Effect of Pressure on the Electronic Structure of Twelve Ferric β-Diketone Complexes

Abstract

The effect of pressure to 180 kbars on the electronic structure of 12 ferric β-diketone complexes has been measured by means of Mössbauer resonance and optical absorption. The systematic variation of the electron donor and acceptor properties of the ligands permits a more detailed interpretation of the results than in previous studies. These properties are correlated with the isomer shift of the Fe(III), and that of the Fe(II) produced under pressure, and with the change of the isomer shifts with pressure. The degree of conversion of Fe(III) to Fe(II) correlates well with the change of isomer shift with pressure, and thus with changes of the electronic properties of the ligands. Optical absorption studies as a function of pressure were made on both the charge transfer and intraligand π → π* transitions of several complexes. The decrease in area under the CT peaks correlates very well with the amount of reduction of Fe(III) as obtained from the Mössbauer resonance studies. The shifts of both the CT peaks and π → π* transitions are recorded and discussed briefly.