Induction of liquid-crystallinity in molecular clips by binding of different guest molecules

Article abstract of DOI:10.1039/a700936d

The use of clip molecules based on diphenyl- and dimethyl-glycoluril as building blocks for liquid-crystalline materials is described. The synthesis is performed by an esterification of hydroxy-derived clip molecules with trialkoxybenzoyl chloride. ¹

Full text of DOI:10.1039/a700936d

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Induction of liquid-crystallinity in molecular clips by binding of
different guest molecules
Johanna L. M. van Nunen and Roeland J. M. Nolte*
Department of Organic Chemistry, NSR Center, University of Nijmegen, Toernooiveld,
6525 ED Nijmegen, The Netherlands
The use of clip molecules based on diphenyl- and dimethyl-glycoluril as building blocks for liquid-
crystalline materials is described. The synthesis is performed by an esterification of hydroxy-derived clip
molecules with trialkoxybenzoyl chloride. 1H N M R titrations show that these molecules, despite the steric
crowding, are still able to bind guest molecules in the cleft. The clip molecules show no liquid-crystalline
properties, except those based on dimethylglycoluril. H owever, clips with alkyl chains of at least ten
carbon atoms display liquid-crystalline behaviour upon binding of guest molecules, which can be tuned
by the substituent of the guest molecules.
Introduction
The development of molecular materials with tunable proper-
ties is a topic of great current interest and in this respect liquid-
crystallinity is receiving much attention.1 Recently, molecular
recognition has been used as a tool to control the properties of
liquid-crystalline materials. Different receptor molecules, e.g.
macroheterocyclic ligands2–4 and cone-shaped molecules,5–8
have been synthesized and studied for this purpose. Percec et
al.2 investigated the engineering of the liquid-crystalline
behaviour of crown-ether-containing polymers with the help
of alkali metal ions, and Ringsdorf et al.4a demonstrated that
liquid-crystallinity can be induced in aza-crown ether deriva-
tives by complexation of metal ions. In cone-shaped mesogens,
based on e.g. cycloveratrylenes5 and calixarenes,6,7 the bowl-like
rigid central core can act as a receptor site. It has been shown
that in the mesophase the bowl-like cores are stacked 5–7 and
that this arrangement can be disturbed upon binding of a guest
molecule in the receptor sites, leading to the loss of liquid-
crystallinity.7
In previous work, we reported on molecular clips, which
are able to bind neutral molecules, e.g. 1 8 and 2.9 These clip
molecules contain a concave framework, which is based on the
molecule diphenylglycoluril. A cleft is formed when this frame-
work is flanked by two aromatic walls. Compound 1 [Fig. 1(a)]
has a rigid, well-defined binding site. It can bind dihydroxyben-
zenes, which are clamped in the cavity of the receptor by hydro-
gen bonding and π–π stacking interactions (association con-
stant of the complex with resorcinol, Ka = 2600 ± 400 dm3
molϪ1). Hydrogen bonding takes place between the hydroxy
functions of the guest molecule and the carbonyl groups of the
glycoluril moiety of the host molecule. π–π Stacking occurs
between the aromatic rings of host and guest. The molecules of
compound 2 exist in three conformations [Fig. 1(b)]: anti–anti
(aa), syn–anti (sa) and syn–syn (ss). The conformers differ in the
way the walls are orientated relative to the phenyl groups of the
diphenylglycoluril part. The molecules of 2 change from one
Fig. 1 Structures of receptor molecules 1 and 2
conformation to another by the flipping of one naphthalene
wall. Only the aa conformer has the right geometry to bind
electron-poor aromatic guests in its cavity (Ka = 115 ± 20 dm3
The tendency of compounds to form liquid-crystalline
molϪ1 for 1,3-nitrobenzene in CDCl3).9
phases is dependent on the lateral interactions between the
molecules. If these interactions are too strong, no liquid-
crystalline phase will form. If these are weakened, a layer type
smectic phase may be generated, and if these are weakened even
further, a nematic phase may appear. It occurred to us that the
phenyl groups of the diphenylglycoluril moiety might be too
bulky and as a result the interactions between the molecules
We assumed that by using receptor molecules of types 1 and 2
as building blocks for liquid-crystalline materials, the properties
of these materials might be influenced by the binding of guest
molecules. To investigate this we have modified 1 and 2 with
four 3,4,5-trialkoxybenzoyl groups in order to create a central
rigid core surrounded by flexible chains.10
J. Chem. Soc., Perkin Trans. 2, 1997
1473

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too weak. For this reason we also synthesized molecules derived
from dimethylglycoluril.
target molecules 11, which are derived from the receptor mol-
ecule with 2,7-dihydroxynaphthalene walls are presented in
Scheme 2.
