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

基本信息

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

项目摘要

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

本研究的目的是（i）在co_2）中形成的（co_2）_n^-clusters的光谱检测，_n^ - } _ <scf>）和（ii）{（co_2）{（CO_2）的复活性的系统研究_n^ - } _ <scf>在ordore中，超级二氧化碳中的否定性。揭示了新生{（co_2）_n^ - } _ <scf>形成的布置超过的电子是n = 5-6的尺寸范围，而负电荷传输随跳跃和避孕带机械态而发生。2.。（co_2）_n^ - 和[（co_2）_n^ - （H_2O）_m的电子和几何结构是MP2/6-311 ++ G（D，P）的初始计算，小组和2/6-31对于较大的演示，将几乎具有不同电子结构的几乎含量异构体的存在（“电子异构体”）。。（co_2）_n^-species.5。质谱研究的电子特性具有气相（CO_2）_n^ - s的反应性，使Co_2^<・>>>>>>>>小说{（co_2）_n^ - } _ <scf>超临界二氧化碳中的化学。