Unprecedented role of water in self-assembly of potential molecular tweezers

Article abstract of DOI:10.1039/b001127o

The X-ray structures of three potential molecular tweezers, C₂₀H₂₄N₂O₅ (1), C₂₀H₂₀N₆O₁₃ (2) and C₂₈H₃₂N₂O₁₃ (3), differing only by the substituents on the terminal aromatic moieties, display three as yet unreported arrays. Hydrogen bonding with co-crystallized water molecules as well as van der Waals interactions between terminal aromatic moieties lead to specific packing patterns, namely: (i) a membrane-like architecture of associated molecular tapes in 1 · 2H₂O, (ii) coupled right- handed and left-handed helices in 2 · H₂O and (iii) a stepped arrangement provided by a back-to-back pairing in (3)₂ · H₂O. Molecular modelling of individual molecules in vacuo shows that the most stable conformers of 1-3 intrinsically display attractive interactions between the terminal aromatic groups, which stabilize a pseudocavity suitable for incorporation of a guest compound.

Full text of DOI:10.1039/b001127o

View Article Online / Journal Homepage / Table of Contents for this issue
Unprecedented role of water in self-assembly of potential molecular
tweezers
Sylvie Meyer,a Remy Louis,a,b Bernard Metz,a,b Yvette Agnus,a Alexandre Varnekc and
Maurice Gross*a
a L aboratoire dÏElectrochimie et Physico-chimie des Complexes et Systemes Interfaciaux (CNRS
UMR 7512), Universite L ouis Pasteur, 4 rue Blaise Pascal, 67008 Strasbourg cedex, France.
E-mail: gross=chimie.u-strasbg.fr; Fax: ]33 3 88 61 15 53
b L aboratoire de Biologie Structural (CNRS UPR 9004), Universite L ouis Pasteur, IGBMC,
1 rue L aurent Fries, 67404 Illkirch cedex, France
c L aboratoire de Chimie Quantique (CNRS UMR 7551), Universite L ouis Pasteur, 4 rue Blaise
Pascal, 67008 Strasbourg cedex, France
Received (in Strasbourg, France) 9th February 2000, Accepted 20th March 2000
Published on the Web 15th May 2000
The X-ray structures of three potential molecular tweezers, C
H
N O (1), C
H
N O (2) and C
13
H
N O
20 24
2
5
20 20
6
28 32
2
13
(3), di†ering only by the substituents on the terminal aromatic moieties, display three as yet unreported arrays.
Hydrogen bonding with co-crystallized water molecules as well as van der Waals interactions between terminal
aromatic moieties lead to speciÐc packing patterns, namely: (i) a membrane-like architecture of associated
molecular tapes in 1 É 2H O, (ii) coupled right-handed and left-handed helices in 2 É H O and (iii) a stepped
2
2
arrangement provided by a back-to-back pairing in (3) É H O. Molecular modelling of individual molecules in
2
2
vacuo shows that the most stable conformers of 1È3 intrinsically display attractive interactions between the terminal
aromatic groups, which stabilize a pseudocavity suitable for incorporation of a guest compound.
Molecular tweezers represent a family of host molecules pos-
sessing two terminal aromatic groups linked by a Ñexible
spacer bearing functional groups that are capable of complex-
ing metal cations or molecular guests. A large variety of
tweezers are known, depending on the nature of their terminal
groups and on the number and type of functional groups
constituting the spacer.1h5 Some of them can be used as
abiotic receptors for aromatic substrates,6 thus mimicking
biomolecular systems.7,8 Recently, we have described the
ecules 1È3 might be more appropriate ligands for the com-
plexation of hard metal cations and for the Ðxation of
molecular guests via hydrogen bonds.11h13
The three compounds have been crystallized at ambient
temperature and in air by slow evaporation of acetone (1),
toluene (2) and dimethylsulfoxide (3) solutions, respectively.
Unexpectedly, water molecules absorbed during the crys-
tallization process are present in the crystals. The water mol-
ecules play a role as guest and/or cement leading to three
di†erent inÐnite arrays: (i) a membrane-like architecture of
synthesis
of
a
tweezers-like
molecule
with
a
S[CH CH SCH C(O)NHÈ] spacer and two terminal 3,5-
associated molecular tapes in 1 É 2H O, (ii) coupled right-
2
2
2
2
2
handed and left-handed helices in 2 É H O and (iii) a stepped
2
dinitrophenyl fragments.5 The solid-state structure of its palla-
dium complex shows that the metal is encapsulated in a pseu-
docavity formed by the spacer and the nearly parallel (p-p
stacking9) terminal groups. Complexation of palladium or
platinum salts by tweezers with S[CH CH SCH C(O)NHÈ] ,
arrangement provided by a back-to-back pairing in (3) É H O.
