Bis amide-aromatic-ureas - Highly effective hydro- and organogelator systems

Article abstract of DOI:10.1016/j.tet.2014.09.017

A series of hydro- and organo-supergelators have been synthesised via coupling of simple bis aromatic-ureas via alkyl amide linkages. These bis amide-aromatic-ureas exhibited reduced critical gelator concentrations, improved gelator stability, mechanical

Full text of DOI:10.1016/j.tet.2014.09.017

Tetrahedron xxx (2014) 1e9
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Bis amide-aromatic-ureasdhighly effective hydro- and
organogelator systems
a
a
b
a,
*
B.C. Baker , A.L. Acton , G.C. Stevens , W. Hayes
a
Department of Chemistry, University of Reading, Whiteknights, Reading RG6 6AD, UK
Gnosys Global Ltd., 17-18 Frederick Sanger Road, The Surrey Research Park, Guildford, Surrey GU2 7YD, UK
b
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of hydro- and organo-supergelators have been synthesised via coupling of simple bis aromatic-
ureas via alkyl amide linkages. These bis amide-aromatic-ureas exhibited reduced critical gelator
concentrations, improved gelator stability, mechanical and dye removal properties for potential use in
water purification, in comparison to related bis aromatic-ureas. Systematic structure studies via variation
of the bis amide-aromatic-urea linker length as well as functionalization of the terminal aromatic
moieties have enabled control over the gel properties.
Received 11 April 2014
Received in revised form 30 July 2014
Accepted 5 September 2014
Available online xxx
Keywords:
Hydrogelator
Organogelator
Supergelator
Amide
Ó 2014 Elsevier Ltd. All rights reserved.
Urea
1
. Introduction
units that are responsible for gel assembly.18a There have been
further successes in exploring the effects of creating bolaamphi-
21,22
Low Molecular Weight Gelators (LMWG) are systems that will
self-assemble via non-covalent interactions (i.e., hydrogen bond-
philic gelators
from the corresponding mono amphiphilic
2
3
hydrogelators and multicomponent linked gelator systems,
ing, aromatic
p
e
p
stacking and van der Waals forces of attraction)
which exhibit increased gelating efficiency. Furthermore, detailed
1,2
under the required stimuli to form supramolecular networks that
studies of the linker unit length between the established gelator
3
,4
24
entrap large volumes of solvent. As a result of their highly ef-
fective self-assembly, LMWGs are able to gel solvents in very low
percentage weights when compared to their polymeric counter-
parts5 (indeed gels formed at weight % values <1 are referred to as
units have enabled the properties of the gels thus formed to be
2
5
tailored.
Herein we report the effects of coupling bis aromatic-urea based
,6
pH tuneable hydrogelator units (1) that have dye uptake capabil-
7
8
13
supergelators ). LMWGs have found application in drug delivery,
ities, via alkyl amide linkages (Fig. 1). Several structural modifi-
9
10,11
12
tissue engineering,
catalysis,
electronics
and water
cations of this gelator motif have been carried out to assess the
purification.1
3,14
optimal group interactions and have also led to the creation of
14
The recent interest in aromatic urea-based gelator systems has
arisen in the light of the effectiveness of the association of urea
moieties, permitting aggregation of fibrils and entrapment of sol-
3
,4,13e15
vents to afford stable gels.
Linking aromatic units directly to
A
ureas facilitates an increase in thickness, strengthening fibrils
formed, on account of
pep stacking perpendicular to the axis of
fibril growth.4
,13e17
Notable independent studies conducted by the groups of
Weiss,18 van Esch, Miravet and Escuder, respectively, have
19
20
demonstrated the positive effects of linking recognised structural
B
*
Corresponding author. Tel.: þ44 118 378 6491; fax: þ44 118 378 6331; e-mail
Fig. 1. A) Hydrogelator 5-(3-(4-nitrophenyl)ureido)isophthalic acid (1); B) Generalised
address: w.c.hayes@reading.ac.uk (W. Hayes).
2 2 2
structure of the novel linked bis amide-aromatic-ureas (R1e4¼CO H/CO Et/H/NO ).
http://dx.doi.org/10.1016/j.tet.2014.09.017
0
040-4020/Ó 2014 Elsevier Ltd. All rights reserved.
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2
B.C. Baker et al. / Tetrahedron xxx (2014) 1e9
organogels.15 In designing these new linked gelators, the aromatic
and urea moieties of 1 were retained as terminal units whilst
bridging alkyl chains were used to couple the bis aromatic-ureas
together via amide residues. The functionality on the terminal ar-
omatic unit group was also varied within this study.
2.2. Gelation studies
The tetra-acid bis amide-aromatic-ureas 2aec were found to be
7
supergelators, readily soluble in basic solutions (pH>12) yet upon
acidification (pH<4) they formed translucent gels (Fig. 2) at wt %
values<1. Interestingly, it was found that only bis amide-aromatic-
urea 2a formed stable gels upon direct pH switching achieved via
addition of HCl(aq). Stable hydrogel systems of 2b and 2c were
2
2
. Results and discussion
2
9
accessed via the established glucono-d-lactone protocol to pro-
.1. Synthesis
duce rapid (ca.<1 h) formation of homogeneous gel. In contrast, the
para-di-acid bis amide-aromatic-ureas 3aec (Table 1) failed to gel
under analogous conditions.
The bis amide-aromatic-ureas 2ae9c were generated from the
corresponding bis aromatic-urea precursors, which featured an
aniline moiety 10e17 (Scheme 1, Table 1). The aniline functional-
ised bis aromatic-ureas 10e17 were linked together using
commercially available diacyl chlorides with increasing alkyl chain
lengths (glutaryl, adipoyl and sebacoyl) in a variety of solvents
Scheme 1). Acid functionalised bis amide-aromatic-ureas 2ae3c
were recovered via precipitation into acid media (pH<4) whereas
the ester, nitro and unfunctionalised bis amide-aromatic-ureas
ae9c precipitated from the reaction medium.
This preliminary study revealed that stable hydrogels in the case
of 2aec were afforded at higher wt % values in comparison to the
13
bis aromatic-urea 1 (Table 2). The trend of decreasing CGC with
increasing linker chain length indicated a surfactant like driving
force in the self-assembly process for these gels, analogous to re-
(
4
,21e25
ported hydrogelators studies,
(the anti-parallel/parallel
stacking effects of linked urea based gelators, evident in other
2
4
studies, have been discounted in these systems as 2aec feature
4
3
Scheme 1. Generic synthesis of bis amide-aromatic-ureas 2ae9c from bis aromatic-ureas 10e17 with (i) DMF, (ii) NMP or (iii) THF, each with Et N at room temperature, 24 h, with
the respective diacyl chloride.
Table 1
Structural conformations of bis amide-aromatic-ureas 2ae9c (where ieiii are syn-
thetic routes reported in Scheme 1) and corresponding bis aromatic-urea precursor
10e17
Bis amide-aromatic-urea Bis aromatic-urea
R
1
R
2
R
3
R
4
2
3
4
5
6
7
8
9
aeci
10
11
12
13
14
15
16
17
H
H
H
H
H
NO
H
CO
H
2
H
H
CO
H
CO
H
H
CO
H
2
H
ii
aec
aec
aec
aec
aec
aec
aec
2
H
iii
iii
iii
iii
iii
iii
CO
H
2
Et
CO
H
2
Et
2
Et
H
H
NO
H
H
H
H
H
2
2
H
NO
H
2
Fig. 2. Hydrogelators (a) 2a, (b) 2b, (c) 2c, at their respective critical gelator concen-
tration (CGC) after pH switching.
Bis aromatic-ureas 10e13 were synthesised via procedures
14,26
Table 2
based upon previous reports.
The bis aromatic-ureas 14 and
13
Gelation studies for 1 and 2aec, G¼gel each accessed via the glucono-
d-lactone
1
5e17 were synthesised according to a variation upon a procedure
protocol.29
2
7
28
described by Rodriguez et al. and Denny et al., respectively.
Addition of a solution of an isocyanate dropwise to a solution of 1,4-
phenyldiamine afforded the bis aromatic-ureas. A ratio of 2:1
Gelator
Obs
CGC [mM]
wt % gel
1
G
G
G
G
0.9
7.4
4.1
1.8
0.03
0.54
0.30
0.14
2
2
2
a
b
c
(
(
diamine:isocyanate), in conjunction with reduced temperature
<10 C), was used to minimize the bis-substitution of the diamine.
ꢀ
Successful synthesis of each bis amide-aromatic-urea 2ae9c
was confirmed via
a range of analytical techniques (see
Supplementary data for analytical data). For example, the synthesis
1
of the amide links in 4c was confirmed by a combination of H NMR
both odd and even numbers of methylene units yet self-assemble
and IR spectroscopic analysis, revealing a key amide proton reso-
nance at 8.64 ppm and the characteristic amide carbonyl stretch at
effectively). The hydrogels 2aec exhibited a thermal stability
(Tgel)>100 C and a vial inversion stability of >1 week. Interestingly,
the bis amide-aromatic-urea 2c was able to thermogelate in both
neutral and basic water, however, under these conditions the CGC
value required was in excess of 38 mM.
ꢀ
ꢁ1
13
1654 cm , respectively. Further verification was provided by
C
NMR spectroscopic analysis with the key carbonyl amide resonance
evident at 170.8 ppm.
