title: Spectroscopic study on anion recognition properties of calix[4]pyrroles: effects of tetraalkylammonium cations.
abstract: The solution binding properties of calix[4]pyrroles with anion (added as tetraalkylammonium salts) were investigated using UV-vis spectroscopic techniques. The obvious red-shift of absorption maximum band of calix[4]pyrrole in EtOH in the presence of the tetramethylammonium (TMA(+)) or tetraethylammonium (TEA(+)) salts were observed. These results displayed in electronic absorption spectra indicated calix[4]pyrrole receptors linking anionic species through multiple hydrogen bonding interactions are capable of using the periphery electron-rich "walls" for selectively binding electron-deficient tetraalkylammonium cation subunits by cation-pi charge-transfer interaction. It was seen that the stability of the calix[4]pyrrole-anion complex depends strongly on the cation. The meso-alkyl groups of the calix[4]pyrrole, the affinity for the anion subunits and the structure of tetraalkylammonium cations have considerable effects on the formation of cation-pi charge-transfer interaction.
authors: Key Laboratory for Natural Medicine of Gansu Province, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, PR China.
authors: Kai
authors: K
authors: Liu
authors: Jian
authors: J
authors: Xu
authors: Yajie
authors: Y
authors: Sun
authors: Yong
authors: Y
authors: Guo
authors: Shengxiang
authors: S
authors: Jiang
authors: Shijun
authors: S
authors: Shao
mesh_terms: D047250:Calixarenes / Q000737:chemistry*; D000431:Ethanol / Q000737:chemistry; D007700:Kinetics; D011166:Porphyrins / Q000737:chemistry*; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D012996:Solutions; D013056:Spectrophotometry, Ultraviolet; D019789:Tetraethylammonium / Q000737:chemistry*
chemical_list: D011166:Porphyrins; D000644:Quaternary Ammonium Compounds; D012996:Solutions; C469811:calix(4)pyrrole; D047250:Calixarenes; D000431:Ethanol; D019789:Tetraethylammonium; C027917:tetramethylammonium