Prediction of EPR <b>g</b> Tensors in Simple d<sup>1</sup> Metal Porphyrins with Density Functional Theory
Bibliographic record
Abstract
Electron paramagnetic resonance (EPR) g tensors of 20 five- or six-coordinated d 1 metal porphyrins following the [M E(P)]−L structural motif (M = V(IV), Nb(IV), Cr(V), Mo(V); E = N, O, S, Se; P = porphyrin dianion; L = F -, Cl -, Br -, ClO 4 -, OH -, OCH 3 -, H 2 O, or not present) were computed using density functional theory (DFT). For all complexes, the singly occupied molecular orbital (SOMO) is dominated by the metal d xy orbitals. Qualitative trends in Δ g components are determined by magnetic-field-induced coupling of the SOMO with three classes of molecular orbitals (MOs): (a) β-spin σ MOs formed by the metal d x 2 - y 2 atomic orbital (AO) and the porphyrin ligand; (b) the corresponding vacant α-spin σ* MOs; and (c) pairs of unoccupied α-spin π* MOs formed between the metal d xz (d yz ) AOs, p x (p y ) AOs of the axial ligands, and the porphyrin π system. The rich orbital system of the porphyrin ligand usually gives rise to multiple contributions of each type. As a consequence, electronic structure of the entire porphyrin ligand must be taken into account for the analysis of experimental g tensors. Values of the theoretical Δ g tensor components are systematically too positive compared to experiment. Once the systematic errors are accounted for, changes in the calculated g tensor components for complexes of metals from the same transition row are in good quantitative agreement with experiment. In oxomolybdenum porphyrinates [Mo O(P)]−L, the sixth ligand L influences g tensors both through geometrical distortion of the invariant part of the complex and by direct electronic interactions. Changes in the orientation of g tensors upon coordination of the sixth ligand arise mostly due to the electronic effects. The importance of the direct contribution increases for more covalent ligands L. The g tensor components of the isolated [Cr O(P)] + cation, which has not been characterized by EPR so far, are predicted to be Δ g ∥ = −15 and Δ g ⊥ = −20 ppt. The Δ g ∥ and Δ g ⊥ values for the [Mo O(P)] + complex are predicted to be −29 and −35 ppt.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| 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 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".