Intimate electronic coupling in cationic homodimeric iridium(iii) complexes
Bibliographic record
Abstract
Herein, we report two new cationic iridium(III) homodinuclear structures linked through a diyne moiety at the 5-position of the bipyridyl ligand (1,4-di(2,2'-bipyridin-5-yl)buta-1,3-diyne) and compare these to mononuclear model systems bearing a 5-ethynyl-2,2'-bipyridine ligand. Low energy bands observed in the absorption spectra point to charge-transfer transitions for all four complexes, with these bands red-shifted in the case of the two dinuclear complexes. Electrochemical studies show metal-centred oxidation and ligand-centred first reduction potentials. In the case of the dimer bearing 2-phenylpyridine (ppyH) cyclometallating ligands, cyclic voltammetry (CV) measurements reveal two one-electron oxidation waves and a corresponding reduction in the HOMO-LUMO gap (ΔE(red-ox)) compared to a mononuclear system, pointing to a significant electronic coupling between the two iridium(III) metals. The room temperature emission spectrum of this dimer is also bathochromically shifted, corroborating the CV data. In the case of the iridium dimer bearing 2-(2,4-difluorophenyl)-5-methylpyridine (dFMeppy) ligands, only a single one-electron oxidation wave is observed, but with the expected smaller ΔE(red-ox) value, compared to its mononuclear counterpart. The emission spectra at room temperature are generally broad and featureless with only modest quantum efficiencies (Φ(PL) = 1.4-8.4%) in 2-methyltetrahydrofuran (2-MeTHF) solution. All complexes emit at 77 K with lifetimes on the order of 4 μs. A combined density functional theory (DFT) and time-dependent DFT (TDDFT) study reveals that the emission process is best described as a mixed metal-to-ligand/ligand-to-ligand charge transfer (MLCT/LLCT).
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".