Studies on the charge-transfer complexes of <i>o</i>-chloranil with a series of methylbenzenes

Abstract

Equilibria for the formation of molecular electron-donor-acceptor (EDA) complexes of a series of methylbenzenes with <em>o</em>-chloranil have been studied in CCl₄ medium. The charge transfer (CT) transition energies are found to change systematically with change in the number and positions of methyl groups in the donor molecule (methylbenzenes). This is well interpreted by the simple PMO theory. Semiempirical AM1 and PM3 calculations have been done on the EDA complexes considering them as supermolecules. The lowest S₁&larr;S₀ transition is clearly shown to be associated with the transfer of one electron from the donor to the acceptor moiety in the excited state, while practically no change transfer occurs in the corresponding ground state. The theoretical CT transition energies follow the same trend as that observed from experimental values.