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B.C. Baker et al. / Tetrahedron xxx (2014) 1e9
3
The importance of the aromatic ring adjacent to both the amide
and urea moieties in hydrogels of 2aec was assessed via synthesis
of the tetra-acid 18 (Fig. 3). Disappointingly, attempts to generate
stable hydrogels of 18 via pH switching resulted only in pre-
cipitation. It is feasible that this amide linked aromatic unit limits
self-assembly of the urea groups via internal hydrogen bonding (as
In contrast, the trend of increasing efficiency of the gelators
4aec and 6aec as the chain length decreased was attributed to
solubility changes rather than an increased ability to self-assem-
ble. Although the CGC values increase as the length of the alkyl
chain was extended it became progressively more difficult to dis-
solve the gelator, with temperatures >Tgel required in all of the
solvents in linked systems reported in Table 3.
17
4
,13e15
observed in related bis aromatic-urea systems
) and thus in
the case of 18 precipitation occurs (hydrophobic effects were dis-
counted as bis-amide-aromatic-ureas featuring both shorter, 2a,
and longer, 2c, alkyl chains successfully gelated, Table 2).
The tetra-ester, 4aec, and meta-nitro, 8aec, bis amide-
aromatic-ureas formed stable opaque gels at wt % values <1 in
combinations of water and polar aprotic solvents (20% v/v)
(Table 4). The decrease in CGC values as the linker chain length
increased indicated a surfactant like effect, with irregular sized
vesicles forming upon addition of the second solvent (see Fig. 5).
The vesicles were found to degrade as the water in the bulk me-
dium evaporated under the analysis conditions used in the optical
or scanning electron (ESEM) microscopic studies, but they re-
formed rapidly following addition of water post-analysis (see
Supplementary data), observations that are analogous to other or-
Fig. 3. The tetra-acid 18.
30,31
ganic/aqueous LMWG systems that have been reported.
This
property was also observed upon addition of other miscible polar
solvents (i.e., methanol, ethanol and acetonitrile). In each case, the
resultant gels exhibited a vial inversion stability of greater than 1
week.
The tetra-ester, 4aec, and unfunctionalised bis amide-aromatic-
ureas (6aec) proved to be highly effective organo-supergelators
within functionalized aromatic solvents, affording translucent
gels (Fig. 4) at wt % values <1 (Table 3). In each case, the gels exhibit
a vial inversion stability >1 week. In contrast, the para-di-ester,
7
Table 4
5
aec, and para, ortho and meta-nitro, 7ae9c, bis amide-aromatic-
ureas failed to gel in any of the solvents reported in Table 3.
Gelation studies for bis amide-aromatic-ureas 4ae9c and bis aromatic-urea 12
where;
G¼Gel,
GP¼gelatinous
precipitate,
S¼solution,
P¼precipitate,
DMSO¼dimethyl sulfoxide, NMP¼N-methyl-2-pyrrolidone, DMF¼dimethylforma-
mide, gelation stimulated via addition of water in 4:1 ratio with respect to the or-
ganic solvent
Gelator DMSO
NMP
DMF
Obs CGC [mM] wt % Obs CGC [mM] wt % Obs CGC [mM] wt %
4
4
4
8
8
8
1
a
b
c
a
b
c
G
G
G
G
G
G
GP
11.9
10.8
4.6
17.2
10.1
5.1
0.93
0.85
0.39
G
G
G
33.4
26.0
16.5
d
2.74 GP
d
d
2.17
1.47
d
G
G
G
G
G
S
48.1
35.3
13.4
12.2
6.5
4.28
3.35
0.90
0.83
0.48
d
1.02 GP
0.61
0.33
d
G
G
GP
15.0
7.32
0.96
0.51
d
2
d
d
d
It was found that derivatives of 8aec whereby the nitro end
group was located in the ortho (7aec) or para position (9aec) with
respect to the urea functionality, failed to gel in any of the solvents
via thermal or solvent triggering effects (indeed, these compounds
formed precipitates in all of the gel studies). Analogous results were
obtained in gelation tests for derivatives of 4aec in which the ester
groups are situated in the para position (5aec). From this simple
gelation assay, it is clear that a key structural motif for effective
gelation (both in aqueous and organic media) is the location of
hydrogen bond acceptor groups meta to the urea moiety. It is thus
proposed that interactions between these hydrogen bond acceptor
moieties and the effective hydrogen bond acceptor/donor capabil-
Fig. 4. Organogelator systems of (a) 12 in 1,2 DCB, (b) 4a in 1,2 DCB and (c) 6a in
nitrobenzene all at their CGC values (see Table 3).
Table 3
Gelation studies for thermogelators bis amide-aromatic-ureas 4aec, 6aec and bis
aromatic-urea 12 where: G¼Gel, GP¼gelatinous precipitate, S¼sol, P¼precipitate,
1,2 DCB¼1,2 dichlorobenzene, 1,2,4 TCB¼1,2,4 trichlorobenzene
Gelator
1,2 DCB
1,2,4 TCB
Nitrobenzene
Obs CGC
wt % Obs CGC
wt % Obs
CGC
wt %
[
mM]
[mM]
[mM]
4
4
4
4
6
6
6
1
a
b
c
a
b
c
G
G
G
P
P
P
2.2
2.3
4.2
0.14
0.15
0.29
d
G
G
G
S
GP
P
4.1
4.0
4.4
d
0.23
0.23
0.27
d
P
P
P
G
G
G
GP
d
d
ity of the bis aromatic-urea moiety facilitate self-assembly, and
d
d
hence gelation, when located in the meta position. Conversely,
when the hydrogen bond acceptor moieties are situated in the or-
tho or para position on the aromatic rings, precipitation results.
However, in the case of the unfunctionalised bis amide-aromatic-
ureas 6aec, which feature phenyl end groups, specific solvents
with hydrogen bond acceptor moieties are required to effect
gelation.
d
d
d
5.81
5.31
7.73
d
0.27
0.25
0.40
d
d
d
d
d
d
d
d
d
2
G
64.6
1.85
G
75.4
1.92
The di-ester bis aromatic-urea 12 was also found to be able to
The presence of hydrogen bond interactions in these assemblies
was confirmed by solid state infrared spectroscopic analysis of
compounds 2aec, 4aec and 8aec (see Supplementary data). The
decreased frequencies of the NeH and C]O amide and urea ab-
sorptions when compared to those found in non-hydrogen bonded
moieties are as a result of ordering induced through hydrogen
effectively gelate in organic solvents (Table 3), however, linking of
the molecules with alkyl chains to afford 4aec increased the ge-
lation efficiency (Fig. 4). This was attributed to the increased
propensity of the gelators to assemble into fibrils as observed with
2
0b,21,22
other aliphatic systems.
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4
B.C. Baker et al. / Tetrahedron xxx (2014) 1e9
Fig. 5. Optical micrographs of the gel of 4c in water/DMSO (20% v/v) at its CGC, revealing micelle formation; (a) scale bar 300 mm, (b) scale bar 50 mm.
bonding.3
2,33
The result is consistent with structural analysis of 113
and 6aec also do not gel in 1,2-dichlorobenzene. However, use of
the Kamlet Taft parameters did not successfully predict suitable
gelating solvents for 4aec and 6aec therefore revealing the limi-
and its analogues.14
3
4c
tation of this approach.
2
.3. Solvent parameter analysis
The tetra-ester, 4aec, and meta-nitro 8aec bis amide-aromatic-
ureas only dissolved in solvents with high hydrogen bonding
The use of solubility parameters such as Hildebrand, Hasen,
KamleteTaft and FloryeHuggins have been employed effectively in
accepting parameters (
b>0.45). Gelation was then achieved after
increasing the value (via addition of water) in order to cause
a
the analysis of the assembly mechanisms operating in gel net-
3
4
34a,35
precipitation of the gelator (Table 4). However, stable gels of para-
ester. 5aec, ortho-nitro 7aec and para-nitro 9aec could not be
realised via this approach, again highlighting the necessity of the
interaction between the meta withdrawing group on terminal ar-
omatic moiety and the urea moieties in successful gelators.
works. KamleteTaft solvent parameters
(see Supplementary
data) have, in this study, also allowed further investigation of the
interactions within the organogels thus formed. It is apparent from
gelation studies on 4aec, 6aec and 8aec that solvents with low
hydrogen bonding donating parameters (a) are desirable for gela-
tion (Table 2). This trend is consistent with observations from
14
previous studies dthe urea moiety is an efficient source of hy-
2.4. Rheological studies
drogen bond donation and thus solvents interfering with this in-
termolecular
interaction
serve
to
disrupt
the
gel
All of the gels reported revealed similar rheological profiles with
network.4
A direct comparison of the hydrogen bonding accepting pa-
rameters ( ) of 1,2-dichlorobenzene and nitrobenzene provided
,15,34c,36,37
a storage modulus (G ) that was an order of magnitude greater than
0
0
0
the loss modulus (G ) (Fig. 6) (indicating successful gelation rather
3
4a
b
than the presence of highly viscous fluids). The storage modulus
insights into the networks formed in gels of tetra-ester, 4aec, and
non-functionalised, 6aec, bis amide-aromatic-ureas. It is proposed
that the successful gelation of 1,2-dichlorobenzene by 4aec arises
was also independent of shear rates above certain thresholds and
3
8,39
thus these gels behave as Bingham type fluids.
