H2O2 reactivity of a dinuclear copper(II) complex incorporating a constrained binucleating polyaminopyridyl ligand and a phosphodiester coligand

Abstract

A dinuclear copper(II) complex [Cu2(PD)(DPP−)2](ClO4)2 (1) incorporating a constrained binucleating hexadenate ligand, PD (1,3-bis{bis[(2-pyridyl)ethyl]amino}benzene), and coligand, DPP− (diphenylphosphate) was synthesized and characterized, with a specific outlook towards evaluating spectroscopic and H2O2 reactivity relevant to the active-sites of noncoupled dinuclear copper enzymes, DβM and PHM. In solution, complex 1 exhibits a broad 1H NMR in the range −25 to +60ppm and has a solution magnetic moment (μ) of ∼2.0 B.M./Cu(II), typical of a noninteracting dicopper(II) center. The room temperature H2O2 reactivity of 1 monitored by UV–Vis spectroscopy reveals the formation of a copper(II)–dioxygen intermediate 1a, which in turn leading to a arene ligand hydroxylation (PD-O−) and thus provide a new doubly-bridged dicopper(II) complex, [Cu2(PD-O−)(DPP−)](ClO4)2 (2). The dioxygen intermediate produces OPPh3 on treatment with PPh3 revealing it is an electrophilic hydroperoxide oxidant. Solution magnetic moment of 1.61 B.M./Cu(II) indicates the product complex 2 is a moderately interacting dicopper(II) center and its 1H NMR spans between −20 and +180ppm. A comparison of the optical absorption features of complex 1a with related dinuclear hydroperoxo-copper(II) complexes is discussed.