Design, synthesis and application of carbazole macrocycles in anion sensors

Alo Rüütel, Ville Yrjänä, Sandip A Kadam, Indrek Saar, Mihkel Ilisson, Astrid Darnell, Kristjan Haav, Tõiv Haljasorg, Lauri Toom, Johan Bobacka, Ivo Leito*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

12 Citations (Scopus)
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Carboxylate sensing solid-contact ion-selective electrodes (ISEs) were created to provide a proof-of-concept ISE development process covering all aspects from in silico ionophore design to functional sensor characterization. The biscarbazolylurea moiety was used to synthesize methylene-bridged macrocycles of different ring size aiming to fine tune selectivity towards different carboxylates. Cyclization was achieved with two separate strategies, using either amide synthesis to access up to –[CH 2] 10–macrocycles or acyl halides to access up to –[CH 2] 14–macrocycles. Seventy-five receptor–anion complexes were modelled and studied with COSMO-RS, in addition to all free host molecules. In order to predict initial selectivity towards carboxylates, 1H NMR relative titrations were used to quantify binding in DMSO-d 6/H 2O solvent systems of two proportions – 99.5%:0.5% m/m and 90.0%:10.0% m/m, suggesting initial selectivity towards acetate. Three ionophores were selected for successful sensor prototype development and characterization. The constructed ion-selective electrodes showed higher selectivity towards benzoate than acetate, i.e., the selectivity patterns of the final sensors deviated from that predicted by the classic titration experiments. While the binding constants obtained by NMR titration in DMSO-d 6/H 2O solvent systems provided important guidance for sensor development, the results obtained in this work emphasize the importance of evaluating the binding behavior of receptors in real sensor membranes.

Original languageEnglish
Pages (from-to)1901-1914
Number of pages14
JournalBeilstein Journal of Organic Chemistry
Publication statusPublished - 4 Aug 2020
MoE publication typeA1 Journal article-refereed


  • anion sensors
  • carboxylates
  • ionophores
  • macrocycles
  • sensor prototype


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