2
2
Structure 2 is of particular interest, since supramolecular
helical strands paired through hydrogen bonds, to our know-
ledge, have never been described in the literature. In order to
determine whether molecules 1È3 are intrinsically pre-
organized for incorporation of the guest species, we performed
conformational sampling using the MonteÈCarlo method
coupled with molecular mechanics calculations.
2
2
2
2
S(CH CH NHCH CH È) or HN(CH CH SCH È) spacers
2
2
2
2 2
2
2
2 2
has been studied in solution by NMR and UVÈVis spectro-
scopies, and by mass spectroscopic techniques.10
This article is devoted to the synthesis as well as experi-
mental and theoretical structural studies of three new mole-
Results and discussion
cular tweezers, 1È3 (Scheme 1), containing
a Ñexible
O[CH CH OCH C(O)NHÈ] spacer and two phenyl (1), 3,5-
Compounds 1È3 were obtained in good yields using the clas-
sical condensation between acid chlorides and amines. The
amide groups in 1È3 are all in the typical trans conformation
suitable to give intra- and intermolecular hydrogen bonds
with oxygens of the polyether spacer and with co-crystallized
water molecules. The ligand-to-water ratio varies as a function
of the nature of the terminal group of the tweezers; it is equal
to 1 : 2 in 1, 1 : 1 in 2 and 2 : 1 in 3. The observed ratios are
related to the variation in size of the aromatic groups and to
the modiÐcation of their electronic factors due to di†erent
substituents.9,14 All water molecules are involved in hydrogen
bonds and the three compounds present clear-cut structural
di†erences.
2
2
2
2
dinitrophenyl (2) or 3,5-dimethylisophthalate (3) terminal
units. Unlike sulfur-containing tweezers studied earlier, mol-
Scheme 1
DOI: 10.1039/b001127o
New J. Chem., 2000, 24, 371È376
371
This journal is ( The Royal Society of Chemistry and the Centre National de la Recherche ScientiÐque 2000

View Article Online
The di†raction study shows that in 1 É 2H O the ligand 1
2
adopts a tweezers-like conformation, unfortunately the two
phenyl rings are not stacked, their planes are turned by
59.8(1)¡ with regard to one another. This corroborates obser-
vations made elsewhere.9,14 The heteroatoms of 1 surround
the Ðrst water molecule O1w, whereas O2w links together
[O1w \ 1] units. Molecule O1w is held inside 1 through three
hydrogen bonds, involving the two amide NH and one ether
O: O1wÉ É ÉN1, O1wÉ É ÉN2 and O1wÉ É ÉO3 are equal to
3.036(2), 3.004(2) and 2.954(2) A, respectively. Owing to these
hydrogen bonds, the carbonyl groups are in an exoÈexo
orientation and are available for interaction with the second
water molecule O2w (Fig. 1). O2w forms strong hydrogen
bonds both with O1w and with two carbonyl oxygens,
each from centrosymmetrically equivalent molecules:
O2wÉ É ÉO1w \ 2.724(2),
O2wÉ É ÉO1 \ 2.773(2)
and
O2wÉ É ÉO5 \ 2.782(2) A. Thus, the [O1w \ 1] units are linked
together by O2w, which plays a key role in this two-
component self-assembly.15h18 This results in the formation of
a molecular tape best formulated as M[H O \ 1] É H ON [Fig.
2(A)]. The tapes are disposed in layers shifted by the value c/2.
In the successive layers, the tapes are alternately all oriented
in either the [110] or the [110] direction. This structure can
be considered as a model of a lamellar double layer system.19
The phenyl groups of a tape are turned outwards to produce a
hydrophobic rim, whereas spacers and water molecules are in
hydrophilic association. The membrane-like structures are
packed along the c axis [Fig. 2(B)]. Weak CHÉ É Ép20 and
CHÉ É ÉO21 interactions within each tape and between tapes
stabilize the self-assembly.
Fig. 2 (A) ORTEP view of the molecular tape M[H O \ 1] É H ON
n
2
2
n
2
2
showing four units. The ellipsoids of the water O atoms are represent-
ed with octant shading. Carbons and hydrogens are depicted as small
circles of arbitrary radius. (B) Partial crystal packing with three tapes
of four units each along the a axis showing the membranar system
displayed in 1 É 2H O. The water O atoms (discrete circles) appear
2
inside and between the ligands. Hydrogen atoms are omitted.
through oxygens of the nitro groups [O13É É ÉO8 \ 2.847(4)
A]. This molecular juxtaposition draws inÐnite helices linked
by pairs via hydrogen bonds (Fig. 4). Each strand of a pair is
obtained from the other by inversion. Since the two strands
are not interweaved, we propose to designate it as a ““pseudo-
In the crystal structure of 2 water also acts as the cement.
