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

Abstract

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 C₂ symmetric proline-based pseudopeptide LH₂ (N,N′-(ethane-1,2-diyl)bis(pyrrolidine-2-carboxamide)), which is capable of supporting an [(L)Cu(III)]⁺ (3) intermediate in MeOH : CH₃CN (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 mCPBA and CAN. The newly generated [(L)Cu(III)]⁺ can promote hydrogen atom abstraction reactions with phenolic substrates.