Brightly Luminescent Platinum Complexes of <i>N<sup>∧</sup>C<sup><i>–</i></sup><sup>∧</sup>N</i> Ligands Forming Six-Membered Chelate Rings: Offsetting Deleterious Ring Size Effects Using Site-Selective Benzannulation
Bibliographic record
Abstract
Brightly emissive platinum(II) complexes (λ emission,max = 607–612 nm) of the type R L PtCl are reported, where R L is a cyclometalated N ∧ C –∧ N -coordinating ligand derived from 1,3-di(2-trifluoromethyl-4-phenanthridinyl)benzene ( CF3 LH ) or 1,3-di(2- tert -butyl-4-phenanthridinyl)benzene ( t Bu LH ). Metathesis of the chlorido ligand can be achieved under mild conditions, enabling isolation of ionic compounds with the formula [ CF3 L PtL′]PF 6 where L′ = pyridine or (4-dimethylamino)pyridine (DMAP), as well as the charge-neutral species t Bu L Pt(C≡C─C 6 H 4 ─ t Bu) (C≡C─C 6 H 4 ─ t Bu = 4- tert -butylphenylacetylido). Compared with N ∧ N ∧ N -ligated Pt(II) complexes that form 5-membered chelates, these compounds all contain 6-membered rings. Expanding the chelate ring size from 5 to 6 has been previously demonstrated to enhance emission in some N ∧ N ∧ N -coordinated Pt(II) species─for example, in complexes of 2,6-di(8-quinolinyl)pyridine vs those of 2,2′:6′,2″-terpyridine─but in related N ∧ C –∧ N -coordinated species, luminescence quantum yields are significantly lower for the 6-membered chelate ring complexes. Here, we demonstrate that site-selective benzannulation of the quinolinyl side-arms can offset the deleterious effect of changing the chelate ring-size and boost photophysical properties such as the quantum yield. Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations suggest that benzannulation counterintuitively destabilizes the emissive triplet states compared to the smaller π-system, with the “imine-bridged biphenyl” form of the phenanthridinyl arm helping to buffer against larger molecular distortions, enhancing photoluminescence quantum yields up to 0.09 ± 0.02. The spontaneous formation under aerated conditions of a Pt(IV) derivative ( CF3 L PtCl 3 ) is also reported, together with its molecular structure in the solid state.
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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".