Speciation Analysis in Iron-Mediated ATRP Studied via FT-Near-IR and Mössbauer Spectroscopy

Abstract

The structure of [FeIIBru(Solv)v] and [FeIIIBrw(Solv)x] complexes to be used as catalysts for atom-transfer radical polymerization (ATRP) was determined in several solvents via FT-near-IR in conjunction with Mössbauer spectroscopy. The relative amounts of these complexes are sensitive to both the type of solvent and pressure. The [FeIIBr3(Solv)]−/[FeIIIBr4]− redox pair essentially governs the ATRP equilibrium. The properties of these complexes are correlated with the measured ATRP activation rate coefficients, kact, for monomer-free model systems. In weakly polar solvents such as esters, ketones, and substituted benzenes, kact was found to be larger than in strongly polar solvents, such as NMP, MeCN, and DMF, due to stabilization of the [FeIIBr3(Solv)]− complex.