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Yan Y, Meng Y, Miu K, Wenk J, Anastasio C, Spinney R, Tang CJ, Xiao R. Direct Determination of Absolute Radical Quantum Yields in Hydroxyl and Sulfate Radical-Based Treatment Processes. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:8966-8975. [PMID: 38722667 DOI: 10.1021/acs.est.4c00246] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2024]
Abstract
The absolute radical quantum yield (Φ ) is a critical parameter to evaluate the efficiency of radical-based processes in engineered water treatment. However, measuring Φ is fraught with challenges, as current quantification methods lack selectivity, specificity, and anti-interference capabilities, resulting in significant error propagation. Herein, we report a direct and reliable time-resolved technique to determine Φ at pH 7.0 for commonly used radical precursors in advanced oxidation processes. For H2O2 and peroxydisulfate (PDS), the values of Φ •OH and Φ SO 4 • - at 266 nm were measured to be 1.10 ± 0.01 and 1.46 ± 0.05, respectively. For peroxymonosulfate (PMS), we developed a new approach to determine Φ • OH PMS with terephthalic acid as a trap-and-trigger probe in the nonsteady state system. For the first time, the Φ • OH PMS value was measured to be 0.56 by the direct method, which is stoichiometrically equal to Φ SO 4 • - PMS (0.57 ± 0.02). Additionally, radical formation mechanisms were elucidated by density functional theory (DFT) calculations. The theoretical results showed that the highest occupied molecular orbitals of the radical precursors are O-O antibonding orbitals, facilitating the destabilization of the peroxy bond for radical formation. Electronic structures of these precursors were compared, aiming to rationalize the tendency of the Φ values we observed. Overall, this time-resolved technique with specific probes can be used as a reliable tool to determine Φ , serving as a scientific basis for the accurate performance evaluation of diverse radical-based treatment processes.
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Affiliation(s)
- Yiqi Yan
- Institute of Environmental Engineering, School of Metallurgy and Environment, Central South University, Changsha 410083, China
- Chinese National Engineering Research Center for Control & Treatment of Heavy Metal Pollution, Changsha 410083, China
| | - Yunxiang Meng
- Institute of Environmental Engineering, School of Metallurgy and Environment, Central South University, Changsha 410083, China
- Chinese National Engineering Research Center for Control & Treatment of Heavy Metal Pollution, Changsha 410083, China
| | - Kanying Miu
- Institute of Environmental Engineering, School of Metallurgy and Environment, Central South University, Changsha 410083, China
- Chinese National Engineering Research Center for Control & Treatment of Heavy Metal Pollution, Changsha 410083, China
| | - Jannis Wenk
- Department of Chemical Engineering, Water Innovation & Research Centre (WIRC@Bath), University of Bath, Bath BA2 7AY, U.K
| | - Cort Anastasio
- Department of Land, Air, and Water Resource, University of California, Davis, California 95616, United States
| | - Richard Spinney
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States
| | - Chong-Jian Tang
- Institute of Environmental Engineering, School of Metallurgy and Environment, Central South University, Changsha 410083, China
- Chinese National Engineering Research Center for Control & Treatment of Heavy Metal Pollution, Changsha 410083, China
| | - Ruiyang Xiao
- Institute of Environmental Engineering, School of Metallurgy and Environment, Central South University, Changsha 410083, China
- Chinese National Engineering Research Center for Control & Treatment of Heavy Metal Pollution, Changsha 410083, China
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Kobus M, Friedrich T, Zorn E, Burmeister N, Maison W. Medicinal Chemistry of Drugs with N-Oxide Functionalities. J Med Chem 2024; 67:5168-5184. [PMID: 38549449 PMCID: PMC11017254 DOI: 10.1021/acs.jmedchem.4c00254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Revised: 03/08/2024] [Accepted: 03/21/2024] [Indexed: 04/12/2024]
Abstract
Molecules with N-oxide functionalities are omnipresent in nature and play an important role in Medicinal Chemistry. They are synthetic or biosynthetic intermediates, prodrugs, drugs, or polymers for applications in drug development and surface engineering. Typically, the N-oxide group is critical for biomedical applications of these molecules. It may provide water solubility or decrease membrane permeability or immunogenicity. In other cases, the N-oxide has a special redox reactivity which is important for drug targeting and/or cytotoxicity. Many of the underlying mechanisms have only recently been discovered, and the number of applications of N-oxides in the healthcare field is rapidly growing. This Perspective article gives a short summary of the properties of N-oxides and their synthesis. It also provides a discussion of current applications of N-oxides in the biomedical field and explains the basic molecular mechanisms responsible for their biological activity.