In this paper we present the synthesis, characterization and
binding properties of clip molecules substituted with long ali-
phatic chains. The influence of complexation of guest mol-
ecules on the liquid-crystalline behaviour of these molecules
will be described.11
HO
OH
Ph
Ph
N
N
N
N
O
O
Results and discussion
Synthesis
HO
OH
Receptor molecule 5 was synthesized in 75% yield by refluxing
compound
3 with an excess of hydroquinone in 1,2-
dichloroethane in the presence of toluene-p-sulfonic acid
(TsOH) as a catalyst.12 The same procedure starting from 4
could be used for the synthesis of compound 6, giving almost
the same yield. Before trying to synthesize the target molecules
8 and 9, some test reactions were performed with benzoic acid
and receptor molecule 5. First, the esterification reaction of 5
with dicyclohexylcarbodiimide (DCC) and dimethylamino-
pyridine (DMAP) in different solvents was attempted, but only
the benzoylurea byproduct was obtained.13 In an alternative
procedure a suspension of the host molecule with sodium
hydride in tetrahydrofuran (THF ) was refluxed and after one
hour benzoyl chloride was slowly added.14 This procedure
enabled us to synthesize all the target molecules 8 and 9 in
yields ranging from 40–80% (Scheme 1). The syntheses of the
10
RΟ
RΟ
RΟ
O
Cl
NaH–THF
7
RΟ
OR
O
O
RΟ
OR
O
O
RΟ
RΟ
OR
OR
Ph
N
N
N
O
O
O
N
Ph
HO
O
OH
O
O
O
R
OR
RΟ
R
R
N
N
N
N
N
N
N
N
O
O
pTosOH
OR
RΟ
O
O
hydroquinone
R
O
R
aa
29%
sa
ss
11a C8H17
64% 7%
63% 6%
61% 6%
HO
OH
11b C10H21 31%
11c C12H25 33%
3 R = Ph
4 R = Me
5 R = Ph
6 R = Me
Scheme 2
R′Ο
Properties of the molecular clips derived from hydroquinone
1H NMR titrations8 were performed to determine the binding
properties of the substituted molecular clips. The association
constant for the complex of resorcinol (DHB) with compound
8a was calculated to be Ka = 1000 ± 150 dm3 molϪ1. Substitu-
tion of a methoxy group (compound 1) by a modified benzoyl
group (compound 8a) reduces the binding constant by a factor
of approximately two. In order to study the influence of the
length of the alkyl chains of the molecular clips on the binding
properties, the association constants of the complexes between
1,3-dihydroxy-5-pentylbenzene (pentylresorcinol) and both 8a
and 8d were determined. Pentylresorcinol was used instead of
resorcinol because of the higher solubility of this guest. The
association constants were calculated to be Ka = 605 ± 100 dm3
molϪ1 for compound 8a and Ka = 645 ± 100 dm3 molϪ1 for
compound 8d. Apparently, the length of the alkyl substituent
does not significantly influence the binding properties of these
receptor molecules.
O
R′Ο
R′Ο
Cl
NaH–THF
7
R′Ο
OR′
O
O
R′Ο
O
O
OR′
R′Ο
OR′
OR′
R
N
N
N
N
O
O
R
R′Ο
R′Ο
O
O
OR′
O
O
R′Ο
OR′
Molecular clips 8a–d were designed to be liquid-crystalline
materials. Remarkably, compounds 8a and 8b were found to be
crystalline compounds with melting points of 175 and 159 ЊC,
respectively. Compound 8c could only be crystallized by anneal-
ing for 2 h at 81 ЊC. The crystals melted at 93–96 ЊC. Compound
8d did not crystallize even after annealing. In the case of 8a and
8b the rigid diphenylglycoluril framework clearly dominates
the structure so crystalline materials are obtained. Due to their
R
R′
8a Ph C6H13
8b Ph C8H17
8c Ph C10H21
8d Ph C12H25
9a Me C10H21
9b Me C12H25
Scheme 1
1474
J. Chem. Soc., Perkin Trans. 2, 1997

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Table 1 Assignments of 1H NMR resonances to conformations of
11ca
Conformer NCHHAr
NCHHAr
Naph-H(3,6) Naph-H(4,5)
sa
5.89(s);
5.50(a)
5.89
5.06(s);
4.31(a)
5.23
7.38(s);
7.13(a)
7.44
7.91(s);
7.38(a)
—
b
ss
aa
5.42
4.16
7.23
7.73
Conformer Ph-H(2,6)
Ph-H(3,5)
Ph-H(4)
(RO)3Ar-H
7.69; 7.53
sa
6.50(s);
6.83(a)
ca. 7.0
6.91
6.29(s);
7.01(a)
6.23
6.37(s);
7.01(a)
ca. 7.0
6.92
ss
7.56
7.66
aa
7.03
a
In CDCl3 with [11c] = 5 m. Chemical shifts are in ppm relative to
tetramethylsilane. The designations (s) and (a) are used for syn and
anti, see text. b Due to the low abundance of the conformer or com-
plexity of the signals, no assignments could be made.
