Donor-acceptor interaction in two-level-reduced molecular systems Original Research Article

The validity of the two-state approximation and its relationship with the donor and acceptor states in electron transfer processes is discussed. The formalism of Greenʹs function is employed with a semiempirical AM1 Hamiltonian. Symmetric molecules containing two nitrogens are used to investigate the behavior of the two lone pairs acting as donor and acceptor states. Zinc atoms, bonded to nitrogen in some of these molecules, are also considered to investigate electron transfer in systems having more localized donor and acceptor states. The results indicate that, for the class of compounds used, the nitrogen lone pairs do not fulfill the requirements to act as localized donor and acceptor states. However, ‘good’ donor and acceptor states may be identified in the 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 describing the transition state of the systems in an electron transfer process.