Effects of Terminal Groups of Guest on the Pseudorotaxane Assembly of Cucurbit[7]uril†

doi:10.7503/cjcu20170607

Abstract

Abstract:

Three guests bearing different terminal groups —COOH(G1), —CH₂Br(G2) and —CH₃(G3) were synthesized based on the bispyridinium ethylene-core, respectively. The experiment results suggest that Q[7] host could slip the bispyridinium ethylene-core in the assistance of the terminal moiety —COOH of G1, and [2]pseudorotaxane based molecular shuttle could be formed between G1 and Q[7], whereas the terminal moiety —CH₂Br(G2) and —CH₃(G3) could not help Q[7] host slip the bispyridinium ethylene-core. This could be attributed to the different electrostatic potential properties between the terminal groups of the guest and the carbonyl portals of Q[7].

Key words: Cucurbit[n]uril, Pseudorotaxane, Molecular driving force, Host-guest interaction

CLC Number:

TrendMD:

YI Junming,SONG Sen,ZHANG Sheng,ZHANG Shaowei,TIAN Mengkui,NI Xinlong. Effects of Terminal Groups of Guest on the Pseudorotaxane Assembly of Cucurbit[7]uril^†[J]. Chem. J. Chinese Universities, 2018, 39(5): 911.

Figures/Tables 8

Fig.1 1H NMR spectra of G1(a)(1.0 mmol) upon the addition of increasing concentrations[(1.0 mmol, b) and (2.0 mmol, c)] of Q[7] in D2O(pD=2.0)

Scheme 2 Possible interaction mode between G1 and Q[7]

Fig.2 1H NMR spectra of G2(a)(1.0 mmol) upon the addition of increasing concentrations[(1.0 mmol, b) and (2.0 mmol, c)] of Q[7] in D2O(pD=2.0)

Scheme 3 Possible interaction mode between G2 and Q[7]

Fig.3 1H NMR spectra of G3(a)(1.0 mmol) upon the addition of increasing concentrations[(1.0 mmol, b) and (2.0 mmol, c)] of Q[7] in D2O(pD=2.0)

Scheme 4 Possible interaction mode

Fig.4 ITC data(A—C) and thermodynamic curves(A'—C') for the complexation of G1-Q[7](A, A'), G2-Q[7](B, B') and G3-Q[7](C, C')

Table 1 Thermodynamic binding data for G1-Q[7], G2-Q[7] and G3-Q[7]

Host-guest	K_a/(L·mol^-1)	ΔG/(kJ·mol^-1)	ΔH/(kJ·mol^-1)	TΔS/(kJ·mol^-1)
G1-Q[7]	(6.317±0.03)×10⁵	-33.111±0.02	-35.45±0.02	-2.339±0.04
G2-Q[7]	(7.023±0.05)×10⁶	-39.093±0.06	-82.63±0.03	-43.537±0.03
G3-Q[7]	(2.739±0.02)×10⁷	-42.465±0.04	-64.07±0.03	-21.605±0.02

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