Modes of Binding Interaction between Viologen Guests and the Cucurbit[7]uril Host

Article abstract of DOI:10.1021/ol035967x

(Matrix presented) Host-guest interactions between cucurbit[7]uril (CB7) and a series of dialkyl-4,4′-bipyridimum (viologen) dicationic guests were investigated by NMR spectroscopy. CB7 includes the aromatic nucleus of short chain viologens, but the mode of interaction is different with longer chain viologens due to the favorable hydrophobic interactions between the terminal alkyl substituents and the inner cavity of the host. A new pseudorotaxane was designed and synthesized on the basis of viologen-CB7 binding interactions.

Full text of DOI:10.1021/ol035967x

Modes of Binding Interaction Between Viologen Guests and the
Cucurbit[7]uril Host
Kwangyul Moon and Angel E. Kaifer*
Center for Supramolecular Science and Department of Chemistry, University of
Miami, Coral Gables, FL 33124-0431.
Supporting information
Diffusion coefficient of guest molecule
Guest : Ethylviologen
Host: CB7
Solvent: 0.2 M NaCl in D2O
Instrument: 500MHz NMR
Diffusion coefficient of H, G as a ratio of H/G
6.5
6
5.5
5
4.5
4
3.5
3
2.5
2
0
0.5
1
1.5
2
2.5
3
3.5
ratio of H/G

NMR titration of propylviologen with CB7
Solvent : 0.2 M NaCl in D2O, 500MHz
A: propylviologen
B: addition of CB7 (0.34eq)
C: addition of CB7 (1.03eq)
D: addition of CB7 (1.72eq)

NMR titration of butyl viologen with CB6
Solvent : 0.2M NaCl in D2O, 300MHz
A : butyl viologen
B : addition of CB6 (0.5eq)
C : addition of CB6 (1.0eq)
D : addition of CB6 (1.5eq)
Asteric is a solvent (acetone)

NMR titration of heptylviologen with CB7
Solvent : DMSO-d6, 500MHz
A: heptyl viologen
B: addition of CB7 (0.4eq)
C: addition of CB7 (1.05eq)
D: addition of CB7 (1.4eq)

NMR titration of amino-dinitrophenyl-propyl viologen with CB7
Solvent : D2O, 500MHz
A: amino-dinitrophenyl-propyl viologen
B: addition of CB7 (0.66eq)
C: addition of CB7 (1.09eq)

General procedure for the synthesis of bis(alkyl)viologens
A mixture of 4,4’-dipyridyl (1.0 equiv) and the corresponding alkyl bromide (8 equiv) in CH3CN
was refluxed for 3days. The resulting precipitate was filtered, washed with hot chloroform to
remove monoalkylated product and dried under vacuum.
1H NMR of EV2+(500MHz, 0.2M NaCl-D2O) δ (ppm) 8.99 (d, J=5Hz, 4H, α of viologen ), 8.40
(d, J=5Hz, 4H, β of viologen), 4.61 (q, 4H, CH2), 1.55(t, 6H, CH3), MASS (FAB): 214 (M+.)
1H NMR of PV2+(500MHz, 0.2M NaCl-D2O) δ (ppm) 8.98 (d, J=6Hz, 4H, α of viologen ), 8.41
(d, J=6Hz, 4H, β of viologen), 4.56 (t, 4H, CH2), 1.96 (m, 4H, CH2), 0.85(t, 6H, CH3), MS
(FAB): 242 (M+.)
1H NMR of BV2+(300MHz, 0.2M NaCl-D2O) δ (ppm) 9.01 (d, J=6.3Hz, 4H, α of viologen ),
8.44 (d, J=6.3Hz, 4H, β of viologen), 4.60 (t, 4H, CH2), 1.95 (m, 4H, CH2), 1.30 (m, 4H, CH2),
0.85(t, 6H, CH3), MS (FAB): 270 (M+.)
Synthesis of NHV•(PF6)2
A mixture of 4,4’-dipyridyl (2g, 12.8mmol) and 3-bromopropylamine hydrobromide (7g,
52mmol) in CH3CN was refluxed for 3days. . The resulting precipitate was filtered and dissolved
in water. The solution was treated with NaOH solution until the blue color characteristic of
reduced viologen appeared. NH4PF6 was added to the solution to exchange the counter anions.
The resulting solid was filtered, washed with water, THF and dried under vacuum. Yield : 59 %,
(4.25g, 7.56mmol).
1H NMR of NHV2+(300MHz, 0.2M NaCl-D2O) δ (ppm) 9.05 (d, J=6.6Hz, 4H, α of viologen ),
8.47 (d, J=6.6Hz, 4H, β of viologen), 4.71 (t, 4H, CH2), 2.88 (t, 4H, CH2), 2.29(m, 6H, CH3), MS
(FAB): 272 (M+.)
Synthesis of NHDBV•(PF6)2
A mixture of aminopropyl-viologen hydrochloride (185mmg, 0.444mmol) and 2,4,6-collidine
(0.74mL) in water (2mL) was stirred at room temperature. A solution of 2,4-dinitro
fluorobenzene in CH3CN (2mL) was added to the first solution. The reaction was stirred for 20 h
at room temperature. The resulting solid was filtered, washed with water, THF, ether and dried
under vacuum. Yield : 81 %, (243mg, 0.36mmol). Counter ion exchange of the product was
accomplished by treatment with excess NH4PF6.
1H NMR of NHDBV2+ (DMSO-d6, 500MHz) δ (ppm) 9.37 (d, J=6.5Hz, 4H, α of viologen ),
8.85 (t, 2H, Ar), 8.84 (s, 2H, NH), 8.73 (d, J=6.5Hz, 4H, β of viologen), 8.28 (dd, 2H, Ar), 7.27
(d, J=10, 2H, Ar), 4.76 (t, 4H, CH2), 3.67(m, 4H, CH2), 2.36(m, 4H, CH2)
13C NMR (DMSO-d6, 500MHz) δ (ppm) 148.47, 147.86, 147.73, 145.99, 134.98, 130.14,
129.87, 126.30, 123.49, 115.22, 58.972, 29.36.
MS (FAB): 605 (M+H-2PF6)+, 750 (M-PF6)+