オルトフェニレン:異例の結合オリゴーマーで,効果的結合長が驚くほど長い
Jian He1, Jason L Crase, Shriya H Wadumethrige
1Department of Chemistry and Biochemistry, Miami University, Oxford, Ohio 45056, USA.
Journal of the American Chemical Society
|September 14, 2010
まとめ
研究者らは新しいオルトフェニレンオリゴーマーを合成し,予期せぬ長距離電子デロカライゼーションとユニークな形状偏好を明らかにし,結合分子構造を進歩させました.
科学分野:
- 有機化学 オーガニック・ケミストリー
- マテリアルサイエンス 材料科学
- 超分子化学 超分子化学
背景:
- オルトフェニレン (Ortho-phenylenes) は,結合した分子構造の基本的だが未熟なクラスである.
- それらの性質を理解することは,新しい機能的有機材料の開発の鍵です.
研究 の 目的:
- 単分散オルトフェニレンオリゴマーの強力な合成経路を開発する.
- これらのオリゴマーの構成的行動,電子的移位,および光物理的性質を調査する.
主な方法:
- オルトフェニレンオリゴマーのホモログ系を12カメールまで合成する.
- 電子デロカライゼーションを評価するために,UV/Visスペクトロスコピーを用いた特徴付け.
- 適合分析と密度関数理論 (DFT) の計算.
主要な成果:
- 単分散オルトフェニレンオリゴマーの合成に成功しました.
- 偏った2倍対称な形状の観察,おそらく積み重ねられたヘリックスです.
- 遠距離電子デロカライゼーションの証拠は,約8つの繰り返しユニットの有効な結合長さがあります.
- オリゴーマー長さの増加に伴い,光スペクトルの異常なヒプソクロミックシフト.
結論:
- 開発された合成アプローチにより,明確に定義されたオルトフェニレンオリゴーマーにアクセスできます.
- オルトフェニレンには独特の形状の好みがあり,長距離の電子移位が顕著である.
- 観測されたスペクトルシフトは,この新しい結合材料のクラスにおける構造-特性関係についての洞察を提供します.
関連する概念動画
01:27¹H NMR: Long-Range Coupling
The coupling interactions of nuclei across four or more bonds are usually weak, with J values less than 1 Hz. While these are usually not observed in spectra, the presence of multiple bonds along the coupling pathway can result in observable long-range coupling.
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene π orbitals.
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene π orbitals.
02:23Structure and Nomenclature of Alcohols and Phenols
Overview
Alcohols are one of the most important functional groups in organic chemistry. The name of alcohol comes from the hydrocarbon from which it is derived. Alcohols are organic molecules containing the functional hydroxyl or –OH group directly bonded to carbon. Phenols have an OH group directly attached to a benzene ring. While alcohols are colorless, phenol is a white crystalline compound with a characteristic "hospital smell" odor.
As with other organic compounds, alcohols and phenols...
Alcohols are one of the most important functional groups in organic chemistry. The name of alcohol comes from the hydrocarbon from which it is derived. Alcohols are organic molecules containing the functional hydroxyl or –OH group directly bonded to carbon. Phenols have an OH group directly attached to a benzene ring. While alcohols are colorless, phenol is a white crystalline compound with a characteristic "hospital smell" odor.
As with other organic compounds, alcohols and phenols...
01:16Structure of Conjugated Dienes
Introduction
Conjugated dienes are compounds characterized by the presence of alternating double and single bonds. In a conjugated system like 1,3-butadiene, the unhybridized 2p orbital on each carbon overlaps continuously, allowing the π electrons to be delocalized across the entire molecule. In contrast, this type of overlap does not occur in cumulated and isolated dienes, such as 2,3-pentadiene and 1,4-pentadiene, respectively. Instead, the π electrons remain localized between the double...
Conjugated dienes are compounds characterized by the presence of alternating double and single bonds. In a conjugated system like 1,3-butadiene, the unhybridized 2p orbital on each carbon overlaps continuously, allowing the π electrons to be delocalized across the entire molecule. In contrast, this type of overlap does not occur in cumulated and isolated dienes, such as 2,3-pentadiene and 1,4-pentadiene, respectively. Instead, the π electrons remain localized between the double...
01:00Characteristics and Nomenclature of Homopolymers
Polymers that are made up of identical monomer units are called homopolymers. Only one repeating unit is involved in the construction of the homopolymer structure. For example, as depicted in Figure 1, polypropylene is a homopolymer constituted of propylene monomers. Here, the only repeating unit in the polymer chain is propylene.
02:35Free-Radical Chain Reaction and Polymerization of Alkenes
The conversion of alkenes to macromolecules called polymers is a reaction of high commercial importance. The structure of the polymer is defined by a repeating unit, while the terminal groups are considered insignificant. The average degree of polymerization represents the number of repeating units in the polymer molecule and is denoted by the subscript n.
01:16Olefin Metathesis Polymerization: Ring-Opening Metathesis Polymerization (ROMP)
Ring-opening metathesis polymerization or ROMP involves strained cycloalkenes as starting materials. The mechanism of ROMP proceeds by reacting cycloalkene with Grubbs catalyst to give metallacyclobutane intermediate which undergoes a ring-opening reaction to form new carbene. The new carbene reacts with another molecule of cycloalkene. Repetition of these steps leads to the formation of an unsaturated open-chain polymer product. All these steps are reversible, however, relieving the ring...