Changes induced by solvent polarity in electronic absorption spectra of some nucleic acid constituents

The electronic absorption spectra of some biologically active nucleic acid constituents in various solvents of different polarities and with variable physical properties have been studied at room temperature. These compounds are of two categories (pyrimidines: [barbital; 5,5′-diethyl-barbituric acid], [SBA; 4,6-dihydroxy-2-mercapto-pyrimidin], [NBA; 5-nitro-2,4,6(1H,3H,5H)-pyrimidine trione] and [TU; 2,3-dihydro-2-thioxo-pyrimidin-4(1H)-one]) and (purines: [adenine; 6-amino purine] and [guanine; 2-amino-6-hydroxy purine]). The solvent effects on the wavenumbers of the absorption band maxima (ύmax) were discussed using the following solvent parameters: refractive index (n), dielectric constant (D) and empirical Kamlet–Taft solvent parameters, π* (dipolarity/polarizability), α (hydrogen bond donating capacity) and β (hydrogen bond accepting ability) using multiple linear regression method (MLR). The solute–solvent interactions were determined on the basis of multilinear solvation energy relationships concept. The data of the studied molecules are affected by both non-specific and specific solute–solvent interactions. The solvatochromic behavior was explained.