Cargando…

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

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 inves...

Descripción completa

Detalles Bibliográficos
Autores principales: Baldini, Laura, Balestri, Davide, Marchiò, Luciano, Casnati, Alessandro
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2023
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10304982/
https://www.ncbi.nlm.nih.gov/pubmed/37375259
http://dx.doi.org/10.3390/molecules28124704
Descripción
Sumario: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.