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Structural Isomerism
21.4K
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...
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...
21.4K
Aromatic Hydrocarbon Cations: Structural Overview
3.6K
Cycloheptatriene is a neutral monocyclic unsaturated hydrocarbon that consists of an odd number of carbon atoms and an intervening sp3 carbon in the ring. The three double bonds in the ring correspond to 6 π electrons, which is a Huckel number, and therefore satisfies the criteria of 4n + 2 π electrons. However, the intervening sp3 carbon disrupts the continuous overlap of p orbitals. As a result, cycloheptatriene is not aromatic.
Removing one hydrogen from the intervening CH2 group...
Removing one hydrogen from the intervening CH2 group...
3.6K
Crystal Field Theory - Tetrahedral and Square Planar Complexes
48.0K
Tetrahedral Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
48.0K
Photochemical Electrocyclic Reactions: Stereochemistry
2.2K
The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
Selection Rules: Photochemical Activation
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Crystal Field Theory - Octahedral Complexes
30.5K
Crystal Field Theory
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
30.5K
Thermal and Photochemical Electrocyclic Reactions: Overview
2.9K
Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
2.9K
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在拓化学修饰的迪昂-雅各布森矿固体溶液中引起的结构变化.
Roshni Bhuvan1, Gary J Sandrock1, Sara Akbarian-Tefaghi1
1Department of Chemistry and the Advanced Materials Research Institute, The University of New Orleans, New Orleans, LA 70148, USA.
Molecules (Basel, Switzerland)
|November 27, 2025
概括
研究人员通过各种性金属离子在迪昂-雅各布森层叠的矿中探索了固体溶液. 他们发现,离子体大小影响结构和热稳定性,使矿材料的结构控制成为可能.
科学领域:
- 材料科学 材料科学 材料科学
- 固态化学 固态化学
- 晶体学 晶体学是指结晶学.
背景情况:
- 迪昂-雅各布森层叠矿是具有潜在应用的离子交换材料.
- 了解组成和结构之间的关系对于材料设计至关重要.
研究的目的:
- 为了研究连续固体溶液系列A1-xA'xLaNb2O7.
- 为了阐明这些矿的结构组成关系.
- 探索金属离子变异对结构和热性质的影响.
主要方法:
- 通过反应的末端成员进行固体溶液的拓化学合成 (ALaNb2O7).
- 在各种金属组合 (Li,Na,K,Rb,Cs) 之间形成的固体溶液的表征.
- 对选定的固体溶液进行热分析.
主要成果:
- 对相邻的金属对 (Li/Na,Na/K,K/Rb,Rb/Cs) 形成了连续的固体溶液.
- 还成功合成了一种非相邻的固体溶液 (K/Cs).
- 发现阴子协调和层对齐取决于组成,由较大的阴子度决定.
- 含有和的化合物表现出热不稳定性.
结论:
- 固体溶液系列中平均阴离子大小的系统变化允许进行结构控制.
- 这些发现有助于对用于各种应用的矿材料的理解和设计.


