B36(CO)n+1-PCCP-2026

The discovery of quasi-planar C_6v B₃₆ and C_2v B₃₆⁻ (Piazza et al., Nat. Commun., 2014, 5, 3113) provided the first experimental evidence for the viability of 2D borophene nanomaterials. Joint chemisorption experiment and first-principles theory investigations conducted herein indicate that, as the well-defined global minimum of the monocation, geometrically similar to C_6v B₃₆ and C_2v B₃₆⁻ , the size-selected quasi-planar C_2v B₃₆⁺ (1) with six approximately equivalent tri-coordinate vertex B atoms can consecutively chemisorb up to six CO molecules under ambient conditions to form a series of quasi-planar B₃₆(CO)_n⁺ analogous to coronene monocation C_2h C₂₄H₁₂⁺ in π-bonding, presenting the largest boron carbonyl aromatics (BCAs) observed to date. Kinetic studies have demonstrated that quasi-planar C_2v B₃₆⁺ is about 10, 100, and 1000 times less reactive in experiments towards the first CO than the previously reported perfect planar C_2v B₁₃⁺, double-ring tubular D_2d B₂₀⁺, and quasi-planar C_s B₁₁⁺ and C_2v B₁₅⁺, respectively. Extensive theoretical calculations and analyses revealed the chemisorption pathways and bonding patterns of the experimentally observed B₃₆(CO)_n⁺ and their neutral counterparts B₃₆(CO)_n (n = 1–6), which appear to possess two concentric delocalized π systems over the molecular plane analogous to that of coronene monocation C_2h C₂₄H₁₂⁺ (6π©5π) and neutral coronene D_6h C₂₄H₁₂ (6π©6π), respectively, imparting dual π-aromaticity and high stability to the systems.