complexation of cations, anions, and organic substrates ... · complexation of cations, anions, and...

Complexation of Cations, Anions, and Complexation of Cations, Anions, and Organic Substrates using Modified Organic Substrates using Modified

CyclodextrinsCyclodextrins

Suhash HarwaniUniversity of Iowa

DTSC - ECL28 January 2009

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•2

OutlineOutline

• Background on cyclodextrins• Inner-sphere coordination of LnIII/AnIII

• Synthesis of acid cyclodextrin scaffolds• Binding with LnIII

• Outer-sphere coordination of ClO4-, PO4

3-, and SO42-

• Synthesis cyclodextrin scaffold• Binding studies via ESI-MS• Binding Mode

• Organic substrate binding• Conclusions

•2



•3

CyclodextrinsCyclodextrins

m

m = 1, 2 or 3

Connors, K. A. Chem. Rev., 1997, 97, 1325-1352.•3

O

* O*

OH

OH

OH n

O

HO

OOH

OH

n

n = 6, 7 or 8

upper rim 1° -OH

lower rim 2° -OH

Cyclic molecules consisting of 6, 7, or 8 α-(14) linked D-glucose molecules named α, β, and γ-cyclodextrin



•4

Cyclodextrin PropertiesCyclodextrin Properties

Physicochemical properties• Hydrophobic interior• Hydrogen-bonding lower and upper rims• Cavity Size

αα--cyclodextrincyclodextrin

Connors, K. A. Chem. Rev., 1997, 97, 1325-1352.Harwani, S.; Telford, J. R. Chemtracts, 2005, 18(8), 437-448.Llinares, J. M.; Powell, D.; Bowman-James, K. Coor. Chem. Rev. 2003, 240, 57-75http://geoweb.princeton.edu/research/geochemistry/research/aqueous-sulfate.html

•4


http://geoweb.princeton.edu/research/geochemistry/research/aqueous-sulfate.html


• Primary hydroxyls substituted

• Important Interactions for Binding• H-bonding• Electrostatic Interactions• Vander Waals Interactions• Outer- vs. Inner-sphere coordination

•5

Modifying Cyclodextrin PropertiesModifying Cyclodextrin Properties

Per-6-modified Mono-6-modified



•6

OutlineOutline

•6

• Background on cyclodextrins• Inner-sphere Coordination of LnIII/AnIII


• Outer-sphere Coordination of ClO4-, PO4

3-, and SO42-


• Organic substrate binding



•7

Preorganization for Binding

•7

Delmau, L. H.; Simon, N.; Schwing-Weill, M.-J.; Arnaud-Neu, F.; Dozol, J.-F.; Eymard, S.; Tournois, B.; Böhmer, V.; Grüttner, C.; Musigmannc, C.; Tunayarc, A. Chem. Comm. 1998, 1627-1628. Nitz, M.; Sherawat, M.; Franz, K. J.; Peisach, E.; Allen, K. N.; Imperiali, B. Angew. Chem. Int. Ed.,2004, 43, 3682-3685Nitz, M.; Franz, K. J.; Maglathlin, R. L.; Imperiali, B. ChemBioChem, 2003, 4, 272-276.

OCnH2n+1 4

R

PO

R

O

NH



•8

PerPer--66--modified modified ββ--cyclodextrinscyclodextrins

Ashton, P. R.; Koeniger, R.; Stoddart, J. F.; Alker, D.; Harding, V. D., J. Org. Chem. 1996, 61, 903-908.



•9Ashton, P. R.; Koeniger, R.; Stoddart, J. F.; Alker, D.; Harding, V. D., J. Org. Chem. 1996, 61, 903-908.

