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Structures and Dynamics of Negatively-Charged Molecular Clusters

带负电分子团的结构和动力学

基本信息

批准号：
06453015
负责人：
NAGATA Takashi
金额：
$ 4.03万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

项目摘要

In the present study, we have concentrated our attention to (1) the geometrical and electronic structures and (2) reactivities of negatively-charged molecular clusters :(1) The electronic structures of [(CO_2)_nROH]^-(R=H,CH_3, and C_2H_5) were investigated by photoelectron spectroscopy. The analysis of the spectra revealed that two forms of isomers coexist in [(CO_2)_nROH]^-(2*n*3) ; one has an electronic structure described as [C_2O_4^-・ROH(CO_2)_<n-2>]where the excess electron is delocalized over two CO_2 molecules, and the other involves a monomer anionic core as [CO_2^-・ROH(CO_2)_<n-1>]. This is one of the few experimental rasults which demonstrates the coexistence of isomers of negatively-charged molecular clusters having defferent electronic structures. The present findings are also supported byab initio calculations at the unrestricted Hatree-Fock levels.(2) New type of gas-phase reactions involving nagatively-charged molecular clusters were investigated by mass spectrometric technique combined with photoelectron spectroscopy. For example, we have reported reactions of (CO_2)_n^-with CH_3I leading to the formation of a novel molecular anion [CO_2CH_3I]^-, which has not been observed in the corresponding condensed-phase reaction. It turned out that [CO_2CH_3I]^-has a large vertical detachment energy, implyintg that the excess electron is delocalized over [CO_2CH_3I]^-to form an acetate-iodine complex [CH_3CO_2-I]^-. This suggests that (CO_2)_n^-reacts with CH_3I via anucleophilic process. Ab initio calculations are under way to get information on the geometrical and electronic structures of [CO_2CH_3I]^-.

在本研究中，我们重点研究了(1)带负电荷分子簇的几何结构和电子结构；(2)带负电荷分子簇的反应性；(1)用光电子能谱研究了[(CO_2)_nROH]^-（R=H，CH_3和C_2H_5）的电子结构。光谱分析表明[(CO_2)_nROH]^-(2*n*3)中存在两种形式的异构体；其中一个的电子结构描述为[C_2O_4^-·ROH(CO_2)_<n-2>]，其中多余的电子在两个CO_2分子上离域，另一个涉及一个单体阴离子核[CO_2^-·ROH(CO_2)_<n-1>]。这是为数不多的证明具有不同电子结构的带负电分子簇的异构体共存的实验结果之一。在不受限制的3 - fock水平上的从头计算也支持了本研究结果。(2)采用质谱与光电子能谱相结合的方法研究了带负电分子团簇的新型气相反应。例如，我们已经报道了（CO_2）_n^-与CH_3I的反应导致形成一种新的分子阴离子[CO_2CH_3I]^-，这在相应的缩合相反应中没有观察到。结果表明，[CO_2CH_3I]^-具有很大的垂直分离能，这意味着多余的电子在[CO_2CH_3I]^ ^上离域，形成醋酸盐-碘配合物[CH_3CO_2-I]^-。这表明（CO_2）_n^-与CH_3I发生非亲核反应。目前正在进行从头计算，以获得[CO_2CH_3I]^-的几何和电子结构信息。