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

Nowadays, organometallic complexes receive particular attention because of their use in the design of pure nanoscale metal structures. In the present work, we present results obtained from a series of studies on the degradation of metal(II) bis(acetylacetonate)s induced by low-energy electrons. These slow particles induce the formation of the acetylacetonate anion, [acac]-, and the parent anion as the most dominant species at incident electron energies near 0 eV. They also fragment the organometallic compounds via various competitive reaction channels that occur at higher energies via dissociative electron attachment. The reported data may contribute to a better understanding of the physical chemistry underlying the electron-molecule interactions, which is crucial for potential applications of these molecular systems in the deposition of nanoscale structures.

Diffuse Basis Functions for Relativistic s and d Block Gaussian Basis Sets

Diffuse s, p, and d functions have been optimized for use with previously reported relativistic basis sets for the s and d blocks of the periodic table. The functions were optimized on the 4:1 weighted average of the s² and p² configurations of the anion, with the d shell in the dⁿ⁺¹ configuration for the d blocks. Exponents were extrapolated for groups 2 and 12, which have unstable or weakly bound anions. The diffuse basis sets have been tested by application to calculations of electron affinities of the group 11 elements (Cu, Ag, and Au), double electron affinities of the group 11 monocations, and potential energy curves of Mg₂ and Ca₂ van der Waals dimers, as well as some response properties of the group 1 anions (Rb^-, Cs^-, and Fr^-), the group 2 elements (Sr, Ba, and Ra), and RbLi, CsLi, and FrLi molecules.

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

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.

Core-excited resonances initiated by unusually low energy electrons observed in dissociative electron attachment to Ni(II) (bis)acetylacetonate

Dissociative electron attachment is a mechanism found in a large area of research and modern applications. This process is initiated by a resonant capture of a scattered electron to form a transitory anion via the shape or the core-excited resonance that usually lies at energies above the former (i.e., >3 eV). By studying experimentally and theoretically the interaction of nickel(II) (bis)acetylacetonate, Ni(II)(acac)₂, with low energy electrons, we show that core-excited resonances are responsible for the molecular dissociation at unusually low electron energies, i.e., below 3 eV. These findings may contribute to a better description of the collision of low energy electrons with large molecular systems.

Decomposition of Bis(acetylacetonate)zinc(II) by Slow Electrons

The production of zinc-containing nanostructures has a large variety of applications. Using electron beam techniques to degrade organometallic molecules for that purpose is perhaps one of the most versatile methods. In this work, we investigate the scattering of low-energy (<12 eV) electrons with bis(acetylacetonate)zinc(II) molecules. We show that core excited and high-lying shape resonances are mainly responsible for the production of the precursor anions as well as the ligand negative fragments, which are observed exclusively at electron energies of >3 eV. The mechanisms for electron capture and then molecular dissociation are discussed in terms of density functional theory studies.

Interaction of Slow Electrons with Thermally Evaporated Manganese(II) Acetylacetonate Complexes

Complexes of metal acetylacetonate are used as general precursors for the synthesis of metal oxide nanomaterials. In the present work, we study the interaction of low-energy (<10 eV) electrons, produced abundantly as secondary electrons during the bombardment of the substrate by the primary particles, with thermally evaporated manganese(II) acetylacetonate complexes. We found that the acetylacetonate anion ([acac]^-) is the major anionic species produced, while the second most abundant is the parent anion [Mn(II)(acac)₂]^-. This observation differs from those reported from electron attachment to Cu(acac)₂, for which [Cu(II)(acac)₂]^- is the predominant anion [Kopyra et al. Phys. Chem. Chem. Phys. 2018, 20, 7746]. The experimental data are supported by theory to provide information on the physical-chemistry processes initiated by slow electrons to the organometallic precursor and to interpret the different behavior of Mn(acac)₂ compared to Cu(acac)₂.

Dissociation of the FEBID precursor cis-Pt(CO)2Cl2 driven by low-energy electrons

In this study, we present experimental and theoretical results on dissociative electron attachment and dissociative ionisation for the potential FEBID precursor cis-Pt(CO)₂Cl₂. UHV surface studies have shown that high purity platinum deposits can be obtained from cis-Pt(CO)₂Cl₂. The efficiency and energetics of ligand removal through these processes are discussed and experimental appearance energies are compared to calculated thermochemical thresholds. The present results demonstrate the potential effectiveness of electron-induced reactions in the deposition of this FEBID precursor, and these are discussed in conjunction with surface science studies on this precursor and the design of new FEBID precursors.

Electron-induced chemistry of surface-grown coordination polymers with different linker anions

Electron beam processing of surface-grown coordination polymers is a versatile approach to the fabrication of nanoscale surface structures. Depending on their molecular components, these materials can be converted into pure metallic particles or they can be activated to become a template for the spatially selective decomposition of suitable gaseous precursor molecules and subsequent autocatalytic growth of deposits. However, insight into the fundamental electron-induced chemistry for such processes has been scarce so far. Therefore, we investigated the electron-induced reactions of three self-assembled copper-containing materials, namely, copper(ii) oxalate, copper(ii) squarate, and copper(ii) 1,3,5-benzenetricarboxylate (HKUST-1) which were grown on the surface of self-assembled monolayers of mercaptoundecanoic acid in a layer-by-layer approach from copper(ii) acetate and various linker molecules. Changes incurred to these materials during electron irradiation were monitored by four complementary techniques. Reflection absorption infrared spectroscopy (RAIRS) and X-ray photoelectron spectroscopy (XPS) were used to identify the chemical species that are formed upon electron exposure. The temporal evolution of electron-stimulated desorption (ESD) of neutral volatile fragments was monitored to reveal the kinetics governing the decomposition of the different materials. Furthermore, the morphology was investigated by helium ion microscopy (HIM). A detailed analysis of the results for the different linker molecules provides new insights into the electron-induced chemistry of such surface-grown layers.