THE USE OF OPTICAL ELECTRONEGATIVITIES TO ASSIGN ELECTRONIC-SPECTRA OF SEMIQUINONE COMPLEXES

Semiquinone complexes of a wide range of transition metals show ligand to metal charge-transfer transitions in their electronic spectra. Using the optical electronegativity approach we have shown that these assignments are consistent with one another. The optical electronegativity of 3,5-di-t-butylsemiquinone is found to vary from 1.2 to 1.5, depending on the metal ion. In cases where the optical electronegativity appears to lie outside these limits, alternative assignments are discussed. Optical electronegativities for 2,2′-bipyridine, 2,2' -bipyrazine and 2-picolinic acid N-oxide are also reported. © 1990.