1
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Baachaoui S, Hajlaoui R, Aoun SB, Fortunelli A, Sementa L, Raouafi N. Covalent surface modification of single-layer graphene-like BC 6N nanosheets with reactive nitrenes for selective ammonia sensing via DFT modeling. NANOTECHNOLOGY 2024; 35:425501. [PMID: 39025079 DOI: 10.1088/1361-6528/ad64da] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2024] [Accepted: 07/18/2024] [Indexed: 07/20/2024]
Abstract
Novel graphene-like nanomaterials with a non-zero bandgap are important for the design of gas sensors. The selectivity toward specific targets can be tuned by introducing appropriate functional groups on their surfaces. In this study, we use first-principles simulations, in the form of density functional theory (DFT), to investigate the covalent functionalization of a single-layer graphitized BC6N with azides to yield aziridine-functionalized adducts and explore their possible use to realize ammonia sensors. First, we determine the most favorable sites for physical adsorption and chemical reaction of methylnitrene, arising from the decomposition of methylazide, onto a BC6N monolayer. Then, we examine the thermodynamics of the [1 + 2]-cycloaddition reaction of various phenylnitrenes and perfluorinated phenylnitrenes para-substituted with (R = CO2H, SO3H) groups, demonstrating favorable energetics. We also monitor the effect of the functionalization on the electronic properties of the nanosheets via density of states and band structure analyses. Finally, we test four dBC6N to gBC6N substrates in the sensing of ammonia. We show that, thanks to their hydrogen bonding capabilities, the functionalized BC6N can selectively detect ammonia, with interaction energies varying from -0.54 eV to -1.37 eV, even in presence of competing gas such as CO2and H2O, as also confirmed by analyzing the change in the electronic properties and the values of recovery times near ambient temperature. Importantly, we model the conductance of a selected substrate alone and in presence of NH3to determine its effect on the integrated current, showing that humidity and coverage conditions should be properly tuned to use HO2C-functionalized BC6N-based nanomaterials to develop selective gas sensors for ammonia.
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Affiliation(s)
- Sabrine Baachaoui
- Sensors and Biosensors Group, Laboratory of Analytical Chemistry and Electrochemistry (LR99ES15), Chemistry Department, Faculty of Science of Tunis, University of Tunis El Manar, Tunis El Manar 2092, Tunisia
| | - Rabiaa Hajlaoui
- Advanced Materials and Quantum Phenomena Laboratory, Physics Department, Faculty of Science of Tunis, University of Tunis El Manar, Tunis El Manar 2092, Tunisia
| | - Sami Ben Aoun
- Department of Chemistry, Faculty of Science, Taibah University, PO Box 30002, Al-Madinah Al-Munawwarah, Saudi Arabia
| | | | - Luca Sementa
- Consiglio Nazionale delle Ricerche, CNR-ICCOM & IPCF, 56124 Pisa, Italy
| | - Noureddine Raouafi
- Sensors and Biosensors Group, Laboratory of Analytical Chemistry and Electrochemistry (LR99ES15), Chemistry Department, Faculty of Science of Tunis, University of Tunis El Manar, Tunis El Manar 2092, Tunisia
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2
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Janssen M, Frederichs T, Olaru M, Lork E, Hupf E, Beckmann J. Synthesis of a stable crystalline nitrene. Science 2024; 385:318-321. [PMID: 38870274 DOI: 10.1126/science.adp4963] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2024] [Accepted: 06/03/2024] [Indexed: 06/15/2024]
Abstract
Nitrenes are a highly reactive, yet fundamental, compound class. They possess a monovalent nitrogen atom and usually a short life span, typically in the nanosecond range. Here, we report on the synthesis of a stable nitrene by photolysis of the arylazide MSFluindN3 (1), which gave rise to the quantitative formation of the arylnitrene MSFluindN (2) (MSFluind is dispiro[fluorene-9,3'-(1',1',7',7'-tetramethyl-s-hydrindacen-4'-yl)-5',9''-fluorene]) that remains unchanged for at least 3 days when stored under argon atmosphere at room temperature. The extraordinary life span permitted the full characterization of 2 by single-crystal x-ray crystallography, electron paramagnetic resonance spectroscopy, and superconducting quantum interference device magnetometry, which supported a triplet ground state. Theoretical simulations suggest that in addition to the kinetic stabilization conferred by the bulky MSFluind aryl substituent, electron delocalization across the central aromatic ring contributes to the electron stabilization of 2.
