Design, Synthesis and Catalysis Applications of Bio-Inspired Metal-Containing Polymers

The quest for the construction of artificial enzyme models able to mimic the activity of metalloenzymes is lucrative research filed for many chemists. There have been considerable efforts in design and synthesize various bio-mimetic systems to achieve the enzymatic activity. One such enzyme mimicking system is to use of macromolecular environment such as polymers with the metal active sites has attracted tremendous interest and resulting in the formation of metal-containing polymers/metallopolymers. We believe that by integrating metal ions within the polymer frameworks using metal-ligand coordination will offer greater control over the choice of various functional groups, control of hydrophilicity/hydrophobicity and secondary coordination network offered by the polymer frameworks for the metal ions. These metal-containing polymers will be expected to serve as the better enzymatic models. The aim of this dissertation is to study the polymer promoted catalytic activity of novel metal-containing polymers. By taking the advantages of polymer synthesis methods, particularly, controlled free radical polymerization methods such as RAFT and ATRP, and post-polymerization methods, we prepared well-defined polymers with the desired functional groups. The metal ions were incorporated into the polymer network via metal-ligand coordination under dilute conditions to induce polymer cross-linking to yield metal-containing single chain polymer nanoparticles (M-SCNPs). These soft nano-sized polymeric nanoparticles were then used as enzymatic model systems for catalysis applications. In chapter 2 of this dissertation work, we explored the use of metallofoldamers containing Ni-thiolate co-factors in a folded polymer framework for the selective photoreduction of CO2. The catalysis results indicated that polymer framework promoted the activity of Ni active sites towards selective CO2 reduction to CO under photochemical conditions. In chapter 3, we demonstrated that Cu-containing SCNPs promoted the activity towards the selective hydroxylation reactions. The catalytic activity towards phenol substrates catalyzed Cu-SCNPs was studied and the results indicate that the selectivity was largely influenced by the dynamics of the folded polymer backbone. The unsaturation of coordination sites to Cu ions limits the cooperative catalysis. We solved this problem by designing a random copolymer having well-defined ligands with a coordination site for Cu-ions. We studied the polymer promoted cooperative O2 activation and how the catalytic efficiency was influenced by polymer flexibility and the mole fraction of Cu sites in copolymers which is described in chapter 4. Further extension of this work by introducing hydrophobic microenvironment for the Cu sites and how it will affect the catalytic activity was demonstrated in chapter 5