Fig. 2 Liquid-crystalline behaviour of molecular clip 9b (top). Texture
of the mesophase at 40 ЊC, as viewed under a polarizing microscope
(bottom).
almost completely shifted to the aa conformer (Fig. 3). The
resonances could be assigned by taking the following points
into consideration: (i) the presence of a guest molecule in the
cleft will significantly shift the signals, (ii) placing a naphthyl
group into the syn orientation will cause a considerable upfield
shift of the naphthyl and phenyl signals, due to the ring current
effects of these moieties, (iii) the methylene protons of the sa
conformer must give rise to two AX systems with equal inten-
sity.9 The assignments of the most important signals of com-
pound 11c are given in Table 1. The positions of the 1H NMR
signals were found to be dependent on the concentration of
receptor molecules 11a–c, but the signals were independent of
the chain length of the substituents. At the same concentration
(5 m), the ratio of the three conformers was almost identical
for the different clip molecules. The association constants for
1
complexation of resorcinol, determined by H NMR titration
experiments, did not differ significantly for receptor molecules
11a and 11c. These are calculated to be Ka = 408 ± 80 and
450 ± 80 dm3 molϪ1, respectively.
Compounds 11a–c are crystalline compounds with melting
ranges of 203–205 for 11a, 177–179 for 11b and 159–164 ЊC for
11c. Upon fast cooling from the liquid state, compound 11c
showed a thermodynamically unstable (monotropic) liquid-
crystalline phase, viz. a nematic phase with a clearing point of
161 ЊC.11
Fig. 3 1H NMR spectra of (a) molecular clip 11c and (b) 11c with 4
equiv. of resorcinol (R)
longer flexible alkyl chains, compounds 8c and 8d were expected
to be liquid-crystalline, but for some unknown reason this was
not the case. On the other hand, molecular clips 9a and 9b,
derived from dimethylglycoluril, displayed liquid-crystalline
behaviour. The nature of the optical textures, which were
observed by polarizing microscopy, and the magnitudes of the
enthalpy changes, which were measured by differential scan-
ning calorimetry (DSC), indicated that a smectic phase was
formed between 1 and 225 ЊC for compound 9a, and between
Ϫ4 and 160 ЊC for compound 9b. Upon cooling an additional
highly ordered smectic phase was visible for the latter com-
pound (Fig. 2). Substitution of the phenyl groups on the convex
side of the molecular clip with methyl groups leads, apparently,
to liquid-crystalline properties. This is probably due to a
decrease in steric bulk, allowing better stacking of the central
cores of the molecules.
Induction of liquid-crystallinity by complexation of guest
molecules
In order to study the influence of host–guest complexation on
the melting behaviour we prepared complexes of clip molecules
8 and 11 with dihydroxybenzene derivatives.15 Two different
guest molecules, viz. resorcinol and methyl 3,5-dihydroxy-
benzoate (MDB), were used. The complexes with molecular
clips 8 are described in Table 2. From earlier studies it is known
that MDB binds approximately six times as strongly as DHB
in clip 1.16
Complexation of guest molecules in clips 8a and 8b only
slightly changes the melting points of the host molecules, as is
described in Table 2. In clips 8c and 8d, however, complexation
of DHB or MDB induces a liquid-crystalline phase. The com-
plex of 8c with DHB displayed a nematic phase directly after
cooling, whereas the complex of 8c with MDB and both com-
plexes of 8d exhibited smectic-like phases (Fig. 4). For some
complexes the more highly ordered mesophase (described as M
in Table 2), which is present in the DSC-thermogram, could not
be assigned unequivocally as the transition temperature of the
mesophase upon cooling fell outside the temperature range of
the polarizing microscope. A comparison of the data of the
complexes in Table 2 shows that the melting points of the com-
plexes of 8a and 8b are almost the same as the melting points of
the free clips. For the liquid-crystalline complexes of 8c and 8d
Properties of the molecular clips derived from 2,7-dihydroxy-
naphthalene
Interpretation of the 1H NMR spectra of clips 11a–c is compli-
cated by the fact that these molecules have three conformations
[aa, sa and ss, Fig. 1(b)], which interconvert slowly on the NMR
