Investigations on Squaric Acid in Superacidic Media

Area of Science:

• Inorganic Chemistry
• Solid-State Chemistry
• Supramolecular Chemistry

Background:

• Squaric acid is a unique organic molecule with interesting chemical properties.
• Superacidic media offer unique environments for chemical synthesis and stabilization of unusual species.
• Understanding protonation states is crucial for predicting and controlling chemical behavior.

Purpose of the Study:

• To synthesize and characterize protonated forms of squaric acid.
• To investigate the structural and spectroscopic properties of squaric acid salts.
• To explore the influence of protonation on the squaric acid carbon skeleton.

Main Methods:

• Synthesis in superacidic media (XF/MF5, M=As, Sb; X=H, D).
• Raman spectroscopy for characterization of protonated squaric acid salts.
• Single-crystal X-ray structure analysis for structural determination.
• Quantum chemical calculations (PBE1PBE/6-311G++(3df,3pd)) for vibrational spectra analysis.

Main Results:

• Synthesized salts of mono- and diprotonated squaric acid: [OC(COX)3][MF6] and [(COX)4][MF6]2·2HF.
• Determined crystal structures of [(COH)4][AsF6] (monoclinic, P21/n) and [OC(COH)3][AsF6] (monoclinic, P21/n).
• Observed changes in the carbon skeleton upon protonation, from dianion to tetrahydroxy dication.

Conclusions:

• Protonation of squaric acid in superacidic media yields stable salts with distinct structural motifs.
• The degree of protonation is controllable via stoichiometry, influencing the final product.
• Structural and spectroscopic data, supported by theoretical calculations, elucidate the behavior of squaric acid under extreme conditions.