Synthesis and Characterization of the Most Active Copper ATRP Catalyst Based on Tris[(4-dimethylaminopyridyl)methyl]amine

• Published in: Journal of the American Chemical Society Vol. 140; no. 4; pp. 1525 - 1534
• Main Authors: Ribelli, Thomas G., Fantin, Marco, Daran, Jean-Claude, Augustine, Kyle F., Poli, Rinaldo, Matyjaszewski, Krzysztof
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 31.01.2018
• Subjects: Catalysis; Chemical Sciences; Coordination chemistry; Polymers
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.7b12180

The tris­[(4-dimethylaminopyridyl)­methyl]­amine (TPMANMe2) as a ligand for copper-catalyzed atom transfer radical polymerization (ATRP) is reported. In solution, the [CuI(TPMANMe2)­Br] complex shows fluxionality by variable-temperature NMR, indicating rapid ligand exchange. In the solid state, the [CuII(TPMANMe2)­Br]­[Br] complex exhibits a slightly distorted trigonal bipyramidal geometry (τ = 0.89). The UV–vis spectrum of [CuII(TPMANMe2)­Br]+ salts is similar to those of other pyridine-based ATRP catalysts. Electrochemical studies of [Cu­(TPMANMe2)]2+ and [Cu­(TPMANMe2)­Br]+ showed highly negative redox potentials (E 1/2 = −302 and −554 mV vs SCE, respectively), suggesting unprecedented ATRP catalytic activity. Cyclic voltammetry (CV) in the presence of methyl 2-bromopropionate (MBrP; acrylate mimic) was used to determine activation rate constant k a = 1.1 × 106 M–1 s–1, confirming the extremely high catalyst reactivity. In the presence of the more active ethyl α-bromoisobutyrate (EBiB; methacrylate mimic), total catalysis was observed and an activation rate constant k a = 7.2 × 106 M–1 s–1 was calculated with values of K ATRP ≈ 1. ATRP of methyl acrylate showed a well-controlled polymerization using as little as 10 ppm of catalyst relative to monomer, while side reactions such as CuI-catalyzed radical termination (CRT) could be suppressed due to the low concentration of L/CuI at a steady state.