Synthesis and characterization of copper complexes with tripodal ligands bearing amino acid groups

Abstract

The tripodal ligand (2-aminoethyl)bis(2-pyridylmethyl)amine (uns-penp), known for its Cu/O2 intermediates, was modified at one side arm by a selection of amino acids. With L-Tyrosine (Tyr), L-Histidine (His) and L-Lysine (Lys) it was possible to introduce chirality into the tripodal ligand system and to investigate the corresponding copper(I) complexes [Cu{L-His(BPh3)uns-penp}], [Cu(L-Lys)uns-penp]OTf and [Cu(L-Tyr)uns-penp]OTf. [Cu{L-His(BPh3)uns-penp}] could be structurally characterized and represents the first example of a copper(I) complex with a coordinated imidazole ring of the histidine ligand. Furthermore, these complexes demonstrated catalytic activity for the oxygenation of thioanisole with hydrogen peroxide as an oxidant.