DONOR-ACCEPTOR INTERACTION IN 2-LEVEL-REDUCED MOLECULAR-SYSTEMS

The validity of the two-state approximation and its relationship with the donor and acceptor states in electron transfer processes is discus sed. The formalism of Green's function is employed with a semiempirica l AM1 Hamiltonian. Symmetric molecules containing two nitrogens are us ed to investigate the behavior of the two lone pairs acting as donor a nd acceptor states. Zinc atoms, bonded to nitrogen in some of these mo lecules, are also considered to investigate electron transfer in syste ms having more localized donor and acceptor states. The results indica te that, for the class of compounds used, the nitrogen lone pairs do n ot fulfill the requirements to act as localized donor and acceptor sta tes. However, 'good' donor and acceptor states may be identified in th e Zinc atoms allowing to correct the prediction of the behavior of the bridge in mediating electron transfer interaction. The use of a self- consistent Hartree-Fock calculation was important for properly describ ing the transition state of the systems in an electron transfer proces s.