Molecular-orbital calculation of the electronic spectra of salicylalkylimines

MO methods in the Hückel approximation are used to derive the bond orders, electron-density distributions, dipole moments, and frequencies and strengths of the electronic transitions. The assignment of the absorption bands (on the basis of the energy and intensity results) leaves no doubt that the bands near 400 m, whose intensity is very much dependent on the solvent, are due to n transitions. The electron densities and bond orders for the ground state and for the first two excited states, as well as for the n₁ transition, show that the molecules have a tendency to adopt quinoid structures on excitation. The calculated dipole moment for salicylalmethylimine agrees well with measured values for this class of compound.