timescale. Earlier work performed in our laboratory showed
that the binding of a suitable guest molecule in receptor mol-
ecule 2 increases the relative amount of the aa conformer, which
is the dominant binding conformer.9 We found that upon add-
ition of an excess of resorcinol to a solution of one of the
receptor molecules 11, the equilibrium of the conformers was
J. Chem. Soc., Perkin Trans. 2, 1997
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Fig. 4 Thermogram of the 1:1 complex of DHB with 8d (left) and the texture of the mesophase at 51 ЊC, as viewed under a polarizing microscope
(right)
Fig. 5 Thermogram of the 1:1 complex of MDB with 11b (left) and the texture of the mesophase at 109 ЊC as viewed under a polarizing
microscope (right)
Table 2 Phase transition temperatures (ЊC) and (in parentheses)
enthalpy changes (kJ molϪ1) of complexes of dihydroxybenzene deriv-
atives with molecular clips 8a–da
Table 3 Phase transition temperatures (ЊC) and (in parentheses)
enthalpy changes (kJ molϪ1) of complexes of dihydroxybenzene deriva-
tives with molecular clips 11a
Uncomplexed 1:1 Complex with
1:1 Complex with
MDB
Uncomplexed
Clip host
1:1 Complex with
DHB
1:1 Complex with
MDB
Clip host
DHB
8a
8b
8c
K175I
K159I
K93–96I
K179(65.87)I
—
K47(50.75)M64(0.92)
N81(3.91)I
K181(57.72)I
K149(28.20)I
K2(37.05)M37(0.57)
S107(16.86)I
11a
11b
11c
K203–205I
K177–179I
K159–164I
—
K173I b
K114S130I b
K124S134I b
K14(58.40)S78(1.12) K14(68.56)N131(3.53)I
SЈ141(9.18)I
8d
—
K54(79.19)S88(15.01)I K48(47.06)M59(1.27)
S102(29.96)I
a
DHB: 1,3-dihydroxybenzene, MDB: methyl 3,5-dihydroxybenzoate.
Values were determined by DSC. b Values were determined by polar-
izing microscopy. K: crystalline phase, S: smectic phase, N: nematic
phase, D: sicotic phase, I: isotropic phase.
a
DHB: 1,3-dihydroxybenzene, MDB: methyl 3,5-dihydroxybenzoate.
Values were determined by DSC. K: crystalline phase, S: smectic phase,
N: nematic phase, D: sicotic phase, I: isotropic phase.
of the alkyl chains as in the complexes with 11c, however,
broadened the liquid-crystalline range to more than 100 ЊC.
The complex of 11c with resorcinol exhibited two different
smectic phases, whereas the complex with MDB displayed only
one, nematic, phase. If the complexes of the three different clips
are compared (Table 3), one can conclude that a decrease in
the alkyl chain length is accompanied by a strong increase of
the melting point together with a relatively small change in the
clearing point. At a certain chain length the melting point will
become higher than the clearing point, which may explain why
no mesophase is observed for the complex of MDB with 11a.
a broadening of the liquid crystalline range is observed when
MDB, instead of DHB, is bound in the clip molecules.
Remarkably, the MDB complex of 8c showed a liquid-
crystalline phase over a wider temperature range, viz. 105 ЊC,
than the corresponding complex of 8d (54 ЊC), whereas this
difference is not that significant for the complexes of 8c and 8d
with DHB. In general we may conclude that the rigid diphenyl-
glycoluril framework is the determining factor for the melting
behaviour of 8a and 8b, whereas in the case of 8c and 8d the
bulk of the alkyl chains are dominant.
The influence of guest molecules on the melting behaviour of
molecular clips 11 is presented in Table 3. When a dihydroxy-
benzene derivative is bound in clip 11a only a decrease in the
melting point was observed, whereas a corresponding complex-
ation in clips 11b and 11c induced liquid-crystalline behaviour,
i.e. the formation of smectic and nematic phases.
The smectic phases observed for the complexes of clip 11b
covered only a small range of 10–15 ЊC. For the complex with
MDB a smectic phase was formed over such a small tempera-
ture range that peak separation was only obtained in the cool-
ing curve of the thermogram (Fig. 5). An increase in the length
Conclusions
We have shown that clip molecules, derived from diphenyl- and
dimethyl-glycoluril, modified with alkoxy-substituted benzoyl
groups can be conveniently prepared by an esterification reac-
tion. The introduction of bulky trialkoxybenzoyl substituents
decreases the binding of resorcinol derivatives in these receptor
molecules compared to the methoxy derivative. The length of
the aliphatic chains (C6H13 to C12H25 derivative) does not influ-
ence the binding strength.
