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1. Reciprocal Redox Interactions of Lithium Cobalt Oxide Nanoparticles with Nicotinamide Adenine Dinucleotide (NADH) and Glutathione (GSH): Toward a Mechanistic Understanding of Nanoparticle-Biological Interactions

   https://doi.org/10.1039/D0EN01221A  

   Henke, Austin ; Laudadio, Elizabeth Dina ; Hedlund Orbeck, Jenny K ; Abbaspour Tamijani, Ali ; Hoang, Khoi Nguyen ; Mason, Sara E. ; Murphy, Catherine ; Feng, Z. Vivian ; Hamers, Robert ( January 2021 , Environmental Science: Nano)

   null (Ed.)

   Among high-valence metal oxides, LiCoO 2 and related materials are of environmental importance because of the rapidly increasing use of these materials as cathodes in lithium ion batteries. Understanding the impact of these materials on aqueous environments relies on understanding their redox chemistry because Co release is dependent on oxidation state. Despite the critical role that redox chemistry plays in cellular homeostasis, the influence of specific biologically relevant electron transporters such as nicotinamide adenine dinucleotide (NADH) and glutathione (GSH) on the transformation of engineered nanoparticles has not been widely considered previously. Here we report an investigation of the interaction of LiCoO 2 nanoparticles with NADH and GSH. Measurements of Co release using inductively coupled plasma-mass spectrometry (ICP-MS) show that exposing LiCoO 2 nanoparticles to either NADH or GSH increases solubilization of cobalt, while corresponding spectroscopic measurements show that NADH is concurrently oxidized to NAD + . To demonstrate that these effects are a consequence the high-valence Co(III) inLiCoO 2 nanoparticles, we performed control experiments using Co(II)-containing Co(OH) 2 and LiCoPO 4 , and dissolved Co 2+ /Li + ions. Additional experiments using molecules of similar structure to NADH and GSH, but that are not reducing agents, confirm that these transformations are driven by redox reactions and not by chelation effects. Our data show that interaction of LiCoO 2 with NADH and GSH induces release Co 2+ ions and alters the redox state of these biologically important transporters. Observation of NADH binding to LiCoO 2 using x-ray photoelectron spectroscopy (XPS) suggests a surface catalyzed reaction. The reciprocal reduction of LiCoO 2 to enable release of Co 2+ and corresponding oxidation of NADH and GSH as model redox-active biomolecules has implications for understanding the biological impacts of high-valence metal oxide nanomaterials. 

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2. Trinuclear and Cyclometallated Organometallic Dinuclear Pt-Pyrazolato Complexes: A Combined Experimental and Theoretical Study

   https://doi.org/10.3390/chemistry5010016  

   Shi, Zhichun ; Li, Fengyu ; Zhao, Hong ; Chakraborty, Indranil ; Chen, Zhongfang ; Raptis, Raphael G. ( March 2023 , Chemistry)

   Two differently substituted pyrazole ligands have been investigated with regard to the topology of their Pt complexes: upon deprotonation, two mononuclear 1:2 PtII-pyrazole complexes—one of the sterically unhindered 4-Me-pzH and one of the bulky 3,5-tBu-pzH (pzH = pyrazole)—yield the corresponding 1:2 PtII-pyrazolato species; the former a triangular, trinuclear metallacycle (1), and the latter a dinuclear, half-lantern species (2) formed via the unprecedented cyclometallation of a butyl group. Stoichiometric oxidation of the colorless PtII2 complex produces the deep-blue, metal–metal bonded PtIII2 analog (3) with a rarely encountered unsymmetrical coordination across the Pt-Pt bond. All three complexes have been characterized by single crystal X-ray structure determination, 1H-NMR, IR, and UV-vis-NIR spectroscopic methods. The XPS spectra of the PtII2 and PtIII2 species are also reported. Density functional theory calculations were carried out to investigate the electronic structure, spectroscopic properties, and chemical bonding of the new complexes. The calculated natural population analysis charges and Wiberg bonding indices indicate a weak σ-interaction in the case of 2 and a formal Pt-Pt single bond in 3. 

