Thixotropic twin-dendritic organogelators

Article abstract of DOI:10.1002/chem.200701273

Twin-dendritic organogelators have been prepared through selective functionalization of N-(3-aminopropyl)-1,3-propanediamine (APPDA) with self-assembling dendrons by using 1,1′-carbonyldiimidazole (CDI). Subsequent modification of the APPDA linker provided an additional degree of structural diversity by which to tailor the gelator self-assembly in bulk or in the gel state. These compounds are able to gel cyclohexane, toluene, n-butyl acetate, ethyl acetate, dichloromethane, and tetrahydrofuran. 3,4-Disubstituted apical branching units provided the most efficient organogelators and show a propensity to form thixotropic gels, wherein the gel recovers its elasticity after being subjected to shear. Structural and retrostructural analysis of the twin-dendritic organogelators reveals the bulk structural characteristics to be indicative of the subsequent gel properties. Diverse self-organized arrays were identified in bulk and all are able to form gels, thus indicating the role of quasiequivalence in mediating self-assembly in the gel state. Furthermore, we have found that porous columnar mesophases provide a strategy by which to prepare thixotropic gels. We demonstrate the importance of weak lateral hydrogen bonding within a column stratum versus hydrogen bonding along the length of the column for forming porous columnar mesophases and, by extension, thixotropic gels.

Full text of DOI:10.1002/chem.200701273

FULL PAPER
DOI: 10.1002/chem.200701273
Thixotropic Twin-Dendritic Organogelators
Virgil Percec,*[a] Mihai Peterca,[a, b] Michael E. Yurchenko,[a] Jonathan G. Rudick,[a] and
Paul A. Heiney[b]
Abstract: Twin-dendritic organogela-
tors have been prepared through selec-
tive functionalization of N-(3-amino-
propyl)-1,3-propanediamine (APPDA)
with self-assembling dendrons by using
1,1’-carbonyldiimidazole (CDI). Subse-
quent modification of the APPDA
linker provided an additional degree of
structural diversity by which to tailor
the gelator self-assembly in bulk or in
the gel state. These compounds are
able to gel cyclohexane,toluene, n-
butyl acetate,ethyl acetate,dichloro-
methane,and tetrahydrofuran. 34,-Dis-
ubstituted apical branching units pro-
vided the most efficient organogelators
and show a propensity to form thixo-
tropic gels,wherein the gel recovers its
elasticity after being subjected to shear.
Structural and retrostructural analysis
of the twin-dendritic organogelators re-
veals the bulk structural characteristics
to be indicative of the subsequent gel
are able to form gels,thus indicating
the role of quasiequivalence in media-
ting self-assembly in the gel state. Fur-
thermore,we have found that porous
columnar mesophases provide a strat-
egy by which to prepare thixotropic
gels. We demonstrate the importance
of weak lateral hydrogen bonding
within a column stratum versus hydro-
gen bonding along the length of the
column for forming porous columnar
mesophases and,by extension,thixo-
tropic gels.
properties.
Diverse
self-organized
arrays were identified in bulk and all
Keywords: dendrimers
liquid crystals self-assembly
supramolecular chemistry
·
gels
·
·
·
Introduction
for heating and cooling to reconstitute thermotropic gels.
This makes thixotropic gels more amenable to processing
and manipulation.
Molecular architectures capable of self-assembly in organic
solvents with subsequent self-organization to entrain the
bulk solvent are increasingly common in the pursuit of pro-
grammable organogelators.[1] Serendipity is the most fre-
quent design principle.[1,2] Advancement beyond the gelation
of organic liquids to the precision design of gel properties
remains more elusive.[1,2] Thixotropic gels,wherein the gel
recovers its elasticity after being subjected to shear,present
a self-healing character in the self-assembled and self-organ-
ized structures. As such,these materials eliminate the need
Only a few recent organogel examples display thixotropic
behavior.[3] Self-assembled fibrillar networks are critical to
gelation phenomena,[3] while spherulitic networks facilitate
reorganization after shearing.[3e] Such criteria may be gener-
ally true for the mesoscopic structural origins of thixotropic
gels. We are investigating the relationship between bulk self-
organization of low-molecular-weight organogelators and
the properties of the resulting organogels. Design principles
for and the syntheses of twin-dendritic gelators are elaborat-
ed herein. We report the propensity of porous cylindrical
supramolecular dendrimers to form thixotropic organogels.
The self-assembling twin-dendritic gelators provide a modu-
lar scaffold through which we can match the gelator to a
broad range of solvent polarities. Relationships between the
self-assembly and self-organization events at the nanoscale
and the above-mentioned mesoscale structural features[3e]
are the subjects of further investigation.
[a] Prof. Dr. V. Percec,Dr. M. Peterca,Dr. M. E. Yurchenko,
Dr. J. G. Rudick
Roy & Diana Vagelos Laboratories
Department of Chemistry
University of Pennsylvania
Philadelphia,PA 19104-6323 (USA)
Fax : (+1)215-573-7888
E-mail: percec@sas.upenn.edu
The design and convergent synthesis of the twin-dendritic
organogelators are based upon our previously reported self-
assembling dendrons[4–8] and twin-dendritic and Janus-den-
dritic benzamides.[9] Amphiphilic,self-assembling dendrons
[b] Dr. M. Peterca,Prof. Dr. P. A. Heiney
Department of Physics and Astronomy
University of Pennsylvania
Philadelphia,PA 19104-6396 (USA)
Chem. Eur. J. 2008, 14,909 – 918
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA,Weinheim
909

form either cylindrical[4,5] or spherical[6–8] supramolecular
dendrimers in bulk and solution. The supramolecular den-
drimers self-organize in periodic[4–8] and quasiperiodic[8]
arrays. Symmetric twin-dendritic benzamides and dissym-
metric Janus-dendritic benzamides undergo self-assembly to
form periodic lattices and superlattices.[9] Structural and ret-
rostructural analysis of self-organized arrays in bulk by
using a combination of techniques,including thermal optical
polarized microscopy (TOPM),differential scanning calo-
rimetry (DSC),X-ray diffraction (XRD),and electron den-
sity mapping,allows us to elucidate the mechanisms by
which self-assembly,self-organization,and subsequent func-
tions arise.[4–9] In solution,structural and retrostructural
analysis is achieved by using NMR,CD,and UV/Vis spec-
troscopies.[5]
tocol[10] provided a complex mixture of mono-,di-,and tria-
cylated products. When an excess of activated ester was
used,the principle product was the triacylated species. By
contrast,the use of 11, ’-carbonyldiimidazole (CDI)[11] led to
products acylated only on the primary amines. This had pre-
viously been reported as only possible for aliphatic carboxyl-
ic acids.[11c,d] The selectivity we observe is likely due to the
lower temperatures employed in our reactions. For both re-
actions,the activated acyl intermediate was isolated and
characterized by 1H and 13C NMR spectroscopy and by
MALDI-TOF mass spectrometry,while the reaction prod-
ucts were monitored by TLC and 1H NMR spectroscopy.
The synthetic strategy and corresponding library of twin-
dendritic supramolecular building blocks is summarized in
Scheme 1. Dendritic imidazoles 2a–h were prepared from
the corresponding dendritic carboxylic acids by using an
excess of CDI. The dendritic imidazoles are readily purified
by recrystallization from acetone and can be stored for days
in the absence of moisture. Twin-dendritic APPDA deriva-
tives 3a–h were prepared in 75–93% yields by the reaction
of the dendritic imidazoles with APPDA. Recrystallization
was often sufficient to purify the twin-dendritic APPDA de-
rivatives,although they are amenable to column chromatog-
raphy if needed.
Results and Discussion
Synthesis of the twin-dendritic organogelators: Twin-den-
dritic organogelators were designed by using N-(3-amino-
propyl)-1,3-propanediamine (APPDA) and self-assembling
monodendritic carboxylic acids. Selective condensation of
the primary amines with the dendritic carboxylic acids was
desired. Conditions were optimized for 4-dodecyloxybenzoic
acid (1a) and APPDA. The use of 2-chloro-4,6-dimethoxy-
1,3,5-triazine (CDMT) in N-methylmorpholine (NMM) as
the carboxylate activating agent in a one-pot,two-step pro-
Polar and nonpolar derivatives of the twin-dendritic
APPDA compounds were prepared by reactions with the
secondary amine functionality. Succinimide derivatives 4a,
4b,and 4d–f were prepared by the reaction of 3a, 3b,and
Scheme 1. Synthesis of twin-dendritic organogelators. i) 1,1-carbodiimidazole (CDI), CH2Cl2; ii) N-(3-aminopropyl)-1,3-propanediamine (APPDA), THF;
iii) succinic anhydride,NEt ,THF,60 8C; iv) CDI,THF; v) 3,THF.
3
910
www.chemeurj.org
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA,Weinheim
Chem. Eur. J. 2008, 14,909 – 918

Twin-Dendritic Organogelators
FULL PAPER
3d–f with succinic anhydride. The reactions proceeded with
high yields and the resulting twin-dendritic carboxylic acids
4a, 4b,and 4d–f were purified by recrystallization from ace-
tone. Gelators containing chiral,branched alkyl moieties ex-
hibit a high propensity to form thixotropic gels.[12] Mixed
ureas were prepared by CDI coupling of racemic 2-amino-6-
methylheptane and the twin-dendritic APPDA derivatives
3b, 3d,and 3 f. The resulting twin-dendritic ureas 5b, 5d,
and 5 f were obtained in 87–89% yields. All new materials
were found to be greater than 99% pure by a combination
of 1H NMR spectroscopy,HPLC,TLC,and MALDI-TOF
mass spectrometry.
tration for the formation of a gel was found for those succi-
nimide derivatives than for the corresponding twin-dendritic
APPDA compounds in the same organic solvents. By con-
trast,the chiral alkyl urea derivatives showed enhanced pro-
pensity and efficiency in the gelation of organic solvents. Fi-
nally,we noted that higher generation dendrons carrying an
appropriate number of peripheral alkyl chains were able to
gel the more polar solvents and impart thixotropic behavior
in some cases.
