SUPRAMOLECULAR CHEMISTRY OF BETA– AND GAMMA– … · SUPRAMOLECULAR CHEMISTRY OF ... important to understand and control the aqueous supramolecular assembly of polymers at the

SUPRAMOLECULAR CHEMISTRY OF

BETA– AND GAMMA–

CYCLODEXTRIN DIMERS

Huy Tien Ngo

Thesis submitted for the degree of

Doctor of Philosophy

in

The University of Adelaide

School of Chemistry and Physics

October 2010

Huy Tien Ngo Chapter 4

135

CHAPTER 4

CONTROLLED SUPRAMOLECULAR

POLYMER ASSEMBLY OF 1-NAPHTHALENE

LABELLED POLY(ACRYLATE)S BY LINKED

- AND -CYCLODEXTRIN DIMERS


136

4.1. Introduction

4.1.1. Controlled Supramolecular Assembly of Polymers and Hydrogels

Hydrogels are water-swollen polymeric networks containing cross-links of chemical or

physical nature. Research on new polymer hydrogels has become of increasing interest in

recent years because of potential applications in drug delivery, biosensing, tissue

engineering, functional nanodevices and biological coating technologies.1-6 In addition to

their biocompatibility characteristics, hydrogels can be tailored to be responsive to various

environmental stimuli during their development for different applications. It is therefore

important to understand and control the aqueous supramolecular assembly of polymers at

the molecular and macroscopic levels in order to produce hydrogels which exhibit

predictable and controllable character and which constitute new materials.

Figure 4.1 shows some possible interactions of substituted polymers in aqueous

solution. The substitution of hydrophobic entities (such as a 1-naphthyl group shown in A)

onto water soluble polymers solubilises these hydrophobes and facilitates studies of their

aggregation and complexation processes in aqueous solutions, which would normally be

otherwise inaccessible. This is likely to result in hydrophobe association and polymer

aggregation (B), enhancement of the viscosity of the polymer solution and possibly

formation of hydrogels. The addition of single water soluble hydrophobe receptors, such as

cyclodextrins (CDs) may lead to polymer disaggregation (C), which can be reversed in the

presence of competitive complexation by a second free hydrophobe species.7-9 On the other

hand, the addition of hydrophobe receptors substituted on water soluble polymers may

produce new entanglement and aggregation through hydrophobe–hydrophobe receptor

association (D) which leads to increased viscosity. This is exemplified by the 1:1 molar

ratio mixture of either CD or CD 3% randomly substituted poly(acrylate)s (PAA) with

octadecyl 3% substituted PAA,8,9 or with adamantyl 3% substituted PAA,10,11 which

resulted in up to a 100-fold increase in solution viscosity by comparison to that of the

individual polymers separately. Furthermore, the addition of dimeric hydrophobe receptors

is likely to lead to (dimeric hydrophobe receptor)(hydrophobe)2 complexation (E) which

can result in stronger polymer association and enhanced viscosity. For example, the

addition of a terephthalimide linked CD dimer to solutions of adamantyl-containing N,N’-

dimethylacrylamide or N-isopropylacrylamide copolymers increased the viscosity of the

solution dramatically to form stable gels within seconds.12 For these interactive systems


137

control of the assembly process can be achieved in many ways such as either changing the

substituents or the extent of substitution, varying the host–guest molar ratio, adjusting the

tether length between polymer backbone and substituents, and changing polymer

concentration, ionic strength, pH or temperature.13-15

A B

C

D

E

hydrophobe

polymer backbone

hydrophobeassociation

hydrophobereceptor

hydrophone - single hydrophobe receptor association

hydrophone - single hydrophobe receptor association

hydrophone - bis hydrophobe receptor association

Figure 4.1. Various interactions of water soluble substituted polymers in water.


138

4.1.2. Fluorescent Polymers

While the association of aliphatic hydrophobe substituted polymers is evident at the

macroscopic level through increased polymer viscosity, it is only through studies at the

molecular level that the detailed nature of this association may be understood in terms

of specific hydrophobe–hydrophobe or hydrophobe–receptor interactions. Thus, the

interactions between aromatic hydrophobe pairs in substituted polymers, which are

generally through intra- and inter-polymer – stacking, as exemplified by

anthracene,16 naphthalene17-24 or pyrene25-35 (Figure 4.2) are often evident through

changes in their UV–vis spectra and larger changes in their fluorescence spectra as a

consequence of exciton coupling. Furthermore, the hydrophobe–receptor interactions

may also lead to changes in the UV–vis or fluorescence spectra of the fluorophores,

which allow their quantification by spectrophotometric methods, such as steady–state

or time–resolved fluorescence spectroscopy.24,36-38

anthracene naphthalene pyrene

E-stilbene

NN

E-azobenzene

XNH2

RXNH2

XNH2 XNH2

RXNH2

Z-stilbene

N N

Z-azobenzeneR XNH2 R XNH2

Figure 4.2. Some aromatic hydrophobic amines suitable for substitution onto water soluble

polymers where R and X represent a variety of substituents.

Other hydrophobes such as azobenzene and stilbene (Figure 4.2) have also been

substituted onto polymers, and their light-responsive photoisomerisation used to actively

control the supramolecular assembly.39,40 It was shown that photoirradiation with UV or

visible light caused repetitive changes in the viscosity of a mixture of CD substituted

PAA (PAACD) and azobenzene substituted PAA (PAAC12Azo), consistent with the

azobenzene moiety photoisomerising from the Z- form to the E- form and vice versa.39


139

4.1.3. Aims of This Study

The research described in this chapter aims to extend previous understanding in the

control of the supramolecular polymer assembly in water through the interactions of

hydrophobic modified poly(acrylate)s (PAAs) and -, - and -cyclodextrin either in their

free state or as substituents in PAA.7-11,13-15 The current study involves the preparation of

two new 3% randomly substituted 1-naphthyl-sulfonamide poly(acrylate)s with either a

diaminoethyl tether (PAA1NSen) or diaminohexyl tether (PAA1NShn) linking the 1-

naphthyl substituents and the polymer backbone (Figure 4.3).

The host–guest complexation between the 1-naphthyl-sulfonamide substituents of

PAA1NSen and PAA1NShn and the cyclodextrin hosts, CD and CD as well as their

succinamide–linked dimers, 33CD2suc, 66CD2suc, 33CD2suc and 66CD2suc (Figure

4.3) is investigated at the macroscopic level by rheology as well as at the molecular level

by 2D 1H NOESY NMR and fluorescence spectroscopy.

The experiments are expected to provide insight into the factors influencing

fluorescence properties, the impact of polymer substituent tether length, as well as the size

and geometry of the CD and CD dimers on the host–guest complexation behaviour and

the viscosity of the 1-naphthalene sbustituted poly(acrylate) solutions.

CO2- CO2

- CO2-

OHN

SO O

HN

O

OHHO

HO

O

n

1

234

56

=

CD, n = 7CD, n = 8

HN

O

O

NH

HN

O

O

NH

C6A C6A

C3A C3A

n = 7, 66CD2suc 33CD2sucn = 8, 66CD2suc 33CD2suc

m

PAA1NSen, m = 2PAA1NShn, m = 6(A)

(B)

(C)

Figure 4.3. Schematic structures of (A) PAA1NSen and PAA1NShn; (B) CD and CD;

and (C) succinamide–linked CD and CD dimers.


140

4.2. 1-Naphthalene Randomly Substituted Poly(Acrylate)s

4.2.1. Synthesis

The preparation of the new 3% randomly substituted N-(2-aminoethyl)-1-naphthyl-

sulfonamide and N-(6-aminohexyl)-1-naphthyl-sulfonamide poly(acrylate)s, PAA1NSen

and PAA1NShn, required the preparation of 4-nitrophenyl naphthalene-1-sulfonate,

1NSNP, from 1-naphthalenesulfonyl chloride and 4-nitrophenol in dichloromethane by a

method similar to that reported in the literature.41 Treatment of 1NSNP with either 1,2-

diaminoethane in dichloromethane or 1,6-diaminohexane in N,N-dimethylformamide

afforded N-(2-aminoethyl)-1-naphthyl-sulfonamide, 1NSen, and N-(6-aminohexyl)-1-

naphthyl-sulfonamide, 1NShn, in moderate yields. A literature method7,8 was then adapted

to prepare the new 3% randomly substituted PAA1NSen and PAA1NShn in 80–90% yield

(Figure 4.4).

CO2- CO2

- CO2-

OHN

SO

OHN

SO O

Cl

S

O

O

NO2O

4-nitrophenol

H2N

S

O

O

NH

1,2-diaminoethane/DCMEt3N, DCM

or 1,6-diaminohexane/DMF1.

2.HC

H2C

COOH n

+2. NaOH

1. 60 oC/NMP, DCC 3%

H2N

S

O

O

NH

m

m

m

PAA1NSen, m = 2PAA1NShn, m = 6

1NSen, m = 21NShn, m = 6

1NSNP

Figure 4.4. Synthetic scheme for preparation of 3% randomly substituted PAA1NSen and

PAA1NShn.

The succinamide–linked CD and CD dimers, 33CD2suc, 66CD2suc, 33CD2suc

and 66CD2suc were synthesised as reported previously42 and in Chapter 3.43


141

4.2.2. 1H NMR Spectra

The 1H NMR (300 MHz) spectra of 1NSNP, 1NSen and 1NShn in DMSO-d6 are shown

in Figure 4.5 and those of PAA, PAA1NSen and PAA1NShn in D2O are shown in Figure

4.6. The degree of substitution at the PAA carboxyl groups by 1-naphthyl-sulfonamide was

determined to be 3.0 ± 0.3 % from the 1H NMR spectra (Figure 4.6) according to the

method reported previously in the literature.7

Figure 4.5. 1H NMR (300 MHz) spectra of 1NSNP, 1NSen and 1NShn in DMSO-d6.


142

CO2- CO2

- CO2-

OHN

SO O

HNm

PAA1NSen, m = 2PAA1NShn, m = 6

Figure 4.6. 1H NMR (300 Mz) spectra of PAA and 3% substituted PAA1NSen and

PAA1NShn in D2O.


143

4.2.3. Photophysical Properties

Typical UV–vis absorbance and fluorescence spectra were recorded for ~0.013 wt%

~0.0033 wt% solutions of PAA1NSen and PAA1NShn, respectively and are shown in

Figure 4.7. The concentrations of both the 1NSen and 1NShn substituents were calculated

to be 4.0 × 10-5 and 1.0 × 10-5 mol dm-3 for the UV–vis and fluorescence spectra,

respectively, according to section 5.4.2.1. The variation of tether length linking the 1-

naphthyl substituents and the polymer backbone from two methylene groups in

PAA1NSen to six methylene groups in PAA1NShn appears to reduce the intensity of both

the UV–vis absorbance and emission of the 1-naphthyl groups. The fluorescence of

PAA1NShn appears to be quenched significantly as the tether length increases, consistent

with increased mobility of the 1-naphthyl groups as well as their increased exposure to the

bulk water molecules.

Figure 4.7. UV–vis absorbance spectra (left ordinate, blue lines) and relative fluorescence

spectra (right ordinate, red lines) of 3% substituted PAA1NSen (solid lines) and

PAA1NShn (dashed lines) in pH 7.0 phosphate buffer (I = 0.10 mol dm-3). The

concentrations of the 1-naphthyl substituents are 4.0 × 10-5 and 1.0 × 10-5 mol dm-3 for

UV–vis and fluorescence, respectively.

0

100

200

300

400

500

0

1,000

2,000

3,000

4,000

5,000

6,000

250 300 350 400 450

Rel

ativ

e flu

ores

cenc

e (a

.u.)

Mol

ar a

bsor

ptio

n (m

ol-1

dm3

cm-1

)

Wavelength (nm)


144

4.3. Rheological Determination of Viscosity

The host–guest interactions at the macroscopic level between the 1NSen and 1NShn

substituents on the poly(acrylate)s, PAA1NSen and PAA1NShn, and CD, CD and

their linked dimers, 33CD2suc, 33CD2suc, 66CD2suc and 66CD2suc, are expected

to affect the zero–shear viscosities of the solutions. Rheological measurements were

carried out on 5 wt% aqueous solutions of PAA1NSen and PAA1NShn alone and in the

presence of a 1:1 molar ratio of each of the CD hosts at pH 7.0 and [NaCl] = 0.10 mol

dm-3.

The variations of the viscosities of the five PAA1NSen and the five PAA1NShn

solutions with shear rate are shown in Figures 4.8 and 4.9. The variations of the

viscosities of PAA1NSen/CD, PAA1NSen/CD, PAA1NShn/CD and

PAA1NShn/CD solutions are very similar to those of PAA1NSen and PAA1NShn

solutions alone over the shear rate range studied, and thus are not shown. The zero–

shear viscosity variations, corresponding to the viscosities extrapolated from those

observed at the lowest shear rates, are shown graphically and numerically in Figure

4.10 and its caption.

Figure 4.8. Viscosity variations with shear rate of 5 wt% aqueous solutions of PAA1NSen

and PAA1NShn alone and in the presence of 66CD2suc and 66CD2suc at pH 7.0 and

[NaCl] = 0.10 mol dm-3 at 298.2 K. The concentrations of the CD and CD substituents in

the linked dimers are equal to those of the 1NSen or 1NShn poly(acrylate) substituents.

0.01

0.02

0.05

0.1

1 10 100 1000

PAA1NShn+66CD2suPAA1NShn+66CD2suPAA1NShnPAA1NSen+66CD2suPAA1NSen+66CD2suPAA1NSen

Shear Rate [1/s]

Vis

cosi

ty [P

as]

c c

c c


145

Figure 4.9. Viscosity variations with shear rate of 5 wt% aqueous solutions of PAA1NSen and PAA1NShn alone and in the presence of 33CD2suc and 33CD2suc at pH 7.0 and [NaCl] = 0.10 mol dm-3 at 298.2 K. The concentrations of the CD and CD substituents in the linked dimers are equal to those of the 1NSen or 1NShn poly(acrylate) substituents.

Figure 4.10. Zero–shear viscosities of 5 wt% aqueous solutions of PAA1NSen (blue column) and PAA1NShn (red column) alone and in the presence of 33CD2suc, 33CD2suc, 66CD2suc and 66CD2suc at pH 7.0 and [NaCl] = 0.10 mol dm-3 at 298.2 K. The concentrations of the CD and CD substituents in the linked dimers are equal to those of the 1NSen or 1NShn poly(acrylate) substituents. A) PAA1NSen (0.0147) and PAA1NShn (0.0172); B) PAA1NSen/33CD2suc (0.0175) and PAA1NShn/33CD2suc (0.0206); C) PAA1NSen/33CD2suc (0.0159) and PAA1NShn/33CD2suc (0.0242); D) PAA1NSen/66CD2suc (0.0156) and PAA1NShn/66CD2suc (0.0315); E) PAA1NSen/66CD2suc (0.0164) and PAA1NShn/66CD2suc (0.0263), where the zero–shear viscosities (Pa·s) are shown in brackets.

