Structures and Reactivities of Negatively-Charged Clusters in Supercritical Carbon Dioxide

超临界二氧化碳中带负电团簇的结构和反应性

• 批准号: 12440160
• 负责人: NAGATA Takashi
• 金额: $ 6.14万
• 依托单位: The University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 2000
• 资助国家: 日本
• 起止时间: 2000 至 2002
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-12440160/
• 关键词: Supercritical carbon dioxide; Mobility measurement; Negatively-charged clusters; Ab initio calculations; Photodestruction spectrum; Radical reactions; Negative-ion chemistry; 局所クラスター構造; 電子束縛状態; イオン移動度; クラスター構造

The present study aims for (i) the spectroscopic detection of (CO_2)_n^-clusters formed in a supercritical carbon dioxide (hereafter referred to as {(CO_2)_n^-}_<scf>) and (ii) the systematic study of reactivities of {(CO_2)_n^-}_<scf> in order to explore the negative-ion chemistry in supercritical carbon dioxide. The findings are summarized as follows :1.The formation of {(CO_2)_n^-}_<scf> is detected by the measurement of negative charge transport in gaseous, supercritical and liquid carbon dioxide. The mobility measurement over a wide range of CO_2 density revealed that the nascent {(CO_2)_n^-}_<scf> formed around the excess electrons are primarily in the size range of n = 5 -6, and that the negative charge transport occurs with both the hopping and the conduction band mechanisms.2.The electronic and geometrical structures of (CO_2)_n^-and [(CO_2)_n^-(H_2O)_m] are investigated by ab initio calculations at MP2/6-311++G(d, p) level for small clusters and MP2/6-31 for larger ones, demo … More nstrating the existence of almost-isoenergetic isomers having different electronic structures ("electronic isomers").3.An effort has been made to probe the nascent {(CO_2)_n^-}_<scf> formed in a supercritical pure carbon dioxide by ns time-resolved photoabsorption spectroscopy. The transient photoabsorption signal has not been detected due possibly to either small quantum yield for the {(CO_2)_n^-}_<scf> formation or small cross sections for the {(CO_2)_n^-} photoabsorption.4.The photodestruction spectra of (CO_2)_n^-are measured in the visible and uv regions by means of photofragment mass spectrometry, which provide information on the fundamental electronic properties of (CO_2)_n^-species.5.Mass spectrometric studies have revealed the reactivity of gas-phase (CO_2)_n^-and CO_2^-(H_2O)_n as carboxylation reagents for alkyl halides and conjugated alkenes. The hydration stabilizes CO_2^<・-> without deteriorating its radical reactivity. These findings open up a possibility of novel {(CO_2)_n^-}_<scf> chemistry in a supercritical carbon dioxide. Less

本研究旨在(1)对超临界二氧化碳中形成的（CO_2）_n^-簇（以下简称{(CO_2)_n^-}_<scf>）进行光谱检测，(2)系统研究{(CO_2)_n^-}_<scf>的反应性，以探索超临界二氧化碳中的负离子化学。研究结果总结如下：1。{(CO_2)_n^-}_<scf>的形成是通过测量气态、超临界和液态二氧化碳中的负电荷输运来检测的。在较宽的CO_2密度范围内的迁移率测量表明，在多余电子周围形成的新生{(CO_2)_n^-}_<scf>主要在n = 5 ~ 6的尺寸范围内，负电荷的输运既以跳变机制发生，也以导带机制发生。在MP2/6-311++G（d, p）水平和MP2/6-31水平上研究了（CO_2）_n^和[(CO_2)_n^-(H_2O)_m]的电子和几何结构，进一步说明了具有不同电子结构的几乎同能异构体（“电子异构体”）的存在。本文尝试用ns时间分辨光吸收光谱法探测超临界纯二氧化碳中形成的新生{(CO_2)_n^-}_<scf>。由于{(CO_2)_n^-}_<scf>形成的量子产率小或{(CO_2)_n^-}光吸收的截面小，所以暂态光吸收信号未被检测到。利用光碎片质谱法测量了（CO_2）_n^-在可见光和紫外区的光破坏光谱，提供了（CO_2）_n^-物质的基本电子性质信息。质谱研究揭示了气相（CO_2）_n^和CO_2^-(H_2O)_n作为烷基卤化物和共轭烯烃羧化试剂的反应性。水合作用稳定了CO_2^<·->而不降低其自由基反应活性。这些发现开辟了在超临界二氧化碳中产生新的{(CO_2)_n^-}_<scf>化学的可能性。少

项目成果

L.Zhu et al.: "Photodissociation of gas-phase I_3^- : product branching in the visible and uv regions"Chemical Physics Letters. 350. 233-239 (2001)

L.Zhu 等人：“气相 I_3^- 的光解离：可见光和紫外区域的产物分支”《化学物理快报》。

R.A.Holroyd, K.Itoh, M.Nishikawaet: "Density inhomogeneities and electron mobility in supercritical xenon"Journal of Chemical Physics. 118. 706-710 (2003)

R.A.Holroyd、K.Itoh、M.Nishikawaet：“超临界氙中的密度不均匀性和电子迁移率”化学物理杂志。

K.Itoh et al.: "Ion mobilities in supercritical ethane, xenon, and carbon dioxide"Chemical Physics Letters. A105. 703-709 (2001)

K.Itoh 等人：“超临界乙烷、氙气和二氧化碳中的离子迁移率”化学物理快报。

L.Zhu, K.Takahashi, M.Saeki, T.Tsukuda, T.Nagata: "Photodissociation of gas-phase I_3^-: product branching in the visible and uv regions"Chemical Physics Letters. 350. 233-239 (2001)

L.Zhu、K.Takahashi、M.Saeki、T.Tsukuda、T.Nagata：“气相 I_3^- 的光解离：可见光和紫外区域的产物分支”《化学物理快报》。

T.Tsukuda, L.Zhu, M.Saeki, T.Tsukuda, T Nagata: "Photochemistry of (NO)_n^-as studied by photofragment mass spectrometry"International Journal of Mass Spectrometry. 220. 137-143 (2002)

T.Tsukuda、L.Zhu、M.Saeki、T.Tsukuda、T Nagata：“通过光碎片质谱法研究 (NO)_n^-的光化学”国际质谱杂志。