Low-molecular-weight gelators of organic solvents func-
tion by self-assembly to form fibrillar networks.[3] Self-as-
sembly of amphiphilic dendritic dipeptides in solution to
form elongated supramolecules has been previously report-
ed.[5] Other dendritic organogelators have been shown to
self-assemble into bundles of wormlike aggregates.[13] We en-
vision that the twin-dendritic organogelators reported
herein self-assemble into elongated supramolecules similar
to the self-assembling dendritic dipeptides previously report-
ed by our group.[5] Subsequent self-organization of the elon-
gated supramolecules promotes the formation of stable ther-
moreversible and thixotropic gels of organic solvents. This
self-organization is likely manifested as the formation of fi-
brillar bundles in the gel state.
Gelation of organic solvents: Solutions of the twin-dendritic
APPDA derivatives 3a–h,succinimide derivatives 4a, 4b,
and 4d–f,and ureas 5b, 5d,and 5 f were prepared by heat-
ing in various organic solvents with a range of polarities.
The formation of a stable gel upon cooling was identified
visually. Similarly,the presence of thixotropic behavior was
confirmed by the visual observation that the gel reforms
upon standing after being shaken. The results are detailed in
Table 1.
Most of the twin-dendritic compounds are able to form
gels in at least one organic solvent. The more polar solvents,
dichloromethane and THF,are the most difficult to gel. Sim-
ilarly,we less frequently found thixotropic gels for the more
polar solvents. Nonetheless,thixotropic gels of BuOAc and
dichloromethane were obtained.
Evaluation of the gelation properties of the twin-dendritic
APPDA derivatives revealed that 3,4 branching of the aryl
amide moiety was necessary to ensure that gels would form
and were likely to exhibit thixotropic behavior in the less
polar solvents,CyH and PhMe. The incorporation of strong
hydrogen bonding in the succinimide derivatives decreased
the propensity for organogel formation,as indicated by the
lower number of gels obtained. A higher minimum concen-
Structural and retrostructural analysis of the twin-dendritic
gelators in bulk: Phase transitions of the twin-dendritic gela-
tors were identified in bulk by using a combination of DSC
and TOPM. Tentative phase assignments were made on the
basis of the diagnostic textures observed by TOPM. The
phase assignments were confirmed by XRD. Table 2 reports
the phase sequences,transition temperatures,and corre-
sponding enthalpy changes observed. Table 3 presents the
structural and retrostructural analysis of the self-organized
lattices,along with the XRD results.
Significantly greater structural diversity has been obtained
from the present libraries of twin-dendritic gelators than
from previously reported twin-
dendritic and Janus-dendritic
Table 1. Gelation properties of twin-dendritic compounds in various organic solvents.[a]
benzamides.[9] The greater flex-
ibility of the spacer between
the dendrons,as well as the
structural variety of the den-
drons in the library,facilitates
diversity at the self-organized
level through hierarchical self-
assembly. Examples of ther-
moreversible shape change ac-
companied by dramatic differ-
ences in the transmission of
polarized light are found for
3 f, 3g,and 4e. The columnar
lattice is comprised of flat-
taper dendrons,while the cubic
phase is composed of dendrons
adopting a conical shape. The
columnar lattice is optically
anisotropic and therefore bire-
Compound
CyH
PhMe
nBuOAc
EtOAc
CH2Cl2
THF
(4)12G0-APPDA (3a)
A
10[b]
13[c]
S
15,T
20,T
S
P
S
I
10
40,T
S
S
S
5,T
2.5,T
P
S
S
10,T
P
20,T
S
S
P
10
30,T
S
P
P
S
S
S
30
S
80
S
S
S
S
S
S
80,T
S
P
S
S
40
10[c]
5[c]
P
R
P
[c]
H
4
P
C
P
6
P
S
[c]
G
4[c]
P
40[d]
S
A
P
(3,4,5-3,4)12G2-APPDA (3h)
(4)12G0-APPDA-Suc (4a)
G
P
P
P
10[c]
P
S
S
S
S
S
S
S
S
S
10[c]
P
[c]
R
5
C
P
P
S
P
P
G
S
–
–
–
A
S
[d]
[c]
G
15
,
T
15
S
S
[c]
H
2.5 [c],T
2.5
[a] CyH: cyclohexane; P: precipitate forms upon cooling; S: solution persists even after cooling; T: thixotropic
gel; I: compound is insoluble at all temperatures. Values indicate the minimum concentraion [mgmLÀ1] of
twin-dendritic compound required to gel the solvent. [b]Gel forms a precipitate upon standing. [c]Opaque gel
is formed. [d]First a transparent gel is formed,which turns opaque after 2–3 h.
Chem. Eur. J. 2008, 14,909 – 918
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA,Weinheim
www.chemeurj.org
911

V. Percec et al.
Table 2. Thermal transitions [8C] and corresponding enthalpy changes [kcalmolÀ1] for the twin-dendritic compounds.[a]
Compound
First and second heating scans
First cooling scans
3a
S 115 (24.5) i
i 101 (19.0) S
S 113 (18.9) i
3b
3c
3d
3e
3 f
3g
3h
4a
4b
Fr-c 120 (28.4) i
i 67 (11.8) Fr-c
Fr-c 96 (2.0) x 98 (À1.0) x 106 (8.5) i
k 52 (20.5) Fr-s 102 (12.3) i
k 29 (1.8) Fr-s 102 (12.7) i
Fiho 175 (20.6) i
i 64 (9.4) Fr-s 19 (4.0) k
i 156 (0.3) Fiho 149 (15.1) Fiho
i 123 (12.3) Fr-s
Fiho 175 (21.1) i
S(bilayer) 99 (20.5) Fr-c 145 (13.0) i
k 36 (7.4) Fr-c 144 (13.3) i
Fh 105 (2.8) x 120 (7.5) x 137 (7.4) Cub 168 (0.9) i
Fh 131 (32.2) Cub 168 (0.9) i
Fh 95 (34.4) Tet
Fh 84 (5.7) Tet
k 63 (11.1) Cub 130 (0.6) i
Cub 129 (0.6) i
i 166 (0.8) Cub 84 (21.9) Fh
Tet 36 (2.9) Fh
i 124 (0.5) Cub
S 82 (1.6) Fr-s 113 (0.8) x 116 (0.9) x 123 (À7.6) k 131 (8.1) Fr-s 135 (1.0) i
i 128 (0.4) Fr-s
g 36 Fr-s 106 (0.3) Fr-s 116ACHTRENGU(0.8) Fr-s 130ACHTRE(UGN 1.0) i
k 76 (4.5) Fh 101 (3.5) Fh 109 (2.0) Fh 140 (0.3) i
Fh 140 (0.3) i
i 137 (0.3) Fh
4d
4e
4 f
Fiho 157 (12.0) Fiho 206 (0.4) dec
Fh 94 (3.5) Tet 151 (0.3) i
k 59 (3.7) k 110 (19.4) Cub
Cub
i 145 (0.2) Tet
Cub
5b
5d
5 f
k 57 (18.7) Fr-c 73 (À0.3) x 88 (18.2) i
k 38 (À8.7) Fr-c 75 (À2.5) x 88 (15.5) i
k 109 (10.9) i
k 109 (9.6) i
k 90 (22.7) Cub 127 (0.8) i
Cub 128 (0.8) i
i
i 106 (2.7) Fh 73 (5.1) k
i 120 (0.7) Cub
[a] Values were determined by DSC (108CminÀ1). Enthalpy changes [kcalmolÀ1] are given in parentheses. Data from first heating and cooling scans are
on the first line,and data from the second heating scans are on the second line. S: smectic phase; i: isotropic liquid phase; Fr-c : c2mm centered rectangu-
lar columnar lattice; x: unidentified phase; k: crystalline phase; Fr-s : p2mm simple rectangular columnar latice; Fiho: hexagonal columnar lattice with in-
¯
ternal order; S(bilayer): smectic bilayer phase; Fh: p6mm hexagonal columnar lattice; Cub: Pm3n cubic lattice; Tet: P42/mnm tetragonal lattice; g: glass;
dec: sample decomposes.
fringent under polarized light,while the cubic mesophase is
optically isotropic. Very few examples of reversible shape
change have been reported for self-assembling dendrons.[6e]
The reversible shape change reveals new conformations
available to the constituent self-assembling dendrons in 3 f,
3g,and 4e that have been elusive in previous libraries of
self-assembling dendrons.[4–8]
Examination of the self-assembled structure as the core
functionality changes provides further insight into the self-
assembly process. Twin-dendritic compounds 3d, 4d,and 5d
likely due to facile hydrogen bonding which creates a seam
within the columnar object,as has been found for porous
columnar structures formed by dendritic dipeptides.[5] By
contrast, 5d lacks internal order in the Fh phase. If the un-
symmetric urea functionality forms any hydrogen bonds,
they appear unable to form a well-defined arrangement
within the columnar object. The decreased thermodynamic
stability of 5d relative to that of 3d and 4d is further indi-
cated by the fact that 5d forms only a monotropic meso-
phase.
contain
4 f,and 5 f contain AHCTREUNG
A
Twin-dendritic gelators containing
assembling dendrons reveal a different criterion for efficacy
in the gel state. (3,4-3,4)12G2-X dendrons prefer to adopt a
ACHTRE(UNG 3,4-3,4)12G2-X self-
drons (Scheme 1). As noted above,34,-substituted apical
branching units provide highly efficient gelators for organic
solvents. Furthermore, 3d, 3 f, 4d, 4 f, 5d,and 5 f form thixo-
tropic gels in at least one solvent. The incorporation of the
carboxylic acid functionality in 4d and 4 f decreases the pro-
pensity to form thixotropic gels. By contrast,the alkyl urea
functionalized twin-dendritic gelators 5d and 5 f form thixo-
tropic gels at low concentrations in multiple solvents.
