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The concept of metalla-aromaticity proposed by Thorn–Hoffmann ( Nouv. J. Chim . 1979, 3, 39) has been expanded to organometallic molecules of transition metals that have more than one independent electron-delocalized system. Lanthanides, with highly contracted 4f atomic orbitals, are rarely found in multiply aromatic systems. Here we report the discovery of a doubly aromatic triatomic lanthanide-boron molecule PrB 2 − based on a joint photoelectron spectroscopy and quantum chemical investigation. Global minimum structural searches reveal that PrB 2 − has a C 2v triangular structure with a paramagnetic triplet 3 B 2 electronic ground state, which can be viewed as featuring a trivalent Pr(III,f 2 ) and B 2 4− . Chemical bonding analyses show that this cyclo-PrB 2 − species is the smallest 4f-metalla-aromatic system exhibiting σ and π double aromaticity and multiple Pr–B bonding characters. It also sheds light on the formation of the rare B 2 4− tetraanion by the high-lying 5d orbitals of the 4f-elements, completing the isoelectronic B 2 4− , C 2 2− , N 2 , and O 2 2+ series.
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This content will become publicly available on March 1, 2026
Erbium and praseodymium doped lithium tantalate electronic structure and metal-oxygen bonding analyses
Electronic information and optical properties coupled with the Quantum Theory of Atoms in Molecules (QTAIM) and Electron Localization Function (ELF) analyses are used to elucidate the erbium (Er+3) and praseodymium (Pr+3) intraband f–f transitions in the lithium tantalate (LiTaO3) doped and co-doped configurations and the metal-oxygen bonding. The generalized gradient approximation calculations show that the Er+3- and Pr+3-4f bands appear closer to the conduction band bottom for Er+3 and Pr+3 at the Li sites and to the valance band top for Er+3 at the Ta sites. However, the corresponding hybrid functional calculations for the dopants at the Li site show that the Er+3 and Pr+3-4f bands spread in energy, which agrees with the observed intraband f–f transitions from the optical properties calculations. QTAIM shows that Ta-, Er+3-, and Pr+3-O bonding is incipient covalent for all configurations of this work. The absence of ELF in the metal-O regions aligns with QTAIM on the lack of strong covalent bonding in these compounds. This complementary insight highlights how weakly interacting metal-O atoms lead to delocalized electron density, a feature that influences the physical, electronic, and chemical behavior of the LiTaO3.
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- Award ID(s):
- 2112650
- PAR ID:
- 10591730
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Materials Today Communications
- Volume:
- 44
- Issue:
- C
- ISSN:
- 2352-4928
- Page Range / eLocation ID:
- 112047
- Subject(s) / Keyword(s):
- LiTaO3 Co-doping DFT QTAIM ELF Er+3 Pr+3
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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