New Heteroleptic Zinc and Magnesium Complexes for the Synthesis and Chemical Recycling of Bioderived Polymer

The pressing issue of climate change underscores an urgent need for sustainable materials, particularly within the plastics industry. This imperative has shifted focus towards biopolymers like aliphatic polyesters and polycarbonates. These materials offer promising solutions for various applications due to their derivation from renewable resources, coupled with their biodegradability and chemical recyclability. The production of these polymers and their copolymers often employs ring-opening polymerization (ROP) of lactones and cyclic carbonates, a process efficiently catalyzed by metal complexes. Among the diverse catalysts available, those based on zinc and magnesium are highly favoured for their low toxicity, high activity, and precise control over polymerization. Notably, some of us has recently developed specific zinc and magnesium complexes featuring phenoxy-imino-pyridine ligands, which have demonstrated exceptional activity in both the production and chemical recycling of polylactide (PLA). Having observed that the ligand's electronic properties significantly impact catalytic activity, here we are presenting the synthesis of new heteroleptic zinc and magnesium complexes, based on an easily synthesized, economical, and low-cytotoxic naphthoxy-imino-pyridine ligand. After a complete characterization, we evaluated their catalytic performance in the homo- and copolymerization of various bio-derived cyclic esters and carbonates. Finally, we explored the effectiveness of the zinc complex in the microwave-assisted depolymerization of polytrimethylene carbonate and its copolymers, promoting a sustainable approach to chemical recycling.