Inorganic Tricarbonate : High-Pressure Synthesis and Structure of K₂C₃O₇

Title data

Aslandukov, Andrii ; Aslandukova, Alena ; Akbar, Fariia Iasmin ; Yin, Yuqing ; Akilli, Ridvan ; Garbarino, Gaston ; Spahr, Dominik ; Winkler, Bjoern ; Bykov, Maxim ; Dubrovinskaia, Natalia ; Dubrovinsky, Leonid:
Inorganic Tricarbonate : High-Pressure Synthesis and Structure of K₂C₃O₇.
In: Journal of the American Chemical Society. (24 March 2026) .
ISSN 1520-5126
DOI: https://doi.org/10.1021/jacs.5c19614

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Abstract in another language

The synthesis of carbonates with novel types of anions is important for geoscience, chemistry, and materials science. Herein, we present the first inorganic tricarbonate salt, K2C3O7, discovered in laser-heated diamond anvil cells at 55(3) and 45(2) GPa. The crystal structure of K2C3O7 was determined in situ by using synchrotron single-crystal X-ray diffraction from a polycrystalline sample. It features nonplanar [C3O7]2– anions, which consist of three corner-sharing planar CO3 groups rotated relative to one another. This anion extends the homologous series of sp2-carbonates: [CO3]2–─[C2O5]2–─[C3O7]2–. Raman spectroscopy establishes the characteristic vibrational fingerprint of the [C3O7]2– anion. Density functional theory (DFT) calculations corroborate the experimental results and suggest a thermodynamic stability of K2C3O7 between 10 and 55 GPa. DFT calculations predict a phase transition between 80 and 90 GPa associated with polymerization of the [C3O7]2– groups, accompanied by a change in the coordination polyhedra of two carbon atoms from triangles to tetrahedra. These results imply that other sp2-and mixed sp2/sp3-carbonates might be stabilized at a high pressure.The synthesis of carbonates with novel types of anions is important for geoscience, chemistry, and materials science. Herein, we present the first inorganic tricarbonate salt, K2C3O7, discovered in laser-heated diamond anvil cells at 55(3) and 45(2) GPa. The crystal structure of K2C3O7 was determined in situ by using synchrotron single-crystal X-ray diffraction from a polycrystalline sample. It features nonplanar [C3O7]2– anions, which consist of three corner-sharing planar CO3 groups rotated relative to one another. This anion extends the homologous series of sp2-carbonates: [CO3]2–─[C2O5]2–─[C3O7]2–. Raman spectroscopy establishes the characteristic vibrational fingerprint of the [C3O7]2– anion. Density functional theory (DFT) calculations corroborate the experimental results and suggest a thermodynamic stability of K2C3O7 between 10 and 55 GPa. DFT calculations predict a phase transition between 80 and 90 GPa associated with polymerization of the [C3O7]2– groups, accompanied by a change in the coordination polyhedra of two carbon atoms from triangles to tetrahedra. These results imply that other sp2-and mixed sp2/sp3-carbonates might be stabilized at a high pressure.