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3. Lanthanum-based double perovskite nanoscale motifs as support media for the methanol oxidation reaction

   https://doi.org/10.1039/d1cy01668g  

   McGuire, Scott C. ; Koenigsmann, Christopher ; Chou, Chun Chieh ; Tong, Xiao ; Wong, Stanislaus S. ( January 2022 , Catalysis Science & Technology)

   We have not only analyzed the performance of perovskite oxides as support media for the methanol oxidation reaction (MOR) but also examined the impact and significance of various reaction parameters on their synthesis. Specifically, we have generated (a) La 2 NiMnO 6 , LaMnO 3 , and LaNiO 3 nanocubes with average sizes of ∼200 nm, in addition to a series of La 2 NiMnO 6 (b) nanocubes possessing average sizes of ∼70 and 400 nm and (c) anisotropic nanorods characterized by average diameters of 40–50 nm. All of these samples, when used as supports for Pt nanoparticles, exhibited activities which were at least twice that measured for Pt/C. We have investigated and correlated the effect of varying perovskite (i) composition, (ii) size, and (iii) morphology upon the measured MOR activity. (i) The Ni-containing perovskites yielded generally higher performance metrics than LaMnO 3 alone, suggesting that the presence of Ni is favorable for MOR, a finding supported by a shift in the Pt d -band in XPS. (ii) MOR activity is enhanced as the perovskite size increases in magnitude, suggesting that a growth in the perovskite particle size enables favorable, synergistic metal–support interactions. (iii) A comparison of the nanorods and nanocubes of a similar diameter implied that the one-dimensional morphology achieved a greater activity, a finding which can be attributed not only to the anisotropic structure but also to a desirable surface structure. Overall, these data yield key insights into the tuning of metal–support interactions via rational control over the composition, size, and morphology of the underlying catalyst support. 

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4. The effect of strong metal–support interaction (SMSI) on Pt–Ti/SiO 2 and Pt–Nb/SiO 2 catalysts for propane dehydrogenation

   https://doi.org/10.1039/d0cy00897d  

   Zhu Chen, Johnny ; Gao, Junxian ; Probus, Paige R. ; Liu, Wei ; Wu, Xianli ; Wegener, Evan C. ; Kropf, A. Jeremy ; Zemlyanov, Dmitry ; Zhang, Guanghui ; Yang, Xin ; et al ( September 2020 , Catalysis Science & Technology)

   null (Ed.)

   In this study, we show how strong metal–support interaction (SMSI) oxides in Pt–Nb/SiO 2 and Pt–Ti/SiO 2 affect the electronic, geometric and catalytic properties for propane dehydrogenation. Transmission electron microscopy (TEM), CO chemisorption, and decrease in the catalytic rates per gram Pt confirm that the Pt nanoparticles were partially covered by the SMSI oxides. X-ray absorption near edge structure (XANES), in situ X-ray photoelectron spectroscopy (XPS), and resonant inelastic X-ray scattering (RIXS) showed little change in the energy of Pt valence orbitals upon interaction with SMSI oxides. The catalytic activity per mol of Pt for ethylene hydrogenation and propane dehydrogenation was lower due to fewer exposed Pt sites, while turnover rates were similar. The SMSI oxides, however, significantly increase the propylene selectivity for the latter reaction compared to Pt/SiO 2 . In the SMSI catalysts, the higher olefin selectivity is suggested to be due to the smaller exposed Pt ensemble sites, which result in suppression of the alkane hydrogenolysis reaction; while the exposed atoms remain active for dehydrogenation. 

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5. Host–Guest Interactions and Redox Activity in Layered Conductive Metal–Organic Frameworks

   https://doi.org/10.1021/acs.chemmater.0c01007  

   Stolz, Robert M. ; Mahdavi-Shakib, Akbar ; Frederick, Brian G. ; Mirica, Katherine A. ( July 2020 , Chemistry of Materials)

   This paper describes the identification of specific host–guest interactions between basic gases (NH3, CD3CN, and pyridine) and four topologically similar 2-dimensional (2D) metal–organic frameworks (MOFs) comprising copper and nickel bis(diimine) and bis(dioxolene) linkages of triphenylene-based ligands using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance spectroscopy (EPR), and powder X-ray diffraction (PXRD). This contribution demonstrates that synthetic bottom-up control over surface chemistry of layered MOFs can be used to impart Lewis acidity or a mixture of Brønsted and Lewis acidities, through the choice of organic ligand and metal cation. This work also distinguishes differences in redox activity within this class of MOFs that contribute to their ability to promote electronic transduction of intermolecular interactions. Future design of structure–function relationships within multifunctional 2D MOFs will benefit from the insights this work provides. 

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