Synthesis, Crystal Structure, and Physical Properties of Sterically Unprotected Hydrocarbon Radicals

Kubo, Takashi; Katada, Yasuyuki; Shimizu, Akihiro; Hirao, Yasukazu; Sato, Kazunobu; Takui, Takeji; Uruichi, Mikio; Yakushi, Kyuya; Haddon, Robert C.

doi:10.1021/ja2065768

Cited by 82 publications

(84 citation statements)

References 33 publications

(23 reference statements)

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“…This is significantly larger than the π-stacking separation found in planar hydrocarbon radicals (≈3 Å), for which recent studies revealed a combination of strong SOMO–SOMO overlap with dispersion forces giving rise to the so-called multicenter bonding configuration. 9,37−39 Thus, a direct magnetic interaction (overlap) is unlikely to contribute to the attractive interaction of radicals in the self-assembled BDPA chains on Au(111).…”

Section: Resultsmentioning

confidence: 99%

Interactions and Self-Assembly of Stable Hydrocarbon Radicals on a Metal Support

et al. 2012

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Stable hydrocarbon radicals are able to withstand ambient conditions. Their combination with a supporting surface is a promising route toward novel functionalities or carbon-based magnetic systems. This will remain elusive until the interplay of radical–radical interactions and interface effects is fundamentally explored. We employ the tip of a low-temperature scanning tunneling microscope as a local probe in combination with density functional theory calculations to investigate with atomic precision the electronic and geometric effects of a weakly interacting metal support on an archetypal hydrocarbon radical model system, i.e., the exceptionally stable spin-1/2 radical α,γ-bisdiphenylene-β-phenylallyl (BDPA). Our study demonstrates the self-assembly of stable and regular one- and two-dimensional radical clusters on the Au(111) surface. Different types of geometric configurations are found to result from the interplay between the highly anisotropic radical–radical interactions and interface effects. We investigate the interaction mechanisms underlying the self-assembly processes and utilize the different configurations as a geometric design parameter to demonstrate energy shifts of up to 0.6 eV of the radicals’ frontier molecular orbitals responsible for their electronic, magnetic, and chemical properties.

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Section: Resultsmentioning

confidence: 99%

Interactions and Self-Assembly of Stable Hydrocarbon Radicals on a Metal Support

et al. 2012

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“…Fortunately, I succeeded in the isolation of a cation species of 8 , and after coming back to Japan, I continued this research and finally isolated an n ‐butyl derivative of 8 in a crystalline form. X‐ray crystallographic analysis revealed that the radical exists in a discrete form in the solid state (Figure ) . This is the first hydrocarbon radical that can survive in the solid state only by thermodynamic stabilization.…”

Section: Phenalenylmentioning

confidence: 99%

Phenalenyl‐Based Open‐Shell Polycyclic Aromatic Hydrocarbons

Kubo

2014

The Chemical Record

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200

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The phenalenyl radical is a polycyclic aromatic hydrocarbon (PAH) radical. Owing to its widely distributed spin structure, phenalenyl is relatively stable compared to other hydrocarbon radicals and has been studied from the viewpoint of its application to electroconductive and magnetic materials. In addition, a strong intermolecular spin-spin coupling nature is another feature of phenalenyl. This account summarizes my studies so far into PAH radicals containing the phenalenyl scaffold in terms of their amphoteric redox properties and singlet biradical character, which strongly rely on the characteristic electronic structure, that is, non-bonding character and sixfold symmetry of a singly occupied molecular orbital of the phenalenyl radical.

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“…[8] In both DT 2 and PT 2 ,t he CÀC bonds connecting the monomers are remarkably longer (1.638(2) for DT 2 and 1.633(10) and 1.653(10) for PT 2 ) than au sual C(sp 3 ) À C(sp 3 )b ond (1.54 ). [14][15][16][17][18][19] Figure 3cshows the bond lengths in JDC determined by X-ray analysis. In ac loser radical pair, there are nine intermolecular short contacts between sp 2 carbon atoms,which are even shorter than the van der Waals contact of sp 2 carbon atoms (3.4 ;F igure 3b).…”

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confidence: 99%

The Divergent Dimerization Behavior of N‐Substituted Dicyanomethyl Radicals: Dynamically Stabilized versus Stable Radicals

Okino

Hira²,

Inoue

et al. 2017

Angew Chem Int Ed

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Herein, we demonstrate that the dimerization behavior of amine-substituted dicyanomethyl radicals can be switched from σ- to π-dimerization simply by varying the electron-donating substituents. For dicyanomethyl radicals with a 4,4'-ditolylamine (DT ) or a phenothiazine (PT ) substituent, the monomeric radical form and the corresponding dimer connected by a reversible C-C bond (σ-dimer) are in equilibrium in solution. On the other hand, the radical with the julolidine skeleton (JD ) does not undergo σ-dimerization and was isolated as a stable radical in spite of the absence of bulky protecting groups. X-ray single-crystal analysis revealed that JD forms the π-dimer in the crystalline state, and variable-temperature spectroscopy showed that JD is in equilibrium with the π-dimer in toluene solution. DFT calculations point to the importance of electrostatic interactions as a driving force for the π-dimerization of JD because of its polarized structure.

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Synthesis, Crystal Structure, and Physical Properties of Sterically Unprotected Hydrocarbon Radicals

Cited by 82 publications

References 33 publications

Interactions and Self-Assembly of Stable Hydrocarbon Radicals on a Metal Support

Interactions and Self-Assembly of Stable Hydrocarbon Radicals on a Metal Support

Phenalenyl‐Based Open‐Shell Polycyclic Aromatic Hydrocarbons

The Divergent Dimerization Behavior of N‐Substituted Dicyanomethyl Radicals: Dynamically Stabilized versus Stable Radicals

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