Protonation effects on the inclusion complexation of 6-deoxy-6-diethylamino-beta-cyclodextrin with 2-anthracenesulfonate, 2-naphthalenesulfonate, 2,6-naphthalenedisulfonate, and 2,7-naphthalenedisulfonate in aqueous solutions.
At pH values 5.5 and 10.3, 6-deoxy-6-diethylamino-beta-cyclodextrin (DD-beta-CD) as well as beta-CD forms 1:1 inclusion complexes with 2-anthracenesulfonate (2AS), 2-naphthalenesulfonate (2NS), 2,6-naphthalenedisulfonate (2,6NDS), and 2,7-naphthalenedisulfonate (2,7NDS). The equilibrium constants (K) for the formation of the 1:1 inclusion complexes have been evaluated from the absorbance and/or fluorescence intensity changes. With respect to the beta-CD inclusion complexes of 2AS, 2NS, 2,6NDS, and 2,7NDS, the K values at pH 5.5 are nearly the same as the corresponding ones at pH 10.3. In the case of the DD-beta-CD inclusion complexes, the K values of 2AS and 2NS similarly do not depend on the pH value. However, the K values of 2,6NDS and 2,7NDS for DD-beta-CD at pH 5.5 have been found to be more than two times greater than the corresponding ones at pH 10.3, suggesting the electrostatic attraction between the protonated diethylamino group of DD-beta-CD and the sulfonato group of the NDSs.
Hamai
S
S
Department of Chemistry, Faculty of Education and Human Studies, Akita University, Japan. hamai@ipc.akita-u.ac.jp
Ishikawa
S
S
D003505:Cyclodextrins / Q000737:chemistry*; D007700:Kinetics; D009282:Naphthalenesulfonates / Q000737:chemistry*; D012996:Solutions; D013050:Spectrometry, Fluorescence; D013053:Spectrophotometry; D014867:Water; D047392:beta-Cyclodextrins
C425151:6-deoxy-6-diethylamino-beta-cyclodextrin; D003505:Cyclodextrins; D009282:Naphthalenesulfonates; D012996:Solutions; D047392:beta-Cyclodextrins; D014867:Water