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"分离"与"接触"离子对结构在溶液中从它们的晶体状态:对丁二二作为混合价值离子的动态影响
Jian-Ming Lü1, Sergiy V Rosokha, Sergey V Lindeman
1Chemistry Department, University of Houston, Houston, TX 77204-5003, USA.
Journal of the American Chemical Society
|February 11, 2005
概括
研究人员通过分离晶体盐来量化动态离子对. 这项研究使用X射线分析和光谱学来区分二二二化 (DNB(-)) 的"分离"和"接触"离子对,证实它们在溶液中的持久性.
科学领域:
- 物理化学 物理化学
- 超分子化学 超分子化学
- 晶体学 晶体学是指结晶学.
背景情况:
- 从历史上看,动态离子对在溶液中被质量理解.
- 晶体盐的低温隔离允许直接结构定量.
- 丁二化离子 (DNB(-)) 作为研究离子对结构的模型.
研究的目的:
- 为了在晶体学上区分和结构上表征DNB的"分离"和"接触"离子对.
- 用光谱分析研究这些离子对结构在溶液中的持久性.
- 阐明DNB(-) 离子对的电子和动态特性.
主要方法:
- 低温分离结晶离子对盐,使用镜还原和宏环连接物 (密和皇冠).
- 射线晶体学以确定"分离" (K(L(C)) ((+) ///DNB(-)) 和"接触" (K(L(E)) (((+) DNB(-)) 离子对中的明显的内部离子分离.
- 近红外 (NIR) 和电子自旋共振 (ESR) 光谱用于光谱分析和电子/动态性质的阐明.
主要成果:
- 基于内部离子距离的"分离"和"接触"离子对的晶体学差异化.
- 在NIR光谱中观察间隔转换,证实DNB(-) 是一种混合价值的离子.
- 在固态和溶液光谱中匹配振动微型结构图案,表明结构持久性.
- 使用马库斯-赫什理论将NIR模式分配给DNB中的对称 (分离) 和不对称 (接触) 电子移位.
- 取决于温度的ESR光谱显示了易于异构,离子分离和溶液中的反离子交换.
结论:
- DNB的晶体离子对结构是直接可量化的,反映了溶液的行为.
- "分离"的离子对表现出对称的电子移位,而"接触"的离子对表现出不对称的分布.
- 溶液中的动态离子对行为,包括异体化和交换,通过光谱方法很好地描述.
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