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Remarkable amine-TFA self assembly.
Chagit Denekamp1, Eisaam Egbaria
1Department of Chemistry and Institute of Catalysis Science and Technology, Technion-Israel Institute of Technology, Haifa, Israel. chchagit@tx.technicon.ac.il
Journal of the American Society for Mass Spectrometry
|March 5, 2004
Summary
Steric effects govern amine-trifluoroacetic acid assembly, forming distinct protonated clusters. Stereochemistry influences cluster size, with specific isomers yielding higher-order supramolecular structures.
Area of Science:
- Supramolecular Chemistry
- Mass Spectrometry
- Computational Chemistry
Background:
- Amine-acid interactions are fundamental in chemistry.
- Understanding supramolecular assembly is key to designing new materials.
- Electrospray ionization mass spectrometry (ESI-MS) is a powerful tool for studying non-covalent interactions.
Purpose of the Study:
- To investigate the supramolecular assemblies formed between various amines and trifluoroacetic acid (TFA).
- To elucidate the role of steric effects and stereochemistry in the formation of protonated amine-TFA clusters.
- To characterize the structure and stability of these assemblies using mass spectrometry and computational methods.
Main Methods:
- Electrospray ionization mass spectrometry (ESI-MS) was employed to study amine-TFA interactions.
- Collision-induced dissociation (CID) experiments were performed on cluster ions.
- Density functional theory (DFT) calculations were utilized to model cluster structures.
Main Results:
- Primary, secondary, and tertiary amines exhibit distinct association behaviors with TFA, dominated by steric effects.
- Specific amines, like R-(+)-alpha-methylbenzylamine and 4-tert-butyl-cyclohexylamine, form high-order clusters.
- Stereochemistry significantly impacts cluster formation, with cis and trans isomers of 4-tert-butyl-1-phenylcyclohexylamine showing different assembly characteristics.
- DFT calculations suggest that abundant clusters are macrocyclic structures.
Conclusions:
- Steric hindrance is a primary factor controlling the size and structure of amine-TFA supramolecular assemblies.
- Stereochemistry plays a crucial role in dictating the specific association patterns and the formation of high-order clusters.
- The observed macrocyclic structures highlight the intricate self-assembly capabilities of these molecules.