物理化学学报 >> 1994, Vol. 10 >> Issue (12): 1105-1109.doi: 10.3866/PKU.WHXB19941210

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冠醚与金属离子配位作用的扩环效应

刘育, 王晓东, 不显和, 陈荣悌, 大内幹雄, 井上佳久   

  1. 南开大学化学系，天津 300071|日本姬路工业大学，应用化学系 671-22；物质科学系678-12
  • 收稿日期:1993-08-20 修回日期:1993-12-22 发布日期:1994-12-15
  • 通讯作者: 刘育

Rign-enlargement Effects upon Cation Complexation with Crown Ether

Liu Yu, Wang Xiao-Dong, Bu Xian-He, Chen Rong-Ti, Ouchi Mikio, Inoue Yoshihisa   

  1. Department of Chemistry,Nankai University,Tianjin 300071|Department of Applied Chemistry,Himeji Institute of Technology,Shosha,Himeji,Hyogo671-22,Japan|Department of Material Science,Himeji Institute of Technology,Kamigori,Hyogo678-12;Japan
  • Received:1993-08-20 Revised:1993-12-22 Published:1994-12-15
  • Contact: Liu Yu

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关键词: 冠醚, 配位作用, 量热滴定, 热力学性质, 扩环效应

Abstract:

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 microcomputer. 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.

Key words: Crown ether, Complexation, Calorimetric titration, Thermodynamics, Ring-enlargement effect