The electronic absorption spectra of N-sulfinylaniline and some of its derivatives were investigated using different solvents. The spectral behavior of the molecules indicated their planarity and that the NSO group is a strong electron acceptor. All the observed bands correspond to delocalized π → π* transitions; n → π* transition were not observed as discrete bands. Ab initio molecular orbital calculations were performed using four different basis sets. The results showed that the NSO group is nonlinear, the molecules studied are planar, and the syn conformer is more stable than the anti conformer. Keywords: N-sulfinylanilines, spectra and theoretical treatment.

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The electronic absorption spectra of m‐ and p‐chloro, m‐ and p‐nitro‐N‐sulfinylanilines were investigated using different solvents. The spectral behavior indicates the planarity of the studied molecules and that the sulfinylamino (NSO) group acts as an electron acceptor. All the observed bands in the spectra correspond to delocalized π→π* transitions, and no discrete bands were observed for n→π* transitions. Ab initio molecular orbital calculations were performed, using split‐valence basis sets, on the ground state of the studied molecules and the equilibrium geometric parameters were calculated. The results indicate that the NSO group is nonlinear, the studied molecules are planar, and the syn conformer is more stable than the anti one. AMl‐SCF procedure was used to calculate the wave functions as well as the energies of the excited states of the studied molecules, the correspondence between the calculated transition energies and the experimental ones is satisfactory. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 72: 1–13, 1999