry and bond lengths about the Cu center. Ab initio calculations are used to confirm experimentally predicted orientations of the Cu EFG tensors, to predict experimental C Q, η Q, and CS tensor values, and to aid in identifying relationships between the copper NMR parameters and molecular structures. This combination of experimental and theoretical NMR data enables the correlation of symmetry and local structure with copper NMR parameters, further extending the applicability of copper SSNMR spectroscopy to a wide variety of copper-containing systems.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".