<i>p</i>‐Substituted Tris(2‐pyridylmethyl)amines as Ligands for Highly Active ATRP Catalysts: Facile Synthesis and Characterization
Alan E. Enciso, Francesca Lorandi, Arshad Mehmood, Marco Fantin, Grzegorz Szczepaniak, Benjamin G. Janesko, Krzysztof Matyjaszewski
Abstract
Abstract A facile and efficient two‐step synthesis of p ‐substituted tris(2‐pyridylmethyl)amine (TPMA) ligands to form Cu complexes with the highest activity to date in atom transfer radical polymerization (ATRP) is presented. In the divergent synthesis, p ‐Cl substituents in tris(4‐chloro‐2‐pyridylmethyl)amine (TPMA 3Cl ) were replaced in one step and high yield by electron‐donating cyclic amines (pyrrolidine (TPMA PYR ), piperidine (TPMA PIP ), and morpholine (TPMA MOR )) by nucleophilic aromatic substitution. The [Cu II (TPMA NR2 )Br] + complexes exhibited larger energy gaps between frontier molecular orbitals and >0.2 V more negative reduction potentials than [Cu II (TPMA)Br] + , indicating >3 orders of magnitude higher ATRP activity. [Cu I (TPMA PYR )] + exhibited the highest reported activity for Br‐capped acrylate chain ends in DMF, and moderate activity toward C−F bonds at room temperature. ATRP of n ‐butyl acrylate using only 10–25 part per million loadings of [Cu II (TPMA NR2 )Br] + exhibited excellent control.