Solvent effect on electronic absorption spectra of some 2-aminobenzimidazoles

The effect of protic and aprotic solvents on electronic apsorption spectra of 1-(3-X-benzil)-2-aminobenzimidazoles (X=CH3;OCH3; Cl) was examined. UV-apsorption spectra (200-400 nm) were recorded in five protic and four aprotic solvents. Batochromic shift of absorption maxima, λmax, occurs from the solvent with the highest proton-donor ability to the proton acceptor solvent (from water to DMSO). Positions of absortion maxima in various solvents are in correlation with the dielectric constant of the solvent. In order to explain the obtained results, the ultraviolet absorption frequences of the electronic transitions of the compounds were correlated using a total solvatochromic equation of the form: νmax = ν0 + s¶* + aα + bβ, where¶* is the measure of solvent polarity. Prepresents the scale of solvent hydrogen bond acceptor basicities and β represents the scale of solvent hydrogen bond donor acidities. Correlation of spectroscopic data was carried out by means of multiple linear regression analysis