Theoretical investigation of a cation‐controllable molecular shuttle of tetracationic cyclophane

Abstract

An ion-controllable molecular switch comprising a tetracationic cyclophane (CBPQT 4+ ) macroring bound to [2]pseudorotaxanes has been investigated by density functional theory. The role of noncovalent interactions has been assessed with the reduced density gradient method and binding energies. Moreover, the natural bond orbital is used to evaluate the strength of hydrogen bonding, π-π and cation-π interactions. The electrostatic repulsions between the bound K + ion and tetracationic cyclophane were also calculated. The theoretical calculations confirmed that the 18-crown-6 derivative containing a 1,5-dioxynaphthalene residue station exhibits the strongest binding interaction, and the hydrogen bond and electrostatic forces are prevalent at all stations.These calculated results are in agreement with the hypothesis proposed by Stoddart.