Supporting Information

© Copyright Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, 2007

I

Dipyrrolyl-functionalized bipyridine-based anion receptors for emission-

based selective detection of dihydrogen phosphate

Patrick Plitt, Dustin E. Gross, Vincent M. Lynch, and Jonathan L. Sessler*

Department of Chemistry and Biochemistry and Institute for Cellular and Molecular Biology, 1 University

Station A5300, University of Texas at Austin, Austin, TX 78712-0165, USA; Fax: +1 512 4717550; Tel: +1

512 4715009; Email: sessler@mail.utexas.edu

II

1H NMR spectroscopic anion recognition studies

The host compounds and the tetrabutylammonium (TBA) salts used in this study were dried

in vacuo overnight at 60 and 50 °C, respectively. Stock solutions of the host molecules were

prepared by dissolving an appropriate amount in DMSO-d6. The concentrations were in the

range between 1.67 and 6.67 mM. To keep the host concentration constant, stock solutions of

the guests were made by dissolving 59 to 61 equivalents of the corresponding TBA salt in the

stock solutions of the hosts leading to guest concentrations in the range of 100 to 400 mM.

The general procedure for the 1H NMR spectroscopic binding studies involved making

sequential additions of the titrant (anionic guest) in question using precision syringes to a

600 µL aliquot of the host stock solution contained in an NMR tube and recording the

spectrum after each addition. The change in the host CH peak (protons on pyridine carbon

C3/C3' of the substituted 2,2'-bipyridine) chemical shift was then plotted as a function of the

concentration of the guest.

Equilibrium constants K were calculated using the software Origin 7.0. It was assumed in

making these calculations that the changes in the chemical shift were due to anion binding. In

other words, equilibrium (a) was considered to lie on the side of dissociation since negligible

spectral changes could be observed when excess of the original counter anion, tetra-n-

butylammonium hexafluorophosphate, was titrated into solutions of the host.1 The program

solves equation 12 iteratively for the equilibrium (b) (G is the guest concentration, δ is the

chemical shift of the proton in question) and provides the parameters K, H (host

concentration), δi (initial δ), and δf (final δ).

m H + n PF6 (a)Hm(PF6)n

m H + n G HmGn (b)

1 An anion affinity constant corresponding to the interaction of the receptors towards hexafluorophosphate could not be determined because no appreciable shift in the various observable signals was seen. For instance, in the case of 2, the pyridine-CH proton resonance shifted 0.006 ppm downfield in the presence of 9 equivalents of TBAPF6. 2 C. S. Wilcox, in Frontiers in Supramolecular Organic Chemistry and Photochemistry, H.-J. Schneider, H. Dürr, Eds.; VCH: Weinheim, 1991.

III

δ = δi+[(δf–δi)/H] [(1/K+H+G)–((1/K+H+G)2–4HG)1/2] (1)

To determine the stoichiometry of the host–guest assembly by 1H NMR in DMSO-d6

sequential additions of titrant (anionic guest as its TBA salt) were made to a 500 µL aliquot of

the host stock solution in DMSO-d6. Job plots were generated by plotting the product of the

host concentration and the chemical shift difference (H × ∆δ) as a function of the molar

fraction of the guest.3 The change in the chemical shift of the bipyridine CH peak was used to

determine the affinity constant in this way.

Selected 1H NMR spectra, binding isotherms, and Job-plots for the titration of 1 and 2

with various anions

5.56.06.57.07.58.08.59.09.510.010.511.011.512.012.5

Fig. 1a Titration of 1 (3.33 mM) with TBA-Cl (top to bottom: 0, 0.20, 0.98, 1.94,

3.04 equivalents).

0,000 0,006 0,0128,7

9,0

9,3

9,6

[Cl]/M

δ

0,0000

0,0001

0,0002

0,0003

0,0004

0,0005

0,0006

0,0007

0,0008

0,0009

0,0010

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0

[Cl] / ([Cl] + [1])

[1]*

∆δ

3 K. A. Connors, Binding Constants; John Wiley & Sons: New York, 1987, p.24.

IV

Fig. 1b Left: Binding isotherm for the titration of 1 (3.33 mM) with TBA-Cl; right: Job plot

for 1 and TBA-Cl ([1] + [Cl] = 3.33 mM).

5.56.06.57.07.58.08.59.09.510.010.511.011.512.0

Fig. 2a Titration of 1 (3.33 mM) with TBA-Br (top to bottom: 0, 0.20, 0.98, 1.94,

3.04 equivalents).

0,000 0,005 0,010 0,015 0,020 0,025

8,80

8,85

8,90

8,95

9,00

9,05

9,10

9,15

δ

[Br]/M

0,0000

0,0001

0,0002

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0

[Br] / ([Br] + [1])

[1]*

∆δ

Fig. 2b Left: Binding isotherm for the titration of 1 (3.33 mM) with TBA-Br; right: Job plot

for 1 and TBA-Br ([1] + [Br] = 3.33 mM).

