Catenation of Two Singlet Diradicals: Synthesis of a Stable Tetraradical (Tetraradicaloid)

Rodríguez, Amor; Tham, Fook S.; Schoeller, Wolfgang W.; Bertrand, Guy

doi:10.1002/anie.200460473

Cited by 65 publications

(38 citation statements)

References 40 publications

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“…A stable tetraradical consisting of two diboradiphosphinocyclobutane rings linked by a meta-phenylene has been reported previously. [8] Although large polycyclic aromatic hydrocarbons, such as an acene with 20 rings (icosacene: n = 20) and periacenes with more than 8 zigzag-edge rings (perioctacene, n = 8), are expected to have tetraradical ground states, such materials have not yet been prepared. [9] 4) Compound 1 a can be regarded as a member of the corannulene family, according to the corannulene concept proposed by Hellwinkel, [10] and as a smaller analogue of [8]circulene, whose derivatives, including its tetrabenzo homologues, have been prepared recently.…”

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“…[8] Although large polycyclic aromatic hydrocarbons, such as an acene with 20 rings (icosacene: n = 20) and periacenes with more than 8 zigzag-edge rings (perioctacene, n = 8), are expected to have tetraradical ground states, such materials have not yet been prepared. [9] 4) Compound 1 a can be regarded as a member of the corannulene family, according to the corannulene concept proposed by Hellwinkel, [10] and as a smaller analogue of [8]circulene, whose derivatives, including its tetrabenzo homologues, have been prepared recently. [11] Although Hellwinkel and Reiff reported the generation of a dicationic species of 1 a (with 26 p electrons) from its tetrahydro derivative 3 a in a mass spectrometry sample chamber, [12] isolation and characterization of 1 a or its derivatives have not been reported.…”

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Tetracyclopenta[def,jkl,pqr,vwx]tetraphenylene: A Potential Tetraradicaloid Hydrocarbon

et al. 2015

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A tetramesityl derivative of hitherto unknown tetracyclopenta[def,jkl,pqr,vwx]tetraphenylene (TCPTP), which is a potential tetraradicaloid hydrocarbon, was synthesized. Theoretical calculations based on spin-flip time-dependent density functional theory predict that the closed-shell D2h form of TCPTP is more stable than the open-shell D4h form with its slightly tetraradical character. The tetramesityl derivative (Mes)4 -TCPTP exhibits remarkable antiaromaticity as a result of the peripheral 20-π-electron circuit, which causes an absorption maximum at a long wavelength and a small HOMO-LUMO gap. In solution, (Mes)4 -TCPTP most likely adopts rapidly equilibrating D2h structures that interconvert via the D4h transition state. X-ray crystallographic analysis showed (Mes)4 -TCPTP as an approximate D2h structure.

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Tetracyclopenta[def,jkl,pqr,vwx]tetraphenylene: A Potential Tetraradicaloid Hydrocarbon

et al. 2015

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“…Although several boron-based diradicals have been reported, only one example of its polyradical (e.g., the tetraradical) was reported by Bertrand and coworkers. [50] We found that the Fe II ion could facilely coordinate three 5,5'-bis(dimesitylboranyl)-2,2'bipyridine (bpy B ) molecules affording the complex 45 (Scheme 20). [51] The solid state structural parameters, EPR spectroscopy and SQUID measurements showed that compound 45 is a diradical, in which two bpy B ligands are in the radical anion state.…”

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Isolable Radical Ions of Main‐Group Elements: Structures, Bonding and Properties

Tan

Wang

2018

Chin. J. Chem.

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Synthesis of stable main‐group element‐based radicals represents one of the most interesting topics in contemporary organometallic chemistry, because of their vital roles in organic, inorganic and biological chemistry as well as materials science. However, the access of stable main‐group element‐based radicals is highly challenging owing to the lack of energetically accessible orbitals in the main‐group elements. During the last decades, several synthetic strategies have been developed in obtaining these reactive species. Among them, utilizing the sterically demanding substituents and π‐conjugated ligands has proven to be an effective approach. Weakly coordinating ions (WCAs) have also been found to be exceptionally practical in synthesizing radical cations of main‐group elements. By introducing these stabilization methods, we have successfully prepared a variety of radical ions of p‐block elements in the crystalline forms, and investigated their properties by different experimental and quantum chemical calculation methods. According to the investigations, magnetic stability was observed, resulting from the intramolecular electron‐exchange interaction. Furthermore, we also found that the singlet‐triplet energy gaps of the bis(triarylamine) diradical dications can be tunable by varying the temperature. These investigations open new avenues of the main‐group element‐based radicals for a large variety of applications.

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“…[5] Synthesis of stable main-group element-based radicals is one of the most interesting topics in contemporary maingroup chemistry,and various radicals of main-group element have been structurally characterized by employing sterically encumbered and/or p-conjugated ligands. [1] Them ain-group element-based diradicals have been widely studied in the last decades, [1] whereas the corresponding polyradicals are much less investigated with afew stable examples reported, namely the silicon-centered triradical A, [6] theboron-based triradical B, [7] and tetraradical C [8] (Scheme 1). However,r adical polymers based on main-group elements rather than C/N/O are still unknown.…”

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A Main‐Group Element Radical Based One‐Dimensional Magnetic Chain

et al. 2019

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The first main-group element radical based onedimensional magnetic chain (1K) n was realized by oneelectron reduction of the pyridinyl functionalizedb orane 1 with elemental potassium in THF in the absence of 18crown-6 (18-c-6). The electron spin density of (1K) n mainly resides at the boron centers with ac onsiderable contribution from central benzene and pyridine moieties.T he spin centers exhibit an antiferromagnetic interaction as demonstrated by magnetic measurements and theoretical calculations.I nc ontrast, the reduction in the presence of 18-c-6 afforded the separated radical anion salt 1K(Crown),i nw hicht he potassium cation was trapped by THF and 18-c-6 molecules.Further one-electron reduction of 1K(Crown) and (1K) n led to the diamagnetic monomer and polymer,respectively.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

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Catenation of Two Singlet Diradicals: Synthesis of a Stable Tetraradical (Tetraradicaloid)

Cited by 65 publications

References 40 publications

Tetracyclopenta[def,jkl,pqr,vwx]tetraphenylene: A Potential Tetraradicaloid Hydrocarbon

Tetracyclopenta[def,jkl,pqr,vwx]tetraphenylene: A Potential Tetraradicaloid Hydrocarbon

Isolable Radical Ions of Main‐Group Elements: Structures, Bonding and Properties

A Main‐Group Element Radical Based One‐Dimensional Magnetic Chain

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