Quantum simulation on donor and acceptor II calix[4]arene substrate and alkali metal ions: the driven inclusion

摘要

The energetic and structural optimized of a calix[4]arene with and without alkali-metal cations are presented with performance of various quantum chemical methods such as Hartree-Fock, second order Moller-Plesset perturbation theory, and density functional theory. The geometry optimizations have been carried out with the 3-21G (Li+-Cs+) and 3-21G(d,p) (Li+-K+) and the 3-21G basis sets for Cs+ and Rb+. Additional single-point energy ab initio calculations for Li+-K+ were carried out at HF/6-31G, HF/6-31G (d,p), HF/6-311G(d,p) for complexes of Li+ and Na+. The calculations were carried out to analyze the complexation of calix[4]arene with alkali metal cationic species (Li+, Na+, K+, Rb+, and Cs+). Assumption to isolate the effects of the aromatic core and cation-pi interactions. Particular emphasis has been on conformational binding selectivity and the structural characterization of the complexes, the smaller cation as Li+ and Na+ has been placed in the lower rim's of the calix[4]arene's cavity. The large cations like K+, Rb+, and Cs+ take placed in upper rim and the endo (inclusive) complexation is driven by cation-pi interactions, that reflect a superior interaction with two phenol rings. The endo complexation of Cs+ with calix[4]arene is in agreement with X-ray diffraction data. The binding modes of calixarene-cation systems are studied to involve cooperative effects between cation-pi and electrostatic forces.