Interaction of thiazolidine-2-thione with 2,3,5,6-tetrabromo-1,4-benzoquinone: a set of sequential interactions involving redox and substitution reactions after an initial charge transfer complexation.

Interaction between thiazolidine-2-thione (T2T) as an electron donor and 2,3,5,6-tetrabromo-1,4-benzoquinone (p-bromanil, BRL) as a π-electron acceptor has been studied by using several spectral techniques, viz. UV/visible, IR, (1)H NMR and Mass spectra. A substitution reaction has been occurred after an initial formation of a CT complex, meanwhile a redox reaction has been occurred, in situ, too in which the interacting donor (T2T) has been oxidized to the corresponding thiazole. Thus, the stoichiometric ratio of this interaction has been found to be 2:1, T2T:BRL. However, the most interesting finding is that unexpectedly neither the SH group of the thiol form nor the NH group of the thione form of the T2T has shared in the substitution reaction with BRL. This finding has been confirmed by the different applied spectral tools, whereas a plausible reaction pathway has been illustrated and discussed.