Probing Optical Anisotropy and Polymorph‐Dependent Photoluminescence in [Ln<sub>2</sub>] Complexes by Hyperspectral Imaging on Single Crystals
Bibliographic record
Abstract
Abstract Two homodinuclear and one heterodinuclear lanthanide (Ln)‐based complexes of the general formula [Ln2(bpm)(tfaa)6] (Ln=Eu (1), Tb (2), Eu−Tb (3), bpm=2,2′‐bipyrimidine, tfaa−=1,1,1‐trifluoroacetylacetonate) were synthesized and characterized by single‐crystal photoluminescence spectroscopy and hyperspectral imaging. Complexes 1 and 2 crystallize in two polymorphic structures, while three polymorphs were isolated for 3, namely having needle‐, plate‐, and block‐like morphologies. Single‐crystal photoluminescence spectroscopy and imaging on Eu3+‐containing 1 and 3 revealed polymorph‐dependent J‐splitting of the hypersensitive 5D0→7F2 Eu3+ transition as well as electric‐to‐magnetic dipole emission intensity ratios. According to these observations, the lowest symmetry chemical environment was attributed to the Eu3+ ions present in the needle‐like polymorph, also in agreement with single‐crystal X‐ray diffraction analysis. More importantly, hyperspectral imaging on all three single‐crystal polymorphs of 3 exhibits optical anisotropy with photoluminescence enhancement at specific crystallographic faces. This behavior was ascribed to the distinct molecular packing of the Ln−Ln dimers in each polymorphic crystal as well as to face‐specific local symmetry of the Eu3+ centers. Overall, opto‐structural relationships of three Ln−Ln dimers and their single‐crystal polymorphs were established as a particularly promising avenue for control of photoluminescence by chemical crystal engineering.
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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".