ACHTREUNG
conical shape,which self-assembles into spheres. Spherical
assemblies are not expected to gel organic solvents.[1,3] The
¯
phase behavior of 3 f,which exhibits both Fh and Pm3n
phases,reflects quasiequivalence
[14]
of the self-assembling
dendron. It is capable of adopting both flat-taper and coni-
cal shapes. Additionally,we can refer to the observed iso-
tropization temperatures,which reinforce the stability trend
observed for 3d, 4d,and 5d. Gelator 5 f exhibits the small-
est range of temperatures over which the mesophase exists.
The least efficient of these gelators, 4 f,has the most ubiqui-
tous mesophase.
The twin-dendritic gelators containing ACHTREU(NG 4-3,4)12G1-X
self-assembling dendrons self-organize into a hexagonal col-
umnar (Fh) lattice. Gelators 3d and 4d possess internal
order within the columnar lattice (Fiho). The internal order is
912
www.chemeurj.org
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA,Weinheim
Chem. Eur. J. 2008, 14,909 – 918

Twin-Dendritic Organogelators
FULL PAPER
Table 3. Structural and retrostructural analysis of the twin-dendritic libraries.
column. In both 3d and 4d,
the hydrogen bonding of the
amides can occur laterally in
the column.
[a]
Compound
T
[8C]
Phase
a[a,b,d]
a, b[c,f]
a, c[e]
[Š]
d10, d20, d30, d40
m[g]
[b]
d10, d11, d20, d21, d30
d20, d11, d02, d22, d13, d40, d31, d42, d24
d110, d200, d210, d211, d220, d310, d321, d400
[c]
[d]
Figure 2 presents the wide-
angle XRD patterns and plots
of their relative intensities.
Stacking features and features
indicating helical order within
the columns of 3d and 4d are
noted in the figure. Both pat-
terns can be indexed to a 21-
helical packing. Nonetheless,
significantly more order is
found in the columns of 3d
than those of 4d. Figure 3 illus-
trates models constructed to fit
the XRD results for 3d and
4d. The models support the
structural interactions inferred
above. Here we can appreciate
the role of the lateral amide
hydrogen bonds (that is,those
within a column stratum). A
reduction in the number of lat-
eral contacts in bulk correlates
with a higher propensity to
form gels with thixotropic be-
havior. We can reason that the
alkyl urea groups (for example,
in 5d) strain the lateral hydro-
gen bonding within the column
strata while providing some
mechanism for strong associa-
tion along the length of the
column (for example,hydrogen
bonding or van der Waals in-
teractions).
[e]
d002, d410, d330, d202, d212, d411, d312
d10, d11, d02, d12, d20, d21, d40
[Š]
[f]
[a]
3a
3b
3c
3d
25
S
39.5
39.5,19.8
[c]
110
100
25
150
65
95
40
145
35
Fr-c
Fr-s
Fiho
Fiho
S(bilayer)
Fr-c
Fh
84.8,36.5
44.4,73.9
43.4
43.3
69.4
77.9,73.9
52.2
93.9
42.5,33.6,–,–,–,21.2,22.4
44.5,38.3,37.0,28.5,22.2,21.1
37.6,21.7,18.8
37.5,21.5,18.7
69.3,34.6,23.0,17.3
39.0,–,37.3,27.0,23.7,19.5
45.4,26.1,22.6,17.1,15.1
66.4,47.0,41.9,38.3,33.2,29.6,25.1,23.4
[f]
[b]
2.0
[b]
[a]
3e
3 f
3g
[c]
[b]
[d]
[d]
¯
Pm3n
Fh
[b]
49.2
42.7,24.6,21.3
[e]
65
120
20
90
25
P42/mnm
Pm3n
Fr-s
164.9,87.3
80.9
98.5,41.5
45.2
57.2
55.5
43.7,40.0,–,–,37.6,–,33.5
57.2,40.5,36.2,33.0,28.6,25.6,21.6,20.2
¯
3h
4a
4b
4d
[f]
–,38.2,–,–,49.4,24.6
[b]
Fh
Fiho
Fiho
Fh
39.2,22.6,19.6
49.5,28.6,24.7
48.1,27.7,24.0
41.3,23.8,20.6
[b]
3.0
[b]
140
25
[b]
4e
47.6
[e]
140
100
85
100
20
P42/mnm
Pm3n
Fr-c
168.8,88.9
112.9
129.2,69.8
61.2
113.1
102.9
44.5,40.9,39.8,39.3,38.3,37.2,34.2
–,56.5,50.3,45.9
65.2,61.5,–,30.7,–,32.4
52.9,30.6,26.5,20.0
–,56.6,50.5,46.2,–,–,30.3
–,51.4,45.9,42.1,–,–,27.4,25.7
[d]
¯
4 f
5b
5d
5 f
[c]
[b]
Fh
[d]
¯
Pm3n
[d]
¯
110
Pm3n
[a] Lattice parameter a=0.25(d10+2d20+3d30+4d40) and d-spacings in the ratio d10:d20:d30:d40 =1:2:3:4 for the
smectic phases. [b] Lattice parameter a=0.5(d10+30.5 d11+2d20+70.5 d21)3À0.5 and d-spacings in the ratio
d10:d11:d20:d21 =1:30.5:2:70.5 for columnar hexagonal phases. [c] Lattice parameters a and b and d-spacings for
centered rectangular columnar phases. In general, a=d10 and b=d01. The ratio of the d-spacings can be calcu-
lated from the general equation dhk =((haÀ1)2+
A
¯
cubic phases. [e] Lattice parameters a=b,c and d-spacings for the P42/mnm tetragonal phases. The ratio of the
d-spacings can be calculated from the general equation dhkl =((h2+k2)aÀ2 (l2cÀ2))À0.5. [f] Lattice parameters a
and b and d-spacings for the simple rectangular columnar phases. In general a=d10 and b=d01. The ratio of
the d-spacings can be calculated from the general equation dhk =((haÀ1)2+(kbÀ1)2)À0.5. [g] Number of dendrons
+ACHTREUNG
AHCTREUNG
per column stratum=(30.5 NA1)(2M)À1,in which Avogadroꢁs number NA =6.0220455”1023, 1 is the density of
ACHTREUNG
the twin-dendron (assumed to be 1 gcmÀ3),and M is the molecular weight of the compound. [h]Smectic phase
observed only in the as-prepared first heating.
As 5d exhibits only a monotropic mesophase,we were
limited to further structural interrogation of 3d and 4d.
Figure 1 presents plots of the XRD intensity from the Fhio
lattice,relative electron-density plots,and reconstructed
electron-density maps for the two twin-dendritic gelators.
The q11 and q20 reflections of the Fiho lattice (Figure 1a) are
more prominent for 3d than for 4d. We have previously
demonstrated this feature to be indicative of porous colum-
nar structures.[5] The relative electron-density profile and re-
constructed electron-density map (Figure 1b and c) confirm
that the self-organized lattice of 3d is comprised of porous
columns. We infer that hydrogen bonding between the car-
boxylic acid functionalities of 4d within the column interacts
laterally with adjacent twin-dendritic gelators within a
column stratum. Such interactions occur at the core of the
column and prevent a hollow structure from forming (Fig-
ure 1d). On the other hand,hydrogen bonding between the
secondary amines must occur along the length of the
column to create a seam that supports the pore through the
Conclusion
We have demonstrated a novel design for dendritic organo-
gelators. The unique hierarchical assembly of the twin-den-
dritic organogelators promotes the formation of thixotropic
gels. We have subjected these gelators to structural and ret-
rostructural analysis in bulk to correlate with their ability to
gel organic solvents. A diverse set of self-assembled structur-
al motifs and resulting self-organized arrays were obtained
from libraries of twin-dendritic gelators. While extended fi-
brillar structures are implicated in gel formation,gels were
obtained from compounds that self-assemble into lamellar,
columnar,and spherical objects. We attribute this to quasie-
quivalence[14] of the self-assembling dendrons.
The formation of cylindrical objects in bulk and solution
is attributed to lateral hydrogen bonding within the column
strata. Dendrons with 3,4-disubstituted apical branching
Chem. Eur. J. 2008, 14,909 – 918
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA,Weinheim
www.chemeurj.org
913

V. Percec et al.
Figure 1. Comparison of 3d (X=APPDA) and 4d (X=APPDA-Suc):
a) XRD plots of the columnar hexagonal phase; b) relative electron-den-
sity profiles indicating a lower electron-density region at the center of
the self-assembled supramolecular columns with X=APPDA; recon-
structed electron-density maps for c) 3d (X=APPDA) and d) 4d (X=
APPDA-Suc) suggesting a different packing at the apex region of the
two dendrons.
Figure 2. a) Wide-angle XRD results from oriented fiber patterns collect-
ed at 258C and indexed to a 21-helical packing; b) the corresponding
meridional q plots. s: 4.4 Š stacking feature (also the maxima of the
second helical layer line); h1, h1’,and h1’’: various maxima observed on
the first helical layer line; h2: helical features observed for 3d; L: helical
layer line order (position indicated by the dotted horizontal lines).
Figure 3. a) Top (a,e) and side (b) views of the molecular model constructed for 3d. Top (c,f) and side (d) views of the molecular model constructed for
4d. The models both show the lateral hydrogen bonds with a column stratum and the helical arrangement of the dendrons.
914
www.chemeurj.org
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA,Weinheim
Chem. Eur. J. 2008, 14,909 – 918

Twin-Dendritic Organogelators
FULL PAPER
Synthesis of 4-(4,6-dimethoxy-1,3,5-triazine-2-yl)-4-methyl-morpholinium
chloride (DMT-NMM+ClÀ): CDMT (1.58 g,9 mmol) was dissolved in
THF (30 mL). NMM (0.9 mL ,9 mmol) was added dropwise to the solu-
tion,thereby generating a thick white slurry. The reaction mixture was
stirred for 30 min at 238C,after which the white solid was filtered off and
washed with THF several times to provide a colorless solid (97% yield).
