Synthesis, topology and energy analysis of crystalline resorcinol-based oligophenylene molecules with various symmetries

Article abstract of DOI:10.1039/c3ce40761f

We describe the development of a set of highly symmetric multitopic oligophenylene molecules decorated with hydroxyl functions that are all derived from the resorcinol moiety. All these resorcinol-based oligophenylene self-assembled structures and the corresponding methoxy protected precursors were found to be highly crystalline materials, with two compounds giving rise to porous 3D-networks. The solid-state organisation of these molecules has been studied from three complementary viewpoints using metrical, topological and energy analyses. A quantitative interaction energy has been associated to each supramolecular interaction responsible for a given topology, even for the quite new and highly complex topologies evidenced. Thermal and luminescent properties of these materials have also been examined.

Full text of DOI:10.1039/c3ce40761f

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Synthesis, topology and energy analysis of crystalline
resorcinol-based oligophenylene molecules with
various symmetries3
Cite this: CrystEngComm, 2013, 15,
6845
a
a
b
a
´
Clement Chaumont, Pierre Mobian,* Nathalie Kyritsakas and Marc Henry*
We describe the development of a set of highly symmetric multitopic oligophenylene molecules decorated
with hydroxyl functions that are all derived from the resorcinol moiety. All these resorcinol-based
oligophenylene self-assembled structures and the corresponding methoxy protected precursors were
found to be highly crystalline materials, with two compounds giving rise to porous 3D-networks. The solid-
state organisation of these molecules has been studied from three complementary viewpoints using
metrical, topological and energy analyses. A quantitative interaction energy has been associated to each
supramolecular interaction responsible for a given topology, even for the quite new and highly complex
topologies evidenced. Thermal and luminescent properties of these materials have also been examined.
Received 30th April 2013,
Accepted 6th June 2013
DOI: 10.1039/c3ce40761f
www.rsc.org/crystengcomm
shown that the topology and the porosity of MOF systems are
strongly influenced by the geometry and the size, respectively,
Introduction
of a given type of ligand.11 Thereby, developing a novel family
of connectors based on identical coordinating entities that are
able to generate a library of compounds showing a high
diversity in terms of symmetry and size is of fundamental
importance.
In the field of materials science, crystalline porous coordina-
tion polymers occupy a particular place owing to their high
potentialities in separation,1 gas storage,2 drug delivery,3
catalysis,4 or magnetism.5 These Metal–Organic Frameworks
(MOFs) are formed from metal ions or clusters connected with
organic linkers. Focusing only on the role of these organic
connectors, the major importance played by the ligand fine
design to provide to the resulting networks structural rigidity
and high porosity is well established. As a consequence, the
very large and structurally diverse family of oligophenylene
connectors have been shown to be particularly adapted to
generate porous networks in the presence of metal ions.6
Thereby, several families of oligophenylene ligands, depend-
ing on the nature of the coordinating groups that functionalise
the rigid backbones, have been reported. These connectors are
mainly dominated by molecules that incorporate rigid
oligophenylene backbones bearing carboxylic acid,7 phospho-
nic acid,8 cyanide9 or N-heterocyclic groups.10 Besides the
chemical nature of the groups attached to the rigid spacers,
other factors linked to the ligands structural features have to
be considered in order to predict, to govern or to understand
the resulting MOF structure. For instance, within a specific
class of ligands, by using the same inorganic node, it has been
In order to propose an alternative class of ligands to the
existing systems that are able to form MOFs with oxophilic
metals, we describe herein the development of a set of
multitopic oligophenylene molecules decorated with hydroxyl
functions and all derived from the resorcinol moiety. The
choice of the resorcinol unit for creating a new family of
oligophenylene connectors was motivated by the ideal 1,3
position of the hydroxyl functions on the phenyl ring to form
extended networks in the presence of oxophilic metal ions.12
So, we establish here efficient synthetic protocols leading to
linear and branched polytopic oligophenylene connectors
displaying various symmetries and having, as a common
feature, terminal resorcinol units. The members of this family
are depicted in Fig. 1. Since a majority of ligands in the field of
MOF chemistry are highly symmetrical compounds, we have
chosen to report the preparation of highly symmetric
molecules belonging to the D2h, C2v, D3h and Td group-points.
The targeted resorcinol-based oligophenylene structures and
the corresponding methoxy protected precursors were found
to be highly crystalline materials and a particular focus has
been devoted to understand their solid-state organisation from
three complementary viewpoints:
a
´
´
Laboratoire de Chimie Moleculaire de l’Etat Solide, UMR 7140, Universite de
Strasbourg, 67070 Strasbourg, France. E-mail: mobian@unistra.fr; henry@unistra.fr
b
´
Laboratoire de Chimie de Coordination Organique, UMR 7140, Universite de
Strasbourg, 67070 Strasbourg, France
(i) A local metrical analysis performed by looking at bond
lengths and bond angles for both intramolecular and inter-
molecular interactions.
CCDC 934375–934378, 934380–934382, 934386 and 934387. For
3
crystallographic data in CIF or other electronic format see DOI: 10.1039/
c3ce40761f
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could be summarised as follows; the first step concerns the
metallo-catalysed synthesis of the methoxy precursors starting
from commercially or easily available molecules, whereas the
second step deals with the cleavage of the methoxy groups
leading to the target molecules. In most cases, the C–C
formation was conducted by application of Suzuki–Miyaura
reactions in the presence of the ‘‘classical’’ Pd(PPh3)4
catalyst.19 It is worth noticing that compounds (1)20 and (5)21
are already known molecules. However, in the present work,
we improve their accessibility and we characterised their
crystalline solid-state organisations. Table 1 presents the
procedures, the isolated yields and the precursors for the
synthesis of compounds (19) to (69).
The synthesis of our library of compounds started with the
preparation of (19). Several synthetic methods have been
envisaged and tested to obtain (19): the Ullmann coupling, the
Kumada–Corriu coupling or the palladium homo- and hetero-
coupling reactions. The most efficient reaction to isolate (19) is
a homo-condensation of 3,5-dimethoxyphenylboronic acid
mediated by the palladium(II) acetate, which allows the
preparation of (19) in a nearly quantitative yield. However, it
appeared that the Suzuki–Miyaura reaction was the most
applicable method for the synthesis of the other oligopheny-
lene systems. All the target molecules, after a purification step
over silica gel chromatography, were isolated with yields going
from good to excellent. In particular, (69) was obtained in an
80% yield, which is satisfactory if we consider that four C–C
bonds were created in one step.
Next, the cleavage of the methoxy groups was conducted by
using the classical BBr3 reagent in anhydrous dichloro-
methane. In order to isolate the final compounds, two
methods freed from the chromatography techniques were
used. Since the conversions in most cases were quantitative,
an extraction with diethylether of the hydrolysed crude
medium was performed. A second option involved the basic
treatment of the final reaction, followed by an acidification of
the aqueous layer leading to the precipitation of the desired
compounds, which were filtered-off. The deprotected mole-
cules were obtained in yields varying from 93% to quantitative.
Fig. 1 The family of resorcinol-based oligophenylene molecules concerned by
this study.
(ii) A global topological analysis performed using the
TOPOS package13 for determining the volume and mean
radius of spherical domain (Rsd) of the molecular
¨
Voronoı-Dirichlet Polyhedron (MVDP), the coordination num-
bers and the point symbols of the underlying nets for both van
der Waals and/or H-bond interactions. Let’s recall that a point
symbol lists the numbers and sizes of shortest circuits (closed
chains of connected atoms) starting from every angle of every
non-equivalent atom in the net.
(iii) An energetic analysis performed using the PACHA
package14 for retrieving quantitative energy values for all
supramolecular interactions at work in these systems, as well
as molecular dipole moments and packing energies.
A major finding of this systematic study is that two
members were able to self-organise in the solid-state into
porous networks. Furthermore, the thermal and luminescent
properties of these solids have also been examined.
Table 1 Synthetic methodologies leading to the formation of (19–69).