0.01

0.02

0.05

0.1

1 10 100 1000

PAA1NShn+33CD2suPAA1NShn+33CD2suPAA1NShnPAA1NSen+33CD2suPAA1NSen+33CD2suPAA1NSen

Shear Rate [1/s]

Vis

cosi

ty [P

as]

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

A B C D E

Vis

cosi

ty [P

a·s]

c c

c c


146

The viscosities of both PAA1NSen and PAA1NShn solutions alone (Figure 4.8) show

little variation with shear rate, consistent with very little or weak or both inter–polymer

strand cross–linking occurring in these solutions. The viscosity of PAA1NSen solution

(0.0147 Pa·s) is slightly smaller than that of PAA1NShn solution (0.0172 Pa·s), consistent

with the shorter ethyl tether of PAA1NSen restricting – association to a greater extent

than the longer hexyl tether of PAA1NShn. These values are similar to the viscosity of a 5

wt% solution of 3% substituted dodecyl poly(acrylate) (PAAC12), but about four orders of

magnitude smaller than that of a 5 wt% solution of 3% substituted octadecyl

poly(acrylate)s (PAAC18).13 This suggests that the intermolecular – interaction between

the 1-naphthyl substituents is of similar strength to hydrophobic association between the

dodecyl groups but much weaker than that between the octadecyl groups.

The viscosities of the PAA1NSen and PAA1NShn solutions in the presence of all four

linked CD and CD dimers (Figures 4.8 & 4.9) also show very little variation with shear

rate, consistent with little inter–strand cross–linking, similar to that occurring in

PAA1NSen and PAA1NShn solutions alone. The zero–shear viscosities of the PAA1NSen

solutions containing CD and CD dimers increase in the sequence of PAA1NSen

(0.0147) < PAA1NSen/66CD2suc (0.0156) < PAA1NSen/33CD2suc (0.0159) <

PAA1NSen/66CD2suc (0.0164) < PAA1NSen/33CD2suc (0.0175) (blue bars A, D, C, E,

B, Figure 4.10). Overall the increases in viscosity of PAA1NSen solutions containing CD

dimers over PAA1NSen solution alone are small, consistent with very little additional

cross–linking occurring through 1-naphthyl complexation by the CD dimers, which is

restricted by the short ethyl tether length. Most of the complexation is likely to occur

through single interaction between 1-naphthyl and a CD dimer (Figures 4.11a and 4.11b).

The zero–shear viscosities of the longer tether PAA1NShn solutions containing CD

and CD dimers increase in the sequence PAA1NShn (0.0172) < PAA1NShn/33CD2suc

(0.0206) < PAA1NShn/33CD2suc (0.0242) < PAA1NShn/66CD2suc (0.0263) <

PAA1NShn/66CD2suc (0.0315) (red bars A, B, C, E, D, Figure 4.10). The 1.2 to 1.8-fold

increase in viscosity of PAA1NShn/(CD dimer) solutions over PAA1NShn solution alone

are consistent with additional cross–linking caused by complexation of the 1NShn

substituents by the CD dimers (Figures 4.11c and 4.11d). This is consistent with the longer

hexyl tether allowing inter–strand complexation to form extra cross–links between polymer

strands. In addition, the larger increases in viscosity caused by 66CD2suc and 66CD2suc


147

are consistent with the geometry of the 6,6–linked dimers favouring cross–linking over the

3,3–linked dimers. The highest viscosity of PAA1NShn/66CD2suc solution is consistent

with the wide rim of CD being the best fit for complexing the 1-naphthyl group.

CO2-

CO2-

CO2-

O

NH

SO2

NH

PAA1NSen orPAA1NShn

CO2-

CO2-

CO2-

O

NH

SO2

NH

-O2C

-O2C

-O2C

O

NH

O2S

HN

CO2-

CO2-

CO2-

O

NH

SO2

NH

-O2C

-O2C

-O2C

O

NH

O2S

HN

-O2C

-O2C

-O2C

O

NH

O2SHN CO2

-

CO2-

CO2-

O

NH

SO2

NH-O2C

-O2C

-O2C

O

NH

O2SHN

CO2-

CO2-

CO2-

O

NH

SO2

NH

-O2C

-O2C

-O2C

O

NH

O2SHN

CO2-

CO2-

CO2-

O

NH

SO2

NH

-O2C

-O2C

-O2C

O

NH

O2SHN

HN

O

HN

O

HN

O

HN

O

+ 66CD2suc or+ 66CD2suc

+ 33CD2suc or+ 33CD2suc

HN

O

HN

O

HN

O

HN

O

HN

O

HN

O

HN

O

HN

O

a) PAA1NSen/66CD2suc or PAA1NSen/66CD2suc

b) PAA1NSen/33CD2suc or PAA1NSen/33CD2suc

c) PAA1NShn/66CD2suc or PAA1NShn/66CD2suc

d) PAA1NShn/33CD2suc or PAA1NShn/33CD2suc

Figure 4.11. Representations of the single complexation of PAA1NSen by a) 66CD2suc

and 66CD2suc and b) 33CD2suc and 33CD2suc and the single and double complexation

of PAA1NShn by c) 66CD2suc and 66CD2suc and d) 33CD2suc and 33CD2suc.


148

4.4. 2D 1H NOESY NMR Studies

The host–guest interactions between the 1-naphthyl substituents of PAA1NSen and

PAA1NShn and CD, CD and their succinamide-linked dimers, 33CD2suc,

66CD2suc, 33CD2suc and 66CD2suc, were studied at the molecular level through

2D 1H NOESY NMR spectroscopy. The 2D 1H NOESY NMR (600 MHz, 300 ms

mixing time) spectra were recorded on 1.43 wt% PAA1NSen and PAA1NShn solutions

(10 mg in 0.70 cm3) in D2O at pD = 7.0 with 0.10 mol dm-3 NaCl at 298.2 K. The

corresponding concentrations of the 1NSen or 1NShn substituents were 3.00 × 10-3 mol

dm-3 and 2.94 × 10-3 mol dm-3, respectively. In each system, the same concentration of

CD, CD or a linked CD dimer to that of either the 1NSen or 1NShn substituents was

present in the solution.

The 2D 1H NOESY NMR spectra for the PAA1NSen solutions with CD, CD and

the linked CD dimer hosts are shown in Figures 4.12–4.17 in section 4.4.1 and the

analogous spectra for the PAA1NShn solutions are shown in Figures 4.18–4.23 in

section 4.4.2. In each system, strong cross–peaks arising from dipolar interactions

between the aromatic protons of the 1-naphthyl groups and the H3,5,6 annular protons of

either CD or CD or their linked dimers are observed. In addition, there are cross–

peaks arising from interactions between the protons of the hexyl tether in PAA1NShn

and the H3,5,6 annular protons of either CD or CD or their linked CD dimers. On the

other hand, cross–peaks arising from interactions of the ethyl tether protons in

PAA1NSen are not observed. These data are consistent with both the hexyl tether and

the 1-naphthyl group of PAA1NShn complexing within CD or CD or their linked

dimers, whereas only the 1-naphthyl group of PAA1NSen is complexed within the CD

hosts. The relative strength of cross–peaks between PAA1NSen aromatic protons and

H3,5,6 of CD and CD dimers increases in the sequence 33CD2suc < 66CD2suc <

33CD2suc < 66CD2suc; and for PAA1NShn the sequence is 33CD2suc < 33CD2suc

< 66CD2suc < 66CD2suc for aromatic 1-naphthyl protons and 33CD2suc <

66CD2suc < 33CD2suc < 66CD2suc for the hexyl tether protons.

Although the 1H NMR data are consistent with host–guest complexation occurring,

they do not distinguish between single substituent complexation and the simultaneous

complexation of 1NSen and 1NShn substituents by the CD or CD dimers to form


149

inter–polymer strand cross–links. Nevertheless, both 1H NMR and viscosity data

suggest that the ability to form additional inter–strand cross–links by host–guest

complexation depends upon the tether length of the substituted polymers, as well as the

size and geometry of the CD and CD dimers.

4.4.1. PAA1NSen

Figure 4.12. 2D 1H NOESY NMR (600 MHz) spectrum of 3% substituted PAA1NSen

(1.43 wt%, [1NSen] = 3.0 x 10-3 mol dm-3) and equimolar CD in D2O at pD 7.0 with 0.10

mol dm-3 NaCl at 298.2 K with a mixing time of 300 ms. Cross–peaks enclosed in the

rectangle arise from interaction between the annular CD protons H3,5,6 and the naphthyl

protons of the 1NSen substituent. Above: model representation of the complexation

between CD and the 1NSen substituent (blue).


150


(1.43 wt%, [1NSen] = 3.0 x 10-3 mol dm-3) and equimolar CD in D2O at pD 7.0 with 0.10

mol dm-3 NaCl at 298.2 K with a mixing time of 300 ms. Cross–peaks enclosed in the

rectangle arise from interaction between the annular CD protons H3,5,6 and the naphthyl

protons of the 1NSen substituent. Above: model representation of the complexation

between CD and the 1NSen substituent (blue).


151


(1.43 wt%, [1NSen] = 3.0 x 10-3 mol dm-3) and equimolar 33CD2suc in D2O at pD 7.0

with 0.10 mol dm-3 NaCl at 298.2 K with a mixing time of 300 ms. Cross–peaks enclosed

in the rectangle arise from interaction between the annular CD protons H3,5,6 and the

naphthyl protons of the 1NSen substituent. Above: model representation of the

complexation between 33CD2suc and the 1NSen substituent (blue).


152








153








154







CD H2-6

CD H1


155

4.4.2. PAA1NShn

Figure 4.18. 2D 1H NOESY NMR (600 MHz) spectrum of 3% substituted PAA1NShn

(1.43 wt%, [1NShn] = 2.94 x 10-3 mol dm-3) and equimolar CD in D2O at pD 7.0 with

0.10 mol dm-3 NaCl at 298.2 K with a mixing time of 300 ms. Cross–peaks enclosed in the

rectangles arise from interaction between the annular CD protons H3,5,6 and the naphthyl

and hn CH2 protons of the 1NShn substituent. Above: model representation of the

complexation between CD and the 1NShn substituent (blue).


156


(1.43 wt%, [1NShn] = 2.94 x 10-3 mol dm-3) and equimolar CD in D2O at pD 7.0 with

0.10 mol dm-3 NaCl at 298.2 K with a mixing time of 300 ms. Cross–peaks enclosed in the

rectangles arise from interaction between the annular CD protons H3,5,6 and the naphthyl

and hn CH2 protons of the 1NShn substituent. Above: model representation of the

complexation between CD and the 1NShn substituent (blue).


157


(1.43 wt%, [1NShn] = 2.94 x 10-3 mol dm-3) and equimolar 33CD2suc in D2O at pD 7.0


in the rectangles arise from interaction between the annular CD protons H3,5,6 and the

naphthyl, hn N-CH2 and hn CH2 protons of the 1NShn substituent. Above: model

representation of the complexation between 33CD2suc and the 1NShn substituent (blue).


158








159








160





naphthyl and hn CH2 protons of the 1NShn substituent. Above: model representation of the

complexation between 66CD2suc and the 1NShn substituent (blue).


161

4.5. Fluorimetric Determination of Host–Guest Complexation

The host–guest interactions between the 1-naphthyl substituents of PAA1NSen and

PAA1NShn and CD, CD and their succinamide-linked dimers, 33CD2suc,

66CD2suc, 33CD2suc and 66CD2suc, were further studied at the molecular level by

fluorescence spectroscopy. Fluorescence spectra were recorded for 0.0033 wt%

PAA1NSen and 0.0034 wt% PAA1NShn solutions, respectively (the calculated

concentrations of both the 1NSen and 1NShn substituents are 1.0 × 10-5 mol dm-3) in

pH 7.0 phosphate buffer (I = 0.10 mol dm-3) at 298.2 K. At these low concentrations,

the optical density of the 1-naphthyl substituents is below 0.05 and therefore any inner–

filter effects on fluorescence are negligible.44

Variations in the fluorescence spectra were monitored as the samples of either 0.0033

wt% PAA1NSen or 0.0034 wt% PAA1NShn solutions were sequentially diluted with

0.050 cm3 aliquots of CD solution (1.06 × 10-2 mol dm-3), CD solution (4.96 × 10-2 mol

dm-3), 33CD2suc solution (2.49 × 10-3 mol dm-3), 66CD2suc solution (2.31 × 10-3 mol

dm-3), 33CD2suc solution (2.63 × 10-3 mol dm-3) or 66CD2suc solution (2.49 × 10-3 mol

dm-3) over the range 300–550 nm in 0.5 nm intervals. The fluorescence spectra and fittings

for PAA1NSen with CD, CD and their dimers are shown in section 4.5.1 and analogous

spectra and fittings for PAA1NShn are shown in section 4.5.2.

At the low concentrations of the fluorescence studies, aggregation of 1-naphthyl groups

appears to be negligible, since no deviation from Beer’s law in the our absorption spectra

of either the PAA1NSen or PAA1NShn was observed as the concentration of the 1-

naphthyl substituents was diluted from 1.0 × 10-4 mol dm-3 to 4.0 × 10-5 mol dm-3.

Therefore, the most likely equilibria in the solutions will be the formation of either 1:1 or

1:2 host–guest complex or both between the 1-naphthyl substituents and CD or CD or a

CD or CD dimer, as exemplified by Eqns. 4.1 and 4.2 for the complexation between

66CD2suc and 1NShn. Analogous equations apply for the other PAA1NSen and

PAA1NShn systems.

66CD2suc + 1NShn 66CD2suc.1NShn (4.1)K1

66CD2suc.1NShn + 1NShn 66CD2suc.(1NShn)2 (4.2)K2


162

The observed fluorescence intensity, IF, at any given wavelength is equal to the mole

fraction–weighted sum of the fluorescence intensities of the free and 1:1 and 1:2

complexed 1NShn species, as shown in Eqn. 4.3.

