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01:20¹³C NMR: Distortionless Enhancement by Polarization Transfer (DEPT)
When proton-coupled carbon-13 spectra are simplified by a broadband proton decoupling technique, structural information about the coupled protons is lost. Distortionless enhancement by polarization transfer (DEPT) is a technique that provides information on the number of hydrogens attached to each carbon in a molecule. While the DEPT experiment utilizes complex pulse sequences, the pulse delay and flip angle are specifically manipulated. The resulting signals have different phases depending on...
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
01:04Structures of Aldehydes and Ketones
Vanillin—a flavoring agent in vanilla, cinnamaldehyde—a molecule responsible for the distinct smell of cinnamon, and acetone—a strong-smelling ingredient in nail polish removers, all belong to a class of carbonyl compounds called aldehydes and ketones (Figure 1). Although both aldehydes and ketones contain the characteristic carbonyl (C=O) bond, their chemical structures vary with respect to the groups directly attached to the carbonyl carbon.
In aldehydes (Figures 1a and 1b), the carbonyl...
In aldehydes (Figures 1a and 1b), the carbonyl...
01:30The Electrical Double Layer
In the region where two bulk phases meet, an intricate electric charge distribution arises due to charge transfer, ion adsorption, molecular orientation, and charge distortion. This complex distribution is commonly referred to as the electrical double layer.When a solid electrode interfaces with ions in an electrolyte solution, the speed of electron transfer dictates the rates of oxidation and reduction. The electrode acquires a charge through the escape of atoms into the solution as cations or...
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Perileno bisimida retorcido en forma de Z en forma de Z.
Faysal Ilhan1, Daniel S Tyson, Daniel J Stasko
1Polymers Branch, Materials and Structures Division, NASA Glenn Research Center, 21000 Brookpark Road, Cleveland, Ohio 44135, USA.
Journal of the American Chemical Society
|January 19, 2006
Resumen
Se sintetizó y caracterizó un nuevo cromóforo de perileno bisimida en forma de Z. Esta nueva molécula exhibe una fuerte fluorescencia y potencial para aplicaciones en estado sólido debido a la formación de exciplex.
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Área de la Ciencia:
- Química orgánica es la química orgánica.
- Ciencia de los materiales Ciencia de los materiales.
- La fotofísica es la fotofísica.
Sus antecedentes:
- Los perileno bisimidas son una clase crucial de tintes orgánicos.
- El desarrollo de nuevos cromóforos con propiedades a medida es esencial para aplicaciones avanzadas.
Objetivo del estudio:
- Para sintetizar un nuevo derivado de perileno bisimida en forma de Z.
- Para investigar sus propiedades fotofísicas y electroquímicas.
- Explorar su potencial en aplicaciones de estado sólido.
Principales métodos:
- Síntesis vía fotoenolización y reacción de Diels-Alder.
- Caracterización utilizando la absorción UV-Vis y la espectroscopia de fluorescencia.
- Análisis electroquímico y cristalografía de rayos X.
Principales resultados:
- Se ha logrado la síntesis de N,N'-bis(octil)-3,9-bis(fenil)perileno-1,2,7,8-tetracarboxil bisimida (1).
- Datos espectroscópicos en diclorometano: absorción máxima a 491 nm, fluorescencia máxima a 517 nm, alto rendimiento cuántico (0,70) y tiempo de vida de la fluorescencia (5,01 ns).
- Se observó una emisión roja en estado sólido, lo que indica la formación de exciplex; el análisis de rayos X reveló un núcleo de perileno retorcido.
Conclusiones:
- El nuevo perileno bisimida en forma de Z exhibe excelentes propiedades fotofísicas.
- La formación de exciplex en estado sólido sugiere el potencial de los dispositivos optoelectrónicos.
- La estructura del núcleo retorcido influye en las propiedades observadas.