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A Combined Solution and Solid-State Study on the Tautomerism of an Azocalix[4]arene Chromoionophore.

Laura BaldiniDavide BalestriLuciano MarchiòAlessandro Casnati
Published in: Molecules (Basel, Switzerland) (2023)
Azocalixarenes functionalized with cation binding sites are popular chromoionophores due to the ease of synthesis and the large complexation-induced shifts of their absorption band that originate from an azo-phenol-quinone-hydrazone tautomerism. Despite their extensive use, however, a thorough investigation of the structure of their metal complexes has not been reported. We describe herein the synthesis of a new azocalixarene ligand ( 2 ) and the study of its complexation properties with the Ca 2+ cation. Through a combination of solution ( 1 H NMR and UV-vis spectroscopies) and solid-state (X-ray diffractometry) techniques, we demonstrate that metal complexation induces a shift of the tautomeric equilibration towards the quinone-hydrazone form, while deprotonation of the complex results in the reversion to the azo-phenol tautomer.
Keyphrases
  • solid state
  • ionic liquid
  • high resolution
  • magnetic resonance imaging
  • high glucose
  • computed tomography
  • endothelial cells
  • mass spectrometry