Electronic structure and nature of the metal-ligand chemical bond of Be, Mg, and Zn β-diketonates by quantum chemistry methods

The electronic structure of Be (II), Mg (II), and Zn (II) acetylacetonates and hexafluoroacetylacetonates was calculated in the DFT approximation. The energies of MOs and ionization energies calculated by the OVGF method were compared with the published data of photoelectron spectroscopy (HeI). The outer valence region of the spectra is equally effectively reproduced by DFT and OVGF methods. The calculations allowed determining the ionization energies of the π2 orbitals of the chelate cycles. It was determined that an increase in the binding energy of the electrons of the valence and core levels upon substitution of CH3>CF3 by 1,7–2,1 eV was correlated with a change of the negative charge of the carbon atom of the substituted groups on positive one. The polarity of M − O bonds increases in the series of Be, Mg, Zn. It was found that in addition to outer valence orbitals, a covalent bonding was also significantly affected by the deep valence σ-orbital 4a1 with a high degree of overlap with metal s-orbitals.