The acid-base properties of 4,4′-dithiodipyridine.

Despite the importance of the 4,4'-dithiodipgridine as an electrode modifier on the protein electrochemical studies and as a remarkable bridged-ligand on conducting electronic density in binuclear mixed valence complexes, there is no data available in the literature concerning acid-base behavior of this compound. Aiming to afford such information we undertook the ionization equilibrium study of this ligand. Although two acid species, DTDPH+ and DTDPH2+ have been detected in solution, only the diacid-form was possible to be isolated as a perclorate salt DTDPH2(ClO4)(2). The ionization constants for the two step equilibrium processes (pK(ai)=2.70 and pK(a2)=4.80) were determined by using the spectrophotometric technique and aqueous solutions of CF3COONa, mu=0,1 mol.L-1.