Spectroscopic characterization and the reactivity of a high valent (L)Cu(III) species supported by a proline-based pseudopeptide.

Inspired by copper-based metalloenzymes, we aim to incorporate amino acids into our ligands to facilitate active copper intermediates that serve as functional and structural models for these enzymes. Herein, we report the synthesis of a Cu(II) complex with a C 2 symmetric proline-based pseudopeptide LH 2 ( N , N '-(ethane-1,2-diyl)bis(pyrrolidine-2-carboxamide)), which is capable of supporting an [(L)Cu(III)] + (3) intermediate in MeOH : CH 3 CN (1 : 20) at -30 °C. From comparative studies with the pyridine analog Cu(II) complex, it was demonstrated that the incorporation of amino acid in the ligand framework decreased the Cu(III)/Cu(II) redox potential significantly to react readily with m CPBA and CAN. The newly generated [(L)Cu(III)] + can promote hydrogen atom abstraction reactions with phenolic substrates.