Video Experimental Relacionado
Updated: Jul 29, 2026
07:13
High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia (YSZ) Scaffolds by In Situ Carbon Templating Xerogels
Published on: April 16, 2017
Solución frente a la estructura en estado sólido de los catalizadores heterobimetálicos de ytterbio
Lorenzo Di Bari1, Moreno Lelli, Guido Pintacuda
1ICCOM-CNR, Sez. di Pisa, Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, I-56126 Pisa, Italy.
Journal of the American Chemical Society
|May 2, 2003
Resumen
Este estudio revela las estructuras de solución de complejos heterobimetálicos de ytterbio, encontrando que comparten geometrías similares pero difieren en propiedades magnéticas. El dicroísmo circular casi infrarrojo resulta sensible a los cambios en la esfera de coordinación del iterbio.
Área de la Ciencia:
- Química organometálica Química orgánica de los metales.
- La catálisis es la catálisis.
- La espectroscopia es una técnica de espectroscopia.
Sus antecedentes:
- Los complejos heterobimetálicos de yterbio, incluidos los complejos Na(3) [Yb(((S) -BINOL) ((3) ], K(3) [Yb((S) -BINOL) ((3) ] y Li(3) [Yb((S) -BINOL) ((3) ], son catalizadores enantioselectivos reconocidos.
- Comprender sus estructuras de solución es crucial para optimizar el rendimiento catalítico.
Objetivo del estudio:
- Para dilucidar las estructuras de solución de complejos heterobimetálicos de ytterbio.
- Investigar la dinámica estructural tras la disolución de los estados cristalinos.
- Evaluar la sensibilidad de las técnicas espectroscópicas a los cambios de la esfera de coordinación.
Principales métodos:
- Espectroscopia de Resonancia Magnética Nuclear (RMN), incluidos los desplazamientos paramagnéticos.
- Espectroscopia de dicroísmo circular (CD) UV e infrarrojo cercano (NIR). espectroscopía de dicroísmo circular (CD). espectroscopía de dichroísmo circular (CD). espectroscopía de dichroísmo circular (CD). espectroscopía de dichroísmo circular (CD). espectroscopía de dichroísmo circular (CD). espectroscopía de dichroísmo circular (CD).
- Difracción de rayos X (XRD) para la comparación de la estructura cristalina.
- Espectroscopia de intercambio (EXSY) para estudiar la labilidad de los bonos.
Principales resultados:
- Los complejos 1, 2 y 3 exhiben geometrías de solución idénticas pero con distintos factores de susceptibilidad magnética (D).
- Se observó una reorganización estructural de la simetría cristalina C(3) a la simetría de la solución D(3) para el complejo 1 tras la disolución.
- Los enlaces de yterbio-oxígeno con el agua no se detectaron en la solución, y los enlaces de Ln-BINOL demostraron labilidad.
- La espectroscopia NIR-CD es muy sensible a las alteraciones en el entorno de coordinación del iterbio.
Conclusiones:
- Las estructuras de solución de estos complejos de iterbio se conservan en diferentes continentes (Na+, K+, Li+).
- La disolución induce un cambio de simetría de los estados cristalinos a los disueltos.
- La labilidad de los enlaces Ln-BINOL y la ausencia de coordinación del agua son características clave del estado de solución.
- NIR-CD es una herramienta poderosa para sondear la esfera de coordinación de iterbio en estos sistemas catalíticos.
Videos de Conceptos Relacionados
02:50Catalysis
The presence of a catalyst affects the rate of a chemical reaction. A catalyst is a substance that can increase the reaction rate without being consumed during the process. A basic comprehension of a catalysts’ role during chemical reactions can be understood from the concept of reaction mechanisms and energy diagrams.
02:34Structural Isomerism
Isomerism in Complexes
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can be...
Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can be...
02:42Valence Bond Theory
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
Tetrahedral Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
01:27Catalysis
Catalysis influences the rate of chemical reactions by providing an alternative reaction pathway with lower activation energy. A catalyst speeds up a reaction, but it is not consumed during the process. The fundamental principle of catalysis is the ability of a catalyst to alter the reaction mechanism, often introducing a more efficient pathway than the uncatalyzed process.In a catalyzed reaction, the catalyst participates directly in the reaction mechanism. It interacts with reactants to form...
01:22Heterogeneous Catalysis
Heterogeneous catalysis involves a catalyst in a different phase from the reactants. It is a process where the catalyst and the reactants are in distinct phases, typically solid and gas or liquid.Most heterogeneous catalysts are metals, metal oxides, or acids. The list includes transition metals like iron (Fe), cobalt (Co), nickel (Ni), palladium (Pd), platinum (Pt), chromium (Cr), manganese (Mn), tungsten (W), silver (Ag), and copper (Cu). These metals possess partially vacant d orbitals that...