title: Density functional theory study of calix[4]arene-N-azacrown-5, calix[4]arene-N-phenyl-azacrown-5, and their complexes with alkali-metal cations: Na+, K+, and Rb+.
abstract: Theoretical studies of 1,3-alternate-25,27-bis(1-methoxyethyl)calix[4]arene-azacrown-5 (L(1)), 1,3-alternate-25,27-bis(1-methoxyethyl)calix[4]arene-N-phenyl-azacrown-5 (L(2)), and the corresponding complexes M(+)/ L of L(1) and L(2) with the alkali-metal cations: Na(+), K(+), and Rb(+) have been performed using density functional theory (DFT) at B3LYP/6-31G* level. The optimized geometric structures obtained from DFT calculations are used to perform natural bond orbital (NBO) analysis. The two main types of driving force metal-ligand and cation-pi interactions are investigated. The results indicate that intermolecular electrostatic interactions are dominant and the electron-donating oxygen offer lone pair electrons to the contacting RY* (1-center Rydberg) or LP* (1-center valence antibond lone pair) orbitals of M(+) (Na(+), K(+), and Rb(+)). What's more, the cation-pi interactions between the metal ion and pi-orbitals of the two rotated benzene rings play a minor role. For all the structures, the most pronounced changes in geometric parameters upon interaction are observed in the calix[4]arene molecule. In addition, an extra pendant phenyl group attached to nitrogen can promote metal complexation by 3D encapsulation greatly. In addition, the enthalpies of complexation reaction and hydrated cation exchange reaction had been studied by the calculated thermodynamic data. The calculated results of hydrated cation exchange reaction are in a good agreement with the experimental data for the complexes.
authors.affiliation: Key Laboratory of Environmentally Friendly Chemistry and Applications of Ministry of Education, College of Chemistry, Xiangtan University, Xiangtan, Hunan 411105, People's Republic of China.
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Zheng
authors.forename: Xueye
authors.initials: X
authors.lastname: Wang
authors.forename: Shanfeng
authors.initials: S
authors.lastname: Yi
authors.forename: Nuanqing
authors.initials: N
authors.lastname: Wang
authors.forename: Yueming
authors.initials: Y
authors.lastname: Peng
mesh_terms: D001372:Aza Compounds / Q000737:chemistry*; D001665:Binding Sites; D047250:Calixarenes / Q000737:chemistry*; D002414:Cations, Monovalent / Q000737:chemistry; D003198:Computer Simulation; D008672:Metals, Alkali / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D011188:Potassium / Q000737:chemistry; D011789:Quantum Theory; D012413:Rubidium / Q000737:chemistry; D012964:Sodium / Q000737:chemistry; D013816:Thermodynamics
chemical_list: D001372:Aza Compounds; D002414:Cations, Monovalent; D008672:Metals, Alkali; D009942:Organometallic Compounds; D047250:Calixarenes; D012964:Sodium; D012413:Rubidium; D011188:Potassium