Interaction of gas phase copper(ii) acetylacetonate with slow electrons

Abstract

Understanding the fundamental processes underlying the interaction of organometallic compounds with low energy electrons is desirable for optimizing methodologies for nanoscale applications. In this work, we couple experimental measurements with theories to investigate the interaction of gas phase copper(ii) acetylacetonate, Cu(acac), with low energy (<12 eV) electrons. Near 0 eV, a multipole-bound anion is likely to act as the doorway for the formation of a transitory molecular anion which then undergoes stabilization via a 90°-rotation of one of the acac units. The production of the parent anion competes with the dissociation processes, generating preferentially the acetylacetonate negative ion. Moreover, at incident electron energies above 3.5 eV, the electron driven fragmentation of Cu(acac) is likely to produce atomic Cu. These results can suggest some potential strategies for the deposition of pure copper using an appropriate electron irradiation technique.

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

“…The present results follow the same trend as those obtained for the Cu(acac) 2 system, for which the reaction Cu(acac) 2 * − → Cu(acac) + [acac] − is endothermic but by ∼1.5 eV. 38 Since, for the copper system, the [acac] − anion formed near 0 eV represents only 2.8% of the [Cu(acac) 2 ] − anion, we suggested that the fragmentation is favored by the accumulated energy via thermal excitation of some accessible vibration modes. In the present case, the yield of the [acac] − anion is ∼10 times larger than that of the Mn(acac) 2 − anion, and the energy threshold is also higher; therefore, the argument employed for the copper acetylacetonate system is unlikely.…”

“…From these results and as shown by the energetic diagram (Figure 2b), the calculated electron affinity value of the acac radical from the Mn(II)(acac) (in the septet configuration, S = 3) + [acac] − agrees with the previously calculated value from Cu(acac) 2 . 38 In this S = 3 electronic configuration, the dissociative electron attachment to the Mn(acac) 2 molecule to form the [acac] − anion is found to be endothermic by 2.01 eV (Table 1). The fragmentation channel associated with the Mn(II)(acac) in the quintet electronic arrangement is found to be higher by 0.8 eV.…”

“…Note that we are measuring the negative ions for which the intensities cannot be directly related to that of the produced neutral molecules, since the interaction cross sections and the lifetimes of the transitory parent anions are not known for these molecular systems. These results are contrasting with the copper-ligand system, since both the [acac] − and the [Cu­(acac) 2 ] − are generated from the interaction of electrons with the Cu­(acac) 2 precursor thermally desorbed from the crystal . At energies above 2 eV, the [acac] − anion can also be produced from Mn­(II)­(acac) 2 .…”

“…These results are contrasting with the copper-ligand system, since both the [acac] − and the [Cu(acac) 2 ] − are generated from the interaction of electrons with the Cu(acac) 2 precursor thermally desorbed from the crystal. 38 At energies above 2 eV, the [acac] − anion can also be produced from Mn(II)(acac) 2 .…”

Electron Beam-Induced Surface Activation of Metal–Organic Framework HKUST-1: Unraveling the Underlying Chemistry

“…The only conceivable additional reaction pathway is electron attachment into an empty d-orbital of Cu 2+ , thus leading to formal reduction to Cu(I). This changes the preferred coordination geometry 42 and is expected to also destabilize the binding of the oxalate linkers.…”