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

ABSTRACT: 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 Ca²⁺ cation. Through a combination of solution (¹H 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.

SUBMITTER: Baldini L

PROVIDER: S-EPMC10304982 | biostudies-literature | 2023 Jun

REPOSITORIES: biostudies-literature

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

Baldini Laura L Balestri Davide D Marchiò Luciano L Casnati Alessandro A

Molecules (Basel, Switzerland) 20230612 12

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 (<b>2</b>) and the study of its complexation properties with th ...[more]

PMID: 37375259

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