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New hybrid guanidine-quinoline copper complexes and their use in atom transfer radical polymerization
New hybrid guanidine-quinoline copper complexes and their use in atom transfer radical polymerization
In this thesis, the synthesis and characterization of a family of seven new guanidine-quinoline hybrid ligands and their six CuI and seven CuII complexes is presented. The catalytic activities of the copper complexes in atom transfer radical polymerization (ATRP) reactions were studied and their electrochemical potentials, ATRP equilibria and reaction rate constants were determined. The molecular structures of the CuBr complexes showed bischelate tetrahedral coordination of the electron-rich ligands and a trigonal-planar geometry for the electron-poor ligands. Similar, the CuII halide complexes exhibited distorted bischelate trigonal-bipyramidal coordination for the electron-rich ligands and monochelate distorted square-pyramidal coordination for electronpoor CuCl2 complexes. All catalysts were found to polymerize styrene in high polymerization rates under controlled conditions. The use of copper complexes with electron-rich ligands resulted in faster catalysis and the [Cu(TMG6Methoxyqu)2]Br complex led to outstandingly fast ATRP reactions, yielding two to five times higher rate constants kp than other investigated catalysts. Electrochemical examinations of the CuBr2 complexes revealed that they exhibited increasing negative potentials for complexes with stronger electron-donating substituents. The potentials ranged from −0.439V to −0.545V (vs. Fc/Fc+). For the CuBr complexes, an increase of the electrochemical potential was found to lie in between 10mV and 35mV and the potentials of the CuCl2 complexes were found to be 40mV to 60mV lower than their CuBr2 counterparts. Most of the electrochemical potentials showed strong correlations with the data from polymerization studies. In correlation with the determined polymerization rates and electrochemical data, the KATRP values of the CuBr complexes were found to be larger for ligands bearing more electron-donating substituents. Our UV/Vis measurements afforded KATRP values ranging from 3.6 × 10-8 to 3.6 × 10-7. After addition of TEMPO to the equilibrium reaction, the kact values were determined to lie between 0.34 s-1 and 2.33 s-1 and values for kdeact were found to range from 5.9 × 106 s-1 to 1.3 × 107 s-1. The data further indicated, that the electron-rich ligands TMG6dmaqu and TMG6dbaqu form bidentate ATRP catalysts with the highest KATRP values known in the literature. The values are increased by one order of magnitude compared to 4,4’-dinonyl-2,2’-bipyridine (dNbpy) complexes.
ATRP, homogeneous catalysis, guanidine, copper, complex
Mannsperger, Johannes
2018
English
Universitätsbibliothek der Ludwig-Maximilians-Universität München
Mannsperger, Johannes (2018): New hybrid guanidine-quinoline copper complexes and their use in atom transfer radical polymerization. Dissertation, LMU München: Faculty of Chemistry and Pharmacy
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Abstract

In this thesis, the synthesis and characterization of a family of seven new guanidine-quinoline hybrid ligands and their six CuI and seven CuII complexes is presented. The catalytic activities of the copper complexes in atom transfer radical polymerization (ATRP) reactions were studied and their electrochemical potentials, ATRP equilibria and reaction rate constants were determined. The molecular structures of the CuBr complexes showed bischelate tetrahedral coordination of the electron-rich ligands and a trigonal-planar geometry for the electron-poor ligands. Similar, the CuII halide complexes exhibited distorted bischelate trigonal-bipyramidal coordination for the electron-rich ligands and monochelate distorted square-pyramidal coordination for electronpoor CuCl2 complexes. All catalysts were found to polymerize styrene in high polymerization rates under controlled conditions. The use of copper complexes with electron-rich ligands resulted in faster catalysis and the [Cu(TMG6Methoxyqu)2]Br complex led to outstandingly fast ATRP reactions, yielding two to five times higher rate constants kp than other investigated catalysts. Electrochemical examinations of the CuBr2 complexes revealed that they exhibited increasing negative potentials for complexes with stronger electron-donating substituents. The potentials ranged from −0.439V to −0.545V (vs. Fc/Fc+). For the CuBr complexes, an increase of the electrochemical potential was found to lie in between 10mV and 35mV and the potentials of the CuCl2 complexes were found to be 40mV to 60mV lower than their CuBr2 counterparts. Most of the electrochemical potentials showed strong correlations with the data from polymerization studies. In correlation with the determined polymerization rates and electrochemical data, the KATRP values of the CuBr complexes were found to be larger for ligands bearing more electron-donating substituents. Our UV/Vis measurements afforded KATRP values ranging from 3.6 × 10-8 to 3.6 × 10-7. After addition of TEMPO to the equilibrium reaction, the kact values were determined to lie between 0.34 s-1 and 2.33 s-1 and values for kdeact were found to range from 5.9 × 106 s-1 to 1.3 × 107 s-1. The data further indicated, that the electron-rich ligands TMG6dmaqu and TMG6dbaqu form bidentate ATRP catalysts with the highest KATRP values known in the literature. The values are increased by one order of magnitude compared to 4,4’-dinonyl-2,2’-bipyridine (dNbpy) complexes.