Increasing the Denticity of perIncreasing the Denticity of per--66--ethylenediamineethylenediamine----cyclodextrincyclodextrin



•10

Increasing the Denticity of perIncreasing the Denticity of per--66--ethylenediamineethylenediamine----cyclodextrincyclodextrin

DTPA is metal chelating agent - effective at binding lanthanides

•10Lee, H.Y.; Jee, H.W.; Seo, S.M.; Kwak, B.K; Khang, G.; Cho, S.H. Bioconjugate Chem. 2006, 17, 700-706.



•11

Mono-6-modified β-cyclodextrins

O

HOOH

OO

HO

OOH

OH

6

HO

O

HOOH

OO

HO

OOH

OH

6

O

O

HOOH

OO

HO

OOH

OH

6

1. ~1eq Ts-Clpyridine, <5°C1h

excess ethylenediamine

70°C48-60h85-92% yield

K2CO3DMF, 70°C18h81.6% yield

SO2

N

H2N

COOH

NHN

COO- K+

O

HOOH

OO

HO

OOH

OH

6

HN

NH2

8 9

71

2. H2O0.25h35.9% yield



•12

Mono-6-modified β-cyclodextrins

O

HOOH

OO

HO

OOH

OH

6

HN

NH2

8

K2CO3DMF, 70°C18h78.8% yield

excess dansyl chloride1. ~1eq. DTPA dianhydride

DIENDMSO, RT4-5h

O

HOOH

OO

HO

OOH

OH

6

HN

NH

O

HOOH

OO

HO

OOH

OH

6

HN

HN

N

O- Na+

O- Na+

N

O

O

N

O

OO

O- Na+

O- Na+

N

S

O

O

10 11

2. 2-3 eq. NaOH1h34.2% yield



•13

Fluorescence of monoFluorescence of mono--66--ethylenediamineethylenediamine--dansyldansyl----cyclodextrincyclodextrin

• λex = 355nm

• λem = 540-542nm

• Unable to quench the fluorescence with Cu2+ or D-glucose

• No FRET using between tryptophan or Tb3+

• Inclusion of dansyl moiety within the cavity• Distance greater than 10 Å between tryptophan or Tb3+

•13



•14

Fluorescence Emission of Eu3+ with 10

Binding Curve of Eu3+ Titrated with 15

0

0.5

1

1.5

2

2.5

3

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

Equivalents 15

Rel

ativ

e Fl

uore

scen

ce61

5

O

HOOH O

OHO

OOH

OH

6

HN

HN

N

O- Na+

O- Na+

N

O

O

N

O

OO

O- Na+

O- Na+

15

Fluorescence Emission of Eu3+ Titrated with 15

0

0.5

1

1.5

2

2.5

3

580 590 600 610 620 630 640 650Wavelength (nm)

Rel

ativ

e Flu

ores

cenc

e

0 eq. 150.1 eq. 150.2 eq. 150.3 eq. 151 eq. 152 eq. 153 eq. 154 eq. 155 eq. 15



•15

Fluorescence Emission of Tb3+ with 10 O

HOOH

OO

HO

OOH

OH

6

HN

HN

N

O- Na+

O- Na+

N

O

O

N

O

OO

O- Na+

O- Na+

15

Binding Curve of Tb3+ Titrated with 15

0

1

2

3

4

5

6

7

8

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5

Equivalents 15

Rela

tive

Fluo

resc

ence5

45

Fluorescence Emission of Tb3+ Titrated with 15

0

1

2

3

4

5

6

7

520 525 530 535 540 545 550 555 560 565 570Wavelength (nm)

Rel

ativ

e Fl

uore

scen

ce

0 eq. 150.1 eq. 150.33 eq. 151 eq. 152 eq. 153 eq. 155 eq. 15



•16

ESIESI--MS TbMS Tb3+3+ with with 1010

200 400 600 800 1000 1200 1400 1600 1800 2000m/z

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

Rel

ativ

e A

bund

ance

880.38

790.34

961.34381.12288.13

718.33

1042.40671.27509.21

658.26 1123.43 1712.821204.59

616.22144.74 1237.20 1376.33 1780.191609.28 1868.53

[semi-anhydride 15-3H++Tb3++Na+]+



•17

ESIESI--MS GdMS Gd3+3+ with with 1010

200 400 600 800 1000 1200 1400 1600 1800 2000m/z

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

Rel

ativ

e A

bund

ance

1711.39

671.261239.56833.33

995.37 1163.781042.42509.15 1296.92 1467.99798.92569.19488.70 1591.93347.13256.79

