Properties of manganese(III) ferrocenyl-β-diketonato complexes revealed by charge transfer and multiplet splitting in the Mn 2p and Fe 2p X-ray photoelectron envelopes

A series of ferrocenyl-functionalized β-diketonato manganese(III) complexes, [Mn(FcCOCHCOR)3] with R = CF3, CH3, Ph (phenyl) and Fc (ferrocenyl) was subjected to a systematic XPS study of the Mn 2p_3/2 and Fe 2p_3/2 core-level photoelectron lines and their satellite structures. A charge-transfer process from the β-diketonato ligand to the Mn(III) metal center is responsible for the prominent shake-up satellite peaks of the Mn 2p photoelectron lines and the shake-down satellite peaks of the Fe 2p photoelectron lines. Multiplet splitting simulations of the photoelectron lines of the Mn(III) center of [Mn(FcCOCHCOR)3] resemble the calculated Mn 2p_3/2 envelope of Mn3+ ions well, indicating the Mn(III) centers are in the high spin state. XPS spectra of complexes with unsymmetrical β-diketonato ligands (i.e., R not Fc) were described with two sets of multiplet splitting peaks representing fac and the more stable mer isomers respectively. Stronger electron-donating ligands stabilize fac more than mer isomers. The sum of group electronegativities, σχR, of the β-diketonato pendant side groups influences the binding energies of the multiplet splitting and charge transfer peaks in both Mn and Fe 2p_3/2 photoelectron lines, the ratio of satellite to main peak intensities, and the degree of covalence of the Mn-O bond.