Electron paramagnetic resonance of 9,9'-dianthrylmethylene. Linear aromatic ground-state triplet methylene

Wasserman, E.; Kuck, Valerie J.; Yager, W. A.; Hutton, R. S.; Greene, Frederick D.; Abegg, Victor P.; Weinshenker, Ned M.

doi:10.1021/ja00752a093

Cited by 34 publications

(28 citation statements)

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“…DPC, the simplest diaryl carbene, has been widely studied for understanding the spin‐dependent reactivity of carbenes. The C(Ph)CC(Ph) angle of DPC 3 is calculated to be 141°, in line with the experimental carbene angle of DPC 3 (about 140°) . The carbene angle of DPC 1 is smaller than that of DPC 3 and the central CC bond distance between the phenyl ring and the central carbon atom is slightly longer in DPC 1 , which can be ascribed to the greater repulsion between substituent σ‐bonds and the adjacent carbene doubly‐occupied sp 2 orbital in DPC 1 .…”

Section: Resultssupporting

confidence: 78%

Controlling the spin state of diphenylcarbene via halogen bonding: A theoretical study

Yang

et al. 2018

Int J of Quantum Chemistry

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Halogen bonding has recently become an effective tool to control the spin state of reactive carbenes. In this work, a series of the complexes of diphenylcarbene (DPC) that has a triplet ground state with several halogen bond donors RX were theoretically studied, and in particular, the influence of the formation of halogen bonding on the spin state of DPC was extensively explored. The spin flip depends on the difference of halogen bond energies between triplet and singlet, that is, when the difference is large enough a spin flip may occur. Furthermore, the variations of the geometries on complexation may induce the potential energy surfaces of different spin states to intersect, thus leading to intersystem crossing. Based on the energy analysis of the minimum energy crossing points (MECPs), the systems with a smaller MECP‐triplet energy barrier go through intersystem crossing more easily. Halogen bonds in the complexes, where a spin flip takes place, exhibit a partially covalent character, while other complexes show conventional behaviors of halogen bonding. According to charge decomposition analysis, the charge transfer from HOMO (DPC) to LUMO (RX) is identified as a prominent stabilizing interaction in the whole complexes.

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Section: Resultssupporting

confidence: 78%

Controlling the spin state of diphenylcarbene via halogen bonding: A theoretical study

Yang

et al. 2018

Int J of Quantum Chemistry

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“…The D values of typical diarylcarbenes are in the range of 0.41-0.32 cm -1 . 54,79 With the exception of di(9-anthryl-)carbene, 198 the D values of 3 154 are the smallest ever reported.…”

Section: Anthryl(phenyl)carbenesmentioning

confidence: 96%

“…198 Annealing the matrix allows the carbene to adopt its minimum energy structure, which is almost completely linear. It has been reported that the half-life of 3 10a in the matrix was 7 min at 200°C; however, it was also concluded that the stability was due to the rigidity of the environment and not due to an intrinsic lack of reactivity.…”

Section: Di(9-anthryl)carbenementioning

confidence: 99%

Persistent Triplet Carbenes

Hirai,

Itoh,

Tomioka

2009

Chem. Rev.

144

123

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“…Among diarylcarbenes, triplet di(9-anthryl)carbene ( 3 2a) exhibits the smallest D (0.113 cm -1 ) and E (0.0011 cm -1 ) values reported 22 , indicating that it has an almost linear bond geometry at the carbene centre with extensive delocalization of the unpaired electrons onto the perpendicularly attached anthryl groups. The extensive delocalization is expected to stabilize this carbene compound thermodynamically, while the perpendicular geometry of the anthryl groups stabilizes the carbene centre kinetically, through shielding with the four peri-hydrogens.…”

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confidence: 99%

Generation and characterization of a fairly stable triplet carbene

Tomioka

Iwamoto

Itakura

et al. 2001

Nature

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Most molecules are held together by covalent bonds-electron pairs jointly shared by the two atoms that are linked by the bond. Free radicals, in contrast, have at least one unpaired electron. In the case of carbon-based radicals, the carbon atom at the radical centre no longer makes four bonds with other atoms as it would do in its normal, tetravalent state. The presence of unpaired electrons renders such radicals highly reactive, so they normally occur only as transient intermediates during chemical reactions. But the discovery by Gomberg in 1900 of triphenylmethyl, the first relatively stable free radical containing a central trivalent carbon atom, illustrated that radicals with suitable geometrical and electronic structures can be stable. Compounds containing a divalent carbon atom that uses only two of its four valence electrons for bonding are usually less stable than Gomberg-type radicals with trivalent carbon. Although the role of these so-called carbenes in chemical reactions has long been postulated, they were unambiguously identified only in the 1950s. More recently, stable carbenes have been prepared, but the singlet state of these molecules, with the two nonbonding valence electrons paired, means that they are not radicals. Carbenes in the second possible electronic state, the triplet state, are radicals: the two nonbonding electrons have parallel spins and occupy different orbitals. Here we report the preparation and characterization of a triplet carbene, whose half-life of 19 minutes at room temperature shows it to be significantly more stable than previously observed triplet carbenes.

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Electron paramagnetic resonance of 9,9'-dianthrylmethylene. Linear aromatic ground-state triplet methylene

Cited by 34 publications

References 0 publications

Controlling the spin state of diphenylcarbene via halogen bonding: A theoretical study

Controlling the spin state of diphenylcarbene via halogen bonding: A theoretical study

Persistent Triplet Carbenes

Generation and characterization of a fairly stable triplet carbene

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