Effect of substituent on the UV-Vis spectra: an extension from disubstituted to multi-substituted benzylideneanilines

For studying the substituent effects on the νmax of substituted benzylideneanilines (XBAYs) systematically, 12 samples of 3,3′-disubstituted XBAYs and 52 samples of multi-substituted XBAYs were synthesized, and the substituent effects on their νmax were investigated in this paper. A modified regression equation quantifying the νmax of 4,4′/4,3′/3,4′/3,3′-disubstituted and multi-substituted XBAYs (shown as Eq. 3) was obtained. The results showed that the substituent effects on the νmax of 3,3′-substituted and multi-substituted XBAYs became more complicated. In Eq. 3, the contributions of the meta-parameters to the νmax of XBAYs were different from those of the corresponding para-parameters. For the substituent cross-interaction effects, there is no difference whatever the substituents are at meta-position or para-position. Compared with Eq. 1, Eq. 3 obtained in this paper has a wider application and more accuracy in quantifying the νmax of substituted XBAYs. Copyright © 2016 John Wiley & Sons, Ltd.