M.p. 116–1178C (literature value:[10c 116–1178C).]
units exhibit the greatest propensity to form gels and to
impart thixotropic behavior to the gel. Thixotropic gels
appear to result from twin-dendritic gelators that have com-
paratively weak lateral interactions in bulk. One strategy to
prepare thixotropic gels is to employ gelators that form
porous columnar mesophases in bulk. The seam of hydrogen
bonds that reinforce the pore wall in bulk appears to play a
critical role in the emergence of gel properties. These design
principles expand upon those of earlier dendritic organoge-
lators[13] and compliment the growing understanding of thix-
otropic organogels.[3]
Synthesis of the 4,6-dimethoxy-1,3,5-triazine (DMT) ester of carboxylic
acid 1a: DMT-NMM+ClÀ (8.28 g,30 mmol) was dissolved in anhydrous
THF (30 mL) that had been previously chilled in an ice-bath. A solution
of acid 1a (3 g,10 mmol) and NMM (2 mL,20 mmol) in anhydrous THF
(5 mL) were added dropwise to this mixture. After 2 h,the reaction was
diluted with dichloromethane (50 mL) and poured into cold water (108C;
50 mL). The reaction was then partitioned between the organic and aque-
ous phases. The water layer was washed three times with small amounts
of CH2Cl2. All of the organic extracts were combined and washed with
1n HCl (50 mL),sat. NaHCO (50 mL),water (50 mL),brine (50 mL),
3
Experimental Section
and water (50 mL) again. All aqueous solutions were previously chilled
in a refrigerator (108C). The organic phase was dried over anhydrous
MgSO4. The solvent was evaporated under vacuum at room temperature.
The resulting colorless solid was purified by flash chromatography on a
silica-gel column,with CH 2Cl2 employed as the eluting solvent. 1H NMR
(CDCl3,TMS): d=8.10 (d,2H),6.93 (d,2H),4.14–4.00 (overlapped
peaks,m,8H),1.81 (m,2H),1.43 (m,2H),1.22 (m,18H),0.88 ppm (t,
3H); 13C NMR (CDCl3,TMS): d=174.57,171.47,164.69,162.57,133.37,
120.36,114.53,68.81,56.22,32.30,30.03,30.02,29.96,29.93,29.73,29.44,
26.35,23.07,14.49 ppm; MALDI-TOF MS: m/z: 484.97 [M+K+],469.04
[M+Na+].
Materials: 1, 1’-Carbonyldiimidazole (CDI; Acros,97%) was used as re-
ceived. Its purity was assessed by a melting-point measurement and
1H NMR spectroscopy. Succinic anhydride (Aldrich,99 + %) was used as
received. N-(3-aminopropyl)-1,3-propanediamine (APPDA) was also pur-
chased from Aldrich (99+ %) and used as received. THF was refluxed
over sodium ketyl until the solution turned purple and was then distilled
before use. CH2Cl2 was freshly distilled from CaH2. 2-Amino-6-methyl-
heptane (Acros,99%) was used as received.
N-methylmorpholine
(NMM; Aldrich,99%) was used without purification. 2-chloro-46, -dime-
thoxy-1,3,5-triazine (CDMT) was prepared according to the procedure
reported previously.[10c]
Acylation of N-(3-aminopropyl)-1,3-propanediamine (APPDA) by the
DMT ester of 1a: An excess of the DMT ester of acid 1a (2.32 g,
4.8 mmol) was added to a solution of APPDA (0.17 mL,1.18 mmol) in
THF (25 mL). The solution was stirred at 238C under an argon atmos-
phere for 2 h. A precipitate formed upon completion of the reaction. The
reaction mixture was taken into methanol and filtered. The resulting
solid was recrystallized from acetone to afford the triacylated product as
a colorless solid (1.11 g,95% yield). The resulting compound was found
to have very low solubility in all solvents that were tried; therefore,a sat-
isfactory 13C NMR spectrum could not be obtained. 1H NMR (CDCl3,
TMS): d=7.86 (m,2H),7.67 (m,1H),7.52 (m,2H),7.32 (d,2H),6.88–
6.83 (overlapped peaks,m,6H),5.91 (m,1H),3.98 (t,4H),3.83 (t,2H),
3.66 (m,2H),3.45 (m,4H),3.31 (m,2H),1.88 (m,4H),1.76 (m,6H),
Techniques: All 1H and 13C NMR spectra were recorded on Bruker
DRX-500 (500 MHz) machine at 208C with CDCl3 as the solvent (with
tetramethylsilane (TMS) as an internal standard). DSC was performed
on a Differential Scanning Calorimeter 2920 (TA Instruments) at rates of
58CminÀ1. A polarized optical microscope (Olympus BX-60) equipped
with a Mettler FP 82 hot stage was used to investigate the bulk properties
of the synthesized compounds. All MALDI-TOF spectra were recorded
on a Voyager-DE mass spectrometer (Perceptive Biosystems) with dihy-
droxybenzoic acid (Aldrich,97%; recrystallized from water before use)
as a matrix. The purity of products was determined by a combination of
techniques including TLC on silica gel plates (Kodak) with fluorescent
indicator and HPLC on a Perkin–Elmer Series 10 high-pressure liquid
chromatograph equipped with an LC-100 column oven,Nelson Analyti-
cal 900 Series integrator data station,and two Perkin–Elmer PL gel col-
umns. Melting points were measured by using a Unimelt capillary melt-
ing-point apparatus (Arthur H. Thomas Company,Philadelphia,USA).
XRD measurements were performed by using CuKa1 radiation (l=
1.54178 Š) from a Bruker–Nonius FR-591 rotating anode X-ray source
equipped with a 0.2”0.2 mm2 filament operated at 3.4 kW. The Cu radia-
tion beam was collimated and focused by a single bent mirror and sagital-
1.44 (m,6H),1.27 (m,48H),0.88 ppm (t,9H); MALDI-TOF MS:
m/z:
1035.98 [M+K+],1018.95 [ M+Na+],997.03 [ M+2H+].
Typical procedure of imidazolide synthesis: Synthesis of 4-(dodecan-1-
yloxy)benzoyl imidazole (2a): CDI (1.459 g,9.0 mmol) was placed into a
round-bottomed flask under argon. Acid 1a (0.918 g,3 mmol) was dis-
solved in anhydrous dichloromethane (50 mL) and added to the flask by
syringe. The reaction was stirred at room temperature for 1 h while argon
was bubbled through. The progress of the reaction was monitored by
TLC,MALDI mass spectrometry,and 1H NMR spectroscopy. Upon com-
pletion of the reaction,the reaction mixture was cooled in a refrigerator,
washed 4–5 times with cold water (58C),and dried over anhydrous
MgSO4. The solvent was evaporated under reduced pressure and the
product was recrystallized from acetone to afford a colorless powder
(1.003 g,95% yield). M.p. 67–69 8C; 1H NMR (CDCl3,TMS): d=8.02 (s,
1H),7.73 (d,2H),7.47 (s,1H),7.09 (s,1H),6.95 (d,2H),3.98 (t,2H),
ly focused through a SiACHTREUNG(111) monochromator,thereby generating a 0.3”
0.4 mm2 spot on a Bruker-AXS Hi-Star multiwire area detector. To mini-
mize attenuation and background scattering,an integral vacuum was
maintained along the length of the flight tube and within the sample
chamber. Samples were held in quartz capillaries (0.7–1.0 mm in diame-
ter) mounted in a temperature-controlled oven (temperature precision:
Æ0.18C; temperature range: À120 to 2708C). The distance between the
sample and the detector was 12.0 cm for wide-angle diffraction experi-
ments and 54.0 cm for intermediate-angle diffraction experiments.
Aligned samples for fiber XRD experiments were prepared by using a
custom-made extrusion device. Thus,powdered sample ( ꢀ10 mg) was
heated inside the extrusion device above the melting temperature. The
fiber was extruded in the mesophase and cooled to 238C. Typically,the
aligned samples have a thickness of ꢀ0.3–0.7 mm and a length of ꢀ3–
7 mm. All XRD measurements were done with the aligned sample axis
perpendicular to the beam direction. The XRD peak position and inten-
sity analysis was performed with Datasqueeze Software (version 2.01)
that allows background elimination and Gaussian,Lorentzian,Lorent-
zian-squared,or Voigt peak-shape fitting.
1.73 (m,2H),1.40 (m,2H),1.19 (m,16H),0.81 ppm (t,3H);
13C NMR
(CDCl3,TMS): d=165.86,164.12,138.54,132.78,131.03,123.98,118.64,
115.14,68.95,32.31,30.05,30.03,29.98,29.95,29.73,29.43,26.36,23.08,
14.51 ppm.
3,4-Bis(dodecan-1-yloxy)benzoyl imidazole (2b): A synthetic procedure
analogous to the synthesis of 2a was used. Aqueous workup and recrys-
tallization from acetone afforded 2b as a colorless solid (88% yield).
M.p. 72–748C; 1H NMR (CDCl3,TMS): d=8.09 (s,1H),7.54 (s,1H),
7.36 (d,1H),7.34 (s,1H),7.15 (s,1H),6.94 (d,1H),4.09 (t,2H),4.04 (t,
2H),1.85 (m,4H),1.48 (m,4H),1.36–1.27 (overlapped peaks,m,32H),
0.88 ppm (t,6H); 13C NMR (CDCl3,TMS): d=165.94,154.55,149.63,
138.63,130.99,124.83,124.04,118.72,115.13,112.35,69.90,69.64,32.32,
Chem. Eur. J. 2008, 14,909 – 918
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA,Weinheim
www.chemeurj.org
915

V. Percec et al.
30.08,30.05,30.00,29.77,29.75,29.53,29.41,26.39,26.36,23.08,
14.49 ppm; MALDI-TOF MS: m/z: 580.44 [M+K+],564.23 [ M+Na+],
541.82 [M+H+].
