THE EFFECT OF LIGHT ON THE THERMODYNAMIC-EQUILIBRIUM IN THE FORMATIONOF THE COMPLEX BETWEEN VIOLOGEN AND THE FERROCYANIDE ION

The formation of the complex between N,N'-dibutyl-4,4'-dipyridilium di bromide and potassium ferrocyanide was studied in aqueous solutions. T he charge transfer band was observed and the composition of the comple x between the dipyridilium dication and the ferrocyanide ion (1 : 1) w as established. The irradiation (lambda less than or equal to 350 nm) of deaerated solutions in the absorption region of individual componen ts results in a shift of the thermodynamic equilibrium towards complex formation via the intermediate formation of an exciplex. Since the ab sorption maximum of the complex is located in the visible region (lamb da = 528 nm), its reversible formation and decomposition are accompani ed by reversible coloring of the solution, i.e., the system is photoch romic.