Evidence for Partially Bound States in Cooperative Molecular

Feb 23, 2009 - Constants for H-Bond Interactions, K1 and K2 (M-1), in the. Complexes Formed Between Porphyrin 3 and Ligands 4b and 4d at 298 Ka solven...
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Evidence for Partially Bound States in Cooperative Molecular Recognition Interfaces [J. Am. Chem. Soc., 2008, 130, 17718-17725] [J. Am. Chem. Soc. 2008, 130, 17718]. Elena Chekmeneva, Christopher A. Hunter,* Martin J. Packer, and Simon M. Turega Pages 17722-17723: Equations 3, 4, 6 and 8 relating to the analysis of the sequential binding equilibria are corrected below. The numerical values of the stepwise association constants and effective molarities reported in Tables 5 and 6 are corrected below. Qualitatively, the results are similar to those in the original publication, and the main conclusions are not affected. However, the overall association constant estimated for the doubly H-bonded complex in Table 6 is always larger than the value estimated for a singly H-bonded complex, even when the most populated state of the doubly H-bonded complex is the singly H-bonded species. Kobs ) K0(1 + K1)

(3)

Kobs ) K0(1 + K1 + K1K2)

(4)

K1 Kobs - K0 ) 4KH 4K0KH

(6)

8K2 8(Kobs - K0 - K0K1) ) 6KH 6K0K1KH

(8)

EM1 )

EM2 )

Table 5. Effective Molarities, EM (M), Sequential Equilibrium

Constants for H-Bond Interactions, K1 and K2 (M-1), in the Complexes Formed Between Porphyrin 3 and Ligands 4b and 4d at 298 Ka 3 · 4b

3 · 4d

solvent

toluene TCE DCM CHCl3 acetone

K1

EM1

K2

EM2

14 3 5 1 5

0.1 0.2 0.7 0.7 0.9

14 b b b b

0.8 b b b b

a Errors are EM1 ( 60%, K1 ( 40%, EM2 ( 80% and K2 ( 60%. The values of K2 are within experimental error of zero, and so the second H-bond does not confer a measurable additional stability on the complex.

b

Table 6. Estimated Overall Association Constants for Complexes Formed Between Porphyrin 3 and Ligand 4d That Make Either One or

Two H-bonds (M-1) and Populations of Partially Bound States Assuming EM1 ) EM2 ) 0.5 M singly H-bonded complex

doubly H-bonded complex

solvent

toluene TCE DCM CHCl3 acetone

Kest

zero H-bonds (%)

one H-bond (%)

Kest

zero H-bonds (%)

one H-bond (%)

two H-bonds (%)

4.2 × 104 2.7 × 103 5.3 × 103 1.5 × 103 4.3 × 102

1 8 13 35 16

99 92 87 65 84

8.2 × 105 1.0 × 104 1.5 × 104 2.5 × 103 1.0 × 103

0 4 8 32 11

10 46 56 58 59

90 50 35 10 29

JA900730Z 10.1021/ja900730z Published on Web 02/23/2009 3786

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J. AM. CHEM. SOC. 2009, 131, 3786

10.1021/ja900730z CCC: $40.75  2009 American Chemical Society