Fragmentation of Nickel(II) and Cobalt(II) Bis(acetylacetonate) Complexes Induced by Slow (<10 eV) Electrons

Abstract

Metal acetylacetonate complexes have high potentiality in nanoscale fabrication processes (e.g., focus electron beam-induced deposition) thanks to the versatile character and ease of preparation compounds. In this work, we study and compare the physics and the physicochemistry induced by the interaction of low-energy (<10 eV) electrons with nickel­(II) and cobalt­(II) bis­(acetylacetonate) complexes. The slow particles decompose the molecules via dissociative electron attachment. The nickel­(II) and cobalt­(II) bis­(acetylacetonate) anions and the acetylacetonate negative fragments are the most dominant detected species. The experimental data are completed with density functional theory calculations to provide information on the electronic states of the molecules and the energetics for fragmentation. Finally, it is found that the interaction of low-energy electrons resulting in the decomposition of organometallic complexes in the gas phase is more efficient with the nickel­(II) than with the cobalt­(II) bis­(acetylacetonate) complex. These results are found to be in a relative agreement with the surface experiments.

Fragmentation of metal(II) bis(acetylacetonate) complexes induced by slow electrons

“… [ML 2 ] − and [L] − yield functions measured from the interaction of electrons with thermally evaporated metal(II) bis(acetylacetonate) (M: Mn, Co, Ni, Cu, and Zn). Data for [ML 2 ] − and [L] − are from [ 15 – 19 ]. …”

“…At first glance, the formation of the precursor anion is very effective for the Co-, Ni- and Cu-containing organometallic complexes, in contrast to MnL 2 and ZnL 2 ( Figure 1 ). These experimental observations may be related in part to the adiabatic electron affinity values of the neutral precursors, which have been calculated to be 1.456, 1.124, 0.498, 0.44, and 0.16 eV for CuL 2 , NiL 2 , and CoL 2 , MnL 2 , and ZnL 2 , respectively [ 15 – 19 ]. As the molecules are sublimated, the pressure of the molecular beam, P , that is, the number of precursors in the gas phase, follows the Clausius–Clapeyron relation (log( P ) = C − Δ H sub / T ), where C is a constant.…”

“…We performed a series of collision experiments of low-energy electrons with metal bis(acetylacetonate)s, ML 2 , where M and L represent a metal (Mn, Co, Ni, Cu, and Zn) and the acetylacetonate ligand, respectively. Previous reports were only dedicated to the mechanism and the energetics for the production of the two predominant species, that is, the parent [ML 2 ] − anion and the ligand [L] − anion [ 15 – 19 ]. In addition to these two species, the interaction of slow electrons with the metal chelates also produces a rich variety of fragment anions, which are reported and discussed in the present report.…”

Multi-Basis-Set (TD-)DFT Methods for Predicting Electron Attachment Energies

“…Consequently, several fits can be found in literature. [19][20][21] One of the main issues to describe the electron scattering in the formalism of ab initio calculations is the difficulty to couple the continuum state of the incoming electron with the discrete states of the molecule. An elegant method to overcome this problem is the stabilization method, where the calculations are repeated using a varying simulation box size.…”

“…It is noteworthy that the scaling factor strongly depends on the level of theory (e.g., choices of the correlation method, the density functional, and the basis set) and possibly on the nature of molecules and excitations investigated. Consequently, several fits can be found in the literature. − …”