Among all C-, N-, and O-centered polyradicals, high-spin nitrenes possess the largest magnetic anisotropy and are of considerable interest as multi-level molecular spin systems for exploration of organic molecular magnetism and quantum information processing. Although the first representatives of quintet and septet nitrenes were obtained almost 50 years ago, the experimental and theoretical studies of these highly reactive species became possible only recently, owing to new achievements in molecular spectroscopy and computational chemistry. Meanwhile, dozens of various quintet dinitrenes and septet trinitrenes were successfully characterized by IR, UV/Vis, and EPR spectroscopy, thus providing important information about the electronic structure, magnetic properties and reactivity of these compounds.
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http://dx.doi.org/10.1002/chem.202002234 | DOI Listing |
J Phys Chem A
December 2024
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Ave. 47, Moscow 119991, Russian Federation.
In this study, low-temperature EPR spectroscopy and quantum-chemical techniques were employed to investigate multispin systems─1,5-diphenyl-3-(3-nitrenophenyl)-6-oxoverdazyl and 1,5-diphenyl-3-(4-nitrenophenyl)-6-oxoverdazyl─that contain a nitrene center at either a - or -position, respectively. Ground states and magnetic zero-field splitting (ZFS) parameters of these multispin systems were determined by experimental and computational methods. The results indicated that the high-spin quartet state is a ground state, and the quartet-doublet energy gap is close to 10 kcal/mol for the -position of the nitrene group, with ZFS parameters = 0.
View Article and Find Full Text PDFJ Am Chem Soc
July 2024
Key Laboratory of Green Chemistry & Technology, Ministry of Education, College of Chemistry, Sichuan University, Chengdu 610064, China.
Transition-metal-catalyzed enantioselective nitrene transfer to sulfides has emerged as one of the most powerful strategies for rapid construction of enantioenriched sulfimides. However, achieving stereocontrol over highly active earth-abundant transition-metal nitrenoid intermediates remains a formidable challenge compared with precious metals. Herein, we disclose a chiral iron(II)/,'-dioxide-catalyzed enantioselective imidation of dialkyl and alkyl aryl sulfides using iminoiodinanes as nitrene precursors.
View Article and Find Full Text PDFChemistry
July 2024
Fakultät für Chemie und Biochemie, Organische Chemie II, Ruhr Universität Bochum, Universitätsstraße 150, Bochum, 44801, Germany.
Vibrational circular dichroism (VCD) spectra of chiral high-spin organic radicals are expected to show a strong intensity enhancement and are thought to be difficult to predict using state-of-the-art theoretical methods. Herein we show that the chiral triplet nitrene obtained from photochemical cleavage of N from enantiopure 2-azido-9H-fluorenol does not feature extraordinarily strong intensities and that the experimental spectra match nicely with calculated ones. Thereby, this study demonstrates the general feasibility of studies on chiral high-spin organics by matrix-isolation VCD.
View Article and Find Full Text PDFJACS Au
December 2023
School of Chemical Sciences, Indian Institute of Technology Mandi, Mandi, Himachal Pradesh 175075, India.
Detailed electronic structure and its correlation with the intramolecular C-H amination reactivity of Fe-porphyrin-nitrene intermediates bearing different "axial" coordination have been investigated using multiconfigurational complete active space self-consistent field (CASSCF), N-electron valence perturbation theory (NEVPT2), and hybrid density functional theory (DFT-B3LYP) calculations. Three types of "axial" coordination, -OMe/-O(H)Me (/), -SMe/-S(H)Me (), and -NMeIm (MeIm = 3-methyl-imidazole) () mimicking serine, cysteine, and histidine, respectively, along with no axial coordination () have been considered to decipher how the "axial" coordination of different strengths regulates the electronic integrity of the Fe-N core and nitrene-transfer reactivity of Fe-porphyrin-nitrene intermediates. CASSCF-based natural orbitals reveal two distinct classes of electronic structures: Fe-nitrenes ( and ) with relatively stronger axial coordination (-OMe and -SMe) display "imidyl" nature and those ( and ) with weaker axial coordination (-O(H)Me, -S(H)Me and no axial coordination) exhibit "imido-like" character.
View Article and Find Full Text PDFJ Am Chem Soc
December 2023
Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea.
We report the synthesis and characterization of a mononuclear nonheme cobalt(III)-imidyl complex, [Co(NTs)(TQA)(OTf)] (), with an = 3/2 spin state that is capable of facilitating exogenous substrate modifications. Complex was generated from the reaction of Co(TQA)(OTf) with PhINTs at -20 °C. A flow setup with ESI-MS detection was used to explore the kinetics of the formation, stability, and degradation pathway of in solution by treating the Co(II) precursor with PhINTs.
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