The water molecule in [2 É H O] forms three hydrogen bonds,
2
with one ether oxygen, one NH group, and a carbonyl oxygen
from an equivalent of
[OwÉ É ÉO3 \ 2.836(3), OwÉ É ÉN2 \ 3.074(3),
2.985(3) A]. Thus, a [2 É H O] dimer is formed; it is stabilized
2
obtained by inversion
OwÉ É ÉO1 \
2
2
by six hydrogen bonds. The hydrogen bonds as well as inter-
molecular interactions induce a helical conformation of 2. The
two individual molecules of the dimer constitute two complete
and independent loops, that is an elementary step of a helix;
one is left-handed, the other right-handed (Fig. 3). The two
dinitrophenyl groups of each loop appear here almost face-to-
face; they are tilted with a dihedral angle of 26.7(1)¡. The
packing of successive [2 É H O] dimeric units exhibits inter-
2
2
esting features. Each loop is in tight contact with its neigh-
bour along the a axis. The successive loops are in contact
Fig. 3 Top view of the centrosymmetric [H O \ 2] unit showing
2
2
the helical conformation of 2 and the intermolecular hydrogen bond
network with the heteroatoms labeled. Drawing parameters are
similar to those in Fig. 1 with the ellipsoids of the water O atoms
represented with octant shading.
Fig. 1 ORTEP view of 1 É 2H O showing the labelling of the non-
2
hydrogen atoms; thermal ellipsoids are drawn at the 50% probability
Fig. 4 Stereoview of the pseudo ““double helixÏÏ. Each strand is rep-
resented by three successive molecules translated along the a axis.
Hydrogen atoms are omitted.
level; carbons and hydrogens are depicted as small circles of arbitrary
radius; intermolecular hydrogen bonds as dashed lines.
372
New J. Chem., 2000, 24, 371È376

View Article Online
Fig. 5 ORTEP view of a [3] É H O entity with the hydrogen bonds
2
2
between the water molecule and the heteroatoms as dashed lines.
Drawing parameters are as in Fig. 1 and 3.
double helixÏÏ. Theobserved assembly is stabilized by intra-
and interstrand forces of the CHÉ É ÉO type.21
The asymmetric unit of 3 contains one water and two
ligand molecules. Both ligands are approximately sym-
metry-related. They are held together in a back-to-back
fashion by the water owing to three hydrogen bonds:
OwÉ É ÉO4 \ 2.777(4),
OwÉ É ÉO15 \ 2.832(4)
and
OwÉ É ÉN4 \ 2.846(4) A (Fig. 5). The two ligands of the
[3] É H O entity exhibit the expected tweezers-like conÐgu-
2
2
ration with rather strained spacers. The observed values of the
intramolecular NÉ É ÉN distances are smallest in [3] É H O,
2
2
4.132(4) and 3.621(4) A compared to 5.508(2) A in M[H O \
2
1] É H ON and 5.546(4) A in [2 É H O]. The amide groups are
2
n
2
in a typical trans conformation as in 1 and 2. The planes of
the four terminal aromatic groups are all nearly parallel with
interplanar angles between 1.2 and 5.6¡. For each ligand, the
distance between the planes of the aromatic fragments is
almost identical: 3.481(3) and 3.401(3) A, the aromatic moi-
eties being shifted with regard to one another. The di†erent
[3] É H O entities are linked through hydrogen bonds
2
2
(NHÉ É ÉO, CHÉ É ÉO and CHÉ É ÉN) and CHÉ É Ép inter-
actions.9,20,21 This bonding network results in linear aggre-
gates consisting of stair-like packed units (Fig. 6).
Molecules 1, 2 and 3 di†er simply in that the meta positions
on the aromatic end groups are occupied by either two hydro-
gens, two nitro groups or two methylcarboxylate groups. As
the bulkiness of the aromatic groups increases, the number of
water molecules present decreases. No water molecule is com-
plexed by 3, the water molecules simply link pairs of ligands.
This allows o†set face-to-face p-stacking interactions. In the
other two compounds, water is each time complexed by the
ligand; the conformations of 1 and 2 are stabilized by elec-
Fig. 7 Lowest-energy conformations of 1, 2 and 3 (from top to
bottom) obtained in a MonteÈCarlo conformational search.
tronic factors due to the substituents on the aromatic systems,
strong hydrogen bonds including the water molecules and, in
the case of 1, CHÉ É Ép interactions. The packing in [2 É H O]
2
displays an original helical self-assembly that, to our know-
ledge, has never been reported so far.22 It di†ers from the
helical structures found in helicates, where strands are
assembled by metal ion complexation with suitable ligands,
and from double helices formed by diols and pyridine deriv-
atives.23h29 Nonchiral linear molecules tend to form helical
structures but not extended arrays.30 So far only a few helical
arrays promoted by neutral substrates have been structurally
characterized.31h33
From the structures of molecules 1È3 in the solid state it is
not clear whether they were initially pre-organized or became
““tweezersÏÏ only under the inÑuence of a guest. To shed light
on the conformational behaviour of the studied molecules, a
MonteÈCarlo conformational search has been performed on
Fig. 6 View of two adjacent [3] É H O entities showing the p-
2
2
stacking. The two entities are linked through the OÉ É ÉHN hydrogen
bond [2.969(4) A] shown as a dashed line at the center of the drawing.
