Spectroscopic investigation of the solvatochromic behavior of a new synthesized non symmetric viologen dye: Study of the solvent-solute interactions

This work deals with the design, synthesis, and characterization of a new solvatochromic dye. The intense solvatochromic behavior of this new synthesized non symmetric viologen was investigated using UV-Vis spectrophotometry. A further purpose was the study of the interactions between the solvent and solute molecules responsible for the solvatochromism. Several protic and aprotic solvents were used, and the resulting absorption maxima wavenumbers obtained via UV-Vis spectrophotometry, were correlated with the solvent polarity parameters, E-T(30) (Dimroth-Reichardt solvent polarity parameter) and the Gutmann's donor number (DN) using the biparametric model introduced by Krygowski and Fawcett. The analysis of the relative contribution of each parameter has clearly shown that the dominating interaction responsible for the solvatochromic behavior observed is the proton donation by the solute molecules to the solvent molecules, the latter acting as a Lewis bases. This is an interaction which can be described by DN. Additionally, the good correlation with the Kamlet-Taft parameter beta is in good agreement.