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Construction and Systematical Symmetric Studies of a Series of Supramolecular Clusters with Binary or Ternary Ammonium Triphenylacetates
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Conformational Landscape and Polymorphism in 5-Acetic Acid Hydantoin
B A Nogueira1, G O Ildiz1,2, J Canotilho3
1CQC, Department of Chemistry, University of Coimbra, P-3004-535 Coimbra, Portugal.
The Journal of Physical Chemistry. A
|June 10, 2020
Summary
Quantum chemical calculations and experimental studies explored 5-acetic acid hydantoin (5AAH). Interestingly, the stable room-temperature polymorph adopts the highest-energy conformer geometry of the isolated molecule.
Area of Science:
- Computational chemistry
- Solid-state chemistry
- Spectroscopy
Background:
- 5-acetic acid hydantoin (5AAH) is a molecule with potential applications.
- Understanding its conformational landscape and solid-state behavior is crucial for its use.
Purpose of the Study:
- To investigate the conformational space of 5AAH using quantum chemical calculations.
- To experimentally determine the solid-state properties and identify polymorphs of 5AAH.
- To correlate the molecular geometry in the solid state with theoretical predictions.
Main Methods:
- Density Functional Theory (DFT) calculations at the B3LYP/6-311++G(d,p) level.
- Gas-phase to matrix isolation (10 K argon) of the most stable conformer.
- Infrared spectroscopy and normal coordinate analysis.
- Differential scanning calorimetry (DSC), polarized light thermal microscopy (PLTM), and Raman spectroscopy.
- Natural Bond Orbital (NBO) analysis for electronic structure.
Main Results:
- 13 conformers of 5AAH were identified, with 6 cis and 7 trans arrangements of the carboxylic group.
- The most stable conformer (cis-I) was isolated and its IR spectrum assigned.
- Five distinct polymorphs of 5AAH were identified through thermal analysis.
- The room-temperature stable polymorph surprisingly adopts the geometry of the highest-energy calculated conformer.
Conclusions:
- The conformational preferences of 5AAH in isolation differ significantly from its stable solid-state form.
- Experimental techniques confirm the existence of multiple polymorphs, highlighting the complexity of its solid-state behavior.
- This study provides valuable insights into structure-property relationships for 5AAH, relevant for material design.
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