Crystal structure, spectroscopic studies, and nonlinear optical (NLO) properties of Schiff base metal complexes containing an N, S donor ligand
Bibliographic record
Abstract
A new ligand, 4-dipropylaminobenzaldehyde thiosemicarbazone (abbreviated as HL), and its complexes ML2 (M = Ni, Pd, and Cu) have been synthesized and fully characterized by elemental analyses, EI-MS, IR and UVvis spectroscopy, and photoluminescence measurements. All of the compounds exhibit a bluegreen color with dual fluorescence in DMF solution. The quantum yield ratio (Φ′(CT)/Φ(LE)) decreases in the order NiL2 > HL > PdL2 > CuL2. The ligand HL crystallizes in the monoclinic system, space group P21/n, with a = 15.1680, b = 8.5573, and c = 25.3920 Å, β = 100.3457°, and V = 3242.2 Å3. The nickel complex (NiL2) crystallizes in the triclinic system, space group Pī, with a = 8.3093, b = 9.7540, and c = 10.2802 Å, α = 101.383°, β = 107.693°, γ = 96.703°, and V = 764.12 Å3. In these complexes, HL has lost a proton from its tautometric thiol form and acts as a single negatively charged bidentate ligand coordinating to the nickel ion via the mercapto sulfur and β-nitrogen atoms. The geometry around Ni(II) is almost square-planar with two equivalent NiN and two equivalent NiS bonds. The monomeric structure of HL or NiL2 is extended into an infinite two-dimensional network via hydrogen bonds. The two-photon absorption of HL and ML2 solutions (in DMF) was measured at 532 nm by the open-aperture Z-scan technique. Key words: crystal structure, metal complex, dual fluorescence, NLO.
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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".