Competitive complexation by ligand and solvent: Polarographic characterization of ATRP catalyst polyamine-copper complexes in acetonitrile plus water mixed solvents

摘要

In the Atom Transfer Radical Polymerization ( ATRP) technique, the suggested polymerization scheme is pivoted by a metal complex acting as a redox catalyst able to coordinate with the incipient radicals. The development of an a priori criterion of choice of the best ( complex + solvent) combination is one of the current topics in this field. In this context we performed polarographic investigations on copper complexes with multidentate amino ligands (TMEDA and Me6TREN, plus acetonitrile as a reference) in water and in water + acetonitrile mixed solvents. In the latter case we took into account the competition between the co-solvent acetonitrile [ a weaker ligand, but concentrated, selectively stabilizing Cu(I)], and the polyamine [ a stronger ligand, but diluted, preferentially stabilizing Cu(II)], achieving further stabilization of the complexed copper, with a narrow potential range of stability as Cu( I), which is modulated through the acetonitrile/polyamine ratio. An interpretative scheme is presented.