Experimental conditions: A: inert atmosphere, toluene/water/methanol,
Na2CO3, Pd(PPh3)4 (5% mol), reflux; B: methanol, Pd(OAc)2, room temperature,
5 hours; C: inert atmosphere, Mg, Ni(PPh3)2Cl2, tetrahydrofuran, reflux
overnight. Boronic acid/ester precursors: a: 3,5-dimethoxyphenylboronic acid, b:
4,49-biphenylboronic acid bis(neopentyl)ester, c: 1-bromo-3,5-dimethoxyben-
zene, d: 1,4-dibromobenzene, e: 1,3,5-tribromobenzene, f: 1-bromo-4-[tris(4-
bromophenyl)methyl] benzene
Results and discussion
Boronic
acid/ester
precursors
Synthesis
Experimental
conditions
Brominated
precursors
Isolated
yields
Compounds
Several synthetic methodologies have been developed to access
oligophenylene structures; these include, for instance, reduc-
tive and oxidative coupling,15 thermolysis and aromatisation
of appropriate precursors,16 and Diels–Alder cycloaddition.17
Indeed, concerning the selected molecules, the application of
transition-metal-catalysed aryl–aryl coupling reactions18
looked the most adapted. Thus, the simple and straightfor-
ward two steps approach employed in the course of this study
A, 12 hours
B
C
A, 12 hours
A, 4 days
A, 24 hours
A, 12 hours
A, 4 days
a
a
—
a
b
a
c
—
c
d
c
e
95%
98%
75%
82%
90%
88%
90%
80%
19
19
19
29
39
49
59
69
a
a
f
g
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verified for compounds (5) and (6) heated just above the
1
observed exotherms. H NMR and mass spectrometry as well
as infrared analysis indicated that the chemical structures of
(5) and (6) were unaffected by heating the samples at 180 uC
and 280 uC, respectively.
Absorption and emission properties
Oligophenylene structures being known for their emission
properties,22 the absorption and the liquid and solid-state
fluorescence measurements were performed for our series of
derivatives. In general, the spectra are broad and structureless,
with a notable exception concerning the fluorescence of
compounds (3) and (39). Table 2 lists the position of
absorption and emission maxima. In solution, no marked
differences of absorption and emission maxima between the
non-linear derivatives with (1) or (19) are noticed.
Furthermore, for a given member of the methoxy series, the
wavelength absorption and the emission wavelength are highly
comparable to those measured for the corresponding depro-
tected derivatives. A noticeable change of the absorption and
emission properties arises when the number of aromatic rings
increases within the series of linear molecules. For instance, a
bathochromic shift for the absorption (Dl = 42 nm) is observed
when going from (1) to (3). Such a shift to lower energy is a
known common feature for p-oligophenylenes, which corre-
sponds to the increase of the p-system.23 Concerning the
rather structured emission spectra of (3) and (39), it is the
signature of aromatic compounds that display a more planar
configuration in the excited state than in the ground state.24
The solid-state fluorescence spectra are presented in Fig. 3.
In general, for a given compound, the emission occurred at
higher wavelength compared to the solution. Trends similar to
those observed in tetrahydrofuran are found in the solid-state
for the series of linear compounds. A particularly relevant
observation concerns the large difference of emission wave-
length between the two biphenyl derivatives (1) and (19) (Dl #
19 nm), whereas in solution these two molecules exhibit
almost the same emission maxima.
Fig. 2 Dependence of the melting point with the number of aromatic rings (left)
or with the molecular weight (right) for derivatives (19–39) and (59–69).
Thermal stabilities
The methoxy derivatives (19–69) melted over a wide range of
temperatures, between 87 uC and 270 uC, whereas the
deprotected compounds (1–6) melted at above 300 uC
evidencing much stronger intermolecular interactions.
If we except (49), which melts at 87 uC, the melting points of
(19–39) and (59–69) were correlated with the number of aromatic
rings present in the backbone of the molecules (Fig. 2, left). An
analogous tendency is observed if the melting points are
plotted versus the molecular weights (Fig. 2, right).
Independently to the molecular weight or the number of
phenyl rings, the symmetry of the molecules seems also to
influence the solid to liquid phase transition, since an
unexpectedly low melting point for (49) compared to the linear
(29) compound was found. Owing to the quite high melting
points of (1–6), we turned to differential scanning calorimetry
analysis (DSC) to evaluate the thermal properties of this family
of compounds. The measurements were performed from 30 uC
to 450 uC on the as-synthetised powders. The thermograms of
(19–69) showed expected endotherms related to desolvation,
vaporisation or fusion processes. Concerning (1–6), their
thermograms were more complex compared to the protected
derivatives. In particular, the DSC analysis of (5) and (6) clearly
showed two exothermic processes occurring at 170 uC and 280
uC, respectively. As exothermic processes may occur from
decomposition or bond breaking, the chemical integrities were
Table 2 Absorption and emission properties of (19–69) and (1–6) derivatives. (a)
and (b) Solutions (1025 mol L21) in tetrahydrofuran. (b) and (c) Excitation at l =
246 nm
Solid-state
fluorescence(c)
centered
emission
l (nm)
Solution
Absorption(a)
lmax (nm)
fluorescence(b)
lmax (nm)
Compounds
19
29
39
49
59
69
1
2
3
4
5
259
290
301
255
261
266
260
294
302
256
264
267
351
347
375
409
348
360
361
366
394
395
368
364
369
354, 366
356, 373
350
352
351
358
371
373
354
Fig. 3 The superimposed normalized solid-state fluorescence spectra in the –
OMe derivatives (19–69) in (a) and the –OH derivatives (1–6) in (b). Excitation
wavelength l = 246 nm.
352
353
6
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Solid-state structures
Solid-state structures of the linear oligophenylene deriva-
tives (D2h): (19), (29), (39), (1) and (2). The compounds (19), (29)
and (39) are crystalline materials. Suitable single crystals for
X-ray analysis were obtained in each case when n-pentane was
allowed to diffuse in a dichloromethane solution of the
oligophenylene molecule. The molecular structures of 19, 29
and 39 are presented in Fig. 4.
Concerning the conformations adopted by the phenyl rings
in these three systems, one can notice in (19) a synclinal
arrangement of the two phenyl rings (measured torsion angle:
35u). When the molecular size increases, the two terminal
phenyl rings adopt the same parallel orientation to one
another but display a synclinal conformation when two
consecutive phenyl rings are concerned. It is noteworthy that
for (39) the two central aromatic rings are coplanar. At the
supramolecular level, the crystal organisation is driven
essentially by p–p interactions. Compound (19) is self-
organised in staggered parallel bilayers, whereas the crystal
organisation for (29) and (39) results from the repetition of
antiparallel layers, as shown in Fig. 5.
MVDPs have been determined for the two crystallographi-
cally non-equivalent molecules of (19) showing that both
molecules have the same Rsd radius (4.35 Å) and volume
(346 Å3). The complete van der Waals topology corresponds to
a 2-nodal 15,15-connected net with a new yet unknown
topology having the point symbol {339.456.510}2. This shows
that each molecule is in van der Waals contact with 15 other
molecules. After reduction of the two molecules to their
respective centroids, a uninodal 10-connected net having the
point symbol {315.424.56} was evidenced corresponding to the
chb/CrB topology (Fig. 6, left). Alternatively, these two
inequivalent molecules were considered as a single dimeric
supramolecular entity with a single centroid, leading to a
uninodal 12-connected net having the point symbol
{324.436.56}, corresponding to the fcu/cubic closest packing
topology (Fig. 6, right).
Fig. 5 Solid-state organisation of (19) in (a) and (29) in (b): (a) a view along the
y-axis of the two antiparallel bilayers. (b) The solid-state arrangement of (29)
derived from the superimposed antiparallel layers. It is noteworthy that the
crystal description for (39) is analogous as the one made for (29).
