Fine tuning of structure and reactivity of copper complexes using pyridylalkylamine ligands - Active site models for copper proteins

Abstract

Ligand effects on the structure and reactivity of copper complexes have been studied systematically by using several types of pyridylalkylamine ligands. Special attention has been focused on the dioxygen activation chemistry by copper (I) complexes aiming at understanding the catalytic mechanism of copper oxidases and copper monooxygenases. Different types of copper-dioxygen complexes such as a (μ-η2: η2-peroxo)dicopper(II) complex, a (μ-η1 : η2-peroxo)dicopper(II) complex, a bis(μ-oxo)dicopper (III) complex, and a mixed-valent bis(μ3-oxo)tricopper (II, II, III) complex have been assessed by the reaction of O2 and copper (I) complexes supported by a series of pyridylalkylamine ligands. Reactivity of the generated active oxygen complexes has been also investigated in detail to get insights into the catalytic mechanism of copper enzymes such as tyrosinase and particulate methane monooxygenase. Mononuclear copper (II)-hydroperoxo complexes as well as bis(μ-oxo) dinickel(III) complexes have been also obtained using the same series of pyridylalkylamine ligands. Furthermore, redox interconversion between disulfide (RS-SR) and thiolate (2RS-) has been finely controlled by the copper complexes of pyridylalkylamine derivatives. Ligand effects on the respective reactions have been discussed based on the structures and physicochemical properties of the complexes.