SOLVENT EFFECT ON THE ELECTRONIC SPECTRAL CHARACTERISTICS OF ACRIDINE-DYES

Visible electronic spectral characteristics of different concentration s of acridine orange and acridine hydrochloride in a number of organic solvents of different propreties and in water have been investigated. It is deduced that the spectral characteristics of Acr.0 (HL+) are la rgely dependent on both dye concentration and the nature of the solven t employed. Thus, under the influence of the basicity of dipolar aprot ic solvents (DMF, DMSO), the Acr.0 in very dilute solutions exists mai nly in the neutral deprotonated form (HL+ + S reversible HS+ + L). Fur ther it is ascertained that the polarizability of the solvent also pla ys an important role in determining the magnitude of the ionization pr ocess. On the other hand, in the solvents ethanol, AN and dioxane as w ell as in H-2(0), this compound exists mainly in the protonated form ( HL+) even at very low concentration. Moreover, it is concluded that Ac r.HCl in its dilute solutions in the various solvents exists mainly in the non-protonated form, i.e. it dissociates completely to the neutra l form (HL+ + S --> L HS+).