大量の芳香炭化水素コアを持つディスク材料の光学および電荷輸送特性
Michael G Debije1, Jorge Piris, Matthijs P de Haas
1Radiation Chemistry Department, IRI, Delft University of Technology, Mekelweg 15, 2629 JB Delft, The Netherlands.
Journal of the American Chemical Society
|April 9, 2004
まとめ
この研究では,異なる多環芳香核サイズを持つディスク分子における電荷輸送を調査した. 高い1次元の電荷の移動性は観察されましたが,それは以前に仮定されたように,コアサイズとともに増加することはありませんでした.
科学分野:
- マテリアルサイエンス 材料科学
- オーガニック・エレクトロニクス
- 物理化学 物理化学
背景:
- ディスコティック分子は,自己組み立てにより一次元柱に構成されるため,有機電子機器にとって有望である.
- これらの材料における電荷輸送の理解は,デバイスの性能にとって極めて重要です.
研究 の 目的:
- 異なる多循環性芳香核の大きさのディスク性分子の光学吸収と電荷輸送特性を調査する.
- 核のサイズが1次元の柱内電荷の移動性に与える影響を判定する.
主な方法:
- サイズのn=24,42,60,78,96,132の炭素原子を持つポリサイクルアロマティックコアを持つディスク分子合成.
- 稀溶液と薄膜での光学吸収スペクトロスコーピー.
- パルス放射解析の時間解像度マイクロ波伝導技術で,一次元のコラム内電荷移動性を測定する (Σμ1D).
主要な成果:
- 吸収最大値 (λmax) は,コアサイズ (n) に沿って線形的に増加し,λmax = 280 + 2n となる.
- 結晶固体における一次元の電荷移動性 (Σμ1D) は,0.41.0 cm2/Vs.の範囲であった.
- ディスコティック・メソフェーズでは,Σμ1Dは0.080.38cm2/Vsの範囲で,結晶固体よりも低い.
- 観測された移動性は,ディスコティックトリフェニレン誘導体について以前に報告されたよりも高かった.
結論:
- この研究は,大きな多循環性アロマティックコアを持つディスク分子における高電荷移動性を実証しています.
- 以前の仮説とは異なり,このシリーズでは,電荷の移動性は,コアサイズが増加する明確な増加傾向を示さなかった.
- これらの発見は,有機半導体設計の構造-特性関係に関する貴重な洞察を提供します.
関連する概念動画
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...
01:14π Electron Effects on Chemical Shift: Aromatic and Antiaromatic Compounds
In aromatic compounds, such as benzene, the circulation of (4n + 2) π-electrons sets up a diamagnetic or diatropic ring current around the perimeter of the molecule. This current induces a magnetic field that opposes the external field inside the ring and reinforces it on the outside. The protons in benzene are deshielded and exhibit high chemical shifts in the range 6.5–8.5 ppm. The shielding effect at the center of the ring is evident in complex aromatic molecules, such as annulenes. In...
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...
01:18Frost 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.
01:14NMR Spectroscopy of Aromatic Compounds
Aromatic compounds can be identified or analyzed using proton NMR and carbon‐13 NMR. Typically, aromatic hydrogens or hydrogens directly bonded to the aromatic rings are strongly deshielded by the aromatic ring current. Therefore, they absorb in the range of 6.5–8.0 ppm in proton NMR spectra. For instance, aromatic hydrogens directly bonded to the benzene ring absorb at 7.3 ppm. However, aromatic hydrogens of larger rings absorb farther upfield or downfield than the ideal range. Consider...
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