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J. Chem. Soc., Perkin Trans. 2, 1997

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Elongation of the alkyl substituent does not lead to liquid-
crystallinity in molecular clips 8a–d. The dimethylglycoluril
derivatives 9a and 9b, however, do have a mesophase. Appar-
ently, a smaller substituent on the convex side of these receptor
molecules allows a better stacking of the central cores. In the
case of the molecular clips with naphthalene walls, we were
more successful in introducing liquid-crystalline properties by
changing the length of the alkyl chains, viz. for compound 11c a
monotropic liquid-crystalline phase was observed.
trialkoxybenzoyl chloride 7 (4.4 equiv.), in a mixture of THF
and CH2Cl2 (1:1 v/v, 5n ml), was added. The mixture was
stirred for 2–24 h and subsequently quenched with a few drops
of water. The solvent was evaporated under reduced pressure
and the residue was dissolved in CHCl3. The organic layer was
extracted twice with aqueous 1  HCl, then with H2O, and dried
(MgSO4). The crude product was subjected to flash column
chromatography (eluent ethyl acetate–hexane, 1:19–25 v/v).
5,7,12,13b,13c,14-Hexahydro-1,4,8,11-tetrakis[(3,4,5-
Complexation of DHB or MDB induces liquid-crystallinity
in the trialkoxybenzoyl substituted clips, when the alkoxy
groups are at least ten carbon atoms long. The MDB complexes
of 8c and 8d have more ordered liquid-crystalline phases over a
wider temperature range than the complexes of DHB. This
effect is less pronounced in the complexes with clips 11a and
11b. Apparently, enlargement of the rigid core from two 1,4-
dihydroxybenzene to two 2,7-dihydroxynaphthalene walls
masks, to some extent, the influence of the alkyl substituents
and the complexation of guest molecules on the melting
behaviour. In conclusion, the receptor molecules described are
very promising building blocks for the construction of liquid-
crystalline materials. As far as we know, this is the first example
of induction of liquid-crystallinity in receptor molecules by the
complexation of neutral guest molecules.
trihexyloxy)benzyloxy]-13b,13c-diphenyl-6H,13H-
5a,6a,12a,13a-tetraazabenz[5,6]azuleno[2,1,8-
ija]benz[ f ]azulene-6,13-dione 8a. Yield 50%. K 175 ЊC I. δH (100
MHz, CDCl3) 7.57 [8H, s, ArH(OR)3], 7.15 (4H, s, ArH), 7.03
(10H, br s, ArH), 5.25 (4H, d, J 16, NCHHAr), 4.22–3.73 (28H,
m, NCHHAr and OCH2), 2.00–1.10 [96H, m, OCH2(CH2)4],
0.88 (36H, t, CH3). FAB-MS (m-nitrobenzyl alcohol) m/z 2179
(M ϩ H)ϩ (Found: C, 72.48; H, 8.55; N, 2.61. Calcd. for
C132H186N4O22: C, 72.70; H, 8.60; N, 2.57%).
5,7,12,13b,13c,14-Hexahydro-1,4,8,11-tetrakis[(3,4,5-tri-
octyloxy)benzyloxy]-13b,13c-diphenyl-6H,13H-5a,6a,12a,13a-
tetraazabenz[5,6]azuleno[2,1,8-ija]benz[ f ]azulene-6,13-dione
8b. Yield 78%. K 159 ЊC I. δH (100 MHz, CDCl3) 7.56 [8H, s,
ArH(OR)3], 7.13 (4H, s, ArH), 7.00 (10H, br s, ArH), 5.23 (4H,
d, J 16, NCHHAr), 4.22–3.78 (28H, m, NCHHAr and OCH2),
2.00–1.10 [144H, m, OCH2(CH2)6], 0.88 (36H, t, CH3) (Found:
C, 74.60; H, 9.58; N, 2.24. Calcd. for C156H234N4O22: C, 74.43;
H, 9.37; N, 2.23%).
Experimental
General methods
5,7,12,13b,13c,14-Hexahydro-1,4,8,11-tetrakis[(3,4,5-tri-
decyloxy)benzyloxy]-13b,13c-diphenyl-6H,13H-5a,6a,12a,13a-
tetraazabenz[5,6]azuleno[2,1,8-ija]benz[ f ]azulene-6,13-dione
8c. Yield 40%. K 93–96 ЊC I. δH (100 MHz, CDCl3) 7.58 [8H,
s, ArH(OR)3], 7.16 (4H, s, ArH), 7.00 (10H, br s, ArH), 5.22
(4H, d, J 16, NCHHAr), 4.39–3.79 (28H, m, NCHHAr and
OCH2), 2.00–1.12 [192H, m, OCH2(CH2)8], 0.87 (36H, t, CH3)
(Found: C, 75.18; H, 9.98; N, 1.92. Calcd. for C180H282N4O22:
C, 75.75; H, 9.96; N, 1.96%).
