Solid-state <sup>25</sup>Mg NMR, X-ray crystallographic, and quantum mechanical study of bis(pyridine)-(5,10,15,20-tetraphenyl porphyrinato)magnesium(II)
Bibliographic record
Abstract
We report solid-state 25Mg NMR, X-ray crystallographic, and quantum-mechanical calculation results for bis(pyridine)(5,10,15,20-tetraphenylporphyrinato)magnesium(II), Mg(TPP)·Py2. Mg(TPP)·Py2 crystallizes in the triclinic form, in the space group P[Formula: see text]. The unit cell parameters are: a = 9.6139(13) Å, b = 11.0096(16) Å, c = 11.8656(15) Å; α = 102.063(3)°, β = 103.785(3)°, γ = 114.043(2)°; Z = 1. The Mg(II) ion is coordinated to four nitrogen atoms from the porphyrin ring and two nitrogen atoms from the axial pyridine ligands, forming a regular octahedron. The 25Mg quadrupole coupling constant (CQ) is 15.32 ± 0.02 MHz, which represents the largest value so far observed for 25Mg nuclei. The electric field gradient tensor at the Mg site is axially symmetric, ηQ = 0.00 ± 0.05. The 25Mg chemical shielding anisotropy is too small to be accurately determined. Quantum-mechanical calculations using a 631G(d) basis set reproduce reasonably well the observed 25Mg NMR data for Mg(TPP)·Py2. The calculations also suggest that the span of the 25Mg chemical shift tensor is less than 50 ppm. Using a theoretical approach, we also investigate the dependence of the 25Mg quadrupole coupling constant on the MgNax bond distance. The calculation suggests that the 25Mg quadrupole coupling constant for an Mg(II) ion at the center of a porphyrin ring without axial ligands is approximately 22 MHz, which may be treated as an upper limit of the 25Mg quadrupole coupling constant for all Mgporphyrin complexes.Key words: 25Mg NMR, crystal structure, quantum chemical calculation, quadrupole parameter, tetraphenylporphyrin.
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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 | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".