Isolation and Characterization of the Triradical 1,3,5‐Trimethylenebenzene

Neuhaus, Patrik; Sander, Wolfram

doi:10.1002/anie.201001393

Cited by 23 publications

(7 citation statements)

References 40 publications

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“…A considerable zero-field splitting parameter of ca. 22 mT was estimated, larger than that reported for trimethylenebenzene (14 mT) and substituted m -xylylene diradical (16 mT) …”

Section: Introductioncontrasting

confidence: 58%

“…A considerable zero-field splitting parameter of ca. 22 mT was estimated, larger than that reported for trimethylenebenzene (14 mT) 32 and substituted m-xylylene diradical (16 mT). 41 As an interesting radical structure, not surprisingly, the synthesis of truxene-5,10,15-triyl was conceived earlier.…”

Section: ■ Introductioncontrasting

confidence: 54%

“…Based on these previous results, it appears that spins confined to a smaller conjugation area are favorable for fostering stronger intramolecular coupling. Simple 1,3,5-trimethylenebenzene is the smallest unit imaginably suitable for accommodating three spin electrons . As prior studies have also shown that torsion angles may sensitively influence the strength of spin coupling, additional covalent linkages are introduced to confer a nearly completely rigid framework and warrant a strong coupling effect.…”

Section: Introductionmentioning

confidence: 99%

“…Simple 1,3,5trimethylenebenzene is the smallest unit imaginably suitable for accommodating three spin electrons. 32 As prior studies have also shown that torsion angles may sensitively influence the strength of spin coupling, 33 additional covalent linkages are introduced to confer a nearly completely rigid framework and warrant a strong coupling effect. Thus, truxene-5,10,15-triyl becomes the obvious choice.…”

Section: ■ Introductionmentioning

confidence: 99%

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Toward an Air-Stable Triradical with Strong Spin Coupling: Synthesis of Substituted Truxene-5,10,15-triyl

et al. 2020

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With the aim to achieve air-stable polyradical species manifesting strong spin coupling, synthetic endeavors are made toward triradical molecules featuring a truxene-triyl skeleton. Commonly used steric-hindering side groups such as 2,4,6trichlorophenyl and 9-anthracenyl are both found to be incompetent at stabilizing the targeted truxene triradical, which appears to be elusive from isolation and characterization. Nonetheless, singlecrystal structures of adducts formed by relevant radicals are obtained, which strongly suggests the transient existence of the designed triradicals. Finally, a truxene triradical comprising 1-anthracenyl along with two 9-anthracenyl substituents is successfully isolated and found to exhibit decent stability in air. We propose that because of the smaller dihedral angle assumed by 1-anthracenyl with respect to the plane of truxene-triyl, more effective π-conjugation allows the spin density to be more widely delocalized and distributed to the anthracenyl side groups. Thus, higher stability is gained by the triradical molecule.

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“…A considerable zero-field splitting parameter of ca. 22 mT was estimated, larger than that reported for trimethylenebenzene (14 mT) and substituted m -xylylene diradical (16 mT) …”

Section: Introductioncontrasting

confidence: 58%

Section: ■ Introductioncontrasting

confidence: 54%

Section: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Toward an Air-Stable Triradical with Strong Spin Coupling: Synthesis of Substituted Truxene-5,10,15-triyl

et al. 2020

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“…Consequently, the energy gap, Δ E , should be significantly greater than the thermal energy ( RT ) at 298 K, i.e., Δ E ≫ 0.6 kcal mol –1 . Such diradicals and polyradicals are uncommon and, especially, those with S > 1 are challenging to attain. − …”

Section: Introductionmentioning

confidence: 99%

High-Spin S = 3/2 Ground-State Aminyl Triradicals: Toward High-Spin Oligo-Aza Nanographenes

et al. 2022

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We report high-spin aminyl triradicals with near-planar triphenylene backbones. Near-planarity of the fused aminyl radicals and the 2,6,10-triphenylene ferromagnetic coupling unit (FCU), magnetically equivalent to three fused 3,4′-biphenyl FCUs, assures an effective 2pπ–2pπ overlap within the cross-conjugated π-system, leading to an S = 3/2 (quartet) ground state that is well separated from low-spin excited doublet states. Thermal populations of the low-spin (S = 1/2) excited states are detectable both by SQUID magnetometry and electron paramagnetic resonance (EPR) spectroscopy, providing doublet–quartet energy gaps, ΔE DQ, corresponding to >85% population of the quartet ground states at room temperature. Notably, EPR-based determination of ΔE DQ relies on direct detection of the quartet ground state and doublet excited states. The ΔE DQ values are 1.0–1.1 kcal mol–1, with the more sterically shielded triradical having the larger value. The half-life of the more sterically shielded triradical in 2-methyltetrahydrofuran (2-MeTHF) is about 6 h at room temperature. The less sterically shielded triradical in 2-MeTHF decomposes at 158 K with a half-life of about 4 h, while at 195 K, the half-life is still about 2 h. The dominant products of the decay of triradicals are the corresponding triamines, suggesting hydrogen atom abstraction from the solvent as the primary mechanism. This study expands the frontier of the open-shell PAHs/nanographenes, of which the unique electronic, nonlinear optical, and magnetic properties could be useful in the development of novel organic electronics, photonics, and spintronics.

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The History of Free Radical Chemistry

Tidwell

2012

Encyclopedia of Radicals in Chemistry, Biology and Materials

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Suggestions of free radicals before 1900 were realized with the discovery first of the triphenylmethyl radical, and then unstabilized aliphatic radicals in the twentieth century. The finding of new types of radicals and the development of their chemistry are outlined. Many individuals participated in the advance of free‐radical chemistry, and some of the most prominent original contributors are recognized where possible. The article provides an overview of the development of many fundamentals of free radicals, while the definitive articles in this encyclopedia on the various topics provided by leaders in their study articles describe the current state of knowledge.

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Isolation and Characterization of the Triradical 1,3,5‐Trimethylenebenzene

Cited by 23 publications

References 40 publications

Toward an Air-Stable Triradical with Strong Spin Coupling: Synthesis of Substituted Truxene-5,10,15-triyl

Toward an Air-Stable Triradical with Strong Spin Coupling: Synthesis of Substituted Truxene-5,10,15-triyl

High-Spin S = 3/2 Ground-State Aminyl Triradicals: Toward High-Spin Oligo-Aza Nanographenes

The History of Free Radical Chemistry

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