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2010 MAY 28 - (VerticalNews.com) -- "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 Party charm bracelet 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," scientists in Xiangtan, People's Republic of China report.

"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 Tiffany Red heart lock charm and bracelet 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," wrote X.Y. Zheng and colleagues, Xiangtan University.

The researchers concluded: "The calculated results of hydrated cation exchange reaction are in a good agreement with the experimental data for the complexes."

Zheng and colleagues published their study in the Journal of Computational Chemistry (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+. Journal of Computational Chemistry, 2010;31(7):1458-1468).

For additional information, contact X.Y. Wang, Xiangtan Paloma's Zellige bracelet, Key Laboratory Environmentally Friendly Chemical & Applicat, Minist Education, College Chemical, Xiangtan 411105, Hunan, People's Republic of China.

The publisher's contact information for the Journal of Computational Chemistry is: John Wiley & Sons Inc., 111 River St., Hoboken, NJ 07030, USA.