MO LCAO calculations of the electronic spectra of the anions of 1,3-diketones with substituents at positions 1 and 3

The MO LCAO method is applied in the Huckel approximation to interpret the electronic spectra of the anions of 1,3-diketones having phenyl groups or double bonds in positions 1 and/or 3, as well as 1 and 2. It is found that one or two phenyl groups or double bonds in positions 1 and/or 3 produce a bathochromic shift in the strong N→V1 transition and the occurrence of a new fairly strong C6H5→V1 or C=C→V1 transition in the short-wave region. Simultaneous substituents in position 1 and 2 or 3 produce rather complex spectra, which are rather difficult to interpret by the simple MO LCAO method.