Multinuclear Solid-State Magnetic Resonance and X-ray Diffraction Study of Some Thiocyanate and Selenocyanate Complexes Exhibiting Halogen Bonding
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Bibliographic record
Abstract
We report on the preparation and study of a series of thiocyanate and selenocyanate compounds exhibiting halogen bonding between iodine and nitrogen, sulfur, or selenium. The novel compounds (Me 4 NSeCN)( p -C 6 F 4 I 2 ) 2 ( 1 ), (Me 4 NSeCN)( o -C 6 F 4 I 2 ) 2 ( 2 ), and (Me 4 NSCN)( p -C 6 F 4 I 2 ) 2 ( 4 ) were synthesized. Their crystal structures and local halogen bonding interactions, along with those of related additional thiocyanate and selenocyanate compounds (e.g., KSCN, Me 4 NSCN, Me 4 NSeCN, etc.) were investigated by single-crystal X-ray diffraction and multinuclear ( 13 C/ 15 N/ 77 Se) solid-state magnetic resonance spectroscopy. Compounds 1 and 2 exhibit trifurcated I···SeCN – close contacts with characteristic bonding angles near 90°. X-ray and 13 C/ 15 N solid-state NMR evidence indicates that the thiocyanate moieties in 4 exhibit 2-fold disorder. The utility of 13 C/ 14 N dipolar coupling and residual dipolar coupling data is discussed. 14 N solid-state NMR spectroscopy is found to be impractical in the compounds of interest due to fast T 2 relaxation. 13 C chemical shifts of the thiocyanates are observed to increase slightly in complexes exhibiting halogen bonding relative to reference compounds with only simple counterions, while 15 N chemical shifts decrease slightly under the same conditions. The opposite trends are noted for the selenocyanates. More substantial changes are observed in both the 77 Se isotropic chemical shift and in the pseudounique principal component of the 77 Se chemical shift tensor when comparing simple selenocyanates with those where the 77 Se is engaged in halogen bonding interactions with iodine. These results are interpreted in the context of Ramsey’s theory to show that the iodine–selenium interactions are reflected in the 77 Se solid-state NMR parameters, thereby providing an example of the utility of NMR methods in characterizing halogen bonding interactions in the solid state.
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Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.000 | 0.000 |
Machine scores (provisional)
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Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
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