Structures and electronic properties of exohedral metalloborospherenes Al12Li20&B60 and Al20Li12&B60 and their endohedral systems: push electron oxidation of super-reduced polyanionic states B6050− and B6060−

Abstract

Novel exohedral metalloborospherenes Al₁₂Li₂₀&B₆₀ and Al₂₀Li₁₂&B₆₀ with the classical fullerene-like borospherene B₆₀ were theoretically predicted and their structures and properties were studied. Incredibly, the B₆₀ cage (pull electron oxidizer) pulls 50 and 60e⁻ from exohedral metal atoms, forming two super-reduced polyanionic states B₆₀⁵⁰⁻ and B₆₀⁶⁰⁻, respectively. Next, the two super-reduced polyanionic states (push electron oxidizers) owing to their negative electric fields push out the remaining valence electrons of exohedral metal atoms. Accordingly, the metalloborospherenes convert to electride salt molecules 6e⁻&[(Al³⁺)₁₂(Li⁺)₂₀]&B₆₀⁵⁰⁻ and 12e⁻&[(Al³⁺)₂₀(Li⁺)₁₂]&B₆₀⁶⁰⁻ due to the pull–push electron oxidation relay. It is known that the loss of electrons by the reducing agent results in an oxidation effect. The mechanism of losing electrons involves not only the pull electron but also the push electron, which results in push electron oxidation. As long as there is enough reducing agents in oxidation–reduction electride systems, the unusual pull–push electron oxidation relay will occur, showing new physical insights. More interestingly, the B₆₀^x− (x = 50 or 60) polyanions can also display push electron oxidation for embedded calcium atoms, forming endohedral spherical electride molecules 14e⁻&[(Al³⁺)₁₂(Li⁺)₂₀]&[(Ca₆)⁸⁺@B₆₀⁵⁰⁻] and 22e⁻&[(Al³⁺)₂₀(Li⁺)₁₂]&[(Ca₆)¹⁰⁺@B₆₀⁶⁰⁻], in which the supernormal pull–push–push electron oxidizing ability of the B₆₀ cage is reflected in the total number of pull–push electrons up to 64 and 82, respectively. Remarkably, these spherical electride molecules have extraordinarily small multiple ionization potential (VIP_n, n = 1–22) values, demonstrating a nuclear large-scale effect of the superatomic model on VIP_n.