The molecular dipole moments of the two molecules were
found to be 0.68 D and 0.73 D, leading to a packing energy of
227 kJ mol21. As these molecules form a 15-connected net, the
average interaction energy per bond is 227/15 = 21.8 kJ
mol21, demonstrating that this net cannot be based on purely
van der Waals stacking of the molecular entities. Taking
account the existence of p–p interactions evidenced in the
metrical analysis in the form of dimers, the p–p bond energy
may be evaluated as 227/2 = 214 kJ mol21, in good agreement
with theoretical computations that predict values ranging
from 10 kJ mol21 up to 15 kJ mol21 for this kind of
interaction.25
From their respectives MVDPs, (29) and (39) were found to
have a Rsd radius of 4.73 Å (29) and 5.04 Å (39) corresponding
to molecular volumes of 442 Å3 (29) and 536 Å3 (39). The
topology of the complete van der Waals net of both molecules
corresponds to a uninodal 14-connected net with a bcu-x
topology having the point symbol {336.448.57}. This shows that
each molecule is in van der Waals contact with 14 other
molecules. Reducing (29) to its centroid leads to a uninodal 10-
connected net having the point symbol {312.428.55}, corre-
sponding to the bct (body-centered tetragonal) topology (Fig. 7,
left). For (39) an uninodal 6-connected net was evidenced
having the point symbol {412.63}, corresponding to the pcu
topology (Fig. 7, right). Both (29) and (39) have a zero molecular
dipole moment, explaining the much reduced PE = 220 kJ
mol21 relative to the polar molecule (19). The average
Fig. 6 Topological organisation of (19) viewed as a uninodal 10-connected net
displaying the chb/CrB topology based on two crystallographically non-
equivalent molecules (left) or as a uninodal 12-connected net displaying the
fcu/ccp topology based on stacking of molecular dimers (right).
Fig. 4 Molecular structures of linear oligophenylenes (19), (29) and (39). The
distances indicated here correspond to those measured between two terminal
aromatic hydrogen atoms.
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…
unusual disposition of its H-atoms with very short H
H
contacts (0.9 Å) along the direction of the H-bonding. The
X-ray coordinates for H-atoms H1, H2A, H3A and H3B were
thus discarded and re-determined through minimisation of
the partial electrostatic energy of the crystal using PACHA. As
it was not possible to decrease the lattice energy by
¯
considering a unit-cell of P1 symmetry with 5 adjustable
torsion angles, the space group symmetry was lowered to P1
with 10 variable torsion angles. Then, it was possible to find a
significantly more stable configuration for the overall H-bond
pattern (21035.1 kJ mol21 versus 2946.0 kJ mol21 for the
…
original CIF file) without any unrealistically short H
H
Fig. 7 The topological organisation of (29) viewed as a uninodal 10-connected
net displaying the body-centered tetragonal (bct) topology (left) and the
topological organisation of (39) viewed as a uninodal 6-connected net
displaying the primitive cubic (pcu) topology (right).
contacts and where each water molecule forms, as expected,
4 hydrogen bonds (instead of the three in the original CIF file).
With this new optimized structure, TOPOS was able to build
MVDPs for (1) and water, changing the topological radius of (1)
to 3.83 Å with a larger volume of 235 Å3. The topology of the
complete van der Waals was now a 3-nodal (4,6,22)-connected
net with a new yet unknown topology having the point symbol
{35.4}{311.44}{350.4121.559.6}. Each molecule of (1) has 12 van
der Waals contacts with other (1) molecules and 10 other
contacts with water molecules. Considering only H-bonding
interactions, we got a new yet unknown topology based on a
2-nodal (4,8)-connected net having the point symbol
{45.6}2{410.614.84}. For this optimised structure, water mole-
cules were found to act as extremely weak electron donors with
an overall polarity (1)20.01(H2O)2+0.005. (1) was found to be a
significantly polar molecule with a molecular dipole moment m
= 1.1 D. The overall H-bonding packing energy was quite large:
interaction energy per molecule in these two 14-connected
nets was 220/14 = 21.4 kJ mol21, demonstrating the purely
van der Waals nature of these nets.
Concerning the solid-state characterisation of the depro-
tected linear compounds, we were able to obtain X-ray quality
crystals for (1) and (2) by slow evaporation of an ethanol
solution of (1) and by diffusion of n-hexane in an ethyl acetate
solution of (2). Despite the fact that in both cases hydrogen
bonds are the key interaction to govern the crystalline
supramolecular organisation, the crystal descriptions are very
¯
different. Compound (1) crystallises in a P1 space group. The
molecular structure shows that the two aromatic rings adopt a
coplanar arrangement. Analysis of the molecular packing of (1)
reveals that one molecule of (1) co-crystallises with two
equivalent water molecules. Each water molecule behaves at
the same time as a hydrogen bond donor and acceptor with
neighbouring OH groups, as shown in Fig. 8a. The closest
…
…
O3 OH distances are found to be 2.7745(33) Å for O3 O1 and
…
2.7211(19) Å for O3 O2. Interestingly, O2 also interacts with a
neighbouring phenol group through a hydrogen bond, the
…
closest O2 O2 intermolecular distance is 2.7136(40) Å (not
shown on the figure). Thus, an expansion of the motif shown
in Fig. 8a through these two types of hydrogen bond leads to a
two-dimensional sheet (Fig. 8b). Finally, interplanar hydrogen
bonds between the water molecules and the O1 oxygen atoms
are responsible for the three-dimensional arrangement in the
…
form of stacked layers (interlayer O3 O1 distance: 2.8756(33)
Å). The view along the x axis in Fig. 8c focuses on this
interaction.
From its MVDP, (1) has a Rsd radius of 3.73 Å with a volume
of 218 Å3. The topology of the complete van der Waals net of
(1) corresponds to a 2-nodal (5,18)-connected net characterized
by a new yet unknown topology having the point symbol
{35.4}2{330.470.545.67.7}. Each molecule (1) has 10 van der
Waals contacts with other (1) molecules and 8 other contacts
with water molecules. Considering only H-bonding interac-
tions involving (1) and the two water molecules leads to a net
of known topology (tfz-d, UO3) based on a 2-nodal (3,8)-
connected net having the point symbol {43}2{46.618.84}.
However, it is worth noticing that TOPOS was not able to
build a MVDP for the water molecule owing to the rather
Fig. 8 Molecular recognition between (1) and the water molecules in the crystal
structure of (1) is shown in (a). A view along the z axis of the three-dimensional
arrangement of molecules in the crystal structure of (1), in the form of stacked
layers is shown in (b). The dotted lines represent the hydrogen bonds
responsible for the crystal packing. A view along the x axis highlighting the
interlayer hydrogen bond between O1 and a water molecule is shown in (c). The
water molecule and the (1) molecule with the oxygen atoms marked as O3 and
O2, respectively, belong to the layer. It should be noted in (a) that O2 is also
involved in an intermolecular hydrogen bond with a neighbouring (1) molecule
…
(O2 O2 = 2.7136(40) Å). This interaction is not detailed on the figure.
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bonds with two adjacent phenol groups, belonging to two
different molecules. Thus, each of these two OH moieties is
hydrogen bonded with a neighbouring resorcinol unit, leading
to a five oxygen centre recognition motif as shown in Fig. 9a.
Looking at the three-dimensional arrangement, it appears that
each molecule is surrounded on each side by another
oligophenylene derivative, leading to columnar assemblies
that are governed by p-stacked interactions (phenyl rings
centroid distances are measured at around 3.7 Å, see Fig. 9b).
Thus, two of these columnar assemblies sandwiches a layer
containing two ethylacetate molecules and two water mole-
cules. At this stage, the resulting network obtained from the
repetition of the motif described in Fig. 9b could be regarded
as a honeycomb-like structure (Fig. 9c). Finally, the resulting
cavities are fitted by threaded (2)-molecules (Fig. 9d), thereby
the solid-state organisation of (2) is related as a pseudorotax-
ane type structure,26 as it is schematically represented in
Scheme 1.
From their respective MVDPs, the three non-equivalent
molecules of (2) have Rsd radii of 4.38 Å (2a), 4.37 Å (2b) and
4.28 Å (2c), with a volume of 353, 349 and 328 Å3, respectively.
The topology of the complete van der Waals net of the crystal is
a completely new yet unknown 8-nodal (6,6,8,8,11,21,24,28)-
connected net having the stoichiometry (6-c)2(6-c)2(8-c)2(8-
c)2(11-c)2(21-c)2(24-c)(28-c)2.
