五种还原Keggin结构杂多阴离子的ESR谱

本文报道了五种具有Keggin结构的还原杂多阴离子的溶液和-150℃冷冻ESR谱,它们是SiV₂Mo₁₀O₄₀^6-、bSiV₂Mo₉O₄₀^7--、PV₃Mo₉O₄₀^6-、PV₃W₉O₄₀^6-和VV₃W₉O₄₀^6-。在室温下pH≤3时,所有杂多酸阴离子均为8条锐线,pH=7-8时,均为8+15条线并且随着放置时间增长逐步变成8条线。在-150℃时均呈现出V⁴⁺8条线的复杂粉末谱,作者根据一种修正的Ble-aney方法成功地模拟了这些冷冻谱,得出g_‖、g_⊥、A_‖、A_⊥,按照DeArmond理论计算了近似的K、α值并讨论了它们的物理意义。最后从异构体的数目和简并度的观点初步解释了观察不到V₃物种22条超精细线的原因。Back

THE ESR SPECTRA OF FIVE REDUCED KEGGIN 'S HETEROPOLYANIONS

The ESR spectra of five reduced heteropolyanions belonging to the Keggin structure are reported in this paper. They are SiV₂Mo₁₀O₄₀^6-, SiV₃Mo₉O₄₀^7-, PV₃MO₉O₄₀^6-, PV₃W₉O₄₀^6- and VV₃W₉O₄₀^6-. At room temperature and pH≤ 3, their spectra contained 8 hfs lines, while at pH=7-8, 8+15 hyperfine lines. Their shape change gradually and finally turned to 8-lines spectrum after a long period of time. The frozen spectra at - 150℃ exhibited complicated 8 line spectra which were successfully simulated based on slightly modified Bleaney's theory.The ESR parameters g_‖ g_⊥ A_‖ A_⊥ were determined and the approximate K, α values were calculated based on DeArmond's theory. The physical meaning of the results are discussed and the failure of observing the 22 hfs lines of V_s species are primarily explained according to the number and degeneracy of the isomers present in the V₃ species.