7,7,8,8-テトラキス ((アルコキシカルボニル)) キノジメタン の結晶構造とトポケミカルポリメリゼーション
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
まとめ
ポリモルフなキノディメタンモノマーは,結晶パッキングの影響で固体状態で異なったポリメリゼーション行動を示します. この研究は,分子配列がトポケミカルおよび熱ポリメリゼーションの結果にどのように影響するか探求しています.
科学分野:
- マテリアルサイエンス 材料科学
- ポリマー化学のポリマー化学について
- クリスタルグラフィーです.
背景:
- 高度に結合したモノマー,特に7,7,8,8-テトラキス (alkoxycarbonyl) キノディメタンが合成されました.
- 多形性は,いくつかの合成キノディメタン誘導体で観察され,異なる結晶形は,異なる分子包装配列を示しています.
研究 の 目的:
- ポリモルフなキノジメタンモノメアの固体状態ポリメリゼーション行動を調査する.
- 分子包装のパラメータをポリメリゼーション反応性とポリマー形態学 (結晶型と無形型) と相関させる.
主な方法:
- 7,7,8,8-テトラキス ((アルコキシカルボニル) キノディメタン単体の一連の合成.
- X線結晶構造分析により,分子包装の形態を決定し,多形形状を特定する.
- 固体光ポリメリゼーションと熱ポリメリゼーションの実験.
- スタッキング距離,炭素間距離,角方向など,結晶の詰め込みパラメータの分析.
主要な成果:
- 特定のポリモルフィック形式 (1a-A,1e-A,1f-A) はトポケミカル光ポリメリゼーションを経て結晶型ポリマーとなった.
- 熱ポリメリゼーションは,結晶型 (1a-A, 1e-A, 1f-A) と特定の無形型 (1e-B, 1f-B) の形態の両方で発生しました.
- アモルフな前体 (1e-B, 1f-B) から派生したポリマーは,それ自体がアモルフであった.
結論:
- キノディメタン結晶の分子包装の配置は,固体ポリメリゼーション反応性とその結果のポリマー構造に大きな影響を与えます.
- 主要なパッキングパラメータ (スタッキング距離,炭素間距離,方向角度) は,ポリメリゼーション結果を予測するために決定的です.
関連する概念動画
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,...