Rheological
studies on the gels were performed at a concentration of 20 mM
ꢀ
as a result of the low
b
value of the solvent and the hydrogen bond
using both cone (1 ) and plate geometries at 1% strain (see
accepting ability of the terminal ester groups, allowing the in-
termolecular interaction of hydrogen bond withdrawing and
Supplementary data) to allow comparison with previous
studies.
13e15
ꢀ
0
00
Fig. 6. Rheological data (1 cone geometry) for (A) hydrogelator 2c (20 mM), (B) organogelator 4a in 1,2 DCB (20 mM), G : : and G : ꢂ.
donating groups and ultimately self-assembly of the gelator.
Absence of the hydrogen bond accepting ester moieties, i.e., bis
amide-aromatic-ureas 6aec, thus favours gelation of solvents with
Table 5 demonstrates the correlation of increasing chain length
against increasing storage modulus (G ) in hydrogelator systems of
tetra-acid bis amide-aromatic-ureas 2aec. The gel 2c exhibited
higher G’ values when compared to the bis aromatic-urea 1,
forming more physically robust gels at equal concentrations, thus
demonstrating the ability to improve this characteristic of the gel
0
larger
b values (as achieved in nitrobenzene) that are able to in-
teract with the gelators hydrogen bond donating moieties. This
conclusion was reinforced since 4aec failed to gel in nitrobenzene
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B.C. Baker et al. / Tetrahedron xxx (2014) 1e9
5
Table 5
2.5. Dye absorption studies
14
Maximum storage and loss moduli (kPa) for hydrogelators 1 and 2aec each at
ꢀ
20 mM (1 cone geometry)
Tetra-acid bis amide-aromatic-ureas 2aec exhibited dye ab-
sorption capabilities relevant to contamination extraction tech-
niques based on molecular gelators
Removal of a model containing methylene blue from aqueous
media was monitored via UV/vis spectroscopic analysis, employing
the absorption maxima at 667 nm of the dye to calculate the degree
of extraction (Fig. 7).
0
00
Gelator
G
G
4
3e48
49
1
294
3.3
281
327
31.5
0.4
41.8
44.5
and linked gelators.
2
2
2
a
b
c
system. The maximum storage modulus value for 2c also reveals an
14
improvement in comparison to the parent hydrogelator 1 and
2
5
related bis urea hydrogelator systems, though not as substantial
an increase as observed for a structurally related chiral linked urea
gelator.2 It is proposed that the sudden decrease in G between bis
0d
0
amide-aromatic-ureas 2a and 2b occurs as a result of the latter’s
19,39e42
decreased ability to cross-link gel fibrils.
The mechanical studies of thermally stimulated organogels of
tetra-ester, 4aec, and meta-nitro, 6aec, bis amide-aromatic-ureas
demonstrate an inverse correlation than that observed for hydro-
0
gelators 2aec (i.e., a decrease in G as the linker chain length in-
creases) (Table 6). In stark contrast, the gels 4aec generated in 1,2
DCB exhibited a reversal of this trend indicating a different gela-
3
8e42
toresolvent interaction/aggregation mechanism.
Gels 4a and
4
b in 1,2 DCB, 4b and 4c in 1,2,4 TCB and 6c in nitrobenzene exhibit
Fig. 7. UV/vis absorption spectra of stirred solution of aqueous methylene blue
(250 mL, 0.25 mg L ) up to 48 h after addition of 1 mL of hydrogelator 2a (1 mL,
10 mM).
0
ꢁ1
higher G values, at identical concentrations to the organogelator
analogues of the parental gelator 1. The bis aromatic-urea 12 was
15
not used as it could not form stable gels at concentrations ca.
2
0 mM and thus could not be directly compared within this study.
Interestingly none of the hydrogelators demonstrated dye re-
moval capabilities at gelator concentration >20 mM, in contrast to
14,15
the parental bis aromatic urea and analogues.
It is proposed that
Table 6
this is as a result of transformations in the mode of self-assembly of
the gelator at higher concentrations (see microscopic images in
Maximum storage and loss moduli (kPa) for thermally stimulated organogelators
4
8
aec and 6aec (20 mM) and solvent variation stimulated organogelators 4aec and
aec (20 mM) (gelation initiated via addition of water) (1 cone geometry)
3
,40,50
ꢀ
Supplementary data),
hence not affording an extended aro-
matic face, or permeability within the gel structure, necessary for
Gelator
1,2 DCB
1,2,4 TCB
Nitrobenzene
DMSO
13,14,44,49
intercalation of the aromatic dye molecules.
It is also noted
0
00
0
00
0
00
0
00
G
G
G
G
G
G
G
G
that gels of both 4aec and 8aec in DMSO, NMP and DMF failed to
remove methylene blue from solution.
4
4
4
6
6
6
8
8
8
a
b
c
a
b
c
a
b
c
348.5
299.0
103.1
d
88.8
79.8
14.9
d
61.3
167.0
173.8
d
12.9
38.3
24.3
d
d
d
188.6
290.1
2032.0
d
43.0
54.6
234.5
d
d
d
To overcome this trend the gelators were used at a concentra-
tion of 10 mM, (removing methylene blue from 1 mg/250 mL
aqueous solutions). The gelators did not show any visual increase in
dye removal capabilities when compared to systems of 1, verified
by weight dye uptake calculations from UV/vis spectroscopic
analysis (Table 7). However, as a result of the decreased concen-
tration used and the increased molecular weight of the linked
d
d
80.9
88.9
398.1
d
8.2
18.3
36.7
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
d
148.3
1694.2
2595.0
17.3
250.4
477.0
d
d
d
d
d
d
d
d
d
d
d
d
ꢁ
1
gelators they have a more effective mol mol uptake of the dye
than the initial gelator 1 (as would be expected, doubling the
amount of aromatic moieties per molecule, hence increasing sites
The mechanical properties of gels of tetra-ester, 4aec, and meta-
nitro 8aec bis amide-aromatic-ureas formed in DMSO (via addition
13,14
available for gel intercalation).
of water to the organic solution) were also compared at concen-
0
trations of 20 mM (Table 6). The G reduction as the linker length
Table 7
Maximum absorption of methylene blue dye from water from hydrogelators 114
20 mM) and 2aec (10 mM)
decreased was attributed to a decrease in surfactant like in-
teractions, an increase in solubility, and hence a weakening of the
(
19,21,40
gel.
The organogelators 4c and 8c exhibited vastly increased
Gelator
Weight dye
Dye uptake per molecule
uptake [mg gꢁ1]
of gelator [mol mol
ꢁ1
]
0
G values when compared to the thermogelator counterparts. The
possibility of evaporation of the water component on the rheom-
eter plate to afford more viscous gels or even inhomogenous
samples, as well as movement of the gels under the cone, was
decreased by repeating the two sweeps using a flat plate and oil
around the outside of the sample. The data obtained via this
method was in agreement with that reported in Table 6 (see
1
1020
128
56
1.1
2.9
1.3
2.9
2
2
2
a
b
c
117
0
Supplementary data). The larger G values observed for gels of
Unfortunately direct correlation was not observed between the
8
aec, when compared to 4aec, were assigned to the larger hy-
chain length of the alkyl linker unit and dye uptake. For example, in
the case of hydrogelator 2b, UV/vis spectroscopic analysis revealed
a decreased dye uptake in comparison to the other systems (see
Supplementary data).
drogen bond acceptor tendencies of the nitro groups, in compari-
son to the ester, resulting in increased self-assembly efficiency of
the systems.1
3e15,38e42
Please cite this article in press as: Baker, B.C.; et al., Tetrahedron (2014), http://dx.doi.org/10.1016/j.tet.2014.09.017

6
B.C. Baker et al. / Tetrahedron xxx (2014) 1e9
ꢀ
ꢀ
Further spectroscopic studies were undertaken on the most
cone with 1 gradient) (25 C). Dye uptake measurements were
carried out via extraction of 2 mL sample from dye/gelator mix-
efficient dye extractor, bis amide-aromatic-urea hydrogelator 2a, in
order to elucidate the mode of interaction between the host and
guest. NMR spectroscopic studies revealed downfield shifts in the
urea protons resonances with increasing dye concentration sug-
gesting hydrogen bonding as a contributing factor to dye absorp-
tures, filtering through sterile syringe filters (0.2 mm, 33 mm).
Thermal stimulated organogel systems of 4aec and 6aec were
achieved via sonication of the gelator in the desired solvent and
subsequent heating. Solvent stimulated organogel systems of 4aeb
and 8aec were achieved via dissolution of the gelator in the desired
solvent (0.8 mL) and addition of polar solvent (0.2 mL). pH stimu-
lated hydrogelator systems of 2aec were achieved via dissolution
of the gelator in NaOH(aq) (0.5 mL, 0.1 M) followed by addition of
tion (see Supplementary data). To ascertain the impact of
pep
stacking on dye intercalation, a hydrogel of 2a (10 mM, 1 mL) was
ꢁ1
2
prepared in D O and a solution of spermine (1 mL, 0.25 mg L ) was
deposited on the gel. After a period of 48 h analysis of the gel and
sol separately showed that absorption of the aliphatic tetracation
spermine from the solution had not occurred thus supporting the
hypothesis that intercalation is responsible for dye removal rather
than electrostatic interactions. The hydrogelator also failed to
remove methylene orange from solution, as monitored by UVevis
spectroscopy, yet was able to partially remove methylene green
from solution (see Supplementary data), indicating selection for
positively charged aromatic based molecule adsorption as dem-
glucono-d-lactone (0.5 mL, 0.2 M). The systems were then left for
2 h to acidify and gel. Critical Gelation Concentration (CGC) de-
termination was carried out in a 2 mL screw top glass vial, mini-
mum gelator mass was determined to nearest 1 mg, then varied
every 0.2 mg to obtain increased accuracy of CGC.