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Affiliation(s)
- Michelle Kobus
- Universität Hamburg, Department of Chemistry, Bundesstrasse 45, 20146 Hamburg, Germany
| | - Timo Friedrich
- Universität Hamburg, Department of Chemistry, Bundesstrasse 45, 20146 Hamburg, Germany
| | - Eilika Zorn
- Universität Hamburg, Department of Chemistry, Bundesstrasse 45, 20146 Hamburg, Germany
| | - Nils Burmeister
- Universität Hamburg, Department of Chemistry, Bundesstrasse 45, 20146 Hamburg, Germany
| | - Wolfgang Maison
- Universität Hamburg, Department of Chemistry, Bundesstrasse 45, 20146 Hamburg, Germany
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Niklas JE, Studvick CM, Bacsa J, Popov IA, La Pierre HS. Ligand Control of Oxidation and Crystallographic Disorder in the Isolation of Hexavalent Uranium Mono-Oxo Complexes. Inorg Chem 2023; 62:2304-2316. [PMID: 36668669 DOI: 10.1021/acs.inorgchem.2c04056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The development of high-valent transuranic chemistry requires robust methodologies to access and fully characterize reactive species. We have recently demonstrated that the reducing nature of imidophosphorane ligands supports the two-electron oxidation of U4+ to U6+ and established the use of this ligand to evaluate the inverse-trans-influence (ITI) in actinide metal-ligand multiple bond (MLMB) complexes. To extend this methodology and analysis to transuranic complexes, new small-scale synthetic strategies and lower-symmetry ligand derivatives are necessary to improve crystallinity and reduce crystallographic disorder. To this end, the synthesis of two new imidophosphorane ligands, [N═PtBu(pip)2]- (NPC1) and [N═PtBu(pyrr)2]- (NPC2) (pip = piperidinyl; pyrr = pyrrolidinyl), is presented, which break pseudo-C3 axes in the tetravalent complexes, U[NPC1]4 and U[NPC2]4. The reaction of these complexes with two-electron oxygen-atom-transfer reagents (N2O, trimethylamine N-oxide (TMAO) and 2,3:5,6-dibenzo-7-azabicyclo[2.2.1]hepta-2,5-diene (dbabhNO)) yields the U6+ mono-oxo complexes U(O)[NPC1]4 and U(O)[NPC2]4. This methodology is optimized for direct translation to transuranic elements. Of the two ligands, the NPC2 framework is most suitable for facilitating detailed bonding analysis and assessment of the ITI. Theoretical evaluation of the U-(NPC) bonding confirms a substantial difference between axially and equatorially bonded N atoms, revealing markedly more covalent U-Nax interactions. The U 6d + 5f combined contribution for U-Nax is nearly double that of U-Neq, accounting for ITI shortening and increased bond order of the axial bond. Two distinct N-atom hybridizations in the pyrrolidine/piperidine rings are noted across the complexes, with approximate sp2 and sp3 configurations describing the slightly shorter P-N"planar" and slightly longer P-N"pyramidal" bonds, respectively. In all complexes, the NPC2 ligands feature more planar N atoms than NPC1, in accordance with a higher electron-donating capacity of the former.
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Affiliation(s)
- Julie E Niklas
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States
| | - Chad M Studvick
- Department of Chemistry, The University of Akron, Akron, Ohio 44325-3601, United States
| | - John Bacsa
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States
| | - Ivan A Popov
- Department of Chemistry, The University of Akron, Akron, Ohio 44325-3601, United States
| | - Henry S La Pierre
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States.,Nuclear and Radiological Engineering Program, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, United States
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Abstract
Bond dissociation energy (BDE) has been calculated for a series of compounds that contain N-O bonds. These structures encompass model N,N,O-trisubstituted hydroxylamines that include O-methoxy, O-acyl, and O-phenyl hydroxylamines. The calculations used three accurate composite methods, CBS-QB3, CBS-APNO, and G4 methods and the computationally more affordable M06-2X/6-311+G(3df,2p) density functional theory (DFT) functional. The calculated N-O single-bond BDEs are 5-15 kcal/mol higher than a generic N-O BDE of 48 kcal/mol quoted in the literature and in textbooks. The M06-2X DFT functional provides BDEs that are in excellent agreement with the higher-level composite methods. We also provided a comparison of the N-O BDE for pyridine-N-oxide to simple trialkylamine oxides. Based on an experimental BDE of 63.3 ± 0.5 kcal/mol for pyridine-N-oxide, our best estimate gives 56.7 ± 0.9 kcal/mol N-O BDE for trimethylamine-N-oxide and 59.0 ± 0.8 kcal/mol for triethylamine-N-oxide.
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Affiliation(s)
- Robert D Bach
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
| | - H Bernhard Schlegel
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202-3489, United States
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Fournier R, Green AR, Greenberg A, Lee-Ruff E, Liebman JF, Rágyanszki A. Predicted Reversal in N-Methylazepine/N-Methyl-7-azanorcaradiene Equilibrium Upon Formation of Their N-Oxides. Molecules 2020; 25:E4767. [PMID: 33081412 PMCID: PMC7594072 DOI: 10.3390/molecules25204767] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Revised: 10/08/2020] [Accepted: 10/12/2020] [Indexed: 11/16/2022] Open
Abstract
Density functional calculations and up to five different basis sets have been applied to the exploration of the structural, enthalpy and free energy changes upon conversion of the azepine to the corresponding N-oxide. Although it is well known that azepines are typically much more stable than their 7-azanorcaradiene valence isomers, the stabilities are reversed for the corresponding N-oxides. Structural, thermochemical as well as nucleus-independent chemical shift (NICS) criteria are employed to probe the potential aromaticity, antiaromaticity and nonaromaticity of N-methylazepine, its 7-azanorcaradiene valence isomer. For the sake of comparison, analogous studies are performed on N-methylpyrrole and its N-oxide.
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Affiliation(s)
- René Fournier
- Department of Chemistry, York University, Keele Campus, Toronto, ON MJ3 1P3, Canada;
| | - Alexa R. Green
- Department of Chemistry, University of New Hampshire, Durham, NH 03824, USA;
| | - Arthur Greenberg
- Department of Chemistry, University of New Hampshire, Durham, NH 03824, USA;
| | - Edward Lee-Ruff
- Department of Chemistry, York University, Keele Campus, Toronto, ON MJ3 1P3, Canada;
| | - Joel F. Liebman
- Department of Chemistry and Biochemistry, University of Maryland Baltimore County, Baltimore, MD 21250, USA
| | - Anita Rágyanszki
- Department of Physics and Astronomy, York University, Keele Campus, Toronto, ON MJ3 1P3, Canada
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