SEMIEMPIRICAL MO-CALCULATIONS ON THE ELECTRONIC-SPECTRA OF AZIDO SUBSTITUTED PARA-BENZOQUINONES

The electronic spectra of azido substituted p-benzoquinone (PBQ) have been recorded. The energy levels have also been calculated by means of PPP-CI method and on the basis of this assignments are made for the observed absorption bands. The results show that the Tetraazido p-benzoquinone has an n-π* transition at 570 nm and three allowed π-π* transitions at 380, 278 and 215 nm. The 2,5-diazido-3,6-dichloro p-benzoquinone has an n-π* transition at 430 nm and two allowed π-π* transitions at 335 and 210 nm. Replacement of the chlorine atoms by -OCH3 and -NH2 groups does not alter the spectra appreciably. Inversion of symmetry is shown to result in an allowed transition from HOMO to LVMO in chloranil whereas it is forbidden in the case of azidanil. A comparison of the EHOMO and ELVMO with those of chloranil suggests that the azido substituted quinones are also efficient electron acceptors. © 1979.