New J. Chem., 2000, 24, 371È376
373

View Article Online
uncomplexed 1È3 molecules using the AMBER* force Ðeld
incorporated in the MacroModel 5.5 program.34 In these cal-
culations, the program generates, for a given molecule, a
number of di†erent conformers (1000 by default), whose ener-
gies are then minimized in molecular mechanics calculations.
In such a way, for each molecule, we have observed a number
of low energy conformers stabilized by intramolecular
carbonyl-OÉ É ÉHÈN and/or ether-OÉ É ÉHÈN hydrogen bonds,
and having di†erent ““in-outÏÏ orientations of amide groups
and conformations of the polyether spacer. The lowest energy
structures of 1È3 have pseudocavities suitable for encapsula-
tion of the guest species, i.e. these molecules are intrinsically
pre-organized as tweezers. Mutual orientation of the two ter-
minal aromatic fragments is similar to that found experimen-
tally for the solid state structures. Thus, the two phenyl
groups in 1 are well separated both in the solid state (Figs. 1
and 2) and in vacuo (Fig. 7). The most stable gas phase con-
formers of 2 and 3 display a pseudo-stacking of their terminal
groups, as in the X-ray structures: the planes of the aromatic
fragments are almost parallel and shifted one with respect to
other (Fig. 7). Thus, the intrinsic conformational properties of
1È3 are an important factor governing their ““tweezersÏÏ behav-
iour in the complexes with cationic or neutral guests.
tures were solved by direct methods using the MOLEN
package35 for 1, the SDP-VAX (EnrafÈNonius) program
system35 for 2 and 3. They were reÐned by full-matrix least-
squares on F with anisotropic displacement parameters for
the non-H atoms; the minimized function was &w( o F o
0
[ o F o )2. Neutral atom scattering factors were taken from the
c
usual source,36 and the e†ects of anomalous dispersion were
included in F .36
c
Calculations on the free molecules 1–3 in vacuo were per-
formed using the AMBER* force Ðeld incorporated in the
MacroModel 5.5 program.34 The most stable conformers of
1–3 were obtained in a 1000 step MonteÈCarlo conforma-
tional search. In order to ascertain the force Ðeld e†ects on the
conformational equilibrium of studied molecules, the MonteÈ
Carlo calculations on molecule
2 were repeated using
AMBER* coupled with electrostatic potential atomic charges
(ESP charges) calculated ab initio (6-31G*) for the
(NO ) C H NHC(O)CH OCH fragment.
2 2 6
3
2
3
General synthetic procedures
1–3 were obtained by a straightforward synthesis involving
the condensation of the appropriate aromatic amines with
tetraglycolic acid dichloride. 3,6,9-Trioxaundecanedioic acid
(tetraglycolic acid purchased from Fluka was puriÐed as
described elsewhere37) was used as the starting chemical to
prepare the three compounds. It was Ðrst converted in its
dichloride derivative. Condensation of the dichloride with the
appropriate amine in a stoichiometric amount in the presence
of K CO to capture the evolving HCl led to the desired pro-
Conclusion
Three di†erently functionalized variants of potential tweezers
have been studied. These molecules form two-component self-
assembled superstructures in the solid state. The process is
driven by the coordination of water molecules and the stack-
ing of the aromatic fragments. Theoretical calculations show
that interactions between two terminal aromatic groups in
uncomplexed tweezers is an important factor a†ecting their
conformational behaviour in complexes with neutral guests.
No stacking is observed for 1, either in the gas phase or in the
2
3
ducts.
The synthesis of the dichloride was conducted in the dark
and under argon: a solution of oxalyl chloride (27.4 g, 0.2
mol) in benzene (50 mL) was added to a suspension of 3,6,9-
trioxaundecanedioic acid (19.5 g, 90 mmol) in benzene (130
mL) with pyridine (4 drops). The mixture was stirred at room
temperature for 20 h. The pale yellow solution of the dichlo-
ride was then quickly Ðltered over celite and the Ðltrate
reduced under vacuum. The yellow oil (even below [78 ¡C)
obtained was used without further puriÐcation. 1H NMR (200
MHz, CDCl ): d 3.72 (A X , 8H, OCH CH O), 4.50 (s, 4H,
solid state.
A membrane-type assembly is observed in
M[H O \ 1] É H ON . Free molecules 2 and 3, for which
2
2
n
strong attractive interactions between the two terminal groups
are observed in vacuo, display stacking e†ects in their com-
plexes with water in the solid state. Both 1 and 2 exhibit a
helical conformation due to the presence of a water molecule
in their hydrophilic cavity; this results in formation of inÐnite
helical arrays in 2. Appropriate choice of substituents in the
aromatic fragments may lead to di†erent helical supramolecu-
lar species. Studies of compounds obtained by hydrolysis of
the ester functions of 3 are, therefore, under way.
3
2 2
2
2
OCH CO).
