Chemistry and Biochemistry
Bayer School of Natural and Environmental Sciences
ATRA, ATRC, ATRP, Coordination Polymers, Ligand Design, Radical processes
This dissertation focuses on the ligand design for atom transfer radical processes and direct reduction method. Atom transfer radical processes such as addition (ATRA), polymerization (ATRP) and cyclization (ATRC) are the fundamental organic reactions in which addition of alkyl halide via free radical means results in the formation of monoadducts or polymers. We have designed tris(2-pyridylmethyl)amine based ligands for ATRP, where systematic addition of the electron donating groups on the pyridine rings of TPMA, resulted in formation of three ligands; TPMA*1, TPMA*2 and TPMA*3. As indicated by electrochemical studies, a nearly stepwise decrease (DE~60 mV) of E1/2 values on going from [CuII(TPMA)Br][Br] to [CuII(TPMA*3)Br][Br], confirming that the presence of electron donating groups increased the reducing ability of the corresponding copper(I) complexes. The complexes were utilized for Activator Regenerated by Electron Transfer (ARGET) ATRP, the preliminary results indicated that the TPMA*2 ligand could have a higher future potential in copper catalyzed ATRP than TPMA*1 and TPMA*3.
Secondly, a series of mononuclear mixed ligand copper(II) complexes with deprotonated L-amino acids (aa = glycine, alanine, phenylalanine and proline) and bidentate N-based ligands (NN = 1, 10-phenanthroline, 2, 2'-bipyridine), [CuII(aa)(NN)Cl] were originally designed for ATRA. However, these complexes were successfully utilized as precursors for the synthesis of copper(I) cyanide (CuCN) coordination polymers via direct reduction method. This method has provided an efficient alternative to traditionally used solvo- and hydrothermal methods, where [CuII(aa)(NN)Cl] complexes activated the cyanide functionality of the diazo radical initiator, 2, 2′-azobis(2-methylpropionitrile) (AIBN) to synthesize multi-dimensional CuCN polymers. We observed that the dimensionality of the polymers was dependent on the structure of the ligand. One-dimensional (1D) polymers were exclusively formed with the aromatic N-based ligands whereas two- (2D) and three-dimensional (3D) frameworks were synthesized with aliphatic amines. We have observed that the ligand design has successfully regulated the size of the pores along with dimensionality. The work in this dissertation provided a significant contribution in two different fields; homogenous catalysis and material synthesis. With the help of the ligand design, we were able to understand as well as regulate the atom transfer radical processes and direct reduction method.
Kaur, A. (2014). Development of Highly Active Ligands for Copper Catalyzed Atom Transfer Radical Processes (Doctoral dissertation, Duquesne University). Retrieved from https://dsc.duq.edu/etd/734