Investigation of charge transfer complexes formed between 3,3′-dimethylbenzidine (o-toluidine) donor and DDQ, p-chloranil and TCNQ as π-acceptors

Charge-transfer (CT) complex of o -toluidine ( o -tol) with the π-acceptor tetrachloro- p -benzoquinone ( p -chloranil; CHL) has been synthesized and characterized, along with the products of the elimination reaction of o -toluidine ( o -tol) with 2,3-dichloro-5,6-dicyano- p -benzoquinone (DDQ) and 7,7,8,8-tetracyanoquinodimethane (TCNQ). Their properties and structures have been investigated using electronic absorption and IR spectroscopy as well as elemental analyses of the isolated compounds. The o -tol/ p -CHL CT complex is shown to consist of a CHL − radical anion and o -tol + radical cation. The formations of all three compounds result in the appearance of new UV-Vis spectral bands that peaked in intensity at a stoichiometric ratio of 1:1. 1 H-NMR and mass spectra were used to confirm the formation of the o -tol/DDQ and o -tol/TCNQ products. The new 7,8-dicyano-7′,8′- o -toluidilequino-dimethane and 2,3-dichloro-5-cyano-6- o -toluidil- p -benzoquinone products resulted from the rapid reaction of o -tol with TCNQ and DDQ, respectively. Thermogravimetric studies showed that the CT-complex decomposes in three steps whereas the new compounds decompose in a single step. Thermodynamic parameters were computed from the thermal decomposition data.