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Affiliation(s)
- Marvin Janssen
- Institute of Inorganic Chemistry and Crystallography, Faculty of Biology and Chemistry, University of Bremen, Leobener Str. 7, D-28359 Bremen, Germany
| | - Thomas Frederichs
- Faculty of Geosciences, University of Bremen, Klagenfurther Str. 2-4, D-28359 Bremen, Germany
| | - Marian Olaru
- Institute of Inorganic Chemistry and Crystallography, Faculty of Biology and Chemistry, University of Bremen, Leobener Str. 7, D-28359 Bremen, Germany
| | - Enno Lork
- Institute of Inorganic Chemistry and Crystallography, Faculty of Biology and Chemistry, University of Bremen, Leobener Str. 7, D-28359 Bremen, Germany
| | - Emanuel Hupf
- Institute of Inorganic Chemistry and Crystallography, Faculty of Biology and Chemistry, University of Bremen, Leobener Str. 7, D-28359 Bremen, Germany
| | - Jens Beckmann
- Institute of Inorganic Chemistry and Crystallography, Faculty of Biology and Chemistry, University of Bremen, Leobener Str. 7, D-28359 Bremen, Germany
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3
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de Kler N, Pereverzev AY, Roithová J. Terminal Copper Nitrenoid Formation and Reactivity Induced by Absorption to an Antenna Ligand. Angew Chem Int Ed Engl 2024; 63:e202319270. [PMID: 38314650 DOI: 10.1002/anie.202319270] [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: 12/13/2023] [Revised: 01/22/2024] [Accepted: 02/05/2024] [Indexed: 02/06/2024]
Abstract
Copper nitrenoids are key intermediates in copper-catalyzed direct C-H amination reactions. Further development of this important reaction relies on knowing the properties and reactivity of the nitrenoid intermediates. This work utilizes antenna ligands to form copper nitrenoid complexes and monitor the consecutive C-H amination reactions under well-defined single-molecule conditions in the gas phase. The [Cu(Lphoto)(Lazide)]+ precursors (Lphoto is a bidentate antenna ligand, and Lazide is an organic azide) were stored in an ion trap at 3.5 K and irradiated by visible light, which resulted in denitrogenation of the complex. Further irradiation of the copper nitrenoid led to the consecutive C-H amination of the antenna ligand. The nitrenoid complexes, as well as the products of the C-H amination, were characterized by helium tagging IRPD spectroscopy, and the mechanism was described by DFT calculations. This research demonstrates that the antenna ligands can be used to promote the denitrogenation of metal azides in the gas phase and also channel the internal energy to promote further reactivity, which opens a new way to study the reactivity of highly reactive species under well-defined conditions.
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Affiliation(s)
- Noël de Kler
- Department of Spectroscopy and Catalysis, Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands
| | - Aleksandr Y Pereverzev
- Department of Spectroscopy and Catalysis, Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands
| | - Jana Roithová
- Department of Spectroscopy and Catalysis, Institute for Molecules and Materials, Radboud University, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands
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4
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Algarra M, Soto J, Pino-González MS, Gonzalez-Munoz E, Dučić T. Multifunctionalized Carbon Dots as an Active Nanocarrier for Drug Delivery to the Glioblastoma Cell Line. ACS OMEGA 2024; 9:13818-13830. [PMID: 38559983 PMCID: PMC10976390 DOI: 10.1021/acsomega.3c08459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/26/2023] [Revised: 02/02/2024] [Accepted: 02/08/2024] [Indexed: 04/04/2024]
Abstract
Nanoparticle-based nanocarriers represent a viable alternative to conventional direct administration in cancer cells. This advanced approach employs the use of nanotechnology to transport therapeutic agents directly to cancer cells, thereby reducing the risk of damage to healthy cells and enhancing the efficacy of treatment. By approving nanoparticle-based nanocarriers, the potential for targeted, effective treatment is greatly increased. The so-called carbon-based nanoparticles, or carbon dots, have been hydrothermally prepared and initiated by a polymerization process. We synthesized and characterized nanoparticles of 2-acrylamido-2-methylpropanesulfonic acid, which showed biocompatibility with glioblastoma cells, and further, we tested them as a carrier for the drug riluzole. The obtained nanoparticles have been extensively characterized by techniques to obtain the exact composition of their surface by using Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), and nuclear magnetic resonance (NMR) spectroscopy, as well as cryo-transmission electron microscopy. We found that the surface of the synthesized nanoparticles (NPs) is covered mainly by sulfonated, carboxylic, and substituted amide groups. These functional groups make them suitable as carriers for drug delivery in cancer cells. Specifically, we have successfully utilized the NPs as a delivery system for the drug riluzole, which has shown efficacy in treating glioblastoma cancer cells. The effect of nanoparticles as carriers for the riluzole system on glioblastoma cells was studied using live-cell synchrotron-based FTIR microspectroscopy to monitor in situ biochemical changes. After applying nanoparticles as nanocarriers, we have observed changes in all biomacromolecules, including the nucleic acids and protein conformation. These findings provide a strong foundation for further exploration into the development of targeted treatments for glioblastoma.
