Investigation of Supramolecular Self-Assembly in Sn(IV)-5,10,15,20-tetra(4-bromo-2,6-difluorophenyl) Porphyrins Mediated through Activated Sigma Hole
Bibliographic record
Abstract
The article presents the design, synthesis, characterization, and investigation of halogen-bonding interactions in a series of six-coordinated Sn(IV) complexes based on 5,10,15,20-tetra(4-bromophenyl) porphyrin [Sn(IV)TBrPr] and 5,10,15,20-tetra(4-bromo-2,6-difluoro phenyl) porphyrin [Sn(IV)TBrFPr] with symmetrical axial linkers 3,5-dibromobenzoic acid (3,5-DiBrBA) and 4-bromobenzoic acid (4-BrBA) and nonsymmetrical axial linker 5-bromo nicotinic acid (5-BrNA). Four compounds, namely, Sn(5-BrNA) 2 (TBrPr) (1), Sn(5-BrNA) 2 (TBrFPr)·2DMF (2), Sn(3,5-DiBrBA) 2 (TBrFPr) (3), Sn(4-BrBA) 2 (TBrFPr) (4), were synthesized and characterized by single-crystal X-ray crystallography. All of the compounds were characterized by 1 H NMR, UV–vis absorption, emission, scanning electron microscopy, and cyclic voltammetry. Diverse supramolecular interactions involving bromine and fluorine atoms like Br···Br, Br···F, Br···π, and F···F are successfully manifested in our systems. The single-crystal analysis reveals that the self-assembly in compound 3 displays the shortest type II Br···Br contact of 3.401(3) Å in the realm of porphyrin assemblies, which leads to the formation of a porphyrin dimer. An interesting example of the shortest Br···F contact of 2.937(2) Å is found in compound 4, which facilitates the formation of 3D supramolecular architecture with well-defined hexagonal voids. The shortest contacts observed in our systems are persuaded by the cooperative interactions of the bromine atoms and by the most electron-withdrawing fluorine atoms on the porphyrin skeleton. Electrostatic potential surface analyses show that the σ-hole potential in the bromine atoms is increased by 6.5 kcal by the fluorine atoms. Optical and electrochemical studies detail the electronic structure of the title compounds under the influence of fluorine atoms and axial linkers, while theoretical studies were conducted to calculate the highest occupied molecular orbital–least unoccupied molecular orbital gap to relate with the experimental values.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| 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 teacher head, 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".