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δ-Bonding modulates the electronic structure of formally divalent nd¹ rare earth arene complexes.

ABSTRACT: Landmark advances in rare earth (RE) chemistry have shown that divalent complexes can be isolated with non-Aufbau 4f ⁿ {5d/6s}¹ electron configurations, facilitating remarkable bonding motifs and magnetic properties. We report a series of divalent bis-tethered arene complexes, [RE(NHAr^iPr₆ )₂] (2RE; RE = Sc, Y, La, Sm, Eu, Tm, Yb; NHAr^iPr₆ = {N(H)C₆H₃-2,6-(C₆H₂-2,4,6-iPr₃)₂}). Fluid solution EPR spectroscopy gives g _iso < 2.002 for 2Sc, 2Y, and 2La, consistent with formal nd¹ configurations, calculations reveal metal-arene δ-bonding via mixing of nd_{(x ²-y ²)} valence electrons into arene π* orbitals. Experimental and calculated EPR and UV-Vis-NIR spectroscopic properties for 2Y show that minor structural changes markedly alter the metal d_{(x ²-y ²)} contribution to the SOMO. This contrasts 4f ⁿ {5d/6s}¹ complexes where the valence d-based electron resides in a non-bonding orbital. Complexes 2Sm, 2Eu, 2Tm, and 2Yb contain highly-localised 4f ⁿ⁺¹ ions with no appreciable metal-arene bonding by density functional calculations. These results show that the physicochemical properties of divalent rare earth arene complexes with both formal nd¹ and 4f ⁿ⁺¹ configurations are nuanced, may be controlled through ligand modification, and require a multi-pronged experimental and theoretical approach to fully rationalise.

SUBMITTER: MacKenzie RE

PROVIDER: S-EPMC11361033 | biostudies-literature | 2024 Aug

REPOSITORIES: biostudies-literature

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δ-Bonding modulates the electronic structure of formally divalent nd1 rare earth arene complexes.

MacKenzie Ross E RE Hajdu Tomáš T Seed John A JA Whitehead George F S GFS Adams Ralph W RW Chilton Nicholas F NF Collison David D McInnes Eric J L EJL Goodwin Conrad A P CAP

Chemical science 20240805

Landmark advances in rare earth (RE) chemistry have shown that divalent complexes can be isolated with non-Aufbau 4f n {5d/6s}1 electron configurations, facilitating remarkable bonding motifs and magnetic properties. We report a series of divalent bis-tethered arene complexes, [RE(NHAriPr6 )2] (2RE; RE = Sc, Y, La, Sm, Eu, Tm, Yb; NHAriPr6 = {N(H)C6H3-2,6-(C6H2-2,4,6-<i ...[more]

PMID: 39220159

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Project description:Background: Rare Earth Elements (REEs) control methanol utilization in both methane- and methanol-utilizing microbes. It has been established that the addition of REEs leads to the transcriptional repression of MxaFI-MeDH [a two-subunit methanol dehydrogenase (MeDH), calcium-dependent] and the activation of XoxF-MeDH (a one-subunit MeDH, lanthanum-dependent). Both enzymes are pyrroquinoline quinone-dependent alcohol dehydrogenases and show significant homology; however, they display different kinetic properties and substrate specificities. This study investigates the impact of the MxaFI to XoxF switch on the behavior of metabolic networks at a global scale. Results: In this study we investigated the steady-state growth of Methylomicrobium alcaliphilum 20ZR in media containing calcium (Ca) or lanthanum (La, a REE element). We found that cells supplemented with La show a higher growth rate compared to Ca-cultures; however, the efficiency of carbon conversion, estimated as biomass yield, is higher in cells grown with Ca. Three complementary global-omics approaches-RNA-seq transcriptomics, proteomics, and metabolomics-were applied to investigate the mechanisms of improved growth vs. carbon conversion. Cells grown with La showed the transcriptional activation of the xoxF gene, a homolog of the formaldehyde-activating enzyme (fae2), a putative transporter, genes for hemin-transport proteins, and nitrate reductase. In contrast, genes for mxaFI and associated cytochrome (mxaG) expression were downregulated. Proteomic profiling suggested additional adjustments of the metabolic network at the protein level, including carbon assimilation pathways, electron transport systems, and the tricarboxylic acid (TCA) cycle. Discord between gene expression and protein abundance changes points toward the possibility of post-transcriptional control of the related systems including key enzymes of the TCA cycle and a set of electron-transport carriers. Metabolomic data followed proteomics and showed the reduction of the ribulose-monophosphate (RuMP) pathway intermediates and the increase of the TCA cycle metabolites. Conclusion: Cells exposed to REEs display higher rates of growth but have lower carbon conversion efficiency compared to cells supplemented with Ca. The most plausible explanation for these physiological changes is an increased conversion of methanol into formate by XoxF-MeDH, which further stimulates methane oxidation but limits both the supply of reducing power and flux of formaldehyde into the RuMP pathway.

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δ-Bonding modulates the electronic structure of formally divalent nd¹ rare earth arene complexes.

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δ-Bonding modulates the electronic structure of formally divalent nd<sup>1</sup> rare earth arene complexes.

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