Journal of Physical Chemistry A, Vol.124, No.22, 4379-4389, 2020
Interplay between sigma Holes, Anion center dot center dot center dot H-C, and Cation-pi Interactions in Dibromo[2,2]paracyclophane Complexes
Theoretical calculations were performed to investigate the interplay between sigma-hole, anion-HC and cation-pi interactions in the complexes of dibromo[2,2]paracyclophane (DBr[2,2]PCP) with alkali (Li+, Na+, K+), alkaline earth metal cations (Be2+, Mg2+, and Ca2+), and halogen anions (F-, Cl-, and Br-) using the wave function (MP2) and density functional theory (M06-2X and B3LYP) methods with the 6-311++G(d,p) basis set. The study reveals that DBr[2,2]PCP behaves as amphoteric molecule with a predominance of basic character. It prefers to interact with hard cations and hard anions such as Be2+ and F- through cation-p and anion center dot center dot center dot HC interactions, respectively. Substitution of Br by F and Cl atoms in DBr[2,2]PCP decreases slightly the interaction energies of DX[2,2]PCP-halogen complexes (X = F, Cl, and Br) by 2.0 and 0.3 kcal/mol (M06-2X), respectively. The anion-HC interactions in DBr[2,2]PCP complexes are similar to 10 kcal/mol stronger (B3LYP; similar to 15 kcal/mol at M06-2X and 7 kcal/mol at MP2) than the sigma-hole interactions.