Molecular orbital calculations of magnetic circular dichroism spectra: a benzene-indole sequence.

The magnetic circular dichroism of benzene and indole derivatives was measured down to 190 nM. The following pairs of molecules have magnetic circular dichroisms of the opposite sign in the B(2u) absorption region: aniline and benzonitrile, indene and indoline, indole and 4-aminoindole, and 4-aminoindole and 5-aminoindole. The sign and magnitude of the magnetic circular dichroisms observed are in good agreement with those calculated by the semiempirical self-consistent field with configuration interaction Pariser-Parr-Pople method with incorporation of variable pi-electronegativity and sigma-polarization. The energy dominator in the magnetic rotational strength expression serves to limit the important contributions to a few terms only.