Origins of aplanarities of carbonate anions in metal carbonates

• Published in: Polyhedron 2024-07, Vol.256, p.116984, Article 116984
• Main Authors: Dem'yanov, Piotr I., Polestshuk, Pavel M.
• Format: Article
• Language: English
• Subjects: Aplanarity; Carbonate anion; Ordered double carbonates; Orthorhombic carbonates
• ISSN: 0277-5387
• DOI: 10.1016/j.poly.2024.116984

Energies of interactions of the carbon and each oxygen atom of a carbonate anion with six cations coordinated to this anion in aragonite and cerussite are theoretically evaluated to ascertain reasons forcing carbonate anions to be deformed (aplanar) in orthorhombic carbonates. Origins of aplanarities of carbonate anions in dolomite and two other ordered double carbonates are analyzed also. [Display omitted] •Energies of interactions of O and C atoms of a carbonate anion with two types of cations in aragonite and cerussite.•Origins of aplanarities of carbonate anions in aragonite, cerussite, and other orthorhombic carbonates.•Origins of aplanarities of carbonate anions in ordered double carbonates.•Similar reasons cause likely aplanarities of nitrate anions in isotypic metal nitrates. Interaction energies of the carbon and oxygen atoms of the carbonate anion (CA) with its six coordinated cations in orthorhombic aragonite (CaCO3) and cerussite (PbCO3) are theoretically evaluated. A comparison of energies of interactions of singly and doubly coordinated cations with oxygen and carbon atoms of the CA as well as a detailed structural analysis allow one to estimate qualitatively the resultant electrostatic forces exerted by cations along the c direction on carbon and two types of oxygen atoms of the CA and to reveal reasons leading to aplanarities of CAs in these carbonates. Deviations of O atoms from the C1 atom in known neutron and X-ray diffraction (XRD) structures of various crystalline carbonates are analyzed to get additional information on the aplanarity origins in these inorganic substances. The impact of the cation size on the CA aplanarity degree, C-O bond lengths, and O-C-O bond angles in carbonates is analyzed also. Different strengths of interactions of cations, which are axially coordinated to the two opposite sides of the CA, with both oxygen and carbon atoms of this anion are demonstrated to provoke largely the pyramidalization (aplanarity) of CAs in orthorhombic and ordered double carbonates (ODCs).