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Molecular analogue of the perovskite repeating unit and evidence for direct Mn^III-Ce^IV-Mn^III exchange coupling pathway.

ABSTRACT: The perovskite manganites AMnO₃ and their doped analogues A_1-x B _x MnO₃ (A and B = main group and lanthanide metals) are a fascinating family of magnetic oxides exhibiting a rich variety of properties. They are thus under intense investigation along multiple fronts, one of which is how their structural and physical properties are modified at the nanoscale. Here we show that the molecular compound [Ce₃Mn₈O₈(O₂CPh)₁₈(HO₂CPh)₂] (Ce^III₂Ce^IVMn^III₈; hereafter Ce₃Mn₈) bears a striking structural resemblance to the repeating unit seen in the perovskite manganites. Further, magnetic studies have established that Ce₃Mn₈ exhibits both the combination of pairwise Mn^III₂ ferromagnetic and antiferromagnetic exchange interactions, and the resultant spin vector alignments that are found within the 3-D C-type antiferromagnetic perovskites. First-principles theoretical calculations reveal not only the expected nearest-neighbor Mn^III₂ exchange couplings via superexchange pathways through bridging ligands but also an unusual, direct Mn^III-Ce^IV-Mn^III metal-to-metal channel involving the Ce^IV f orbitals.Perovskite manganites exhibit intriguing but poorly understood properties, including multiferroicity. Here, the authors synthesize a Ce₃Mn₈ cluster that structurally resembles a perovskite repeat unit, and use this molecular analogue to elucidate mechanisms driving bulk perovskite properties.

SUBMITTER: Thuijs AE

PROVIDER: S-EPMC5593820 | biostudies-literature | 2017 Sep

REPOSITORIES: biostudies-literature

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Molecular analogue of the perovskite repeating unit and evidence for direct MnIII-CeIV-MnIII exchange coupling pathway.

Thuijs Annaliese E AE Li Xiang-Guo XG Wang Yun-Peng YP Abboud Khalil A KA Zhang X-G XG Cheng Hai-Ping HP Christou George G

Nature communications 20170911 1

The perovskite manganites AMnO3 and their doped analogues A1-x B x MnO3 (A and B = main group and lanthanide metals) are a fascinating family of magnetic oxides exhibiting a rich variety of properties. They are thus under intense investigation along multiple fronts, one of which is how their structural and physical properties are modified at the nanoscale. Here we show that the molecular compound [Ce3Mn8O8(O2 ...[more]

PMID: 28894086

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Project description:Layered perovskites have been extensively investigated in many research fields, such as electronics, catalysis, optics, energy, and magnetics, because of the fascinating chemical properties that are generated by the specific structural features of perovskite frameworks. Furthermore, the interlayers of these structures can be chemically modified through ion exchange to form nanosheets. To further expand the modification of layered perovskites, we have demonstrated an advance in the new structural concept of layered perovskite "charge-neutral perovskite layers" by manipulating the perovskite layer itself. A charge-neutral perovskite layer in [CeIVTa2O7] was synthesized through a soft chemical oxidative reaction based on anionic [CeIIITa2O7]- layers. The Ce oxidation state for the charge-neutral [CeIVTa2O7] layers was found to be tetravalent by X-ray absorption fine structure (XAFS) analysis. The atomic arrangements were determined through scattering transmission electron microscopy and extended XAFS (EXAFS) analysis. The framework structure was simulated through density functional theory (DFT) calculations, the results of which were in good agreement with those of the EXAFS spectra quantitative analysis. The anionic [CeIIITa2O7]- layers exhibited optical absorption in the near infrared (NIR) region at approximately 1000 nm, whereas the level of NIR absorption decreased in the [CeIVTa2O7] charge-neutral layer due to the disappearance of the Ce 4f electrons. In addition, the chemical reactivity of the charge-neutral [CeIVTa2O7] layers was investigated by chemical reduction with ascorbic acid, resulting in the reduction of the [CeIVTa2O7] layers to form anionic [CeIIITa2O7]- layers. Furthermore, the anionic [CeIIITa2O7]- layers exhibited redox activity which the Ce in the perovskite unit can be electrochemically oxidized and reduced. The synthesis of the "charge-neutral" perovskite layer indicated that diverse features were generated by systematically tuning the electronic structure through the redox control of Ce; such diverse features have not been found in conventional layered perovskites. This study could demonstrate the potential for developing innovative, unique functional materials with perovskite structures.

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Molecular analogue of the perovskite repeating unit and evidence for direct Mn^III-Ce^IV-Mn^III exchange coupling pathway.

Publications

Molecular analogue of the perovskite repeating unit and evidence for direct Mn<sup>III</sup>-Ce<sup>IV</sup>-Mn<sup>III</sup> exchange coupling pathway.

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