(s,1H),7.40 (overlapped peaks,m,3H),7.13 (s,1H),7.02 (d,1H),6.62
(d,4H),5.15 (s,2H),5.09 (s,2H),3.92 (overlapped peaks,m,12H),1.75
(m,12H),1.45 (m,12H),1.26 (m,96H),0.87 ppm (t,18H);
13C NMR
(CDCl3,TMS): d=165.68,154.22,153.85,153.81,149.11,138.62,138.51,
131.58,131.39,131.05,125.30,124.61,118.76,116.55,113.80,106.23,
106.15,73.85,72.07,71.82,69.63,69.56,32.34,30.80,30.18,30.14,30.09,
30.06,29.90,29.85,29.81,29.79,26.57,23.10,14.52 ppm; MALDI-TOF
MS: m/z: 1531.5 [M+K+],1516.2 [ M+Na+],1492.4 [ M+2H+].
3,4,5-Tris(dodecan-1-yloxy)benzoyl imidazole (2c): A synthetic procedure
analogous to the synthesis of 2a was used. Aqueous workup and recrys-
tallization from acetone afforded the corresponding imidazolide as a col-
orless powder (92% yield). M.p. 61–628C; 1H NMR (CDCl3,TMS): d=
8.10 (s,1H),74, 6 (s,1H),7.16 (s,1H),6.98 (s,2H),4.07 (t,2H),3.99 (t,
4H),1.80 (overlapped peaks,m,6H),1.46 (m,6H),1.26 (m,48H),
0.88 ppm (t,9H); 13C NMR (CDCl3,TMS): d=166.16,153.66,143.63,
138.67,131.16,126.47,118.66,109.10,74.14,69.92,32.33,32.32,30.76,
30.14,30.12,30.09,30.05,30.01,29.95,29.76,29.67,26.45,23.08,
Typical procedure for coupling of imidazolides with APPDA: Synthesis
of
N,N-bis(3-(4-(dodecan-1-yloxy)benzamido)propyl)amine
(3a):
APPDA (0.7 mL,5 mmol) was placed into a round-bottomed flask under
argon. 2a (3.52 g,10 mmol) dissolved in anhydrous THF was added to
the flask gradually over a period of 20 min. The reaction was kept under
argon and the mixture was stirred in an ice-bath at 08C for 4 h. Upon
completion of the reaction,the mixture was poured into methanol; this
resulted in a white precipitate,which was filtered off,washed repeatedly
with water,recrystallized from acetone and/or ethyl acetate,and dried
under vacuum to provide a colorless solid (3.31 g,93% yield). 1H NMR
(CDCl3,TMS): d=7.74 (d,4H),7.19 (t,2H),6.89 (d,4H),3.98 (t,4H),
3.59 (q,4H),2.74 (t,4H),1.70 (m,9H),1.43 (m,4H),1.19 (m,32H),
0.81 ppm (t,6H); 13C NMR (CDCl3,TMS): d=167.63,162.08,129.07,
127.13,114.57,68.58,48.23,39.09,32.32,30.07,30.04,30.01,29.98,29.81,
14.49 ppm; MALDI-TOF MS: m/z: 764.22 [M+K+],748.61 [ M+Na+],
726.44 [M+H+].
3,4-Bis[(4’-dodecan-1-yloxy)benzyloxy]benzoyl imidazole (2d):
A syn-
thetic procedure analogous to the synthesis of 2a was used. Aqueous
workup and recrystallization from acetone afforded the corresponding
imidazolide as a colorless powder (90% yield). M.p. 93–958C; 1H NMR
(CDCl3,TMS): d=7.96 (s,1H),7.27 (overlapped peaks,m,7H),7.05 (s,
1H),6.94 (d,1H),6.82 (overlapped peaks,m,4H),5.11 (s,2H),5.05 (s,
2H),3.88 (t,4H),1.70 (m,4H),1.37 (m,4H),1.19 (m,32H),0.81 ppm
(t,6H); 13C NMR (CDCl3,TMS): d=165.76,159.63,154.39,149.07,
138.54,130.97,129.51,129.33,128.49,128.23,125.24,124.39,118.71,
116.87,115.07,115.04,113.84,71.64,71.30,68.50,32.32,30.07,30.04,
30.01,29.99,29.82,29.75,29.68,26.47,23.09,14.52 ppm; MALDI-TOF
MS: m/z: 792.27 [M+K+],776.25 [ M+Na+],754.22 [ M+H+].
29.75,29.58,26.42,23.09,14.51 ppm; MS (ESI):
N,N-Bis(3-(3,4-bis(dodecan-1-yloxy)benzamido)propyl)amine (3b):
m/z: 708.32 [M+H+].
N
A
synthetic procedure analogous to the synthesis of 3a was used. Upon
completion of the reaction,the mixture was poured into methanol and
filtered. The product was recrystallized from acetone to yield a colorless
powder (89% yield). 1H NMR (CDCl3,TMS): d=7.43 (s,2H),7.25–7.24
(overlapped peaks,m,4H),6.82 (d,4H),4.01 (t,8H),3.56 (q,4H),2.77
(t,4H),1.82 (m,12H),1.48 (m,8H),1.35 (m,64H),0.91 ppm (t,12H);
13C NMR (CDCl3,TMS): d=167.72,152.33,149.35,127.59,119.97,
113.52,112.77,69.86,69.55,48.20,39.14,32.33,30.11,30.06,30.05,29.85,
3,4,5-Tris[(4’-dodecan-1-yloxy)benzyloxy]benzoyl imidazole (2e): A syn-
thetic procedure analogous to the synthesis of 2a was used. In this case,
an excess of CDI (3.0 equiv) was necessary to convert all of the acid into
imidazolide. Aqueous workup afforded the corresponding imidazolide as
a colorless powder (90% yield). M.p. 78–798C; 1H NMR (CDCl3,TMS):
d=8.00 (s,1H),7.28 (overlapped peaks,d,7H),7.10 (s,1H),7.03 (s,
2H),6.81 (d,4H),6.76 (d,2H),5.08 (s,2H),5.05 (s,4H),3.92 (m,6H),
29.77,29.70,29.62,29.572, 6.43,23.08,14.49 ppm; MALDI-TOF MS:
m/z:
1118.51 [M+2H++K+],1102.23 [ M+2H++Na+],1078.94 [ M+2H+].
1.78 (m,6H),1.45 (m,6H),1.26 (m,48H),0.87 ppm (t,9H);
13C NMR
(CDCl3,TMS): d=165.892,159.65,159.59,153.23,143.80,138.51,131.10,
130.70,129.64,129.52,128.38,126.55,118.70,115.04,114.62,110.61,75.30,
71.72,68.52,68.44,32.34,30.09,30.06,30.03,30.01,29.87,29.77,29.73,
29.70,26.49,23.11,14.53 ppm; MALDI-TOF MS: m/z: 1087.93 [M+K+],
1066.84 [M+Na+],1044.83 [ M+H+].
N,N-Bis(3-(3,4,5-tris(dodecan-1-yloxy)benzamido)propyl)amine (3c):
A
synthetic procedure analogous to the synthesis of 3a was used. After 4 h
of stirring under argon,the reaction mixture was poured into methanol
and filtered. The solid was recrystallized twice from acetone to afford a
pure colorless solid (89% yield). 1H NMR (CDCl3,TMS): d=7.13 (t,
2H),6.97 (s,4H),3.95 (t,12H),3.52 (q,4H),2.73 (t,4H),1.77–1.71
(overlapped peaks,m,16H),1.43 (m,12H),1.26 (m,96H),0.88 ppm (t,
18H); 13C NMR (CDCl3,TMS): d=167.87,153.46,141.70,129.98,106.41,
73.90,69.88,48.09,39.18,32.33,30.76,30.16,30.12,30.10,30.07,30.02,
29.85,29.79,29.77,29.63,26.52,23.09,14.49 ppm; MALDI-TOF MS:
m/z: 1485.74 [M+K+],1470.23 [ M+Na+],1446.67 [ M+H+].
3,4-Bis(3’,4’-bis(dodecan-1-yloxy)benzyloxy)benzoyl imidazole (2 f):
A
synthetic procedure analogous to the synthesis of 2a was used. Aqueous
workup and recrystallization from acetone afforded 2 f as a colorless
solid (91% yield). M.p. 95–978C; 1H NMR (CDCl3,TMS): d=8.04 (s,
1H),7.40 (overlapped peaks,m,3H),7.12 (s,1H),6.98 (d,1H),6.96 (d,
2H),6.93–6.90 (overlapped peaks,m,2H),6.84 (overlapped peaks,m,
2H),5.16 (s,2H),5.11 (s,2H),3.96 (overlapped peaks,m,8H),1.81 (m,
N,N-Bis(3-ACHTRE(UGN 3,4-bis[(4’-dodecan-1-yloxy)benzyloxy]benzamido)propyl)-
8H),1.45 (m,8H),1.26 (m,64H),0.87 ppm (t,12H);
13C NMR (CDCl3,
amine (3d): When an analogous procedure to that described above was
used in dichloromethane or THF,the reaction mixture resulted in a gel.