5,7,12,13b,13c,14-Hexahydro-1,4,8,11-tetrakis[(3,4,5-trido-
decyloxy)benzyloxy]-13b,13c-diphenyl-6H,13H-5a,6a,12a,13a-
tetraazabenz[5,6]azuleno[2,1,8-ija]benz[ f ]azulene-6,13-dione
8d. Yield 43%. δH (400 MHz, CDCl3) 7.59 [8H, s, ArH(OR)3],
7.16 (4H, s, ArH), 7.07–7.05 (6H, m, ArH), 6.98–6.96 (4H, m,
ArH), 5.22 and 3.99 (4H, 2 × d, J 16, NCHHAr), 4.09–3.96
(24H, m, OCH2), 1.82–1.26 [240H, m, OCH2(CH2)10], 0.87
(36H, t, CH3) (Found: C, 76.44; H, 10.57; N, 1.82. Calcd. for
C204H330N4O22: C, 76.79; H, 10.42; N, 1.76%).
5,7,12,13b,13c,14-Hexahydro-1,4,8,11-tetrakis[(3,4,5-tri-
decyloxy)benzyloxy]-13b,13c-dimethyl-6H,13H-5a,6a,12a,13a-
tetraazabenz[5,6]azuleno[2,1,8-ija]benz[ f ]azulene-6,13-dione
9a. Yield 63%. K 1 ЊC M 225 ЊC I. δH (100 MHz, CDCl3) 7.54
[8H, s, ArH(OR)3], 7.14 (4H, s, ArH), 5.12 (4H, d, J 16, NCH-
HAr), 4.28–3.77 (28H, m, NCHHAr and OCH2), 2.00–1.10
[198H, m, OCH2(CH2)8 and CH3], 0.88 (36H, t, CH3) (Found:
C, 74.55; H, 10.51; N, 2.08. Calcd. for C170H278N4O22: C, 74.79;
H, 10.26; N, 2.05%).
5,7,12,13b,13c,14-Hexahydro-1,4,8,11-tetrakis[(3,4,5-trido-
decyloxy)benzyloxy]-13b,13c-dimethyl-6H,13H-5a,6a,12a,13a-
tetraazabenz[5,6]azuleno[2,1,8-ija]benz[ f ]azulene-6,13-dione
9b. Yield 37%. K Ϫ4 ЊC M 160 ЊC I. δH (100 MHz, CDCl3) 7.54
[8H, s, ArH(OR)3], 7.14 (4H, s, ArH), 5.12 (4H, d, J 16, NCH-
HAr), 4.24–3.73 (28H, m, NCHHAr and OCH2), 2.00–1.10
[246H, m, OCH2(CH2)10 and CH3], 0.88 (36H, t, CH3) (Found:
C, 75.89; H, 10.70; N, 1.87. Calcd. for C194H326N4O22: C, 75.98;
H, 10.71; N, 1.83%).
CH2Cl2 was distilled from CaH2 and THF from LiAlH4. For
flash column chromatography Merck silica gel 60H was used.
Melting points were measured with a Jeneval polarizing micro-
scope connected to a Linkam THMS 600 hot stage. Thermo-
grams were recorded at a rate of 10 ЊC minϪ1 using a Perkin-
Elmer DSC 7 instrument. Samples were prepared in stainless-
steel large volume pans (75 µl).
8b,8c-Dihydro-8b,8c-dimethyl-1H,3H,4H,5H,7H,8H-2,6-
dioxa-3a,4a,7a,8a-tetraazacyclopenta[def]fluorene-4,8-dione 4.
This compound was synthesized as described in ref. 17.
5,7,12,13b,13c,14-Hexahydro-1,4,8,11-tetrahydroxy-13b,13c-
diphenyl-6H,13H-5a,6a,12a,13a-tetraazabenz[5,6]azuleno-
[2,1,8-ija]benz[ f ]azulene-6,13-dione 5. This compound was
synthesized from 3 according to a procedure developed pre-
viously in our laboratory.12
5,7,12,13b,13c,14-Hexahydro-1,4,8,11-tetrahydroxy-13b,13c-
dimethyl-6H,13H-5a,6a,12a,13a-tetraazabenz[5,6]azuleno-
[2,1,8-ija]benz[ f ]azulene-6,13-dione 6. This compound was syn-
thesized according to a procedure developed in our labor-
atory12 using compound 4 (1.0 g, 3.9 mol), TsOH (3.0 g, 16
mmol) in 1,2-dichloroethane (30 ml), and hydroquinone (1.7 g,
15 mmol). In order to remove traces of water a suspension of
product 6 in triethyl orthoformate was heated under reflux for 1
h. The precipitate was filtered, washed with CH2Cl2, and dried
in vacuo. Yield 71%. Mp >225 ЊC (decomp.); δH (100 MHz;
[2H6]DMSO; J values in Hz throughout) 6.43 (4H, s, OH), 5.74
(4H, s, ArH), 5.14 and 4.93 (4H, 2 d, J 16, CH2N), 1.70 (3H, s,
CH3). FAB-MS (m-nitrobenzyl alcohol) m/z 439 (M ϩ H)ϩ.
