Resolving a Half-Century-Long Controversy between (Magneto)optical and EPR Spectra of Single-Electron-Reduced [PcFe]<sup>−</sup>, [PcFeL]<sup>−</sup>, and [PcFeX]<sup>2–</sup> Complexes: Story of a Double Flip
Bibliographic record
Abstract
The reduction of iron(II) phthalocyanine (Pc(2−)FeII) or its bisaxially coordinated complexes results in the formation of the purple/red [PcFe]−, [PcFeL]−, and [PcFeX]2– (L is neutral and X is anionic ligand) species. The X-ray structure of the [K(DME)4][PcFe] complex exhibits a square-planar [PcFe]− anion. 1H NMR spectra of the reduced species have one or two phthalocyanine broad peaks between 15 and 17 ppm. Solution magnetic moments are consistent with the presence of a single unpaired electron. A solid-state Mössbauer spectrum of [K(DME)4][PcFe] is consistent with an early report [Taube, R. Pure Appl. Chem.1974, 38, 427−438]. The solid-state EPR spectrum of the [PcFe]− anion is close to that recorded by Konarev et al. [ Dalton Trans.2012, 41, 13841−13847]. Solution EPR spectra of reduced species have axial symmetry (g⊥ ∼ 2.08–2.17 and g|| ∼ 1.95–1.96) and correlate well with spectra reported by Lever and Wilshire in 1978 [ Inorg. Chem.1978, 17, 1145−1151]. The UV–vis spectra of pentacoordinated [PcFeL]− and [PcFeX]2– anions consist of the characteristic bands around 810, 690, and 515 nm. These bands correlate well with the set of MCD pseudo A-terms and resemble transitions in the [Pc(3−)M]− and [Pc(3−)ML]− compounds. The UV–vis and MCD spectra of [PcFeL]− and [PcFeX]2– complexes are in stark contrast to the crystallographically characterized reference [Pc(2−)CoI]− anion, which is EPR silent, has a regular diamagnetic 1H NMR spectrum, and has an intense Q-band at 699 nm, which correlates well with the strong MCD A-term. The DFT and TDDFT calculations are suggestive of the iron(II) center in a (dxy)2(dxz,yz)3(dz2)1 (s = 1) electronic configuration that is antiferromagnetically coupled with the one-electron-reduced Pc(3−) ligand (i.e., [Pc(3−)FeII]−, [Pc(3−)FeIIL]−, and [Pc(3−)FeIIX]2–). The calculated EPR, Mössbauer, and UV–vis spectra of [PcFe]−, [PcFeL]−, and [PcFeX]2– complexes are in excellent agreement with the experimental data, thus resolving the controversy between axial s = 1/2 like EPR and Pc(3−)-like UV–vis spectra of these compounds.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.002 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.002 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.006 | 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".