540495-04-3Relevant articles and documents
Do dibenzo[22-30]crown ethers bind secondary ammonium ions to form pseudorotaxanes?
Tokunaga, Yuji,Yoshioka, Megumi,Nakamura, Tatsuya,Goda, Tatsuhiro,Nakata, Ryuji,Kakuchi, Suzuka,Shimomura, Youji
experimental part, p. 1377 - 1382 (2009/06/20)
In this study, we synthesized dibenzo[22-30]crown ethers and dumbbell-like secondary ammonium salts having stoppers of varying bulk. These crown ethers formed pseudorotaxanes with the ammonium ions in solution and in the gas phase, as evidenced using NMR spectroscopy and MS/MS spectrometry, respectively. The association constants in solution were obtained through regulation of the association and dissociation rates by varying the nature of the stopper groups of the dumbbell-like ammonium ions. The [25]- and [26]crown ether/ isopropylphenyl group, the [27]- and [30]crown ether/tert-butylphenyl group, and the [22]- and [23]crown ether/furyl group were matched pairs. 1 HNMR spectra of mixtures (CDCI3/CD3CN) of the crown ethers and their matched ammonium salts indicated the presence of three sets of signals in solution: those of the crown ether, the ammonium salt, and their pseudorotaxane. Integration of pertinent signals allowed the association constants of pseudorotaxanes to be determined readily. Among the [22-30]crown ethers, the highest value of the association constant was that for the [24]crown ether/dibenzylammoniumion system; the [25-30]crown ether/ammonium ion systems exhibited moderate values of their association constants [Kexp - 35-114 M-1 when using (ArCH2)2NH 2+PF6- as the ammonium salt at 27 °C; Kexp = 21 M-1 when using (ArCH2) 2NH2+TsO- at 27 °C]. The [22]- and [23]crown ethers interacted weakly [Kexp = 6-14 M-1 when using (ArCH2)2NH2+TsO - at27°C].
