Cucurbit[7]urilhost–guest complexes of cholines and phosphonium cholines in aqueous solution

Abstract

The neutral host cucurbit[7]uril forms very stable complexes with a series of cationic cholines (R(3)NCH(2)CH(2)OR'(+)) and their phosphonium analogues (R(3)PCH(2)CH(2)OR'(+)) (R(3) = Me(3), Et(3), or Me(2)Bz, or R(3)N = quinuclidinium, and R' = H, COCH(3), CO(CH(2))(2)CH(3), or PO(3)H), and (+/-)-carnitine, in aqueous solution. The complexation behaviour has been investigated using (1)H and (31)P NMR spectroscopies, and ESI mass spectrometry. The complexation-induced chemical shift changes of the guests clearly indicate the effects of replacing the N(CH(3))(3)(+) end group by P(CH(3))(3)(+), and changing the nature of R on the position of the guest with respect to the CB[7] cavity and its polar portal-lining carbonyl groups. This study demonstrates that molecular recognition of cholines in aqueous solution is achievable with a neutral host without the need for aromatic walls for cation-pi interactions.

Host–guest complexes between cucurbit[n]urils and acetanilides having aminopropyl units

“…Firm spectroscopic evidence of the formation of the complexes was obtained by 1 H NMR spectroscopy. Comparison of the 1 H NMR spectra of 1a in the absence and in the presence of an excess of CB [6] shows remarkable upfield shifts for the signals corresponding to the aliphatic protons, while the peaks of the aromatic protons lose their degeneracy, appearing separated the signals of the ortho-, meta-and para-protons and shifted downfield. This is compatible with inclusion of the aliphatic chains inside the hydrophobic cavity of CB [6], the aromatic ring being located near the carbonyl portals.…”

“…Formation of the host-guest complexes for 1a-c was studied for CB [6], CB [7] and CB [8]. Firm spectroscopic evidence of the formation of the complexes was obtained by 1 H NMR spectroscopy.…”

“…The molecular geometry of CBs defines an internal cavity that can be accessed through the carbonyl portals [12][13][14]. Depending on the number of glycoluril units, the internal diameter and the opening of the organic capsule varies from 3.9 to 5.8 Å and from 6.9 to 8.8 Å for CB [6] and CB [8], respectively [13,14].…”

“…[1][2][3][4][5][6][7][8][9][10][11] CBs are cyclic oligomers of glycoluril units connected by methylene bridges. The molecular geometry of CBs defines an internal cavity that can be accessed through the carbonyl portals [12][13][14].…”

Butyration of Lignosulfonate with Butyric Anhydride in the Presence of Choline Chloride

“…4. The peaks were assigned to butyrylcholine according to a previous work (Wyman and Macartney 2010), indicating that the mechanism proposed is reasonable. However, there were some differences in the spectra obtained from the solvent of the present study, and the additional peaks indicate the presence of butyric anhydride and butyric acid synthesized by hydrolysis of butyric anhydride with D2O, as described in Fig.…”