1
|
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
![]()
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.
Collapse
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
| |
Collapse
|
2
|
Fertig AA, Brennessel WW, McKone JR, Matson EM. Concerted Multiproton-Multielectron Transfer for the Reduction of O 2 to H 2O with a Polyoxovanadate Cluster. J Am Chem Soc 2021; 143:15756-15768. [PMID: 34528799 DOI: 10.1021/jacs.1c07076] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The concerted transfer of protons and electrons enables the activation of small-molecule substrates by bypassing energetically costly intermediates. Here, we present the synthesis and characterization of several hydrogenated forms of an organofunctionalized vanadium oxide assembly, [V6O13(TRIOLNO2)2]2-, and their ability to facilitate the concerted transfer of protons and electrons to O2. Electrochemical analysis reveals that the fully reduced cluster is capable of mediating 2e-/2H+ transfer reactions from surface hydroxide ligands, with an average bond dissociation free energy (BDFE) of 61.6 kcal/mol. Complementary stoichiometric experiments with hydrogen-atom-accepting reagents of established bond strengths confirm that the electrochemically established BDFE predicts the 2H+/2e- transfer reactivity of the assembly. Finally, the reactivity of the reduced polyoxovanadate toward O2 reduction is summarized; our results indicate a stepwise reduction of the substrate, proceeding through H2O2 en route to the formation of H2O. Kinetic isotope effect experiments confirm the participation of hydrogen transfer in the rate-determining step of both the reduction of O2 and H2O2. This work constitutes the first example of hydrogen atom transfer for small-molecule activation with reduced polyoxometalates, where both electron and proton originate from the cluster.
Collapse
Affiliation(s)
- Alex A Fertig
- 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
| | - James R McKone
- Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, United States
| | - Ellen M Matson
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| |
Collapse
|
3
|
Younis AM, El‐Gamil MM, Rakha TH, Abu El‐Reash GM. Iron(III), copper(II), cadmium(II), and mercury(II) complexes of isatin carbohydrazone Schiff base ligand (H
3
L): Synthesis, characterization, X‐ray diffraction, cyclic voltammetry, fluorescence, density functional theory, biological activity, and molecular docking studies. Appl Organomet Chem 2021. [DOI: 10.1002/aoc.6250] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Adel M. Younis
- Chemistry Department, Faculty of Science Mansoura University PO Box 70 Mansoura Egypt
| | - Mohammed M. El‐Gamil
- Department of Toxic and Narcotic Drug, Forensic Medicine, Mansoura Laboratory, Medico‐Legal Organization Ministry of Justice Mansoura Egypt
| | - Tawfik H. Rakha
- Chemistry Department, Faculty of Science Mansoura University PO Box 70 Mansoura Egypt
| | - Gaber M. Abu El‐Reash
- Chemistry Department, Faculty of Science Mansoura University PO Box 70 Mansoura Egypt
| |
Collapse
|
4
|
Lian L, Chen X, Yi X, Liu Y, Chen W, Zheng A, Miras HN, Song YF. Modulation of Self-Separating Molecular Catalysts for Highly Efficient Biomass Transformations. Chemistry 2020; 26:11900-11908. [PMID: 32329538 PMCID: PMC7540606 DOI: 10.1002/chem.202001451] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Indexed: 11/10/2022]
Abstract
The energetically viable fabrication of stable and highly efficient solid acid catalysts is one of the key steps in large‐scale transformation processes of biomass resources. Herein, the covalent modification of the classical Dawson polyoxometalate (POMs) with sulfonic acids (‐SO3H) is reported by grafting sulfonic acid groups on the POM's surface followed by oxidation of (3‐mercaptopropyl)trimethoxysilane. The acidity of TBA6‐P2W17‐SO3H (TBA=tetrabutyl ammonium) has been demonstrated by using 31P NMR spectroscopy, clearly indicating the presence of strong Brønsted acid sites. The presence of TBA counterions renders the solid acid catalyst as a promising candidate for phase transfer catalytic processes. The TBA6‐P2W17‐SO3H shows remarkable activity and selectivity, excellent stability, and great substrate compatibility for the esterification of free fatty acids (FFA) with methanol and conversion into biodiesel at 70 °C with >98 % conversion of oleic acid in 20 min. The excellent catalytic performance can be attributed to the formation of a catalytically active emulsion, which results in a uniform catalytic behavior during the reaction, leading to efficient interaction between the substrate and the active sites of the catalyst. Most importantly, the catalyst can be easily recovered and reused without any loss of its catalytic activity owing to its excellent phase transfer properties. This work offers an efficient and cost‐effective strategy for large‐scale biomass conversion applications.
Collapse
Affiliation(s)
- Lifei Lian
- State Key Laboratory of Chemical Resource Engineering, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing, 100029, P.R. China
| | - Xiang Chen
- State Key Laboratory of Chemical Resource Engineering, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing, 100029, P.R. China
| | - Xianfeng Yi
- Wuhan Center for Magnetic Resonance, Key Laboratory of, Magnetic Resonance in Biological Systems, State Key Laboratory of, Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, 430071, P.R. China
| | - Yubing Liu
- State Key Laboratory of Chemical Resource Engineering, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing, 100029, P.R. China
| | - Wei Chen
- State Key Laboratory of Chemical Resource Engineering, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing, 100029, P.R. China
| | - Anmin Zheng
- Wuhan Center for Magnetic Resonance, Key Laboratory of, Magnetic Resonance in Biological Systems, State Key Laboratory of, Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan, 430071, P.R. China
| | - Haralampos N Miras
- WestCHEM, School of Chemistry, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Yu-Fei Song
- State Key Laboratory of Chemical Resource Engineering, Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing, 100029, P.R. China
| |
Collapse
|