Direct Arylations for Study of the Air-Stable P‑Heterocyclic Biradical: From Wide Electronic Tuning to Characterization of the Localized Radicalic Electrons Shigekazu Ito Yasuhiro Ueta Trang Thi Thu Ngo Makoto Kobayashi Daisuke Hashizume Jun-ichi Nishida Yoshiro Yamashita Koichi Mikami 10.1021/ja409625x.s004 https://acs.figshare.com/articles/dataset/Direct_Arylations_for_Study_of_the_Air_Stable_P_Heterocyclic_Biradical_From_Wide_Electronic_Tuning_to_Characterization_of_the_Localized_Radicalic_Electrons/2351434 We have developed methods for installing aryl substituents directly on the phosphino groups of the 1,3-diphosphacyclobutane-2,4-diyl system. The aryl substituents tuned the electronic and structural characteristics of the biradical unit both in solution and in the solid state. 1-<i>tert</i>-butyl-2,4-bis­(2,4,6-tri-<i>tert-</i>butylphenyl)-1,3-diphosphacyclobuten-4-yl anion, prepared from phosphaalkyne (Mes*CP; Mes* = 2,4,6-<i>t</i>Bu<sub>3</sub>C<sub>6</sub>H<sub>2</sub>) and <i>t</i>-butyllithium, was allowed to react with an electron-deficient N-heterocyclic reagent. The corresponding N-heteroaryl-substituted P-heterocyclic biradicals were produced via S<sub>N</sub>Ar reactions. Biradicals bearing perfluorinated pyridyl substituents exhibited photoabsorption properties comparable to those of previously reported derivatives because the highest occupied and lowest unoccupied molecular orbit levels were reduced by a similar amount. In contrast, the triazine substituent reduced the band gap of the biradical unit, and the large red shift in the visible absorption and high oxidation potential were further tuned via subsequent S<sub>N</sub>Ar and Negishi coupling reactions. The amino-substituted triazine structure provided a strongly electron-donating biradical chromophore, which produced unique p-type semiconducting behavior even though there was no obvious π-overlap in the crystalline state. The single-electron transfer reaction involving Mes*CP, phenyllithium, and iodine afforded 1,3-diphenyl-2,4-bis­(2,4,6-tri-<i>tert</i>-butylphenyl)-1,3-diphosphacyclobutane-2,4-diyl via the intermediate P-heterocyclic monoradical. The tetraaryl-substituted symmetric biradical product was used to determine the electron density distribution from the X-ray diffraction data. The data show highly localized radicalic electrons around the skeletal carbon atoms, moderately polarized skeletal P–C bonds in the four-membered ring, and no covalent transannular interaction. 2013-11-20 00:00:00 Biradical biradical unit SNAr electron density distribution triazine 3C Localized Radicalic ElectronsWe Me covalent transannular interaction perfluorinated pyridyl substituents aryl substituents data Wide Electronic Tuning