Electronic structure and stability of transition metal acetylacetonates TM(AcAc)n (TM = Cr, Fe, Co, Ni, Cu; n = 1, 2, 3)

Abstract

Transition metal acetylacetonates have a wide range of technological applications, such as modifiers in polymers and polymerization catalysts. Since the electronic structure defines the physical-chemistry properties of these materials and ultimately their selectivity in technological applications, its characterization is of paramount importance. In this work, the general trends on the electronic structure of the transition metal acetylacetonate TM(AcAc) were estimated from qualitative and quantitative approaches. The qualitative picture, based on the ligand field theory, allowed to establish a relation between the d-orbital electron occupancy and the stability of the system, in which the Cu(AcAc)2 presents a limitrophe case, indicating moderate stability and reactivity. On the quantitative approach, the low-lying electronic states of TM(AcAc) were characterized by highly correlated methods. The thermodynamic and kinetic stabilities of TM(AcAc)n were ranked by using a stability index based on parameters of the wavefunction, namely, the excitation energy, the free energy of atomization, and the HOMO energy, showing a good agreement with the qualitative results. Besides the spectroscopic data provided for TM(AcAc)n, the combined qualitative and quantitative results can guide the choice of a specific TM(AcAc)n in applications that require higher or lower stabilities.