Strongly Bound Polynuclear Anions Comprising Scandium Fluoride Building Blocks

The stability of polynuclear anions composed of ScF₃ building blocks was studied by using ab initio and density functional theory electronic structure methods and flexible basis sets. Thorough exploration of ground state potential energy surfaces of (Sc₂F₇)^-, (Sc₃F₁₀)^-, and (Sc₄F₁₃)^- anions which may be viewed as comprising ScF₃ fragments and the additional fluorine atom led to determining the isomeric structures thereof. It was found that the most stable isomers which are predicted to dominate at room temperature correspond to the compact structures enabling the formation of a large number of Sc-F-Sc bridging linkages rather than to the chain-like structures. The vertical electron detachment energies of the (ScF₃)^- anions were found to be very large (spanning the 10.85-12.29 eV range) and increasing with the increasing number of scandium atoms (n) and thus the ScF₃ building blocks involved in the structure. Thermodynamic stability of (ScF₃)^- anions (i.e., their susceptibility to fragmentation) was also verified and discussed.