The gel/precipitate was filtered to afford fibrous colorless waxy solid
(85% yield). The product obtained by this method is usually pure; how-
ever,additional recrystallization from a dichloromethane/EtOAc mixture
was sometimes used. 1H NMR (CDCl3,TMS): d=7.47 (d,2H),7.28
(overlapped peaks,m,12H),6.82 (overlapped peaks,m,8H),5.10 (s,
4H),5.01 (s,4H),3.90 (t,8H),3.50 (q,4H),2.75 (t,4H),1.75 (m,13H),
TMS): d=165.74,154.308,149.80,149.79,149.66,149.58,149.07,138.53,
131.00,129.18,128.94,125.23,124.44,120.63,120.46,118.71,116.65,
114.09,113.76,113.69,113.60,71.77,71.49,69.74,69.76,32.34,30.14,
30.12,30.08,30.06,29.91,29.87,29.78,29.74,26.51,26.48,23.10,
14.52 ppm; MALDI-TOF MS: m/z: 1161.7 [M+K+],1145.2 [ M+Na+],
1123.4 [M+2H+].
3,5-Bis(3’,4’-bis(dodecan-1-yloxy)benzyloxy)benzoyl imidazole (2g):
A
1.41 (m,8H),1.26 (m,64H),0.87 ppm (t,12H);
13C NMR (CDCl3,
synthetic procedure analogous to the synthesis of 2a was used. Aqueous
workup and recrystallization from acetone afforded 2g as a colorless
solid (82% yield). M.p. 72–738C; 1H NMR (CDCl3,TMS): d=8.08 (s,
1H),7.45 (s,1H),7.13 (s,1H),6.97–6.86 (overlapped peaks,m,9H),4.97
(s,4H),3.99 (m,8H),1.81 (m,8H),1.45 (m,8H),1.26 (m,64H),
TMS): d=167.45,167.12,159.34,152.23,149.18,129.62,129.54,129.34,
129.24,129.15,128.98,128.82,127.68,127.45,120.88,114.84,114.84,
114.62,114.21,71.54,71.23,68.49,48.15,39.34,32.31,30.10,30.07,29.83,
29.73,29.71,29.43,28.24,27.75,26.48,23.08,14.52 ppm; MALDI-TOF
MS: m/z: 1543.54 [M+3H++K+],1522.71 [ M+Na+],1501.52 [ M+].
0.87 ppm (t,12H); 13C NMR (CDCl3,TMS): d=160.52,149.86,149.80,
138.60,1338,9,131.30,128.80,120.99,118.45,114.20,114.03,109.11,
107.82,71.05,69.78,32.34,30.11,30.07,30.05,29.86,29.84,29.77,29.74,
N,N-Bis(3-(3,4,5-tris[(4’-dodecan-1-yloxy)benzyloxy]benzamido)propyl)-
amine (3e): A synthetic procedure analogous to the synthesis of 3a was
used. The reaction was left to stir under argon for 2 h. The reaction mix-
ture was then poured into methanol and the precipitate was filtered off.
Recrystallization from BuOAc (or alternatively column chromatography
on silica gel,with first a dichloromethane/EtOAC mixture and then a
CHCl3/MeOH mixture employed as the eluting solvent,with subsequent
evaporation of the solvent) afforded a colorless solid (1.04 g,81% yield).
29.70,26.47,26.46,23.10,14.51 ppm; MALDI-TOF MS:
m/z: 1126.47
[M+5H+].
3,4-Bis(3’,4’,5’-tris(dodecan-1-yloxy)benzyloxy)benzoyl imidazole (2h): A
synthetic procedure analogous to the synthesis of 2a was used. Aqueous
workup and recrystallization from acetone afforded 2h as a waxy color-
less solid (83% yield). M.p. 64–668C; 1H NMR (CDCl3,TMS): d=8.07
916
www.chemeurj.org
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA,Weinheim
Chem. Eur. J. 2008, 14,909 – 918

Twin-Dendritic Organogelators
FULL PAPER
1H NMR (CDCl3,TMS): d=7.27 (d,8H),7.20 (d,4H),6.84 (d,8H),6.70
(d,4H),4.92 (s,4H),4.89 (s,8H),3.89 (m,12H),3.50 (q,4H),2.74 (t,
4H),1.84 (m,17H),1.44 (m,12H),1.26 (m,96H),0.83 ppm (t,18H);
13C NMR (CDCl3,TMS): d=167.66,159.44,159.36,153.24,141.90,
130.59,130.31,129.93,129.71,129.02,114.82,114.50,107.76,75.17,71.79,
68.47,68.38,48.20,39.24,32.34,30.10,30.06,30.03,29.89,29.77,29.74,
29.57,26.50,23.10,14.52 ppm; MALDI-TOF MS: m/z: 2123.92 [M+3H+
+K+],2107.79 [ M+3H++Na+],2085.60 [ M+3H+].
used,to afford a colorless powder (92% yield). 1H NMR (CDCl3,TMS):
d=7.78 (overlapped peaks,d,4H),7.55 (t,1H),6.95 (t,1H),6.86 (dd,
4H),3.96 (t,4H),3.47 (m,4H),3.38 (t,2H),3.31 (q,4H),2.67–2.58 (m,
4H),1.96 (m,2H),1.78–1.75 (two overlapped peaks,m,6H),1.43 (m,
4H),1.26 (m,32H),0.87 ppm (t,6H);
13C NMR (CDCl3,TMS): d=
176.75,173.27,168.03,167.50,162.29,162.17,129.26,126.65,126.49,
114.62,68.62,46.22,43.17,37.87,36.19,32.32,30.07,30.04,30.02,29.99,
29.82,29.75,29.59,28.13,27.88,26.42,23.09,14.51 ppm; MS (ESI):
808.43 [M+H+].
m/z:
N,N-Bis(3-ACHTREUNG(3,4-bis(3’,4’-bis(dodecan-1-yloxy)benzyloxy)benzamido)pro-
pyl)amine (3 f): A synthetic procedure analogous to the synthesis of 3a
was used. Upon completion,the reaction mixture was poured into metha-
nol and filtered. The resulting product was recrystallized from acetone
several times. A colorless solid was obtained (92% yield). 1H NMR
(CDCl3,TMS): d=7.50 (s,2H),7.22 (m,2H),6.95 (d,4H),6.87 (over-
lapped peaks,m,6H),6.79 (d,4H),5.01 (s,8H),3.94 (t,8H),3.88 (t,
8H),3.49 (q,4H),2.72 (t,4H),1.76 (m,20H),1.44 (m,16H),1.26 (m,
128H),0.87 ppm (t,24H); 13C NMR (CDCl3,TMS): d=167.42,152.16,
149.75,149.71,149.44,149.42,149.21,129.36,129.95,129.72,128.27,
120.72,120.61,120.49,114.86,114.22,114.14,113.96,113.73,71.91,71.48,
69.79,69.66,69.65,48.30,39.27,32.35,30.11,30.09,29.95,29.81,29.58,
26.55,26.51,23.10,14.50 ppm; MALDI-TOF MS: m/z: 2275.51 [M+K+],
2260.23 [M+Na+],2237.94 [ M+].
N,N-Bis(3-ACHTRE(GNU 3,4-bis(dodecan-1-yloxy)benzamido)propyl)amino-4-oxo-buta-
noic acid (4b): A synthetic procedure analogous to the synthesis of 4d
was used,to afford a colorless powder in 93% yield. 1H NMR (CDCl3,
TMS): d=8.06 (t,1H),7.46 (d,2H),7.38 (m,2H),7.28 (t,1H),6.81
(overlapped peaks,m,2H),3.99 (overlapped peaks,m,8H),3.45 (m,
4H),3.32 (m,2H),3.29 (m,2H),2.60 (m,2H),2.57 (m,2H),1.95 (m,
2H),1.81 (m,8H),1.69 (m,2H),1.43 (m,8H),1.26 (m,64H),0.87 ppm
(t,12H); 13C NMR (CDCl3,TMS): d=173.19,168.03,167.48,152.40,
152.19,149.28,149.17,126.99,126.82,120.39,120.25,113.15,112.82,
112.73,112.55,69.70,69.50,46.22,43.06,37.94,35.99,32.35,30.09. 29.88,
29.80,29.67,29.58,28.15,27.80,26.45,23.12,14.54 ppm; MALDI-TOF
MS: m/z: 1203.43 [M+3H++Na+],1180.13 [ M+3H+].
N,N-Bis(3-(3,4,5-tris[(4’-dodecan-1-yloxy)benzyloxy]benzamido)propyl)-
amino-4-oxo-butanoic acid (4e): A synthetic procedure analogous to the
synthesis of 4d was used and resulted in a white solid as the final product
N,N-Bis(3-ACHTREUNG(3,5-bis(3’,4’-bis(dodecan-1-yloxy)benzyloxy)benzamido)pro-
pyl)amine (3g): A synthetic procedure analogous to the synthesis of 3a
was used. Upon completion,the reaction mixture was poured into metha-
nol and filtered. The resulting product was purified by column chroma-
tography as described for 3c. A colorless solid was obtained (78% yield).
1H NMR (CDCl3,TMS): d=7.48 (s,2H),7.02–6.81 (overlapped peaks,
m,7H),6.66 (s,2H),4.87 (s,8H),3.95 (t,16H),3.46 (q,4H),2.76 (t,
4H),1.81 (m,16H),1.45 (m,16H),1.26 (m,128H),0.87 ppm (t,24H);
13C NMR (CDCl3,TMS): d=167.72,160.42,149.75,149.64,137.16,
129.36,125.92,121.08,114.96,106.48,105.31,70.81,69.77,48.15,39.17,
32.35,30.73,30.13,30.08,29.90,29.89,29.79,29.75,26.51,26.48,23.11,
14.52 ppm; MALDI-TOF MS: m/z: 2277.35 [M+K+],2261.79 [ M+Na+],
2241.56 [M+3H+].
