The synthesis, spectral, electrical and magnetic properties of charge transfer materials of aromatic diamines namely benzidine (BEN) andρ-toluidine (O.TOL) with various acceptors such as iodine, 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), tetracyanoquinodimethane (TCNQ), andp-chloranil (p-CA) have been reported. These materials excepto-toluidine-chloranil complex have been found to be typical molecular semiconductors on the basis of temperature dependence on their electrical conductivity. They have low electrical conductivities and two thermal activation energies indicating mixed conductivity mechanism in which both the electrons and holes are charge carriers, one dominating over the other at different temperatures. The observation of the metal like electrical conductivity i.e. the increase of electrical conductivity with decreasing temperature in theo-toluidine-chloranil system is unique for this class of molecular electronic materials.

Mixed ionic and electronic conduction in charge transfer materials based on aromatic diamine electron donors (benzidine,o-tolidine (3,3′-dimethyl benzidine) andN,N′-diphenylbenzidine) with iodine in different mole ratios has been reported. The current-voltage and capacitance-voltage curves as a function of time and temperature have been obtained to determine the role of ionic conduction in electronic conductors based on charge transfer complexes. The compositional dependence of ionic transport numbers, diffusion parameters, ionic(σ_i) and electronic(σ_e) conductivities and thermal activation energies has been studied. Temperature and frequency dependence of AC impedance and related parameters have been studied to learn about the electrical conduction behaviour in these non-stoichiometric charge transfer materials. An electrochemical mechanism has been proposed to account for the ionic conduction in some of these complexes.