水溶液におけるアニオン-π相互作用の熱力学
Paloma Arranz-Mascarós1, Carla Bazzicalupi, Antonio Bianchi
1Department of Inorganic and Organic Chemistry, University of Jaen, 23071, Jaen, Spain.
Journal of the American Chemical Society
|December 25, 2012
まとめ
アニオン-π相互作用は,熱ではなくエントロピーによって駆動される水中の有電荷分子にとって重要な安定性を提供します. これらの相互作用は,分子結合と複合体の形成を理解するために極めて重要です.
科学分野:
- 超分子化学 超分子化学
- 物理化学 物理化学
- クリスタログラフィーです.
背景:
- アニオン認識は,生物学的および化学的なシステムにおいて不可欠です.
- アニオン-πのような非共性相互作用を理解することは,分子受容体の設計の鍵です.
- ニトロソアミノピリミジン誘導体は,充電された種の潜在的受容体として機能する.
研究 の 目的:
- ニトロゾアミノピリミジン受容体とのアニオン結合の背後にある熱力学的原動力を調査する.
- 結合安定性に対するアニオン-π相互作用の寄与を定量化するために.
- これらの相互作用の構造的基礎を,結晶学分析によって解明する.
主な方法:
- 結合定数と熱力学パラメータを決定するための電位計定位.
- 結合熱力学の正確な測定のための同熱定位熱計 (ITC).
- 受容体-アニオン複合体の固体構造を決定するためのX線結晶学.
主要な成果:
- アニオン-π相互作用は,結合の自由エネルギーに約-10 kJ/molの貢献をします.
- 結合は主に不熱性であり,有意な好ましいエントロピー貢献度 (TΔS°) があります.
- 結晶構造は短いCN··セントロイド距離 (2.786(3) Å) を明らかにし,強いアニオン-π相互作用を示した.
結論:
- アニオン-π相互作用は,高電荷アニオンに対する水溶液における重要な安定力である.
- 観察されたエントロピック好適性は,結合時に水構造の破壊が減少することを示唆しています.
- この研究は,アニオン-π相互作用による効率的なアニオン認識のための構造的および熱力学的証拠を提供します.
関連する概念動画
01:28Ionic Association
The ionic association is the association of oppositely charged ions in an electrolyte solution to form ion pairs. Bjerrum defined ion pairs as two oppositely charged ions whose electrostatic attraction exceeds the thermal energy of the system, typically expressed as 2kT. Electrostatic attraction depends on ionic charge, separation distance, and the dielectric constant of the medium. Thermal energy, represented by kT, reflects the tendency of ions to move independently due to molecular motion.
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...
03:13Intermolecular Forces
Atoms and molecules interact through bonds (or forces): intramolecular and intermolecular. The forces are electrostatic as they arise from interactions (attractive or repulsive) between charged species (permanent, partial, or temporary charges) and exist with varying strengths between ions, polar, nonpolar, and neutral molecules. The different types of intermolecular forces are ion–dipole, dipole–dipole, hydrogen bonds, and dispersion; among these, dipole–dipole, hydrogen bonds, and dispersion...
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:
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...
03:38Polyprotic Acids
Acids are classified by the number of protons per molecule that they can give up in a reaction. Acids such as HCl, HNO3, and HCN that contain one ionizable hydrogen atom in each molecule are called monoprotic acids. Their reactions with water are: