L.M.C. Vieira,^a A.M. Fonseca, ^a,*M.M.M. Raposo,^a G. Kirsch^b

^aDepartamento de Química, Universidade do Minho, Campus de Gualtar,

4710-057, Braga, Portugal.

^bLaboratoire d´Ingénierie Moléculaire et Biochimie Pharmacologique, Faculté de Sciences, Université de Metz, 57012 Metz, France.

Received 15 September 2003; Accepted in revised form 6 November 2003

This work reports on cyclic voltammetry and spectroscopic UV-Vis investigations of some pyridazine derivatives 1-8 in dimethylformamide. In the electrochemical study, monochlorinated pyridazines 2-8 exhibit two reductions but in the case of dichlorinated derivative 1 an additional wave is seen for the reduction of the second carbon-chloride bond. The electronic absorption spectra display an intramolecular charge transfer band π-π* in the UV region of which depend substantially on the nature of both donor and acceptor moieties. These results indicate the π-electron delocalization in the conjugated system.

Keywords: pyridazines; electrochemistry; electronic spectra; donor-π -bridge-acceptor systems.

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^*Corresponding author. E-mail address: amcf@quimica.uminho.pt (A.M. Fonseca).