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铁和协调复合物的电子和原子自我交换反应
Jeffrey C Yoder1, Justine P Roth, Emily M Gussenhoven
1Department of Chemistry, University of Washington, Box 351700, Seattle, WA 98195-1700, USA.
Journal of the American Chemical Society
|February 27, 2003
概括
这项研究研究了铁和复合体中的电子和原子自我交换反应. 由于旋转状态效应,铁复合体在较低的温度下表现出更快的自我交换,而复合体表现出由于旋转状态相互转换的缓慢速度.
科学领域:
- 协调化学 协调化学
- 无机化学 无机化学 有机化学
- 物理化学 物理化学
背景情况:
- 自交换反应对于理解协调复合体中的电子和原子转移过程至关重要.
- 铁和复合体与捐赠体是生物系统和催化剂的相关模型.
- 研究连接体结构和金属自旋状态对反应动力学的影响至关重要.
研究的目的:
- 量化铁 2,2'-bi(tetrahydro) pyrimidine (H(2) bip) 复合物的电子和原子自我交换率.
- 为了确定 2,2'-biimidazoline (H(2)bim) 复合物的自我交换率.
- 阐明控制这些反应的机械细节,包括自旋状态效应和动态同位素效应.
主要方法:
- 用质子核磁共振 (1H NMR) 光谱来监测自我交换反应.
- 动力学研究涉及不同的度和温度,以确定速率常数和激活参数.
- 马库斯交叉关系被应用来估计复合物的自我交换率.
主要成果:
- 铁复合体表现出在1.1 x 10 5 M 1 s 1 的电子自我交换 (k) 和原子自我交换 (k) 的电子自我交换. 在1.1 × 10 (4) M (-1) s (-1) 中.
- 两种铁自我交换反应都显示出负激活度,这归因于较低温度下低旋转状态的优势.
- 复合体表现出缓慢的自我交换率 (<或=10(-3) M(-1) s(-1),与高旋转/低旋转互换相关.
结论:
- 铁复合体自我交换的温度依赖性表明旋转状态人群的重要作用.
- 温和的动态同位素效应和负激活参数差异意味着在原子转移中进行了广泛的道化.
- 缓慢的自我交换率主要由电子转移时自旋状态变化的能量控制.
相关概念视频
02:45Valence Bond Theory
Overview of Valence Bond Theory
03:45Formation of Complex Ions
A type of Lewis acid-base chemistry involves the formation of a complex ion (or a coordination complex) comprising a central atom, typically a transition metal cation, surrounded by ions or molecules called ligands. These ligands can be neutral molecules like H2O or NH3, or ions such as CN− or OH−. Often, the ligands act as Lewis bases, donating a pair of electrons to the central atom. These types of Lewis acid-base reactions are examples of a broad subdiscipline called coordination...
02:51Metal-Ligand Bonds
The hemoglobin in the blood, the chlorophyll in green plants, vitamin B-12, and the catalyst used in the manufacture of polyethylene all contain coordination compounds. Ions of the metals, especially the transition metals, are likely to form complexes.
In these complexes, transition metals form coordinate covalent bonds, a kind of Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in...
In these complexes, transition metals form coordinate covalent bonds, a kind of Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in...
02:34Structural Isomerism
Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can be...
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can be...
02:42Valence Bond Theory
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
03:02Colors and Magnetism
Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.