IF = IF(1NShn)([1NShn]/[1NShn]total) + IFCD2suc.1NShn)([66CD2suc.1NShn]/[1NShn]total)

+ IFCD2suc.(1NShn)2)([66CD2suc.(1NShn)2]/[1NShn]total) (4.3)

The stepwise stability constants, K1 and K2, for the 1:1 and 1:2 host–guest complexes,

respectively, are defined by the following equations:

K1 = [66CD2suc.1NShn]/([66CD2suc][1NShn]) (4.4)

K2 = [66CD2suc.(1NShn)2]/([66CD2suc.1NShn][1NShn]) (4.5)

Except for the systems of PAA1NSen/66CD2suc (Figure 4.29), PAA1NShn/CD

(Figure 4.30), PAA1NShn/33CD2suc (Figure 4.32), PAA1NShn/66CD2suc (Figure

4.33) and PAA1NShn/66CD2suc (Figure 4.35), there is a decrease in both the observed

fluorescence intensity and the relative fluorescence intensity, which is the fluorescence

intensity corrected to the same concentration of the 1-naphthyl substituents relative to the

fluorescence intensity of the 1-naphthyl substituents alone (1.0 × 10-5 mol dm-3) as the ratio

of [CD host]total/[1NS guest]total increases. A slight blue-shift of emission maxima occurs in

all systems. An algorithm for the formation of 1:1 host–guest complex analogous to Eqn.

4.3, with the absence of the third right-hand term, best–fits the data in ranges of

wavelengths, where significant fluorescence changes occur, as indicated in the figure

captions, to yield the complexation constants, K1, which appear in Table 4.1. In most cases,

good fits of the fluorescence data were obtained, except for the PAA1Nsen/66CD2suc

system, where the fluorescence variation was relatively small resulting in a derived K1

value with ~30 % error.

In the cases of PAA1NSen/66CD2suc (Figure 4.29), PAA1NShn/66CD2suc (Figure

4.33) and PAA1NShn/66CD2suc (Figure 4.35) systems, an increase in the relative

fluorescence intensity was observed coupled with a much stronger blue-shift of emission

maxima as each CD dimer host was added. For these complexes, the algorithm for the

formation of 1:1 host–guest complex did not fit the fluorescence data, instead an algorithm

analogous to Eqn. 4.3 for the formation of both 1:1 and 1:2 host–guest complexes best–fits

the data to yield the stepwise complexation constants, K1 and K2, which also appear in


163

Table 4.1. Overall, the errors in the fittings of K1 and K2 for these systems are large (10 –

25 %) over the ranges of the linked CD dimer concentrations being studied.

In the case of PAA1NShn/33CD2suc system (Figure 4.32), the observed fluorescence

decreased but the relative fluorescence remained little changed upon serially addition of

33CD2suc solution. Consequently, a reliable fitting to the experimental data could not be

obtained to derive the complexation constant, K1, consistent with little complexation

occurring.


164

4.5.1. Fluorimetric Titrations of PAA1NSen Complexation

Figure 4.24. Top: Variation in the emission spectra of 0.0033 wt% PAA1NSen solution ([1NSen] = 1.0 × 10-5 mol dm-3) in pH 7.0 phosphate buffer (I = 0.10 mol dm-3) at 298.2 K upon sequential injection (0.050 cm3 each) of CD solution (1.06 × 10-2 mol dm-3). Excitation wavelength ex= 290 nm with both excitation and emission slits of 5 nm. The arrows indicate the direction of fluorescence changes as the ratio of [CD]total/[1NSen]total increases. max= 360 nm and 359 nm for the free and complexed 1NSen, respectively. Middle: Variation in the observed fluorescence (left ordinate, circles) and relative fluorescence (right ordinate, triangles) at 360 nm. The solid curves represent the best fit of the algorithm for a 1:1 complexation model in the range 330–420 nm for both cases. Bottom: Speciation relative to [1NSen]total, curve a is the percentage of free [1NSen] and curve b is the percentage of [CD.1NSen].

0

100

200

300

400

500

300 350 400 450 500

Fluo

resc

ence

inte

nsity

(a.u

.)

Wavelength (nm)

0.90

0.95

1.00

220

320

420

0 200 400 600 800

Rel

ativ

e flu

ores

cenc

e

Fluo

resc

ence

inte

nsity

(a.u

.)

[CD]total/[1NSen]total

0

20

40

60

80

100

0 200 400 600 800

% s

peci

atio

n


a

b


165

Figure 4.25. Top: Variation in the emission spectra of 0.0033 wt% PAA1NSen solution ([1NSen] = 1.0 × 10-5 mol dm-3) in pH 7.0 phosphate buffer (I = 0.10 mol dm-3) at 298.2 K upon sequential injection (0.050 cm3 each) of CD solution (4.96 × 10-2 mol dm-3). Excitation wavelength ex= 290 nm with both excitation and emission slits of 5 nm. The arrows indicate the direction of fluorescence changes as the ratio of [CD]total/[1NSen]total increases. max= 360 nm and 355 nm for the free and complexed 1NSen, respectively. Middle: Variation in the observed fluorescence (left ordinate, circles) and relative fluorescence (right ordinate, triangles) at 360 nm. The solid curves represent the best fit of the algorithm for a 1:1 complexation model in the range 330–420 nm for both cases. Bottom: Speciation relative to [1NSen]total, curve a is the percentage of free [1NSen] and curve b is the percentage of [CD.1NSen].

0

100

200

300

400

500

310 360 410 460 510Fl

uore

scen

ce in

tens

ity (a

.u.)

Wavelength (nm)

0.70

0.80

0.90

1.00

180

280

380

0 1000 2000 3000

Rel

ativ

e flu

ores

cenc

e

Fluo

resc

ence

inte

nsity

(a.u

.)


0

20

40

60

80

100

0 1000 2000 3000

% s

peci

atio

n


a

b


166

Figure 4.26. Top: Variation in the emission spectra of 0.0033 wt% PAA1NSen solution ([1NSen] = 1.0 × 10-5 mol dm-3) in pH 7.0 phosphate buffer (I = 0.10 mol dm-3) at 298.2 K upon sequential injection (0.050 cm3 each) of 33CD2suc solution (2.49 × 10-3 mol dm-3). Excitation wavelength ex= 290 nm with both excitation and emission slits of 5 nm. The arrows indicate the direction of fluorescence changes as the ratio of [33CD2suc]total/[1NSen]total increases. max= 360 nm and 356 nm for the free and complexed 1NSen, respectively. Middle: Variation in the observed fluorescence (left ordinate, circles) and relative fluorescence (right ordinate, triangles) at 360 nm. The solid curves represent the best fit of the algorithm for a 1:1 complexation model in the range 330–410 nm for both cases. Bottom: Speciation relative to [1NSen]total, curve a is the percentage of free [1NSen] and curve b is the percentage of [33CD2suc.1NSen].

0

100

200

300

400

500

310 360 410 460 510Fl

uore

scen

ce in

tens

ity (a

.u.)

Wavelength (nm)

0.85

0.90

0.95

1.00

200

300

400

0 50 100 150

Rel

ativ

e flu

ores

cenc

e

Fluo

resc

ence

inte

nsity

(a.u

.)

[33CD2suc]total/[1NSen]total

0

20

40

60

80

100

0 50 100 150

% s

peci

atio

n


a

b


167

Figure 4.27. Top: Variation in the emission spectra of 0.0033 wt% PAA1NSen solution ([1NSen] = 1.0 × 10-5 mol dm-3) in pH 7.0 phosphate buffer (I = 0.10 mol dm-3) at 298.2 K upon sequential injection (0.050 cm3 each) of 66CD2suc solution (2.31 × 10-3 mol dm-3). Excitation wavelength ex= 290 nm with both excitation and emission slits of 5 nm. The arrows indicate the direction of fluorescence changes as the ratio of [66CD2suc]total/[1NSen]total increases. max= 360 nm and 354 nm for the free and complexed 1NSen, respectively. Middle: Variation in the observed fluorescence (left ordinate, circles) and relative fluorescence (right ordinate, triangles) at 360 nm. The solid curves represent the tentative best fit of the algorithm for a 1:1 complexation model in the range 330–410 nm for both cases. Bottom: speciation relative to [1NSen]total, curve a is the percentage of free [1NSen] and curve b is the percentage of [66CD2suc.1NSen].

0

100

200

300

400

500

310 360 410 460 510Fl

uore

scen

ce in

tens

ity (a

.u.)

Wavelength (nm)

0.96

0.98

1

1.02

200

300

400

500

0 25 50 75 100 125 150

Rel

ativ

e flu

ores

cenc

e

Fluo

resc

ence

inte

nsity

(a.u

.)


0

20

40

60

80

100

0 25 50 75 100 125 150

% s

peci

atio

n


a

b


168

Figure 4.28. Top: Variation in the emission spectra of 0.0033 wt% PAA1NSen solution ([1NSen] = 1.0 × 10-5 mol dm-3) in pH 7.0 phosphate buffer (I = 0.10 mol dm-3) at 298.2 K upon sequential injection (0.050 cm3 each) of 33CD2suc solution (2.63 × 10-3 mol dm-3). Excitation wavelength ex= 290 nm with both excitation and emission slits of 5 nm. The arrows indicate the direction of fluorescence changes as the ratio of [33CD2suc]total/[1NSen]total increases. max= 360 nm and 359 nm for the free and complexed 1NSen, respectively. Middle: Variation in the observed fluorescence (left ordinate, circles) and relative fluorescence (right ordinate, triangles) at 360 nm. The solid curves represent the best fit of the algorithm for a 1:1 complexation model in the range 330–410 nm for both cases. Bottom: speciation relative to [1NSen]total, curve a is the percentage of free [1NSen] and curve b is the percentage of [33CD2suc.1NSen].

0

100

200

300

400

500

310 360 410 460 510Fl

uore

scen

ce in

tens

ity (a

.u.)

Wavelength (nm)

0.00

0.50

1.00

0

100

200

300

400

0 50 100 150

Rel

ativ

e flu

ores

cenc

e

Fluo

resc

ence

inte

nsity

(a.u

.)


0

20

40

60

80

100

0 50 100 150

% s

peci

atio

n


a

b


169

Figure 4.29. Top: Variation in the emission spectra of 0.0033 wt% PAA1NSen solution ([1NSen] = 1.0 × 10-5 mol dm-3) in pH 7.0 phosphate buffer (I = 0.10 mol dm-3) at 298.2 K upon sequential injection (0.050 cm3 each) of 66CD2suc solution (2.52 × 10-3 mol dm-3). Excitation wavelength ex= 290 nm with both excitation and emission slits of 5 nm. The arrows indicate the direction of fluorescence changes as the ratio of [66CD2suc]total/[1NSen]total increases. max= 360 nm, 347 nm and 349 nm for the free, 1:1 and 1:2 host–guest complexed 1NSen, respectively. Middle: Variation in the observed fluorescence (left ordinate, circles) and relative fluorescence (right ordinate, triangles) at 345 nm. The solid curves represent the best fit of the algorithm incorporating 1:1 and 1:2 host–guest complexation models in the range 320–480 nm for both cases. Bottom: speciation relative to [1NSen]total, curve a is the percentage of free [1NSen], curve b is the percentage of [66CD2suc.1NSen] and curve c is twice the percentage of [66CD2suc.(1NSen)2].

0

100

200

300

400

500

600

700

310 360 410 460 510Fl

uore

scen

ce in

tens

ity (a

.u.)

Wavelength (nm)

1.00

2.00

3.00

370

470

570

670

0 50 100 150

Rel

ativ

e flu

ores

cenc

e

Fluo

resc

ence

inte

nsity

(a.u

.)


0

20

40

60

80

100

0 50 100 150

% s

peci

atio

n


a

bc


170

4.5.2. Fluorimetric Titrations of PAA1NShn Complexation

Figure 4.30. Top: Variation in the emission spectra of 0.0034 wt% PAA1NShn solution ([1NShn] = 1.0 × 10-5 mol dm-3) in pH 7.0 phosphate buffer (I = 0.10 mol dm-3) at 298.2 K upon sequential injection (0.350 cm3 initially then 0.050 cm3 each) of CD solution (1.06 × 10-2 mol dm-3). Excitation wavelength ex= 290 nm with both excitation and emission slits of 5 nm. The arrows indicate the direction of fluorescence changes as the ratio of [CD]total/[1NShn]total increases. max= 360 nm and 350 nm for the free and complexed 1NShn, respectively. Middle: Variation in the observed fluorescence (left ordinate, circles) and relative fluorescence (right ordinate, triangles) at 355 nm. The solid curves represent the best fit of the algorithm for a 1:1 complexation model in the range 330–430 nm for both cases. Bottom: Speciation relative to [1NShn]total, curve a is the percentage of free [1NShn] and curve b is the percentage of [CD.1NShn].

0

50

100

150

200

310 360 410 460

Fluo

resc

ence

inte

nsity

(a.u

.)

Wavelength (nm)

1.00

1.05

1.10

120

140

160

185 385 585 785

Rel

ativ

e flu

ores

cenc

e

Fluo

resc

ence

inte

nsity

(a.u

.)

[CD]total/[1NShn]total

0

20

40

60

80

100

185 385 585 785

% s

peci

atio

n


a

b


171

Figure 4.31. Top: Variation in the emission spectra of 0.0034 wt% PAA1NShn solution ([1NShn] = 1.0 × 10-5 mol dm-3) in pH 7.0 phosphate buffer (I = 0.10 mol dm-3) at 298.2 K upon sequential injection (0.050 cm3 each) of CD solution (4.96 × 10-2 mol dm-3). Excitation wavelength ex= 290 nm with both excitation and emission slits of 5 nm. The arrows indicate the direction of fluorescence changes as the ratio of [CD]total/[1NShn]total increases. max= 360 nm and 346 nm for the free and complexed 1NShn, respectively. Middle: Variation in the observed fluorescence (left ordinate, circles) and relative fluorescence (right ordinate, triangles) at 355 nm. The solid curves represent the best fit of the algorithm for a 1:1 complexation model in the range 330–430 nm for both cases. Bottom: Speciation relative to [1NShn]total, curve a is the percentage of free [1NShn] and curve b is the percentage of [CD.1NShn].

0

50

100

150

200

300 350 400 450 500Fl

uore

scen

ce in

tens

ity (a

.u.)

Wavelength (nm)

0.70

0.80

0.90

1.00

80

100

120

140

160

180

0 1000 2000 3000

Rel

ativ

e flu

ores

cenc

e

Fluo

resc

ence

inte

nsity

(a.u

.)


0

20

40

60

80

100

0 1000 2000 3000

% s

peci

atio

n


a

b


172

Figure 4.32. Top: Variation in the emission spectra of 0.0034 wt% PAA1NShn solution

([1NShn] = 1.0 × 10-5 mol dm-3) in pH 7.0 phosphate buffer (I = 0.10 mol dm-3) at 298.2 K

upon sequential injection (0.050 cm3 each) of 33CD2suc solution (2.13 × 10-3 mol dm-3).

