Oxygen-Atom Vacancy Formation at Polyoxovanadate Clusters: Homogeneous Models for Reducible Metal Oxides

Petel, Brittney E.; Brennessel, William W.; Matson, Ellen M.

doi:10.1021/jacs.8b05298

Cited by 64 publications

(161 citation statements)

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“…Given the significance of the proposed reduced species in these molecular transformations, extensive efforts have focused on the isolation and characterization of oxygen-deficient POMs. However, to date, examples of well-defined polyoxoanions containing a coordinatively unsaturated, reduced ion, generated via reduction of the parent metal oxide cluster, remain scarce 29,34–37…”

Section: Introductionmentioning

confidence: 99%

Oxygen atom transfer with organofunctionalized polyoxovanadium clusters: O-atom vacancy formation with tertiary phosphanes and deoxygenation of styrene oxide

et al. 2019

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We report a rare example of oxygen atom transfer (OAT) from a polyoxometalate cluster to a series of tertiary phosphanes. Addition of PR 3 (PR 3 ¼ PMe 3 , PMe 2 Ph, PMePh 2 , PPh 3 ) to a neutral methoxidebridged polyoxovanadate-alkoxide (POV-alkoxide) cluster, [V 6 O 7 (OMe) 12 ] 0 , results in isolation of a reduced structure with phosphine oxide datively coordinated to a site-differentiated V III ion. A positive correlation between the steric and electronic properties of the phosphane and the reaction rate was observed. Further investigation of the steric influence of the alkoxy-bridged clusters on OAT was probed through the use of POV clusters with bridging alkoxide ligands of varying chain length ([V 6 O 7 (OR 0 ) 12 ]; R 0 ¼ Et, n Pr). These investigations expose that steric hinderance of the vanadyl moieties has significant influence on the rate of OAT. Finally, we report the reactivity of the reduced POV-alkoxide clusters with styrene oxide, resulting in the deoxygenation of the substrate to generate styrene. This result is the first example of epoxide deoxygenation using homometallic polyoxometalate clusters, demonstrating the potential for mono-vacant Lindqvist clusters to catalyze the removal of oxygen atoms from organic substrates. † Electronic supplementary information (ESI) available: 1 H NMR, ESI-MS (+ve), UV-vis, and IR spectroscopic data for all complexes, crystallographic parameters and BVS calculations of complexes 2-OPMe 3 , 2-OPMe 2 Ph, 2-OPMePh 2 , 2-OPPh 3 , and 4-OPPh 3 , attempted synthesis of 4-OPMePh 2 , 4-OPPh 3 , and propoxide derivatives, 1 H NMR analysis of styrene oxide OAT reactions with 2-OPMe 3 and 4-OPMe 3 . For ESI and crystallographic data (CCDC1914250-1914254) in CIF or other electronic format see Scheme 1 Previously reported synthesis of the mono-vacant neutral cluster, 2-MeCN, via addition of VMes 3 (THF) addition (left) 35 and synthesis of [V 6 O 6 (OMe) 12 OPMe 3 ] (2-OPMe 3 ) via OAT to PMe 3 reported in this work (right). 8036 | Chem. Sci., 2019, 10, 8035-8045 This journal is Scheme 2 Synthesis of complexes 2-OPMe 2 Ph, 2-OPMePh 2 , and 2-OPPh 3 . 8038 | Chem. Sci., 2019, 10, 8035-8045 This journal is Scheme 3 Synthesis of complexes 4-OPMe 3 and 4-OPMe 2 Ph. This journal is Scheme 5 Stoichiometric oxygen atom transfer facilitated by an oxygen-atom vacancy on a POV-alkoxide cluster. 8040 | Chem. Sci., 2019, 10, 8035-8045 This journal is

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Section: Introductionmentioning

confidence: 99%

Oxygen atom transfer with organofunctionalized polyoxovanadium clusters: O-atom vacancy formation with tertiary phosphanes and deoxygenation of styrene oxide

et al. 2019

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“…Recently, Avila et al [ 70 ] performed extensive density functional theory (DFT) calculation and concluded the highest possible oxidation state of all 10 V atoms in decavandate clusters as 5+. The work of Petel et al [ 60 ] provides enough evidence in support of natural presence of OVs in neutral and stable POM clusters. Proper external electric stimuli (in case of RRAMs, it is the bias voltage applied between top and bottom contacts) can further multiply the number of OVs within the POM matrix facilitating fast and reversible redox reaction.…”

Section: Resultsmentioning

confidence: 99%

“…[ 67 ] Furthermore, Petel et al also carried out extensive investigation of a vanadium‐based POM to study presence of OV sites within the molecular cluster. [ 60 ] They too argued that such vacancy sites are formed naturally at the surface of the POM clusters as a result of removal of neutral oxygen atoms from it. The structure then gets reduced through delocalization of electronic charge density.…”

Section: Resultsmentioning

confidence: 99%

“…In recent years, numerous theoretical as well as experimental studies have rendered detailed analysis about nature of POM compositions, their diverse structures, and properties. [ 48,49,54–61 ] Being oxygen‐rich clusters, POMs act as natural electron reservoirs. [ 58 ] Interestingly, POMs are also known as excellent electron acceptor that can reversibly store and release multiple electrons.…”