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Affiliation(s)
- Manuel Algarra
- INAMAT—Institute for Advanced Materials and Mathematics,
Dept. Science, Public University of Navarra, Campus Arrosadía, 31006 Pamplona, Spain
| | - Juan Soto
- Dept.
Physical Chemistry, Faculty of Science, University of Málaga, Avda. Cervantes, 2, 29071 Málaga, Spain
| | | | - Elena Gonzalez-Munoz
- Instituto
de Investigación Biomédica de Málaga y Plataforma
en Nanomedicina-IBIMA Plataforma BIONAND., C/Severo Ochoa, 35, 29590 Málaga, Spain
- Dept.
Cell Biology, Genetics and Physiology, University
of Málaga, 29071 Málaga, Spain
| | - Tanja Dučić
- ALBA-CELLS
Synchrotron Light Source, Consorcio para
la Construccion Equipamiento y Explotacion del Laboratorio de Luz
Sincrotron, C. de la Llum 2-26, 08290 Cerdanyola del Vallès, Barcelona, Spain
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5
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Soto J. Identification of the Photoreactive Species of Protonated N-Nitrosopiperidine in Acid Medium: A CASPT2 and DFT Study. J Phys Chem A 2023; 127:9781-9786. [PMID: 37948763 PMCID: PMC10683013 DOI: 10.1021/acs.jpca.3c06477] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Revised: 10/25/2023] [Accepted: 10/27/2023] [Indexed: 11/12/2023]
Abstract
In this work, we have studied the initial reaction step after photoexcitation of protonated N-nitrosopiperidine both in the gas and condensed phases. To achieve this end, we have applied the CASPT2 and MP2 wave function methods and the density functional theory approach. It is found that the site of protonation of N-nitrosopiperidine in acid medium depends on the solvent: protonation occurs at the oxygen atom in protic solvents, while in aprotic solvents, the proton is bonded at the N-atom of the amine moiety. Furthermore, protonation at such an N-atom is the unique protonated species that absorbs in the visible range and directly dissociates into aminium radical cation and nitric oxide.
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Affiliation(s)
- Juan Soto
- Department of Physical Chemistry, Faculty of Science, University of Málaga, Malaga 29071, Spain
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6
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Belostotskii AM. Delocalization quantitatively mapped for prototypic organic nitroanions as well as azidoform anions. RSC Adv 2023; 13:33786-33796. [PMID: 38019983 PMCID: PMC10655850 DOI: 10.1039/d3ra06708d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Accepted: 11/09/2023] [Indexed: 12/01/2023] Open
Abstract
Delocalization of occupied orbitals impacts the chemical bonding in the simplest known pernitroanions [(NO2)3C]- (1) and [(NO2)2N]- (2) as well as other functionalized organic anions. By quantitatively mapping it onto molecular backbones of 1, 2, [CH2NO2]- (3), [CH3NNO2]- (4) and [C(N3)]- (6) anions (all modeled by QM calculations), the Weinhold's NBO analysis refines their chemical structure, enabling to explain and even predict their essential chemical behaviour. In detail, the HOMO of 1 and 2 is associated with the central atom to the degree of 70.7% and 80.4%, respectively, while the HOMO localization on O atoms for 3 and 4 is 85.3% and 81.1%, respectively. Predomination of C-alkylation for 1 and that of O-alkylation for 3 in non-coordinating solvents thus becomes clear. The important news is that the easiness of homolytically disrupting the N-N bond in 2, a constituent of inexpensive powerful explosives, is because of the occupancy of the related σ*orbital increases with stretching this bond. The same is true for electrocyclic extrusion of NO3- from this molecule. This antibonding effect may be assumed to be the common cause of the proneness of aliphatic nitro compounds to decompose. Pyramidal anion 6 is a highly localized carbanion. Its isomer of molecular symmetry CS has a unique chemical structure of its azido substituents: each of them is represented by one high-weight resonance structure, e.g., N-N[triple bond, length as m-dash]N. The prediction is that the dinitrogen-eliminating decomposition of this isomer is more facile than of the isomer of C3 symmetry. In summary, this study affords three novel particular insights into the chemical structure and reactivity of these anions: chemically telling delocalization-augmented molecular structures, a reasonable hypothesis of the common cause of thermally triggered instability of aliphatic nitro compounds, and discovered one-resonance structure azido groups.
