Abstract
Two symmetric amphiphilic imidazolium ionic liquids having ω-undecenyl chains form supramolecular complexes with CB[7] and CB[8] in water as revealed by 1H NMR spectroscopy and MALDI-MS. Binding constants in the range 10 4 to 10 5 M -1 were estimated from the conductivity measurements for the 1:1 complexes of these imidazolium ionic liquids with CB[7] and CB[8]. Radical initiated polymerization of these host-guest complexes at concentrations above the critical self-assembly concentration of imidazolium ionic liquids to form liposomes, destroys completely (CB[7]) or partially (CB[8]) the host-guest ionic liquid@CB[n] complex; this behaviour was proved by titration with acridine orange tricyclic dye, of CB[n]s in the colloidal solutions of the liposomes before and after performing dialysis to remove free CB[n]s. Thus, the increase in the fluorescence emission of acridine orange by CB[7] is not observed if the polymerized ionic liquid@CB[7] complex is submitted to dialysis to remove uncomplexed CB[7]. Analogous study by titration of absorbance change of acridine orange solutions caused by CB[8], reveals only a partial destruction of the host-guest complex by self-assembly of amphiphilic ionic liquid above the critical self-assembly concentration. The results obtained have been rationalized considering that the driving force for the formation of supramolecular ionic liquid@CB[n] complexes is a hydrophobic interaction between the apolar alkenyl chain and the cucurbituril interior cavity and that these hydrophobic interactions are disturbed when self-assembly leading to liposomes occurs.
Original language | English |
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Pages (from-to) | 4296-4301 |
Number of pages | 6 |
Journal | Tetrahedron |
Volume | 68 |
Issue number | 22 |
DOIs | |
Publication status | Published - 3 Jun 2012 |
Externally published | Yes |
Keywords
- Cucurbit[n]urils
- Host-guest complex
- Ionic liquids
- Liposome
- Self-assembly