配列で定義された結合オリゴーマーにおける電荷輸送
Hao Yu1, Songsong Li2,3, Kenneth E Schwieter4
1Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States.
Journal of the American Chemical Society
|February 19, 2020
まとめ
合成ポリマーのモノメアの配列は,電荷輸送に大きな影響を及ぼします. 結合したオリゴマーの特定の配列は,ユニークな電荷経路を作り出すことで,分子伝導性を10倍以上高めます.
科学分野:
- ポリマー化学
- 材料科学
- 分子電子
背景:
- モノマー配列と物質特性の関係を理解することは,合成ポリマーにとって極めて重要です.
- 結合されたオリゴマーの電荷輸送は分子電子学の重要な要素である.
研究 の 目的:
- 単一分子の交差点における電荷輸送に,主モノマー配列がどのように影響するかを調査する.
- 配列で定義された結合オリゴーマーを合成し,特徴づけること.
主な方法:
- ヴァン・ルイスン反応を用いた繰り返し合成で,配列定義オリゴーマー (2〜7単位) を生成する.
- スキャニング・トンネル顕微鏡・ブレイク・ジャンクション (STM-BJ) 技術を用いて,電荷輸送特性の特徴づけ.
- 様々なオリゴーマー長さの分子伝導度を測定する.
主要な成果:
- 特定のモノマー配列は分子伝導性を10倍以上高めることが判明しました.
- イミダゾールまたはピロール群の配列定義ペンタマーは,複数の伝導経路を促進しました.
- ステリック阻害とヘテロサイクルの方向性は,負荷輸送において重要な役割を果たします.
結論:
- モノマー配列は,結合されたオリゴマーの電荷輸送を制御するための重要な設計パラメータです.
- 分子構造を調整することで 分子電子機器の性能が向上します
- この研究は,高度な分子電子部品を設計するための洞察を提供します.
関連する概念動画
00:57Cationic Chain-Growth Polymerization: Mechanism
2.7K
The cationic polymerization mechanism consists of three steps: initiation, propagation, and termination. In the initiation step of the polymerization process, the π bond of a monomer gets protonated by the Lewis acid catalyst, which is formed from boron trifluoride and water. The protonation of the π bond generates a carbocation stabilized by the electron‐donating group. In the propagation step, the π bond of the second monomer acts as a nucleophile and attacks the...
2.7K
01:04Anionic Chain-Growth Polymerization: Mechanism
2.4K
The mechanism for anionic chain-growth polymerization involves initiation, propagation, and termination steps. In the initiation step, a nucleophilic anion, such as butyl lithium, initiates the polymerization process by attacking the π bond of the vinylic monomer. As a result, a carbanion, stabilized by the electron‐withdrawing group, is generated. The resulting carbanion acts as a Michael donor in the propagation step and attacks the second vinylic monomer, which acts as a Michael...
2.4K
01:26Photochemical Electrocyclic Reactions: Stereochemistry
2.1K
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
2.1K
01:26Thermal 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
01:16Structure of Conjugated Dienes
6.6K
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...
6.6K
01:20Anionic Chain-Growth Polymerization: Overview
2.5K
The polymerization process that involves carbanion as an intermediate is called anionic polymerization. It is also a type of addition or chain-growth polymerization. Anionic polymerization gets initiated by a strong nucleophile such as an organolithium or a Grignard reagent. The most commonly used initiator for anionic polymerization is butyl lithium. Monomers involved in anionic polymerization must possess a vinyl group bonded to one or two electron-withdrawing groups. For instance,...
2.5K