ELECTRONIC STRUCTURES OF TRIS(ACETYLACETONATO) COMPLEXES OF IRON-SERIES TRANSITION-METAL IONS .2. COMPLEXES CONTAINING PARAMAGNETIC METAL IONS

The theoretical method developed in Paper I is extensively applied to the tris(acetylacetonato) complexes containing paramagnetic metal ions such as Cr3+, Fe3+, and Ti3+. The results show that the present theoretical treatment is very useful in explaining the electronic structures and electronic absorption spectra of these complexes. Particularly the following two points may be emphasized: (1) Originally forbidden singlet-triplet π→π* transitions in the ligand are intensified by the mixing of the singlet and triplet states of the ligand through the transfer of the metal unpaired electron to the ligand π-electron system. This fact is shown to be important in explaining the electronic spectra of the Cr(acac)3 and Fe(acac)3 complexes containing paramagnetic metal ions. (2) Ti(acac)2 is shown to be peculiar because of the degeneracy of its ground configurations which is released by the configuration interaction. The band due to the transition between the split ground configurations is predicted to appear in the infrared region. Moreover, the transitions to triplet excited states in the ligand are shown to be intensified through the mixings with the interligand charge-transfer transitions and with some doubly excited transitions.