Excitation wavelength ex= 290 nm with both excitation and emission slits of 5 nm. The

arrows indicate the direction of fluorescence changes as the ratio of

[33CD2suc]total/[1NShn]total increases. Bottom: Variation in the observed fluorescence

(left ordinate, circles) and relative fluorescence (right ordinate, triangles) at 355 nm.

Reliable fittings of either 1:1 or 1:2 host–guest complexation model or both to the

experimental data could not be obtained.

0

50

100

150

200

310 360 410 460 510

Fluo

resc

ence

inte

nsity

(a.u

.)

Wavelength (nm)

0.90

1.00

1.10

100

120

140

160

180

0 25 50 75 100 125

Rel

ativ

e flu

ores

cenc

e

Fluo

resc

ence

inte

nsity

(a.u

.)

[33CD2suc]total/[1NShn]total


173

Figure 4.33. Top: Variation in the emission spectra of 0.0034 wt% PAA1NShn solution ([1NShn] = 1.0 × 10-5 mol dm-3) in pH 7.0 phosphate buffer (I = 0.10 mol dm-3) at 298.2 K upon sequential injection (0.050 cm3 each) of 66CD2suc solution (2.31 × 10-3 mol dm-3). Excitation wavelength ex = 290 nm with both excitation and emission slits of 5 nm. The arrows indicate the direction of fluorescence changes as the ratio of [66CD2suc]total/[1NShn]total increases. max = 360 nm, 351 nm and 354 nm for the free, 1:1 and 1:2 complexed 1NShn, respectively. Middle: Variation in the observed fluorescence (left ordinate, circles) and relative fluorescence (right ordinate, triangles) at 355 nm. The solid curves represent the best fit of the algorithm incorporating 1:1 and 1:2 host–guest complexation models in the range 320–400 nm for both cases. Bottom: speciation relative to [1NShn]total, curve a is the percentage of free [1NShn], curve b is the percentage of [66CD2suc.1NShn] and curve c is twice the percentage of [66CD2suc.(1NShn)2].

0

50

100

150

200

310 360 410 460 510Fl

uore

scen

ce in

tens

ity (a

.u.)

Wavelength (nm)

1.00

1.05

1.10

120

140

160

180

0 25 50 75 100 125

Rel

ativ

e flu

ores

cenc

e

Fluo

resc

ence

inte

nsity

(a.u

.)


0

20

40

60

80

100

0 25 50 75 100 125

% s

peci

atio

n


a

bc


174

Figure 4.34. Top: Variation in the emission spectra of 0.0034 wt% PAA1NShn solution ([1NShn] = 1.0 × 10-5 mol dm-3) in pH 7.0 phosphate buffer (I = 0.10 mol dm-3) at 298.2 K upon sequential injection (0.050 cm3 each) of 33CD2suc solution (2.63 × 10-3 mol dm-3). Excitation wavelength ex= 290 nm with both excitation and emission slits of 5 nm. The arrows indicate the direction of fluorescence changes as the ratio of [33CD2suc]total/[1NShn]total increases. max= 360 nm and 354 nm for the free and complexed 1NShn, respectively. Middle: Variation in the observed fluorescence (left ordinate, circles) and relative fluorescence (right ordinate, triangles) at 360 nm. The solid curves represent the best fit of the algorithm for a 1:1 complexation model in the range 320–410 nm for both cases. Bottom: Speciation relative to [1NShn]total, curve a is the percentage of free [1NShn] and curve b is the percentage of [33CD2suc.1NShn].

0

50

100

150

200

310 360 410 460 510Fl

uore

scen

ce in

tens

ity (a

.u.)

Wavelength (nm)

0.20

0.60

1.00

20

70

120

170

0 50 100

Rel

ativ

e flu

ores

cenc

e

Fluo

resc

ence

inte

nsity

(a.u

.)


0

30

60

90

0 30 60 90 120

Fluo

resc

ence

inte

nsity

(a.u

.)


a

b


175

Figure 4.35. Top: Variation in the emission spectra of 0.0034 wt% PAA1NShn solution ([1NShn] = 1.0 × 10-5 mol dm-3) in pH 7.0 phosphate buffer (I = 0.10 mol dm-3) at 298.2 K upon sequential injection (0.050 cm3 each) of 66CD2suc solution (2.52 × 10-3 mol dm-3). Excitation wavelength ex= 290 nm with both excitation and emission slits of 5 nm. The arrows indicate the direction of fluorescence changes as the ratio of [66CD2suc]total/[1NShn]total increases. max= 360 nm, 342 nm and 351 nm for the free, 1:1 and 1:2 complexed 1NShn, respectively. Middle: Variation in the observed fluorescence (left ordinate, circles) and relative fluorescence (right ordinate, triangles) at 355 nm. The solid curve a represents the best fit of the algorithm incorporating 1:1 and 1:2 host–guest complexation models in the range 320–430 nm for both cases. Bottom: speciation relative to [1NShn]total, curve a is the percentage of free [1NShn], curve b is the percentage of [66CD2suc.1NShn] and curve c is twice the percentage of [66CD2suc.(1NShn)2].

0

200

400

600

310 360 410 460 510Fl

uore

scen

ce in

tens

ity (a

.u.)

Wavelength (nm)

1.00

2.00

3.00

4.00

5.00

6.00

170

270

370

470

570

0 50 100 150

Rel

ativ

e flu

ores

cenc

e

Fluo

resc

ence

inte

nsity

(a.u

.)


0

20

40

60

80

100

0 50 100 150

% s

peci

atio

n


a

bc


176

Table 4.1 summarises the stepwise stability constants, K1 and K2, for the 1:1 and 1:2

host–guest complexes of the 1NSen and 1NShn poly(acrylate) substituents by CD, CD

and their succinamide–linked dimers at the molecular level by fluorescence spectroscopy.

The results show differing fluorescence variations of PAA1NSen and PAA1NShn upon

complexation with CD, CD and the CD dimers, consistent with the variation in tether

length between ethyl and hexyl, as well as in size and geometry of CD, CD and the CD

dimer hosts.

Table 4.1. Stepwise equilibrium constants, K1 and K2, for the 1:1 and 1:2 host–guest

complexation of 3% randomly substituted PAA1NShn and PAA1NSen by CD, CD and

their succinamide–linked dimers, determined by fluorimetric titrations in pH 7.0 phosphate

buffer (I = 0.10 mol dm-3) at 298.2 K.

Host

PAA1NSen PAA1NShn

K1

dm3 mol-1

10-4 × K2

dm3 mol-1

K1

dm3 mol-1

10-4 × K2

dm3 mol-1

CD 440 ± 20 – 60 ± 10 –

33CD2suc 420 ± 20 – very small –

66CD2suc 120 ± 40 – 160 ± 40 7.9 ± 0.8

CD ~20 – 330 ± 15 –

33CD2suc 1150 ± 60 – 1230 ± 60 –

66CD2suc ~20 30 ± 6 ~20 37 ± 7

The fluorescence of PAA1NSen and PAA1NShn show contrasting behaviour upon their

complexation by the native CD and CD. While CD complexes PAA1NSen much more

strongly than CD does (~22–fold) as evident by larger fluorescence variation, the longer

tethered and weakly fluorescent PAA1NShn is complexed 5.5–fold more strongly by CD

than it is by CD. This is consistent with the 1-naphthyl moiety of the short tethered

PAA1NSen fitting better to the CD annulus than the larger CD annulus. On the other

hand, the longer hexyl tether of PAA1NShn acts as a “space competitor” to compete with

1-naphthyl moiety in complexing within the CD annulus, but acts as “space regulator” to

optimise the fit of 1-naphthyl to the bigger CD annulus. The competition between the


177

hexyl and 1-naphthyl moieties in complexing within CD is consistent with the much

smaller fluorescence variation of PAA1NShn induced by CD complexation (Figure 4.30)

by comparison with that of PAA1NSen (Figure 4.24).

In addition to the effects of polymer tether lengths and CD and CD annular sizes,

differing geometries between the 3,3–linked and the 6,6–linked CD and CD dimers

provide a third controlling factor over host–guest complexation. Both 33CD2suc and

33CD2suc complex PAA1NSen and PAA1NShn in a 1:1 stoichiometry, in a similar way

to that which native CD and CD do. With the narrow end of two smaller CD annuli

pointing outward, 33CD2suc only complexes PAA1NSen moderately, while the

competition of the hexyl tether in PAA1NShn leads to very weak interaction of the 1-

naphthyl moiety with 33CD2suc (Figure 4.32). On the other hand, the larger CD annuli

of 33CD2suc allow stronger complexation to both PAA1NSen and PAA1NShn (Figures

4.28 and 4.34). Neither 33CD2suc nor 33CD2suc show inter–polymer strand cross–

linking through 1:2 host–guest complexation with either PAA1NSen or PAA1NShn. This

is consistent with two CD or CD annuli being of relatively close proximity to each other

due to the inversion of the C2A and C3

A carbons on each of the CD or CD altropyranose

units in these dimers, thus restricting intermolecular cross–linking.

In contrast, 66CD2suc and 66CD2suc show additional 1:2 host–guest complexation

with both PAA1NSen and PAA1NShn, except for the 66CD2suc/PAA1NSen system

where only the 1:1 host–guest complex is observed. For these systems, the stepwise

stability constants, K2, of the 1:2 complexes are about 2.7 to ~4.2 orders of magnitude

higher than K1 of the 1:1 complexes (Table 4.1), coupled with opposite fluorescence

behaviour as compared to the other systems (fluorescence enhancing instead of quenching,

Figures 4.29 & 4.35). This opposite fluorescence behaviour can be attributed to additional

- interaction of two adjacent 1-naphthyl groups induced by complexation by either

66CD2suc or 66CD2suc. This phenomenon has been observed previously, where induced

dimerisation of CD-appended anthracene occurs within the CD annulus, with the

stepwise 1:2 host–guest complexation constant, K2, of almost two orders of magnitude

higher than the 1:1 complexation constant, K1.45 The 1:2 host–guest complexation of

PAA1NShn by 66CD2suc and 66CD2suc appears to provide additional inter–polymer

strand cross-links which lead to enhanced viscosities of these solutions as shown in section


178

4.3 (red bars D and E, Figure 4.10, page 145). On the other hand, 1:2 host–guest

complexation between 66CD2suc and PAA1NSen do not greatly enhance solution

viscosity, consistent with the short ethyl tether restricting inter–strand cross–linking (blue

bar E, Figure 4.10, page 145). Overall, the fluorescence data agree with the 1H NMR and

viscosity data in that the ability to form additional inter–strand cross–links through host–

guest complexation depends upon both tether length of the substituted polymers and the

size and geometry of the CD and CD dimers.

4.6. Conclusion

Two new 3% randomly substituted poly(acrylate)s labelled with 1-naphthalene side

groups through either a two methylene tether, PAA1NSen, or six methylene tether,

PAA1NShn, have been synthesised and studied for their polymer network assembly in

aqueous solution. The zero–shear viscosities of 5 wt% solutions of both PAA1NSen and

PAA1NShn are similar to each other and similar to that of 5 wt% solution of 3% randomly

substituted dodecyl poly(acrylate) (PAAC12), but are several orders of magnitude smaller

than that of 5 wt% solution of 3% randomly substituted octadecyl poly(acrylate)

(PAAC18). This is consistent with - stacking between inter–polymer 1-naphthyl groups,

being the main force for the assembly, having similar strength to the hydrophobic

interaction between dodecyl substituents but much weaker than hydrophobic interaction

between the longer octadecyl substituents.

The patterns of the relative magnitudes of the effects of four CD and CD dimers,

33CD2suc, 33CD2suc, 66CD2suc and 66CD2suc, on the polymer network assembly of

PAA1NSen and PAA1NShn have been studied at the macroscopic level by viscosity and at

the molecular level by 1H NOESY NMR and fluorescence spectroscopy. The three sets of

data are together consistent with a combination of the tether lengths linking the 1-naphthyl

substituents to the polymer backbone, the sizes of the CD and CD annuli and the

geometries of the linked CD and CD dimers controlling the extent and strength of the

inter–polymer strand cross–links formed through 1-naphthyl substituent aggregation and

host–guest complexation. This has provided insight for the design of new aqueous polymer

networks and hydrogels with potential for practical application.


179

4.7. References

1. Peppas, N. A.; Huang, Y.; Torres-Lugo, M.; Ward, J. H.; Zhang, J., Annu. Rev.

Biomed. Eng. 2000, 2, 9-29.

2. Lee, K. Y.; Mooney, D. J., Chem. Rev. 2001, 101, 1869-1879.

3. Nowak, A. P.; Breedveld, V.; Pakstis, L.; Ozbas, B.; Pine, D. J.; Pochan, D.;

Deming, T. J., Nature 2002, 417, 424-428.

4. Sangeetha, N. M.; Maitra, U., Chem. Soc. Rev. 2005, 34, 821-836.

5. Hendrickson, G. R.; Lyon, L. A., Soft Matter 2009, 5, 29-35.

6. Huebsch, N.; Mooney, D. J., Nature 2009, 462, 426-432.

7. Guo, X.; Abdala, A. A.; May, B. L.; Lincoln, S. F.; Khan, S. A.; Prud'homme, R. K.,

Macromolecules 2005, 38, 3037-3040.

8. Guo, X.; Abdala, A. A.; May, B. L.; Lincoln, S. F.; Khan, S. A.; Prud'homme, R. K.,

Polymer 2006, 47, 2976-2983.

9. Li, L.; Guo, X.; Fu, L.; Prud'homme, R. K.; Lincoln, S. F., Langmuir 2008, 24, 8290-

8296.

10. Guo, X.; Wang, J.; Li, L.; Pacheco, C. R.; Fu, L.; Prud'homme, R. K.; Lincoln, S. F.,

PMSE Preprints 2007, 97, 543-544.

11. Li, L.; Guo, X.; Wang, J.; Liu, P.; Prud'homme, R. K.; May, B. L.; Lincoln, S. F.,


12. Kretschmann, O.; Choi, S. W.; Miyauchi, M.; Tomatsu, I.; Harada, A.; Ritter, H.,

Angew. Chem. Int. Ed. 2006, 45, 4361-4365.

13. Wang, J.; Li, L.; Ke, H.; Liu, P.; Zheng, L.; Guo, X.; Lincoln, S. F., Asia-Pac. J.

Chem. Eng. 2009, 4, 537-543.

14. Wang, J.; Pham, D.-T.; Guo, X.; Li, L.; Lincoln, S. F.; Luo, Z.; Ke, H.; Zheng, L.;

Prud'homme, R. K., Ind. Eng. Chem. Res. 2010, 49, 609-612.


