Triplet Alkyl Nitrenes

Muthukrishnan, Sivaramakrishnan; Ranaweera, R. A. A. Upul; Guđmundsdóttir, Anna D.

doi:10.1002/9781118560907.ch5

Cited by 12 publications

(12 citation statements)

References 92 publications

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“…[5][6][7] In comparison, triplet alkylnitrenes and arylnitrenes are less reactive and longer-lived, as they do not react with the solvent, but mainly decay by dimerization (Scheme 1). [8][9][10][11][12][13] Because triplet alkylnitrenes and arylnitrenes have high spin properties and are long-lived, they have a potential as building blocks for high spin assemblies. In contrast, triplet vinylnitrene intermediates are short-lived in solution, in spite of their electron-donating substituents, because they decay by intersystem crossing to form azirines and isoxazoles.…”

Section: Introductionmentioning

confidence: 99%

“…For example, triplet carboalkoxynitrenes are short‐lived, as they abstract H atoms from the solvent . In comparison, triplet alkylnitrenes and arylnitrenes are less reactive and longer‐lived, as they do not react with the solvent, but mainly decay by dimerization (Scheme ) . Because triplet alkylnitrenes and arylnitrenes have high spin properties and are long‐lived, they have a potential as building blocks for high spin assemblies.…”

Section: Introductionmentioning

confidence: 99%

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Photolysis of 3,5‐diphenylisoxazole in argon matrices

Sriyarathne

Sarkar

Hatano

et al. 2016

J of Physical Organic Chem

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Broadband irradiation of 3,5‐diphenylisoxazole 1 in an argon matrix results in formation of azirine 3. Further irradiation of the matrix reduces the amount of azirine 3 with concurrent formation of ylide 4. Thus, it is theorized that the conversion of isoxazole 1 to azirine 3 goes through a triplet vinylnitrene 2 that does not intersystem cross to ketenimine 6. Hence, the reactivity of triplet vinylnitrene 2 is different from similar vinylnitrene intermediates with α‐methyl substituents that intersystem cross to form corresponding ketenimines. Density functional theory calculations support the notion that the conjugation of the α‐phenyl group to the vinylnitrene moiety in vinylnitrene 2 renders it more flexible than vinylnitrenes with α‐methyl substituents, and therefore, vinylnitrene 2 intersystem crosses to azirine 3, rather than ketenimine 6. Copyright © 2016 John Wiley & Sons, Ltd.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Photolysis of 3,5‐diphenylisoxazole in argon matrices

Sriyarathne

Sarkar

Hatano

et al. 2016

J of Physical Organic Chem

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“…The N–N–N bond angle in T A of 1 was approximately 119.5° and the spin density calculations showed that the unpaired electrons in T A of 1 are localized on the α‐ and γ‐N atoms (Fig. 5), as typically observed for triplet alkyl azides (1,22,23).…”

Section: Resultsmentioning

confidence: 70%

“…The thermal activation or direct irradiation of alkyl azides in solution or cryogenic matrices generally results in the formation of corresponding imine products with the loss of a nitrogen molecule (1)(2)(3)(4). It has been theorized that the imine products are formed either from singlet alkylnitrene intermediates or in a concerted manner from the singlet excited state of the alkyl azides (Scheme 1) (5)(6)(7)(8)(9).…”

Section: Introductionmentioning

confidence: 99%

Photolysis of 3‐Azido‐3‐phenyl‐3H‐isobenzofuran‐1‐one at Ambient and Cryogenic Temperatures^†