Molecule (2a) is the node of a 21-connected net having the
point symbol {347.499.559.65}, with nine contacts with other (2)-
molecules, six contacts with water molecules, four contacts
with CH3COOEt molecules and two contacts with a void of
radius 2.23 Å displaying a volume of 46 Å3, occupied by a
single isolated O-atom O13. Molecule (2b) is the node of a 28-
connected net having the point symbol {362.4180.5127.69},
characterised by fourteen contacts with other (2)-molecules
and fourteen contacts with water molecules. Molecule (2c) is
the node of a 24-connected net having the point symbol
{358.4106.589.623}, characterised by ten contacts with other (2)-
molecules, eight contacts with water molecules, four contacts
with CH3COOEt molecules and two contacts with the void.
CH3COOEt molecule is the node of the 11-connected net
having the point symbol {320.427.58} characterised by six
contacts with (2)-molecules, three contacts with the void,
and one contact with a water molecule and another CH3COOEt
Fig. 9 A view along the x-axis of a tetrameric motif composed by four (2)
molecules and two water molecules is shown in (a). A hydrogen bonded
recognition motif composed by five oxygen atoms is highlighted using dotted
lines. A view along the y-axis of trimeric columnar assemblies sandwiching a
layer composed by two water molecules and two ethylacetate molecules is
shown in (b). The hydrogen atoms have been omitted for clarity. A view along
the y-axis of the network partially represented evidencing a honey-comb like
structure is shown in (c). A perspective view evidencing the presence of
threaded (2) molecules within the honey-comb network is shown in (d).
PE = 2153 kJ mol21. As (1) is involved in 8 H-bonds and each
water molecule is involved in 4 H-bonds, this packing energy
corresponds to (8 + 2 6 4)/2 = 8 H-bonds, i.e. to an average
bond energy EHB = 2153/8 = 219 kJ mol21, a value typical of
…
O–H O bonding between neutral molecules. Moreover, by
removing the water dimers, leaving a H-bonded net of (1), it
was possible to figure out the energies of the three kinds of
…
H-bonding interactions at work in this net: EHB(H2O H2O) =
231 kJ mol21; EHB[H2O (1)] = 227 kJ mol21 and EHB[(1) (1)]
= 210 kJ mol21. As expected, the H-bond energy between
phenolic moieties is significantly less stabilizing than that
involving water molecules.
…
…
Next, the solid-state organisation of (2) was examined.
Compound (2) crystallises in a P21/c space group. Four
molecules of (2) crystallise with two ethylacetate molecules
and seven water molecules. The central ring adopts, compared
to the two terminal resorcinol units, a synclinal conformation
(measured torsion angle: 32u). In this structure, the role of the
crystallisation solvent that co-crystallises with (2) is essential
to explain the crystal cohesion. The detailed analysis of the
packing reveals that (2) forms first a layer, which could be
decomposed as an infinite assembly of the tetrameric motif
shown in Fig. 9a. The key feature explaining the formation of
Scheme 1 Schematic representation of the pseudorotaxane type structure of
(2) reflecting a not perfect alignment of the threaded molecules within the
structure (represented in black).
this two-dimensional sheet concerns the presence of
a
bridging water molecule interacting through two hydrogen
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molecules. The void is the node of one of the two 8-connected
nets with three contacts with either (2) or CH3COOEt
molecules and two contacts with water molecules having a
point symbol {311.415.52}. The node of the other 8-connected
net, having a {313.414.5} point symbol, is the O11-based water
molecule having six contacts with (2)-molecules and two
contacts with the void. Finally, the water molecules based on
atoms O12 and O14 form the nodes of two 6-connected nets
sharing the same point symbol {310.45}. The O12-based water
molecule has six contacts with (2)-molecules whereas the O14-
based one has five contacts with (2)-molecules and one contact
with a CH3COOEt molecule.
This very complex topology may be further simplified by
considering only H-bonding interactions between molecular
tectons, generating another completely new 7-nodal
(1,4,4,4,6,8,8)-connected net displaying the stoichiometry (1-
c)2(4-c)2(4-c)2(4-c)2(6-c)(8-c)2(8-c).
Molecule (2a) is now the node of a double 8-connected net
having the point symbol {414.611.72.8} and is H-bonded to itself
through four H-bonds and also to two O11–water (O3, O4) and
two O14–water (O1, O2) molecules. Molecule (2b) is the node
of the other 8-connected net having a point symbol {414.612.72}
and is also H-bonded to itself through four H-bonds, with the
other four bonds involving the O12–water. Molecule (2c) is the
node of a 6-connected net having the point symbol {42.52.72.89}
and is not H-bonded to itself, being rather engaged into one
H-bond with the O14–water through each O7-atom and in two
H-bonds with the O11–water and O12–water through each O8-
atom. Each water molecule is the node of a 4-connected net
but with different point symbols. The point symbol for the
O11–water node is {43} with one H-bond with CH3COOEt, two
H-bonds with (2a) and one H-bond with (2c). The point symbol
for the O12–water node is {4.54.6}, with one H-bond with the
O14–water, two H-bonds with (2b) and one H-bond with (2c).
The point symbol for the O14–water node is {43.5.62}, with one
H-bond with the O12–water, two H-bonds with (2a) and one
H-bond with (2c). Finally, the CH3COOEt molecule H-bonded
to the O11–water molecule is the node of a 1-connected net
having the point symbol {0}, meaning that it corresponds to a
dead-end for the H-bonding networking interactions.
which may be split into two groups. One with an energy quite
similar to that involving CH3COOEt molecules with values:
236 kJ mol21 and EHB(2b wO12)
…
= =
…
EHB(2c wO12)
EHB(2c wO11) = 234 kJ mol21. Then another less stabilizing
…
group with EHB(2a wO14) = 230 kJ mol21, EHB(2a wO11) =
…
…
227 kJ mol21 and EHB(2c wO14) = 225 kJ mol21. The H-bond
…
energy between the two water molecules was quite standard
with EHB(wO12 wO14) = 221 kJ mol21. Finally, the less
…
stabilizing H-bond energies were those linking the (2)-
21
…
molecules together with EHB(2b 2b) = 218 kJ mol
and
EHB(2a 2a) = 217 kJ mol21. Summing together all these
H-bonding interactions according to the observed topology
then leads to an overall H-bond packing energy of PEHB = 2389
kJ mol21. Comparing this value to the total packing energy
leaves 242 kJ mol21 of stabilizing energy through van der
Waals packing. From the van der Waals topology outlined
above, this corresponds to 52 van der Waals interactions, i.e. to
an average energy ,EVdW> = 20.8 kJ mol21 for each van der
Waals interaction. As this is of the right order of magnitude for
this kind of interaction, it may be safely concluded that about
90% of the packing energy may be associated with highly
specific hydrogen bonding interactions whereas the other 10%
comes from non-specific van der Waals stacking between
molecular quasi-neutral tectons.
…
Solid-state structures of the D3h and C2v oligophenylene
derivatives: 49, 59 and 5. The structures of (49) and (59) were
both resolved from crystals obtained when n-pentane was
allowed to diffuse into dichloromethane solutions of the
oligophenylene derivatives. These two compounds crystallise
¯
in the same space group (P1).
In the molecular crystal structure of (49), the two terminal
phenyl rings adopt, respectively, a synperiplanar and a
synclinal conformation in relation to the central phenyl ring
(Fig. 10). At the supramolecular level, the structure of (49)
could be regarded as an infinite self-association of molecules
into chains. According to the structure, the centroid phenyl
ring distance between the two aromatic moieties in these
chains is evaluated at 3.49 Å. From its MVDP, the (49)-molecule
has a topological radius of 4.73 Å for a volume of 444 Å3. The
complete van der Waals topology corresponds to a new
original uninodal 18-connected net having the point symbol
{360.488.55}, meaning that each molecule is in van der Waals
contact with 18 other molecules. The molecular dipole
moments of (49)-molecules were found to be 1.23 D, leading
to a packing energy of 223 kJ mol21. As these molecules form
an 18-connected net, the average interaction energy per van
der Waals bond is 223/18 = 21.3 kJ mol21. This rather low
The next step was to characterise the overall electronic
density partition as well as the relative magnitudes of each
networking interaction within this very interesting new highly
complex net. Partial charges analysis confirms the molecular
nature of this framework with the following charge partition:
20.02
(2a)220.00(2b)+0.06(2c)20.08(CH3COOEt)2
…
value may be associated to weak CH O hydrogen bonds
…
characterized by an average HC O distance of 3.8497(23) Å.