1876.91

[semi-anhydride 15-3H++Gd3++Na+]+



•18

OutlineOutline

•18




3-, and SO42-





•19

Importance of Remediating Tetrahedral Importance of Remediating Tetrahedral AnionsAnions

• Concentrations of tetrahedral oxyanions have been increasing in nature (mostly from fertilizers and factories)

• Perchlorate and pertechnetate have been shown compete with iodide uptake with the thyroid gland in mammals

• A major form technetium exists as as pertechnetate anion, TcO4

-

Katayev, E. A.; Ustynyuk, Y. A.; Sessler, J.L. Coor. Chem. Rev. 250 (2006) 3004-3037. •19



•20

Anion ReceptorsAnion Receptors

• Phosphate Binding Protein (Kd ~ 0.8 µM)• Tetraamine spermine in yeast

• Additional anion receptors

Llinares, J. M.; Powell, D.; Bowman-James, K. Coor. Chem. Rev. 2003, 240, 57-75.Medveczky, N.; Rosenberg, H. Biochim. Biophys. Acta 1970, 211, 158-168. •20

Ar = Aryl groups

n=1, NO3- and Cl- F- (~2), SO4

2- (~4.4), HPO42- (~7.4)



•21

Synthesis of modified CyclodextrinSynthesis of modified Cyclodextrin

Goals with functionalization of the upper rim:• Elongate the upper-cyclodextrin binding pocket• Add hydrogen bonding acceptor-donor• Create possible sites for electrostatic interaction

•21



•22

NonNon--covalent Interactions covalent Interactions viavia ESIESI--MSMS

• Soft-ionization technique• Gas phase ESI-MS has been shown to resemble

solution phase well• Unambiguous stoichiometry of complexes formed

•22

Tjernberg, A.; Carno, S.; Oliv, F.; Benkestock, K.; Edlund, P.; Griffiths, W. J.; Hallen, D. Anal. Chem. 2004,76, 4325-4331.Veenstra, T. D. Biophys. Chem. 1999, 79, 63-79.Hofstadler, S. A.; Sannes-Lowery, K. A. Nat. Rev. Drug Discov. 2006, 5, 585-595.



•23

960 965 970 975 980 985 990 995 1000m/z

0

10

20

30

40

50

60

70

80

90

100

Rel

ativ

e A

bund

ance

972.98

989.94

974.00

990.98974.97

1001.86995.35975.96 1002.90997.22992.98979.34 989.10972.21 985.11965.12 968.00960.82

MS of MS of αα--cyclodextrincyclodextrin

[+NH4+]

[+H+]



•24

MS MS αα--cyclodextrin with LiClOcyclodextrin with LiClO44 (1:7)(1:7)

200 400 600 800 1000 1200 1400m/z

0

10

20

30

40

50

60

70

80

90

100

Rel

ativ

e A

bund

ance

979.39

493.31

1085.16

546.17

1191.03

221.10 1298.95599.05 655.14 1404.85758.96331.14147.02 412.31 1459.69866.60

[+Li+]

[+2Li+, 1ClO4-]

[+3Li+, 2ClO4-]



•25

MS of MS of αα--cyclodextrin with KHcyclodextrin with KH22POPO44 (1:7)(1:7)

200 400 600 800 1000 1200 1400m/z

0

10

20

30

40

50

60

70

80

90

100

Rel

ativ

e A

bund

ance

1011.32

446.68 973.03310.73

582.621146.98620.60174.86

718.53348.68

778.40 1320.91892.43 1185.001070.74 1456.81

[+H+]

