Multiple and sequential charge transfer interactions occurring in situ: A redox reaction of thiazolidine-2-thione with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone

Abstract

Interaction of thiazolidine-2-thione (T2T) as an electron donor with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as an electron π-acceptor has been studied. Electronic absorption spectra of the system T2T–DDQ in several organic solvents of different polarities have been measured. A charge transfer (CT) complexation has occurred between T2T and DDQ. This CT interaction has led to a redox reaction in which T2T has been oxidized to the corresponding dehydrogenated T2T (T2T-2 H), meanwhile DDQ has been fully reduced to the corresponding hydroquinone (DDQH 2). However, the two new species, resulting in situ, have been interacted, whereas a CT complex having the formula (T2T-2 H·DDQH 2) has occurred. IR, 1H NMR and mass spectra were used for ascertaining the structural formula of the synthesized CT complex. Formation constants ( K CT), molar absorption coefficients ( ɛ CT) and thermodynamic properties of this CT interaction in various organic solvents were determined and discussed. The obtained K CT and ɛ CT values have indicated that T2T-2 H is a weak CT donor, whereas the formed CT complex has a low stability and it is classified as a contact-type CT complex.