180

15. Guo, X.; Wang, J.; Li, L.; Pham, D.-T.; Clements, P.; Lincoln, S. F.; May, B. L.;

Chen, Q.; Zheng, L.; Prud'homme, R. K., Macromol. Rapid Commun. 2010, 31, 300-

304.

16. Clements, J. H.; Webber, S. E., Macromolecules 2004, 37, 1531-1536.

17. Cao, T.; Yin, W.; Webber, S. E., Macromolecules 1994, 27, 7459-7464.

18. Premachandran, R. S.; Banerjee, S.; Wu, X.-K.; John, V. T.; McPherson, G. L.,


19. Hu, Y.; Smith, G. L.; Richardson, M. F.; McCormick, C. L., Macromolecules 1997,

30, 3526-3537.

20. Anghel, D. F.; Alderson, V.; Winnik, F. M.; Masanobu, M.; Morishima, Y., Polymer

1998, 39, 3035-3044.

21. Costa, T.; Miguel, M. G.; Lindman, B.; Schillén, K.; Lima, J. C.; Seixas de Melo, J.,

J. Phys. Chem. B 2005, 109, 3243-3251.

22. Costa, T.; Miguel, M. G.; Lindman, B.; Schillén, K.; Seixas de Melo, J., J. Phys.

Chem. B 2005, 109, 11478-11492.

23. Schillén, K.; Anghel, D. F.; Miguel, M. G.; Lindman, B., Langmuir 2000, 16, 10528-

10539.

24. Harada, A.; Ito, F.; Tomatsu, I.; Shimoda, K.; Hashidzume, A.; Takashima, Y.;

Yamaguchi, H.; Kamitori, S., J. Photochem. Photobiol. A: Chem. 2006, 179, 13-19.

25. Prazeres, T. J. V.; Beingessner, R.; Duhamel, J., Macromolecules 2001, 34, 7876-

7884.

26. Gao, C.; Yan, D.; Zhang, B.; Chen, W., Langmuir 2002, 18, 3708-3713.

27. Anghel, D. F.; Toca-Herrera, J. L.; Winnik, F. M.; Rettig, W.; Klitzing, R., Langmuir

2002, 18, 5600-5606.

28. Kanaganlingam, S.; Spartalis, J.; Cao, T.-M.; Duhamel, J., Macromolecules 2002,

35, 8571-8577.


181

29. Siu, H.; Prazeres, T. J. V.; Duhamel, J.; Olesen, K.; Shay, G., Macromolecules 2005,

38, 2865-2875.

30. Siu, H.; Duhamel, J., Macromolecules 2005, 38, 7184-7186.

31. Ingratta, M.; Duhamel, J., Macromolecules 2007, 40, 6647-6657.

32. Seixas de Melo, J.; Costa, T.; Oliveira, N.; Schillén, K., Polym. Int. 2007, 56, 882-

899.

33. Seixas de Melo, J.; Costa, T.; Francisco, A.; Macanita, A. L.; Gago, S.; Goncalves, I.

S., Phys. Chem. Chem. Phys. 2007, 9, 1370-1385.

34. Siu, H.; Duhamel, J., J. Phys. Chem. B 2008, 112, 15301-15312.

35. Costa, T.; Schillén, K.; Miguel, M. G.; Lindman, B.; Seixas de Melo, J., J. Phys.

Chem. B 2009, 113, 6194-6204.

36. Hashidzume, A.; Ito, F.; Tomatsu, I.; Harada, A., Macromol. Rapid Commun. 2005,

26, 1151-1154.

37. Hashidzume, A.; Tomatsu, I.; Harada, A., Polymer 2006, 47, 6011-6027.

38. Costa, T.; Seixas de Melo, J., J. Polym. Sci. Pol. Chem. 2008, 46, 1402-1415.

39. Tomatsu, I.; Hashidzume, A.; Harada, A., J. Am. Chem. Soc. 2006, 128, 2226-2227.

40. Pouliquen, G.; Amiel, C.; Tribet, C., J. Phys. Chem. B 2007, 111, 5587-5595.

41. May, B. L.; Clements, P.; Tsanaktsidis, J.; Easton, C. J.; Lincoln, S. F., J. Chem. Soc,

Perkin Trans. 1 2000, 463-469.

42. Easton, C. J.; van Eyk, S. J.; Lincoln, S. F.; May, B. L.; Papageorgiou, J.; Williams,

M. L., Aust. J. Chem. 1997, 50, 9-12.

43. Pham, D.-T.; Ngo, H. T.; Lincoln, S. F.; May, B. L.; Easton, C. J., Tetrahedron 2010,

66, 2895-2898.

44. Lakowicz, J. R., Principles of Fluorescence Spectroscopy, 3rd Ed.; Springer

Science+Business Media: New York, 2006.


182

45. Yang, C.; Mori, T.; Origane, Y.; Ko, Y. H.; Selvapalam, N.; Kim, K.; Inoue, Y., J.

Am. Chem. Soc. 2008, 130, 8574-8575.

Huy Tien Ngo Chapter 5 - Experimental

183

CHAPTER 5

EXPERIMENTAL†

† Publication associated with part of the material in this chapter:

Pham, D.-T.; Ngo, H. T.; Lincoln, S. F.; May, B. L.; Easton, C. J., Tetrahedron 2010, 66,

2895-2898.


184

5.1. General

5.1.1. Instrumental

Routine 1D 1H and 13C NMR spectra were recorded on a Varian Gemini ACP-300

(300.145 MHz and 75.4 MHz, respectively) spectrometer, unless otherwise stated. Spectra

were obtained in either CDCl3, D2O or DMSO-d6 solutions with references to either

tetramethylsilane (H 0.0 for SiMe4) and CDCl3 (C 77.0) in CDCl3, the residual solvent

peak (H 2.49 and C 39.5) in DMSO-d6 or an external standard, aqueous

trimethylsilylpropiosulfonic acid, in D2O. Chemical shifts are cited on the scale in parts

per million, ppm, followed by multiplicity and assignment. The following abbreviations

are used to report multiplicity: s, single; d, doublet; t, triplet; q, quartet; m, multiplet; br,

broad. The value at the centre of the multiplet resonance is recorded excepted for signals

where a multiplet is well resolved in which case the values for all individual multiplet

components are given.

The 2D 1H ROESY and NOESY NMR spectra were recorded on a Varian Inova 600

(599.957 MHz) spectrometer, using a standard sequence with a mixing time of 300 ms.

Electrospray ionisation mass spectra, ESI-MS, were recorded on a Finnigan MAT ion

trap LC-Q octapole mass spectrometer. Gas chromatography - mass spectrometry, GC-MS,

data was obtained using a Shimadzu GC-MS spectrometer. Samples were dissolved in

either Milli-Q water, HPLC grade methanol or a mixture of both at a concentration of 0.5

mg cm-3. Elemental analyses were performed by the Microanalytical Service of the

Chemistry Department, University of Otago, New Zealand. Since cyclodextrin derivatives

contain associated water molecules, fractional numbers of water molecules were added to

the molecular formula to give the best fit to the microanalytical data.

Thin-layer chromatography, TLC, was carried out on Merck Kieselgel 60 F254 on

aluminium-backed sheets. For analysis of - and -cyclodextrin derivatives, plates were

developed with 7:7:5:4 v/v ethyl acetate/propan-2-ol/ammonium hydroxide/water. The

compounds were visualised by drying the plate, dipping it into a 1% sulphuric acid in

ethanol solution and followed by heating with a heat-gun. To visualise amino bearing

cyclodextrins, plates were dried prior to dipping into 0.5% ninhydrin in ethanol and heated

with a heat-gun before dipping in 1% sulphuric acid in ethanol. For the preparations of


185

modified cyclodextrins described in the following sections, Rc represents the Rf of a

substituted cyclodextrin relative to the Rf of the parent cyclodextrin.

UV-visible absorbance spectra were recorded using a Varian CARY 5000 UV-VIS-NIR

spectrophotometer equipped with matched 1.0 cm path length quartz cells over a range of

required wavelengths at 0.5 nm intervals. Each solution was run against a reference

solution containing all components of the solution of interest except the absorbing

compound. Solutions were pre-equilibrated at 298.2 ± 0.2 K, unless stated otherwise and

maintained at this temperature during measurement by means of a thermostatted cell block.

All solutions were freshly prepared prior to measurement.

Fluorescence measurements were recorded using a Varian CARY Eclipse

spectrofluorimeter equipped with a 1.0 cm path length quartz cell. Spectra were obtained

over a range of desired wavelengths at 0.5 nm intervals, with both excitation and emission

slit widths of 5 nm (unless stated otherwise), using a 1% transmittance emission filter.

Emission spectra obtained were not corrected for instrumental factors. Solutions were pre-

equilibrated at 298.2 ± 0.2 K and maintained at this temperature during measurement by

means of a thermostatted cell block. All solutions were freshly prepared prior to

measurement.

Rheological measurements were carried out at the State Key Laboratory of Chemical

Engineering, East China University of Science and Technology, Shanghai 200237, China

using a Physica MCR 501 (Anton Parr GmbH) stress–controlled rheometer with a 25 mm

cone and plate geometry. Temperature was controlled at 298.2 ± 0.1 K by a Peltier plate.

Rheological samples were prepared by dissolution of PAA1NSen and PAA1NShn in 0.10

mol dm-3 aqueous sodium chloride to ensure screening of the electrostatic interactions

between the carboxylate groups. The solution pH was adjusted to 7.0 with 0.10 mol dm-3

aqueous sodium hydroxide solution.

5.1.2. Materials

All reagents were obtained from Sigma-Aldrich or other commercial sources and were

used without further purification, unless stated otherwise. Water was purified with a Milli-

Q system to give a resistivity of > 15 MΩ cm. Triethylamine (Ajax) was dried by

distillation. All organic solvents, N,N-dimethylformamide (APS), pyridine (Ajax), diethyl

ether (Chem Supply), acetone (Chem Supply), ethanol (Ajax), methanol (Ajax), N-


186

methylpyrrolidin-2-one (Fluka), tetrahydrofuran (Chem Supply), dichloromethane (Chem

Supply), ethyl acetate (Chem Supply) were of HPLC grade and were used without further

purification.

Squat column chromatography was carried out using Merck Kieselgel 60 F254 thin layer

chromatography silica. Aluminium oxide column chromatography was carried out using

Acros Organics basic activated aluminium oxide, 50-200 micron, Brockman activity I with

appropriate amount of water added to give Brockman activity III. Bio-Rex 70 resin was

purchased from Bio-Rad Laboratories Inc., CA and was converted to the acid form using

3.0 mol dm-3 hydrochloric acid. Diaion HP-20 resin was purchased from Supelco, PA.

CD and CD were obtained from Nihon Shokuhin Kako Co. Unless otherwise stated,

6A-O-(4-methylbenzenesulfonyl)--cyclodextrin (6CDTs),1 6A-amino-6A-deoxy--

cyclodextrin (6CDNH2),2 were prepared according to literature methods. The modified

cyclodextrins were dried to a constant weight over P2O5 containing indicator (Sicapent)

under vacuum and stored in the dark under refrigeration. Pyronine B (PB+) was purchased

from Sigma as the 95% pure salt PB2Fe2Cl8, which was twice recrystallised from water

before use.3 The commercially obtained pyronine Y (PY+) chloride salt contained

approximately 40% impurities by weight. These water insoluble impurities were filtered

from an aqueous slurry with a 0.45 m filter before use.4 Hematoporphyrin (HP) was

purchased as the 95% pure dihydrochloride salt from Sigma and was used as received.

Poly(acrylic acid)s (PAA, Mw = 250,000, Mw/Mn ≈ 2) 35 wt% aqueous solution (Aldrich)

was diluted to approximately 10 wt% and freeze-dried to constant weight to give a white

solid. 1-Naphthalenesulfonyl chloride (Aldrich, 97%), succinyl chloride (Aldrich, 95%), 4-

nitrophenol (Sigma, 98%), 1,2-diaminoethane (Ajax), 1,6-diaminohexane (Aldrich) and

N,N’-dicyclohexylcarbodiimide (Merck, 98%) were used as supplied without further

purification.

5.1.3. Data Analysis

Equation 5.1 describes the observed absorbance when a single host-guest complex

equilibrium exists in the solution, where A, G, H.G represent the total absorbance, molar

absorbances of the guest and (host).(guest) complex, respectively. Equations 5.2–5.4

describe the observed absorbance when more than one equilibrium co-exist in the


187

solutions, where G2, H.G2 represent the molar absorbances of the dimerised guest and 1:2

(host).(guest)2 complex, respectively.

A = G[guest] + H.G[(host).(guest)] (5.1)

A = G[guest] + G2[(guest)2] + H.G[(host).(guest)] (5.2)

A = G[guest] + H.G[(host).(guest)] + H.G2[(host).(guest)2] (5.3)

A = G[guest] + G2[(guest)2] + H.G[(host).(guest)] + H.G2[(host).(guest)2] (5.4)

The K1 for the 1:1 host-guest complexes of either PB+ or PY+ with CD and the linked

CD dimer hosts were derived by simultaneously fitting the algorithm analogous to Eqn.

5.1 to the absorbance variations over a wide wavelength range at 0.5 nm intervals, using

the non–linear least–squares SPECFIT/32 protocol.5 Analogous equations apply for the

fluorescence variations of all six systems.

The Kd for the dimerisation of HP2- was derived by simultaneously fitting the

algorithm analogous to Eqn. 5.2 to the absorbance variations over a wide wavelength

range at 0.5 nm intervals, with the absence of the third right–hand term, using the non–

linear least–squares fitting program HypSpec.6,7 Using the known values of Kd, HP and

HP2, the complexation constants, K1, for the 1:1 host/guest complex of HP2- by CD

and the linked CD dimer hosts were then derived by simultaneously fitting the

algorithm analogous to Eqn. 5.2 to the observed absorbance variations. Analogous

equations apply for the fluorescence variations of all three complex systems.