3,4,5-Trialkoxybenzoyl chloride 7. The corresponding 3,4,5-
trialkoxybenzoic acid 10 was refluxed in pure SOCl2. After 2 h
the reaction mixture was evaporated to dryness in vacuo and the
product was used without further purification.
17b,17c-Dihydro-1,6,10,15-tetrahydroxy-17b,17c-diphenyl-
7H,8H,9H,16H,17H,18H-7a,8a,16a,17a-tetraazapentaleno-
[1Љ,6Љ:5,6,7;3Љ,4Љ:5Ј,6Ј,7Ј]dicycloocta[1,2,3-de:1Ј,2Ј,3ЈdЈeЈ]-
dinaphthalene-8,17-dione 10. This compound was synthesized
according to a procedure developed previously in our labor-
atory.18
17b,17c-Dihydro-1,6,10,15-tetrakis[(3,4,5-trioctyloxy)benzyl-
oxy]-17b,17c-diphenyl-7H,8H,9H,16H,17H,18H-7a,8a,16a,
17a-tetraazapentaleno[1Љ,6Љ:5,6,7;3Љ,4Љ:5Ј,6Ј,7Ј]dicycloocta-
[1,2,3-de:1Ј,2Ј,3ЈdЈeЈ]dinaphthalene-8,17-dione 11a. Yield 63%.
K 204 ЊC I. δH (400 MHz, CDCl3); see Table 1 for uncomplexed
host. Host–guest complex: host: 7.66 [8H, s, ArH(OR)3], 7.41
and 7.01 (8H, 2 × d, J 9, naph-H), 7.15–7.04 (6H, m, ArH),
General procedure for the synthesis of compounds 8, 9 and 11
Receptor molecule 5, 6 or 10 (n mmol) and NaH (10n mmol)
were refluxed for 1 h in THF (10n ml). The appropriate 3,4,5-
J. Chem. Soc., Perkin Trans. 2, 1997
1477

View Article Online
6.94 (4H, d, ArH), 5.41 and 4.15 (8H, 2 × d, J 17, NCHHAr),
4.13–3.85 (24H, m, OCH2), 1.89–1.09 [144H, m, OCH2(CH2)6],
0.98–0.80 (36H, m, CH3); guest (resorcinol) 6.83 (t), 6.12 (dd),
5.40 (s), 5.27 (br s) (Found: C, 74.96; H, 9.22; N, 2.19. Calcd.
for C164H238N4O22: C, 75.25; H, 9.16; N, 2.14%).
17b,17c-Dihydro-1,6,10,15-tetrakis[(3,4,5-tridecyloxy)benzyl-
oxy]-17b,17c-diphenyl-7H,8H,9H,16H,17H,18H-7a,8a,16a,
17a-tetraazapentaleno[1Љ,6Љ:5,6,7;3Љ,4Љ:5Ј,6Ј,7Ј]dicycloocta-
[1,2,3-de:1Ј,2Ј,3ЈdЈeЈ]dinaphthalene-8,17-dione 11b. Yield 40%.
K 178 ЊC I. δH (400 MHz, CDCl3) see Table 1 for uncomplexed
host. Host–guest complex: host 7.68 [8H, s, ArH(OR)3], 7.45
and 7.00 (8H, 2 × d, J 9, naph-H), 7.13–7.04 (6H, m, ArH),
6.94 (4H, d, ArH), 5.42 and 4.15 (8H, 2 × d, J 17, NCHHAr),
4.13–3.78 (24 H m, OCH2), 1.87–1.18 [192H, m, OCH2(CH2)8],
0.95–0.81 (36H, m, CH3), guest (resorcinol) 6.93 (t), 6.24 (dd),
5.60 (br s) (Found: C, 76.12; H, 9.48; N, 1.95. Calcd. for
C188H286N4O22: C, 76.43; H, 9.76; N, 1.90%).
17b,17c-Dihydro-1,6,10,15-tetrakis[(3,4,5-tridodecyloxy)-
benzyloxy]-17b,17c-diphenyl-7H,8H,9H,16H,17H,18H-7a,8a,
16a,17a-tetraazapentaleno[1Љ,6Љ:5,6,7;3Љ,4Љ:5Ј,6Ј,7Ј]dicyclo-
octa[1,2,3-de:1Ј,2Ј,3ЈdЈeЈ]dinaphthalene-8,17-dione 11c. Yield
57%. K 159–162 ЊC I. δH (400 MHz, CDCl3) see Table 1 for
uncomplexed host. Host–guest complex: host: 7.67 [8H, s,
ArH(OR)3], 7.44 and 6.99 (8H, 2 × d, J 9, naph-H), 7.11–7.05
(6H, m, ArH), 6.94 (4H, d, ArH), 5.41 and 4.14 (8H, 2 × d, J
17, NCHHAr), 4.12–3.84 (24H, m, OCH2), 1.84–1.08 [240H,
m, OCH2(CH2)10], 1.04–0.80 (36H, m, CH3), guest (resorcinol)
6.90 (t), 6.21 (dd), 5.75 (br s), 5.49 (s) (Found: C, 77.13; H,
10.56; N, 1.67. Calcd. for C212H334N4O22: C, 77.37; H, 10.23; N,
1.70%).
