マルチフェロイドの振る舞いは,ペロブスキートABX3アーキテクチャの金属有機フレームワーク (MOF) での秩序-無秩序の水素結合移行と関連しています
Prashant Jain1, Vasanth Ramachandran, Ronald J Clark
1Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306-4390, USA.
Journal of the American Chemical Society
|September 4, 2009
まとめ
この研究は,金属有機フレームワークに基づいた新しい種類のマルチフェロ材料を導入します. これらの化合物は,水素結合によって誘発される,電気的相変化と弱い鉄磁性の両方を表します.
科学分野:
- マテリアルサイエンス 材料科学
- 固体物理 固体物理学
- 化学 化学は化学です.
背景:
- ペロブスキートに関連する金属有機構造は,新しい特性のために探求されています.
- マルチフェロ材料は,共存する磁気と電気の順序を示す.
- 水素結合は,材料の特性において重要な役割を果たします.
研究 の 目的:
- メタル・オーガニック・フレームワークの一連のマルチフェロイドの振る舞いを調査する.
- 結晶構造,水素結合,およびマルチフェロ性との関係を調査する.
- 先進的な電子アプリケーションのための新しい材料を特定する.
主な方法:
- 一般的な式 [(CH(3)) (((2) NH(2)]M(HCOO) (((3) の金属有機フレームワークの合成.
- 温度依存測定を用いた相変化の特徴化.
- 弱い鉄磁性を含む磁性特性の調査.
主要な成果:
- 4つの化合物すべて (M = Mn, Fe, Co, Ni) は,160-185 Kの間のパラ電気-アンチフェロ電気移行を示しました.
- これらの移行は,ダイメチルアモニウムカチオンにおける秩序-乱雑現象と関連しています.
- すべての化合物において,40K未満のCantedの弱い鉄磁性は観察されました.
結論:
- 電気的なオーダーリングのために水素結合を利用する新しいクラスのマルチフェロイクが発見されました.
- これらの金属有機フレームワークは,多機能材料の開発に有望なプラットフォームを提供します.
- 水素結合と磁気/電気の順序の相互作用は,それらのマルチフェロー的行動の鍵です.
関連する概念動画
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.
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...
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,...
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...
02:42Ionic 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...