Effects of solvent and substituent on the electronic absorption spectra of some substituted Schiff bases: A chemometrics study

A series of Schiff bases were studied for their delicate changes in absorption electronic spectra by changing substituents and solvents. UV/vis absorbance spectra of Schiff base derivatives of different substituents ranging from electron withdrawing to electron donating (Br, CF3, Cl, CN, CO2H, F, Me, NO2, OH, OMe, H) were studied in different solvents (acetonitrile, chloroform, cyclohexane, dioxane, dimethylsulfoxide and methanol). Linear relationships were established to investigate the effect of solute structure and solvatochromic parameters of solvents on the absorbance spectra. Meaningful chemical factors and then regression models were provided utilizing factor analysis (FA) and multiple linear regression (MLR). It was found that the frequency of maximum absorbance was mainly controlled by the solvent's dipolarity/polarizability. The λmax of the ortho-nitro derivative represented the largest dependency on solvents’ polarity/polarizability so that it can be used as a solvatochromic probe.

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► Solvent and substituent effects on the λmax of some Schiff bases were investigated.
► Factor analysis and multiple linear regression were employed and compared.
► Factor analysis resulted in more interpretable models.
► Solvent polarity/polarizability was found to exert the most significant effect on λmax.
► The λmax of ortho-NO2 derivative represented the most sensitivity to solvent polarity.