Conjugated donor-acceptor substituted systems involving the 1,3-indandione-derived electron accepting moieties
Mark Sigalov1, Royi Mazor1, Arkady Ellern2
1Dept. of Chemistry, Ben-Gurion Univ. of the Negev Beer-Sheva 84105 Israel.
RSC Advances
|November 2, 2022
Summary
Researchers synthesized novel 1,3-indandione compounds, revealing that intermolecular contacts affect molecular geometry. Neglecting bridge donation and internal rotation can lead to misinterpreting NMR spectra and overestimating dipole moments.
Area of Science:
- Organic Chemistry
- Materials Science
- Computational Chemistry
Background:
- Conjugated donor-acceptor molecules exhibit unique photo- and electro-physical properties.
- Predicting and explaining unusual features in these compounds remains challenging.
- 1,3-indandione derivatives offer a tunable platform for studying conjugation.
Purpose of the Study:
- To synthesize and characterize 1,3-indandione derivatives with varying electron acceptor strength and bridge length.
- To investigate the impact of intermolecular contacts on molecular geometry.
- To elucidate the role of bridge donation and internal rotation in conjugation and properties.
Main Methods:
- Synthesis of novel 1,3-indandione derivatives.
- X-ray crystallography for structural analysis.
- Dynamic Nuclear Magnetic Resonance (D-NMR) spectroscopy.
- Density Functional Theory (DFT) calculations (B3LYP/aug-cc-pVDZ).
Main Results:
- X-ray structures revealed significant intermolecular short contacts influencing molecular geometries.
- D-NMR indicated unhindered rotation of the phenylamino moiety at room temperature (coalescence temperatures < 246 K).
- Computational studies showed calculated barriers to rotation, dipole moments, and hyperpolarizabilities were within experimental error.
- Discrepancies between experimental and computed dipole moments were observed when internal rotation and bridge donation were neglected.
Conclusions:
- Intermolecular interactions play a crucial role in solid-state molecular geometry.
- Internal rotation and electron-donating properties of bridges are essential considerations for accurate modeling.
- Misinterpretation of NMR spectra and overestimation of dipole moments can occur if these factors are ignored.
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