Video Experimental Relacionado
Updated: Jul 15, 2026
09:42
Fabrication of a Dipole-assisted Solid Phase Extraction Microchip for Trace Metal Analysis in Water Samples
Published on: August 7, 2016
La estructura del catalizador de oxidación homogéneo, Mn{II}{Br}{-1}x, en agua supercrítica: un estudio de la
Yongsheng Chen1, John L Fulton, Walter Partenheimer
1Chemical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, USA.
Journal of the American Chemical Society
|October 6, 2005
Resumen
En el agua supercrítica, los catalizadores de bromuro de manganeso ((II) cambian de estructuras octaédricas a tetraédricas, formando pares de iones de contacto Mn-Br cruciales para la síntesis del ácido tereftálico.
Área de la Ciencia:
- Química Inorgánica La Química Inorgánica es la química inorgánica.
- Ciencia de los materiales Ciencia de los materiales.
- La catálisis de la catálisis.
Sus antecedentes:
- El bromuro de manganeso (MnBr2) en agua supercrítica cataliza eficazmente la síntesis oxidativa aeróbica del ácido tereftálico.
- Comprender la estructura de coordinación de los iones Mn (II) y Br (-1) es clave para explicar esta actividad catalítica.
Objetivo del estudio:
- Para dilucidar la estructura de coordinación de la primera capa de los iones Mn (II) y Br (-1) en agua supercrítica.
- Para aclarar la base estructural del papel catalítico de MnBr2 en la oxidación de compuestos metilaromáticos.
Principales métodos:
- Utilizó espectroscopias de estructura fina de absorción de rayos X extendida (EXAFS) y de absorción de rayos X cerca de la estructura de borde (XANES).
- Se han recogido espectros de borde Mn y Br K en la Fuente Avanzada de Fotones del Laboratorio Nacional Argonne.
Principales resultados:
- La coordinación cambia de octaédrico (ambiente) a tetraédrico (condiciones supercríticas).
- En el agua supercrítica, las distancias de enlace Mn-OH2 y Mn-Br son 2,14 Å y 2,46 Å, respectivamente.
- El MnBr2 disuelto se transforma de [Mn(II) ((H2O) 6+2 a [Mn(II) ((H2O) 2 ((Br (-1)) 2), formando pares de iones de contacto Mn-Br.
Conclusiones:
- El catalizador activo de MnBr2 en agua supercrítica exhibe una estructura tetraédrica con dos pares de iones de contacto Mn-Br.
- El exceso de iones de bromuro aumenta la coordinación del bromuro y disminuye los ligandos de agua.
- Los aniones de acetato desactivan el catalizador formando óxido de manganeso insoluble (MnO).
Más Videos Relacionados
07:55Elemental-sensitive Detection of the Chemistry in Batteries through Soft X-ray Absorption Spectroscopy and Resonant Inelastic X-ray Scattering
Published on: April 17, 2018
09:02Manganese Oxide Nanoparticle Synthesis by Thermal Decomposition of Manganese(II) Acetylacetonate
Published on: June 18, 2020
Videos de Conceptos Relacionados
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...
02:58Crystal Field Theory - Octahedral Complexes
Crystal Field Theory
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
03:02Colors and Magnetism
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 eye.
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 eye.
01:13¹H NMR: Complex Splitting
A proton M that is coupled to a proton X results in doublet signals for M. However, NMR-active nuclei can be simultaneously coupled to more than one nonequivalent nucleus. When M is coupled to a second proton A, such as in styrene oxide, each peak in the doublet is split into another doublet.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.
01:29Determination of Crystal Structures
In the late 1800s, the revelation that light extended beyond visible wavelengths led to the discovery of X-rays by Wilhelm Roentgen. Recognized as high-energy electromagnetic radiation with short wavelengths, X-rays prompted exploration into their interaction with crystals. Max von Laue proposed in 1912 that the periodic arrangement of atoms, ions, or molecules in crystals would cause them to diffract X-rays, a hypothesis confirmed through experiments with copper sulfate and zinc sulfide...