title: New insights into the hexaphenylethane riddle: formation of an α,o-dimer.
abstract: Upon reduction of a 1H-cyclobuta[de]naphthalene-4,5-diylbis(diarylmethylium) species, a new CC bond is formed between the Cα and Cortho atoms of the two chromophores, which presents an unprecedented coupling pattern for the dimerization of two trityl units. By attaching an annulated cyclobutane ring at the opposite peri position of the naphthalene core, the distance between the Cα  carbon atoms was elongated beyond the limit of σ-bond formation through "scissor effects". The suppression of Cα Cα bond formation, which would lead to hexaphenylethane-type compounds, is key to the first successful isolation of the α,o-adducts. The 5-diarylmethylene-6-triarylmethyl-1,3-cyclohexadiene unit in the α,o-adducts is stable, and isomerization of the cyclohexadiene unit into an aromatic system was not observed. The newly formed Cα Cortho bond was cleaved upon two-electron oxidation to regenerate the dicationic dye.
authors.affiliation: Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810 (Japan).
authors.forename: Yasuto
authors.initials: Y
authors.lastname: Uchimura
authors.forename: Takashi
authors.initials: T
authors.lastname: Takeda
authors.forename: Ryo
authors.initials: R
authors.lastname: Katoono
authors.forename: Kenshu
authors.initials: K
authors.lastname: Fujiwara
authors.forename: Takanori
authors.initials: T
authors.lastname: Suzuki
keywords: X-ray diffraction; dimerization; radicals; steric hindrance; strained molecules