2
N,Nº-Bisphenyl-3,6,9-trioxaundecanedicarboxamide (1).
1
was obtained as a colourless crystalline solid during puriÐ-
cation of the tetraglycolic acid. 1H NMR (200 MHz, CDCl ):
3
d 3.79 (A B , 8H, OCH CH O), 4.08 (s, 4H, OCH CO), 7.07È
2 2
2
2
2
7.54 [m, 10H, ArH: 7.07È7.15 (m, 2H); 7.27È7.34 (m, 4H);
7.48È7.54 (m, 4H)], 8.55 (s, 2H, NH); IR (KBr): l 3384 (NÈH),
Experimental
1654 (C2O) cm~1; elem. anal. for
C
H
N O É 2H O
All reactions were carried out under argon. The solvents were
freshly distilled, benzene from sodium, diethyl ether and THF
from sodiumÈbenzophenone. Other chemicals were of reagent
grade and used without further puriÐcation, unless otherwise
indicated. 1H and 13C NMR spectra were recorded at
ambient temperature on either Bruker WP200 or AC200
spectrometers using the solvent as an internal standard. IR
spectra were recorded on a Bruker IFS25 spectrometer. Mass
spectra were obtained by the fast atom bombardment (FAB)
method; nitrobenzyl alcohol was used as the matrix. Column
chromatography was performed on Merck silica 60 (particle
size 0.040È0.063 or 0.063È0.200 mm). Elemental analyses were
performed by the Service de Microanalyse de lÏInstitut de
Chimie de Strasbourg.
20 24
2
5
2
(408.46): calcd C 58.81, H 6.91, N 6.86; found C 59.07, H 6.66,
N 6.73%.
N,Nº-Bis(3,5-dinitrophenyl)-3,6,9-trioxaundecanedicar-
boxamide (2). Under an argon atmosphere 3,5-dinitroaniline
(4.58 g, 25 mmol) and K CO (3.59 g, 26 mmol) were mixed in
2
3
diethyl ether (250 mL); then
a solution of 3,6,9-tri-
oxaundecanedioic acid dichloride (3.37 g, 13 mmol) in diethyl
ether (100 mL) was added dropwise. The mixture was stirred
at room temperature for 60 h. The resulting yellow solid was
Ðltered, washed successively with diethyl ether and water,
before being dried under vacuum. 2 was obtained as a yellow
solid (3.2 g, 45%) after puriÐcation by column chromatog-
raphy (eluent CH Cl ÈCH OH gradient 100 : 0 until
X-Ray structure analyses were recorded on a Philips
PW1100/16 di†ractometer with Cu-Ka radiation (graphite
monochromator, j \ 1.541 84 A) at 173(2) K for 1, and on an
EnrafÈNonius CAD-4 di†ractometer, graphite monochro-
mated Cu-Ka radiation at 294(2) K for 2 and 3. The struc-
2
2
3
98.5 : 1.5). 1H NMR (200 MHz, DMSO-d ): d 3.70 (A B , 8H,
2 2
OCH CH O), 4.19 (s, 4H, OCH CO), 8.47 (t, 2H, ArH,
6
2
2
2
J \ 2.1 Hz), 8.93 (d, 4H, ArH, J \ 2.1 Hz), 11.30 (s br, 2H,
NH); 13C NMR (50 MHz, DMSO-d ): d 69.62 (CH ), 70.14
6
2
374
New J. Chem., 2000, 24, 371È376

View Article Online
2
S. C. Zimmerman, Z. Zeng, W. Wu and D. E. Reichert, J. Am.
Chem. Soc., 1991, 113, 183 and references therein; S. C. Zimmer-
man, W. Wu and Z. Zeng, ibid., 1991, 113, 196; S. C. Zimmerman
and W. Wu, ibid., 1989, 111, 8054; S. C. Zimmerman, M. Mrksich
and M. Baloga, ibid., 1989, 111, 8528; R. Shimazawa, Y. Hash-
imoto and S. Iwasaki, T etrahedron L ett., 1992, 33, 7197.
J. P. Fillers, K. G. Ravichandran, A. Abdalmuhdi, A. Tulinsky
and C. K. Chang, J. Am. Chem. Soc., 1986, 108, 417.
(CH ), 70.31 (CH ), 112.46 (2 ArCH), 118.93 (4 ArCH), 140.46
2
2
(2 ArC), 148.01 (4 ArC), 169.80 (CH CO); IR (KBr) l \ 3434,
2
3311 (NÈH), 1696 (C2O), 1540, 1345 (NO ) cm~1; MS (FAB):
2
m/z 553.0 [M ] H]` (552.1 calcd for C
H
N O ); elem.
20 20
6
13
anal. for C
H
N O É H O (570.43): calcd C 42.11, H 3.89,
20 20
6
13
2
N 14.73; found C 42.04, H 3.81, N 14.58%.
