三価金属イオンを含む水クラスターにおける電子水化とイオン-電子ペア
William A Donald1, Maria Demireva, Ryan D Leib
1Department of Chemistry, University of California, Berkeley, California 94720-1460, USA.
Journal of the American Chemical Society
|March 12, 2010
まとめ
研究者は,基本的な水性核愛体である水性電子を研究した. 彼らは,安定した電子溶解三価ランタニドイオン水群を用いて,その散水エンタルピーを -1.3 eVと決定した.
科学分野:
- 物理化学 物理化学
- 化学物理 化学物理
- マテリアルサイエンス 材料科学
背景:
- 水素化された電子は水溶液における重要な核愛子であるが,液体の水におけるその一時的な性質は,重要な研究課題を提起する.
- 電子溶解熱力学を理解することは,電子帯の構造と水と水系システムの性質を特徴付けるのに不可欠です.
- 以前の研究では,陽子溶解エンタルピーにおける不確実性により,幅広い電子溶解エンタルピー値 (-1.0〜-1.8 eV) が得られた.
研究 の 目的:
- 水溶液中の電子の大量水分エンタルピーを正確に測定する.
- 安定したガス相群の水分子との電子相互作用を調査する.
- 陽子溶解値に頼らずに,電子水化エンタルピーを計算するための信頼できる方法を確立する.
主な方法:
- 余分な電子と溶媒で分離された三価金属イオンを含む安定した水クラスター (ランタニドクラスター) の生成.
- 電子捕獲時に水分子の損失に基づいて,La(H2O) n3+ (n = 42160) のアディアバティック再結合エネルギーの測定.
- リコンビネーションエンタルピーを無限クラスターサイズにエクストラポレーションして,サイズに依存する幾何学的な要因を考慮して,散発水分エンタルピーを決定します.
主要な成果:
- クラスターの大きさが増加するにつれて,電子の局所化の構造的移行が,表面結合 (n ≤ ~56) から完全に溶解 (n ≥ ~60) へと観察されました.
- 水素化されたランタニドクラスターの水素化数値の範囲で得られたアディアバティック再結合エネルギー.
- クラスターデータのエキストラポレーションにより,電子の大量水素化エンタルピーを -1.3 eVと決定しました.
結論:
- この研究では,ガス相クラスターデータから新しいエクストラポレーション法を使用して,電子の大量水素化エンタルピーを成功裏に決定しました.
- この結果は,電子溶解エンタルピーのより正確な値を提供し,以前の曖昧さを解消します.
- この方法は,絶対的な陽子または水素水素化エンタルピー推定の必要性を回避することによって,利点を提供します.
関連する概念動画
02:54Ions as Acids and Bases
Salts with Acidic Ions
Salts are ionic compounds composed of cations and anions, either of which may be capable of undergoing an acid or base ionization reaction with water. Aqueous salt solutions, therefore, may be acidic, basic, or neutral, depending on the relative acid-base strengths of the salt’s constituent ions. For example, dissolving the ammonium chloride in water results in its dissociation, as described by the equation:
Salts are ionic compounds composed of cations and anions, either of which may be capable of undergoing an acid or base ionization reaction with water. Aqueous salt solutions, therefore, may be acidic, basic, or neutral, depending on the relative acid-base strengths of the salt’s constituent ions. For example, dissolving the ammonium chloride in water results in its dissociation, as described by the equation:
02:51Metal-Ligand Bonds
The hemoglobin in the blood, the chlorophyll in green plants, vitamin B-12, and the catalyst used in the manufacture of polyethylene all contain coordination compounds. Ions of the metals, especially the transition metals, are likely to form complexes.
In these complexes, transition metals form coordinate covalent bonds, a kind of Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in...
In these complexes, transition metals form coordinate covalent bonds, a kind of Lewis acid-base interaction in which both of the electrons in the bond are contributed by a donor (Lewis base) to an electron acceptor (Lewis acid). The Lewis acid in...
02:48Ionic Bonding and Electron Transfer
Ions are atoms or molecules bearing an electrical charge. A cation (a positive ion) forms when a neutral atom loses one or more electrons from its valence shell, and an anion (a negative ion) forms when a neutral atom gains one or more electrons in its valence shell. Compounds composed of ions are called ionic compounds (or salts), and their constituent ions are held together by ionic bonds: electrostatic forces of attraction between oppositely charged cations and anions.
02:42Aqueous Solutions and Heats of Hydration
Water and other polar molecules are attracted to ions. The electrostatic attraction between an ion and a molecule with a dipole is called an ion-dipole attraction. These attractions play an important role in the dissolution of ionic compounds in water.
When ionic compounds dissolve in water, the ions in the solid separate and disperse uniformly throughout the solution because water molecules surround and solvate the ions, reducing the strong electrostatic forces between them. This process...
When ionic compounds dissolve in water, the ions in the solid separate and disperse uniformly throughout the solution because water molecules surround and solvate the ions, reducing the strong electrostatic forces between them. This process...
03:45Formation of Complex Ions
A type of Lewis acid-base chemistry involves the formation of a complex ion (or a coordination complex) comprising a central atom, typically a transition metal cation, surrounded by ions or molecules called ligands. These ligands can be neutral molecules like H2O or NH3, or ions such as CN− or OH−. Often, the ligands act as Lewis bases, donating a pair of electrons to the central atom. These types of Lewis acid-base reactions are examples of a broad subdiscipline called coordination...
01:19Complexation Equilibria: The Chelate Effect
In complexation reactions, metal atoms or cations interact with ligands to form donor-acceptor adducts called metal complexes. Ligands that bind through one donor site are monodentate, ligands with two donor sites are bidentate, and those with more than two donor sites are polydentate ligands. For example, ethylene diamine is a bidentate ligand that binds through two nitrogen donor atoms, forming a five-membered ring. EDTA is a polydentate ligand that binds through four oxygen and two nitrogen...