Organic-inorganic hybrid materials based on phthalocyanine, calix[4]arene and polyoxometalate scaffolds

  • Organisch-anorganische Hybridmaterialien aus den Bausteinen Phthalocyanin, Calix[4]aren und Polyoxometallat

Sarwar, Sidra; Kögerler, Paul (Thesis advisor); Oppel, Iris (Thesis advisor)

Aachen : RWTH Aachen University (2021)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2021

Abstract

This doctoral thesis describes the synthesis and characterization of discrete hybrid structures containing organic and inorganic scaffolds covalently linked through a single-metal ion. In the first part, we show how to combine a phthalocyanine and a monolacunary Keggin phosphotungstate into double-decker structures of 4f-centers (Tb(III) and Dy(III)) that exhibit strong magnetic anisotropy in axial ligand fields. Both tetradentate ligands, differing in their electronic properties and charges, encapsulate 4f-ion in a distorted square-antiprismatic coordination geometry. The magnetic studies reveal marginal magnetic anisotropy of terbium derivative, whereas the dysprosium analogue exhibit significant slow magnetic relaxation. In addition, the impact of electronic nature of phthalocyanine ring on the properties of hybrid complexes has been studied by replacing the peripheral protons with electron-donating (2,6-di-iso-propylphenoxy) and electron-withdrawing (fluorine) groups. UV-Vis spectra and cyclic voltammograms of derivatized complexes show a shift in the signals due to the changes in the electronic structure of complexes. The magnetic ac-data of these complexes reveal the impact of peripheral derivatization by preferring different pathways to the magnetization reversal. The second part describes the integration of a p-tert-butylcalix[4]arene and a monolacunary Keggin phosphotungstate into heteroleptic double-decker complexes of Ce(IV) and Zr(IV), representing the first example of combining these scaffolds through a single-metal ion. The cyclic voltammograms of these complexes display two reversible redox waves at positive potentials that could be attributed to the formation of phenoxy radical and phenoxylium cation on the p-tert-butylcalix[4]arene-skeleton. This represents the first report in which a calix[4]arene shows redox-active behavior upon coordination to metal, suggesting their potential as electroactive materials in single-molecule switches.

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