3
4
5
6
M. J. Gunter, M. R. Johnston, B. W. Skelton and A. H. White, J.
Chem. Soc., Perkin T rans. 1, 1994, 1009.
N,Nº-Bis(dimethylisophthalate)-3,6,9-trioxaundecanedicar-
boxamide (3). Dropwise addition of 3,6,9-trioxaundecanedioic
acid dichloride (7.38 g, 28 mmol) in THF (100 mL) to 5-
aminoisophthalic acid dimethyl ester (12.05 g, 57.6 mmol) and
K CO (8.31 g, 60 mmol) in THF (200 mL) gives 3 (5.1 g,
Y. Agnus, M. Gross, M. Labarelle, R. Louis and B. Metz, J.
Chem. Soc., Chem. Commun., 1994, 939.
S. C. Zimmerman, in Bioorganic Chemistry Frontiers, Springer,
Berlin, 1991, vol. 2, 33È71; S. C. Zimmerman, T op. Curr. Chem.,
1993, 165, 71; S. C. Zimmerman, K. W. Saionz and Z. Zeng,
Proc. Natl. Acad. Sci. USA, 1993, 90, 1190.
2
3
30%) as a beige solid having no accurate melting point. 1H
NMR (200 MHz, DMSO-d ):
OCH CH O), 3.87 (s, 12H, OCH ), 4.11 (s, 4H, OCH CO),
8.10 (t, 2H, ArH, J \ 1.5 Hz), 8.45 (d, 4H, ArH, J \ 1.5 Hz),
10.04 (s br, 2H, NH); IR (KBr) l 3313 (NÈH), 1727 (C2O)
cm~1; MS (FAB): m/z 605.1 [M ] H]` (604.2 calcd for
d
3.70 (A B , 8H,
7
J. Rebek, Jr., Angew. Chem. , 1990, 102, 261; Angew. Chem., Int.
Ed. Engl., 1990, 29, 245; R. Guther, M. Nieger and F. Vogtle,
Angew. Chem., 1993, 105, 647; Angew. Chem., Int. Ed. Engl., 1993,
32, 601; M. Harmata, C. L. Barnes, S. R. Karra and S. Elahmad,
J. Am. Chem. Soc., 1994, 116, 8392; A. Lorente, M.
FernandezÈSaiz, J. F. Espinosa, C. Jaime, J. M. Lehn and J. P.
Vigneron, T etrahedron L ett., 1995, 36, 5261; L. J. DÏSouza and
U. Maitra, J. Org. Chem., 1996, 61, 9494.
6
2 2
2
2
3
2
C
H
N O ); elem. anal. for 2C
H
N O É H O
28 32
2
13
28 32
2
13
2
(1227.16): calcd C 54.81, H 5.42, N 4.57; found C 55.44, H
5.54, N 4.42.
8
9
T. Schrader, Chem. Eur. J., 1997, 3, 1537.
F. Cozzi and J. S. Siegel, Pure Appl. Chem., 1995, 67, 683; K.
Miyamura, A. Mihara, T. Fujii, Y. Gohshi and Y. Ishii, J. Am.
Chem. Soc., 1995, 117, 2377; A. S. Shetty, J. Zhang and J. S.
Moore, J. Am. Chem. Soc., 1996, 1181019.
X-Ray structure analyses
1 É 2H O. Colourless prisms, monoclinic, P2 /c, (C5 ) (no. 14),
10 S. Meyer, Ph.D. Dissertation, Universite Louis Pasteur, Stras-
bourg, 1996.
2
1
2h
a \ 11.726(3), b \ 8.518(3), c \ 20.943(6) A, b \ 91.31(2)¡,
U \ 2091(2) AŽ 3, Z \ 4, k(Cu-Ka) \ 7.81 cm~1. All hydrogen
11 M. C. Etter, Acc. Chem. Res., 1990, 23, 120; J. Bernstein, R. E.
Davis, L. Shimoni and N.-L. Chang, Angew. Chem., 1995, 107,
1687; Angew. Chem., Int. Ed. Engl., 1995, 34, 1555; S. Sub-
ramanian and M. J. Zaworotko, Coord. Chem. Rev., 1994, 137,
357; J. P. Glusker, T op. Curr. Chem., 1998, 198, 1; A. Nangia and
G. R. Desiraju, T op. Curr. Chem., 1998, 198, 57; R. E. Melendez
and A. D. Hamilton, T op. Curr. Chem., 1998, 198, 97.
12 G. R. Desiraju, J. Chem. Soc., Chem. Commun., 1991, 426; T. M.
Krygowski, S. J. Grabowski and J. Konarski, T etrahedron, 1998,
11311.
13 R. Parthasarathy, S. Chaturvedi and K. Go, Proc. Natl. Acad.
Sci. USA, 1990, 87, 871; K. R. Rajashankar, S. Ramakumar,
R. M. Jain and V. S. Chauhan, J. Am. Chem. Soc., 1995, 117,
11773.
