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

Redox-switching of a formazanate zinc catalyst in ring-opening polymerization (ROP) of lactide is described. Using a redox-active ligand bound to an inert metal ion (Zn2+) allows modulation of the catalytic activity by reversible reduction/oxidation chemistry at a purely organic fragment. A combination of kinetic and spectroscopic studies, together with mass spectrometry of the catalysis mixture, provides insight in the nature of the active species and the initiation of lactide ring-opening polymerization. The mechanistic data highlight the key role of the redox-active ligand and provide a rationale for the formation of cyclic polymer.本文报道了丙交酯（lactide）开环聚合（ring-opening polymerization, ROP）体系中甲臜合锌催化剂（formazanate zinc catalyst）的氧化还原切换行为。通过将氧化还原活性配体与惰性金属离子Zn²+结合，可依托纯有机片段处的可逆还原/氧化反应实现催化活性的调控。结合动力学与光谱学研究，以及催化反应混合物的质谱分析，可深入解析活性物种的本质与丙交酯开环聚合的引发机制。该机理数据凸显了氧化还原活性配体的关键作用，并为环状聚合物的生成提供了理论依据。