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7
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Drabkin VD, Paczelt V, Eckhardt AK. Spectroscopic identification of interstellar relevant 2-iminoacetaldehyde. Chem Commun (Camb) 2023; 59:12715-12718. [PMID: 37814897 DOI: 10.1039/d3cc04192a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/11/2023]
Abstract
Imines play a fundamental role in organic synthesis and some of them have been detected in space. However, the simplest imines are spectroscopically not well-characterized. Herein we present the infrared and UV/Vis spectroscopic characterization of 2-iminoacetaldehyde using cryogenic matrix isolation techniques. After UV irradiation of 2-azidoacetaldehyde in solid argon at 3 K we identified two conformers of 2-iminoacetaldehyde, which can be photochemically interconverted. Deuterium labelling experiments and high level ab initio coupled cluster calculations at the CCSD(T)/CBS level of theory provide further evidence for the formation of 2-iminoacetaldehyde.
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Affiliation(s)
- Vladimir D Drabkin
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum, Bochum 44801, Germany.
| | - Viktor Paczelt
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum, Bochum 44801, Germany.
| | - André K Eckhardt
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum, Bochum 44801, Germany.
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8
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Domenianni LI, Bauer M, Schmidt-Räntsch T, Lindner J, Schneider S, Vöhringer P. Photoinduced Metallonitrene Formation by N 2 Elimination from Azide Diradical Ligands. Angew Chem Int Ed Engl 2023; 62:e202309618. [PMID: 37549374 DOI: 10.1002/anie.202309618] [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: 07/07/2023] [Revised: 08/04/2023] [Accepted: 08/07/2023] [Indexed: 08/09/2023]
Abstract
Transition-metal nitrides/nitrenes are highly promising reagents for catalytic nitrogen-atom-transfer reactivity. They are typically prepared in situ upon optically induced N2 elimination from azido precursors. A full exploitation of their catalytic potential, however, requires in-depth knowledge of the primary photo-induced processes and the structural/electronic factors mediating the N2 loss with birth of the terminal metal-nitrogen core. Using femtosecond infrared spectroscopy, we elucidate here the primary molecular-level mechanisms responsible for the formation of a unique platinum(II) nitrene with a triplet ground state from a closed-shell platinum(II) azide precursor. The spectroscopic data in combination with quantum-chemical calculations provide compelling evidence that product formation requires the initial occupation of a singlet excited state with an anionic azide diradical ligand that is bound to a low-spin d8 -configured PtII ion. Subsequent intersystem crossing generates the Pt-bound triplet azide diradical, which smoothly evolves into the triplet nitrene via N2 loss in a near barrierless adiabatic dissociation. Our data highlight the importance of the productive, N2 -releasing state possessing azide ππ* character as a design principle for accessing efficient N-atom-transfer catalysts.