The stepwise complexation constants, K1 and K2, for 1:1 and 1:2 host–guest complexes

of either PAA1NSen or PAA1NShn with CD, CD, succindamide–linked CD dimers

and succinamide–linked CD dimers were derived by simultaneously fitting the algorithm

analogous to either Eqn. 5.1 or 5.3 to the fluorescence variations over a wide wavelength

range at 0.5 nm intervals, using the non–linear least–squares fitting program HypSpec.6,7

In the 1D 1H NMR study, the dimerisation constants, Kd, for PB+ and PY+ were derived

by simultaneously fitting dimerisation algorithm analogous to Eqn. 5.5 to the variation of

the 1H chemical shifts, exp, of the H1–H4 protons as [PB+]total and [PY+]total increased using

the HypNMR 2003 program.8,9 The K1 for the complexation of PB+ and PY+ by CD and

the linked CD dimer hosts were similarly derived by fitting Eqn. 5.6 to the 1H chemical


188

shift variations, exp, of the PB+ and PY+ H1–H4 protons and either the PY+ H5 or PB+ H6

proton.

exp = PB[PB+] + PB2[(PB+)2] (5.5)

exp = PB[PB+] + PB2[(PB+)2] + CD.PB[CD.PB+] (5.6)

5.1.4. Molecular Modelling

Molecular modelling and MM2 energy minimisations were performed in the gas–phase

with the ChemBio3D® Ultra 11.0 software10 and geometry optimisation was performed

using the PM6 semi-empirical method in MOPAC2009.11,12 The Broyden-Fletcher-

Goldfarb-Shanno (BFGS) optimisation procedure was employed for all PM6

optimisation,13,14 and additional keywords, XYZ (for geometry optimisation using

Cartesian coordinates) and CHARGE=n were used as appropriate. The intitial molecular

models of the CD dimers: 33CD2suc and 66CD2suc and the hematoporphyrin

complexes: CD.HP2-, 33CD2suc.HP2- and 66CD2suc.HP2- in Chapter 3 were constructed

with the assistance of Dr. Duc-Truc Pham.


189

5.2. Experimental for Chapter 2

5.2.1. Syntheses

2A-O-(4-Methylbenzenesulfonyl)--cyclodextrin, 2CDTs15

C2A O S

O

O

CD

The title compound was prepared according to the literature method,15 through the

reaction of CD (45.4 g, 0.04 mol) with p-toluenesulfonylchloride (28.8 g, 0.15 mol) in

DMF in the presence of dibutyltin oxide (25 g, 0.1 mol) and triethylamine (12.2 g, 0.12

mol) to afford a white powder with spectral information consistent with that in the

literature.16

Yield: 3.92 g (7.6 %)

TLC: Rc = 1.93

1H NMR: H (DMSO-d6) 7.86 (d, 2 H, Ar-H), 7.45 (d, 2 H, Ar-H), 5.69-5.91 (m, 13 H,

OH2,3), 4.82 (s, 7 H, H1), 4.48 (d, 7 H, OH6), 3.41-4.25 (m, 42 H, H2-6), 2.42 (s, 3 H, Ar-

CH3) 13C NMR: C (DMSO-d6): 133.4, 129.9, 128.2, 125.7 (Ar-C); 101.9-101.1 (C1B-G), 97.3

(C1A); 82.3-78.2 (C4); 73.1-69.2 (C2, C3, C5); 60.2 (C6); 40.9-38.4 (DMSO); 21.3 (Ar-

CH3).

2A,3A-Manno-epoxide--cyclodextrin, 23CDO17

C2A

O

C3ACD

The title compound was prepared by the literature method.17 A solution of 2A-O-(4-

methylbenzenesulfonyl)--cyclodextrin, 2CDTs (2.32 g, 1.8 mmol) in aqueous

ammonium bicarbonate (10 %, 100 cm3) was stirred at 60 oC for 3 hrs. The solvent was


190

removed under vacuum and the residue was redissolved in water, followed by evaporation

to dryness (this procedure was repeated three times). This crude product was dissolved in

water (20 cm3) and added dropwise to vigorously stirred acetone (200 cm3). The precipitate

formed was collected by filtration and washed with acetone and diethyl ether to give a

crude product. The crude material was dissolved in water (100 cm3) and loaded onto a

Diaion HP-20 column (3 × 20 cm). The column was washed with water (500 cm3) and 10 –

20 % aqueous methanol and the washings were evaporated under vacuum to give the

product as a white powder, which contained traces of 2CDNH2 by-product. This solid was

run through a column (4.5 × 4.5 cm) of BioRex 70 (H+), 100-200 mesh (BioRad) and

eluted by water. The fractions containing the product were combined and evaporated to

dryness under vacuum to give the title compound as a white powder.

Yield: 1.45 g (72.1 %)

TLC: Rc = 1.11 1H NMR, H (D2O): 5.26 (s, 1 H, H1A-epoxide), 5.09-5.04 (m, 6 H, H1), 3.98-3.57 (m, 41

H, H2-6), 3.46 (d, 1 H, H2A-epoxide) 13C NMR, C(D2O): 104.5-103.7 (C1), 83.7-83.0 (C4), 75.7-72.1 (C2B-G, C3B-G, C5), 63.6

(C6B-G), 62.9 (C6A), 57.1 (C2A), 52.2 (C3A).

3A-Amino-3A-deoxy-(2AS,3AS)--cyclodextrin, 3CDNH218

NH2C3A

CD

The title compound was prepared by the literature method.18 2A,3A-Manno-epoxide--

cyclodextrin (1.45 g, 1.3 mmol) was dissolved in aqueous ammonium hydroxide (25%, 40

cm3) and the solution was stirred at 60 oC for 4 hrs. The mixture was then evaporated to

dryness and the residual was dissolved in aqueous ammonium hydroxide (28%, 10 cm3)

and added to acetone (200 cm3). The precipitate was collected, washed with acetone and

diethyl ether and dried under vacuum to a crude product. The solid was dissolved in water

(10 cm3) and loaded onto a column (4.5 × 4.5 cm) of BioRex 70 (H+), 100-200 mesh

(BioRad). After flushing with water (ca. 400 cm3), the 3CDNH2 product was eluted with

1.0 mol dm-3 aqueous ammonium hydroxide (ca. 100 cm3 fractions). Fractions containing

the product were combined and evaporated to dryness under vacuum (removal of excess


191

ammonia was achieved by dissolving the residue in water and evaporating to dryness three

times) to afford 3CDNH2 as a white powder.

Yield: 0.88 g (60%)

TLC: Rc = 0.71 1H NMR: H (D2O): 5.13 (d, 2 H, H1A), 5.04-4.93 (m, 5 H, H1), 4.23 (m, 1 H, H2A), 4.01-

3.54 (m, 40 H, H2-6), 2.98 (d, 1 H, H3A) 13C NMR: C (D2O): 103.1-99.7 (C1), 80.9-80.2 (C4), 79.2-71.1 (C2, C3B-G, C5), 60.8-

59.8 (C6), 52.2 (C3A).

Bis(4-nitrophenyl) succinate19,20

O

O

O

O

NO2

O2N

A method silimar to those reported in the literature was used to prepared the title

compound.19,20 To a stirred solution of succinyl chloride (4.83 g, 31.2 mmol) in

dichloromethane (100 cm3) was added 4-nitrophenol (9.87 g, 71 mmol) in one portion and

then triethylamine (7.54 g, 74.5 mmol) dropwise over a period of 15 mins. The mixture

was stirred for 1 hr at room temperature. The reaction mixture was subsequently washed

with water (2 x 100 cm3) and the organic layer was dried over anhydrous MgSO4. TLC

(10% hexane in dichloromethane) of the organic extract showed the title compound (Rf =

0.6) and 4-nitrophenol (Rf = 0.2). Evaporation of the solvent yielded the crude product

which was recrystallised from ethyl acetate to afford the pure product as a cream coloured

flaky powder.

Yield: 2.04 g (18.1 %) 1H NMR: H (CDCl3) 8.27 (d, 4 H, ArH), 7.29 (d, 4 H, ArH), 3.06 (s, 4 H, CH2) 13C NMR: C (CDCl3) 166.8 (ester C=O), 155-122.2 (ArC), 29.1 (succinyl CH2).

General procedure for the preparation of the succinamide-linked CD dimers21

The succinmamide-linked CD dimers were prepared according to the literature

method.21 Either (2AS,3AS)-3A-amino-3A-deoxy--cyclodextrin or 6A-amino-6A-deoxy--

cyclodextrin (~1 mmol) was dissolved in pyridine (20 cm3) and stirred at room temperature


192

for 15 min. Bis(4-nitrophenyl) succinate (0.4 equivalents) was added to this solution in two

or more portions over a period of 1 hr. The reaction mixture was then stirred for 48 hrs at

room temperature before being added dropwise to diethyl ether (200 cm3) with vigorous

stirring. The resultant precipitate was collected by centrifugation, washed with acetone and

diethyl ether and dried under vacuum. The product was dissolved in H2O and run down a

BioRex 70 (H+) column to remove either excess (2AS,3AS)-3A-amino-3A-deoxy--

cyclodextrin or 6A-amino-6A-deoxy--cyclodextrin. The white solid products were

obtained by freeze drying followed by further drying over phosphorous pentoxide.

N,N′-Bis((2AS,3AS)-3A-deoxy--cyclodextrin-3A-yl) succinamide, 33CD2suc

HNC3A

O

HN C3A

OCD CD

The title compound was prepared by treatment of the 3CDNH2 (880 mg, 0.78 mmol) with

bis(4-nitrophenyl) succinate (112.7 mg, 0.31 mmol) according to the general procedure.

After the general work-up and purification procedure, the title compound was obtained as a

white solid.

Yield: 0.81 g (88%)

TLC: Rc = 0.54 1H NMR: H (D2O): 5.11-4.92 (m, 14 H, H1), 4.21-3.56 (m, 84 H, H2-6), 2.6 (s, 4 H, CH2) 13C NMR, C (D2O): 177.6 (C=O), 106.5, 104.6, 104.5, 104.1, 103.9 (C1), 83.8, 83.6, 83.5,

83.3, 82.7 (C4), 75.9, 75.7, 75.3, 75.0, 74.8, 74.5, 74.2, 74.0, 72.6 (C2,3,5), 63.0, 62.4,

(C6), 53.7 (C3A), 33.7 (CH2)

Mass spectrum m/z: 2350 (M+), 2373 (M + Na)+

Elemental analysis: C88H144N2O70.20H2O: C, 38.99; H, 6.84; N, 1.03. Found: C, 39.1; H,

6.5; N, 1.1.


193

N,N′-Bis(6A-deoxy--cyclodextrin-6A-yl) succinamide, 66CD2suc

HN

O

C6AHN

O

C6A

CD CD

The title compound was prepared by treatment of the 6CDNH2 (1.21 g, 1.1 mmol) with

bis(4-nitrophenyl) succinate (158.5 mg, 0.44 mmol) according to the general procedure.


white solid.

Yield: 0.84 g (81.2 %)

TLC: Rc = 0.40 1H NMR, H (D2O): 5.07 (m, 14 H, H1), 3.99-3.38 (m, 84 H, H2-H6), 2.60 (m, 4 H, CH2)

13C NMR, C (D2O): 177.5 (C=O), 104.6 (C1), 85.7, 83.8 (C4), 75.8, 74.8, 74.5, 72.9

(C2,3,5), 63.0 (C6B-G), 42.8 (C6A), 33.7 (CH2)

Mass spectrum m/z: 2351 (M + H)+, 2373 (M+Na)+


6.6; N, 1.1.

5.2.2. Sample Preparation

5.2.2.1. Sample Preparation for UV–vis and Fluorescence Studies

Stock solutions of the pyronines PB+ (6.0 × 10-4 mol dm-3), PY+ (9.0 × 10-4 mol dm-3)

and the hosts CD (1.5 × 10-2 mol dm-3), 33CD2suc and 66CD2suc (5.0 × 10-3 mol dm-3)

were freshly prepared in aqueous hydrochloric acid (1.00 × 10-4 mol dm-3),22 to prevent

base hydrolysis and 0.10 mol dm-3 sodium chloride to maintain constant ionic strength.

The concentrations of PY+ stock were estimated using the reported molar absorptivity at

546 nm of = 8.1 × 104 mol-1 dm3 cm-1.23

Aqueous solutions for UV–vis and fluorescence studies were 6.0 × 10-6 mol dm-3 in PB+

and 9.0 × 10-6 mol dm-3 in PY+; and 6.0 x 10-7 mol dm-3 of PB+ and 9.0 × 10-7 mol dm-3 of

PY+, respectively. The CD and linked CD dimer concentrations varied over wide ranges,

as indicated in the figure captions.


194

5.2.2.2. Sample Preparation for 1H NMR Studies

Solutions for 1H NMR experiments were prepared in D2O, 1.00 × 10-4 mol dm-3 in

hydrochloric acid and 0.10 mol dm-3 in sodium chloride. The concentrations of PB+ and

PY+ solutions for dimerisation studies ranged from 1.0 × 10-3 mol dm-3 to 2.0 × 10-2 mol

dm-3. For complexation studies, the concentrations of PB+ and PY+ were kept constant at

2.0 × 10-3 mol dm-3, while those of the CD and CD dimer hosts were varied from 0–5.0

× 10-3 mol dm-3 by addition of appropriate volumes of stock solutions.

For the 2D 1H ROESY NMR experiments, each sample was 2.0 × 10-3 mol dm-3 in

either PB+ or PY+ and in either CD or a linked CD dimer, unless stated otherwise in the

figure captions.


195


5.3.1. Syntheses24

6A-O-(2,4,6-triisopropylbenzenesulfonyl)--cyclodextrin (6CDTPBS)25

SO

OO

CDC6A

The title compound was prepared according to the literature method.25 To a solution

pyridine (30 cm3) was added CD (5.0 g, 3.85 mmol) and the mixture was stirred at room

temperature for 30 mins under nitrogen. 2,4,6-triisopropylbenzenesulfonyl chloride (3.5 g,

11.56 mmol) was added in 3 portions over the period of 2 hrs and stirred for 24 hrs. The

mixture was concentrated to ca. 10 cm3 and added dropwise to vigorously stirred acetone

(200 cm3). The resulting precipitate was collected by filtration, washed with acetone and

diethyl ether and dried under vacuum to give 6.4 g of crude product. The crude material

was repeatedly recrystallised from water until no more crystals formed to afford the title

product as a white solid.

Yield: 0.78 g (12.9 %)

TLC: Rc = 1.32

1H NMR: H (DMSO-d6) 7.28 (s, 2 H, Ar-H), 5.91-5.69 (m, 16 H, OH2,3), 4.85 (m, 8 H,

H1), 4.58-4.47 (m, 7 H, OH6), 4.25 (m, 2 H, CH2-OSO-Ar), 3.21-4.03 (m, 47 H, H2-6, Ar-

CH(CH3)2), 2.94 (m, 1 H, Ar-CH(CH3)2), 1.21 (m, 18 H, Ar-CH(CH3)2).

2A-O-(4-methylbenzenesulfonyl)--cyclodextrin, 2CDTs, and its 6A analogue, 6CDTs

C6AC2A OO S

O

O

S

O

O

CDCD

2CDTS 6CDTS


196

The title compounds were prepared by a modification of the literature method.15 CD

(51.9 g, 40.0 mmol) was added to anhydrous DMF (150 cm3) and the mixture was stirred

for two hrs at 0 oC under dry nitrogen until dissolution was complete. After heating to 100 oC, dibutyltin oxide (25.1 g, 100.9 mmol) was added and stirred for another 2 hrs. The

mixture was then cooled to 0 oC, triethylamine (12.2 g, 120.6 mmol) was added, followed

by dropwise addition of 4-toluenesulfonyl chloride (20 g, 105 mmol) in DMF (50 cm3).

