Exploring Cation-π Interaction in the Complexes with B≡B Triple Bond: A DFT Study

Density functional theory calculations on metal ion-π interactions in cation-π complexes of diboryne and sandwiches of diboryne and benzene formed via metal ions were performed to understand the strength of interaction in these complexes. Results suggest that apart from the smaller metal ions (Li⁺, Be²⁺), larger ions (Na⁺, Mg²⁺, Ca²⁺, and Al³⁺) can also form cation-π complexes with B≡B triple bond and interaction energies of the complexes with larger metal ions (possessing same charges) are less than those obtained with smaller ions. Cations with higher charge lead to stronger interaction with the B≡B triple bonds. The calculated interaction energy further reveals that the sandwiches are more stable than their corresponding cation-π complexes. Stability of the complexes is measured in terms of global hardness (using Koopmans' theorem and ΔSCF method), and the values obtained using ΔSCF method corroborate with the stability trend predicted by interaction energy values. Negative solvent-phase interaction energy for most of the chosen complexes indicates their stability in polar solvents too.