関連する実験動画

Updated: Jul 14, 2026

Novel Techniques for Observing Structural Dynamics of Photoresponsive Liquid Crystals

Novel Techniques for Observing Structural Dynamics of Photoresponsive Liquid Crystals

Published on: May 29, 2018

光誘発の環状環の開閉を比較する:興奮状態経路の違い

Björn Heinz¹, Stephan Malkmus, Stefan Laimgruber

¹Department für Physik - Munich Center for Integrated Protein Science, Ludwig-Maximilians-Universität, Oettingenstrasse 67, D-80538 München, Germany.

Journal of the American Chemical Society

|June 15, 2007

まとめ

フルジミドの光色化は,開いた (E) と閉じた (C) の同位体間の切り替えを含みます. 超高速スペクトロスコピーは,EからCのサイクリングとCからEのサイクロレバーションの異なる興奮状態経路を明らかにし,単純な予測に挑戦しています.

科学分野:

フォトケミストリーフォトケミストリー
分子ダイナミクス分子ダイナミクス
オーガニック・ケミストリーオーガニック・ケミストリー

背景:

フルギミドは,光に曝露したときに逆行可能な色変化であるフォトクロミズムを発現します.
この現象は,オープン環 (E) と閉環 (C) の同位体間の相互変換に起因する.
ウッドワード・ホフマン法則は,これらの同位体間の光化学的相互変換を予測する.

研究の目的:

フルジミド光色素化の超高速ダイナミクスを調査する.
E --> Cサイクル化とC --> Eサイクル逆転の興奮状態経路を解明する.
実験結果と理論的予測を比較する.

主な方法:

フェムト秒の光スペクトロスコピー
暫定吸収スペクトロスコピーは,一時的な吸収スペクトロスコピーを用います.
時間解像度測定による測定

主要な成果:

E --> CとC --> E反応の両方の0.1-1psのタイムスケールで観察された二相光衰退.
2つの反応方向の異なる時間常数とスペクトルシグネチャー (例えば,E --> C に対して0.06と0.4ps,C --> E に対して0.09と2.4ps).
より長い崩壊時間定数は,光産物形成時間と相関する.

結論:

E --> Cサイクル化とC --> Eサイクル逆転の興奮状態経路は一般的ではない.
実験結果は,フルジミド光色化に関するウッドワード・ホフマン法則の単純な解釈と矛盾しています.
この発見は,フルジミドの興奮状態トポロジーに関する最近の量子力学計算を裏付けている.

さらに関連する動画

Photogeneration of N-Heterocyclic Carbenes: Application in Photoinduced Ring-Opening Metathesis Polymerization

Photogeneration of N-Heterocyclic Carbenes: Application in Photoinduced Ring-Opening Metathesis Polymerization

Published on: November 29, 2018

Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach

Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach

Published on: June 10, 2021

関連する概念動画

Photochemical Electrocyclic Reactions: Stereochemistry

Photochemical Electrocyclic Reactions: Stereochemistry

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

Thermal and Photochemical Electrocyclic Reactions: Overview

Thermal and Photochemical Electrocyclic Reactions: Overview

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.

Thermal Electrocyclic Reactions: Stereochemistry

Thermal Electrocyclic Reactions: Stereochemistry

The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.

Pericyclic Reactions: Introduction

Pericyclic Reactions: Introduction

Pericyclic reactions are organic reactions that occur via a concerted mechanism without generating any intermediates. The reactions proceed through the movement of electrons in a closed loop to form a cyclic transition state, where rearrangement of the σ and π bonds yields specific products.
Pericyclic reactions can be classified into three categories: electrocyclic reactions, cycloaddition reactions, and sigmatropic rearrangements. Electrocyclic reactions and sigmatropic rearrangements are...

Cycloaddition Reactions: MO Requirements for Photochemical Activation

Cycloaddition Reactions: MO Requirements for Photochemical Activation

Some cycloaddition reactions are activated by heat, while others are initiated by light. For example, a [2 + 2] cycloaddition between two ethylene molecules occurs only in the presence of light. It is photochemically allowed but thermally forbidden.

Base-Catalyzed Ring-Opening of Epoxides

Base-Catalyzed Ring-Opening of Epoxides

Due to their highly strained structures, epoxides can readily undergo ring-opening reactions through nucleophilic substitution, either in the presence of an acid or a base. The nucleophilic substitution reactions in the presence of acid are called acid-catalyzed ring-opening reactions, and nucleophilic substitution reactions in the presence of a base are called base-catalyzed ring-opening reactions. Epoxides undergo base-catalyzed ring-opening reactions in the presence of a strong nucleophile...