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化学学报
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化学学报 ›› 2006, Vol. 64 ›› Issue (16): 1716-1722. 上一篇    下一篇

研究论文

N-(二茂铁酰胺基)硫脲类阴离子受体

韩洁1, 黎朝1, 刘文侠1, 杨睿1,2, 江云宝*,1   

  1. (1厦门大学化学化工学院化学系 现代分析科学教育部重点实验室 厦门 361005)
    (2西南大学化学化工学院 重庆 400715)
  • 投稿日期:2006-01-11 修回日期:2006-07-17 发布日期:2006-08-28
  • 通讯作者: 江云宝

N-(Ferrocamido)thiourea-Based Anion Receptors

HAN Jie1; LI Zhao1; LIU Wen-Xia1; YANG Rui1,2; JIANG Yun-Bao*,1   

  1. (1 Department of Chemistry and the MOE Key Laboratory of Analytical Sciences, College of Chem-istry and Chemical Engineering, Xiamen University, Xiamen 361005)
    (2 College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715)
  • Received:2006-01-11 Revised:2006-07-17 Published:2006-08-28
  • Contact: JIANG Yun-Bao

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我们将N-(苯甲酰胺基)硫脲类阴离子识别受体研究拓展至N-(二茂铁酰胺基)硫脲, 设计合成了N-(二茂铁甲酰胺基)-N'-(取代苯基)硫脲(3a～3e, 取代基X＝p-OCH3, p-CH3, H, m-Br, m-CF3), 其中二茂铁基系芳香性的电化学活性基团、“—NH—”为连接臂．研究的目的是进一步理解 “—NH—”连接臂的特性和3a～3e作为阴离子的电化学响应受体的可行性. 我们发现, 3a～3e分子中的N'-苯环取代基不影响其半波电位(0.31V vs. Ag/AgNO3); 二茂铁环芳香质子和酰胺基—NH质子的核磁化学位移不受取代基的影响, 而N'-苯基芳香质子和硫脲—NH质子的化学位移显著地受制于取代基; 说明受体3分子中酰肼基N—N单键高度扭曲, 阻碍了N'-苯环取代基电子效应传递至二茂铁基. 我们观察到乙腈中3的氧化电位因阴离子如CH3CO2－和F－的结合负移200 mV, 二茂铁基芳香质子的化学位移向高场移动, 意味着阴离子结合诱导了受体3分子中酰肼基N—N单键构型变化, 使阴离子结合信息得以传递至二茂铁环. 吸收光谱滴定实验表明, 乙腈中3a～3e与阴离子结合时在约315 nm处出现新的吸收峰, 光谱红移达5820 cm－1, 阴离子如CH3CO2－和F－的结合常数在106 mol－1•L, 均远高于传统的二苯基硫脲类受体(1); 我们还发现, 尽管1和3a～3e分子中硫脲—NH质子酸性对取代基的依赖性相近, 3a～3e之阴离子结合常数的取代基效应强于1. 我们认为, 这是由于N—N键的变构作用导致3a～3e的吸收光谱红移、阴离子结合常数和阴离子结合常数的取代基效应远高于传统的N,N'-二苯基硫脲类受体, 因而体现了“—NH—”连接臂的独特性质.

关键词: 阴离子受体, 二茂铁, 硫脲, 变构作用, —NH—连接臂, 循环伏安

We extended our research on N-benzamidothiourea based anion receptors to N-ferrocamidothioureas and synthesized N-ferrocamido-N'-(substituted phenyl)thioureas (3a～3e, substituent X＝p-OCH3, p-CH3, H, m-Br, and m-CF3). In 3a～3e an electrochemically active ferrocene moiety was employed as an aromatic counterpart of phenyl and —NH— was a spacer linking ferrocene signal reporter and the thiourea binding-site. Cyclic voltammetric ex-periments carried out in acetonitrile indicated that the half-wave potentials of 3a～3e of 0.31 V vs. Ag/AgNO3 were independent of the substituent at N'-phenyl ring. It was found that the 1H NMR chemical shifts of the aromatic protons at ferrocene moi-ety and the amido —NH proton in 3 did not, whereas those of the N'-phenyl aromatic pro-tons and the thioureido —NH protons did vary when the N'-phenyl substituent was changed. The azino N—N bond was hence concluded to be twisted that blocked the electronic communication between the ferrocene moiety and thiourea anion-binding site. Yet we experimentally observed that the oxidation poten-tials of 3a～3e shifted by ca. －200 mV in the presence of anions such as CH3CO2－ and F－ in acetonitrile and the chemical shifts of the ferrocene aromatic protons shifted to high field upon anion binding to the thiourea moiety in 3a～3e. A conformation change in the N—N bond was hence assumed for 3a～3e upon anion binding. Absorption titrations indicated that anion binding to 3a～3e resulted in a new absorption band at ca. 315 nm with a spectral red-shift of 5820 cm-1 irrespective of the substituent. The spectral red-shift, anion affinity of 106 mol－1•L orders of magnitude for CH3CO2－ and F－, and substituent effect on the anion affinity of 3a～3e were found much higher than those of the corresponding traditional N,N'-diphenylthiourea coun-terparts (1). It was concluded that anion binding induced conformational change in 3a～3e led to enhanced anion affinity and substituent effect on the anion affinity, information indicative of allosteric character of the receptors and instructive for designing N-arylamido-N'-arylthiourea based anion receptors. Results reported here further supported the advantages of the “—NH—” spacer in N-benzamidothiourea-based anion receptors.

Key words: anion receptor, ferrocene, thiourea, allosterism, —NH— spacer, cyclic voltammetry