title: Computational investigation of a new ion-pair receptor for calix[4]pyrrole.
abstract: Theoretical studies of a new ion-pair receptor, meso-octamethylcalix[4]pyrrole (OMCP), and its interactions with the halide anions F(-), Cl(-), and Br(-) and the cesium halides CsF, CsCl, and CsBr have been performed. Geometries, binding energies, and binding enthalpies were evaluated with the restricted hybrid Becke three-parameter exchange functional (B3LYP) method using the 6-31+G(d) basis set and relativistic effective core potentials. The optimized geometric structures were used to perform natural bond orbital (NBO) analysis. The two typical types of hydrogen bonds, N-H…X(-) and C-H…X(-), were investigated. The results indicate that hydrogen bonding interactions are dominant, and that the halide anions (F(-), Cl(-), and Br(-)) offer lone pair electrons to the σ*(N-H) or σ*(C-H) antibonding orbitals of OMCP. In addition, electrostatic interactions between the lone pair electrons of the halide anion and the LP* orbitals of Cs(+) as well as cation-π interactions between the metal ion and π-orbitals of the pyrrole rings have important roles to play in the Cs(+)•OMCP•X(-) complexes. The current study further demonstrates that this easy-to-make OMCP host compound functions as not only an anion receptor but also an ion-pair receptor.
authors.affiliation: Key Laboratory of Environmentally Friendly Chemistry and Applications of Ministry of Education, College of Chemistry, Xiangtan University, Xiangtan, Hunan, People's Republic of China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Xia
authors.forename: Xueye
authors.initials: X
authors.lastname: Wang
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhang
authors.forename: Benhua
authors.initials: B
authors.lastname: Luo
authors.forename: Yi
authors.initials: Y
authors.lastname: Liu
mesh_terms: D000465:Algorithms; D001965:Bromides / Q000737:chemistry; D047250:Calixarenes / Q000737:chemistry*; D002586:Cesium / Q000737:chemistry; D002712:Chlorides / Q000737:chemistry; D003198:Computer Simulation; D056831:Coordination Complexes / Q000737:chemistry*; D005459:Fluorides / Q000737:chemistry; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008968:Molecular Conformation; D011166:Porphyrins / Q000737:chemistry*; D011789:Quantum Theory; D013816:Thermodynamics
chemical_list: D001965:Bromides; D002712:Chlorides; D056831:Coordination Complexes; D011166:Porphyrins; C469811:calix(4)pyrrole; C078556:cesium bromide; D047250:Calixarenes; D002586:Cesium; C028019:cesium chloride; D005459:Fluorides; C027754:cesium fluoride