Solvent-Triggered Long-Range Proton Transport in 7-Hydroxyquinoline Using a Sulfonamide Transporter Group

J Org Chem. 2022 May 20;87(10):6794-6806. doi: 10.1021/acs.joc.2c00494. Epub 2022 May 5.

Abstract

The ability of long-range proton transport by substitution of 7-hydroxyquinoline at the eighth position with sulfonamide and sulfonylhydrazone rotor units to act as a crane-arm has been studied. Different proton transport pathways triggered by different stimuli have been established depending on the structure of the crane-arms. Solvent-driven proton switching from OH to the quinoline nitrogen (Nquin) site, facilitated by a sulfonamide transporter group in polar protic and aprotic solvents, has been confirmed by optical (absorption and fluorescence) and NMR spectroscopies as well as by single-crystal X-ray structure analysis. Photoinduced long-range proton transport to the Nquin site upon 340 nm UV light irradiation has been estimated in sulfonylhydrazone, which is not sensitive to solvent-driven switching. Both compounds have exhibited acid-triggered switching by trifluoroacetic acid due to the formation of a stable six-membered intramolecular hydrogen bonding interaction between the protonated Nquin and crane-arm. The structures of acid-switched form were confirmed by NMR spectroscopy and single-crystal X-ray structure analysis. The behavior of the compounds suggests a big step forward in the advanced proton pump-switching architecture because they cover three distinct driving forces in the switching process: solvent, light, and acid.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Hydrogen Bonding
  • Hydroxyquinolines* / chemistry
  • Protons*
  • Quinine
  • Solvents / chemistry
  • Sulfonamides

Substances

  • Hydroxyquinolines
  • Protons
  • Solvents
  • Sulfonamides
  • Quinine
  • 7-hydroxyquinoline