Generic procedure for synthesis of bis amide-aromatic-ureas
2aec and 3aec was achieved via dissolution of 10 (0.20 g,
0.6 mmol) and 11 (0.16 g, 0.6 mmol), respectively, in anhydrous
DMF (30 mL) or NMP (30 mL) respectively, with triethlyamine
13
onstrated in dye removal studies involving 1.
. Conclusions
It has been demonstrated that a range of both hydro- and
(
0.25 mL, 1.8 mmol), followed by addition of respective diacyl
chloride (glutaryl chloride 38.3 L, 0.3 mmol/adipoyl chloride
3.6 L, 0.3 mmol/sebacoyl chloride 64.1 L, 0.3 mmol) then stirred
3
m
4
m
m
for 24 h under inert conditions. Precipitating into acid solutions
organo-supergelators can be synthesised via linking a known
gelator motif. The process of linking creates a significant im-
provement on the initial gelling properties. Control over the linked
gelators CGC and mechanical properties has been demonstrated via
variations of the alkyl linker lengths. It is proposed that function-
alization of the links could also result in greater manipulation of the
gelator properties, especially dye absorption.
It has also been demonstrated that by varying the number and
position of groups capable of hydrogen bonding on the terminal
aromatic ring, the gelators properties can also be altered. Further-
more it has been shown that the increase of aromatic moieties via
linking known hydrogelators can facilitate increased efficiency of
dye removal from aqueous media.
(pH<4) afforded:
0
4.1.1. 5,5 -(((((Glutaroylbis(azanediyl))bis(4,1-phenylene))bis(azane-
diyl))bis(carbonyl)) bis(azanediyl))diisophthalic acid (2a). Brown
powder, (0.17 g, 79%). Mp 229 C (dec); IR (ATR)/cm 3299, 2962,
ꢀ
ꢁ1
1
2567, 1692, 1657, 1559, 1516, 1403, 1299, 1259, 1225, 758, 665;
NMR (DMSO-d
)¼9.84 (s, 2H), 9.19 (s, 2H), 8.77 (s, 2H), 8.26 (s, 4H),
8.09 (s, 2H), 7.53 (m, 4H), 7.41 (m, 4H), 2.37 (t, 4H, J¼7.2 Hz), 1.92
H
6
13
(t, 2H, J¼5.2 Hz) ppm; C NMR (DMSO-d )¼170.4, 166.7, 152.5,
6
140.6, 134.6, 134.0, 131.8, 123.1, 122.5, 119.6, 119.0, 35.5, 21.0 ppm;
þ
MS (ESI) m/z [MþH ] calculated for C35
31 6
H N O12 727.1994, found
727.2000.
0
4
.1.2. 5,5 -(((((Adipoylbis(azanediyl))bis(4,1-phenylene))bis(azane-
4
4
. Experimental
diyl))bis(carbonyl)) bis(azanediyl))diisophthalic acid (2b). Brown
powder, (0.20 g, 91%). Mp 209 C (dec); IR (ATR)/cm 3286,
3087, 2959, 2923, 2856, 1710, 1691, 1604, 1557, 1514, 1199, 754,
ꢀ
ꢁ1
.1. General
1
6
66; H NMR (DMSO-d
6
)¼9.80 (s, 2H), 9.08 (s, 2H), 8.65 (s, 2H),
All of the chemicals and solvents were purchased from Sigma
8.26 (s, 4H), 8.06 (s 2H), 7.50 (m, 4H), 7.39 (m, 4H), 2.31 (s, 4H),
1.62 (s, 4H) ppm; C NMR (DMSO-d
134.5, 134.0, 131.7, 123.4, 122.5, 119.6, 119.0, 36.2, 25.0 ppm; MS
13
Aldrich and used as purchased. THF was distilled from sodium and
benzophenone under inert conditions prior to use. All other sol-
vents were used as supplied. NMR spectra were obtained using
Bruker Nanobay 400 and Bruker DPX 400 (operating at 400 MHz
and 100 MHz for H NMR and C NMR, respectively). All samples
were prepared in DMSO-d and dissolution was achieved with
6
)¼170.7, 166.6, 152.5, 140.6,
þ
(ESI) m/z [MþH ] calculated for C36
33 6
H N O12 741.2151, found
741.2156.
1
13
0
6
4.1.3. 5,5 -(((((Decanedioylbis(azanediyl))bis(4,1-phenylene))bis(a-
slight heating and sonication (5e10 min). Mass spectra were gen-
erated from Thermo-Fisher Scientific Orbitrap XL LCMS (operating
in electrospray mode)dsamples were prepared in either 0.1 M
zanediyl)) bis(carbonyl))bis(azanediyl))diisophthalic acid (2c). Dark
brown powder, (0.20 g, 84%). Mp 197 C (dec); IR (ATR)/cm 3287,
3051, 2926, 2851, 2578, 1690, 1655, 1551, 1514, 1401, 1201, 1109,
ꢀ
ꢁ1
ꢁ1
1
NaOH(aq) or DMSO (for direct injection) (1 mg mL ). A Perkin
Elmer 100 FT-IR (diamond ATR sampling attachment) was
employed for IR spectroscopic analysis. All the samples in the
characterisation were in powder form. UV spectra were recorded
using a Varian Cary 300 Bio or a PerkinElmer Lambda 25 UV/Vis
Spectrometer. Samples were analysed in quartz curettes with
a 5.0 mm path length and were baseline corrected with respect to
a blank cell with the appropriate solvent. Thermogravimetric
Analysis employed TA Instruments TGA Q50 attached to TGA heat
exchanger, platinum crucible and an aluminium TA-Tzero pan
1061, 756, 663; H NMR (DMSO-d
6
)¼9.79 (s, 2H), 9.09 (s, 2H), 8.67
(s, 2H), 8.28 (s, 4H), 8.08 (s, 2H), 7.51 (m, 4H), 7.39 (m, 4H), 2.28 (t,
13
4H, J¼7.2 Hz), 1.59 (s, 4H), 1.31 (s, 8H) ppm; C NMR (DMSO-d )¼
6
170.8, 166.7, 152.5, 140.6, 134.5, 134.1, 131.8, 123.1, 122.5, 119.6, 118.9,
þ
36.3, 28.7, 28.7, 25.2 ppm; MS (ESI) m/z [MþH ] calculated for
40 41 6
C H N O12 797.2777, found 797.2783.
0
4.1.4. 4,4 -(((((Glutaroylbis(azanediyl))bis(4,1-phenylene))bis(azane-
diyl))bis(carbonyl)) bis(azanediyl))dibenzoic acid (3a). Cream pow-
ꢀ
ꢁ1
der, (0.11 g, 59%). Mp 213 C (dec); IR (ATR)/cm ; 3278, 2962,
ꢀ
ꢀ
(
ramp rate 15 C/min to 500 C). Differential scanning calorimetry
2541, 1645, 1595, 1553, 1509, 1401, 1303, 1226, 1169, 1107, 1052,
1
analysis employed TA DSC Q2000 with TA Refrigerated Cooling
837, 760; H NMR (DMSO-d
6
)¼9.84 (s, 2H), 9.19 (s, 2H), 8.89 (s,
ꢀ
System 90 (aluminium TA-Tzero pans and lids) (ramp rate 15 C/
2H), 7.86 (m, 4H), 7.55 (m, 8H), 7.40 (m, 4H), 2.35 (m, 4H), 1.91 (t,
13
min). Rheological analysis employed TA Instruments AR 2000
rheometer operating in the cone and plate geometry (20 mm steel
2H, J¼6.8 Hz) ppm; C NMR (DMSO-d
6
)¼170.4, 167.0, 152.2, 144.1,
134.5, 134.0, 130.5, 123.4, 119.7, 118.8, 117.1, 35.5, 21.0 ppm; MS
Please cite this article in press as: Baker, B.C.; et al., Tetrahedron (2014), http://dx.doi.org/10.1016/j.tet.2014.09.017

B.C. Baker et al. / Tetrahedron xxx (2014) 1e9
7
þ
(t, 12H, J¼7.2 Hz), 1.31 (s, 8H) ppm; 13C NMR (DMSO-d
(
6
ESI) m/z [MþH ] calculated for C33
H
31
N
6
O
8
639.2198, found
6
)¼170.8,
39.2196.