14 G. R. Desiraju, Chem. Commun., 1997, 1475; G. R. Desiraju,
Angew. Chem., 1995, 107, 2541; Angew. Chem., Int. Ed. Engl.,
1995, 34, 2311; G. R. Desiraju and A. Gavezzotti, J. Chem. Soc.,
Chem. Commun., 1989, 621.
15 F. Vogtle, in Supramolecular Chemistry, Wiley, Chichester, 1991;
J.-M. Lehn, in Supramolecular Chemistry, VCH, Weinheim, 1995;
G. M. Whitesides, E. E. Simanek, J. P. Mathias, C. T. Seto, D. N.
Chin, M. Mammen and D. M. Gordon, Acc. Chem. Res., 1995,
28, 37; C. B. Aakeroy, M. Nieuwenhuyzen and S. L. Price, J. Am.
Chem. Soc., 1998, 120, 8986; V. R. Pedireddi, A. Ranganathan
and S. Chatterjee, T etrahedron L ett., 1998, 39, 9831.
16 D. S. Lawrence, T. Jiang and M. Levett, Chem. Rev., 1995, 95,
2229.
17 Y.-L. Chang, M.-A. West, F. W. Fowler and J. W. Lauher, J. Am.
atoms were localized and introduced as Ðxed contributions
with isotropic thermal parameters set to 1.3 times those of the
atoms to which they were bonded. R \ 0.034, Rw \ 0.047, for
2111 observed reÑections (F2 [ 3p(F2)). The weighting scheme
0
0
was deÐned by the Killean and Lawrence method with terms
of 0.02 and 3.0.38
2 É H O. Pale yellow prisms, monoclinic, P2 /c, (C5 )
2
1
2h
(no. 14), a \ 7.994(1), b \ 21.670(3), c \ 14.741(3) A,
b \ 101.91(1)¡, U \ 2499(1)
AŽ 3, Z \ 4, k(Cu-Ka) \ 10.88
cm~1. All hydrogen atoms were located on di†erence Fourier
syntheses maps and included as Ðxed contributions with iso-
tropic thermal parameters 1.3 times those of the atoms to
which they were bonded. Anisotropic temperature factors for
all non-hydrogen atoms; R \ 0.049, Rw \ 0.045, for 3267
reÑections (F2 [ 3p(F2)).
0
0
3 É 0.5H O. Pale yellow prisms, triclinic, P1, (C1) (no. 2),
2
i
a \ 11.318(2), b \ 24.444(5), c \ 11.069(1) A, a \ 96.17(1),
b \ 101.24(1), c \ 77.23(2)¡; U \ 2923(1) A
Ž
3, Z \ 2, asym-
metric unit formula 2 (C
H
N O ) É H O, k(Cu-Ka) \ 9.12
28 32
2
13
2
cm~1. The Killean and Lawrence method with terms of 0.02
and 0.4 was used to deÐne the weights.38 Final R \ 0.052,
Rw \ 0.059, for 6597 reÑections (F2 [ 3p(F2)). Anisotropic
temperature factors were used for all non-hydrogen atoms.
Hydrogen atom treatment: included in di†erence map or cal-
0
0
Chem. Soc., 1993, 115, 5991.
culated positions (d
showed a large thermal motion. This was treated as a disorder
over two alternative positions.
\ 0.95 A). An ether O of one ligand
18 M. C. T. Fyfe and J. F. Stoddart, Acc. Chem. Res., 1997, 30, 393;
D. Philp and J. F. Stoddart, ibid., 1996, 108, 1242; ibid., 1996, 35,
1154; D. B. Amabilino and J. F. Stoddart, Chem. Rev., 1995, 95,
2725.
19 H. Ringsdorf, B. Schlarb and J. Venzmer, Angew. Chem., 1988,
100, 117; Angew. Chem., Int. Ed. Engl., 1988, 27, 113; R. B.
Gennis, in Biomembranes: Molecular Structure and Function,
SpringerÈVerlag, New York, 1989; T. Dewa, S. J. Vigmond and
S. L. Regen, J. Am. Chem. Soc., 1996, 118, 3435.
20 Y. Umezawa, S. Tsuboyama, K. Honda, J. Uzawa and M. Nishio,
Bull. Chem. Soc. Jpn., 1998, 71, 1207.
ChH
CCDC reference number 440/177. See http://www.rsc.org/
suppdata/nj/b0/b001127o/ for crystallographic Ðles in .cif
format.
Acknowledgements
21 G. R. Desiraju, Acc. Chem. Res., 1996, 29, 441; C. V.
KrishnamohanÈSharma and M. J. Zaworotko, Chem. Commun.,
1996, 2655; T. Steiner, Chem. Commun., 1997, 727; I. Berger and
M. Egli, Chem. Eur. J., 1997, 3, 1400; S. G. Bodige, R. D. Rogers
and S. C. Blackstock, Chem. Commun., 1997, 1669; K. N. Houk,
S. Mentzer, S. P. Newton, F. M. Raymo, J. F. Stoddart and D. J.
Williams, J. Am. Chem. Soc., 1999, 121, 1479; G. R. Desiraju and
T. Steiner, in T he W eak Hydrogen Bond in Structural Chemistry
and Biology, Oxford University Press, Oxford, 1999.
