金属萘酞菁(MNCs)被证明是激活光诱导电子转移可逆加成-断裂链转移(PET-RAFT)聚合的有效光催化剂,能够在近红外(λ=780 nm)光下实现(甲基)丙烯酸酯的良好控制聚合。由于三硫代碳酸酯RAFT试剂的氧化还原电位低于先前探索的光催化剂,因此其活化表现出独特的选择性,这取决于R基团的性质。具体而言,MNCs能够激活第三R族三硫代碳酸酯,而未观察到具有第二R族的三硫代碳酸酯的激活。
综合密度泛函理论计算和实验研究揭示了PET-RAFT机制控制因素的新机理,并解释了MNCs对三硫代碳酸三酯的独特选择性。有趣的是,通过适度提高反应温度(即~-15℃),克服了阻碍具有二级R基团的三硫代碳酸酯光活化的能垒,使其能够成功活化。
附:英文原文
Title: Selective Photoactivation of Trithiocarbonates Mediated by Metal Naphthalocyanines and Overcoming Activation Barriers Using Thermal Energy
Author: Zilong Wu, Kenward Jung, Chenyu Wu, Gervase Ng, Lei Wang, Jingquan Liu, Cyrille Boyer
Issue&Volume: January 10, 2022
Abstract: Metal naphthalocyanines (MNcs) were demonstrated to be efficient photocatalysts to activate photoinduced electron-transfer reversible addition–fragmentation chain transfer (PET-RAFT) polymerization, enabling well-controlled polymerization of (meth)acrylates under near-infrared (λ = 780 nm) light. Owing to their lower redox potential compared to previously explored photocatalysts, the activation of trithiocarbonate RAFT agents exhibited a unique selectivity that was dependent on the nature of the R group. Specifically, MNcs were capable in activating tertiary R group trithiocarbonates, whereas no activation of the trithiocarbonate possessing a secondary R group was observed. The combination of density functional theory calculations and experimental studies have revealed new mechanistic insights into the factors governing a PET-RAFT mechanism and explained this unique selectivity of MNcs toward tertiary carbon trithiocarbonates. Interestingly, by increasing the reaction temperature moderately (i.e., ~15 °C), the energy barrier prohibiting the photoactivation of the trithiocarbonate with a secondary R group was overcome, enabling their successful activation.
DOI: 10.1021/jacs.1c11700
Source: https://pubs.acs.org/doi/10.1021/jacs.1c11700
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