[+K+]



•26

MS MS αα--cyclodextrin with MgSOcyclodextrin with MgSO44 (1:7)(1:7)

200 400 600 800 1000 1200 1400m/z

0

10

20

30

40

50

60

70

80

90

100

Rel

ativ

e A

bund

ance

972.97

989.95

498.251093.16

558.23324.86 486.80 670.57810.83

465.67 1156.56845.37247.70147.021262.96 1470.63

[+NH4+]

[+H+, Mg2+, SO42-]

[+H+]



•27

200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500m/z

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

Rel

ativ

e A

bund

ance

592.43

613.421183.45

409.36

1225.47

395.36

583.41

389.38 1165.43

571.33 1141.40

205.07 553.33

375.31 627.40 1105.371253.41418.71 677.24

532.35451.79369.35 1045.30 1310.98775.22 979.31511.28 817.21349.12247.05 757.24 925.28

1383.33 1458.30

MS of Cyclodextrin MS of Cyclodextrin 1414

[M +2H+]2+/2

[M + 2H+ + OH - EDA]2+/2

[M + H++ OH - EDA]+

[M +3H+]3+/3

[M + 2H+ + OH - EDA]3+/3

[M +H+]+



•28

MS MS 14 14 with ClOwith ClO44-- (10:1)(10:1)

200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500m/z

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

Rel

ativ

e A

bund

ance

592.42

613.41

409.37

1183.44

1225.47

395.36

583.42

389.35

562.371165.41

1123.39

205.06 553.37

375.34 1105.36627.41418.69 1063.36677.28 1253.44532.37369.34

1045.33 1311.07979.34775.27490.32 961.31817.24349.15247.08 721.221381.12 1482.46



•29


[M + 3H+ + ClO4-] / 2

[M + 2H+ - EDA + OH + ClO4-] / 2

[M + 2H+ + ClO4-]+

[M + 2H+ - EDA + OH + ClO4-]+

200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500m/z

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

Rel

ativ

e A

bund

ance

592.39

613.41

663.38409.35

442.69 583.40

395.361183.41

389.35

562.36 1225.44

553.35

1123.37205.07 375.33 677.27451.88 1283.27

532.35369.29 1105.38523.33

1353.151045.30775.24 979.32511.30 692.16 817.23349.12 925.29247.06 1383.22 1452.83



•30


200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500m/z

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

Rel

ativ

e A

bund

ance

642.32

663.37

592.39442.67

583.40

409.29 562.37553.38 1283.25677.25

389.38 713.261325.28205.05 1183.43

532.34 1123.37375.301063.32979.28775.18 817.20 1425.22

925.21247.06 883.36355.16



•31

MS MS 1414 with ClOwith ClO44-- (1:10)(1:10)

T: + c Full ms [ 150.00-1500.00]

200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500m/z

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

Rel

ativ

e A

bund

ance

642.34

663.37

664.28442.72

592.39

713.30583.36428.63714.24

422.73 553.34409.27 475.98

716.18205.05763.15395.38 532.36 1283.23817.09523.28169.02 1325.23979.30 1183.341021.25 1383.161225.31823.07 1123.33367.12 1437.17901.06206.07 307.06



•32

MS MS 1414 with SOwith SO4422-- (10:1)(10:1)

200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500m/z

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

Rel

ativ

e A

bund

ance

592.40

409.36

613.39

395.37

583.41 1183.43

389.351225.45562.36

553.34

451.88375.32 1165.41627.46205.06 656.24

369.32 532.35 1105.34523.36 1253.39 1353.061045.30775.16 979.30817.23511.21 692.25349.09247.08

1381.09 1498.46



•33

MS MS 14 14 with SOwith SO4422-- (1:1)(1:1)

