Issue:

SCSCC6, Volume VII, No. 4

Section:

Volume VII, No. 4 (2006)

Abstract:

The symmetric viologenes are bi-quaternary salts of 4,4’- bipyridil which may be obtained through nucleofile substitution (SN2) at nitrogen atoms with reactive halogenated derivates, such as a-halogenoesters and a-halogeno-ketones. It is known that the viologenes present three oxidation states: Viologen+2, Viologen+ and Viologen0, each of them having a certain color, and specific magnetic, electrical, vibrational and spectral properties. The bipyridinium cation (Viologen2+) is a stable state that may be transformed into Viologen+ or Viologen0 through a redox reactions activated by visible radiation. These redox processes could be reversible or not, depending on the nature of the viologen, of the electrolytic support, of the solvent and of the operating conditions. The complexity of these transformations may be clearly evidenced through cyclic voltammetry (CV). Our studies have been performed in 0.1M KCl aqueous solutions, with glassy carbon electrode. We have concluded that the CV signals given by viologenes synthesized starting from a-halogéno-esters are the most important. We can affirm that the electrochemical processes corresponding to these types of viologenes take place at a higher rate than other viologenes. The study of the redox properties allowed us to explain the behavior of different viologenes under irradiation. The viologenes have been introduced in a poly (vinylic alcohol) matrix, and the electronic absorption spectra modifications under UV radiations have been recorded. The specific behavior of each type of viologen has been studied.

Keywords:

viologen, cyclic voltametry, UV radiation.

Code [ID]:

CSCC6200607V04S01A0017 [0001595]

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