Application of QSPR-MLR methodology to solvatochromic behavior of quinoline in binary solvent HBD/DMF mixtures

Quantitative Structure-Property Relationship methodology was applied successfully to experimental molar transition energies of quinoline, published before, in order to achieve a better understanding about the predominant quinoline-solvent interactions. Internal and external model validations were performed showing a high predictive ability of the selected multiple linear relationship. The wavenumbers of maximum absorbance of five dyes UV-vis spectra in methanol/dimethylformamide, propan-1-ol/dimethylformamide and pentan-1-ol/dimethylformamide mixtures, and in pure solvents, were experimentally determined, at 298.15 K, with the aim of calculating the Kamlet and Taft solvatochromic parameters (π⁎, α and β). Refractive indices of those mixtures were also calculated, to evaluate the Lorentz-Lorenz function values, g(nD). The chosen solvatochromic response model of quinoline suggests the dominance of the dipolarity/polarizability (π⁎) and the basicity (β) parameters followed by the ETN one (predominantly a measure of the solvent acidity). The former parameter contributes to a higher stabilization of the ground state and the two latter ones to a greater stabilization of the quinoline Frank-Condon excited state.