Dataset Information

Catalytic N₂-to-NH₃ Conversion by Fe at Lower Driving Force: A Proposed Role for Metallocene-Mediated PCET.

ABSTRACT: We have recently reported on several Fe catalysts for N₂-to-NH₃ conversion that operate at low temperature (-78 °C) and atmospheric pressure while relying on a very strong reductant (KC₈) and acid ([H(OEt₂)₂][BAr^F₄]). Here we show that our original catalyst system, P₃^BFe, achieves both significantly improved efficiency for NH₃ formation (up to 72% for e^- delivery) and a comparatively high turnover number for a synthetic molecular Fe catalyst (84 equiv of NH₃ per Fe site), when employing a significantly weaker combination of reductant (Cp*₂Co) and acid ([Ph₂NH₂][OTf] or [PhNH₃][OTf]). Relative to the previously reported catalysis, freeze-quench Mössbauer spectroscopy under turnover conditions suggests a change in the rate of key elementary steps; formation of a previously characterized off-path borohydrido-hydrido resting state is also suppressed. Theoretical and experimental studies are presented that highlight the possibility of protonated metallocenes as discrete PCET reagents under the present (and related) catalytic conditions, offering a plausible rationale for the increased efficiency at reduced driving force of this Fe catalyst system.

SUBMITTER: Chalkley MJ

PROVIDER: S-EPMC5364448 | biostudies-literature | 2017 Mar

REPOSITORIES: biostudies-literature

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Publications

Catalytic N2-to-NH3 Conversion by Fe at Lower Driving Force: A Proposed Role for Metallocene-Mediated PCET.

Chalkley Matthew J MJ Del Castillo Trevor J TJ Matson Benjamin D BD Roddy Joseph P JP Peters Jonas C JC

ACS central science 20170214 3

We have recently reported on several Fe catalysts for N2-to-NH3 conversion that operate at low temperature (-78 °C) and atmospheric pressure while relying on a very strong reductant (KC8) and acid ([H(OEt2)2][BArF4]). Here we show that our original catalyst system, P3BFe, achieves both significantly improved efficiency for NH3 formation (up to 72% for e- delivery) and a compar ...[more]

PMID: 28386599

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Project description:BackgroundUnderstanding the in vivo size-dependent pharmacokinetics and toxicity of nanoparticles is crucial to determine their successful development. Systematic studies on the size-dependent biological effects of nanoparticles not only help to unravel unknown toxicological mechanism but also contribute to the possible biological applications of nanomaterial.MethodsIn this study, the biodistribution and the size-dependent biological effects of Fe3O4@SiO2-NH2 nanoparticles (Fe@Si-NPs) in three diameters (10, 20 and 40 nm) were investigated by ICP-AES, serum biochemistry analysis and NMR-based metabolomic analysis after intravenous administration in a rat model.ResultsOur findings indicated that biodistribution and biological activities of Fe@Si-NPs demonstrated the obvious size-dependent and tissue-specific effects. Spleen and liver are the target tissues of Fe@Si-NPs, and 20 nm of Fe@Si-NPs showed a possible longer blood circulation time. Quantitative biochemical analysis showed that the alterations of lactate dehydrogenase (LDH) and uric acid (UA) were correlated to some extent with the sizes of Fe@Si-NPs. The untargeted metabolomic analyses of tissue metabolomes (kidney, liver, lung, and spleen) indicated that different sizes of Fe@Si-NPs were involved in the different biochemical mechanisms. LDH, formate, uric acid, and GSH related metabolites were suggested as sensitive indicators for the size-dependent toxic effects of Fe@Si-NPs. The findings from serum biochemical analysis and metabolomic analysis corroborate each other. Thus we proposed a toxicity hypothesis that size-dependent NAD depletion may occur in vivo in response to nanoparticle exposure. To our knowledge, this is the first report that links size-dependent biological effects of nanoparticles with in vivo NAD depletion in rats.ConclusionThe integrated metabolomic approach is an effective tool to understand physiological responses to the size-specific properties of nanoparticles. Our results can provide a direction for the future biological applications of Fe@Si-NPs.

Dataset Information

Catalytic N₂-to-NH₃ Conversion by Fe at Lower Driving Force: A Proposed Role for Metallocene-Mediated PCET.

Publications

Catalytic N<sub>2</sub>-to-NH<sub>3</sub> Conversion by Fe at Lower Driving Force: A Proposed Role for Metallocene-Mediated PCET.

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