Video Experimental Relacionado
Updated: Jul 20, 2026
13:09
Utilization of Stop-flow Micro-tubing Reactors for the Development of Organic Transformations
Published on: January 4, 2018
La fotociclización eficiente del diímero, trímero y tetrámero de dietienileteno: rendimiento cuántico y dinámica de
Teruaki Kaieda1, Seiya Kobatake, Hiroshi Miyasaka
1Department of Chemistry and Biochemistry, Graduate School of Engineering, Kyushu University, and CREST, Japan Science and Technology Corporation, Higashi-ku, Fukuoka 812-8581, Japan.
Journal of the American Chemical Society
|February 28, 2002
Resumen
Las matrices sintetizadas de multi-dietienileteno exhiben cambios de color reversibles tras la irradiación UV/luz visible. El aumento de las unidades de dietienileteno mejora el rendimiento cuántico de la fotociclado debido a una migración de energía eficiente.
Área de la Ciencia:
- Química orgánica es la química orgánica.
- La fotoquímica es la fotoquímica.
- Ciencia de los materiales Ciencia de los materiales.
Sus antecedentes:
- Los compuestos de ditilenileto (DTE) son conocidos por sus propiedades fotocrómicas.
- El fotocromismo implica cambios de color reversibles inducidos por la luz.
- El ajuste de las propiedades DTE es crucial para el desarrollo de materiales ópticos avanzados.
Objetivo del estudio:
- Para sintetizar y caracterizar las matrices de multi-dietienileteno.
- Para investigar el efecto de la longitud de la matriz en el rendimiento cuántico de fotociclismo.
- Para dilucidar el mecanismo detrás del rendimiento fotocrómico mejorado.
Principales métodos:
- Síntesis de matrices multi-dietienileteno puenteadas con etiinile (dimeros, trímeros, tetrámeros).
- Evaluación del rendimiento fotocrómico bajo la irradiación UV y luz visible.
- Determinación del rendimiento cuántico para reacciones de fotociclado.
- Estudios de fotólisis láser de picosegundos y despolarización por fluorescencia.
Principales resultados:
- Las matrices sintetizadas mostraron un cambio de color violeta-azul reversible tras la irradiación UV, desapareciendo con la luz visible.
- Los rendimientos cuánticos para la fotociclización aumentaron de 0,21 a 0,40 con el aumento de las unidades de DTE (1 a 4).
- Se observó evidencia de una eficiente migración de energía excitada de los conformadores paralelos a los antiparalelas.
Conclusiones:
- Las matrices de multi-dietienileteno ofrecen propiedades fotocrómicas sintonizables.
- El aumento de la conjugación y la migración de energía mejoran la eficiencia de la fotociclización en estas matrices.
- Estos hallazgos contribuyen al diseño de nuevos materiales fotorreactivos.
Videos de Conceptos Relacionados
01:26Thermal 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.
01:17Thermal 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.
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.
01:26Photochemical 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
Selection Rules: Photochemical Activation
![[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2Ffiles%2Fmedia%2Fscience-education%2Fscience-education-thumbs%2F12417.jpg&w=3840&q=75)
01:16[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
The Diels–Alder reaction is an example of a thermal pericyclic reaction between a conjugated diene and an alkene or alkyne, commonly referred to as a dienophile. The reaction involves a concerted movement of six π electrons, four from the diene and two from the dienophile, forming an unsaturated six-membered ring. As a result, these reactions are classified as [4+2] cycloadditions.
01:28Diels–Alder Reaction Forming Cyclic Products: Stereochemistry
The Diels–Alder reaction is one of the robust methods for synthesizing unsaturated six-membered rings. The reaction involves a concerted cyclic movement of six π electrons: four π electrons from the diene and two π electrons from the dienophile.
01:17Pericyclic 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...
Pericyclic reactions can be classified into three categories: electrocyclic reactions, cycloaddition reactions, and sigmatropic rearrangements. Electrocyclic reactions and sigmatropic rearrangements are...