Issue 19, 2021

Imino-thiolate-templated synthesis of a chloride-selective neutral macrocyclic host with a specific “turn-off–on” fluorescence response for hypochlorite (ClO)

Abstract

A precise replacement of one oxygen atom with sulfur in the intra-annular amide-1-methylene-pyrene substituent allowed us to efficiently synthesize a novel macrocyclic host 2 for selective recognition of chloride ions. The high yield of the macrocyclization process (64%) between sterically demanding substrates was attributed to a combination of external and internal templating effects of chloride and – previously unrecognized in the literature – thioimidate anions –C([double bond, length as m-dash]N–)S (generated in situ by deprotonation of thioamide by sodium methoxide), respectively. Both templating agents help to adopt a favorable folded conformation of the open-chain intermediate leading to a sterically crowded structure of 2. The host was characterized by single crystal X-ray analysis and its anion recognition properties were determined by 1H-NMR titration experiments in a demanding (DMSO-d6 + 0.5% H2O) solvent mixture. The host exhibits one of the highest reported selectivities toward chloride among systems binding anions by hydrogen bonding interactions (Ka,Cl = 1130 M−1, Ka,Cl/Ka,anion up to 35.3). Host 2 is essentially nonfluorescent due to the quenching effect of a thioamide group, however, the selective oxidation of the C[double bond, length as m-dash]S moiety by the hypochlorite (ClO) anion was found to fully restore the fluorescence (λem = 377 nm). This demonstrates the first example of metal-free macrocyclic sensors for the selective detection of this biologically important analyte.

Graphical abstract: Imino-thiolate-templated synthesis of a chloride-selective neutral macrocyclic host with a specific “turn-off–on” fluorescence response for hypochlorite (ClO−)

Supplementary files

Article information

Article type
Research Article
Submitted
31 mar 2021
Accepted
14 jul 2021
First published
14 jul 2021

Org. Chem. Front., 2021,8, 5258-5264

Imino-thiolate-templated synthesis of a chloride-selective neutral macrocyclic host with a specific “turn-off–on” fluorescence response for hypochlorite (ClO)

K. Dąbrowa, M. Lindner, A. Tyszka-Gumkowska and J. Jurczak, Org. Chem. Front., 2021, 8, 5258 DOI: 10.1039/D1QO00504A

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements