Browsing by Author "Asami, Nobuyuki"

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Nanosecond Time-resolved Infrared Spectra and Structure of the Charge-transfer State of 9,9 '-Bianthryl in Acetonitrile
(2012-06-05)
Asami, Nobuyuki
;
Yabumoto, Sohshi
;
Shigeto, Shinsuke
;
Takaya, Tomohisa
;
Hamaguchi, Hiro-o
Nanosecond time-resolved infrared spectra of photoexcited 9,9'-bianthryl (BA) and its deuterated derivative (BA-d(18)) were recorded in acetonitrile-d(3) and cyclohexane-d(12). The charge-transfer (CT) bands observed at the 1200-1400 cm(-1) region are contributed mostly by the intra- and inter-ring CC stretch vibrations. The intrinsic frequency of the inter-ring CC stretch falls within the 1200-1400 cm(-1) region, which is consistent more with a twisted structure than with a fully conjugated planar structure of the CT state.
Two Different Charge Transfer States of Photoexcited 9,9 '-Bianthryl in Polar and Nonpolar Solvents Characterized by Nanosecond Time-Resolved Near-IR Spectroscopy in the 4500-10 500 cm(-1) Region
(2010-06-10)
Asami, Nobuyuki
;
Takaya, Tomohisa
;
Yabumoto, Soshi
;
Shigeto, Shinsuke
;
Hamaguchi, Hiro-o
Transient absorption spectra of 9,9'-bianthryl (BA) in heptane, in acetonitrile, and in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (bmimTf(2)N) are observed with a nanosecond time-resolved near-IR absorption spectrometer for the wavenumber range of 4500-10 500 cm(-1) (2200-950 nm). In nonpolar heptane solution, a broad absorption band is observed at 6700 cm(-1)(1500 urn), in addition to a strong absorption band of the locally excited (LE) state centered at 9800 cm(-1) (1020 nm). The broad band is assigned to a partial charge transfer (PCT) band. The decay time constants of the PCT band and the LE band are both (13 +/- 1) ns. The agreement of the two decay constants strongly suggests that the PCT state is in equilibrium with the LE state in heptane. In acetonitrile, an absorption band of the charge transfer (CT) state is observed at 8000 cm(-1) (1250 nm). This band decays in (41 +/- 2) ns. In bmimTf(2)N, the CT band appears at 8500 cm(-1) (1180 nm) and decays in (34 +/- 1) ns. The difference in peak position for the CT bands in acetonitrile and in bmimTf(2)N, and the PCT bands in heptane, is explained well by the model based on the charge resonance between the two equivalent electronic structures of the CT state.