Carboxyl substituted Bambus[6]uril as a novel macrocyclic receptor for cyanide anion: A DFT study

Using density functional theory calculations, the most probable conformation of CN- based carboxyl substituted bambus[6]uril complex was investigated. The molecular complex shows the C3 symmetry in which the cyanide anion resides in the cavity of the macrocyclic complex. The parent macrocycle reduces the diameter of its inner cavity to adjust the anionic specie. Furthermore, we report the AIM and NCI analysis to interpret various non -covalent interactions between the CN- and carboxyl-substituted BU[6] macrocycle. The results of NCI analysis show certain types of noncovalent interactions between the receptor and anion, which are responsible for the stability of the complex. Four N H-type interactions between the anion and hydrogen atoms of the methine group in the macrocycle exhibit H-bonds, which are analyzed by QTAIM. The interaction energy of the optimized complex was -81.25 kcal/mol.