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Dagar M, Brennessel WW, Matson EM. Elucidation of Design Criteria for V-based Redox Mediators: Structure-Function Relationships that Dictate Rates of Heterogeneous Electron Transfer. Chemistry 2024:e202400764. [PMID: 38574277 DOI: 10.1002/chem.202400764] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2024] [Revised: 03/30/2024] [Accepted: 04/04/2024] [Indexed: 04/06/2024]
Abstract
Redox mediators are attractive solutions for addressing the stringent kinetic stipulations required for efficient energy conversion processes. In this work, we compare the electrochemical properties of four vanadium complexes, namely [V(acac)3], [V6O7(OMe)12], [nBu4N]3[V6O13(TRISNO2)2], and [nBu4N]5[V18O46(NO3)] in non-aqueous solutions on glassy carbon electrodes. The goal of this study is to investigate the electron transfer kinetics and diffusivity of these compounds under identical experimental conditions to develop an understanding of structure-function relationships that dictate the physicochemical properties of vanadium oxide assemblies. Complex selection was dictated by two criteria - (1) nuclearity of the transition metal complexes (2) distribution of electron density in the native electronic configuration. Our analyses establish that electronic communication between metal centers significantly impacts charge transfer kinetics of these vanadium-based compounds.
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Affiliation(s)
- Mamta Dagar
- University of Rochester, Department of Chemistry, Rochester, NY 14627, USA
| | | | - Ellen M Matson
- University of Rochester, Department of Chemistry, Rochester, NY 14627, USA
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Dagar M, Dissanyake DMMM, Kesler DN, Corr M, McPherson JD, Brennessel WW, McKone JR, Matson EM. Improved solubility of titanium-doped polyoxovanadate charge carriers for symmetric non-aqueous redox flow batteries. Dalton Trans 2023; 53:93-104. [PMID: 38038996 DOI: 10.1039/d3dt03642a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2023]
Abstract
Non-aqueous redox flow batteries constitute a promising solution for grid-scale energy storage due to the ability to achieve larger cell voltages than can be readily accessed in water. However, their widespread application is limited by low solubility of the electroactive species in organic solvents. In this work, we demonstrate that organic functionalization of titanium-substituted polyoxovanadate-alkoxide clusters increases the solubility of these assemblies over that of their homoleptic congeners by a factor of >10 in acetonitrile. Cyclic voltammetry, chronoamperometry, and charge-discharge cycling experiments are reported, assessing the electrochemical properties of these clusters relevant to their ability to serve as multielectron charge carriers for energy storage. The kinetic implications of ligand variation are assessed, demonstrating the role of ligand structure on the diffusivity and heterogeneous rates of electron transfer in mixed-metal charge carriers. Our results offer new insights into the impact of structural modifications on the physicochemical properties of these assemblies.
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Affiliation(s)
- Mamta Dagar
- Department of Chemistry, University of Rochester, Rochester, NY 14627, USA.
| | | | - Daniel N Kesler
- Department of Chemistry, University of Rochester, Rochester, NY 14627, USA.
| | - Molly Corr
- Department of Chemistry, University of Rochester, Rochester, NY 14627, USA.
| | - Joshua D McPherson
- Department of Chemistry, University of Rochester, Rochester, NY 14627, USA.
| | | | - James R McKone
- Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Ellen M Matson
- Department of Chemistry, University of Rochester, Rochester, NY 14627, USA.
