title: Structural study of various substituted biphenyls and their radical anions based on time-resolved resonance Raman spectroscopy combined with pulse radiolysis.
abstract: The structures of various para-substituted biphenyls (Bp-X; X = -OH, -OCH3, -CH3, -H, -CONH2, -COOH, and -CN) and their radical anions (Bp-X(•-)) were investigated by time-resolved resonance Raman spectroscopy combined with pulse radiolysis. The inter-ring C1-C1' stretching modes (ν6) of Bp-X were observed at ∼1285 cm(-1), whereas the ν6 modes of Bp-X(•-) with an electron-donating or -withdrawing substituent were significantly up-shifted. The difference (Δf) between the ν6 frequencies of Bp-X and Bp-X(•-) showed a significant dependence on the electron affinity of the substituent and exhibited a correlation with the Hammett substituent constants (σp). In contrast to Bp-H(•-) with a planar geometry, the theoretical and experimental results reveal that all Bp-X(•-) with an electron-donating or -withdrawing substituent have a slightly twisted structure. The twisted structure of Bp-X(•-) is due to the localization of the unpaired electron and negative charge density on one phenyl moiety in Bp-X(•-).
authors.affiliation: The Institute of Scientific and Industrial Research (SANKEN), Osaka University , Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan.
authors.forename: Jungkweon
authors.initials: J
authors.lastname: Choi
authors.forename: Dae Won
authors.initials: DW
authors.lastname: Cho
authors.forename: Sachiko
authors.initials: S
authors.lastname: Tojo
authors.forename: Mamoru
authors.initials: M
authors.lastname: Fujitsuka
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Majima