The chemistry of localized singlet 1,3-diradicals (biradicals): from putative intermediates to persistent species and unusual molecules with a π-single bonded character

Abe, Manabu; Ye, Jianhuai; Mishima, Megumi

doi:10.1039/c2cs00005a

Cited by 156 publications

(101 citation statements)

References 90 publications

(100 reference statements)

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“…Their isolable derivatives and analogues with enhanced stability and diradical character have also been explored. [1,4] Very recently Kamada et al and our group reported stable nitrogen analogues of Chichibabins hydrocarbon as diradicaloids (A-C in Scheme 2). [5] Herein we present the isolation and characterization of nitrogen analogues of Thieles hydrocarbon (1 2+ -3 2+ in Scheme 3).…”

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confidence: 97%

“…), and promising applications as functional materials in molecular electronics. [1] Thieles and Chichibabins hydrocarbons (Scheme 1), [2] which were prepared shortly after Gombergs synthesis of the triphenylmethyl radical, [3] have been the subjects of interest for more than one century. Both possess a characteristic resonance structure between an open-shell diradical and a closed-shell quinonoid form.…”

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confidence: 99%

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Nitrogen Analogues of Thiele’s Hydrocarbon

Wang

et al. 2014

Angew Chem Int Ed

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A series of bis[N,N-di-(4-methoxylphenyl)amino]arene dications 1(2+) -3(2+) have been synthesized and characterized. Their electronic structures were investigated by various experiments assisted by theoretical calculations. It was found that they are singlets in the ground state and that their diradical character is dependent on the bridging moiety. 3(2+) has a smaller singlet-triplet energy gap and its excited triplet state is thermally readily accessible. The work provides a nitrogen analogue of Thiele's hydrocarbon with considerable diradical character.

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confidence: 97%

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confidence: 99%

Nitrogen Analogues of Thiele’s Hydrocarbon

Wang

et al. 2014

Angew Chem Int Ed

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“…Only one diastereoisomer, the lk or S*S* diasteroisomer of 35 was isolated. This latter diastereoselectivity is also influenced by the radical combination in the diradical intermediate 37 which is related to particular properties of such intermediates [83,84]. In this step, an intersystem crossing form the triplet state of 37 to the singlet state of 35 is involved [85][86][87][88][89][90].…”

Section: Intramolecular Radical Addition With Electronically Excited mentioning

confidence: 99%

Photochemically induced radical reactions with furanones

Oelgemöller

Hoffmann

2015

Pure and Applied Chemistry

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Radicals are easily generated via hydrogen transfer form secondary alcohols or tertiary amines using photochemical sensitization with ketones. They can subsequently add to the electron deficient double bond of furanones. The addition of the alcohols is particularly efficient. Therefore, this reaction was used to characterize and to compare the efficiency of different photochemical continuous flow microreactors. A range of micro-structured reactors were tested and their performances evaluated. The enclosed microchip enabled high space-time-yields but its microscopic dimensions limited its productivity. In contrast, the open microcapillary model showed a greater potential for scale-up and reactor optimization. A 10-microcapillary reactor was therefore constructed and utilized for typical R&D applications. Compared to the corresponding batch processes, the microreactor systems gave faster conversions, improved product qualities and higher yields. Similar reactions have also been carried out with electronically excited furanones and other α,β-unsaturated ketones. In this case, hydrogen is transferred directly to the excited olefin. This reaction part may occur either in one step, i.e., electron and proton are transferred simultaneously, or it may occur in two steps, i.e., the electron is transferred first and the proton follows. In the first case, a C-C bond is formed in the α position of the α,β-unsaturated carbonyl compound and in the second case this bond is formed in the β position. For the first reaction, the influence of stereochemical elements of the substrate on the regioselectivity of the hydrogen abstraction on the side chain has been studied.

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“…Since biradicals are putative intermediates in the processes of bond formation and bond breaking, their characterization and isolation are of great interest. [2][3][4] In cycloadditions, biradicals were identified as obligatory intermediates. 5 Implicitly, biradicals are highly reactive species, which allows a rich follow-up chemistry.…”

Section: Introductionmentioning

confidence: 99%

Tunable Cyclopentane-1,3-diyls Generated by Insertion of Isonitriles into Diphosphadiazanediyls

2015

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Diphosphadiazanediyl ([P(μ-NTer)]2, 1) is known to readily react with small molecules bearing multiple bonds to give [2.1.1]bicyclic species. On the contrary, in the reaction of isonitriles with 1, planar five-membered heterocycles (3) with biradical character are formed by insertion of the carbon atom into one P-N bond. Under irradiation, heterocyclic biradicaloids 3 are shown to generate housane-type [2.1.0]bicyclopentanes by transannular bond formation. However, these housane species thermally equilibrate, reforming the open-shell singlet cyclopentanediyl. The biradical character of 3 indicates high reactivity which is further demonstrated in the activation of small molecules bearing multiple bonds leading to [2.2.1]bicyclic heterocycles. Depending on the substituent of the isonitrile, the reaction with a second equivalent of isonitrile is also observed for smaller substituents. By employing suitable diisonitriles, even the catenation of two open-shell singlet cyclopentane-1,3-diyls is achieved. CASSCF(6,6) computations revealed biradical character for 3 ranging between 26 and 27%.

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The chemistry of localized singlet 1,3-diradicals (biradicals): from putative intermediates to persistent species and unusual molecules with a π-single bonded character

Cited by 156 publications

References 90 publications

Nitrogen Analogues of Thiele’s Hydrocarbon

Nitrogen Analogues of Thiele’s Hydrocarbon

Photochemically induced radical reactions with furanones

Tunable Cyclopentane-1,3-diyls Generated by Insertion of Isonitriles into Diphosphadiazanediyls

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