Host-Guest Complexations of Amine Boranes and Isoelectronic/Isostructural Quaternary Alkylammonium Cations by Cucurbit[7]uril in Aqueous Solution
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Bibliographic record
Abstract
The host-guest complexation of six amine boranes (R 3 NBH 3 ) by the macrocyclic host molecule cucurbit<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:mo stretchy="false">[</mml:mo><mml:mn fontstyle="italic">7</mml:mn><mml:mo stretchy="false">]</mml:mo></mml:math>uril (CB<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M2"><mml:mo stretchy="false">[</mml:mo><mml:mn fontstyle="italic">7</mml:mn><mml:mo stretchy="false">]</mml:mo></mml:math>) in aqueous solution has been investigated using 1 H and 11 B NMR spectroscopy. The limiting complexation-induced 1 H and 11 B chemical shift changes indicate that the amine boranes are included in the hydrophobic cavity of the host molecule. The host-guest stability constants for neutral <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M3"><mml:mrow><mml:mfenced open="{" close="" separators="|"><mml:mrow><mml:mo> </mml:mo></mml:mrow></mml:mfenced></mml:mrow></mml:math>R 3 NBH 3 ∙ CB<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M4"><mml:mo stretchy="false">[</mml:mo><mml:mn fontstyle="italic">7</mml:mn><mml:mo stretchy="false">]</mml:mo><mml:mfenced open="" close="}" separators="|"><mml:mrow><mml:mo> </mml:mo></mml:mrow></mml:mfenced></mml:math> complexes (in the range of 10 5 -10 7 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M5"><mml:mrow><mml:msup><mml:mrow><mml:mi mathvariant="normal">M</mml:mi></mml:mrow><mml:mrow><mml:mtext>-</mml:mtext><mml:mn mathvariant="normal">1</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>) have been determined by 1 H NMR competition experiments and are compared with the corresponding values for the isoelectronic/isostructural <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M6"><mml:mrow><mml:mfenced open="{" close="" separators="|"><mml:mrow><mml:mo> </mml:mo></mml:mrow></mml:mfenced></mml:mrow></mml:math>R 3 NCH 3 ∙ CB<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M7"><mml:mo stretchy="false">[</mml:mo><mml:mn fontstyle="italic">7</mml:mn><mml:mo stretchy="false">]</mml:mo><mml:msup><mml:mrow><mml:mfenced open="" close="}" separators="|"><mml:mrow><mml:mo> </mml:mo></mml:mrow></mml:mfenced></mml:mrow><mml:mrow><mml:mo>+</mml:mo></mml:mrow></mml:msup></mml:math> complexes. Ammonia borane (H 3 NBH 3 ) does not form a host-guest complex with CB<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M8"><mml:mo stretchy="false">[</mml:mo><mml:mn fontstyle="italic">7</mml:mn><mml:mo stretchy="false">]</mml:mo></mml:math>. The trends in the host-guest stability constant with the guest molar volume are examined, and the stability is ascribed to the hydrophobic effect (packing coefficient) and quadrupole-dipole interactions.
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Full frame distilled prediction
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)
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 it