- WALTER DE GRUYTER GMBH
Using the inclusion complexation of methylene blue with p-sulfonatocalix[ 6] arene (Calix-S6) as a chemical indicator, the association constants of inclusion complexes of Calix-S6 with visible-spectroscopically inert 1-butyl-3-methylimidazolium salts (ionic liquids (IL): counter anions BF4-, PF6-, and Cl-) were determined. It was found that the experimentally observed association constants of IL with Calix-S6 in a water-methanol mixture increased in the order of counter anion Cl- < BF4- < PF6-. The F-19 NMR signals of counter anions BF4- and PF6- shift upfield upon addition of Calix-S6. From the F-19 NMR chemical shifts, we suggested that Calix-S6 forms weak 1 : 1 complexes with the BF4- and PF6- anions. The binding constants and their thermodynamic parameters for the complexation of the BF4- and PF6- anions with Calix-S6 were evaluated in a water-methanol mixture (6 : 4 (V/V)) at 298 K:K-A = 26.2M (-1) for BF4- and 106 M-1 for PF6 (-). Based on the results, the characteristics for the complexation of the counter anions with Calix-S6 were discussed and the inclusion constants of Calix-S6 with the cationic ringmoiety of 1-butyl-3-methyl-imidazolium salts were determined.
Web of Science ® 被引用回数 : 2
Web of Science ® の 関連論文(Related Records®)ビュー