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化学学报
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化学学报 ›› 1997, Vol. 55 ›› Issue (11): 1091-1096. 上一篇    下一篇

研究论文

双冠醚配位作用的热力学性质V. 双(苯并-15-冠-5)与稀土(III)硝酸盐在无水乙腈溶液中分子内夹心配位作用

刘育;戚爱棣;陈荣悌;张有明   

  1. 南开大学化学系;西北师范学院化学系
  • 发布日期:1997-11-15

Complexation thermodynamics of bis (crown ether)s V. Intramolecular sandwich complexation of light lanthanoid nitrates with bis (benzo-15-crown-5) in anhydrous acetonitrile

LIU YU;QI AIDI;CHEN RONGTI;ZHANG YOUMING   

  • Published:1997-11-15

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本文用分光光度滴定法测定了双(苯并-15-冠-5)(1)与轻稀土(III)硝酸盐在无水乙腈溶液中, 20.0-35.0℃时分子内夹心配位作用的稳定常数, 进而计算了配位焓和配位熵, 并与母体苯并15-冠-5(2)的实验结果作了比较。化学计量法表明, 所有稀土硝酸盐均与双(苯并-15-冠-5)形成了1 : 1的配合物。从热力学的观点, 讨论了双冠醚分子结构、尺寸效应和空间构型等配位稳定性的影响。研究结果发现, 双冠醚(1)对于Eu^3^+具有较强的配位能力和配位选择性, Nd^3^+次之。配合物的稳定性主要来自于熵的贡献。

关键词: 分光光度法, 热力学性质, 硝酸盐, 乙腈, 冠醚

The spectrophotometric titrations have been performed in anhydrous acetonitrile at 20.0-35.0℃ to give the constants (logKs) and the thermodynamic parameters (ΔH°and TΔS°) for the intramolecular sandwich complexation of light lanthanoid (III) nitrates (La, Ce, Pr, Nd, Sm, Eu, Gd) with bis (benzo-15-crown-5) (1), and the results were compared with the data reported for the parent benzo-15-crown-5. The stoichiometry of the complex formed is 1 : 1 for all light lanthanoid nitrates complexation with bis (benzo-15-crown-5) (1). The effects of the bis (crown ether)'s size-fit concept, spatial arrangement, intramolecular constitution and other major factors upon complex stability are discussed from a viewpoint of thermodynamics. The thermodynamic parameters obtained indicate that the coordination of Eu^3^+ with bis (benzo-crown ether)(1) shows the strongest complexation ability and selectivity, and Nd^3^+ the second. The stabilities of light lanthanoid nitrates complexation with bis (crown ether) are contributed mainly through the coordination entropy.

Key words: SPECTROPHOTOMETRY, THERMODYNAMIC PROPERTIES, NITRATE, ACETONITRILE, CROWN ETHER

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