Video Experimental Relacionado
Updated: Jul 5, 2026
06:35
Construction and Systematical Symmetric Studies of a Series of Supramolecular Clusters with Binary or Ternary Ammonium Triphenylacetates
Published on: February 15, 2016
Las estructuras cristalinas y las polimerizaciones topoquímicas de 7,7,8,8-tetráquidos ((alcoxicarbonilo)
Shinji Nomura1, Takahito Itoh, Hirofumi Nakasho
1Department of Chemistry for Materials, Faculty of Engineering, Mie University, 1515 Kamihama-cho, Tsu-shi, Mie 514-8507, Japan.
Journal of the American Chemical Society
|February 20, 2004
Resumen
Los monómeros polimórficos de quinodimetano exhiben comportamientos de polimerización distintos en estado sólido, influenciados por el empaque de cristales. Esta investigación explora cómo el arreglo molecular afecta a los resultados de la polimerización topoquímica y térmica.
Área de la Ciencia:
- Ciencia de los materiales Ciencia de los materiales.
- Química de Polímeros La Química de Polímeros es la química de los polímeros.
- La cristalografía es una técnica de cristalografía.
Sus antecedentes:
- Se sintetizaron monómeros altamente conjugados, específicamente los 7,7,8,8-tetráquicos ((alcoxicarbonilo) quinodimetanos.
- El polimorfismo se observó en varios derivados sintetizados de quinodimetano, con diferentes formas cristalinas que exhiben distintos arreglos de empaque molecular.
Objetivo del estudio:
- Para investigar el comportamiento de polimerización en estado sólido de los monómeros polimórficos de quinodimetano.
- Para correlacionar los parámetros de empaque molecular con la reactividad de polimerización y la morfología del polímero (cristalino vs amorfo).
Principales métodos:
- Síntesis de una serie de monómeros de 7,7,8,8-tetráquidos ((alcoxicarbonilo) quinodimetano.
- Análisis de la estructura cristalina de rayos X para determinar los modos de empaque molecular e identificar las formas polimórficas.
- Experimentos de foto polimerización en estado sólido y de polimerización térmica.
- Análisis de los parámetros de embalaje de cristales, incluida la distancia de apilamiento, la distancia entre carbono y las orientaciones angulares.
Principales resultados:
- Las formas polimórficas específicas (1a-A, 1e-A, 1f-A) se sometieron a una fotopolimerización topoquímica para obtener polímeros cristalinos.
- La polimerización térmica se produjo tanto para las formas cristalinas (1a-A, 1e-A, 1f-A) como para ciertas formas amorfas (1e-B, 1f-B).
- Los polímeros derivados de precursores amorfos (1e-B, 1f-B) eran ellos mismos amorfos.
Conclusiones:
- La disposición de empaque molecular en los cristales de quinodimetano influye significativamente en su reactividad de polimerización en estado sólido y en la estructura del polímero resultante.
- Los parámetros clave de empaque (distancia de apilamiento, distancia entre carbono y ángulos de orientación) son cruciales para predecir los resultados de la polimerización.
Videos de Conceptos Relacionados
02:42Ionic Crystal Structures
Ionic crystals consist of two or more different kinds of ions that usually have different sizes. The packing of these ions into a crystal structure is more complex than the packing of metal atoms that are the same size.
Most monatomic ions behave as charged spheres, and their attraction for ions of opposite charge is the same in every direction. Consequently, stable structures for ionic compounds result (1) when ions of one charge are surrounded by as many ions as possible of the opposite...
Most monatomic ions behave as charged spheres, and their attraction for ions of opposite charge is the same in every direction. Consequently, stable structures for ionic compounds result (1) when ions of one charge are surrounded by as many ions as possible of the opposite...
02:18Network Covalent Solids
Network covalent solids contain a three-dimensional network of covalently bonded atoms as found in the crystal structures of nonmetals like diamond, graphite, silicon, and some covalent compounds, such as silicon dioxide (sand) and silicon carbide (carborundum, the abrasive on sandpaper). Many minerals have networks of covalent bonds.
To break or to melt a covalent network solid, covalent bonds must be broken. Because covalent bonds are relatively strong, covalent network solids are typically...
To break or to melt a covalent network solid, covalent bonds must be broken. Because covalent bonds are relatively strong, covalent network solids are typically...
02:57Coordination Number and Geometry
For transition metal complexes, the coordination number determines the geometry around the central metal ion. Table 1 compares coordination numbers to molecular geometry. The most common structures of the complexes in coordination compounds are octahedral, tetrahedral, and square planar.
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,...