The mixture was stirred for 2 hrs before another portion of 4-toluenesulfonyl chloride (9.7

g, 50.9 mmol) in DMF (20 cm3) was added dropwise. The resultant solution was stirred for

a further 10 hrs at room temperature and then concentrated to a yellow syrup. This was

added to 2 dm3 of vigorously stirred acetone and stirring was continued for 30 mins. The

precipitate formed was collected by filtration, washed with acetone and diethyl ether and

dried under vacuum to give 62 g of crude product which was recrystallised from ca. 200

cm3 water. The precipitate was collected and dried under vacuum to give ca. 9 g of crude

6CDTs, while the filtrate was evaporated to dryness to give ca. 47 g of crude 2CDTs.

The crude 2CDTs was dissolved in water (1 dm3) and loaded onto a Diaion HP-20

column (5 × 30 cm). After flushing with ca. 3 dm3 of water, followed by 10 – 15 %

aqueous methanol solvent gradient elution of unreacted CD, 2CDTs was eluted with 20 -

25% aqueous methanol (ca. 400 cm3 fractions). The fractions containing the product were

combined, the methanol was removed and the product was dried under vacuum to give the

2CDTs as a white powder.

Yield: 4.37 g (7.5 %)

TLC: Rc = 1.67 1H NMR: H (DMSO-d6): 7.83, 7.47 (ABq, J = 8.2 Hz, 4H, ArH), 5.91-5.69 (m, 15 H,

OH2, OH3), 4.88 (s, 8 H, H1), 4.30-3.30 (m, 56 H, H2-6, OH6), 2.41 (s, 3 H, Ar-CH3) 13C NMR: C (DMSO-d6): 133.4, 129.9, 128.2, 125.7 (Ar-C); 101.9-101.1 (C1B-H), 97.3

(C1A); 82.3-78.2 (C4); 73.1-69.2 (C2, C3, C5); 60.2 (C6); 40.9-38.4 (DMSO); 21.3 (Ar-

CH3).

The crude 6CDTs was dissolved in water (500 – 700 cm3) and loaded onto a Diaion

HP-20 column (3 × 25 cm). After flushing with water (ca. 1 dm3), followed by 10 – 20%

aqueous methanol solvent gradient elution of unreacted CD, 6CDTs was eluted with 30 –


197

40 % aqueous methanol (ca. 250 cm3 fractions). The fractions containing the product were

combined and evaporated to dryness under vacuum to give 6CDTs as a white powder.

Yield: 2.47 g (4.25 %)

TLC: Rc = 1.40 1H NMR: H (DMSO-d6): 7.78, 7.46 (ABq, J = 8.3 Hz, 4H, ArH), 6.05-5.35 (m, 16 H,

OH2, OH3), 5.09-4.81 (m, 8 H, H1), 4.31-3.20 (m, 55 H, H2-6, OH6), 2.42 (s, 3 H, Ar-CH3) 13C NMR: C (DMSO-d6): 133.2, 130.7, 128.8, 126.2 (Ar-C); 102.9-101.8 (C1A); 81.6-80.8

(C4); 73.6-69.7 (C2, C3, C5); 60.7 (C6); 40.9-38.4 (DMSO); 21.8 (Ar-CH3).

2A,3A-Manno-epoxide--cyclodextrin, 23CDO

C2A

O

C3ACD

The title compound was prepared according to the literature method.17 A solution of 2A-

O-(4-methylbenzenesulfonyl)--cyclodextrin, 2CDTs (4 g, 2.76 mmol) in aqueous

ammonium bicarbonate (10 %, 125 cm3) was stirred at 60 oC for 3 hrs. The solvent was

removed under vacuum and the residue was redissolved in water, followed by evaporation

to dryness (this procedure was repeated three times). This crude product was dissolved in

water (20 cm3) and added dropwise to vigorously stirred acetone (500 cm3). The precipitate

formed was collected by filtration and washed with acetone and diethyl ether to give 4 g of

crude product. The crude material was dissolved in water (125 cm3) and loaded onto a

Diaion HP-20 column (3 × 20 cm). The column was washed with water (1 dm3) and 10 %

aqueous methanol and the washings were evaporated under vacuum to give the product as

a white powder, which contained traces of 2CDNH2 by-product. This solid was run

through a column (4.5 × 4.5 cm) of BioRex 70 (H+), 100-200 mesh (BioRad) and eluted by

water. The fractions containing the product were combined and evaporated to dryness

under vacuum to give the title compound as a white powder.

Yield: 2.77 g (78.6 %)

TLC: Rc = 1.15 1H NMR: H (D2O): 5.27 (s, 1 H, H1A-epoxide), 5.13-5.07 (m, 7 H, H1), 3.95-3.59 (m, 47

H, H2-6), 3.49 (d, 1 H, H2A-epoxide)


198

13C NMR: C(D2O): 104.5-103.7 (C1), 83.7-83.0 (C4), 75.7-72.1 (C2B-H, C3B-H, C5), 63.6

(C6B-H), 62.9 (C6A), 57.1 (C2A), 52.2 (C3A).

3A-Amino-3A-deoxy-(2AS,3AS)--cyclodextrin, 3CDNH2

NH2C3A

CD

The title compound was prepared according to the literature method.18 2A,3A-Manno-

epoxide--cyclodextrin, 23CDO (2.6 g, 2.03 mmol) was dissolved in aqueous ammonium

hydroxide (25%, 60 cm3) and the solution was stirred at 60 oC for 4 hrs. The mixture was

then evaporated to dryness and the residual was dissolved in aqueous ammonium

hydroxide (28%, 20 cm3) and added to acetone (500 cm3). The precipitate was collected,

washed with acetone and diethyl ether and dried under vacuum to obtain 2.74 g of the

crude product. This was dissolved in water (20 cm3) and loaded onto a column (4.5 × 4.5

cm) of BioRex 70 (H+), 100-200 mesh (BioRad). After flushing with water (ca. 500 cm3),

the 3CDNH2 product was eluted with 1.0 mol dm-3 aqueous ammonium hydroxide (ca.

100 cm3 fractions). Fractions containing the product were combined and evaporated to

dryness under vacuum (removal of excess ammonia was achieved by dissolving the residue

in water and evaporating to dryness three times) to afford 3CDNH2 as a white powder.

Yield: 1.49 g (56.7 %)

TLC: Rc = 0.76. 1H NMR, H (D2O): 5.22 (d, 2 H, H1A), 5.16-4.93 (m, 6 H, H1), 4.20 (m, 1

H, H2A): 4.00-3.56 (m, 46 H, H2-6), 3.10 (d, 1 H, H3A) 13C NMR: C (D2O): 103.1-99.7 (C1), 80.9-80.2 (C4), 79.2-71.1 (C2, C3B-H, C5), 60.8-

59.8 (C6), 52.2 (C3A).

6A-Amino-6A-deoxy--cyclodextrin, 6CDNH2

NH2C6A

CD


199

The title compound was prepared according to the literature method.2 6A-O-(4-

Methylbenzenesulfonyl)--cyclodextrin, 6CDTs (3.4 g, 2.3 mmol) was dissolved in

ammonium hydroxide (28%, 250 cm3) at 0 oC. The reaction vessel was closed and left in

the dark with occasional stirring for 5 days. The ammonium hydroxide was removed under

reduced pressure, after which water was added (100 cm3) and removed under reduced

pressure. The remaining solid was dissolved in ammonium hydroxide (28%, 20 cm3) and

the solution added drop-wise to vigorously stirring acetone (450 cm3) and stirred for 30

min. The resulting precipitate was dried under vacuum to give crude 6CDNH2 as a cream

powder. This was dissolved in water (20 cm3) and loaded onto a BioRex 70 (H+) column.

The column was washed with water (400 cm3), and the title compound was eluted with

0.05 – 0.1 mol dm-3 aqueous ammonium carbonate (4 × 100 cm3 fractions). The 6CDNH2

containing fractions were evaporated to dryness under reduced pressure, and the residue

freeze dried to give 6CDNH2 as a white solid.

Yield: 0.55 g (18 %)

TLC: Rc = 0.90 1H NMR: δ(D2O) 5.37 (s, 2H, H1A), 5.10 (m, 14H, H1B-H), 3.93-3.58 (m, 48H, H2-6) 13C NMR: δ(D2O): 103.72-101.77 (C1); 80.50-79.0 (C4); 73.89-71.88 (C2, C3, C5); 60.33

(C6); 41.05 (C6A).

General procedure for the preparation of the succinamide-linked CD dimers21

The succinmamide-linked CD dimers were prepared according to the literature

method.21 Either (2AS,3AS)-3A-amino-3A-deoxy--cyclodextrin or 6A-amino-6A-deoxy--

cyclodextrin (~1 mmol) was dissolved in pyridine (20 cm3) and stirred at room temperature

for 15 min. Bis(4-nitrophenyl) succinate (0.4 equivalents) was added to this solution in two

or more portions over a period of 1 hr. The reaction mixture was then stirred for 48 hrs at

room temperature before being added dropwise to diethylether (200 cm3) with vigorous

stirring. The resultant precipitate was collected by centrifugation, washed with acetone and

diethylether and dried under vacuum. The product was dissolved in H2O and run down a

BioRex 70 (H+) column to remove either excess (2AS,3AS)-3A-amino-3A-deoxy--

cyclodextrin or 6A-amino-6A-deoxy--cyclodextrin. The white solid products were

obtained by freeze drying followed by further drying over phosphorous pentoxide.


200

N,N′-Bis((2AS,3AS)-3A-deoxy--cyclodextrin-3A-yl) succinamide, 33CD2suc

HNC3A

O

HN C3A

OCD CD

The title compound was prepared by treatment of the 3CDNH2 (1.39 g, 1.08 mmol)

with bis(4-nitrophenyl) succinate (155 mg, 0.43 mmol) according to the general procedure.


white solid.

Yield: 0.87 g (75.7 %)

TLC: Rc = 0.60 1H NMR: H (D2O): 5.39-4.94 (m, 16 H, H1), 4.26-3.59 (m, 96 H, H2-6), 2.6 (s, 4 H, CH2) 13C NMR: C (D2O): 177.7 (C=O), 105.8, 104.2, 102.3 (C1), 81.9, 82.7, 83.1 (C4), 72.3,

73.9, 74.4, 74.9, 74.9, 75.2, 75.6 (C2,3,5), 62.4, 62.9 (C6), 53.6 (C3A), 33.6 (CH2)

Mass spectrum m/z: 1359.9 (M+Na)2+


6.39; N, 0.89.

N,N′-Bis(6A-deoxy--cyclodextrin-6A-yl) succinamide, 66CD2suc

HN

O

C6AHN

O

C6A

CD CD

The title compound was prepared by treatment of the 6CDNH2 (1.58 g, 1.21 mmol)

with bis(4-nitrophenyl) succinate (176 mg, 0.49 mmol) according to the general procedure.


white solid.

Yield: 1.2 g (91.6 %)

TLC: Rc = 0.45 1H NMR, H (D2O): 5.11 (m, 16 H, H1), 3.42-3.93 (m, 96 H, H2-H6), 2.59 (m, 4 H, CH2)


201

13C NMR, C (D2O): 177.5 (C=O), 104.3 (C1), 85.7, 83.1 (C4), 75.6, 75.0, 74.4, 72.8

(C2,3,5), 62.9 (C6B-H), 42.8 (C6A), 33.7 (CH2)

Mass spectrum m/z: 1359.9 (M+Na)2+


6.40; N, 0.91.


5.3.2.1. Sample Preparation for UV–vis and Fluorescence Studies

Solutions were prepared from fresh stock solutions in pH 10.0, 0.025 mol dm-3

carbonate/bicarbonate buffer (NaHCO3 0.0107 mol dm-3, Na2CO3 0.0143 mol dm-3 and

NaCl 0.0466 mol dm-3) at constant ionic strength I = 0.10 mol dm-3. Initial aqueous

solutions for UV–visible studies were 7.6 × 10-6 mol dm-3 in HP2- and the titrations

were conducted by sequential injection of 0.100 cm3 aliquots of either the buffer (in

dimerisation studies) or CD (2.63 × 10-2 mol dm-3) and linked CD dimers (2.50 × 10-3

mol dm-3) in complexation studies.

Solutions for fluorescence studies were 2.10 × 10 -7 mol dm-3 in HP2- and the CD

and linked CD dimer concentrations varied over wide ranges as indicated in the figure

captions.


Solutions for 2D 1H–NOESY NMR experiments were prepared in D2O (pD 10.0

carbonate/bicarbonate buffer, NaHCO3 0.0107 mol dm-3, Na2CO3 0.0143 mol dm-3 and

NaCl 0.0466 mol dm-3) at constant ionic strength I = 0.10 mol dm-3. Each sample was

5.0 × 10-3 mol dm-3 in HP2- and equimolar in either CD or a linked CD dimer.

5.3.3. Thermodynamic Parameters Determination

UV–vis titrations at temperatures ranging from 278.2 to 318.2 K were performed to

obtain the dimerisation constants, Kd, of HP2- and the complexation constants, K1, of

the 1:1 host-guest complexes.

The relationship between the Gibbs free energy (Go), enthalpy (Ho) and entropy

(So) for the dimerisation or complexation and the equilibrium constants (K) are given


202

by the following van’t Hoff equations:

Go = –RTlnK (5.6)

with

Go = Ho – TSo (5.7)

from 5.6 and 5.7,

lnK = –Ho/RT + So/R (5.8)

where R is the gas constant and T is the absolute temperature. The plot of lnK versus 1/T

according to Eqn. 5.8 is a van’t Hoff plot, and for a linear plot, the slope and the intercept

represent –Ho/R and So/R, respectively.


203


5.4.1. Syntheses

4-Nitrophenyl naphthalene-1-sulfonate

SO

OO N+

O

O-

This procedure was adopted from a similar reported method.26 A mixture of 4-

nitrophenol (2.38 g, 17.1 mmol), 1-naphthalenesulfonyl chloride (3.88 g, 17.1 mmol) and

triethylamine (2.60 g, 25.6 mmol) in dichloromethane (200 cm3) was stirred at room

temperature for 3 hrs under nitrogen. The reaction mixture was filtered through Celite and

the filtrate was loaded onto a squat column (4.5 × 9 cm) and eluted with dichloromethane

(500 cm3). Fractions containing the product was combined and evaporated under reduced

pressure to give the pure product as an orange powder.