S.M. is grateful to the Centre National de la Recherche Scien-
tiÐque (CNRS) and the Region Alsace for a PhD fellowship.
We thank Dr. D. Moras and Professor J. Fischer for the use
of their X-ray facilities.
References
1
C.-W. Chen and H. W. Whitlock, J. Am. Chem. Soc., 1978, 100,
4921.
22 J. R. Fredericks and A. D. Hamilton, in Comprehensive Supramo-
lecular Chemistry, ed. J. L. Atwood, J. E. D. Davies, D. D. Mac-
New J. Chem., 2000, 24, 371È376
375

View Article Online
Nicol, F. Vogtle and K. S. Suslick, Pergamon, Oxford, 1996, vol.
9, pp. 565È594; G. A. Je†rey, in An Introduction to Hydrogen
Bonding, Oxford University Press, Oxford, 1997.
31 S. J. Geib, C. Vicent, E. Fan and A. D. Hamilton, Angew. Chem.,
1993, 105, 83; Angew. Chem., Int. Ed. Engl., 1993, 32, 119.
32 S. Hanessian, A. Gomtsyan, M. Simard and S. Roelens, J. Am.
Chem. Soc., 1994, 116, 4495; S. Hanessian, M. Simard and S.
Roelens, ibid., 1995, 117, 7630.
23 R. Bishop, in Comprehensive Supramolecular Chemistry, ed. J. L.
Atwood, J. E. D. Davies, D. D. MacNicol, F. Vogtle and K. S.
Suslick, Pergamon, Oxford, 1996, vol. 6, pp. 85È115; R. Bishop
and I. G. Dance, in Inclusion Compounds, ed. J. L. Atwood, J. E.
D. Davies and D. D. MacNicol, Oxford Chemistry Press, Oxford,
1991, vol. 4, pp. 1È26.
24 E. C. Constable, in Comprehensive Supramolecular Chemistry, ed.
J. L. Atwood, J. E. D. Davies, D. D. MacNicol, F. Vogtle and K.
S. Suslick, Pergamon, Oxford, 1996, vol. 9, pp. 213È252.
25 R. D. Rogers and C. B. Bauer, in Comprehensive Supramolecular
Chemistry, ed. J. L. Atwood, J. E. D. Davies, D. D. MacNicol, F.
Vogtle and K. S. Suslick, Pergamon, Oxford, 1996, vol. 1, pp.
315È355.
26 J. M. Lehn, A. Rigault, J. Siegel, J. HarrowÐeld, B. Chevrier and
D. Moras, Proc. Natl. Acad. Sci. USA, 1987, 84, 2565.
27 A. Williams, Chem. Eur. J., 1997, 3, 15.
28 B. Hasenknopf, J. M. Lehn, B. O. Kneisel, G. Baum and D.
Fenske, Angew. Chem., 1996, 108, 1987; Angew. Chem., Int. Ed.
Engl., 1996, 35, 1838.
29 A. E. Rowan and R. J. M. Nolte, Angew. Chem., 1998, 110, 65;
Angew. Chem., Int. Ed. Engl., 1998, 37, 63.
33 T. GulikÈKrzywicki, C. Fouquey and J. M. Lehn, Proc. Natl.
Acad. Sci. USA, 1993, 90, 163.
34 W. C. Still, MacroModel v.5.5, Columbia University, New York,
1996; F. Mohamadi, N. G. J. Richards, W. C. Guida, R. Liskamp,
M. Lipton, C. CauÐeld, G. Chang, T. Henrickson and W. C. Still,
J. Comput. Chem., 1990, 11, 440.
35 MOL EN, An Interactive Structure Solution Procedure, EnrafÈ
Nonius, Delft, The Netherlands, 1990; SDP-Plus Structure Deter-
mination Package, B. A. Frenz & Associates Inc., College Station,
TX, USA and EnrafÈNonius, Delft, The Netherlands, 1983.
36 D. T. Cromer and J. T. Waber, in International T ables for X-Ray
Crystallography, The Kynoch Press, Birmingham, UK, 1974, vol.
IV, Table 2.2B; D. T. Cromer, ibid., Table 2.3.1.
37 B. Dietrich, J. M. Lehn, J. P. Sauvage and J. Blanzat, T etra-
hedron, 1973, 29, 1629.
38 R. C. G Killean and J. L. Lawrence, Acta Crystallogr., Sect. B,
1969, 25, 1750.
30 D. M. Bassani, J.-M. Lehn, G. Baum and D. Fenske, Angew.
Chem., 1997, 109, 1931; Angew. Chem., Int. Ed. Engl., 1997, 36,
1845.
376
New J. Chem., 2000, 24, 371È376