Bonding and structures of copper-aminopyridine complexes — High-resolution electron spectroscopy and ab initio calculations
Bibliographic record
Abstract
Copper complexes of x-aminopyridine (x = 2, 3, 4) were prepared in a laser vaporization supersonic molecular beam source and identified using laser photoionization time-of-flight mass spectrometry. These complexes were studied by pulsed-field ionization zero electron kinetic energy (ZEKE) spectroscopy and second-order Møller-Plesset perturbation theory. Three structures formed by Cu binding to the pyridine nitrogen (σα), the amino nitrogen (σβ), and the pyridine ring (π) were considered by the theoretical calculations, but only the σα structures with Cu binding to the pyridine nitrogen were confirmed by the spectroscopic measurements. Adiabatic ionization energies and metal-ligand and ligand-based vibrational frequencies of the σα complexes were measured from the ZEKE spectra, and the metal-ligand bond energies of the neutral and ionized complexes were predicted by the theory. The ionization energies of the Cu complexes are about 20 000 cm–1 lower than that of bare Cu atom. This ionization energy shift is the result of the stronger Cu+-ligand bonding because of the additional charge-dipole interaction in the ion. Although the three complexes are formed by Cu coordination to the pyridine nitrogen atom, the position of the amino group affects the metal-ligand bonding strengths in both neutral and ionized species. These effects include the structural resonance and hydrogen bonding in the neutral complexes and the electric dipole moment and bidentate bonding in the ions.Key words: photoelectron, PFI-ZEKE, ab initio, copper aminopyridine.
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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) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 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".