1
(87% yield). H NMR (CDCl3,TMS): d=7.28 (d,8H),7.20 (d,4H),6.82
(d,8H),6.70 (d,4H),4.92 (s,4H),4.89 (s,8H),3.87 (m,12H),3.45 (m,
4H),3.32 (m,84H),2.57 (m,2H),2.53 (m,2H),1.92 (m,2H),1.76 (m,
12H),1.72 (m,2H),1.43 (m,12H),1.26 (m,96H),0.87 ppm (t,18H);
13C NMR (CDCl3,TMS): d=177.58,173.25,167.77,167.18,159.43,
159.36,159.32,153.29,153.24,141.77,141.41,130.55,130.09,129.98,
129.75,129.66,129.51,129.18,129.03,114.82,114.78,114.49,107.48,
106.81,75.17,71.50,71.20,68.48,68.45,68.39,46.44 ppm; MALDI-TOF
MS: m/z: 2224.43 [M+3H++Na+].
N,N-Bis(3-ACHTRE(UGN 3,4-bis(3’,4’-bis(dodecan-1-yloxy)benzyloxy)benzamido)propyl)-
amino-4-oxo-butanoic acid (4 f): A synthetic procedure analogous to the
synthesis of 4d was used,to afford a colorless powder (91% yield).
1H NMR (CDCl3,TMS): d=7.60–7.59 (overlapped peaks,m,3H),7.41
(m,1H),7.00–6.79 (overlapped peaks,m,16H),5.05 (s,4H),5.04 (s,
4H),3.94 (t,8H),3.88 (t,8H),3.48 (m,2H),3.45 (m,2H),3.38 (m,2H),
3.32 (m,2H),2.67 (m,2H),2.63 (m,2H),1.94 (m,2H),1.76 (m,18H),
N,N-Bis(3-ACHTREUNG(3,4-Bis(3’,4’,5’-tris(dodecan-1-yloxy)benzyloxy)benzamido)-
propyl)amine (3h): A synthetic procedure analogous to the synthesis of
3a was used. Upon completion,the reaction mixture was poured into
methanol and filtered. The resulting product was purified by column
chromatography as described for 3c. A colorless solid was obtained
1
(75% yield). H NMR (CDCl3,TMS): d=7.53 (s,2H),7.31 (d,4H),6.88
1.43 (m,16H),1.26 (m,128H),0.88 ppm (t,24H);
13C NMR (CDCl3,
(d,1H),6.59 (d,8H),5.02 (s,8H),3.92–3.86 (overlapped peaks,m,
24H),3.49 (q,4H),2.76 (t,4H),1.74 (m,28H),1.45 (m,24H),1.26 (m,
192H),0.87 ppm (t,36H); 13C NMR (CDCl3,TMS): d=167.68,153.72,
153.66,152.19,138.35,132.27,132.07,128.09,120.80,114.82,114.31,
106.39,106.12,73.82,72.17,71.80,69.54,47.66,38.68,32.35,30.83,30.19,
30.16,30.11,29.94,29.91,29.80,28.99,26.60,23.10,14.49 ppm; MALDI-
TOF MS: m/z: 3008.8 [M+K+],2992.3 [ M+Na+],2971.0 [ M+].
TMS): d=167.70,167.21,152.32,152.11,149.71,149.45,149.40,149.34,
149.25,149.15,129.92,129.62,127.77,127.49,120.75,120.65,120.52,
114.50,114.10,113.91,113.74,71.53,71.42,69.77,69.63,46.12,43.10,
37.98,36.29,32.35,30.11,29.98,29.95,29.84,29.80,29.50,27.87,26.58,
26.53,23.09,14.49 ppm; MALDI-TOF MS:
m/z: 2375.40 [M+K+],
2359.54 [M+Na+]
Typical procedure for the synthesis of ureas: Synthesis of 1,1-bis(3-ACHTREUNG(3,4-
Typical procedure for coupling of amido amines with succinic anhydride:
Synthesis of N,N-bis(3-ACHTREU(NG 3,4-bis[(4’-dodecan-1-yloxy)benzyloxy]benzami-
bis[(4’-dodecan-1-yloxy)benzyloxy]benzamido)propyl)-3-(6-methylhep-
tan-2-yl)urea (5d): CDI (0.13 g,0.79 mmol) was dissolved in anhydrous
THF (25 mL). 2-Amino-6-methylheptane (0.13 mL,0.79 mmol) was
added to that mixture dropwise. The reaction was left to stir for 1 h at
238C. Upon completion of this step (as monitored by TLC),compound
3d (0.79 g,0.53 mmol) was added to the mixture; the mixture was then
refluxed for 6 h. The solvent was evaporated and the resulting solid was
recrystallized twice from acetone to afford a colorless solid (87% yield).
1H NMR (CDCl3,TMS): d=7.58 (s,2H),7.36–7.30 (overlapped peaks,
m,12H),6.90 (d,2H),6.85 (d,8H),5.09 (s,4H),5.08 (s,4H),4.80 (d,
1H),3.94 (t,8H),3.89 (m,1H),3.41 (m,4H),3.34 (m,4H),1.77 (m,
12H),1.43 (m,10H),1.29–1.26 (overlapped peaks,m,67H),1.10 (m,
do)propyl)amino-4-oxo-butanoic acid (4d): Amido amine 3d (1.502 g,
1 mmol) was mixed with succinic anhydride (0.110 g,1.1 mmol). The mix-
ture was dissolved in hot anhydrous THF and refluxed overnight under
argon. The mixture was then poured into water; this resulted in a white
precipitate,which was filtered,washed with water,and recrystallized
from acetone. This procedure provided a colorless solid product (1.329 g,
83% yield). 1H NMR (CDCl3,TMS): d=7.57 (d,2H),7.32 (overlapped
peaks,m,12H),6.80 (overlapped peaks,m,8H),4.99 (m,8H),3.87 (t,
8H),3.38 (m,4H),3.28 (m,4H),2.60 (m,2H),2.53 (m,4H),1.84 (m,
2H),1.65 (m,10H),1.43 (m,8H),1.26 (m,64H),0.87 ppm (t,12H);
13C NMR (CDCl3,TMS): d=177.58,173.25,167.80,167.23,159.37,
152.31,152.07,149.24,149.12,129.66,129.58,129.38,129.23,129.13,
5H),0.87 (t,12H),0.79 ppm (d,6H);
13C NMR (CDCl3,TMS): d=
167.43,159.40,158.60,152.16,149.30,129.61,129.31,129.25,129.02,
127.84,120.66,114.92,114.87,114.50,71.51,71.37,68.48,47.13,44.35,
39.23,38.07,37.12,32.32,30.07,30.01,29.83,29.75,29.72,28.92,28.27,
26.48,24.43,23.09,22.94,22.00,14.50 ppm; MALDI-TOF MS:
1697.10 [M+H++K+],1680.53 [ M+H++Na+],1657.78 [ M+H+].
128.96,128.86,127.67,127.48,120.86,114.86,114.81,114.60,114.0,71.56,
71.28,68.47,46.17,43.00,37.99,36.10,32.33,30.09,30.05,29.86,29.76,
29.73,29.43,28.24,27.78,26.48,23.09,14.52 ppm; MALDI-TOF MS:
m/z:
m/z:
1643.20 [M+3H++K+],1627.27 [ M+3H++Na+],1604.99 [ M+3H+].
N,N-Bis(3-(4-(dodecan-1-yloxy)benzamido)propyl)amino-4-oxo-butanoic
acid (4a): A synthetic procedure analogous to the synthesis of 4d was
1,1-Bis(3-
ACHTRE(UNG 3,4-bis(dodecan-1-yloxy)benzamido)propyl)-3-(6-methylhep-
tan-2-yl)urea (5b): A synthetic procedure analogous to the synthesis of
Chem. Eur. J. 2008, 14,909 – 918
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA,Weinheim
www.chemeurj.org
917

V. Percec et al.
5d was used. A colorless solid was obtained (89% yield). 1H NMR
(CDCl3,TMS): d=7.65 (s,2H),7.64 (m,2H),7.42 (d,2H),6.84 (d,2H),
4.91 (d,1H),4.04 (t,4H),4.01 (t,2H),3.85 (m,1H),3.41–3.34 (overlap-
ped peaks,m,8H),1.79 (m,12H),1.45 (m,10H),1.31–1.26 (overlapped
Chem. Soc. 2004, 126,6078–6094; c) V. Percec,M. N. Holerca,S.
Nummelin,J. J. Morrison,M. Glodde,J. Smidrkal,M. Peterca,B. M.
Rosen,S. Uchida,V. S. K. Balagurusamy,M. J. Sienkowska,P. A.
Heiney, Chem. Eur. J. 2006, 12,6216–6241; d) V. Percec,M. Peterca,
peaks,m,67H),1.11 (m,5H),0.88 (t,12H),0.81 ppm (d,6H);
13C NMR
M. J. Sienkowska,M. A. Ilies,E. Aqad,J. Smidrkal,P. A. Heiney,
Am. Chem. Soc. 2006, 128,3324–3334.
J.
(CDCl3,TMS): d=167.74,158.59,152.31,149.33,127.20,120.22,113.16,
112.84,69.68,69.56,47.12,44.35,39.23,38.04,37.13,32.32,31.28,30.09,
30.04,29.85,29.81,29.75,29.67,29.56,28.87,26.45,26.40,24.45,23.07,
22.92,21.95,14.48 ppm; MALDI-TOF MS: m/z: 1271.50 [M+H++K+],
1256.83 [M+H++Na+],1232.78 [ M+H+].
[5] a) V. Percec,A. E. Dulcey,V. S. K. Balagurusamy,Y. Miura,J.
Smidrkal,M. Peterca,S. Nummelin,U. Edlund,S. D. Hudson,P. A.
Heiney,H. Duan,S. N. Magonov,S. A. Vinogradov,
Nature 2004,
430,764–768; b) V. Percec,A. E. Dulcey,M. Peterca,M. Ilies,J. S.
Ladislaw,B. M. Rosen,U. Edlund,P. A. Heiney,
Angew. Chem.
