冠醚与金属离子配位作用的扩环效应  

Rign-enlargement Effects upon Cation Complexation with Crown Ether

作　　者：刘育[1] 王晓东[1] 卜显和[1] 陈荣悌[1] 大内幹雄 井上佳久[3] 

机构地区：[1]南开大学化学系,天津300071 [2]日本姬路工业大学应用化学系 [3]日本姬路工业大学物质科学系

出　　处：《物理化学学报》1994年第12期1105-1109,共5页Acta Physico-Chimica Sinica

摘　　要：Calorimetric Titrations in anhydrous acetonitrile at 298.15K have been performed to give the complex stability constants and thermodynamic properties for the complexation reactions of sodium thiocyanate and potassium thiocyanate with dibenzo-18-crown-6(Ⅰ), dibenzo-20-crown-6 (Ⅱ) and dibenzo-22-crown-6(Ⅲ ). The complex stability constanta, reaction enthalpies and (entropies were calculated directly by using calorimeter connected to an CA-033 Ancrocomputer. Data analyses assuming 1:1 stoichiometry were sussessfully applied to all of the crown ether-cation combinations employed. The thermodynamic parameters obtained and examination of CPK molecular models reveal that the less-symmetrical arrangement of donor oxygen induced by increasing methylene in dibenzo-18-crown-6 molecule and lead to an unfavorable conformation for complexation compared with parent crown ether. The complex stability constants are lower than those of dibenzo-18-crown-6(Ⅰ) for the ligands (Ⅱ ) and (Ⅲ) with Na+ and K+ but the relative cation selectivity for K+/Na+ are increased respectively. The effects of molecular structure of benzo crown ether and cation diameter upon complex stability are discussed from a viewpoint of thermodynamics.Calorimetric Titrations in anhydrous acetonitrile at 298.15K have been performed to give the complex stability constants and thermodynamic properties for the complexation reactions of sodium thiocyanate and potassium thiocyanate with dibenzo-18-crown-6(Ⅰ), dibenzo-20-crown-6 (Ⅱ) and dibenzo-22-crown-6(Ⅲ ). The complex stability constanta, reaction enthalpies and (entropies were calculated directly by using calorimeter connected to an CA-033 Ancrocomputer. Data analyses assuming 1:1 stoichiometry were sussessfully applied to all of the crown ether-cation combinations employed. The thermodynamic parameters obtained and examination of CPK molecular models reveal that the less-symmetrical arrangement of donor oxygen induced by increasing methylene in dibenzo-18-crown-6 molecule and lead to an unfavorable conformation for complexation compared with parent crown ether. The complex stability constants are lower than those of dibenzo-18-crown-6(Ⅰ) for the ligands (Ⅱ ) and (Ⅲ) with Na+ and K+ but the relative cation selectivity for K+/Na+ are increased respectively. The effects of molecular structure of benzo crown ether and cation diameter upon complex stability are discussed from a viewpoint of thermodynamics.

关 键 词：冠醚 金属离子 配位作用 扩环效应 

分 类 号：O623.423[理学—有机化学]