Reversible On/OffSwitching of Lactide Cyclopolymerization with a Redox-Active Formazanate Ligand

Redox-switching of a formazanate zinc catalyst inring-opening polymerization (ROP) of lactide is described. Using aredox-active ligand bound to an inert metal ion (Zn2+) allowsmodulation of the catalytic activity by reversible reduction/oxidation chemistry at a purely organic fragment. A combination ofkinetic and spectroscopic studies, together with mass spectrometryof the catalysis mixture, provides insight in the nature of the activespecies and the initiation of lactide ring-opening polymerization.The mechanistic data highlight the key role of the redox-activeligand and provide a rationale for the formation of cyclic polymer.

Automated summary

This article describes the redox-switching of a formazanate zinc catalyst in ring-opening polymerization of lactide. The catalytic activity can be modulated by reversible reduction/oxidation chemistry at a purely organic fragment, achieved by using a redox-active ligand bound to an inert metal ion (Zn2+). Kinetic and spectroscopic studies, along with mass spectrometry analysis of the catalysis mixture, provide insights into the nature of the active species and the initiation of lactide ring-opening polymerization. The mechanistic data highlights the crucial role of the redox-active ligand and offers an explanation for the formation of cyclic polymer.