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Affiliation(s)
- Luis I Domenianni
- Clausius-Institut für Physikalische und Theoretische Chemie, Rheinische Friedrich-Wilhelms-Universität, Wegelerstraße 12, 53115, Bonn, Germany
| | - Markus Bauer
- Clausius-Institut für Physikalische und Theoretische Chemie, Rheinische Friedrich-Wilhelms-Universität, Wegelerstraße 12, 53115, Bonn, Germany
| | - Till Schmidt-Räntsch
- Georg-August-Universität Göttingen, Institut für Anorganische Chemie, Tammannstraße 4, 37077, Göttingen, Germany
| | - Jörg Lindner
- Clausius-Institut für Physikalische und Theoretische Chemie, Rheinische Friedrich-Wilhelms-Universität, Wegelerstraße 12, 53115, Bonn, Germany
| | - Sven Schneider
- Georg-August-Universität Göttingen, Institut für Anorganische Chemie, Tammannstraße 4, 37077, Göttingen, Germany
| | - Peter Vöhringer
- Clausius-Institut für Physikalische und Theoretische Chemie, Rheinische Friedrich-Wilhelms-Universität, Wegelerstraße 12, 53115, Bonn, Germany
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9
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Cruz Neto DH, Soto J, Maity N, Lefumeux C, Nguyen T, Pernot P, Steenkeste K, Peláez D, Ha-Thi MH, Pino T. A Novel Pump-Pump-Probe Resonance Raman Approach Featuring Light-Induced Charge Accumulation on a Model Photosystem. J Phys Chem Lett 2023; 14:4789-4795. [PMID: 37186953 DOI: 10.1021/acs.jpclett.3c00594] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Light-induced charge accumulation is at the heart of biomimetic systems aiming at solar fuel production in the realm of artificial photosynthesis. Understanding the mechanisms upon which these processes operate is a necessary condition to drive down the rational catalyst design road. We have built a nanosecond pump-pump-probe resonance Raman setup to witness the sequential charge accumulation process while probing vibrational features of different charge-separated states. By employing a reversible model system featuring methyl viologen (MV) as a dual electron acceptor, we have been able to watch the photosensitized production of its neutral form, MV0, resulting from two sequential electron transfer reactions. We have found that, upon double excitation, a fingerprint vibrational mode corresponding to the doubly reduced species appears at 992 cm-1 and peaks at 30 μs after the second excitation. This has been further confirmed by simulated resonance Raman spectra which fully support our experimental findings in this unprecedented buildup of charge seen by a resonance Raman probe.
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Affiliation(s)
- Daniel H Cruz Neto
- Institut des Sciences Moléculaires d'Orsay (ISMO), Université Paris-Saclay, CNRS, 91405 Orsay, France
| | - Juan Soto
- Department of Physical Chemistry, Faculty of Science, University of Málaga, E-29071 Málaga, Spain
| | - Nishith Maity
- Institut des Sciences Moléculaires d'Orsay (ISMO), Université Paris-Saclay, CNRS, 91405 Orsay, France
| | - Christophe Lefumeux
- Institut des Sciences Moléculaires d'Orsay (ISMO), Université Paris-Saclay, CNRS, 91405 Orsay, France
| | - Thai Nguyen
- Institut des Sciences Moléculaires d'Orsay (ISMO), Université Paris-Saclay, CNRS, 91405 Orsay, France
| | - Pascal Pernot
- Institut de Chimie Physique (ICP), Université Paris-Saclay, CNRS, 91405 Orsay, France
| | - Karine Steenkeste
- Institut des Sciences Moléculaires d'Orsay (ISMO), Université Paris-Saclay, CNRS, 91405 Orsay, France
| | - Daniel Peláez
- Institut des Sciences Moléculaires d'Orsay (ISMO), Université Paris-Saclay, CNRS, 91405 Orsay, France
| | - Minh-Huong Ha-Thi
- Institut des Sciences Moléculaires d'Orsay (ISMO), Université Paris-Saclay, CNRS, 91405 Orsay, France
| | - Thomas Pino
- Institut des Sciences Moléculaires d'Orsay (ISMO), Université Paris-Saclay, CNRS, 91405 Orsay, France
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10
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Paczelt V, Wende RC, Schreiner PR, Eckhardt AK. Glycine Imine-The Elusive α-Imino Acid Intermediate in the Reductive Amination of Glyoxylic Acid. Angew Chem Int Ed Engl 2023; 62:e202218548. [PMID: 36656102 DOI: 10.1002/anie.202218548] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 01/18/2023] [Accepted: 01/18/2023] [Indexed: 01/20/2023]
Abstract
Simple unhindered aldimines tend to hydrolyze or oligomerize and are therefore spectroscopically not well characterized. Herein we report the formation and spectroscopic characterization of the simplest imino acid, namely glycine imine, by cryogenic matrix isolation IR and UV/Vis spectroscopy. Glycine imine forms after UV irradiation of 2-azidoacetic acid by N2 extrusion in anti-(E,E)- and anti-(Z,Z)-conformation that can be photochemically interconverted. In matrix isolation pyrolysis experiments with 2-azidoacetic acid, glycine imine cannot be trapped as it further decarboxylates to aminomethylene. In aqueous solution glycine imine is hydrolyzed to hydroxy glycine and hydrated glyoxylic acid. At higher concentrations or in the presence of FeII SO4 as a reducing agent glycine imine undergoes self-reduction by oxidative decarboxylation chemistry. Glycine imine may be seen as one of the key reaction intermediates connecting prebiotic amino acid and sugar formation chemistry.
