Comparison of Two Molecular Design Strategies for the Development of an Ammonium Ionophore More Highly Selective than Nonactin
作者:Shin-ichi Sasaki、Tsuyoshi Amano、Gou Monma、Takeshi Otsuka、Naoko Iwasawa、Daniel Citterio、Hideaki Hisamoto、Koji Suzuki
DOI:10.1021/ac025713+
日期:2002.9.1
A series of ionophores for ammonium ion-selective electrodes was designed and synthesized, and their characteristics were examined. The design of the ionophores is based on two different strategies: (1) introduction of bulky blocking subunits (decalino groups) in 20- or 21-membered crown ethers (TD20C6 and TD21C6), the ring size of which is expected to be suitable for selective NH4+ recognition, as compared to the slightly smaller K+; and (2) preorganized tripodal ionophores based on a 6-fold substituted benzene ring in order to complementarily recognize the tetrahedral NH4+, in contrast to the spherical K+. Compared to nonactin, a natural product that is used as a representative NH4+ ionophore, the newly developed TD20C6 showed higher NH4+ selectivity over K+ while retaining the selectivity over Na+ (log = −1.5 and log = −2.5). On the other hand, a tripodal ionophore with pyrazole nitrogen atoms as NH4+ binding sites showed high NH4+/K+ selectivity but suffered from increased Ca2+ interference (log = −2.1 and log = −1.6). As an overall conclusion, the cyclic ionophores TD19C6 and TD20C6 are the best ammonium-selective ionophores developed to date.
一系列用于氨离子选择性电极的离子载体被设计和合成,并对其特性进行了检查。离子载体的设计基于两种不同的策略:(1)在20或21元环的冠醚中引入笨重的阻隔子单元(十环基团),其环尺寸预计与稍小的钾离子相比,更适合选择性识别NH4+;(2)基于六取代苯环的预组织三足离子载体,以补充性地识别四面体的NH4+,与球形的K+形成对比。与非行动菌素——一种用作代表NH4+离子载体的天然产物相比,新开发的TD20C6在保持对Na+的选择性的同时,对NH4+相比K+表现出更高的选择性(log = -1.5和log = -2.5)。另一方面,一种带有噁唑氮原子的三足离子载体作为NH4+的结合位点,展示了较高的NH4+/K+选择性,但存在钙离子干扰(log = -2.1和log = -1.6)。总体结论是,环状离子载体TD19C6和TD20C6是迄今为止开发的最佳氨选择性离子载体。