Correlation of the ionization potentials of pseudo-aromatic metal complexes with hammett's substituent constants—II: Chromium acetylacetonates

The first ionization potentials, E_I, of substituted chromium(III) acetylacetonates are found to be a linear function of the sum of Hammett's σ_m and σ_p constants for substituents in various positions of the pseudo-aromatic rings, relative to the Cr atom. The equation for the regression is E_I = 7·40 + 0·380Σσ ± 0·02 eV, where 7·40 eV is the interpolated value for the tris-Cr chelate of malonaldehyde, and the slope of the correlation line is 0·380. From the value of the slope and other considerations, it is deduced that the ejected electron is an unpaired d_xyCr electron in at_2gMO.