Simple Ligand-Field Theory of <i>d</i><sup>4</sup> and <i>d</i><sup>6</sup> Transition Metal Complexes with a <i>C</i><sub>3</sub> Symmetry Axis
Bibliographic record
Abstract
There have been a number of recent studies reporting high-spin d(4,6) complexes with three- and four-coordinate geometry, which exhibit roughly trigonal symmetry. These include complexes of Fe(II) with general formula L(3)FeX, where L = thioether or dialkylphosphine donors of a tripodal chelating ligand and X is a monodentate ligand on the C(3) axis. In these systems, there is unquenched orbital angular momentum, which has significant consequences on the electronic/magnetic properties of the complexes, including magnetic susceptibility, EPR spectra, and magnetic Mössbauer spectra. We describe here a simple model using a description of the d orbitals with trigonal symmetry that along with the application of the spin-orbit interaction successfully explains the magnetic properties of such systems. These d orbitals with 3-fold symmetry are complex orbitals with a parameter, a, that is determined by the bond angle, α, of LFeX. We demonstrate that the E symmetry states in such systems with S > 1/2 cannot be properly "simulated by" or be "represented by" the Zeeman and second-order zero-field spin Hamiltonian alone because by definition the parameters D and E are second-order terms. One must include the first-order spin-orbit interaction. We also find these systems to be very anisotropic in all their magnetic properties. For example, the perpendicular values of g and the hyperfine interaction parameter are essentially zero for the ground-state doublet. For illustrative purposes, the discussion focuses primarily on two specific Fe(II) complexes: one with the bond angle α greater than tetrahedral and another with the bond angle α less than tetrahedral. The nature of the EPR spectra and hyperfine interaction of (57)Fe are discussed.
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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) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.001 | 0.002 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.007 | 0.001 |
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".