Revised Structure for the Diphenylaminyl Radical: The Importance of Theory in the Assignment of Electronic Transitions in Ph<sub>2</sub>X<sup>•</sup> (X = CH, N) and PhY<sup>•</sup> (Y = CH<sub>2</sub>, NH, O)
Bibliographic record
Abstract
Density functional theory indicates that the minimum energy structure of the diphenylaminyl radical, Ph 2 N •, has a “staggered” conformation in which the two phenyl rings are twisted relative to each other by an angle, φ, of 40°. In this conformation, the aromatic rings are oriented so as to maximize interaction with the unpaired electron while minimizing repulsion between the 2- and 2‘-hydrogen atoms. This calculated ground state structure of Ph 2 N • differs from that, which has been accepted for the past 15 years, which had the two rings orthogonal (φ = 90°) with one ring conjugating with the nitrogen's lone pair and the other conjugating with the unpaired electron. This structure was based on unexpected differences between the UV−vis absorption spectra of Ph 2 N • and the diphenylmethyl radical. However, our calculations indicate that this orthogonal structure lies 3.5 kcal/mol above the global minimum. Further support for the staggered conformation of Ph 2 N • is provided by the similarities between absorption transition wavelengths determined theoretically and the experimental absorption bands of Ph 2 N • and other diarylaminyl radicals generated by laser flash photolysis. The long wavelength transition of Ph 2 N •, resulting in a structure that can be represented as (Ph 2 ) + N -, is red-shifted as compared to the related transition from Ph 2 CH • to (Ph 2 ) + CH - due to the electronegativity of the N atom. The absorption bands for PhCH 2 •, PhNH •, and PhO • in the 300−450 nm region are similar in position, which has been taken to indicate that for isoelectronic species the electronic transition energies should be little affected by heteroatom substitution. Our calculations show, however, that these sets of absorption bands arise from different transitions. Therefore, the experimentally similar 300−450 nm absorption bands for these three radicals are fortuitous and do not reflect some common, unifying traits, a fact that further serves to emphasize the importance of theory in the assignment of bands due to electronic transitions.
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How this classification was reachedexpand
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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.002 |
| 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, 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".