1,1-Bis(3-ACHTREUNG(3,4-bis(3’,4’-bis(dodecan-1-yloxy)benzyloxy)benzamido)prop-
2005, 117,6674–6679; Angew. Chem. Int. Ed. 2005, 44,6516–6521;
c) V. Percec,A. E. Dulcey,M. Peterca,M. Ilies,Y. Miura,U.
Edlund,P. A. Heiney, Aust. J. Chem. 2005, 58,472–482; d) V.
Percec,A. E. Dulcey,M. Peterca,M. Ilies,M. J. Sienkowska,P. A.
Heiney, J. Am. Chem. Soc. 2005, 127,17902–17909; e) M. Peterca,
V. Percec,A. E. Dulcey,S. Nummelin,S. Korey,M. Ilies,P. A.
Heiney, J. Am. Chem. Soc. 2006, 128,6713–6720; f) V. Percec,A. E.
Dulcey,M. Peterca,M. Ilies,S. Nummelin,M. J. Sienkowska,P. A.
Heiney, Proc. Natl. Acad. Sci. USA 2006, 103,2518–2523.
yl)-3-(6-methylheptan-2-yl)urea (5 f): A synthetic procedure analogous to
the synthesis of 5d was used. A colorless solid was obtained (87% yield).
1H NMR (CDCl3,TMS): d=7.60 (s,2H),7.37 (d,2H),7.27 (m,2H),
7.00–6.81 (overlapped peaks,m,14H),5.09 (s,4H),5.07 (s,4H),4.83 (d,
1H),3.96 (t,8H),3.91 (t,8H),3.44–3.34 (overlapped peaks,m,8H),1.77
(m,20H),1.44 (m,18H),1.32–1.26 (overlapped peaks,m,131H),1.11
(d,5H),0.88 (t,24H),0.79 ppm (d,6H);
13C NMR (CDCl3,TMS): d=
167.40,158.62,152.15,149.78,149.74,149.42,149.40,149.29,130.02,
129.81,127.91,120.70,120.64,120.39,114.37,114.20,113.95,113.66,71.64,
71.55,69.81,69.64,47.14,44.31,39.24,38.08,37.10,32.34,30.09,29.92,
29.89,29.79,28.93,28.27,26.53,26.49,24.43,23.09,22.98,22.95,22.02,
14.50 ppm; MALDI-TOF MS: m/z: 2433.90 [M+H++K+],2418.02
[M+H++Na+],2394.78 [ M+H+].
[6] a) S. D. Hudson,H.-T. Jung,V. Percec,W.-D. Cho,G. Johansson,G.
Ungar,V. S. K. Balagurusamy,
Science 1997, 278,449–452;
b) V. S. K. Balagurusamy,G. Ungar,V. Percec,G. Johansson, J. Am.
Chem. Soc. 1997, 119,1539–1555; c) V. Percec,W.-D. Cho,P. E.
Mosier,G. Ungar,D. J. P. Yeardley, J. Am. Chem. Soc. 1998, 120,
11061–11070; d) V. Percec,W.-D. Cho,G. Ungar, J. Am. Chem. Soc.
2000, 122,10273–10281; e) V. Percec,W.-D. Cho,G. Ungar,D. J. P.
Yeardley, J. Am. Chem. Soc. 2001, 123,1302–1315; f) V. Percec,
M. N. Holerca,S. Uchida,W.-D. Cho,G. Ungar,Y. Lee,D. J. P.
Yeardley, Chem. Eur. J. 2002, 8,1106–1117.
Typical procedure for gelation experiments:
A carefully measured
amount of solid (4–60 mg) was put into an NMR tube with a tight-fit
twist cap and organic solvent (0.5 or 1 mL) was added. The mixture was
carefully heated in an oil bath. Upon dissolution,the solution was slowly
cooled to 238C. If the tube was inverted and the liquid did not flow,it
was considered to be a gel. The tube was left for observation for 2 days
at 238C.
[7] G. Ungar,Y. Liu,X. Zeng,V. Percec,W.-D. Cho,
1208–1211.
Science 2003, 299,
[8] X. Zeng,G. Ungar,Y. Liu,V. Percec,A. E. Dulcey,J. K. Hobbs,
Nature 2004, 428,157–160.
[9] a) G. Ungar,D. Abramic,V. Percec,J. A. Heck, Liq. Cryst. 1996, 21,
73–86; b) V. Percec,C.-H. Anh,T. K. Bera,G. Ungar,D. J. P.
Yeardley, Chem. Eur. J. 1999, 5,1070–1083; c) V. Percec,T. K. Bera,
M. Glodde,Q. Fu,V. S. K. Balagurusamy,P. A. Heiney, Chem. Eur.
J. 2003, 9,921–935; d) V. Percec,M. R. Imam,T. K. Bera,V. S. K.
Balagurusamy,M. Peterca,P. A. Heiney, Angew. Chem. 2005, 117,
4817–4823; Angew. Chem. Int. Ed. 2005, 44,4739–4745.
Acknowledgement
Financial support by the National Science Foundation (grant nos.: DMR-
05-48559 and DMR-05-20020),DuPont–Marshall Laboratories,and the
P. Roy Vagelos Chair at the University of Pennsylvania are gratefully ac-
knowledged.
[10] a) Z. J. Kaminski, Tetrahedron Lett. 1985, 26,2901–2904; b) M. Ku-
nishima,C. Kawachi,J. Morita,K. Terao,F. Iwasaki,S. Tani,
Tetra-
[1] a) P. Terech,R. G. Weiss, Chem. Rev. 1997, 97,3133–3159; b) J. H.
van Esch,B. L. Feringa, Angew. Chem. 2000, 112,2351–2354;
Angew. Chem. Int. Ed. 2000, 39,2263–2266; c) D. J. Abdallah,R. G.
Weiss, Adv. Mater. 2000, 12,1237–1247; d) M. George,R. G. Weiss,
Acc. Chem. Res. 2006, 39,489–497; e) K. Sada,M. Takeuchi,N.
Fujita,M. Numata,S. Shinkai, Chem. Soc. Rev. 2007, 36,415–435.
hedron 1999, 55,13159–13170; c) M. Kunishima,C. Kawachi,F.
Iwasaki,K. Terao,S. Tani, Tetrahedron Lett. 1999, 40,5327–5330;
d) Z. J. Kaminski, Biopolymers 2000, 55,140–164; e) C. E. Garrett,
X. Jiang,K. Prasad,O. Repic,
4165.
Tetrahedron Lett. 2002, 43,4161–
[11] a) H. A. Staab, Angew. Chem. 1962, 74,407–423; Angew. Chem. Int.
Ed. Engl. 1962, 1,1351–1367; b) S. P. Rannard,N. J. Davis, Org.
Lett. 1999, 1,933–936; c) S. P. Rannard,N. J. Davis, Org. Lett. 2000,
[2] a) M. de Loos,J. van Esch,R. M. Kellogg,B. L. Feringa,
Angew.
Chem. 2001, 113,633–636; Angew. Chem. Int. Ed. 2001, 40,613–
616; b) L. Estroff,A. D. Hamilton, Chem. Rev. 2004, 104,1201–
1217; c) J. J. van Gorp,J. A. J. M. Vekemans,E. W. Meijer, J. Am.
Chem. Soc. 2002, 124,14759–14769.
2,2117–2120; d) S. Rannard,N. Davis,H. McFarland,
2000, 49,1002–1006.
Polym. Int.
[12] a) K. Hanabusa,K. Okui,K. Karaki,T. Koyama,H. Shirai,
J. Chem
[3] a) J. van Esch,F. Schoonbeek,M. de Loos,H. Kooijman,A. L.
Spek,R. M. Kellogg,B. L. Feringa, Chem. Eur. J. 1999, 5,937–950;
b) M. de Loos,A. G. J. Ligtenbarg,J. van Esch,H. Kooijman,A. L.
Soc. Chem. Commun. 1992,1371–1373; b) K. Hanabusa,J. Tange,
Y. Taguchi,T. Koyama,H. Shirai, J. Chem Soc. Chem. Commun.
1993,390–392.
Spek,R. Hage,R. M. Kellogg,B. L. Feringa,
Eur. J. Org. Chem.
[13] a) W.-D. Jang,D.-L. Jiang,T. Aida, J. Am. Chem. Soc. 2000, 122,
2000,3675–3678; c) M. Lescanne,P. Grondin,A. dꢁAlØo,F. Fages,
J.-L. Pozzo,O. M. Monval,P. Reinheimer,A. Colin, Langmuir 2004,
20,3032–3041; d) X. Huang,P. Terech,S. R. Raghavan,R. G. Weiss,
J. Am. Chem. Soc. 2005, 127,4336–4344; e) X. Huang,S. R. Ragha-
van,P. Terech,R. G. Weiss, J. Am. Chem. Soc. 2006, 128,15341–
15352.
3232–3233; b) C. Kim,K. T. Kim,Y. Chang,
J. Am. Chem. Soc.
2001, 123,5586–5587; c) W.-D. Jang,T. Aida, Macromolecules 2003,
36,8461–8469; d) A. R. Hirst,D. K. Smith,M. C. Feiters,H. P. M.
Geurts,A. C. Wright, J. Am. Chem. Soc. 2003, 125,9010–9011.
[14] V. Percec,C.-H. Anh,G. Ungar,D. J. P. Yeardley,M. Mçller,S. S.
Sheiko, Nature 1998, 391,161–164.
[4] a) V. Percec,W.-D. Cho,G. Ungar,D. J. P. Yeardley, Angew. Chem.
2000, 112,1661–1666; Angew. Chem. Int. Ed. 2000, 39,1597–1602;
b) V. Percec,C. M. Mitchell,W.-D. Cho,S. Uchida,M. Glodde,G.
Received: August 16,2007
Ungar,X. Zeng,Y. Liu,V. S. K. Balagurusamy,P. A. Heiney,
J. Am.
Published online: November 19,2007
918
www.chemeurj.org
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA,Weinheim
Chem. Eur. J. 2008, 14,909 – 918