Advanced ligand design in atom transfer radical polymerisation : on the development of new catalysts based on guanidinoquinoline copper complexes

  • Fortschrittliches Liganden-Design in der Atomtransfer-Radikalpolymerisation: Über die Entwicklung neuer Katalysatoren, basierend auf Guanidinochinolin-Kupferkomplexen

Rösener, Thomas; Herres-Pawlis, Sonja (Thesis advisor); Pich, Andrij (Thesis advisor)

Aachen (2018, 2019)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2018

Abstract

This thesis deals with the development of new guanidinoquinoline ligands for their use in Atom Transfer Radical Polymerisation. Copper halide complexes of guanidinoquinoline (GUAqu) ligands with a rigid aromatic backbone were found to be suitable for ATRP in previous studies. However, it appeared that these complexes are only barely soluble in apolar monomers, limiting the control of a polymerisation reaction. The solubility of these complexes could be enhanced via alkylation of the quinoline backbone. A method for the synthesis of C6-substituted GUAqu ligands was developed. Starting from para-substituted anilines, the synthesis of differently substituted GUAqu ligands could be accomplished in high yields. Copper(I) and copper(II) complexes of these ligands were studied comprehensively with regard to their suitability in ATRP and structure-reactivity correlations. The complexes were structurally characterised in solid state and in solution. Redox potentials E(1/2) and equilibrium constants K(ATRP) of these complexes were determined and correlated. K(ATRP) represents the central equilibrium constant of the ATRP equilibrium and has a huge influence on the catalyst’s activity. It is demonstrated that substitution only minimally influences the activity of DMEG6Rqu complexes but significantly influences the activity of TMG6Rqucomplexes. KATRP consists of the rate constant of activation k(act) and the rate constant of deactivation(deact). These constants were also determined for the complexes. Copper halide complexes of alkylated GUA6Rqu ligands were tested in bulk ATRP of styrene.GUA6buqu complexes turned out to be highly soluble in the monomer, polymerisations showed high control. Furthermore, attempts were made to predict catalyst activities by means of density functional theoretical calculations and isodesmic reactions. This should enable in silico development of newATRP catalysts. Correct predictions were possible in the case of unsubstituted ligands. The high conformational freedom in substituted ligands on the other hand rendered correct predictions impossible. Moreover, a new class of guanidine pincer ligands with a rigid aromatic backbone was synthesised:GUA2phaz ligands with a phenazine backbone. Copper(I) and copper(II) complexes as well as onezinc(II) complex were synthesised and characterised. Preliminary studies with regard to ATRP activity revealed that copper halide complexes of these ligands might be promising catalysts in ATRP.

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