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Scaiano JC, Wang B, Bourgonje CR, Yaghmaei M. The nitro to amine reduction: from millions of tons to single molecule studies. PURE APPL CHEM 2023; 95:913-920. [PMID: 38013690 PMCID: PMC10505479 DOI: 10.1515/pac-2023-0111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
Palladium nanostructures are interesting heterogeneous catalysts because of their high catalytic activity in a vast range of highly relevant reactions such as cross couplings, dehalogenations, and nitro-to-amine reductions. In the latter case, the catalyst Pd@GW (palladium on glass wool) shows exceptional performance and durability in reducing nitrobenzene to aniline under ambient conditions in aqueous solutions. To enhance our understanding, we use a combination of optical and electron microscopy, in-flow single molecule fluorescence, and bench chemistry combined with a fluorogenic system to develop an intimate understanding of Pd@GW in nitro-to-amine reductions. We fully characterize our catalyst in situ using advanced microscopy techniques, providing deep insights into its catalytic performance. We also explore Pd cluster migration on the surface of the support under flow conditions, providing insights into the mechanism of catalysis. We show that even under flow, Pd migration from anchoring sites seems to be minimal over 4 h, with the catalyst stability assisted by APTES anchoring.
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Affiliation(s)
- Juan C. Scaiano
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, ONK1N 6N5, Canada
| | - Bowen Wang
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, ONK1N 6N5, Canada
| | - Connor R. Bourgonje
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, ONK1N 6N5, Canada
| | - Mahzad Yaghmaei
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, ONK1N 6N5, Canada
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Gu K, Liu S, Liu C. Surface Preparation for Single-Molecule Fluorescence Imaging in Organic Solvents. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:15848-15857. [PMID: 36475684 DOI: 10.1021/acs.langmuir.2c02828] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
The development of single-molecule techniques provides opportunities to investigate the properties and heterogeneities of individual molecules, which are almost impossible to be obtained in ensemble measurements. Recently, single-molecule fluorescence microscopy is being applied more and more to study chemical reactions in organic solvents. However, little has been done to optimize the surface preparation procedures for single-molecule fluorescence imaging in organic solvents. In this work, we developed a method to prepare the surface for single-molecule fluorescence imaging in organic solvents with a well-controlled surface density of chemically immobilized dye molecules and a low density of nonspecifically adsorbed impurities. We also compared the surfaces prepared by two different procedures and studied the impacts of the polarities of the solvent and the surface functionality on the quality of prepared surface. We found that higher polarities of both the solvent and the surface functionality provided better control of the surface density of chemically immobilized dyes and helped reduce the nonspecific adsorption of both dyes and fluorescent impurities in organic solvents. We further performed single-molecule fluorescence imaging in DMF and investigated the photophysical properties of dyes and fluorescent impurities, which could be used to filter out false counts in single-molecule fluorescence measurements.
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Affiliation(s)
- Kai Gu
- School of Polymer Science and Polymer Engineering, The University of Akron, Akron, Ohio 44325, United States
| | - Shuzhen Liu
- School of Polymer Science and Polymer Engineering, The University of Akron, Akron, Ohio 44325, United States
| | - Chunming Liu
- School of Polymer Science and Polymer Engineering, The University of Akron, Akron, Ohio 44325, United States
- Department of Chemistry, The University of Akron, Akron, Ohio 44325, United States
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Wang B, Lanterna AE, Scaiano JC. Mechanistic Insights on the Semihydrogenation of Alkynes over Different Nanostructured Photocatalysts. ACS Catal 2021. [DOI: 10.1021/acscatal.0c05233] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Bowen Wang
- Department of Chemistry and Biomolecular Sciences and Centre for Advanced Materials Research, University of Ottawa, Ottawa K1N 6N5, Ontario, Canada
| | - Anabel E. Lanterna
- Department of Chemistry and Biomolecular Sciences and Centre for Advanced Materials Research, University of Ottawa, Ottawa K1N 6N5, Ontario, Canada
| | - Juan C. Scaiano
- Department of Chemistry and Biomolecular Sciences and Centre for Advanced Materials Research, University of Ottawa, Ottawa K1N 6N5, Ontario, Canada
