Roy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6323, United States.
School of Chemistry and Biological Engineering, University of Science and Technology Beijing, Beijing 100083, China.
Biomacromolecules. 2020 May 11;21(5):1902-1919. doi: 10.1021/acs.biomac.9b01765. Epub 2020 Feb 7.
A mixed-ligand effect was observed for mixtures of tris(2-dimethylaminoethyl)amine (Me-TREN) with tris(2-aminoethyl)amine (TREN) ligands during Cu(0) wire-catalyzed, single-electron transfer-living radical polymerization (SET-LRP) of methyl acrylate (MA) initiated with bis(2-bromopropionyl)ethane (BPE) in DMSO. The external order of reaction of SET-LRP both in the presence of Me-TREN, TREN and of the mixed-ligand Me-TREN/TREN, in DMSO, demonstrated a catalytic activity for DMSO similar to that reported in the presence of Cu(0) powder. The catalytic activity of DMSO, with close to 100% chain-end functionality, facilitates the much less expensive TREN to act as a very efficient ligand that is competitive with Me-TREN and with the mixed-ligand and revitalizes TREN into an excellent ligand. The highest activity of the mixed-ligand at 1/1 ratio between ligands suggests that in addition to a fast exchange between these two ligands, a new single dynamic ligand stabilized by hydrogen-bonding, may generate these results.
在二甲基氨基乙基三乙胺(Me-TREN)与三(2-氨基乙基)胺(TREN)配体的混合物存在下，观察到在双(2-溴代丙酰基)乙烷(BPE)引发的甲基丙烯酸甲酯(MA)的铜(0)线催化、单电子转移-自由基聚合(SET-LRP)中存在混合配体 Me-TREN/TREN 时，混合配体具有混合配体效应。在 DMSO 中，SET-LRP 的外部反应级数既表现出与 Me-TREN 存在时相似的催化活性，也表现出与 TREN 存在时相似的催化活性，表明 DMSO 的催化活性类似于在 Cu(0)粉末存在下的催化活性。DMSO 的催化活性接近 100%的链端官能度，使得相对便宜的 TREN 能够作为一种非常有效的配体，与 Me-TREN 和混合配体竞争，并使 TREN 重新成为一种优良的配体。在配体 1:1 比例下混合配体的最高活性表明，除了这两种配体之间的快速交换外，氢键稳定的新的单一动态配体可能产生这些结果。