164.9, 152.5, 140.9, 134.3, 134.2, 130.9, 122.5, 122.4, 119.6, 119.1, 61.2,
þ
3
6.3, 28.7, 28.7, 25.2, 14.1 ppm; MS (ESI) m/z [MþH ] calculated for
0
4
.1.5. 4,4 -(((((Adipoylbis(azanediyl))bis(4,1-phenylene))bis(azane-
48 57 6
C H N O12 909.4029, found 909.4036.
diyl))bis(carbonyl)) bis(azanediyl))dibenzoic acid (3b). Cream pow-
1
ꢀ
0
der, (0.15 g, at 80% purity, estimated from H NMR). Mp 222
C
4.1.10. Diethyl 4,4 -(((((glutaroylbis(azanediyl))bis(4,1-phenylene))
ꢁ
1
(
dec); IR (ATR)/cm ; 3272, 2939, 2864, 2679, 2550, 1679, 1646,
bis(azanediyl)) bis(carbonyl))bis(azanediyl))dibenzoate (5a). White
powder, (0.11 g, 80%). Mp 231 C (dec); IR (ATR)/cm 3285, 3049,
2982, 2942, 2904, 1712, 1650, 1596, 1557, 1511, 1402, 1367, 1304,
1274, 1227, 1169, 1102, 1017, 835, 761; H NMR (DMSO-d
1
ꢀ
ꢁ1
1
594,1556,1510,1403,1294,1172, 1109, 1041, 907, 841, 760; H NMR
DMSO-d
)¼9.81 (s, 2H), 9.12 (s, 2H), 8.80 (s, 2H), 7.86 (m, 4H), 7.54
m, 8H), 7.38 (m, 4H), 2.28 (m, 5H), 1.57 (m, 5H) ppm; C NMR
DMSO-d
)¼174.3, 170.6, 167.0, 152.4, 144.3, 134.7, 130.5, 123.2,
(
(
(
6
13
1
6
)¼9.85 (s,
6
2H), 9.06 (s, 2H), 8.71 (s, 2H), 7.88 (m, 4H), 7.57 (m, 4H), 7.53 (m,
1
19.8, 119.7, 118.5, 116.8, 36.0, 33.4, 24.7, 24.1 ppm; MS (ESI) m/z
4H), 7.39 (m, 4H), 4.29 (q, 4H, J¼8.0 Hz), 2.37 (m, 4H), 1.90 (m, 2H),
þ
13
[
MþH ] calculated for C34
H N
33 6
O
8
652.2355, found 653.2358.
1.32 (t, 6H, J¼8.0 Hz) ppm; C NMR (DMSO-d
6
)¼170.4, 165.4, 152.2,
1
44.4, 130.3, 122.5, 119.7, 118.8, 117.2, 60.2, 35.5, 21.0, 14.2 ppm; MS
0
þ
4
.1.6. 4,4 -(((((Decanedioylbis(azanediyl))bis(4,1-phenylene))bis(a-
(ESI) m/z [MþH ] calculated for C37
39 6 8
H N O 695.2824, found
zanediyl))bis(carbonyl)) bis(azanediyl))dibenzoic acid (3c). Brown
695.2827.
ꢀ
ꢁ1
powder, (0.16 g, 75%). Mp 217 C (dec); IR (ATR)/cm 3285, 2927,
851, 1802, 1692, 1648, 1594, 1562, 1511, 1404, 1305, 1171, 1043, 839,
)¼9.78 (s, 2H), 9.05 (s, 2H),
.73 (s, 2H), 7.86 (m, 4H), 7.53 (m, 8H), 7.37 (m, 4H), 2.27 (t, 4H,
0
2
7
8
4.1.11. Diethyl 4,4 -(((((adipoylbis(azanediyl))bis(4,1-phenylene))bi-
s(azanediyl)) bis(carbonyl))bis(azanediyl))dibenzoate (5b). White
powder, (0.11 g, 79%). Mp 211 C (dec); IR (ATR)/cm 3263, 2945,
2870, 1712, 1647, 1552, 1511, 1401, 1273, 1212, 1169, 1075, 834, 760;
42; MS (ESI) m/z; 1H NMR (DMSO-d
6
ꢀ
ꢁ1
13
J¼7.2 Hz), 1.59 (s, 4H), 1.29 (s, 8H) ppm; C NMR (DMSO-d
6
)¼170.8,
1
1
2
67.0, 152.2, 144.4, 134.4, 134.1, 130.5, 123.4, 119.6, 118.8, 117.1, 36.3,
H NMR (DMSO-d
6
)¼9.85 (s, 2H), 9.06 (s, 2H) 8.71 (s, 2H), 7.87 (m,
þ
8.7 (d), 25.2 ppm; MS (ESI) m/z [MþH ] calculated for C38
H
41
N
6
O
8
4H), 7.57 (m, 4H), 7.51 (m, 4H), 7.37 (m, 4H), 4.28 (q, 4H, J¼8.0 Hz),
13
7
08.2980, found 708.2980.
2.32 (m, 4H), 1.63 (m, 4H), 1.31 (t, 6H, J¼8.0 Hz) ppm; C NMR
Generic procedure for synthesis of bis amide-aromatic-ureas
(DMSO-d
6
)¼170.8, 165.5, 152.2, 144.4, 134.4, 134.0, 130.3, 122.6,
þ
4
aec, 5aec, 6aec, 7aec, 8aec and 9aec were achieved via dis-
119.7, 118.9, 117.2, 60.3, 36.2, 24.9, 14.2 ppm; MS (ESI) m/z [MþH ]
solution of bis aromatic-ureas 12 (0.15 g, 0.4 mmol), 13 (0.12 g,
.4 mmol), 14 (0.10 g, 0.4 mmol), 15e17 (0.15 g, 0.5 mmol), re-
spectively, in anhydrous THF (40 mL) and triethlyamine (69.7 L,
.5 mmol), followed by addition of respective diacyl chloride
glutaryl chloride 25.5 L, 0.2 mmol/adipoyl chloride 29.3 L,
.2 mmol/sebacoyl chloride 42.7 L, 0.2 mmol) then stirred for
4 h under inert conditions. The products were isolated as
calculated for C38
H
41
N
6
O
8
709.2980, found 709.2980.
0
0
m
4.1.12. Diethyl 4,4 -(((((decanedioylbis(azanediyl))bis(4,1-
phenylene))bis(azanediyl)) bis(carbonyl))bis(azanediyl))dibenzoate
(5c). White powder (0.09 g, 63%). Mp 216 C (dec); IR (ATR)/cm
3285, 2928, 2850, 1714, 1650, 1597, 1562, 1514, 1403, 1306, 1278,
0
ꢀ
ꢁ1
(
m
m
0
2
m
1
1230, 1172, 1107, 1019, 838, 761; H NMR (DMSO-d
9.06 (s, 2H), 8.70 (s, 2H) 7.86 (m, 4H), 7.55 (m, 4H), 7.50 (m, 4H),
.36 (m, 4H), 4.27 (q, 4H, J¼8.0 Hz), 2.26 (m, 4H), 1.57 (m, 4H)
6
)¼9.76 (s, 2H),
precipitates.
7
0
13
4
.1.7. Tetraethyl 5,5 -(((((glutaroylbis(azanediyl))bis(4,1-phenylene))
1.30 (m, 14H) ppm; C NMR (DMSO-d
6
)¼170.8, 165.4, 152.2,
bis(azanediyl)) bis(carbonyl))bis(azanediyl))diisophthalate (4a).
144.4, 130.3, 122.5, 119.6, 118.8, 117.1, 60.2, 36.3, 28.7, 14.2 ppm;
ꢀ
ꢁ1
þ
Cream powder, (0.15 g, 91%). Mp 228 C (dec); IR (ATR)/cm 3708,
676, 3354, 3267, 2982, 2939, 2923, 1724, 1660, 1650, 1562, 1228,
MS (ESI) m/z [MþH ] calculated for C42
49 6 8
H N O 765.3606, found
3
765.3607.
1
1
058,1033,1018, 753; H NMR (DMSO-d
6
)¼9.86 (s, 2H), 9.21 (s, 2H),
1
5
8
.65 (s, 2H), 8.33 (s, 4H), 8.08 (s, 2H), 7.55 (m, 4H), 7.40 (m, 4H), 4.37
4.1.13. N ,N -Bis(4-(3-phenylureido)phenyl)glutaramide (6a). White
powder, (0.09 g, 82%). Mp 201 C (dec); IR (ATR)/cm 3310, 3284,
3040, 2959,1659,1637,1557,1538,1445,1403,1298,1227,1169, 739,
692, 637, 619; H NMR (DMSO-d
ꢀ
ꢁ1
(
1
1
1
q, 8H, J¼6.8 Hz), 2.37 (t, 4H, J¼6.8 Hz),1.92 (t, 2H, J¼6.8 Hz),1.35 (q,
13
2H, J¼6.8 Hz) ppm; C NMR (DMSO-d
6
)¼170.4,164.9,152.5,140.9,
1
34.4, 134.1, 130.9, 122.5, 122.4, 119.6, 119.1, 61.2, 35.5, 21.0,
6
)¼9.82 (s, 2H), 8.61 (s, 2H), 8.56 (s,
þ
4.1 ppm; MS (ESI) m/z [MþH ] calculated for C43
H
47
N
6
O
12
2H), 7.52 (m, 4H), 7.45 (m, 4H), 7.37 (m, 4H), 7.28 (m, 4H), 6.97 (m,
13
8
39.3246, found 839.3248.
4H), 2.36 (t, 4H, J¼7.2 Hz), 1.91 (quin, 2H, J¼7.2 Hz) ppm; C NMR
(DMSO-d
6
)¼170.4, 152.5,139.8,134.9,133.7,128.7,121.7,119.7,118.6,
0
þ
4
.1.8. Tetraethyl 5,5 -(((((adipoylbis(azanediyl))bis(4,1-phenylene))
118.1, 35.5, 21.1 ppm; MS (ESI) m/z [MþH ] calculated for
bis(azanediyl)) bis(carbonyl))bis(azanediyl))diisophthalate (4b).