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Menges JA, Grandjean A, Clasen A, Jung G. Kinetics of Palladium(0)‐Allyl Interactions in the Tsuji‐Trost Reaction, derived from Single‐Molecule Fluorescence Microscopy. ChemCatChem 2020. [DOI: 10.1002/cctc.202000032] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Johannes A. Menges
- Department of Biophysical Chemistry Saarland University Building B2 2 66123 Saarbrücken Germany
| | - Alexander Grandjean
- Department of Biophysical Chemistry Saarland University Building B2 2 66123 Saarbrücken Germany
| | - Anne Clasen
- Department of Biophysical Chemistry Saarland University Building B2 2 66123 Saarbrücken Germany
| | - Gregor Jung
- Department of Biophysical Chemistry Saarland University Building B2 2 66123 Saarbrücken Germany
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Easter QT, Blum SA. Organic and Organometallic Chemistry at the Single-Molecule, -Particle, and -Molecular-Catalyst-Turnover Level by Fluorescence Microscopy. Acc Chem Res 2019; 52:2244-2255. [PMID: 31310095 DOI: 10.1021/acs.accounts.9b00219] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Mechanistic studies have historically played a key role in the discovery and optimization of reactions in organic and organometallic chemistry. However, even apparently simple organic and organometallic transformations may have surprisingly complicated multistep mechanisms, increasing the difficulty of extracting this mechanistic information. The resulting reaction intermediates often constitute a small fraction of the total reaction mixture, for example, creating a long-term analytical challenge of detection. This challenge is particularly pronounced in cases where the positions of intermediates on the reaction energy surface mean that they do not "build up" to the quantities needed for observation by traditional ensemble analytical tools. Thus, their existence and single-step elementary reactivity cannot be studied directly. New approaches for obtaining this otherwise-missing mechanistic information are therefore needed. Single-turnover, single-molecule, single-particle, and other subensemble fluorescence microscopy techniques are ideally suited for this role because of their sensitivity and spatiotemporal resolution. Inspired by the robust development of single-molecule fluorescence microscopy tools for studying enzyme catalysis, our laboratory has developed analogous fluorescence microscopy techniques to overcome mechanistic challenges in synthetic chemistry, with sensitivity as high as the single-complex, single-turnover, and single-molecule level. These techniques free the experimenter from the previous restriction that intermediates must "build up" to quantities needed for detection by ensemble analytical tools and are suited to systems where synchronization through flash photolysis or stopped flow would be inconvenient or inaccessible. In this process, the techniques transform certain previously "unobservable" intermediates and their elementary single-step reactivities into "observable" ones through sensitive and selective spectral handles. Our program has focused on imaging reactions in small-molecule, organic, and polymer synthetic chemistry with an accent on the reactivity of molecular transition metal complexes and catalysts. Our laboratory initiated studies in this area in 2008 with the imaging of individual palladium complexes that were tagged with spectator fluorophores. To enable imaging, we started with fluorophore selection and development, overcame challenges with imaging in organic solvents, and developed strategies compatible with air-sensitive chemistry and concentrations of reagents generally used in small-molecule synthesis. These studies grew to include characterization of previously unknown organometallic intermediates in the synthesis of organozinc reagents and the direct study of their elementary-step reactivity. The ability to directly observe this behavior generated predictive power for selecting salts that accelerated organozinc reagent formation in synthesis, including salts that had not yet been reported synthetically. In 2017 we also developed the first single-turnover imaging of molecular (chemo)catalysts, which through the technique's spatiotemporal resolution revealed abruptly time-variable polymerization kinetics wherein molecular ruthenium ring-opening metathesis polymerization (ROMP) catalysts changed rates independently from other catalysts less than 1 μm away. Individual catalytic turnovers, each corresponding to one single-chain-elongation reaction arising from insertion of single ROMP or enyne monomers at individual Grubbs II molecular ruthenium catalysts, were spatiotemporally resolved as green flashes in growing polymers. In this Account, we discuss the development of this technique from idea to application, including challenges overcome and strategies created to image synthetic organic and organometallic molecular chemistry at the highest levels of detection sensitivity. We also describe challenges not yet solved and provide an outlook for this growing field at the intersection of microscopy and synthetic/molecular chemistry.