20.02
(wO11)2+0.01(wO12)2+0.015(wO14)2
Concerning the (59) crystal, the crystal organisation is
derived from supramolecular dimers where two (59)-molecules
stack via p–p-interactions with a staggered conformation
(centroid central phenyl ring distance: 3.56 Å) as shown
Fig. 11a. These dimers further interact again via p–p-interac-
tions with neighbouring dimers to form supramolecular
chains and sheets that are interdigitated, as attested in the
crystal view in Fig. 11b. From its MVDP the (59)-molecule has a
Rsd radius of 5.33 Å for a volume of 635 Å3. The complete van
der Waals topology corresponds to a new original uninodal 19-
It is worth noting that (2b) and (2c) have a null dipolar
moment, whereas that of (2b) was found to be m = 0.13 D. The
overall
packing
energy
corresponding
to
a
(2)2?(H2O)3?(CH3COOEt) stoichiometry was found to be: PE =
2430 kJ mol21. The largest stabilizing H-bond energy was that
involving the non-networking CH3COOEt molecules (m = 2.03
D) with EHB(CH3COOEt wO11) = 237 kJ mol21. Next comes
…
the H-bonding interaction between (2) and water molecules,
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AC2. Acetone molecule AC2 is the node of a 12-connected net
having the point symbol {327.434.55}, characterised by five
contacts with (5)-molecules, three contacts with AC1, two
contacts with AC2 and two contacts with a water molecule.
Acetone molecule AC1 is the node of an 8-connected net
having the point symbol {317.411}, characterised by five
contacts with (5)-molecules and three contacts with acetone
molecule AC2. Finally water is the node of a 7-connected net
having the point symbol {315.46}, characterised by five contacts
with (5)-molecules and two contacts with acetone molecule
AC2. As before, this topology may be further simplified by
considering only H-bond interactions between molecular
tectons, generating another new 4-nodal (1,1,3,9)-connected
net displaying the stoichiometry (1-c)(1-c)(3-c)(9-c).
Molecule (5) is now the node of a 9-connected net having the
point symbol {413.614.8} and is H-bonded to itself through six
H-bonds, to water molecules with two H-bonds and to the
acetone molecule AC1 with one H-bond. The point symbol for
the water node of the 3-connected net is {4} with two H-bonds
with (5) and one H-bond with the acetone molecule AC2.
Finally, both the acetone molecules AC1, which is H-bonded to
(5) and AC2, which is H-bonded to water, are the nodes of a
two 1-connected net having the point symbol {0} and should
thus be considered as dead-ends for H-bonding networking
interactions.
Fig. 10 The molecular structure of (49) is shown in (a). An illustration of the
solid-state supramolecular organisation of (49) is shown in (b). A distance of
3.49 Å between two centroid phenyl rings (represented as a dotted line) is
estimated from the structure evidencing p–p-interaction leading to the
formation of a supramolecular dimer. Two dimeric motifs are self-associated via
…
CH O contacts as illustrated by the two dotted lines joining the hydrogen and
…
the oxygen atoms (average measured HC O distances: 3.8497(23) Å).
Partial charges analysis confirms the molecular nature of
this framework with the following charge partition:
connected net having the point symbol {363.4102.56}, meaning
that each molecule is in van der Waals contact with 19 other
molecules. The molecular dipole moments of (59)-molecules
were found to be 1.70 D, leading to a packing energy of 245 kJ
mol21. As these molecules form a 19-connected net, the
average interaction energy per van der Waals bond is 245/19 =
22.4 kJ mol21. As this value is a little bit too high for pure van
der Waals interactions, a (59)-dimer was generated allowing us
(5)20.11(H2O)+0.03(AC1)+0.03(AC2)+0.04
21
…
to derive an interaction energy Eint(59 59) = 217 kJ mol
,
which is more in line with aromatic p–p-stacking. Linking
dimers into chains, chains into layers and stacking layers
21
…
21
together then leads to Eint(dim dim) = 211 kJ mol
,
…
…
and Eint(layer layer) =
Eint(chain chain) = 210 kJ mol
211 kJ mol21
.
Single crystals of (5) were produced when an acetone
(solvent)/chloroform (counter-solvent) system was used.
Fig. 12 partially represents the supramolecular organisation
of the crystal. Again, in the crystal, p-stacked interactions
generate columnar assemblies (not shown on the figure).
Perpendicularly to this 1D network, (5) is involved in a
hydrogen bonded network. Fig. 12 highlights the organisation
of four (5)-molecules in the crystal through four hydrogen
bonds leading to pseudo-channels filled with acetone and
water molecules (not shown on the figure). Molecules of (5)
have a Rsd radius of 4.74 Å for a volume of 446 Å3. The
topology of the complete van der Waals net of the crystal is
again a new unknown 4-nodal (7,8,12,26)-connected net
having the stoichiometry (7-c)(8-c)(12-c)(26-c). (5) is the node
of a 26-connected net having the point symbol {373.4159.591.62},
with eleven contacts with other (5)-molecules, five contacts
with a water molecule, five contacts with a first acetone
molecule AC1 and five contacts with another acetone molecule
Fig. 11 A view of two (59)-dimers self-associated via p-stacked interactions is
shown in (a). These dimers, where a staggered conformation is observed, result
from an aromatic stacking between the central phenyl rings of the molecules.
The hydrogen atoms have been omitted for clarity. A view of the interdigitated
sheets that compose the crystal structure is shown in (b).
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tions,33 oligophenyl groups,34 carboxylic acids,35 sulfonic
acids,36 nitro groups37 and acetylenic derivatives.38 However,
for the tetraphenylmethane-based building block containing
phenol functionalities only one example of a molecule that
self-assembles into a zeolitic network without the need of a co-
crystal agent has been reported.39 Thus, in the aim to
characterise novel clathrate structures based on tetraphenyl-
methane derivatives, the ortho-methoxy-substituted tetraphe-
nylmethane derivative (69) crystallises in the space group Pbcn
as an inclusion compound. However, due to the presence in
the structure of highly disordered solvent molecules, which
could not be refined satisfactorily, the SQUEEZE command
was used to resolve the structure. The molecular structure is
shown in Fig. 13, the crystallisation of (6) and (69) was
undertaken. Single crystals of (69) suitable for X-ray analysis
were obtained when toluene was allowed to slowly diffuse in a
dichloromethane solution of (69).
This structure indicates that in the crystal (69) adopts a C2
symmetry, since the two 1,3-dimethoxybenzene groups that
decorate the tetraphenylmethane core adopt an anti–anti
conformation whereas the two other groups display a syn–anti
conformation. As shown in Fig. 13c, the crystalline network of
(69) leads to a zeolite-like structure, where the 1D-channels are
originated from the association of four molecules via weak
interactions (Fig. 13b). Such a tetrameric motif is essentially
…
Fig. 12 Hydrogen bonding network in the crystal of 5. d(O3 O6) = 2.7200(16)
…
…
Å, d(O5 O2) = 2.8714(17) Å, d(O1 O4) = 2.6708(19) Å.
The molecular dipolar moment of (5) was found to be m = 0.4
D, with an overall packing energy corresponding to
(5)?(H2O)?(Me2CO)2 stoichiometry that was found to be: PE =
2299 kJ mol21. The largest stabilizing H-bond energy was
a
…
involving the non-networking acetone AC1 with EHB(5 AC1) =
247 kJ mol21. Next, comes the H-bonding interaction between
(5) and the water molecule: EHB(5 H2O) = 235 kJ mol21. The
…
H-bond energy between the water molecules and the other
…
non-networking acetone molecule was EHB(wO12 wO14) =
226 kJ mol21. Finally, the less stabilizing H-bond energies
…
were those linking (5)-molecules together with EHB(5 5) = 217
kJ mol21. Summing together all these H-bonding interactions
according to the topology then leads to an overall H-bond
packing energy PEHB = 2276 kJ mol21. Comparing this value
to the total packing energy leaves 223 kJ mol21 of stabilizing
energy through van der Waals packing. From the van der
Waals topology outlined above, this corresponds to 27 van der
Waals interactions, i.e. to an average energy ,EVdW> = 20.9 kJ
mol21 for each van der Waals interaction. Consequently, it
may be safely concluded that about 92% of the packing energy
may be associated with highly specific hydrogen bonding
interactions whereas the other 8% comes from non-specific
van der Waals stacking between molecular quasi-neutral
tectons.