Section: Introductionmentioning

confidence: 99%

“…[ 58 ] Interestingly, POMs are also known as excellent electron acceptor that can reversibly store and release multiple electrons. [ 54,55,60,61 ] This implies that such clusters can easily undergo multiple reduction (or oxidation) that enables delocalization of large number of electrons throughout the metal–oxide cage (with only minor structural reorganization of the cluster) allowing them to play a vital role as excellent electron conductor in electronic nanoscale devices. [ 48,55 ] Such ability of multiple reductions can also facilitate POM as potential active material for multi‐bit storage cell.…”

Section: Introductionmentioning

confidence: 99%

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Redox‐Active Vanadium‐Based Polyoxometalate as an Active Element in Resistive Switching Based Nonvolatile Molecular Memory

Sterin

Basu

Cahay

et al. 2020

Physica Status Solidi (a)

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Resistive switching (RS)‐based random access memory has been envisaged as a viable alternative to existing memory technology due to its nonvolatility, high switching speed, high endurance/retention, and considerably low operating voltage. Herein, a new uniform, repetitive, and stable RS phenomenon is demonstrated based on very low‐cost two‐terminal metal–insulator–metal stack fabricated using a highly redox‐active vanadium‐based polyoxometalate (POM) molecular clusters, [V10O28]6−—belonging to polyoxovanadate (POV) family. The RS is observed to be unipolar and nonvolatile in nature, and occur at a fairly low operating bias voltage (less than 2 V), making it suitable for low‐power operations. The switching event is attributed to the cycling between formation and rupture of tiny conductive nanofilaments formed due to trapping and detrapping of positively charged ionized oxygen vacancy sites present in the active switching layer of [V10O28]6−. POMs, in their rich abundance, are highly stable early transition‐metal oxide nanosized clusters, capable of storing as well as releasing a large number of electrons. In addition, they can undergo fast and reversible redox reactions (both in solid and liquid electrolyte media) in “stepwise” manner—a property that makes them a promising candidate for ultrafast and multi‐level nonvolatile molecular memory for high‐density data storage. Preliminary investigations on the POV‐based memory cells result in device resistance ratio ≈25, endurance for more than 200 cycles, and stable retention time around 2200 s, in fully open air condition.

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Polyoxometalate‐Single Atom Catalysts (POM‐SACs) in Energy Research and Catalysis

Liu

Streb

2021

Advanced Energy Materials

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have only been explored since the early 21st century, mainly because their identification and characterization has been virtually impossible before, due to a lack of high-resolution instrumentation (such as electron or scanning probe microscopies). [1,4] Beyond classical heterogeneous SACs, much research has recently focused on developing molecular SAC model systems. Here, polyoxometalate-single atom catalysts (POM-SACs) are of enormous interest as these molecular metal oxides could form the link between molecularly well-defined prototypes and technologically relevant solid-state SACs. In this Review, we will provide a brief introduction into the current status in SACs chemistry. We then discuss pioneering studies as well as current research challenges in POM-SACs chemistry with an emphasis on sustainable energy research. Finally, we will identify future areas in POM-SAC research and highlight the bottlenecks which need to be overcome to further develop this field. Classical Single Atom Catalysts Common Anchoring Strategies and Applications of SACsSACs offer the ultimate atomic reactivity, as each single atom is interacting with its environment and can act as catalytic site. [7][8][9] The key to the successful preparation of SACs is to stabilize catalytic metal centers as individual atoms by utilizing hosts/supports featuring strong binding motifs (Figure 1). Early model systems included high specific surface area carbons, [10,11] metal oxides, [12,13] as well as materials with uniform pores and regular structures, such as zeolites, [14] metal organic frameworks (MOFs) [5,[14][15][16][17][18][19] and covalent organic frameworks (COFs). [20,21] Stabilization of single-atoms on supports requires a support-surface with specific anchoring sites, such as coordinatively unsaturated surface atoms (e.g., O 2− , OH − ), surface vacancies or heteroatom dopants (e.g., N, P, S, and halogens). The SACs can be stabilized on the support surface by covalent or ionic interactions, or by geometric enclosure in small pores. Each anchoring mode offers several benefits and challenges. For instance, the coordination of a single metal atom to surface oxo ligands makes the single-atom accessible from the outside, e.g., for binding of a substrate. However, it also leads to high surface-energy and destabilization of the single-atom, so that leaching, or agglomeration are possible. In contrast, Single atom catalysts-SACs-have received intense interest in sustainable energy research due to their enormous application potential and broad catalytic scope. In particular, SACs anchored on molecular metal oxides-polyoxometalates (POMs)-offer unrivalled possibilities as models to understand the function of these complex systems on the atomic level. Research questions which are difficult to address for classical heterogeneous SACs can be addressed by experiment and theory using POM-SACs as prototype catalysts. This review reviews the emerging field of POM-SAC research with a focus on fundamental properties and their application in energy conversion...

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Oxygen-Atom Vacancy Formation at Polyoxovanadate Clusters: Homogeneous Models for Reducible Metal Oxides

Cited by 64 publications

References 52 publications

Oxygen atom transfer with organofunctionalized polyoxovanadium clusters: O-atom vacancy formation with tertiary phosphanes and deoxygenation of styrene oxide

Oxygen atom transfer with organofunctionalized polyoxovanadium clusters: O-atom vacancy formation with tertiary phosphanes and deoxygenation of styrene oxide

Redox‐Active Vanadium‐Based Polyoxometalate as an Active Element in Resistive Switching Based Nonvolatile Molecular Memory

Polyoxometalate‐Single Atom Catalysts (POM‐SACs) in Energy Research and Catalysis

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