Table 1 Association constants (Ka, M−1) of naphthotubes 5a and 5b with G1–G7 in phosphate buffer (50 mM, pH = 7.4 or 12, H2O/D2O = 9/1) at 298 K as determined by 1H NMR titrationsa.

From: Switchable bifunctional molecular recognition in water using a pH-responsive Endo-functionalized cavity

Guest

Host

Ka (pH 7.4)

Ka (pH 12)

Ratiob

G1

5a

(4.8 ± 0.6) × 103

(1.6 ± 0.2) × 102

30/1

5b

(3.8 ± 0.7) × 103

(4.9 ± 0.7) × 102

8/1

G2

5a

(8.4 ± 0.1) × 104 c

(2.4 ± 0.4) × 103 c

35/1

5b

(3.7 ± 0.1) × 105 c

(1.5 ± 0.2) × 104 c

25/1

G3

5a

(1.9 ± 0.3) × 104

(6 ± 1) × 102

32/1

5b

(1.1 ± 0.1) × 105

(1.8 ± 0.1) × 103

61/1

G4

5a

(8.6 ± 0.2) × 103 c

(5 ± 1) × 101

172/1

5b

(1.7 ± 0.2) × 104 c

(9 ± 2) × 101

189/1

G5

5a

–d

-d

-d

5b

(2.0 ± 0.4) × 101

(5.9 ± 0.9) × 103

1/295

G6

5a

(7 ± 1) × 101

(7.0 ± 0.6) × 102

1/10

5b

(1.0 ± 0.1) × 102

(1.6 ± 0.1) × 103

1/16

G7

5a

(1.0 ± 0.1) × 103

(5.6 ± 0.7) × 103

1/6

5b

(2.0 ± 0.4) × 103

(4.0 ± 0.4) × 104

1/20

  1. aThe data were averaged from three independent titrations.
  2. bRatio = Ka (pH 7.4)/Ka (pH 12).
  3. cThese association constants were determined by ITC titrations.
  4. dThe association constants could not be obtained due to severe aggregation in the host–guest mixture.
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