31 31 6 4
C H N O 551.2401, found 551.2413.
ꢀ
ꢁ1
Cream powder, (0.16 g, 88%). Mp 214 C (dec); IR (ATR)/cm 3708,
675, 3352, 3288, 2982, 2946, 2923, 1719, 1656, 1655, 1554,1515,
1
6
3
4.1.14. N ,N -Bis(4-(3-phenylureido)phenyl)adipamide (6b). White
powder, (0.11 g, 98%). Mp 249 C (dec); IR (ATR)/cm 3308, 3260,
3149, 3040, 2940, 2875,1644,1557,1512,1403,1299, 1228, 842, 726,
690, 642; H NMR (DMSO-d
7.51 (m, 4H), 7.50 (m, 4H), 7.37 (m, 4H), 7.28 (m, 4H), 6.97 (m, 4H),
2.32 (s, 4H), 1.64 (s, 4H) ppm; C NMR (DMSO-d
139.8,134.9,133.7,128.7,121.7,119.7,118.6,118.1, 36.2, 25.0 ppm; MS
(ESI) m/z [MþH ] calculated for C32
1
ꢀ
ꢁ1
1
227, 1214, 1057, 1033, 1018, 752; H NMR (DMSO-d
6
)¼9.83 (s, 2H),
9
.21 (s, 2H), 8.64 (s, 2H), 8.33 (s, 4H), 8.08 (s, 2H), 7.53 (m, 4H), 7.40
1
(
m, 4H), 4.39 (q, 8H, J¼6.8 Hz), 2.33 (s, 4H), 2.10 (s, 4H), 1.35 (t, 12H,
6
)¼9.79 (s, 2H), 8.60 (s, 2H), 8.56 (s, 2H),
13
J¼8.4 Hz) ppm; C NMR (DMSO-d
6
)¼170.7, 164.9, 152.4, 140.9,
13
1
1
8
34.4, 134.1, 130.9, 122.5, 122.4, 119.6, 119.1, 61.1, 36.2, 25.0,
6
)¼170.6, 152.5,
þ
4.1 ppm; MS (ESI) m/z [MþH ] calculated for C44
H
49
N
6
O
12
þ
53.3403, found 853.3412.
33 6 4
H N O 565.2558, found
565.2565.
0
4
.1.9. Tetraethyl 5,5 -(((((decanedioylbis(azanediyl))bis(4,1-
1
10
phenylene))bis(azanediyl)) bis(carbonyl))bis(azanediyl))diisophthalate
4.1.15. N ,N -Bis(4-(3-phenylureido)phenyl)decanediamide
(6c). White powder, (0.12 g, 90%). Mp 254 C (dec); IR (ATR)/cm
3308, 3287, 3043, 2927, 2850, 1624, 1562, 1514, 1404, 1230, 741, 691,
638, 625; H NMR (DMSO-d
7.49 (m, 4H), 7.45 (m, 4H), 7.37 (m, 4H), 7.28 (m, 4H), 6.96 (m, 4H),
ꢀ
ꢁ1
ꢀ
ꢁ1
(
4c). Brown powder, (0.17 g, 93%). Mp 204 C (dec); IR (ATR)/cm
3
708, 3681, 3351, 3286, 2982, 2938, 2923, 1719, 1654, 1652, 1554,
1
1
1
515, 1228, 1057, 1033, 1017, 752; H NMR (DMSO-d
.22 (s, 2H), 8.64 (s, 2H), 8.32 (m, 4H), 8.08 (s, 2H), 7.52 (m, 4H), 7.39
d, 4H) 4.36 (q, 8H, J¼6.8 Hz), 2.28 (t, 4H, J¼7.2 Hz), 1.60 (s, 4H) 1.35
6
)¼9.77 (s, 2H),
6
)¼9.75 (s, 2H), 8.75 (s, 2H), 8.70 (s, 2H),
9
(
13
2.28 (t, 4H, J¼7.2 Hz), 1.60 (s, 4H), 1.32 (s, 8H) ppm; C NMR
Please cite this article in press as: Baker, B.C.; et al., Tetrahedron (2014), http://dx.doi.org/10.1016/j.tet.2014.09.017

8
B.C. Baker et al. / Tetrahedron xxx (2014) 1e9
þ
(
1
C
DMSO-d
6
)¼170.8, 152.7, 140.0, 135.1, 133.6, 128.7, 121.5, 119.7, 118.5,
36.3, 28.7, 28.7, 25.2 ppm; MS (ESI) m/z [MþH ] calculated for
þ
18.1, 36.3, 28.7, 28.7, 25.2 ppm; MS (ESI) m/z [MþH ] calculated for
C
36
39
H N
8
O
8
711.2885, found 711.2886.
H
36 41
N
6
O
4
621.3184, found 621.3198.
1
5
4
.1.22. N ,N -Bis(4-(3-(4-nitrophenyl)ureido)phenyl)glutaramide
(9a). Yellow powder, (0.11 g, 78%). Mp 213 C (dec); IR (ATR)/cm
3368, 3271, 3153, 2930, 2851, 1654, 1550, 1503, 1401, 1326, 1303,
1
5
ꢀ
ꢁ1
4
.1.16. N ,N -Bis(4-(3-(2-nitrophenyl)ureido)phenyl)glutaramide
;
ꢀ
ꢁ1
(7a). Yellow powder, (0.10 g, 85%), Mp 203 C (dec); IR (ATR)/cm
1
3
1
7
275, 3140, 3051, 3036, 2935, 2362, 2322, 1660, 1609, 1586, 1559,
1215, 1176, 1111, 854, 834, 747; H NMR (DMSO-d
6
)¼9.84 (s, 2H),
541, 1496, 1461, 1435, 1403, 1336, 1282, 1221, 1145, 844, 779, 783,
9.39 (s, 2H), 8.83 (s, 2H), 8.17 (m, 4H), 7.67 (m, 4H), 7.53 (m, 4H),
1
39; H NMR (DMSO-d
6
)¼9.88 (s, 2H), 9.79 (s, 2H), 9.59 (s, 2H), 8.32
7.38 (m, 4H), 2.35 (t, 4H, J¼7.3 Hz), 1.88 (quin, 2H, J¼6.9 Hz) ppm;
13
(
(
d
m, 2H), 8.10 (m, 2H), 7.70 (m, 2H), 7.56 (m, 4H), 7.42 (m, 4H), 7.19
m, 4H), 2.38 (t, 4H, J¼7.2 Hz), 1.92 (m, 2H) ppm; C NMR (DMSO-
C NMR (DMSO-d
6
)¼170.4, 151.9, 146.5, 140.9, 134.4, 134.1, 125.1,
13
þ
119.7, 119.1, 117.3, 35.5, 30.7 ppm; MS (ESI) m/z [MþH ] calculated
6
)¼170.4, 151.8, 137.5, 135.0, 134.9, 134.3, 125.4, 122.6, 122.1, 119.7,
for C31
29 8 8
H N O 641.2103, found 641.2110.
þ
1
C
19.0, 35.5, 21.0 ppm; MS (ESI) m/z [MþH ] calculated for
1
6
31
29
H N
8
O
8
641.2103, found 641.2101.
4.1.23. N ,N -Bis(4-(3-(4-nitrophenyl)ureido)phenyl)adipamide
9b). Yellow powder, (0.11 g, 82%). Mp 234 C (dec); IR (ATR)/cm
3367, 3270, 2929,2850, 1654, 1549, 1495, 1401, 1325, 1300, 1214,
ꢀ
ꢁ1
(
;
1
6
4
.1.17. N ,N -Bis(4-(3-(2-nitrophenyl)ureido)phenyl)adipamide
ꢀ
ꢁ1
1
(7b). Yellow powder, (0.12 g, 93%), Mp 220 C (dec); IR (ATR)/cm
1178, 1110, 834, 747; H NMR (DMSO-d
6
)¼9.81 (s, 2H), 9.38 (s, 2H),
3
1
262, 3146, 3041, 2923, 2364, 2336, 1651, 1584, 1558, 1543, 1499,
456, 1434, 1401, 1337, 1283, 1253, 1213, 1147, 842, 782, 736;
8.82 (s, 2H), 8.17 (m, 4H), 7.67 (m, 4H), 7.52 (m, 4H), 7.37 (m, 4H),
1
13
H
2.31 (s, 4H), 1.62 (s, 4H) ppm; C NMR (DMSO-d
146.5,140.9,134.3,134.1,125.1,119.7, 119.1,117.3, 36.2, 25.0 ppm; MS
6
)¼170.7, 151.9,
NMR (DMSO-d
2
2
1
2
6
)¼9.84 (s, 2H), 9.78 (s, 2H), 9.59 (s, 2H), 8.32 (m,
þ
H), 8.10 (m, 2H), 7.71 (m, 2H), 7.55 (m, 4H), 7.42 (m, 4H), 7.19 (m,
(ESI) m/z [MþH ] calculated for C32
31 8 8
H N O 655.2259, found
H), 2.33 (s, 4H), 1.65 (s, 4H) ppm; 13C NMR (DMSO-d
655.2272.
