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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对配位稳定性的影响.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.
In this paper, the stability of the sandwich coordination between the bis (benzo-15-crown-5) (1) and the light rare earth (Ⅲ) nitrate in anhydrous acetonitrile at 20.0 ~ 35.0 ℃ was determined by spectrophotometric titration Constant, and then calculated the enthalpy and coordination entropy and compared with the experimental results of the benzo-15-crown-5 (2) .The stoichiometry showed that all the rare earth nitrate and bis (benzo-15 - crown-5) formed a 1: 1 complex.From the thermodynamic point of view, the double crown ether molecule structure, size effect and spatial configuration of the coordination stability of the study results showed that double crown ether 1) has strong coordination ability and coordination selectivity to Eu ~ (3+), followed by Nd ~ (3+) .The stability of the complex mainly comes from the contribution of entropy.