Yamamoto Takashi, Uruichi Mikio, Yamamoto Kaoru, Yakushi Kyuya, Kawamoto Atushi, Taniguchi Hiromi
Institute for Molecular Science, Myodaiji, Okazaki 444-8585, Japan.
J Phys Chem B. 2005 Aug 18;109(32):15226-35. doi: 10.1021/jp050247o.
We reinvestigated the two C=C stretching modes of the five-membered rings of ET (ET = bis(ethylenedithio)tetrathiafulvalene), namely, nu(2) (in-phase mode) and nu(27) (out-of-phase mode). The frequency of the nu(27) mode of ET(+) was corrected to be approximately 1400 cm(-1), which was identified from the polarized infrared reflectance spectra of (ET)(ClO(4)), (ET)(AuBr(2)Cl(2)), and the deuterium- or (13)C-substituted compounds of (ET)(AuBr(2)Cl(2)). It was clarified from DFT calculations that the frequency of the nu(27) mode of the flat ET(0) molecule was significantly different from that of the boat-shaped ET(0) molecule. We obtained the linear relationship between the frequency and the charge on the molecule, rho, for the flat ET molecule, which was shown to be nu(27)(rho) = 1398 + 140(1 - rho) cm(-1). The frequency shift due to oxidation is remarkably larger than that reported in previous studies. The fractional charges of several ET salts in a charge-ordered state can be successfully estimated by applying this relationship. Therefore, the nu(27) mode is an efficient probe to detect rho in the charge-transfer salts of ET. Similarly, a linear relationship for the nu(2) mode was obtained as nu(2)(rho) = 1447 + 120(1 - rho). This relationship was successfully applied to the charge-poor molecule of theta-type ET salts in the charge-ordered state but could not be applied to the charge-rich molecule. This discrepancy was semiquantitatively explained by the hybridization between the nu(2) and nu(3) modes.
我们重新研究了二（乙撑二硫）四硫富瓦烯（ET）五元环的两种C=C伸缩模式，即ν(2)（同相模式）和ν(27)（异相模式）。ET(+)的ν(27)模式频率被校正为约1400 cm⁻¹，这是从(ET)(ClO₄)、(ET)(AuBr₂Cl₂)以及(ET)(AuBr₂Cl₂)的氘代或¹³C取代化合物的偏振红外反射光谱中确定的。从密度泛函理论计算中可以明确，平面ET(0)分子的ν(27)模式频率与船形ET(0)分子的显著不同。我们得到了平面ET分子的频率与分子上电荷ρ之间的线性关系，即ν(27)(ρ) = 1398 + 140(1 - ρ) cm⁻¹。氧化引起的频率 shift 比先前研究报道的要大得多。通过应用这种关系，可以成功估计几种处于电荷有序状态的ET盐的分数电荷。因此，ν(27)模式是检测ET电荷转移盐中ρ的有效探针。同样，对于ν(2)模式也得到了线性关系，即ν(2)(ρ) = 1447 + 120(1 - ρ)。这种关系成功应用于处于电荷有序状态的θ型ET盐的贫电荷分子，但不适用于富电荷分子。这种差异通过ν(2)和ν(3)模式之间的杂化得到了半定量解释。
