Quantum chemistry insight into the interactions of 1,3-diisopropoxycalix[4]arenecrown-6 with alkali metal cations: Structure, selectivity, and solvation

Abstract

Double-hybrid functional PWPB95-D3 with precise description of dispersion is employed to calculate the thermodynamic properties of complexes with 1,3-Diisopropoxycalix[4]arenecrown-6 (BPC6) and alkali metal cations (Li+, Na+, K+, Rb+, and Cs+) in the gas phase and solutions (chloroform, methanol, and acetonitrile). Moreover, symmetry-adapted perturbation theory (SAPT) and IGM based on Hirshfeld partition of molecular density (IGMH) are for the first time used to reveal the interactions of complexes due to the accuracy energy decomposition and markedly graphical effect, respectively. For the complexes of BPC6 with alkali metal cations in the gas phase, the electrostatic energy takes up nearly 70% of the total energy. The electrostatics energy dominated attractive part of the interaction energy. The dielectric screen of solvents leads to the decrease of the absolute value of binding Gibbs free energy (|ΔG|). The protic solvent provides a further decrease of |ΔG|. The |ΔG| of each M+/BPC6 complex in solvents follow the order of |ΔG|(gas) > |ΔG|(chloroform) > |ΔG|(acetonitrile) > |ΔG|(methanol). In complex Cs+/BPC6, the ratio of dispersion is as high as 26%. Thus, the dispersion interaction is non-negligible for complexation with large cations in the solvents. Because the ΔG of complex Cs+/BPC6 is less affected by solvation effect than that of other cations, Cs+/BPC6 is the most stable complex in all the three solvents. The |ΔG| of complexes with alkali metal cations decreases with the increase of the cationic radii in the gas phase, and increases with that in the solvent solutions. The regulars of |ΔG| are well match that of the experimental results in literatures.