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Coexistence of Two Different Distorted Octahedral [MnF₆ ]^3- Sites in K₃ [MnF₆ ]: Manifestation in Spectroscopy and Magnetism.

ABSTRACT: As a consequence of the static Jahn-Teller effect of the ⁵ E ground state of Mn^III in cubic structures with octahedral parent geometries, their octahedral coordination spheres become distorted. In the case of six fluorido ligands, [MnF₆ ]^3- anions with two longer and four shorter Mn-F bonds making elongated octahedra are usually observed. Herein, we report the synthesis of the compound K₃ [MnF₆ ] through a high-temperature approach and its crystallization by a high-pressure/high-temperature route. The main structural motifs are two quasi-isolated, octahedron-like [MnF₆ ]^3- anions of quite different nature compared to that met in ideal octahedral Mn^III Jahn-Teller systems. Owing to the internal electric field of C_i symmetry dominated by the next-neighbour K⁺ ions acting on the Mn^III sites, both sites, the pseudo-rhombic (site 1) and the pseudo-tetragonally elongated (site 2) [MnF₆ ]^3- anions are present in K₃ [MnF₆ ]. The compound was characterized by single-crystal and powder X-ray diffraction, and magnetometry as well as by FTIR, Raman, and ligand field spectroscopy. A theoretical interpretation of the electronic structure and molecular geometry of the two Mn sites in the lattice is given by using a vibronic coupling model with parameters adjusted from multireference ab-initio cluster calculations.

SUBMITTER: Stoll C

PROVIDER: S-EPMC8362050 | biostudies-literature |

REPOSITORIES: biostudies-literature

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