On the magnetic circular dichroism of aromatic carbonyl compounds

Abstract

The magnetic circular dichroism of the single‐ring aromatic compounds benzaldehyde, acetophenone, and phthalaldehyde and of the two‐ring compounds benzophenone, anthrone, 9,10‐anthraquinone, and 10‐methylene anthrone is reported. In each case the molecular symmetry is so low that only B terms contribute to the magnetic ellipticity. The magnitude of the magnetic ellipticity in the $\mathrm{n\pi *}$ absorption region is discussed in terms of vibronic and electronic intensification mechanisms. The MCD of the ππ* transition region of the single‐ring compounds is discussed in terms of a model which considers magnetic field mixing of the ¹L_b and ¹L_a benzene states alone. The MCD of the two‐ring compounds, other than benzophenone, reveal ππ* transitions which are not observed in either absorption or polarized phosphorescence excitation spectra.