5.56.06.57.07.58.08.59.09.510.010.511.011.512.0

V

Fig. 3a Titration of 1 (3.33 mM) with TBA-CN (top to bottom: 0, 0.20, 0.98, 1.94,

3.04 equivalents).

0,000 0,005 0,010 0,015 0,020 0,025

8,8

8,9

9,0

9,1

9,2

9,3

δ

[CN]/M

0,0000

0,0001

0,0002

0,0003

0,0004

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0

[CN] / ([CN] + [1])

[1]*

∆δ

Fig. 3b Left: Binding isotherm for the titration of 1 (3.33 mM) with TBA-CN; right: Job plot

for 1 and TBA-CN ([1] + [CN] = 3.33 mM).

6.06.57.07.58.08.59.09.510.010.511.011.512.012.513.013.5 Fig. 4a Titration of 1 (3.33 mM) with TBA-benzoate (OBz) (top to bottom: 0, 0.20, 0.98,

1.94, 3.04 equivalents).

VI

-0,002 0,000 0,002 0,004 0,006 0,008 0,010 0,012 0,014 0,0168,7

8,8

8,9

9,0

9,1

9,2

9,3

9,4

9,5

9,6

δ

[OBz]/M

0,0000

0,0002

0,0004

0,0006

0,0008

0,0010

0,0012

0,0014

0,0016

0,0018

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0

[OBz] / ([OBz] + [1])

[1]*

∆δ

Fig. 4b Left: Binding isotherm for the titration of 1 (3.33 mM) with TBA-benzoate; right: Job

plot for 1 and TBA-benzoate ([1] + [OBz] = 3.33 mM).

6.06.57.07.58.08.59.09.510.010.511.011.512.012.5

Fig. 5a Titration of 2 (3.33 mM) with TBA-Cl (top to bottom: 0, 0.20, 0.98, 1.94,

3.04 equivalents).

-0,002 0,000 0,002 0,004 0,006 0,008 0,010 0,012 0,014 0,0168,8

9,0

9,2

9,4

9,6

9,8

δ

[Cl]/M

0,0000

0,0002

0,0004

0,0006

0,0008

0,0010

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0

[Cl] / ([Cl] + [2])

[2]*

∆δ

VII

Fig. 5b Left: Binding isotherm for the titration of 2 (3.33 mM) with TBA-Cl; right: Job plot

for 2 and TBA-Cl ([2] + [Cl] = 3.33 mM).

6.06.57.07.58.08.59.09.510.010.511.011.512.012.5

Fig. 6a Titration of 2 (3.33 mM) with TBA-Br (top to bottom: 0, 0.20, 0.98, 1.94,

3.04 equivalents).

0,000 0,005 0,010 0,015 0,020 0,0258,90

8,95

9,00

9,05

9,10

9,15

9,20

9,25

9,30

9,35

δ

[Br]/M

0,0000

0,0001

0,0002

0,0003

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0

[Br] / ([Br] + [2])

[2]*

∆δ

Fig. 6b Left: Binding isotherm for the titration of 2 (3.33 mM) with TBA-Br; right: Job plot

for 2 and TBA-Br ([2] + [Br] = 3.33 mM).

VIII

6.06.57.07.58.08.59.09.510.010.511.011.512.012.513.013.514.0

Fig. 7a Titration of 2 (3.33 mM) with TBA-benzoate (OBz) (top to bottom: 0, 0.20, 0.98,

1.94, 3.04 equivalents).

-0,002 0,000 0,002 0,004 0,006 0,008 0,010 0,012 0,014 0,016

8,9

9,0

9,1

9,2

9,3

9,4

9,5

9,6

9,7

δ

[OBz]/M

0,0000

0,0002

0,0004

0,0006

0,0008

0,0010

0,0012

0,0014

0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0

[OBz] / ([OBz] + [2])

[2]*

∆δ

Fig. 7b Left: Binding isotherm for the titration of 2 (3.33 mM) with TBA-benzoate; right: Job

plot for 2 and TBA-benzoate ([2] + [OBz] = 3.33 mM).

IX

Dihydrogen phosphate recognition studied by fluorescence spectroscopy

The preparation of the stock solutions of the host (H) and guest (G) in DMSO followed a

procedure similar to that used to prepare those for the NMR spectroscopic titrations. The host

concentration was kept constant. Binding isotherms were generated by plotting the relative

fluorescence intensity (F/F0) versus the concentration of the guest. Association constants (K)

were calculated by curve-fitting with Origin 7.0 using the following equation (eq. 2, where F

refers to the fluorescence intensity; F0 is the initial fluorescence intensity of the receptor in

question; kf and kH are proportionality constants of the bound complex and the receptor,

respectively; G is the concentration of the guest molecule).4

F / F0 = (1 + kf/kH K G) / (1 + K G) (2)

0,0 0,5 1,0 1,5 2,0

0

100000

200000

300000

400000

500000

600000

700000

F (

a.u.

