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相关概念视频

Thermal Electrocyclic Reactions: Stereochemistry01:17

Thermal Electrocyclic Reactions: Stereochemistry

The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Valence Bond Theory02:42

Valence 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...
Valence Bond Theory02:45

Valence Bond Theory

Overview of Valence Bond Theory
Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)01:22

Spin–Spin Coupling: Three-Bond Coupling (Vicinal Coupling)

Vicinal or three-bond coupling is commonly observed between protons attached to adjacent carbons. Here, nuclear spin information is primarily transferred via electron spin interactions between adjacent C‑H bond orbitals. This generally favors the antiparallel arrangement of spins, so 3J values are usually positive.
The extent of coupling depends on the C‑C bond length, the two H‑C‑C angles, any electron-withdrawing substituents, and the dihedral angle between the involved orbitals. The...
Aromatic Hydrocarbon Cations: Structural Overview01:18

Aromatic Hydrocarbon Cations: Structural Overview

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 with both...
Photochemical Electrocyclic Reactions: Stereochemistry01:26

Photochemical Electrocyclic Reactions: Stereochemistry

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

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Line Shape Analysis of Dynamic NMR Spectra for Characterizing Coordination Sphere Rearrangements at a Chiral Rhenium Polyhydride Complex
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在Pd(II),Ti(IV) 含有环和子分子之间,Ti(IV) 中心的动态相互转换.

Shuichi Hiraoka1, Yoko Sakata, Mitsuhiko Shionoya

  • 1Department of Chemistry, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan. hiraoka@chem.s.u-tokyo.ac.jp

Journal of the American Chemical Society
|July 11, 2008
PubMed
概括

研究人员使用基甲基醇连接体,和创造了新的超分子复合体. 这些复合体是相互可转换的,表现出由成分分数和基本性驱动的动态Ti4+中心的协调变化.

科学领域:

  • 协调化学 协调化学
  • 超分子化学 超分子化学
  • 材料科学 材料科学 材料科学

背景情况:

  • 超分子化学侧重于非共价相互作用来构建复杂的结构.
  • 异质核复合体由于存在多个金属中心,因此具有独特的特性.
  • 和复合物因其催化和结构应用而被广泛研究.

研究的目的:

  • 构建新的异质核,超分子环和子复合体.
  • 研究不同的Ti4+中心协调结构之间的相互可转换性.
  • 了解影响Ti4+中心结构转变的因素.

主要方法:

  • 合成的异质核复合物使用一个化类甲基醇连接体,TiO(acac) 2,和PdCl2 ((CH3CN) 2.
  • 用光谱和晶体分析来描述这些复合物的特征.
  • 研究反应条件,包括成分分数和基本性,以研究相互转换.

主要成果:

  • 成功构建了异质核,超分子环和子复合体.
  • 证明了两种不同的Ti4+中心协调结构之间的定量相互转换:Ti ((catecholato) 3) 和TiH ((catecholato) 2) ((acetylacetonato).
  • 确定了组成部分和基本性作为推动Ti4+中心结构变化的关键因素.

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Vibrational Spectra of a N719-Chromophore/Titania Interface from Empirical-Potential Molecular-Dynamics Simulation, Solvated by a Room Temperature Ionic Liquid
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Using Cyclic Voltammetry, UV-Vis-NIR, and EPR Spectroelectrochemistry to Analyze Organic Compounds
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Line Shape Analysis of Dynamic NMR Spectra for Characterizing Coordination Sphere Rearrangements at a Chiral Rhenium Polyhydride Complex
10:52

Line Shape Analysis of Dynamic NMR Spectra for Characterizing Coordination Sphere Rearrangements at a Chiral Rhenium Polyhydride Complex

Published on: July 27, 2022

Vibrational Spectra of a N719-Chromophore/Titania Interface from Empirical-Potential Molecular-Dynamics Simulation, Solvated by a Room Temperature Ionic Liquid
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Vibrational Spectra of a N719-Chromophore/Titania Interface from Empirical-Potential Molecular-Dynamics Simulation, Solvated by a Room Temperature Ionic Liquid

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结论:

  • 该研究提出了具有动态Ti4+中心协调的新型异质核超分子复合体.
  • 相互转换机制为这些复杂的灵活性和响应能力提供了洞察力.
  • 这些发现有助于理解协调化学中的自我组装和结构多样性.