Comparison of two molecular design strategies for the development of an ammonium ionophore more highly selective than nonactin

Shin ichi Sasaki, Tsuyoshi Amano, Gou Monma, Takeshi Otsuka, Naoko Iwasawa, Daniel Citterio, Hideaki Hisamoto, Koji Suzuki

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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 KNH4+,K+pot≡ -1.5 and log KNH4+,Na+pot = -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 KNH4+,K+pot = -2.1 and log KNH4+,Ca2+pot = -1.6). As an overall conclusion, the cyclic ionophores TD19C6 and TD20C6 are the best ammonium-selective ionophores developed to date.

Original languageEnglish
Pages (from-to)4845-4848
Number of pages4
JournalAnalytical chemistry
Issue number18
Publication statusPublished - 2002 Sep 15


ASJC Scopus subject areas

  • Analytical Chemistry

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