通过使用五[60]富勒烯复合物的狭窄空间来隔离平面四个成员的芳香系统
Masashi Maruyama1, Jing-Dong Guo, Shigeru Nagase
1Department of Chemistry, The University of Tokyo, Hongo, Tokyo 113-0033, Japan.
Journal of the American Chemical Society
|April 20, 2011
概括
研究人员创建了由烯配体稳定的新型芳香四肢环 (CoE3). 这些化合物表现出独特的反应性,为有机金属化学中的芳香性提供了新的见解.
科学领域:
- 有机金属化学 有机金属化学
- 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:
- 芳香性通常与顺服赫克尔规则的平面,循环系统有关.
- 四个成员的环通常是紧张的,不太容易产生芳香.
- 反应性中间体的稳定对于它们的研究至关重要.
研究的目的:
- 构建和表征新的中性,封闭外的芳香四个成员环系统.
- 调查体保护在隔离这些系统中的作用.
- 探索这些独特的有机金属化合物的反应性和电子特性.
主要方法:
- 在penttaaryl[60]fullerene中封装的cobaltacyclobutane复合物的合成.
- 进行X射线晶体分析以确定分子结构.
- 密度函数理论 (DFT) 计算以探测电子结构和芳香度.
主要成果:
- 成功地构建了-硫 (CoS3) 和- (CoSe3) 四个组成的环.
- X射线分析证实在富勒烯内有一个平面的COS3单元.
- DFT的计算表明,CoS3单元的6π电子芳香系统.
- 通过硫原子抽象证明了独特的反应性,导致二聚体的形成.
结论:
- 五甲基[60]富勒烯为隔离芳香 hetero cobaltacyclobutanes 提供了关键的固态保护.
- 这项研究扩大了对紧张的四个成员环系统中芳香度的理解.
- 这项工作推动了芳香有机金属化学领域的发展.
相关概念视频
01:18Aromatic Hydrocarbon Anions: Structural Overview
Neutral hydrocarbons like cyclopentadiene with an odd number of carbon atoms and one intervening CH2 group in the ring are not aromatic. Cyclopentadiene with 4 π electrons does not satisfy the 4n + 2 π electron rule. Additionally, the intervening CH2 group is sp3 hybridized and lacks a vacant p orbital, thereby interrupting the overlap of p orbitals in a continuous manner and preventing the delocalization of π electrons throughout the ring.
Due to the absence of continuous overlap of p...
Due to the absence of continuous overlap of p...
01:18Aromatic 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...
Removing one hydrogen from the intervening CH2 group with both...
01:18Frost Circles for Different Conjugated Systems
The inscribed polygon method is consistent with Hückel’s 4n + 2 rule and helps to learn whether the given cyclic compound is aromatic or not. The compound is stable and aromatic if every bonding molecular orbital (MO) is completely filled with a pair of electrons. However, if the non-bonding or antibonding orbitals are filled with electrons, the compound is unstable and not aromatic. Consider the Frost circle diagrams for cycloalkenes containing 4 to 8 carbons.
01:13Five-Membered Heterocyclic Aromatic Compounds: Overview
Heterocyclic aromatic compounds are cyclic compounds that are aromatic and have one or more heteroatoms—atoms other than carbon, in the ring. Depending upon the number of atoms present in the ring, they can be either five or six-membered. Examples of five-membered heterocyclic aromatic compounds include pyrrole, furan, thiophene, and imidazole. Pyrrole consists of one nitrogen atom having one lone pair of electrons. Furan and thiophene have one oxygen and one sulfur heteroatom, respectively.
01:20Criteria for Aromaticity and the Hückel 4n + 2 Rule
Like benzene, cyclobutadiene and cyclooctatetraene are cyclic compounds with alternate single and double bonds. However, their chemical behavior differs from benzene, as they are unstable and not aromatic. So, what are the structural characteristics of unsaturated compounds categorized as aromatic?
For the first time, Eric Hückel, a German chemical physicist, derived a set of structural features for a compound to be classified as aromatic. This is now known as Hückel’s rule or the 4n + 2 rule.
For the first time, Eric Hückel, a German chemical physicist, derived a set of structural features for a compound to be classified as aromatic. This is now known as Hückel’s rule or the 4n + 2 rule.
01:24π Molecular Orbitals of 1,3-Butadiene
Conjugated dienes have lower heats of hydrogenation than cumulated and isolated dienes, making them more stable. The enhanced stabilization of conjugated systems can be understood from their π molecular orbitals.
The simplest conjugated diene is 1,3-butadiene: a four-carbon system where each carbon is sp2-hybridized and has an unhybridized p orbital that contains an unpaired electron. According to molecular orbital theory, atomic orbitals combine to form molecular orbitals such that the number...
The simplest conjugated diene is 1,3-butadiene: a four-carbon system where each carbon is sp2-hybridized and has an unhybridized p orbital that contains an unpaired electron. According to molecular orbital theory, atomic orbitals combine to form molecular orbitals such that the number...