200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500m/z

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

Rel

ativ

e A

bund

ance

592.41

613.41409.37

395.37

583.42

1183.42

562.35389.351225.46

662.39553.40

1165.40451.84375.29205.05 532.39 677.16369.31

1063.31523.31 1310.98775.21 1045.26979.28692.30 817.18511.26355.19247.07 1383.35 1481.27



•34


200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500m/z

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

Rel

ativ

e A

bund

ance

592.39

613.39

662.35409.35

583.38

395.35

562.39

553.36389.34

441.97 1183.42

532.35375.34 1225.45205.06 369.29

1165.37677.02523.30701.28 1105.39 1281.26775.13511.23 979.29817.12355.24 1323.27925.19247.08 331.12 1365.26 1443.31



•35


200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500m/z

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

Rel

ativ

e A

bund

ance

592.42

641.33

662.38

583.41562.38409.35

553.35395.32

442.00

532.30389.33

523.31205.04 375.30

677.261183.42

722.38451.92 772.22 1123.34 1225.42979.28937.20355.26 1063.24 1281.23247.02 1361.31 1458.80



•36

MS MS 14 14 with POwith PO4433-- (10:1)(10:1)

T: + c Full ms [ 150.00-1500.00]

200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500m/z

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

Rel

ativ

e A

bund

ance

592.41

613.43

1183.46

1225.49

409.35

583.41

1226.50395.36

1165.43562.37

1141.41614.24553.36389.35

205.051105.39 1227.52627.41

677.23 1063.37451.82 532.33 1311.05169.03 1353.07375.33 1045.36979.33523.37 775.26367.13 1354.10817.27678.07 925.29247.01 307.15 1355.17 1429.16



•37


200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500m/z

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

Rel

ativ

e A

bund

ance

592.39

1183.46

613.41

1225.48

409.35

1226.51

583.43395.35

1165.44662.29

1141.41571.34562.37

389.35 1281.16553.38

205.051323.12

441.871105.42375.32 677.25532.37 1063.31169.02 1324.17711.19369.31 523.26 979.30 1354.04367.11 775.27511.25 817.25 961.27901.19 1355.11206.08 331.04 1429.16



•38


200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500m/z

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

Rel

ativ

e A

bund

ance

1183.47

1225.50

592.43613.42

1226.51

1165.45662.31

1123.38583.40 1281.11

409.34

571.36 1323.15553.38395.37

1105.39441.94 1324.18205.05 711.20 1063.37389.33 1353.09532.34375.30 1045.34 1354.09151.05 817.24 979.28451.29 775.24310.67 943.35 1355.13883.21247.02 1437.33



•39


200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500m/z

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

Rel

ativ

e A

bund

ance

1183.46

1225.49

592.43613.42

1226.51

662.29

1165.44

1141.43

583.38 1281.15

571.331323.14409.35 553.36

1105.41711.21

441.931324.14395.41205.03 1063.39532.31310.67

484.51 1045.34174.85 348.74 1353.05979.23817.19756.38212.92 883.26 1383.43247.02 1429.34



•40

Calculation of KCalculation of Kdd from ESIfrom ESI--MSMS

HG

GHK d

0

0

0

0%H

HHGKGH

GGHGBound d

Total

bound

HGH

HG

IIIRBound *%

0*

*H

IIKRGII

IR HHGdo

HGH

HG

H

HGd

HGH

HG

II

HK

RHG

III *

* 00

0

H

HGd

HGH

HG

IGI

HRK

nHIII

GR

*][*'*

*1*

]['

