Nishizawa Seiichi, Kamaishi Tomoyuki, Yokobori Tomoyuki, Kato Ryo, Cui Ying-Yu, Shioya Takeshi, Teramae Norio
Department of Chemistry, Graduate School of Science, Tohoku University, Aoba-ku, Sendai 980-8578, Japan.
Anal Sci. 2004 Nov;20(11):1559-65. doi: 10.2116/analsci.20.1559.
Facilitated SO4(2-) transfers by hydrogen bond-forming ionophores are investigated across the nitrobenzene (NB)-water interface by using polarography with a dropping electrolyte electrode. Bis-thiourea 1, alpha,alpha'-bis(N'-p-nitrophenylthioureylene)-m-xylene, is found to significantly facilitate the transfer of the highly hydrophilic SO4(2-) whereas its counterpart, N-(p-nitrophenyl)-N'-propylthiourea (ionophore 2), cannot. In contrast to the predominant formation of a 1:1 complex with SO4(2-) in the bulk NB phase, the SO4(2-) transfer assisted by 1 is indeed based on the formation of a 1:2 complex between SO4(2-) and ionophore, even under the condition of [SO4(2-)]aq >> [1]org. Such an exclusive formation of the 1:2 (SO4(2-) to ionophore) complex at the NB-water interface is not observed with structurally similar bis-thiourea 3, alpha,alpha'-bis(N'-phenylthioureylene)-m-xylene, where p-nitrophenyl moietes of bis-thiourea 1 are simply replaced by phenyl groups. The facilitated transfer of SO4(2-) with bis-thiourea 1 is further compared to that of HPO4(2-) and H2PO4- across the NB-water interface, which was previously shown to be assisted by 1 through the formation of the 1:1 and 2:1 (anion to ionophore) complexes, respectively. On the basis of these examinations, unique binding behaviors of hydrogen bond-forming ionophores at the NB-water interface are discussed, with a view towards development of ionophore-based anion-selective chemical sensors.
通过使用滴汞电解质电极的极谱法，研究了通过形成氢键的离子载体促进硫酸根离子（SO₄²⁻）在硝基苯（NB）-水界面的转移。发现双硫脲1，α，α'-双（N'-对硝基苯基硫脲基）-间二甲苯，能显著促进高亲水性SO₄²⁻的转移，而其类似物N-（对硝基苯基）-N'-丙基硫脲（离子载体2）则不能。与在本体NB相中主要形成1:1的SO₄²⁻络合物相反，即使在[SO₄²⁻]水相>>[1]有机相的条件下，由1辅助的SO₄²⁻转移实际上是基于SO₄²⁻与离子载体之间形成1:2的络合物。在结构相似的双硫脲3，α，α'-双（N'-苯基硫脲基）-间二甲苯中未观察到在NB-水界面处这种1:2（SO₄²⁻与离子载体）络合物的排他性形成，其中双硫脲1的对硝基苯基部分简单地被苯基取代。将双硫脲1促进的SO₄²⁻转移与HPO₄²⁻和H₂PO₄⁻在NB-水界面的转移进行了进一步比较，先前已表明它们分别通过形成1:1和2:1（阴离子与离子载体）络合物而得到1的辅助。基于这些研究，讨论了形成氢键的离子载体在NB-水界面的独特结合行为，以期开发基于离子载体的阴离子选择性化学传感器。