Solid-state structures of the tetraphenylmethane derivatives:
6 and 69. In the field of crystal engineering, molecules based
on a tetraphenylmethane backbone are particularly attractive
building blocks since these compounds usually self-assemble
into crystalline networks, encapsulating guest molecules in
large channels.
A survey of the 1.1.1 release of the Cambridge Structural
Database reveals that about forty tetraphenylmethane-based
molecules displaying a Td symmetry have been reported. These
tetraphenylmethane derivatives are decorated at the periphery
with a large panel of groups or functions, which include for
instance halogens,27 pyridine rings,28 triazine derivatives,29
boronic acids,30 silanols,31 amide connections,32 cyano func-
Fig. 13 The molecular structure of (69) is shown in (a). A view along the y-axis of
a tetrameric motif that permits the formation of 1D-channels is shown in (b).
The tetrameric assembly formation is induced by several weak interactions.
Different types of short contacts are identified as represented on the figure by
dotted lines (the distances indicated here correspond to the hydrogen–oxygen
distances or the hydrogen-centroid phenyl ring distances estimated from the
structure. A space filling representation of the zeolite-like structure of (69) self-
assembled network is shown in (c), viewed along the y-axis.
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Perpendicularly to these columns, the recognition between
one
6 molecule with eight neighbouring molecules is
originated from a complex hydrogen-bond dominated pattern,
implying four resorcinol units as highlighted by the expansion
shown in Fig. 15b. The simulation of the channel profile
indicates the lake of homogeneity concerning the inner
diameter of the channel where the inner diameter of the
channel is ranging from 4.3 Å to 2.54 Å (Fig. 16). A guest
accessible volume of approximately 28% of the volume of the
crystal40 has been estimated that is in the same accessible
volume range as the one already reported for tetrakis(4-
hydroxyphenyl)methane.39
Fig. 14 Channel aperture along the [010] axis assuming van der Waals radii of
1.2, 1.52 and 1.7 Å for H, O and C-atoms in the crystal of (69).
Molecules of (6) have a Rsd radius of 6.53 Å for a volume of
1165 Å3. The topology of the complete van der Waals net of the
crystal was found to be a uninodal 14-connected net having
the point symbol {336.446.59}, with fourteen contacts with other
(6)-molecules corresponding to the known gpu-x topology in
the RCSR database. Considering only H-bonding interactions
between molecular tectons, the topological type was found to
be that of a sql/Shubnikov tetragonal plane net having a point
symbol {44.62}. In order to check if this molecule was indeed
able to build a 3D-net, the atomic positions of the four
H-atoms bonded to oxygen atoms O1–O4 were optimized
through minimization of the PACHA lattice energy leading to a
bcu-topology corresponding to a uninodal 8-connected net
having a point symbol {424.64}. The molecular dipolar moment
of (6) was found to be m = 0.31 D with an overall packing energy
…
…
generated by CH p, CH O interactions as well as p–p
interactions, as attested by the short contact distances
measured from the structure (see Fig. 13b).
Interestingly, the inner diameter of the channel is ranging
from 4.9 Å and 3.9 Å, as demonstrated in the channel aperture
profile shown in Fig. 14. The solvent-accessible free volume of
these channels is estimated to represent 20.9% of the total
crystal volume.40 Next, to better characterise this organic
crystalline materials, the synthesis of a crystalline powder
using the same solvent conditions as those employed to
produce the single crystals was attempted.
Upon scale-up of the quantity of (69) for crystallisation, the
resulting crystalline powder was shown to be a second
polymorph of (69), since the X-ray diffraction powder pattern
of the as-synthetized powder is strongly different from the one
simulated from the X-ray single crystal diffraction data. The
thermogravimetric analysis (TGA) performed on the crystalline
powder evidenced no significant weight loss indicating the
presence of an apohost phase. From its MVDP the (69)-
molecule has a Rsd radius of 6.81 Å for a volume of 1323 Å3.
The complete van der Waals topology corresponds to a new
original uninodal 20-connected net having the point symbol
{354.4126.510}. Molecule (69) was found to be rather polar (m =
1.70 D), leading to a quite large packing energy: PE = 257 kJ
mol21. Each (69)-molecule being in contact with twenty other
(69)-molecules, the average interaction energy per contact is
,Eint> = 257/20 = 22.9 kJ mol21, a value much too high for
pure van der Waals bonding. Generating a (69)-chain allows us
PE = 2134 kJ mol21
.
Ten supramolecular interactions may be identified in this
…
net: two bifurcated H-bonds (O3–H3 O2 = 206 pm and O3–
…
…
H3 O4 = 235 pm), two non-bifurcated H-bonds (O1–H1 O3 =
…
…
183 pm) and four O–H p bonds (O2–H2 Ph = 244 pm and
O4–H4 Ph = 266 pm). In order to quantify the relative
…
magnitude of each of these contributions, full rotation of the
four O–H moieties along their respective C–O were performed
in order to retrieve the respective energy profiles (Fig. 17).
The largest stabilizing energy (257 kJ mol21) is lost after
breaking the O3–H3 bifurcated H-bond (bottom left of Fig. 17).
Then comes the O2–H2 p-interaction (top right with 248 kJ
mol21) and the O1–H1 single H-bond (top left with 241 kJ
mol21). Finally, the least stabilizing energy is associated to the
O4–H4 p-interaction (bottom right with 221 kJ mol21).
By employing the same crystallisation conditions as the
ones described just above, we were able to produce on a
preparative scale crystals of (6) with a very high degree of
reproducibility. The obtained phase was identical to the one
evaluated by the single crystal analysis as confirmed by X-ray
powder analysis. The capacity to produce crystals on a large
scale allowed us to study more in detail the thermal behaviour
of this porous network. The presence of guests trapped into
the channels was confirmed by thermogravimetric analysis
(TGA). A weight loss of 18.5% between 30 uC and 250 uC was
observed. For this range of temperature, a closer observation
of the TGA curve indicates three inflection regions that are
linked with three endotherms measured at 80 uC, 120 uC and
160 uC by DSC. Obviously, these endothermic processes
correspond to the desolvation of the crystallisation solvents
(ethyl acetate, bp = 77 uC and toluene bp = 110 uC). Whereas
the two first endotherms may be attributed to free molecules,
21
…
to derive an interaction energy Echain(69 69) = 218 kJ mol
,
corresponding clearly to p–p interactions. Linking chains into
2D-layers then leads to Eint(chain chain) = 29 kJ mol21, and
…
…
finally stacking layers together gives Eint(layer layer) = 230 kJ
mol21
.
Single crystals of the Td symmetric derivative (6) display the
space group C2/c and were grown in an ethylacetate solution
upon slow diffusion of toluene. The structure was solved using
the Squeeze command due to the presence to highly
disordered solvent molecules within the structure. The
structure analysis also revealed that the solid-state organisa-
tion of (6) led to a network with 1D channels (Fig. 15). A close
observation of the structure indicates that the 1D channels are
generated by the assembly of infinite columns. These columns
…
result from the stack of 6 units via CH O interactions.
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…
…
Fig. 15 A view along the z-axis of two stacked (6) molecules through CH O interactions (mean intermolecular H O distance: 3.17 Å) is shown in (a). The repetition
of this motif leads to two infinite columnar assemblies. A view along the y-axis of four columnar assemblies is shown in (b). The interactions between a molecule of (6)
with the neighbouring partners that belong to other columns are mainly due to hydrogen bonds. The expansion shows the complex recognition motif between four
resorcinol units that belong respectively to four different (6) molecules. A space filling representation of the zeolite-like structure of the (6) self-assembled network is
shown in (c), viewed along the y-axis.
the last endotherm is unambiguously linked to the departure
of solvent molecules that are trapped into the channels. Thus,
to evaluate the possibility to obtain a crystalline apohost phase
via a thermal treatment, the X-ray diffraction powder analysis
at various temperatures was performed from 30 uC to 190 uC.
