MPW1PW91‐Calculated Structures, IR Spectra, and Frontier Orbitals of Benzoylmethoxythiacalix[4]arene Complexed with Alkali Metal Ions

Abstract

The molecular structures of four conformers [cone (CONE), partial cone (PACO), 1,2‐alternate (12A), and 1,3‐alternate (13A)] of benzoylmethoxythiacalix[4]arene 1 and the corresponding alkali metal ion complexes were optimized by using a mPW1PW91/6‐31G(d,p) (hybrid Hartree–Fock density functional) calculation method. The 13A conformer was the most stable among the various conformers of 1 because of less steric hindrance. The total electronic and Gibbs free energies, complexation energies, and the gap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) frontier orbitals of the complexes of 1 with the sodium and potassium ions were analyzed. Among the ditopic complexes, the 13A‐type 1•2Na+ complex exhibited the strongest binding efficiency. The binding efficiency of the CONE‐type 1•Na+ complex was much stronger than that of the 12A‐type 1•Na+ complex. However, the 1•K+ complexes were relatively insensitive to the conformation of host 1. The calculated binding preference of the various conformers is consistent with the empirical solution data. The infrared spectra of the conformers of 1 and their exo complexes with the alkali metal ions were calculated by mPW1PW91 and analyzed.