Structural Elucidation of the Triethylammonium Betaine of Squaric Acid

Betaines of squaric acid have gained research interest because of their structural and spectral properties. We elucidated the crystal and molecular structure of the triethylammonium betaine of squaric acid (1) by X-ray crystallography, IR, and NMR spectroscopy augmented by Hirshfeld surface analysis...

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Bibliographic Details
Published in:MolBank 2023-10, Vol.2023 (4), p.M1737
Main Authors: Palme, Paul R, Goddard, Richard, Leutzsch, Markus, Richter, Adrian, Imming, Peter, Seidel, Rüdiger W
Format: Article
Language:English
Subjects:
Acids
Ammonium compounds
Ammonium paratungstate
betaine
Betaines
Bonding strength
Crystal structure
Crystallography
Crystals
Density functionals
Hirshfeld surface analysis
Hybrid structures
Hydrogen
Hydrogen bonds
Identification and classification
Infrared spectroscopy
IR spectroscopy
Molecular structure
Nitrogen
NMR spectroscopy
Nuclear magnetic resonance spectroscopy
Properties
Solid state
Spectrum analysis
squaric acid
Structural analysis
Structure
Surface active agents
Surface analysis (chemical)
Symmetry
X-ray crystallography
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Summary:Betaines of squaric acid have gained research interest because of their structural and spectral properties. We elucidated the crystal and molecular structure of the triethylammonium betaine of squaric acid (1) by X-ray crystallography, IR, and NMR spectroscopy augmented by Hirshfeld surface analysis and DFT calculations. The crystal structure determination using Hirshfeld atom refinement reveals that the resonance hybrid structure with partial enolate character of the two lateral squaric acid C=O groups describes 1 best. The solid-state supramolecular structure features weak intermolecular C−H···O hydrogen bonds. The number of C=O bands in the IR spectrum in the solid-state is consistent with local C2v symmetry of the squaric acid residue in 1. The 13C NMR signals of this group in solution were assigned based on 2D NMR experiments and computational prediction using the Gauge-Independent Atom Orbital (GIAO) method. The present study provides the first structural characterization of a betaine of squaric acid containing a four-coordinate nitrogen atom directly attached to the four-membered ring.
ISSN:1422-8599
1422-8599
DOI:10.3390/M1737