Fig. 18 shows three selected X-ray powder diffractograms. First
of all, no phase transformation was observed upon elevating
the temperature of the crystalline sample. Obviously, the
temperature induces a dramatic loss of crystallinity. However,
when the X-ray diffractogram was recorded at 130 uC, (i.e. after
the two first desolvation processes according the DSC
analysis), the solid conserves a certain degree of crystallinity
but when all the solvent is removed from the structure (at 170
uC) the resulting apohost phase is amorphous. Nevertheless, at
this stage the preservation of porosity for the apohost phase
could not be excluded.
Fig. 17 Energy profiles for the 4 kinds of supramolecular interactions at work in
the bcu net (Z = 4) based on (6). The full lines show the variation of the total
electrostatic polarisation energy (self) when a given O–H moiety is rotated along
its C–O bond by 360u. The dotted lines show the variation of the total electron–
electron repulsions (steric) computed using Gordon–Kim potentials.
Fig. 16 Channel aperture along the [010] axis assuming van der Waals radii of
1.2; 1.52 and 1.7 Å for H, O and C-atoms in the crystal of (6).
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Replacing the methoxy groups by hydroxy groups allowed
the occurrence of hydrogen bonding interactions with H-bond
energies ranging from 217 kJ mol21 down to 257 kJ mol21
.
The weakest bonds involved intermolecular H-bonds between
phenolic groups whereas the strongest bonds involved inter-
molecular H-bonds with small solvent molecules such as
water, ethylacetate or acetone. It is worth noticing that in all
cases it was not possible to obtain molecular nets free of
solvent molecules. When it was possible to localise solvent
molecules, in the cases of (1), (2) and (5), quite complex
unprecedented topologies have been evidenced, with connec-
tivities ranging from 18-c up to 28-c taking into account both
van der Waals and H-bonding and connectivities of 8-c or 9-c
considering H-bonding alone. Compound (6) was a special
case as, owing to its largely porous structure, it was not
possible to localise solvent molecules. This explains the low
Fig. 18 Three X-ray powder diffractograms of the (6) crystalline powder
recorded at 30 uC, 130 uC and 170 uC.
value (14-c) found for the van der Waals plus H-bonding
…
connectivity. The occurrence of quite strong aromatic O–H
…
p
bonding interactions in addition to normal O–H O bonding
and the occurrence of a bifurcated H-bond are also worth
noticing in this last case. Our inability to obtain single-crystals
for compounds (3) and (4) could well be due to an obviously
more flexible character for (3) and to a rather low symmetry for
(4) favouring strong solvation in solution. The next step is now
to investigate how these molecules may react with Ti(IV)
tetraalkoxides in order to obtain Ti–O based MOFs absorbing
visible rather than ultra-violet light. Work is under progress
and results will be reported elsewhere.
Conclusions
In conclusion, we have been able to synthesise and character-
ise several new resorcinol-based oligophenylene molecules
displaying highly symmetric structures and that were able to
self-assemble into interesting topologies through van der
Waals and/or aromatic p–p stacking for methoxy-protected
compounds and through H-bonding interactions in the case of
deprotected molecules.
Concerning the methoxy-protected compounds, uninodal
nets displaying connectivities ranging from 14 to 20 have been
observed, with the exception of (19), which forms a binodal 15-
connected net. Most interestingly, most of the observed
topologies are unprecedented with the exception of (29) and
(39) that adopt the familiar bct-topology. Obviously, the
highest connectivity was observed with (69) that has 8 aromatic
rings and the lowest one for (29) that has only 3 aromatic rings.
But it is worth noticing that (49), which has also 3 aromatic
rings, forms an 18-connected net whereas (19) with only 2 rings
forms a 15-connected net. Similarly it was observed that (39)
leads to a 14-connected net like (29), whereas (59) leads to a 19-
connected net despite the fact that both molecules have the
same number of aromatic rings. The number of aromatic rings
is thus not a good discriminator for predicting the net
connectivity and explaining the trends observed for melting
points. However, dividing the packing energy by the net
connectivity leads to the following order: 21.3 (49) > 21.4 (29),
(39) > 21.8 (19) > 22.4 (59) > 22.9 (69) and this could nicely
explain the rather low melting point of (49) and quite high
melting point of (69) relative to the other members of the
series. Obviously, a perfect correlation would not be expected
owing to the fact that upon melting both enthalpy (packing
energies) and entropy (degrees of freedom) factors have to be
taken into account. Finally, only (19), (59) and (69) were found
to be associated through aromatic p–p stacking with interac-
tion energies ranging from 214 kJ mol21 down to 218 kJ
Experimental section
General
All chemicals, solvents and reagents were of the best
commercially available grade and purchased from Alfa Aesar,
Sigma Aldrich, TCI Europe or Fluka and used as received. All
reactions involving moisture-sensitive reactants were con-
ducted under a nitrogen atmosphere. Column chromatogra-
phy was performed on silica gel 60 (particle size: 40–63 mm,
Merck, Darmstadt, Germany). For thin-layer chromatography
silica gel 60 sheets (POLYGRAM SIL G/UV254, Macherey-Nagel,
Du¨ren, Germany) were used, detected under UV-light at 254
nm. 1H and 13C NMR spectra were recorded with a Bruker
Avance 300 (300 MHz) spectrometer with use of a deuterated
solvent as the lock. The chemical shifts were expressed in parts
per million (ppm, d) and referenced to residual solvent protons
as internal standards (1H NMR: CDCl3: d = 7.26 ppm, CD3OD: d
= 3.31 ppm; 13C NMR: CDCl3: d = 77.16 ppm, CD2Cl2: d = 53.84
ppm, CD3OD: d = 49.00 ppm). All coupling constants are
absolute values and J values are expressed in Hertz (Hz). The
description of signals include: s singlet, d doublet, dd doublet
of doublets, t triplet, m multiplet. The signal abbreviations
include: PhH aromatic proton, OMe methoxy proton. Infrared
(IR) spectra were recorded with a Shimadzu FTIR-8400S.
Fluorescence spectra were recorded with a Perkin Elmer
LS55 Fluorescence Spectrometer. UV-vis spectra were recorded
with a BioTek UVIKON XL spectrometer. Thermogravimetric
mol21
.
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analysis (TGA) were performed on a Perkin Elmer Pyris 6 TGA
thermogravimetric analyzer. Differential Scanning Calorimetry
(DSC) spectra were obtained with a Perkin Elmer Jade DSC
calorimeter. Melting points (M.p.) were determinated using a
Stuart Scientific Melting Point SMP1 apparatus. Mass spectra
were obtained with a micrOTOF in positive mode (ESI-MS).
Microanalyses were performed by the Service de Microanalyses
817, 748, 672 cm21. Crystals were obtained by slow evapora-
tion of a solution of 1 in ethanol. X-ray data for 1: empirical
formula: C12H14O6 (C12H10O4, 2H2O); formula mass: 254.23;
¯
crystal system: triclinic; space group: P1; unit cell dimensions:
a = 4.9700(2) Å, b = 7.4370(3) Å, c = 7.9748(4) Å; a = 85.355(2), b
= 82.615(2), c = 75.241(2); V = 282.32(2) Å3; Z = 1; density
(calcd): 1.495 Mg m23; crystal size: 0.09 6 0.07 6 0.05 mm; h
range for data collection: 2.58–27.00u; reflections collected:
2867; independent reflections: 1205 [Rint = 0.0160]; refinement
method: full-matrix least squares on F2; data/restraints/
parameters: 1205/3/90; goodness-of-fit on F2: 1.060; final R
indices [I > 2s(I)]: R1 = 0.0454, wR2 = 0.1330; R indices (all
data): R1 = 0.0511, wR2 = 0.1396. CCDC: 934386.
