Theoretical investigation of the complexation of crown ethers and crown ethers of fulleropyrrolidine with (CH3)xNH +4−x, x = 0–4

Abstract

The electronic and geometric structures of dibenzo-12-crown-4, dibenzo-18-crown-6, and dibenzo-24-crown-8 ethers, and dibenzo-18-crown-6 ether of fullero-N-methylpyrrolidine and their complexes with (CH₃)_xNH⁺_4−x, x = 0–4 were investigated by employing density functional theory (B3LYP, M05-2X, M06-2X, MPWBIK and B2PLYP-D) in conjunction with three basis sets. Different energetic minima have been identified for all of the above molecules and complexes in the gas phase as well as in CHCl₃ solvent. We report geometries, complexation energies and some thermochemical data. For increasing values of x, the complexation energies, corrected for the basis set superposition error range from 3.29 to 0.73 eV in the gas phase and from 1.56 to 0.13 eV in the CHCl₃ solvent. In the case of the largest crown ethers, the 24-crown-8 ethers are folded around the ammonium cation so as to maximize the number of hydrogen bonds formed and present the largest complexation energies. Finally, the presence of fullero-N-methylpyrrolidine, attached to the crown ethers, does not change the complexation energies substantially.