Lanthanide/actinide boride nanoclusters and nanomaterials based on boron frameworks consisting of conjoined Bn rings (n = 7–9)

Abstract

Extensive global minimum searches augmented with first-principles theory calculations performed in this work indicate that the experimentally observed perfect inverse sandwich lanthanide boride complexes D_7h La₂B₇⁻ (1), D_8h La₂B₈ (3), D_9h La₂B₉⁻ (7) can be extended to their actinide counterparts C_2v Ac₂B₇⁻ (1′), D_8h Ac₂B₈ (3′), D_9h Ac₂B₉⁻ (7′) with a B_n monocyclic ring (n = 7–9) sandwiched by two Ac dopants. Such M₂B_n^−/0 inverse sandwiches (1/1′, 3/3′, 7/7′) can be used as building blocks to generate the ground-state C₂ La₄B₁₃⁻ (2)/Ac₄B₁₃⁻ (2′), D₂ La₄B₁₅⁻ (4)/Ac₄B₁₅⁻ (4′), C_3v/C₃ La₄B₁₈ (5)/Ac₄B₁₈ (5′), O_h Ac₇B₂₄⁺ (6′), O_h Ac₇B₂₄, T_d Ac₄B₂₄ (8′), C₁ La₅B₂₄⁺ (9)/Ac₅B₂₄⁺ (9′), and T_d Ac₄B₂₉⁻ (10′) which are based on boron frameworks consisting of multiple conjoined B_n rings (n = 7–9). Detailed bonding analyses show that effective (d–p)σ, (d–p)π and (d–p)δ coordination bonds are formed between the B_n rings and metal doping centers, conferring three-dimensional aromaticity and extra stability to the systems. In particular, the perfect body-centered cubic O_h Ac₇B₂₄⁺ (6′) and O_h Ac₇B₂₄ with six conjoined B₈ rings can be extended in x, y, and z dimensions to form one-dimensional Ac₁₀B₃₂ (11′), two-dimensional Ac₃B₁₀ (12′), and three-dimensional AcB₆ (13′) nanomaterials, presenting a B₈-based bottom-up approach from metal boride nanoclusters to their low-dimensional nanomaterials.