合成和电子结构的确定N-基替代 bis ((imino) pyridine铁胺基呈现旋转交叉行为
Amanda C Bowman1, Carsten Milsmann, Eckhard Bill
1Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, USA.
Journal of the American Chemical Society
|October 12, 2011
概括
新的铁胺复合物表现出旋转交叉行为,在低旋转和高旋转状态之间进行过渡. 这种行为受到基替代物的影响,并提供了对其电子结构和结合的见解.
科学领域:
- 有机金属化学 有机金属化学
- 协调化学 协调化学
- 材料科学 材料科学 材料科学
背景情况:
- 双胺连接物是协调化学中的多功能支架.
- 铁胺复合物由于其多样化的电子特性和潜在应用而引起人们的兴趣.
研究的目的:
- 为了合成和表征新的N-基替代 bis ((imino) pyridine铁胺复合物.
- 为了研究这些新化合物的旋转交叉行为和电子结构.
主要方法:
- 通过向铁二基前体添加亚化物合成铁二胺复合物.
- 使用SQUID磁力测量,X射线衍射和Mössbauer光谱学进行了表征.
- 计算研究和X射线吸收光谱学用于电子结构分析.
主要成果:
- 成功合成了三种新的N-基替代 bis ((imino) pyridine铁胺化合物复合物.
- 在同位素铁胺基中观察到旋转交叉行为,其中一个显示出更完整的过渡.
- X射线衍射揭示了带有短Fe-N(imide) 键的平面结构,表明联体的两电子减少.
- 莫斯巴乌尔光谱学证实了二磁性基态,并支持了旋转交叉,为S=0到S=1的过渡产生了热力学参数.
结论:
- 合成的复合物表现出可调节的旋转交叉特性.
- 电子结构最好描述为一个低旋转的铁中心与S=0状态的 imidyl 基相结合.
- 一个以铁为中心的旋转过渡到一个中间旋转铁离子解释了在更高温度下S=1状态.
相关概念视频
01:25Basicity of Heterocyclic Aromatic Amines
Heterocyclic amines, where the N atom is a part of an alicyclic system, are similar in basicity to alkylamines. Interestingly, the heterocyclic amine having a nitrogen atom as part of an aromatic ring has much less basicity than its corresponding alicyclic counterpart. For this reason, as presented in Figure 1, piperidine (pKb = 2.8) is significantly more basic than pyridine (pKb = 8.8).
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.
01:20Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)
Two NMR-active nuclei bonded to a central atom can be involved in geminal or two-bond coupling. Geminal coupling is commonly seen between diastereotopic protons in chiral molecules and unsymmetrical alkenes, among others.
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
02:52Stereoisomerism
Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...
Isomers are different chemical species that have the same chemical formula.
Transition metal complexes often exist as geometric isomers, in which the same atoms are connected through the same types of bonds but with differences in their orientation in space. Coordination complexes with two different ligands in the cis and trans positions from a ligand of interest form isomers. For example, the octahedral [Co(NH3)4Cl2]+ ion has two isomers (Figure 1) In the cis...