Polyaromatic N-heterocyclic carbene ligands and π-stacking. Catalytic consequences
Bibliographic record
Abstract
In the course of our most recent research, we demonstrated how homogeneous catalysts with polyaromatic functionalities possess properties that clearly differ from those shown by analogues lacking these polyaromatic systems. The differences arise from the ability of the polyaromatic groups to afford non-covalent interactions with aromatic molecules, which can either be substrates in a homogeneous catalysed reaction, or the same catalysts to afford self-assembled systems. This article summarizes all our efforts toward understanding the fundamental effects of π-stacking interactions in homogenous catalysis, particularly in those cases where catalysts bearing polyaromatic functionalities are used. The study reveals several important implications regarding the influence of ligand-ligand interactions, ligand-additive interactions, and ligand-substrate interactions, in the performance of the catalysts used. In particular, the electronic properties of ligands with fused polyconjugated systems, are modified if molecules with π-stacking abilities are added, via a ligand-additive interaction. Also, the kinetics of the reactions in which aromatic substrates and catalysts with polyaromatic ligands are used, are strongly influenced by the self-association of the catalysts and by the non-covalent interaction between the catalyst and the aromatic substrates. The nature and the magnitude of these supramolecular interactions were unveiled by using host-guest chemistry methods applied to organometallic catalysis. Finally, non-covalent interactions afford a very convenient approach for the immobilization of catalysts decorated with polyaromatic systems onto the surfaces of graphene derivatives, hence affording an easy yet extremely effective way to support catalysts and facilitate recycling. The results given have fundamental implications in the design of future catalysts containing rigid polyaromatic systems, and may inspire future researchers in the design of improved homogeneous catalysts, by taking into account that the activities of the metal complexes are strongly modified by supramolecular interactions.
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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) | 0.001 | 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".