線形反応法によるエクシトン吸収スペクトル:結合ポリマーへの適用
Martín A Mosquera1, Nicholas E Jackson1,2, Thomas J Fauvell1
1Department of Chemistry and the Materials Research Center, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.
Journal of the American Chemical Society
|February 23, 2017
まとめ
この研究は,結合されたポリマーにおけるエクシトンスペクトルを計算するための効率的な2段階の方法を示しています. この新しいアプローチは,近赤外線の吸収を正確に予測し,材料の性質を理解し,将来のスペクトロスコピーの発展を導くのに役立ちます.
科学分野:
- コンピュータ化学
- スペクトロスコーピー
- 材料科学
背景:
- エクシトンスペクトルの計算は,材料の興奮状態のダイナミクスを理解するために重要です.
- 従来の方法は,一般的な密度関数を使用する計算コストと精度の問題に直面します.
- 以前の作業では,これらの制限に対処するために2段階の計算を導入しました.
研究 の 目的:
- エクシトンの近赤外線吸収スペクトルを計算するための新しい2段階の理論的方法を適用する.
- ポリ3-ヘキシルチオフェン (P3HT),ポリ2-メトキシ-5-2-エチルヘキシロシ) -1,4-フェニレンビニレン (MEH-PPV),およびポリ-ベンゾジチオフェン-チエノ[3,4-b]チオフェン (PTB7) のオリゴマーのエクシトン行動を調査する.
- 主要な軌道刺激を特定し,最長波長の吸収ピークを予測するためのルールを確立する.
主な方法:
- 2つの線形応答時間依存密度関数理論 (TDDFT) の2つのステップを含む2段階の計算.
- 最初の TDDFT ステップは,エクシトン状態によって混乱した軌道を生成します.
- TDDFTの第2段階は,興奮状態に対する興奮スペクトルを計算します.
主要な成果:
- P3HTとMEH-PPVのオリゴマーの計算されたスペクトルは,実験データと一致する10のモノマー単位で収束を示しています.
- MEH-PPVにおけるエキシトンスペクトルの特徴は,バイポラロン形成と重複することが判明した.
- PTB7 オリゴマーのエクシトンの吸収帯は,一時的な吸収スペクトルで特定されました.
- すべての研究されたポリマーについて,光学的に活発な移行に寄与する支配的軌道刺激が報告されました.
結論:
- 開発された方法論は,結合されたポリマーの近赤外線吸収スペクトルを正確に予測します.
- この発見は,エクシトン-バイポラロン相互作用の洞察を提供し,実験的な一時的な吸収スペクトルを検証します.
- この方法は,非アディアバティック効果と電荷移転状態を含む,高度な理論的トランジントスペクトロスコーピーの基礎を提供します.
関連する概念動画
UV–Vis Spectroscopy of Conjugated Systems
8.7K
Organic compounds with conjugated double bonds show strong absorption features in the UV–visible region of the electromagnetic spectrum attributed to π → π* electronic excitations. Generally, a UV–vis absorption spectrum is recorded as a plot of absorbance vs wavelength. The wavelength of maximum absorbance, which manifests as a peak in the absorption spectrum, is denoted as λmax.
One of the factors influencing λmax is the extent of conjugation in...
One of the factors influencing λmax is the extent of conjugation in...
8.7K
Photochemical Electrocyclic Reactions: Stereochemistry
2.3K
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
2.3K
Molecular Spectroscopy: Absorption and Emission
5.1K
Molecules possess discrete energy levels called quantum states. Unlike atoms, which have simpler energy levels, molecules possess additional rotational and vibrational energy levels. Each energy level is separated by an energy gap, with the gaps between adjacent electronic, vibrational, and rotational levels varying significantly. The three types of energy levels in a diatomic molecule are shown in Figure 1.
5.1K
UV–Vis Spectrum
3.1K
When light passes through a substance, a portion of the light is absorbed while the remaining light is reflected or transmitted. If the molecule absorbs light between the wavelengths of 180–400 nm range, the UV spectrum is obtained, and if it absorbs light in the 400–780 nm wavelength range, the visible spectrum is obtained.
The UV–Vis spectrum of a molecule is the plot of its absorbance versus wavelength. The plot is drawn by taking molar...
The UV–Vis spectrum of a molecule is the plot of its absorbance versus wavelength. The plot is drawn by taking molar...
3.1K
UV–Vis Spectroscopy: Molecular Electronic Transitions
3.3K
In Ultraviolet–Visible (UV–Vis) spectroscopy, the absorption of electromagnetic radiation is used to probe the electronic structure of molecules. This technique provides insights into molecular electronic transitions, particularly the movement of electrons between different molecular orbitals. Radiation is absorbed if the energy of the electromagnetic radiation passing through the molecule is precisely equal to the energy difference between the excited and ground states. During this...
3.3K
Spectrophotometry: Introduction
10.8K
Spectrophotometry is the quantitative measurement of the absorption, reflection, diffraction, or transmission of electromagnetic radiation through a material as a function of the intensity and wavelength of the radiation. A spectrophotometer is a device used to measure the change in the radiation intensity caused by its interaction with the material.
The essential components of a spectrophotometer include a source of electromagnetic radiation, a slot for placing a material to be analyzed, and a...
The essential components of a spectrophotometer include a source of electromagnetic radiation, a slot for placing a material to be analyzed, and a...
10.8K


