Video Experimental Relacionado
Updated: Mar 27, 2026
10:44
Isolating Free Carbenes, their Mixed Dimers and Organic Radicals
Published on: April 19, 2019
11.8K
Control de la luz y la temperatura del estado de espín del bis (p-metoxifenil) carbeno: un carbeno magnéticamente
Paolo Costa1, Thomas Lohmiller1,2, Iris Trosien1
1Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum , 44780 Bochum, Germany.
Journal of the American Chemical Society
|January 16, 2016
Resumen
El bis ((p-metoxifenil) carbeno es el primer carbeno aislado en los estados singlete y triplete a 3 K. La luz controla el carbeno
Área de la Ciencia:
- Química orgánica
- La fotoquímica
- Espectroscopia
Sus antecedentes:
- Los carbenos son productos intermedios altamente reactivos que son cruciales en la síntesis orgánica.
- Comprender los estados de espín de los carbenos (singlet y triplet) es clave para controlar su reactividad.
- El aislamiento de carbenos en estados de espín específicos a bajas temperaturas presenta un desafío significativo.
Objetivo del estudio:
- Investigar el aislamiento y la interconversión de los estados singlet y triplet de bis (p-metoxifenil) carbeno a temperaturas criogénicas.
- Para explorar la influencia de la irradiación de luz y la temperatura en el estado de espín del carbeno.
- Evaluar las aplicaciones potenciales de los estados de espín de carbenos controlados por la luz.
Principales métodos:
- Aislamiento del bis ((p-metoxifenil) carbeno en matrices de argón y vidrios MTHF a 3 K.
- Caracterización espectroscópica mediante IR, UV-vis, EPR de banda X, EPR de banda W y ENDOR de banda Q.
- Manipulación fotoquímica mediante luz UV (365 nm) y luz visible (450 nm) y recocido térmico.
Principales resultados:
- El bis ((p-metoxifenil) carbeno se aisló con éxito tanto en su estado singular como en su estado triple, coexistiendo indefinidamente a 3 K.
- La irradiación UV favoreció el estado triplet, mientras que la luz visible promovió el estado singlet.
- El recocido térmico convirtió el triplet en el estado singlet, un proceso irreversible al enfriarse.
Conclusiones:
- El estado de espín del bis ((p-metoxifenil) carbeno puede ser controlado selectivamente por la longitud de onda de la luz y la temperatura de la matriz.
- Este control inducido por la luz sobre los estados de espín del carbeno ofrece potencial para aplicaciones en el almacenamiento de información y la polimerización.
- Los hallazgos demuestran un nuevo método para manipular intermedios reactivos para aplicaciones de materiales avanzados.
Videos de Conceptos Relacionados
01:08Spin–Spin Coupling Constant: Overview
1.6K
In bromoethane, the three methyl protons are coupled to the two methylene protons that are three bonds away. In accordance with the n+1 rule, the signal from the methyl protons is split into three peaks with 1:2:1 relative intensities. The methylene protons appear as a quartet, with the relative intensities of 1:3:3:1.
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must...
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must...
1.6K
01:12Cycloaddition Reactions: MO Requirements for Photochemical Activation
2.9K
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.
2.9K
03:02Colors and Magnetism
14.6K
Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human...
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human...
14.6K
01:26Photochemical Electrocyclic Reactions: Stereochemistry
2.4K
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
2.4K
01:17Thermal Electrocyclic Reactions: Stereochemistry
2.7K
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.
2.7K
01:26Thermal and Photochemical Electrocyclic Reactions: Overview
3.2K
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.
3.2K