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Schreiber E, Brennessel WW, Matson EM. Charge-State Dependence of Proton Uptake in Polyoxovanadate-alkoxide Clusters. Inorg Chem 2022; 61:4789-4800. [PMID: 35293218 PMCID: PMC8965876 DOI: 10.1021/acs.inorgchem.1c02937] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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Here, we present
an investigation of the thermochemistry of proton
uptake in acetonitrile across three charge states of a polyoxovanadate-alkoxide
(POV-alkoxide) cluster, [V6O7(OMe)12]n (n = 2–, 1–,
and 0). The vanadium oxide assembly studied features bridging sites
saturated by methoxide ligands, isolating protonation to terminal
vanadyl moieties. Exposure of [V6O7(OMe)12]n to organic acids of appropriate
strength results in the protonation of a terminal V=O bond,
generating the transient hydroxide-substituted POV-alkoxide cluster
[V6O6(OH)(OMe)12]n+1. Evidence for this intermediate proved elusive in our initial
report, but here we present the isolation of a divalent anionic cluster
that features hydrogen bonding to dimethylammonium at the terminal
oxo site. Degradation of the protonated species results in the formation
of equimolar quantities of one-electron-oxidized and oxygen-atom-efficient
complexes, [V6O7(OMe)12]n+1 and [V6O6(OMe)12]n+1. While analogous reactivity was
observed across the three charge states of the cluster, a dependence
on the acid strength was observed, suggesting that the oxidation state
of the vanadium oxide assembly influences the basicity of the cluster
surface. Spectroscopic investigations reveal sigmoidal relationships
between the acid strength and cluster conversion across the redox
series, allowing for determination of the proton affinity of the surface
of the cluster in all three charge states. The fully reduced cluster
is found to be the most basic, with higher oxidation states of the
assembly possessing substantially reduced proton affinities (∼7
pKa units per electron). These results
further our understanding of the site-specific reactivity of terminal M=O bonds with protons in an organic solvent,
revealing design criteria for engineering functional surfaces of metal
oxide materials of relevance to energy storage and conversion. Experimental determination of the surface
basicity of polyoxovanadate-alkoxide
clusters across three oxidation states reveals a charge-state dependence
of proton uptake in molecular, organofunctionalized vanadium oxide
assemblies.
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Affiliation(s)
- Eric Schreiber
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - William W Brennessel
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Ellen M Matson
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
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Fertig AA, Rabbani SMG, Koch MD, Brennessel WW, Miró P, Matson EM. Physicochemical implications of surface alkylation of high-valent, Lindqvist-type polyoxovanadate-alkoxide clusters. NANOSCALE 2021; 13:6162-6173. [PMID: 33734254 DOI: 10.1039/d0nr09201k] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We report a rare example of the direct alkylation of the surface of a plenary polyoxometalate cluster by leveraging the increased nucleophilicity of vanadium oxide assemblies. Addition of methyl trifluoromethylsulfonate (MeOTf) to the parent polyoxovanadate cluster, [V6O13(TRIOLR)2]2- (TRIOL = tris(hydroxymethyl)methane; R = Me, NO2) results in functionalisation of one or two bridging oxide ligands of the cluster core to generate [V6O12(OMe)(TRIOLR)2]1- and [V6O11(OMe)2(TRIOLR)2]2-, respectively. Comparison of the electronic absorption spectra of the functionalised and unfunctionalised derivatives indicates the decreased overall charge of the complex results in a decrease in the energy required for ligand to metal charge transfer events to occur, while simultaneously mitigating the inductive effects imposed by the capping TRIOL ligand. Electrochemical analysis of the family of organofunctionalised polyoxovanadate clusters reveals the relationship of ligand environment and the redox properties of the cluster core: increased organofunctionalisation of the surface of the vanadium oxide assembly translates to anodic shifts in the reduction events of the Lindqvist ion. Overall, this work provides insight into the electronic effects induced upon atomically precise modifications to the surface structure of nanoscopic, redox-active metal oxide assemblies.
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Affiliation(s)
- Alex A Fertig
- Department of Chemistry, University of Rochester, Rochester, NY 14627, USA.