6
)¼170.7,
51.8, 137.5, 135.1, 135.0, 134.3, 125.4, 122.4, 122.2, 119.7, 119.0, 36.2,
þ
1
10
5.0 ppm; MS (ESI) m/z [MþH ] calculated for C32
H
31
N
8
O
8
4.1.24. N ,N -Bis(4-(3-(4-nitrophenyl)ureido)phenyl)decanediamide
(9c). Yellow powder, (0.12 g, 91%). Mp 226 C (dec); IR (ATR)/cm
370, 3280, 2930, 2919, 2850, 1654, 1550, 1503, 1493, 1401, 1326,
1303, 1227,1215, 1176, 1111, 853, 834,747; H NMR (DMSO-d
(s, 2H), 9.40 (s, 2H), 8.83 (s, 2H), 8.20 (m, 4H), 7.70 (m, 4H), 7.54 (m,
ꢀ
ꢁ1
6
55.2259, found 655.2256.
3
1
10
1
4
.1.18. N ,N -Bis(4-(3-(2-nitrophenyl)ureido)phenyl)decanediamide
6
)¼9.80
ꢀ
ꢁ1
(7c). Yellow powder, (0.09 g, 73%), Mp 229 C (dec); IR (ATR)/cm
13
3
1
267, 2913, 2845, 2602, 2496, 2361, 2337, 1654, 1589, 1584, 1554,
543, 1498, 1456, 1435, 1402, 1337, 1283, 1222, 838, 791, 735;
4H), 7.40 (m, 4H), 2.28 (s, 4H) 1.60 (s, 4H),1.32 (s, 8H) ppm; C NMR
1
H
(DMSO-d
6
)¼170.9,151.9, 146.5, 140.9, 134.4, 134.0, 125.1, 119.7, 119.1,
þ
NMR (DMSO-d
2
6
)¼9.83 (m, 4H), 9.61 (s, 2H), 8.30 (m, 2H), 8.10 (m,
117.3, 36.3, 28.7, 28.7, 25.14 ppm; MS (ESI) m/z [MþH ] calculated
H), 7.70 (m, 2H), 7.54 (m, 4H), 7.40 (m, 4H), 7.21 (m, 2H), 2.29
39 8 8
for C36H N O 711.2885, found 711.2886.
13
(
d
t, 4H, J¼7.2 Hz), 1.60 (m, 4H), 1.30 (m, 8H) ppm; C NMR (DMSO-
6
)¼170.9, 151.8, 137.7, 134.9, 134.3, 125.4, 122.6, 122.1, 119.6, 119.0,
4.1.25. 1-(4-Aminophenyl)-3-phenylurea
(14). Phenylisocyanate
(273 L, 2.5 mmol) in anhydrous THF (25 mL) was added dropwise
to a solution of 1,4-phenyldiamine (0.30 g, 2.8 mmol) in anhydrous
THF (25 mL, 5 C). The product was then recovered in vacuo as
a white powder, (0.54 g, 95%). Mp 155 C (dec); IR (ATR)/cm 3452,
3364, 3291, 3036, 2940, 1621, 1593, 1551, 1509, 1303, 1228, 835, 799,
þ
3
C
6.3, 28.7, 25.2 ppm; MS (ESI) m/z [MþH ] calculated for
m
H
36 39
N
8
O
8
711.2885, found 711.2885.
ꢀ
1
5
ꢀ
ꢁ1
4
.1.19. N ,N -Bis(4-(3-(3-nitrophenyl)ureido)phenyl)glutaramide
ꢀ
ꢁ1
(8a). Yellow powder, (0.09 g, 74%). Mp 240 C (dec); IR (ATR)/cm
1
3
1
9
367, 3276, 3096, 2985, 1737, 1653, 1556, 1513, 1404, 1345, 1301,
228, 1044, 802, 733, 681, 606; H NMR (DMSO-d
.20 (s, 2H), 8.78 (s, 2H), 8.58 (s, 2H), 7.83 (m, 2H), 7.73 (m, 2H), 7.53
738, 691, 667; H NMR (DMSO-d
6
)¼8.53 (s,1H), 8.19 (s,1H), 7.43 (m,
1
6
)¼9.86 (s, 2H),
2H), 7.27 (m, 2H), 7.08 (m, 2H), 6.94 (m, 1H), 6.52 (m, 2H), 4.79 (s,
13
2H) ppm; C NMR (DMSO-d
6
)¼152.9, 144.0, 140.2, 128.7, 128.5,
þ
(
m, 6H), 7.41 (m, 4H), 2.37 (t, 4H, J¼6.8 Hz), 1.59 (t, 2H, J¼7.2 Hz)
121.3, 120.7, 117.9, 114.1 ppm; MS (ESI) m/z [MþH ] calculated for
13
ppm; C NMR (DMSO-d
6
)¼170.4, 152.4, 148.1, 141.2, 134.3, 134.2,
C
13
H
14
N
3
O 228.1131, found 228.1131.
1
33.9, 130.0, 124.2, 119.6, 119.4, 119.0, 116.1, 112.0, 35.5, 21.0 ppm;
Bis aromatic-ureas 15e17 were synthesised by addition of the
þ
MS (ESI) m/z [MþH ] calculated for C31
H
29
N
8
O
8
641.2103, found
respective 2/3/4-nitrophenlyisocyanate (0.45 g, 2.7 mmol) in an-
hydrous THF (25 mL) in a dropwise fashion to a solution of 1,4-
phenyldiamine (0.30 g, 2.8 mmol) in anhydrous THF (25 mL,
6
41.2103.
1
6
ꢀ
4
.1.20. N ,N -Bis(4-(3-(3-nitrophenyl)ureido)phenyl)adipamide
5 C). The product was then recovered in vacuo.
ꢀ
ꢁ1
(8b). Yellow powder, (0.11 g, 84%). Mp 199 C (dec); IR (ATR)/cm
3
259, 2937, 2871, 1648, 1554, 1513, 1403, 1347, 1298, 1238, 1178,
4.1.26. 1-(4-Aminophenyl)-3-(2-nitrophenyl)urea (15). Yellow pow-
der, (0.65 g, 89%), Mp 184 C (dec); IR (ATR)/cm 3325, 3288, 3045,
2841, 2539, 2325,1715,1661,1582,1549,1499,1420,1335,1280,1257,
1
ꢀ
ꢁ1
1
2
4
013, 842, 797, 732, 679; H NMR (DMSO-d
6
)¼9.84 (s, 2H), 9.19 (s,
H), 8.76 (s, 2H), 7.82 (m, 2H), 7.70 (m, 2H), 7.56 (m, 6H), 7.41 (m,
13
1
H), 2.33 (s, 4H), 1.64 (s, 4H) ppm; C NMR (DMSO-d
6
)¼170.7,
1118, 1090, 1038, 861, 789, 733; H NMR (DMSO-d
6
)¼10.11 (s, 1H),
152.6, 148.1, 141.4, 130.0, 124.2, 119.7, 119.6, 119.3, 119.0, 116.0, 112.0,
9.93 (s, 2H), 9.68 (s 1H), 8.22 (m, 1H) 8.10 (m, 1H), 7.72 (m, 1H), 7.58
(m, 2H), 7.27 (m, 3H) ppm; C NMR (DMSO-d
134.8, 134.4, 125.4, 123.2, 122.8, 122.5, 119.4 ppm; MS (ESI) m/z
þ
13
3
C
6.2, 25.0, 24.9 ppm; MS (ESI) m/z [MþH ] calculated for
6
)¼151.9, 138.5, 138.2,
H
32 31
N
8
O
8
655.2259, found 655.2258.
þ
[
MþH ] calculated for C13
13 4 3
H N O 273.0982, found 273.0984.
1
10
4.1.21. N ,N -Bis(4-(3-(3-nitrophenyl)ureido)phenyl)decanediamide
ꢀ
ꢁ1
(8c). Brown powder, (0.12 g, 90%). Mp 211 C (dec); IR (ATR)/cm
4.1.27. 1-(4-Aminophenyl)-3-(3-nitrophenyl)urea (16). Yellow solid,
ꢀ
ꢁ1
3
367, 3286, 2924, 2925, 2850, 1654, 1554, 1514, 1403, 1345, 1303,
(0.69 g, 94%), Mp 198 C (dec); IR (ATR)/cm 3403, 3338, 3299,
1
1
2
2
230, 843, 804, 734, 681; H NMR (DMSO-d
H), 9.01 (s, 2H), 8.57 (s, 2H), 7.81 (m, 2H), 7.72 (m, 2H), 7.58 (m,
6
)¼9.82 (s, 2H), 9.52 (s,
1669, 1606, 1553, 1522, 1511, 1435, 1347, 1311, 1279, 1236, 884, 842,
1
804, 738, 681; H NMR (DMSO-d
6
)¼9.07 (s, 1H), 8.57 (s, 1H), 8.31 (s,
H), 7.51 (m, 4H), 7.39 (m, 4H), 2.28 (t, 4H, J¼7.2 Hz), 1.59 (s, 4H),
1H), 7.78 (m, 1H), 7.67 (m, 1H), 7.56 (m, 1H), 7.09 (m, 2H), 6.53 (m,
2H), 4.83 (s, 2H) ppm; C NMR (DMSO-d
141.5, 129.9, 127.8, 124.0, 121.2, 119.4, 115.7, 114.0, 111.8 ppm; MS
.31 (s, 8H) ppm; 13C NMR (DMSO-d
13
)¼152.7, 148.1, 144.5,
1
6
)¼170.9, 152.5, 148.1, 141.2,
6
134.4, 134.1, 133.9, 130.0, 124.0, 119.7, 119.4, 119.2, 118.9, 116.0, 111.8,
Please cite this article in press as: Baker, B.C.; et al., Tetrahedron (2014), http://dx.doi.org/10.1016/j.tet.2014.09.017

B.C. Baker et al. / Tetrahedron xxx (2014) 1e9
9
þ
(
2
ESI) m/z [MþH ] calculated for C13
H
13
N
4
O
3
273.0982, found
13. Rodríguez-Llansola, F.; Escuder, B.; Miravet, J. F.; Hermida-Merino, D.; Hamley,
I. W.; Cardin, C. J.; Hayes, W. Chem. Commun. 2010, 7960e7962.
73.0982.