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Affiliation(s)
- Viktor Paczelt
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum, Universitätsstraße 150, 44801, Bochum, Germany
| | - Raffael C Wende
- Institute of Organic Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35392, Giessen, Germany
| | - Peter R Schreiner
- Institute of Organic Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35392, Giessen, Germany
| | - André K Eckhardt
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum, Universitätsstraße 150, 44801, Bochum, Germany
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11
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Soto J. Photochemistry of 1-Phenyl-1-diazopropane and Its Diazirine Isomer: A CASSCF and MS-CASPT2 Study. J Phys Chem A 2022; 126:8372-8379. [PMID: 36335481 PMCID: PMC9677432 DOI: 10.1021/acs.jpca.2c04816] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Revised: 10/10/2022] [Indexed: 11/07/2022]
Abstract
In this work, we studied the wavelength (520 or 350 nm) dependence of the photochemical decomposition of 1-phenyl-1-diazopropane (PDP) and 1-phenyl-1-propyl diazirine (PED) by means of high-level ab initio quantum chemical calculations (CASSCF and MS-CASPT2) to obtain qualitative and quantitative results. It is found that the photochemistry of PDP is governed by nonradiative deactivation processes that can involve one or two S1/S0 conical intersections (CI1 and CI2) depending on the wavelength of the radiation; CI2 is only accessible at the shortest wavelength. It is demonstrated that the main intermediate of the photochemistry of the titled compounds is 1-ethyl-1-phenyl carbene (EPC). Upon irradiation of PDP with the 520 nm light, the carbene is always generated in its ground state as closed-shell singlet carbene. In contrast, the 350 nm radiation can directly decompose PDP into S1 carbene (open shell) and N2 when the conical intersection CI2 is avoided. Once the carbene is formed in the S1 state, it can experience excited state intramolecular proton transfer along a seam of crossing (ESIPT-SC) of the S1 and S0 states to yield the alkene derivative; that is, the proton transfer reaction takes places on a degenerate potential energy surface where the two electronic states have equal energy. In addition, it is found that EPC absorbs at 350 nm (double excitations); therefore, there is another possible route that can induce as well a slightly different photochemistry in changing the wavelength of the radiation because the shortest wavelength (when it is intense enough) decreases the amount of available EPC or generates a highly vibrationally excited state of the carbene; that is, after 350 nm excitation, the carbene intermediate can deactivate via radiation emission or can decay through a cascade of conical intersections to its first excited state (S1), where ESIPT-SC is operative again.
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Affiliation(s)
- Juan Soto
- Department of Physical Chemistry,
Faculty of Science, University of Málaga, 29071 Málaga, Spain
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12
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Eckhardt AK. Spectroscopic evidence for 1,2-diiminoethane - a key intermediate in imidazole synthesis. Chem Commun (Camb) 2022; 58:8484-8487. [PMID: 35815822 DOI: 10.1039/d2cc03065a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Simple imines and diimines are common building blocks in organic synthesis, but the compound class is spectroscopically not well characterized. Herein we report the formation of the simplest diimine, namely 1,2-diiminoethane, as well as spectroscopic characterization by cryogenic matrix isolation IR and UV/Vis spectroscopy. Three conformers of 1,2-diiminoethane form after UV irradiation of 1,2-diazidoethane by N2 extrusion at 3 K in solid argon and can be photochemically interconverted. In a matrix isolation pyrolysis experiment at 600 °C with 1,2-diazidoethane as the starting material we observe hydrogen cyanide and formaldimine as the main decomposition products. All experimental findings are supported by deuterium labeling experiments and B3LYP/6-311++G(2d,2p) calculations. Irradiation of 1,2-diazidoethane in aqueous solution leads to the formation of imidazoles as indicated by NMR spectroscopy and GC-MS analysis. Our results underline the key role of diimines as building blocks in N-heterocyclic chemistry.
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Affiliation(s)
- André K Eckhardt
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum, 44801, Bochum, Germany.
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