0000

DefinitionsR = response factor = R’ * n

[G]0 = Initial guest (tetrahedral anion) concentration

[H]0 = Initial host (cyclodextrin) concentration

[G] = Amount of free guest (tetrahedral anion) present

[H] = Amount of free host (cyclodextrin) present

IHG = Absolute intensity of HG complex

IH = Absolute intensity of H



•41

Binding with Cyclodextrin Binding with Cyclodextrin 1414

Anion ClO4- SO4

2- PO43-

Charge/Size Ratio 0.21 0.43 0.63

Log Ka 3.8 ± 0.02 3.62 ± 0.04 4.0 ± 0.02

R’ * -8 -1 -4

n * 0.3 2 15



•42

Binding ModesBinding Modes

Anions can bind at numerous positions• Interaction at upper rim through ethylenediamine arms• Interaction at lower rim through hydroxyl groups• Within the cavity (unlikely due to the hydrophobic

nature of the cavity)

•42

+ XO4n- XO4

n-

X(n) = Cl(-1), P(3-), S(2-)



•43

Proton T1 Relaxation TimesT 1 R e la x a tio n V a lu e s : T itra t io n o f C y c lo d e x tr in 6 w ith L iC lO 4

0

0 .5

1

1 .5

2

2 .5

3

2 .5 3 3 .5 4 4 .5 5 5 .5C h e m ic a l S h if t ( p p m )

T1 R

elax

atio

n Ti

me

(sec

)

= 1 : 0 ( [6 ] : [P e r c h lo r a te ]

= 1 : 1 .2 ( [6 ] : [P e r c h lo r a te ]

= 1 : 4 ( [6 ] : [P e r c h lo r a te ]

= 1 : 8 ( [6 ] : [P e r c h lo r a te ]

1/0 *21 T

t eMM

Definitions: Mt = peak intensity at a specified τ valueM0 = peak intensity at full relaxationtau = delay time before the spectrum takenT1 = T1 relaxation value being calculated

O

HOOOH

NH

6

NH3+ I-

T1 Relaxation Values: Titration of 14 with LiClO4

1 : 0 ( [14] : [ClO4-] )

1 : 1.2 ( [14] : [ClO4-] )

1 : 4 ( [14] : [ClO4-] )

1 : 8 ( [14] : [ClO4-] )



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OutlineOutline

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3-, and SO42-





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HostHost--Guest StudiesGuest Studies

2, 3-dihydroxyquinoxaline 2, 3-diaminonaphthalene DHQ DAN

N-(1-pyridyl-methyl)-2-amino-benzoic acidDJ-101

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Analysis of Titration SpectraAnalysis of Titration Spectra

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Compound Cyclodextrin Log Ka (M-1)DAN Native β 2.7 ± 0.1DHQ Native β 4.7 ± 0.1

DJ-101 Native β 3.0 ± 0.1 DJ-101 Per-6-EDA-β (3) 5.4 ± 0.1

Yukihide Shiraishi, Hidefumi Hirai et al. J of Molecular Catalysis A 1999, 139, 149-158.

N

NHO

HO

N

N OH

OH

+N N

OHHO

+



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ConclusionsConclusions• Cation Binding

• Synthesis of novel per-6- and mono-6-modified β-cyclodextrins has been accomplished

• The initial analysis indicates complexation by cyclodextrin 11 (DTPA modified) with Tb3+, Eu3+, and Gd3+

• Fluorescence and MS experiments indicate a 1:1 (Cyclodextrin/LnIII) stoichiometry

• Anion Binding• Characterization of perchlorate, phosphate, and sulfate binding with native α-cyclodextrin and 14 using ESI-MS have been completed

• Binding affinities determined, indicating a minor amount of discrimination• Binding modes analyzed through T1 calculations

• Organic Substrate Binding• Cyclodextrins incorporate DHQ, DAN, and DJ-101 into their hydrophobic

cavities with modest association constants

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AcknowledgementsAcknowledgements

• Professors Jason Telford and Sonya Franklin• Telford Group Members (David, Nate, Heaweon, and

Tony)• Department of Chemistry at the University of Iowa• Funding sources

• PRF• University of Iowa GCSF

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complexation of cations, anions, and organic substrates ... · complexation of cations, anions, and...

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