title: Stable hydrocarbon diradical, an analogue of trimethylenemethane.
abstract: Hydrocarbon diradical 1, a new stable, 3-fold symmetric analogue of trimethylenemethane (TMM) with no heteroatom perturbation, is prepared and studied. Such diradicals should provide new building blocks for high-spin hydrocarbon polyradicals with very strong net ferromagnetic coupling. Magnetic studies (SQUID) and EPR spectroscopy indicate that 1 in tetrahydrofuran-d8 (THF-d8) possesses a triplet (S = 1) ground state, with strong ferromagnetic coupling. After annealing at room temperature, the EPR spectra of 1 (approximately 0.02 M in frozen THF-d8) consist of a single narrow resonance (deltaH(pp) < 1 G), and intermolecular antiferromagnetic coupling is increased by 1 order of magnitude. This behavior is consistent with the presence of exchange narrowing, thus suggesting aggregation of 1 in THF-d8. Blue solutions of 1 in THF-d8 possess a strong UV-vis absorption band at lambda(max) approximately 640 nm. Diradical 1 in THF-d8 is stable (or persistent) at room temperature, with no detectable decomposition for at least 2 days.
authors.affiliation: Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, USA. arajca1@unl.edu
authors.forename: Andrzej
authors.initials: A
authors.lastname: Rajca
authors.forename: Kouichi
authors.initials: K
authors.lastname: Shiraishi
authors.forename: Matthew
authors.initials: M
authors.lastname: Vale
authors.forename: Hongxian
authors.initials: H
authors.lastname: Han
authors.forename: Suchada
authors.initials: S
authors.lastname: Rajca
mesh_terms: D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals / Q000737:chemistry; D006841:Hydrocarbons, Aromatic / Q000138:chemical synthesis / Q000737:chemistry*; D008280:Magnetics; D008697:Methane / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry*; D015394:Molecular Structure; D013056:Spectrophotometry, Ultraviolet
chemical_list: D005609:Free Radicals; D006841:Hydrocarbons, Aromatic; D008697:Methane