Ligand Substituent Effects on Redox-Switchable Polymerization Catalysts

Plastic pollution necessitates the need for new sustainable polymer technologies. Such materials are accessible via the construction of biobased materials and biodegradable microstructural engineering. Such motifs can be rationally synthesized via redox-switchable catalysis, which exhibits orthogonal reactivity towards various monomers. In this vein, this work aims to ascertain ligand substitution as a modality of control over the orthogonal reactivity. By investigating a set of substituents on a phosphen ligand scaffold with varied electron-donating and electron-withdrawing effects, an investigation into the electronic properties of such catalysts is undertaken. Synthesis and characterization of one variant of the yttrium complexes of interest is presented, as well as its reactivity in ring-opening polymerizations. These findings are compared to previous work with another yttrium analogue. Essentially, no ligand substitution effect was found, but reactivity toward an additional orthogonal monomer was discovered.