14. Wood, D. M.; Greenland, B. W.; Acton, A. L.; Rodríguez-Llansola, F.; Murray, C.
A.; Cardin, C. J.; Miravet, J. F.; Escuder, B.; Hamley, I. W.; Hayes, W. Chem.dEur. J.
2012, 18, 2692e2699.
15. Bajaj, N.; Hart, L. R.; Greenland, B. W.; Hayes, W. Macromol. Symp. 2013, 329,
4
.1.28. 1-(4-Aminophenyl)-3-(4-nitrophenyl)urea (17). Yellow solid,
ꢀ
ꢁ1
(
0.65 g, 88%), Mp 161 C (dec); IR (ATR)/cm 3402, 3319, 3071,
700, 1597, 1539, 1501, 1488, 1338, 1234, 1204, 1112, 853, 853, 749;
H NMR (DMSO-d
118e124.
1
1
6. Hunter, C. A.; Sanders, J. K. M. J. Am. Chem. Soc. 1990, 112, 5525e5534.
17. Chen, J.; Kampf, J. W.; McNeil, A. J. Langmuir 2010, 26, 13076e13080.
18. (a) George, M.; Tan, G.; John, V. T.; Weiss, R. G. Chem.dEur. J. 2005, 11,
1
6
)¼9.29 (s, 1H), 8.42 (s, 1H), 8.18 (m, 2H), 7.67 (m,
13
2
d
H), 7.11 (m, 2H), 6.54 (m, 2H), 4.87 (s, 2H) ppm; C NMR (DMSO-
3243e3254; (b) Abdallah, D. J.; Weiss, R. G. Adv. Mater. 2000, 12, 1237e1247.
6
)¼152.1, 146.9,144.7,140.6,127.6,125.1,121.1, 117.1, 114.0 ppm; MS
1
9. van Esch, J. H.; De Feyter, S.; Kellogg, R. M.; De Schryver, F.; Feringa, B. L. Chem.
dEur. J. 1997, 3, 1238e1243.
þ
(
2
ESI) m/z [MþH ] calculated for C13
H
13
N
4
O
3
273.0982, found
2
0. (a) Miravet, J. F.; Escuder, B. Org. Lett. 2005, 7, 4791e4794; (b) Escuder, B.;
LLusar, M.; Miravet, J. F. J. Org. Chem. 2006, 71, 7747e7752; (c) Hirst, A. R.;
Coates, I. A.; Boucheteau, T. R.; Miravet, J. F.; Escuder, B.; Castelletto, V.; Hamley,
I. W.; Smith, D. K. J. Am. Chem. Soc. 2008, 130, 9113e9121; (d) Rodríguez-
Llansola, F.; Hermida-Merino, D.; Nieto-Ortega, B.; Ramírez, F. J.; Navarrete, J. T.;
Casado, J.; Hamley, I. W.; Escuder, B.; Hayes, W.; Miravet, J. F. Chem.dEur. J.
73.0982.
0
.1.29. 5,5 -(((Hexane-1,6-diylbis(azanediyl))bis(carbonyl))bis(aza-
4
nediyl))diisophthalic acid (18). 5-Aminoisophthalic acid (0.15 g,
.8 mmol) was added to a solution of 1,6-Diisocyanatohexane
64.6 L, 0.4 mmol) in anhydrous DMF (50 mL) and stirred under
0
(
2012, 46, 14725e14731.
m
21. van Esch, J. H.; Feringa, B. L. Angew. Chem., Int. Ed. 2000, 39, 2263e2266.
22. Jung, J. H.; Shinkai, S.; Shimizu, T. Chem.dEur. J. 2002, 8, 2684e2690.
23. Nakazawa, I.; Masuda, M.; Okada, Y.; Hanada, T.; Yase, K.; Asai, M.; Shimizu, T.
Langmuir 1999, 15, 4757e4764.
inert conditions for 24 h. The solvent was removed in vacuo to af-
ford 18 as a white powder (0.14 g, 64%). Mp 189 C (dec); IR (ATR)/
cm 3306, 2935, 2853, 1695, 1645, 1600, 1558, 1513, 1403, 1297,
ꢀ
ꢁ
1
2
4. Buerkle, L. E.; Rowan, S. J. Chem. Soc. Rev. 2012, 41, 6089e6102.
25. Lloyd, G. O.; Piepenbrock, M. M.; Foster, J. A.; Clarke, N.; Steed, J. W. Soft Matter
012, 8, 204e216.
1
1207, 1105, 1059, 757, 647; H NMR (DMSO-d
6
)¼8.97 (s, 2H), 8.23 (s,
2
4
H), 8.02 (s, 2H), 6.35 (s, 2H), 3.11 (s, 4H), 1.47 (s, 4H), 1.33 (s, 4H)
2
6. San-Jos eꢀ , N.; G oꢀ mez-Valdemoro, A.; García, F. C.; De La Pe n~ a, J. L.; Serna, F.;
García, J. M. J. Polym. Sci., Part A: Polym. Chem. 2007, 45, 5398e5407.
13
ppm; C NMR (DMSO-d
3
C
6
)¼166.9, 155.0, 141.2, 132.0, 122.4, 121.9,
þ
0.0, 29.7, 26.1 ppm; MS (ESI) m/z [MþH ] calculated for
27. Rodriguez, F.; Rozas, I.; Brun, R.; Kaiser, M.; Nguyen, B.; Wilson, W. D.; Garcia, R.
N.; Dardonville, C. J. Med. Chem. 2008, 51, 909e923.
24 27 4
H N O10 531.1722, found 531.1719.
2
8. Denny, W. A.; Atwell, G. J.; Baguley, B. C.; Cain, B. F. J. Med. Chem. 1979, 22,
34e150.
29. Weng, W.; Beck, J. B.; Jamieson, A. M.; Rowan, S. J. J. Am. Chem. Soc. 2006, 128,
1663e11672.
1
Acknowledgements
1
3
0. Yan, N.; Xu, Z.; Diehn, K. K.; Raghavan, S. R.; Fang, Y.; Weiss, R. G. J. Am. Chem.
Soc. 2013, 135, 8989e8999.
The authors would like to acknowledge financial support from
the University of Reading and Gnosys Global Ltd. (PhD studentship
for B.C.B.). In addition, the University of Reading is acknowledged
for granting access to instrumentation in the Chemical Analysis
Facility. Professor I. W. Hamley is acknowledged for access to rhe-
ological facilities.
31. Laouini, A.; Jaafar-Maalej, C.; Limayem-Blouza, I.; Sfar, S.; Charcosset, C.; Fessi,
H. J. Colloid Sci. Biotechnol. 2012, 1, 147e168.
32. (a) Teo, L. S.; Chen, C. Y.; Kuo, J. F. Macromolecules 1997, 30, 1793e1799; (b)
Yilg o€ r, E.; Burgaz, E.; Yurtsever, E.; Yilg o€ r, I. Polymer 2000, 41, 849e857.
ꢀ
33. Silverstein, R. M.; Webster, F. X. Spectrometric Identification of Organic Com-
pounds; John Wiley & Sons: New York, NY, 1997.
3
4. (a) Hirst, A. R.; Smith, D. K. Langmuir 2004, 20, 10851e10857; (b) Barton, A. F. M.
Chem. Rev. 1975, 75, 731e753; (c) Edwards, W.; Lagadec, C. A.; Smith, D. K. Soft
Matter 2011, 7, 110e117.
Supplementary data
35. Adams, D. J.; Butler, M. F.; Frith, W. J.; Kirkland, M.; Mullen, L.; Sanderson, P. Soft
Matter 2009, 5, 1856e1862.
6. Kamlet, M. J.; Abboud, J. L. M.; Abraham, M. H.; Taft, R. W. J. Org. Chem. 1983, 48,
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.tet.2014.09.017.
3
2877e2887.
37. Kamlet, M. J.; Doherty, R. M.; Abraham, M. H.; Carr, P. W.; Doherty, R. F.; Taft, R.
W. J. Phys. Chem. 1987, 91, 1996e2004.
8. Macocosko, C. W. Rheology Principles, Measurements and Applications; Wiley
References and notes
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1
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2. Segarra-Maset, M. D.; Nebot, V. J.; Miravet, J. F.; Escuder, B. Chem. Soc. Rev. 2013,
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4
5
. Terech, P.; Weiss, R. G. Chem. Rev. 1997, 97, 3133e3159.
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4
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Please cite this article in press as: Baker, B.C.; et al., Tetrahedron (2014), http://dx.doi.org/10.1016/j.tet.2014.09.017