Frontier molecular orbital analysis of Cun-O2 reactivity

Frontier molecular orbital (FMO) theory coupled with density functional calculations has been applied to investigate the chemical reactivity of three key biomorganic Cu-n-O-2 complexes. the mononuclear end-on hydroperoxo-Cu(II). the side-on bridged mu-eta(2):eta(2)-O-2(2-) Cu(II)(2) dimer and the bis-mu-oxo Cu(III)(2) dimer. Two acceptor orbitals (sigma* and pi*) of each complex and two types of donating substrates (alpha-substrate. phosphine: pi-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 sigma*/sigma and pi*/pi pathways are found more reactive than the corresponding cross sigma*/pi and pi*/sigma pathways which have poor donor-acceptor orbital overlaps in the sterically constrained substrate access region. (C) 2002 Elsevier Science Inc. All rights reserved.