Frontier molecular orbital analysis of Cun–O2 reactivity

Abstract

Frontier molecular orbital (FMO) theory coupled with density functional calculations has been applied to investigate the chemical reactivity of three key bioinorganic Cun–O2 complexes, the mononuclear end-on hydroperoxo-Cu(II), the side-on bridged μ–η2:η2–O22− Cu(II)2 dimer and the bis-μ-oxo Cu(III)2 dimer. Two acceptor orbitals (σ* and π*) of each complex and two types of donating substrates (σ-substrate, phosphine; π-substrate, alkylbenzene) are considered in the electrophilic attack mechanism. The angular dependences of different reaction pathways are determined using FMO theory and the angular overlap model. Including steric effects, the σ*/σ and π*/π pathways are found more reactive than the corresponding cross σ*/π and π*/σ pathways which have poor donor–acceptor orbital overlaps in the sterically constrained substrate access region.