References
1 V. Percec and D. Tomazos, Comprehensive Polymer Science, 1992, I,
300.
2 (a) V. Percec, G. Johansson and R. Rodenhouse, Macromolecules,
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3 (a) J.-M. Lehn, J. Malthête and A. M. Levelut, J. Chem. Soc., Chem.
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1091; (c) G. Lattermann, S. Schmidt, R. Kleppinger and J. H.
Wendorff, Adv. Mater., 1992, 4, 30.
5 J. Malthête and A. Collet, J. Am. Chem. Soc., 1987, 109, 7544.
6 T. Komori and S. Shinkai, Chem. Lett., 1993, 1455.
7 B. Xu and T. M. Swager, J. Am. Chem. Soc., 1993, 115, 1159.
8 (a) R. P. Sijbesma, A. P. M. Kentgens and R. J. M. Nolte, J. Org.
Chem., 1991, 56, 3199; (b) R. P. Sijbesma, A. P. M. Kentgens,
E. T. G. Lutz, J. H. van der Maas and R. J. M. Nolte, J. Am. Chem.
Soc., 1993, 115, 8999.
9 (a) R. P. Sijbesma and R. J. M. Nolte, J. Am. Chem. Soc., 1991, 113,
6695; (b) R. P. Sijbesma, S. S. Wijmenga and R. J. M. Nolte, J. Am.
Chem. Soc., 1992, 114, 9807.
10 V. Percec, M. Lee, J. Heck, H. E. Blackwell, G. Ungar and A.
Alvarez-Castillo, J. Mater. Chem., 1992, 2, 931.
11 For a related study see: J. L. M. van Nunen, B. J. B. Folmer and
R. J. M. Nolte, J. Am. Chem. Soc., 1997, 119, 283.
12 J. W. H. Smeets, R. P. Sijbesma, L. van Dalen, A. L. Spek, W. J. J.
Smeets and R. J. M. Nolte, J. Org. Chem., 1989, 54, 3710.
13 E. Vowinkel, Chem. Ber., 1967, 100, 16.
14 The reaction product of 5 and benzoyl chloride was obtained in
61% yield. δH (400 MHz, CDCl3) 8.38 (8H, d, J 16, ArH), 7.71–
7.67 (12H, m, ArH), 7.18 (4H, s, ArH), 7.10–7.00 (10H, m, ArH),
5.27 and 3.94 (8H, 2 d, J 16, CH2N).
15 During the course of our study we found out that complex formation
proceeds much better with the method described in this paper than
with the method published previously by us, cf. J. L. M. van Nunen,
R. S. A. Stevens, S. J. Picken and R. J. M. Nolte, J. Am. Chem. Soc.,
1994, 116, 8825.
Complex formation
The 1:1 complexes were prepared by mixing ca. 20 mg of clip
molecule (5–10 × 10Ϫ6 mol) and an equimolar amount (between
0.7–1.5 mg) of guest (5–10 × 10Ϫ6 mol) in 0.2 ml of CHCl3. If
necessary 1–3 drops of acetone were added. The solvent was
slowly evaporated overnight at 40 ЊC, and the complexes were
dried at room temperature using high vacuum.
For the DSC-measurements ca. 10 mg of complex was
weighed in a stainless-steel large volume pan (75 µl). Thermo-
grams were recorded at 10 ЊC minϪ1 and repeated heating and
cooling runs were recorded to study the stability of the complex
and the reproducibility of the measurements. Polarizing micro-
scopy was carried out using the same heating and cooling rates.
16 J. Reek, unpublished results. Binding constants of clip 1 with DHB
and MDB amount to Ka = 2600 and Ka = 15 000 dm3 molϪ1
respectively.
,
17 F. G. M. Niele and R. J. M. Nolte, J. Am. Chem. Soc., 1988, 110, 172.
18 R. P. Sijbesma and R. J. M. Nolte, Recl. Trav. Chim. Pays-Bas, 1993,
112, 643.
Paper 7/00936D
Received 3rd February 1997
Accepted 21st March 1997
1478
J. Chem. Soc., Perkin Trans. 2, 1997