Analogues for the Molybdenum Center of Sulfite Oxidase: Oxomolybdenum(V) Complexes with Three Thiolate Sulfur Donor Atoms
Bibliographic record
Abstract
cis,trans-(L-N2S2)Mo(V)O(SR) [L-N2S2H2 = N,N'-dimethyl-N,N'-bis(mercaptophenyl)ethylenediamine; R = CH2Ph, CH2CH3, and p-C6H4-Y (Y = CF3, Cl, Br, F, H, CH3, CH2CH3, and OCH3)] are the first structurally characterized mononuclear Mo compounds with three thiolate donors, as occurs at the Mo active site in sulfite oxidase. X-ray crystal structures of the cis,trans-(L-N2S2)Mo(V)O(SR) compounds, where R = CH2Ph, CH2CH3, p-C6H4-OCH3, and p-C6H4-CF3, show a similar coordination geometry about the Mo atom with all three sulfur thiolate donors in the equatorial plane. This coordination geometry places two adjacent S ppi orbitals parallel to the Mo=O bond, analogous to the orientation in the ene-dithiolate ligand in sulfite oxidase; the third S ppi orbital lies in the equatorial plane. Charge-transfer transitions from the S p to the Mo d orbitals occur at approximately 28,000 cm(-1) (epsilon: 4,400-6,900 L mol(-1)] cm(-1)) and 15,500 cm(-1) (epsilon: 3,200-4,900 L mol(-1) cm(-1)). The EPR parameters are nearly identical for all the cis,trans-(L-N2S2)Mo(V)O(SR) compounds (g1 approximately 2.022, g2 approximately 1.963, g3 approximately 1.956, Al approximately 58.4 x 10(-4) cm(-1), A2 approximately 23.7 x 10(-4) cm(-1), A3 approximately 22.3 x 10(-4) cm(-1)) and are typical of an oxo-Mo(V) center coordinated by multiple thiolate donors. The g and A tensors are related by a 24 degrees rotation about the coincident g2 and A2 tensor elements, reflecting the approximate Cs coordination symmetry. These EPR parameters more closely mimic those of the low pH form of sulfite oxidase and the "very rapid" species of xanthine oxidase than previous model compounds with two or four thiolate donors. The cis,trans-(L-N2S2)Mo(V)O(SR) compounds undergo a quasi-reversible, one-electron reduction and an irreversible oxidation that show a linear dependence upon the Hammett parameter, sigmap, of the Y group. The cis,trans-(L-N2S2)Mo(V)O(SR) compounds provide a well-defined platform for the systematic investigation of the electronic structures of the Mo(V)OS3 centers and their implications for molybdoenzymes.
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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 | 0.001 | 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".