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Chakraborty S, Petel BE, Schreiber E, Matson EM. Atomically precise vanadium-oxide clusters. NANOSCALE ADVANCES 2021; 3:1293-1318. [PMID: 36132875 PMCID: PMC9419539 DOI: 10.1039/d0na00877j] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Accepted: 01/19/2021] [Indexed: 05/08/2023]
Abstract
Polyoxovanadate (POV) clusters are an important subclass of polyoxometalates with a broad range of molecular compositions and physicochemical properties. One relatively underdeveloped application of these polynuclear assemblies involves their use as atomically precise, homogenous molecular models for bulk metal oxides. Given the structural and electronic similarities of POVs and extended vanadium oxide materials, as well as the relative ease of modifying the homogenous congeners, investigation of the chemical and physical properties of pristine and modified cluster complexes presents a method toward understanding the influence of structural modifications (e.g. crystal structure/phase, chemical makeup of surface ligands, elemental dopants) on the properties of extended solids. This review summarises recent advances in the use of POV clusters as atomically precise models for bulk metal oxides, with particular focus on the assembly of vanadium oxide clusters and the consequences of altering the molecular composition of the assembly via organofunctionalization and the incorporation of elemental "dopants".
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Affiliation(s)
| | - Brittney E Petel
- University of Rochester, Department of Chemistry Rochester NY 14627 USA
| | - Eric Schreiber
- University of Rochester, Department of Chemistry Rochester NY 14627 USA
| | - Ellen M Matson
- University of Rochester, Department of Chemistry Rochester NY 14627 USA
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6
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Accessing decavanadate chemistry with tris(hydroxymethyl)aminomethane, and evaluation of methylene blue bleaching. Polyhedron 2020. [DOI: 10.1016/j.poly.2020.114414] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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VanGelder LE, Schreiber E, Wind ML, Limberg C, Matson EM. Investigation of Cubic Fe 4 M 4 Frameworks for Application in Nonaqueous Energy Storage. Chemistry 2019; 25:14421-14429. [PMID: 31497908 DOI: 10.1002/chem.201903360] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Revised: 08/27/2019] [Indexed: 11/09/2022]
Abstract
Multimetallic complexes have recently seen increased attention as next-generation charge carriers for nonaqueous redox flow batteries. Herein, we report the electrochemical performance of a molecular iron-molybdenum oxido complex, {[(Me3 TACN)Fe][μ-(MoO4 κ3 O,O',O")]}4 (Fe4 Mo4 O16 ). In symmetric battery charging schematics, Fe4 Mo4 O16 facilitates reversible two-electron storage with coulombic efficiencies >99 % over 100 cycles (5 days) with no molecular decomposition and minimal capacity fade. Energy efficiency throughout cycling remained high (∼82 %), as a result of the rapid electron-transfer kinetics observed for each of the complex's four redox events. We also report the synthesis of the analogous synthetic frameworks featuring tungstate vertices or bridging-sulfide moieties, revealing key observations relevant to structure-function relationships and design criteria for these types of heterometallic ensembles.
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Affiliation(s)
- Lauren E VanGelder
- Department of Chemistry, University of Rochester, Rochester, NY, 14627, USA
| | - Eric Schreiber
- Department of Chemistry, University of Rochester, Rochester, NY, 14627, USA
| | - Marie-Louise Wind
- Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Strasse 2, 12489, Berlin, Germany
| | - Christian Limberg
- Institut für Chemie, Humboldt-Universität zu Berlin, Brook-Taylor-Strasse 2, 12489, Berlin, Germany
| | - Ellen M Matson
- Department of Chemistry, University of Rochester, Rochester, NY, 14627, USA
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VanGelder LE, Pratt HD, Anderson TM, Matson EM. Surface functionalization of polyoxovanadium clusters: generation of highly soluble charge carriers for nonaqueous energy storage. Chem Commun (Camb) 2019; 55:12247-12250. [DOI: 10.1039/c9cc05380h] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Here, we demonstrate the effects of surface functionalization on a tunable series of nano-sized electron shuttles toward improving their function in nonaqueous energy storage.
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