)

[1]/uM

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

[H2PO4] / ([H2PO4]+[1])

[1]*

(F0-

F)

Fig. 8a Left: Lambert-Beer plot for 1; right: Job plot for 1 and TBA-H2PO4 ([1] + [H2PO4] =

0.5 µM).

600 700 800

600000

1200000

1800000

F (a

.u.)

λ/nm

0,000000 0,000004 0,000008 0,000012

0,6

0,7

0,8

0,9

1,0

F /

F0

[H2PO4]/M

4 K. A. Connors, Binding Constants; John Wiley & Sons; New York, 1987, p.341.

X

Fig. 8b Left: Titration of 1 (1 µM in DMSO) with 0 to 9.5 equivalents TBA-H2PO4; right:

Binding isotherm for the titration of 1 (1 µM) with TBA-H2PO4.

XI

Fluoride recognition studied by UV-Vis absorption

Tetrabutylammonium fluoride was not dried prior to use and contained ca. 6 equivalents of

water, as determined from 1H NMR spectroscopic integrations carried out in DMSO-d6. Stock

solutions of the host and guest in DMSO were prepared as described above for the NMR and

fluorescence titrations thereby allowing the host concentration to be kept constant during the

addition of the guest. Binding isotherms were generated by plotting the difference in the

absorption value (|A–A0|) versus the concentration of the guest. Association constants (K)

were calculated by curve-fitting the binding isotherms to equation 3, where A refers to the

absorption, A0 is the initial absorption of the host, B is a proportionality constant, and G is the

concentration of the guest.5

|A–A0| = B G / (1 + K G) (3)

300 400 500 600

0.0

0.2

0.4

A

λ / nm

0.00000 0.00005 0.00010 0.00015-0.01

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

∆A @

352

nm

[F] / M

Fig. 9 Left: Changes in the spectrum of 1 (10 µM in DMSO) seen upon the addition of TBA-

F (0 to 17 equiv.); right: Plot of the difference in absorption at 352 nm vs. [F–].

5 K. A. Connors, Binding Constants; John Wiley & Sons; New York, 1987, p.141ff.

XII

Microcalorimetric studies

Solutions were prepared as above to produce the concentrations indicated below. The guest

solutions were ca. 15 fold more concentrated than the corresponding host solutions.

Isothermal titration calorimetric (ITC) studies were carried out at 298 K in dry DMSO. In all

cases a background titration (dilution of guest) was subtracted from the host to guest titration.

Thermodynamic data (∆H, ∆S and ∆G), stoichiometry (N), and association constants (Ka)

were obtained using the one_sites model in Origin 7.0, provided by MicroCal, or by simple

calculation in the case of ∆G.

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.00.0

0.1

0.2

-2

0

2

4

0 50 100 150

Time (min)

µcal

/sec

Data: pp357l_NDHModel: OneSitesChi^2/DoF = 7.008N 1.11 ±0.032K 416 ±22∆H 405.1 ±15.9∆S 13.3

Molar Ratio

kcal

/mol

e of

inje

ctan

t

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0-1.5

-1.0

-0.5

0.0

-30

-20

-10

0

0 50 100 150

Time (min)

µcal

/sec

Data: pp357h_NDHModel: OneSitesChi^2/DoF = 31.62N 1.11 ±0.0063K 1.56E3 ±30∆H -1604 ±13.1∆S 9.23

Molar Ratio

kcal

/mol

e of

inje

ctan

t

Fig. 10 Isothermal heat changes produced upon the addition of guest salt to receptor 1

(2.8 mM in DMSO) and below a fit to one_sites model in Origin 7.0. Left: TBA-Cl (in

DMSO); right: TBA-OBz (in DMSO).

XIII

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

0.0

0.1

0.2

0.3

0.4

0

2

4

60 50 100 150

Time (min)

µcal

/sec

Data: pp358a_NDHModel: OneSitesChi^2/DoF = 4.647N 1.05 ±0.0070K 1.07E3 ±24∆H 489.5 ±4.39∆S 15.5

Molar Ratio

kcal

/mol

e of

inje

ctan

t

0.0 0.5 1.0 1.5 2.0 2.5 3.0

-1.0

-0.8

-0.6

-0.4

-0.2

0.0-10

-8

-6

-4

-2

0

0 50 100 150

Time (min)

µcal

/sec

Data: pp358c_NDHModel: OneSitesChi^2/DoF = 39.13N 1.09 ±0.0034K 4.48E3 ±1.0E2∆H -1032 ±4.45∆S 13.2

Molar Ratio

kcal

/mol

e of

inje

ctan

t

Fig. 11 Isothermal heat changes see upon the addition of guest salt to receptor 2 (2.9 mM in

DMSO) and below a fit to one_sites model in Origin 7.0. Left: TBA-Cl (in DMSO); right:

TBA-OBz (in DMSO).