Arbeit zu binären Metalloxidclustern erscheint in JACS

Dichtefuntionaltheorie unzuverlässig!

Nachricht vom 08.10.2020

Sreekanta's und Marcel's Arbeit zur Schwingungsspektroskopie an binären Metalloxidclustern und der Zuverlässigkeit von Dichtefunktiontheorierechnungen in Bezug auf die energetsiche Reihenfolge der Isomere erscheint im Journal of the American Chemical Society

Dichtefunktionaltheorie sagt die energetische Reihefolge der Isomere falsch voraus. — Dichtefunktionaltheorie sagt die energetische Reihefolge der abgebildeten Isomere falsch voraus. (Reprinted with permission from J. Am. Chem. Soc. 2020 142, 18050. Copyright 2020 American Chemical Society)

We provide spectroscopic and computational evidence for a substantial change in structure and gas phase reactivity of Al₃O₄⁺upon Fe-substitution, which is correctly predicted by multireference (MR) wave function calculations. Al₃O₄⁺ exhibits a cone-like structure with a central trivalent O atom (C_3v symmetry). The replacement of the Al- by an Fe atom leads to a planar bicyclic frame with a terminal Al−O^•− radical site, accompanied by a change from the Fe^+III/O^−II to the Fe^+II/O^−I valence state. The gas phase vibrational spectrum of Al₂FeO₄⁺ is exclusively reproduced by the latter structure, which MR wave function calculations correctly identify as the most stable isomer. This isomer of Al₂FeO₄⁺is predicted to be highly reactive with respect to C−H bond activation, very similar to Al₈O₁₂⁺ which also features the terminal Al−O^•− radical site. Density functional theory, in contrast, predicts a less reactive Al₃O₄⁺-like “isomorphous substitution” structure of Al₂FeO₄⁺ to be the most stable one, except for functionals with very high admixture of Fock exchange (50%, BHLYP).

Valence and Structure Isomerism of Al₂FeO₄⁺: Synergy of Spectroscopy and Quantum Chemistry
F. Müller, J.B. Stückrath, F.A. Bischoff, L. Gagliardi, J. Sauer, S. Debnath, M. Jorewitz, K.R. Asmis
J. Am. Chem. Soc. 42, 18050–9 (2020)

DOI: 10.1021/JACS.0C07158