Thenna‐Hewa

Sebastien

Lemen

et al. 2021

Photochem & Photobiology

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Although alkyl azides are known to typically form imines under direct irradiation, the product formation mechanism remains ambiguous as some alkyl azides also yield the corresponding triplet alkylnitrenes at cryogenic temperatures. The photoreactivity of 3-azido-3-phenyl-3H-isobenzofuran-1-one (1) was investigated in solution and in cryogenic matrices. Irradiation (k = 254 nm) of azide 1 in acetonitrile yielded a mixture of imines 2 and 3. Monitoring of the reaction progress using UV-Vis absorption spectroscopy revealed an isosbestic point at 210 nm, indicating that the reaction proceeded cleanly. Similar results were observed for the photoreactivity of azide 1 in a frozen 2-methyltetrahydrofuran (mTHF) matrix. Irradiation of azide 1 in an argon matrix at 6 K resulted in the disappearance of its IR bands with the concurrent appearance of IR bands corresponding to imines 2 and 3. Thus, it was theorized that azide 1 forms imines 2 and 3 via a concerted mechanism from its singlet excited state or through singlet alkylnitrene 1 1N, which does not intersystem cross to its triplet configuration. This proposal was supported by CASPT2 calculations on a model system, which suggested that the energy gap between the singlet and triplet configurations of alkylnitrene 1N is 33 kcal/mol, thus making intersystem crossing inefficient.

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“…) . Nitroso oxide may arise from the spin‐allowed reaction of triplet nitrene with 3 O 2 and is a reaction analogous to that of triplet carbenes with 3 O 2 . Owing to its ability to hydroxylate toluene, nitroso oxide has been described as possessing diradical character (RN•OO•) .…”

Section: Resultsmentioning

confidence: 99%

Density Functional Theory and ab Initio Computational Evidence for Nitrosamine Photoperoxides: Hammett Substituent Effects in the Photogeneration of the Nitrooxide Intermediate

Greer

Kwon

2018

Photochem & Photobiology

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Little attention has been focused on diradical and zwitterionic photoperoxides formed from nitrosamine compounds. Here, an attempt is made to probe the electronic character of the nitrooxide intermediate formed in photochemical reactions with triplet oxygen ( O ). Theoretical studies have been conducted to screen para-substituted phenyl nitrosamines. In particular, we find that electron-withdrawing substituents produce low-lying triplet nitrooxide diradicals. A clear electronic dependence in the S - T and S - S energy gaps of nitrooxides was found using Hammett plots. Computed geometries show a twisted diradical triplet nitrooxide moiety, which contrasts to the nearly flat singlet zwitterionic ground state nitrooxide moiety; analyses of charges (natural bond order), molecular orbitals (HOMO/LUMO) and spin densities enable these assignments. Calculations predict the former triplet species is photogenerated initially from nitrosamine with O . The conversion of the triplet nitrooxide diradical to the singlet ground state is an example where longer-lived zwitterionic nitrooxide structures become possible. The reaction mechanism is consistent with a zwitterionic ground state nitrooxide playing an important role in the bimolecular oxygen-transfer reaction with phosphine and phosphite trapping agents as has been observed experimentally.

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Triplet Alkyl Nitrenes

Cited by 12 publications

References 92 publications

Photolysis of 3,5‐diphenylisoxazole in argon matrices

Photolysis of 3,5‐diphenylisoxazole in argon matrices

Photolysis of 3‐Azido‐3‐phenyl‐3H‐isobenzofuran‐1‐one at Ambient and Cryogenic Temperatures^†

Density Functional Theory and ab Initio Computational Evidence for Nitrosamine Photoperoxides: Hammett Substituent Effects in the Photogeneration of the Nitrooxide Intermediate

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Triplet Alkyl Nitrenes

Cited by 12 publications

References 92 publications

Photolysis of 3,5‐diphenylisoxazole in argon matrices

Photolysis of 3,5‐diphenylisoxazole in argon matrices

Photolysis of 3‐Azido‐3‐phenyl‐3H‐isobenzofuran‐1‐one at Ambient and Cryogenic Temperatures†

Density Functional Theory and ab Initio Computational Evidence for Nitrosamine Photoperoxides: Hammett Substituent Effects in the Photogeneration of the Nitrooxide Intermediate

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Photolysis of 3‐Azido‐3‐phenyl‐3H‐isobenzofuran‐1‐one at Ambient and Cryogenic Temperatures^†