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Affiliation(s)
- Quinn T. Easter
- Department of Chemistry, University of California, Irvine, California 92697−2025, United States
| | - Suzanne A. Blum
- Department of Chemistry, University of California, Irvine, California 92697−2025, United States
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Abstract
Abstract
In the new millennium the well-established paradigms of organic photochemistry have come alive as the basis for a wide range of synthetic methodologies that take advantage of the enhanced redox properties of excited states. While many strategies have been developed using rare, expensive and non-reusable catalysts, the road forward should include catalysts based on more abundant elements and reusable materials. This green road leads to the exploration of heterogeneous systems that can be eventually adapted for flow photocatalysis, and also adopted for the solution of environmental problems such as water treatment and fuel generation using solar radiation. If heterogeneous photocatalysis can play a role in supplying solutions to drug synthesis, energy and potable water supplies, then photochemistry will have an unprecedented societal impact.
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Affiliation(s)
- Juan C. Scaiano
- Department of Chemistry and Biomolecular Science, Centre for Advanced Materials Research (CAMaR) , University of Ottawa , 10 Marie Curie, Ottawa , ON K1N 6N5 , Canada
| | - Anabel E. Lanterna
- Department of Chemistry and Biomolecular Science, Centre for Advanced Materials Research (CAMaR) , University of Ottawa , 10 Marie Curie, Ottawa , ON K1N 6N5 , Canada
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Zou N, Chen G, Mao X, Shen H, Choudhary E, Zhou X, Chen P. Imaging Catalytic Hotspots on Single Plasmonic Nanostructures via Correlated Super-Resolution and Electron Microscopy. ACS NANO 2018; 12:5570-5579. [PMID: 29860829 DOI: 10.1021/acsnano.8b01338] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Surface-plasmon (SP) enhanced catalysis on plasmonic nanostructures brings opportunities to increase catalytic efficiency and alter catalytic selectivity. Understanding the underlying mechanism requires quantitative measurements of catalytic enhancement on these nanostructures, whose intrinsic structural heterogeneity presents experimental challenges. Using correlated super-resolution fluorescence microscopy and electron microscopy, here we report a quantitative visualization of SP-enhanced catalytic activity at the nanoscale within single plasmonic nanostructures. We focus on two Au- and Ag-based linked nanostructures that present plasmonic hotspots at nanoscale gaps. Spatially localized higher reaction rates at these gaps vs nongap regions report the SP-induced catalytic enhancements, which show direct correlations with the nanostructure geometries and local electric field enhancements. Furthermore, the catalytic enhancement scales quadratically with the local actual light intensity, attributable to hot electron involvement in the catalytic enhancement mechanism. These discoveries highlight the effectiveness of correlated super-resolution and electron microscopy in interrogating nanoscale catalytic properties.
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Affiliation(s)
- Ningmu Zou
- Department of Chemistry and Chemical Biology , Cornell University , Ithaca , New York 14853 , United States
| | - Guanqun Chen
- Department of Chemistry and Chemical Biology , Cornell University , Ithaca , New York 14853 , United States
| | - Xianwen Mao
- Department of Chemistry and Chemical Biology , Cornell University , Ithaca , New York 14853 , United States
| | - Hao Shen
- Department of Chemistry and Chemical Biology , Cornell University , Ithaca , New York 14853 , United States
| | - Eric Choudhary
- Department of Chemistry and Chemical Biology , Cornell University , Ithaca , New York 14853 , United States
| | - Xiaochun Zhou
- Department of Chemistry and Chemical Biology , Cornell University , Ithaca , New York 14853 , United States
| | - Peng Chen
- Department of Chemistry and Chemical Biology , Cornell University , Ithaca , New York 14853 , United States
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Wang B, Lanterna AE, Scaiano JC. Click Chemistry: Mechanistic Insights into the Role of Amines Using Single-Molecule Spectroscopy. ACS Catal 2017. [DOI: 10.1021/acscatal.7b03150] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Bowen Wang
- Department of Chemistry and
Biomolecular Sciences and Centre for Advanced Materials Research (CAMaR), University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5, Canada
| | - Anabel E. Lanterna
- Department of Chemistry and
Biomolecular Sciences and Centre for Advanced Materials Research (CAMaR), University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5, Canada
| | - Juan C. Scaiano
- Department of Chemistry and
Biomolecular Sciences and Centre for Advanced Materials Research (CAMaR), University of Ottawa, 10 Marie Curie, Ottawa, Ontario K1N 6N5, Canada
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