Yield: 5.09 g (90.4 %)

TLC (10 % hexane in CH2Cl2): Rf = 0.73 1H NMR: H (DMSO-d6): 8.64 (d, J = 8.4 Hz, 1H, naphthyl H8), 8.46 (d, J = 8.4 Hz, 1H,

naphthyl H2), 8.25-8.16 (m, 4H, naphthyl H4,5, phenyl H3,4), 7.96 (t, J = 6.9 Hz, 1H,

naphthyl H7), 7.82 (t, J = 6.9 Hz, 1H, naphthyl H6), 7.66 (t, J = 6.9 Hz, 1H, naphthyl H3),

7.23-7.17 (m, 2H, phenyl H2,6).

N-(2-Aminoethyl)-1-naphthyl-sulfonamide, 1NSen

SO O

HN

NH2

A solution of 4-nitrophenyl naphthalene-1-sulfonate (600 mg, 1.82 mmol) in

dichloromethane was added dropwise to a vigorously stirred solution of 1,2-diaminoethane

(1.1 g, 18.2 mmol) in dichloromethane (10 cm3) at room temperature over a period of 4

hrs. The reaction was left overnight before being diluted with water (50 cm3) and acidified


204

to pH < 2 with 3.0 mol dm-3 hydrochloric acid. The solution was washed with

dichloromethane (3 × 50 cm3), the aqueous solution was made basic to pH > 10 with 40

wt% aqueous sodium hydroxide and extracted with dichloromethane (3 × 50 cm3). The

combined dichloromethane solution was washed successively with water (3 × 100 cm3)

and brine (3 × 50 cm3) and dried over anhydrous sodium sulphate. The solvent was

removed under reduced pressure to give the pure product as a slight yellow solid.

Yield: 262 mg (57.5 %) 1H NMR: H (DMSO-d6): 8.66 (d, J = 8.4 Hz, 1H, ArH8), 8.22 (d, J = 8.4 Hz, 1H, ArH2),

8.11 (m, 2H, ArH4,5), 7.74-7.62 (m, 3H, ArH3,6,7), 2.75 (t, J = 6.6 Hz, 2H, SO2NHCH2),

2.43 (t, J = 6.6 Hz, 2H, CH2NH2).

GC-MS: C12H14N2O2S m/z calcd. 250.32, found: 250.15.

N-(6-Aminohexyl)-1-naphthyl-sulfonamide, 1NShn

SO OHN

NH2

A solution of 4-nitrophenyl naphthalene-1-sulfonate (585 mg, 1.78 mmol) in N,N-

dimethylformamide (10 cm3) was added dropwise to a vigorously stirred solution of 1,6-

diaminohexane (2.25 g, 19.4 mmol) in N,N-dimethylformamide (10 cm3) at room

temperature over a period of 4 hrs and the reaction was left overnight. The solvent was

removed under reduced pressure and dissolved in dichloromethane (40 cm3) and 10 wt%

hydrochloric acid (40 cm3). The aqueous solution was washed with dichloromethane (3 ×

40 cm3), made basic to pH > 10 with 40 wt% aqueous sodium hydroxide and extracted

with dichloromethane (3 × 50 cm3). The combined dichloromethane solution was washed

successively with water (3 × 50 cm3) and brine (3 × 50 cm3) and dried over anhydrous

sodium sulphate. The solvent was concentrated down to approximately 5 cm3, any

precipitation formed was filtered and the filtrate was loaded onto a basic aluminium oxide

column (4.5 × 4.5 cm, Brockman activity III). The column was eluted with a gradient of

dichloromethane:methanol from 100:0 to 70:30. Fractions containing the product were

combined and concentrated under reduced pressure to give the product as yellow oil.

Yield: 176 mg (32 %)


205

1H NMR: H (DMSO-d6): 8.65 (d, J = 7.8 Hz, 1H, ArH8), 8.22 (d, J = 8.1 Hz, 1H, ArH2),

8.10 (m, 2H, ArH4,5), 7.71-7.62 (m, 3H, ArH3,6,7), 2.76 (t, J = 6.9 Hz, 2H, SO2NHCH2),

2.36 (t, J = 6.9 Hz, 2H, CH2NH2), 1.27-1.02 (m, 8H, (CH2)4)

GC-MS: C16H22N2O2S m/z calcd. 306.42, found: 306.20.

General procedure for the preparation of the 3% randomly substituted 1-naphthyl-

sulfonamide poly(acrylate)s27,28

The 3% randomly substituted 1-naphthyl-sulfonamide poly(acrylate)s were prepared

according to the generam procedure reported in the literature.27,28 The solid poly(acrylic

acid)s, PAA (1.9 g, 26.4 mmol of -COOH groups) was dissolved in N-methylpyrrolidin-2-

one (60 cm3) at 60 oC for 24 hrs. Either 1NSen or 1NShn (0.79 mmol) in N-

methylpyrrolidin-2-one (7.5 cm3) was added followed by dicyclohexylcarbodiimide (0.79

mmol) in N-methylpyrrolidin-2-one (7.5 cm3) and the reaction mixture was stirred at 60 oC

for at least 48 hrs. After cooling to room temperature, 40 wt% aqueous sodium hydroxide

(60 cm3) was added. The resulting precipitate was filtered and washed with 60 oC N-

methylpyrrolidin-2-one (2 × 30 cm3) and methanol (2 × 40 cm3). The crude product was

dissolved in water (12.5 cm3) and added dropwise to methanol (100 cm3) and the

precipitate collected (this step was repeated). The solid was dissolved in water (30 cm3)

and dialysed (Spectra/Por 3 tubing, molecular weight cutoff 3,500 g mol-1) against

deionised water until the conductivity of the water outside the tube remained constant. The

final dry product was obtained as the sodium polyarylate salt by freeze-drying after

concentrating the solution to 10 cm3 by evaporation. Typical yields were 80–90 %. The

degree of substitution was determined to be 3.0 ± 0.3 % by 1H NMR spectroscopy

according to the literature method.27,28 The 1H NMR spectra of PAA1NSen and

PAA1NShn in D2O are shown in Chapter 4.


5.4.2.1.Sample Preparation for UV–vis and Fluorescence Studies

Stock solutions of 5.0 wt% in either PAA1NSen or PAA1NShn were prepared in pH

7.0 phosphate buffer (KH2PO4 0.0195 mol dm-3, Na2HPO4 0.0268 mol dm-3) at constant

ionic strength I = 0.10 mol dm-3. For UV–vis and fluorescence studies, the stock

solutions were diluted to make 0.0330 wt% and 0.0033 wt% in either PAA1NSen or

PAA1NShn, which correspond to 1.0 × 10-4 mol dm-3 and 1.0 × 10-5 mol dm-3 in either


206

1NSen or 1NShn groups, respectively, based on their calculated molecular weights

determined below.

Determination of the molecular weights of 1NSen and 1NShn in 3% randomly

substituted PAAs:

Mw(1NSen) = 3 × [Mw(CH2CHCOONa) × 97 % + Mw(CH2CHCO1NSen) × 3 %]

= 3343 g mol-1

Mw(1NShn) = 3 × [Mw(CH2CHCOONa) × 97 % + Mw(CH2CHCO1NShn) × 3 %]

= 3399 g mol-1

The initial solutions for fluorescence studies of 1.0 × 10-5 mol dm-3 in either [1Nsen]

or [1NShn] were sequentially diluted with 0.050 cm3 aliquots of stock solutions of each

CD host: CD (1.06 × 10-2 mol dm-3), CD (4.96 × 10-2 mol dm-3), 33CD2suc (2.49 ×

10-3 mol dm-3), 66CD2suc (2.31 × 10-3 mol dm-3), 33CD2suc (2.63 × 10-3 mol dm-3) or

66gCD2suc (2.49 × 10-3 mol dm-3). In a typical titration measurement, 30 aliquots of

either host were added.


Solutions for 1D and 2D 1H–NOESY NMR experiments were prepared in D2O in

0.10 mol cm-3 sodium chloride. The solution pH was adjusted to 7.0 with 0.10 mol dm -3

aqueous sodium hydroxide solution. Each sample contained 1.43 wt% in either

PAA1NSen or PAA1NShn (3.0 × 10-3 mol dm-3 in 1NSen groups and 2.94 × 10-3 mol

dm-3 in 1NShn groups) and the same concentration of CD, CD or a linked CD dimer.


207

5.5. References

1. Brady, B.; Lynam, N.; O'Sullivan, T.; Ahern, C.; Darcy, R., Org. Syntheses 2000,

77, 220-224.

2. Brown, S. E.; Coates, J. H.; Coghlan, D. R.; Easton, C. J.; Vaneyk, S. J.;

Janowski, W.; Lepore, A.; Lincoln, S. F.; Luo, Y.; May, B. L.; Schiesser, D. S.;

Wang, P.; Williams, M. L., Aust. J. Chem. 1993, 46, 953-958.

3. Chamberlin, E. M.; F, P. B.; Williams, D. E.; Conn, J., J. Org. Chem. 1962, 27,

2263-2264.

4. Schiller, R. L.; Lincoln, S. F.; Coates, J. H., J. Chem. Soc., Faraday Trans. 1

1987, 83, 3237-3248.

5. Binstead, R. A.; Jung, B.; Zuberbuhler, A. D. SPECFIT/32, v3.0.39(b); Spectrum

Software Associates: Marlborough, MA, USA, 2007.

6. Gans, P.; Sabatini, A.; Vacca, A., Talanta 1996, 43, 1739-1753.

7. Gans, P.; Sabatini, A.; Vacca, A., Ann. Chim. (Rome) 1999, 89, 45-49.

8. Frassineti, C.; Ghelli, S.; Gans, P.; Sabatini, A.; Moruzzi, S.; Vacca, A., Anal.

Biochem. 1995, 231, 374-382.

9. Gans, P.; Sabatini, A.; Vacca, A. HypNMR, v3.1.5; Protonic Software: 2004.

10. CambridgeSoft, ChemBio3D Ultra, v11.0.1; Cambridge, 2007.

11. Stewart, J. J. P., J. Mol. Mod. 2007, 13, 1173-1213.

12. Stewart, J. J. P., MOPAC2009, v. 10.288w; Stewart Computational Chemistry:

2009.

13. Agrafidtis, D.; Rzepa, H., J. Chem. Res. Synop. 1988, 100-101.

14. Head, J.; Zerner, M., Chem. Phys. Lett. 1985, 122, 264-270.

15. Murakami, T.; Harata, K.; Morimoto, S., Tetrahedron Lett. 1987, 28, 321-324.


208

16. Ueno, A.; Breslow, R., Tetrahedron Lett. 1982, 23, 3451-3454.

17. Breslow, R.; Czarnik, A. W., J. Am. Chem. Soc. 1983, 105, 1390-1391.

18. Murakami, T.; Harata, K.; Morimoto, S., Chem. Lett. 1988, 553-556.

19. Du, H.-T.; Du, H.-J.; Lu, M.; Sun, L.-L., Acta Cryst. 2007, E63, o4926.

20. Guo, K.; Chu, C. C., J. Polym. Sci. Pol. Chem. 2007, 45, 1595-1606.

21. Easton, C. J.; van Eyk, S. J.; Lincoln, S. F.; May, B. L.; Papageorgiou, J.;

Williams, M. L., Aust. J. Chem. 1997, 50, 9-12.

22. Reija, B.; Al-Soufi, W.; Novo, M.; Tato, J. V., J. Phys. Chem. B 2005, 109, 1364-

1370.

23. Gianneschi, L. P.; Kurucsev, T., J. Chem. Soc, Faraday Trans. 2 1974, 70, 1334-

1342.

24. Pham, D.-T.; Ngo, H. T.; Lincoln, S. F.; May, B. L.; Easton, C. J., Tetrahedron

2010, 66, 2895-2898.

25. Palin, R.; Grove, S. J. A.; Prosser, A. B.; Zhang, M.-Q., Tetrahedron Lett. 2001,

42, 8897-8899.

26. May, B. L.; Clements, P.; Tsanaktsidis, J.; Easton, C. J.; Lincoln, S. F., J. Chem.

Soc, Perkin Trans. 1 2000, 463-469.

27. Guo, X.; Abdala, A. A.; May, B. L.; Lincoln, S. F.; Khan, S. A.; Prud'homme, R.

K., Macromolecules 2005, 38, 3037-3040.

28. Guo, X.; Abdala, A. A.; May, B. L.; Lincoln, S. F.; Khan, S. A.; Prud'homme, R.

K., Polymer 2006, 47, 2976-2983.

209

APPENDIX A

PUBLICATIONS

Based on the research carried out during the period of PhD candidature

1. Ngo, H. T., Clements, P., Easton, C. J., Pham, D.-T., Lincoln, S. F., Supramolecular

Chemistry of Pyronines B and Y, β-Cyclodextrin and Linked β-Cyclodextrin Dimers,

Aust. J. Chem., 2010; 63, 687-692.

2. Pham, D.-T., Ngo, H. T., Lincoln, S. F., May, B. L., Easton, C. J., Synthesis of C6A-to-

C6A and C3A-to-C3A Diamide Linked γ-Cyclodextrin Dimers, Tetrahedron, 2010, 66,

2895-2898.

a1172507

Text Box

A Ngo, H. T., Clements, P., Easton, C. J., Pham, D.-T. & Lincoln, S. F. (2010) Supramolecular Chemistry of Pyronines B and Y, β-Cyclodextrin and Linked β-Cyclodextrin Dimers, Australian Journal of Chemistry, v. 63(4), pp. 687-692

a1172507

Text Box

A NOTE: This publication is included in the print copy of the thesis held in the University of Adelaide Library. A It is also available online to authorised users at: A http://dx.doi.org/10.1071/CH09467 A

http://dx.doi.org/10.1071/CH09467

a1172507

Text Box

A Pham, D.-T., Ngo, H. T., Lincoln, S. F., May, B. L. & Easton, C. J. (2010) Synthesis of C6A-to- C6A and C3A-to-C3A Diamide Linked γ-Cyclodextrin Dimers. Tetrahedron, v. 66(15), pp. 2895-2898

a1172507

Text Box

A NOTE: This publication is included in the print copy of the thesis held in the University of Adelaide Library. A It is also available online to authorised users at: A http://dx.doi.org/10.1016/j.tet.2010.02.005 A

http://dx.doi.org/10.1016/j.tet.2010.02.005

Documents

SUPRAMOLECULAR CHEMISTRY OF BETA– AND GAMMA– … · SUPRAMOLECULAR CHEMISTRY OF ... important to understand and control the aqueous supramolecular assembly of polymers at the