´ ´
´
de la Federation de Recherche de Chimie, Universite de
Strasbourg, Strasbourg, France. Crystallography data were
collected at 173(2) K with a Bruker APEX8 CCD diffractometer
equipped with an Oxford cryosystem liquid N2 device, with use
of graphite-monochromated Mo Ka (l = 0.71073) radiation.
For all structures, diffraction data were corrected for absorp-
tion, and structural determination was achieved by using the
APEX (1.022) package. Tetrakis(4-bromophenyl)methane was
obtained according ref. 41.
3,399,5,599-Tetramethoxy-1,19:49,199-terphenyl (29)
The reaction was conducted under a nitrogen atmosphere. A
degassed aqueous solution of Na2CO3 (2 M, 40 mL) was
3,39,5,59-Tetramethoxy-1,19-biphenyl (19)18
transferred by cannula to
a degassed solution of 1,4-
To a stirred solution of 3,5-dimethoxybenzeneboronic acid
(170 mg, 0.93 mmol) in methanol (19 mL) was added Pd(OAc)2
(20.9 mg, 0.09 mmol). The mixture was stirred under air for
five hours at room temperature and concentrated under
reduced pressure. The remaining crude product was purified
by silica gel chromatography (CH2Cl2/n-pentane, 50/50) to
yield a white solid (127 mg, 98%). M.p. 108 uC (lit. 109–111 uC).
1H NMR (300 MHz, CDCl3): d = 6.69 (d, J = 2.2 Hz, 4H, PhH),
6.45 (t, J = 2.2 Hz, 2H, PhH), 3.82 (s, 12H, OMe) ppm. 13C NMR
dibromobenzene (500 mg, 2.12 mmol) and Pd(PPh3)4 (120
mg) in toluene (40 mL). After the cannulation of a solution of
3,5-dimethoxy-phenylboronic acid (1.07 g, 5.88 mmol) in
MeOH (40 mL), the reaction mixture was refluxed overnight.
The mixture was allowed to reach room temperature and
extracted three times with CH2Cl2. The combined organic
layers were dried over MgSO4 and concentrated under reduced
pressure. The crude product was purified over a silica gel
chromatography (CH2Cl2/n-pentane 50/50) to give 29 as a white
1
˜
(75 MHz, CDCl3): d = 161.5, 143.7, 105.8, 99.8, 55.8 ppm. IR: v =
powder (606 mg, 82%). M.p. 149–150 uC. H NMR (300 MHz,
3006, 1604, 1577, 1470, 1410, 1291, 1195, 1156, 1030, 861, 845,
816, 692 cm21. Crystals were obtained by slow diffusion of
n-pentane into a CH2Cl2 solution of 1. X-ray data for 1:
empirical formula: C16H18O4; formula mass: 274.30; crystal
system: orthorhombic; space group: Pna21; unit cell dimen-
sions: a = 16.655(3) Å, b = 7.4707(7) Å, c = 22.232(3) Å; V =
2766.3(6) Å3; Z = 8; density (calcd): 1.317 Mg m23; crystal size:
0.12 6 0.09 6 0.01 mm; h range for data collection: 1.83–
27.53u; reflections collected: 8997; independent reflections:
4044 [Rint = 0.0283]; refinement method: full-matrix least
squares on F2; data/restraints/parameters: 4044/1/370; good-
ness-of-fit on F2: 1.001; final R indices [I > 2s(I)]: R1 = 0.0417,
wR2 = 0.0934; R indices (all data): R1 = 0.0508, wR2 = 0.1005.
CCDC: 934379.
CDCl3): d = 7.63 (s, 4H, PhH), 6.76 (d, J = 2.1 Hz, 4H, PhH), 6.47
(t, J = 2.1 Hz, 2H, PhH), 3.85 (s, 12H, OMe) ppm. 13C NMR (75
MHz, CDCl3): d = 161.5, 143.1, 140.7, 127.8, 105.6, 99.7, 55.8
˜
ppm. IR: v = 2947, 2836, 1608, 1583, 1462, 1332, 1228, 1201,
1162, 1037, 1014, 940, 826, 689 cm21. MS (ESI): calcd for [M +
Na]+ 373.142, found 373.141. C22H22O4 (350.15): calcd C 75.41,
H 6.33; found C 74.31, H 6.32%. Crystals were obtained by
slow diffusion of n-pentane into a CH2Cl2 solution of 29. X-ray
data for 29: empirical formula: C22H22O4; formula mass:
350.40; crystal system: monoclinic; space group: P21/c; unit
cell dimensions: a = 13.0066(5) Å, b = 8.3251(3) Å, c = 8.5054(3)
Å; b = 106.143(2)u; V = 884.66(6) Å3; Z = 2; density (calcd): 1.315
Mg m23; crystal size: 0.10 6 0.07 6 0.06 mm; h range for data
collection: 1.63–29.99u; reflections collected: 21 371; indepen-
dent reflections: 2550 [Rint = 0.0253]; refinement method: full-
matrix least squares on F2; data/restraints/parameters: 2550/0/
120; goodness-of-fit on F2: 1.078; final R indices [I > 2s(I)]: R1 =
0.0457, wR2 = 0.1384; R indices (all data): R1 = 0.0607, wR2 =
0.1595. CCDC: 934380.
3,39,5,59-Tetrahydroxy-1,19-biphenyl (1)18
The reaction was conducted under nitrogen. At 278 uC, to a
solution of 1 (1 g, 3.65 mmol) in freshly distilled CH2Cl2 (20
mL) was added dropwise a solution of BBr3 (1 M in CH2Cl2,
17.5 mL). The resulting reaction mixture was allowed to reach
room temperature and stirred overnight. Then, a small
amount of water was carefully added (40 mL). The mixture
was washed with an aqueous Na2CO3 solution (2 M, 200 mL)
and then acidified with HCl 37% until acid pH was reached.
The water phase was extracted three times with diethyl ether
and the organic layers were combined and concentrated under
reduced pressure to afford 1 as a brownish powder (795 mg,
3,399,5,599-Tetrahydroxy-1,19:49,199-terphenyl (2)
The reaction was conducted under a nitrogen atmosphere. At
278 uC, to a solution of 29 (475 mg, 1.36 mmol) in freshly
distilled CH2Cl2 (10 mL) was added dropwise a solution of
BBr3 (1 M in CH2Cl2, 6.51 mL). The resulting reaction mixture
was stirred overnight at room temperature. Then, a small
amount of water was carefully added (10 mL). The mixture was
washed with an aqueous Na2CO3 solution (2 M, 200 mL) and
then acidified with HCl 37% until acid pH was reached. The
solid was recovered by filtration and dried under reduced
pressure to afford 2 as a brownish powder (370 mg, 93%). M.p.
1
quantitative). M.p. > 300 uC (lit. 310 uC). H NMR (300 MHz,
CD3OD): d = 6.46 (d, J = 2.2 Hz, 4H, PhH), 6.22 (t, J = 2.2 Hz, 2H,
PhH) ppm. 13C (75 MHz, CD3OD): d = 158.8, 142.7, 108.4, 102.5
˜
ppm. IR: v = 3282, 2968, 1618, 1424, 1292, 1153, 1136, 1002,
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1
> 300 uC. H NMR (300 MHz, CD3OD): d = 7.57 (s, 4H, PhH),
6.57 (d, J = 2.2 Hz, 4H, PhH), 6.26 (t, J = 2.2 Hz, 2H, PhH). 13C
NMR (75 MHz, CD3OD): d = 160.1, 144.3, 141.7, 128.3, 106.7,
(10 mL) was added dropwise a solution of BBr3 (1 M in CH2Cl2,
9.2 mL). The resulting reaction mixture was allowed to reach
room temperature and stirred overnight. Then, a small
amount of water was carefully added (10 mL). The mixture
was washed with an aqueous Na2CO3 solution (2 M, 20 mL)
and then acidified with HCl 37% until acid pH was reached.
The precipitate formed was filtered, washed with an excess of
water and dried under reduced pressure to afford 4 as a white
solid (560 mg, quantitative). M.p. > 300 uC. 1H NMR (300 MHz,
CD3OD): d = 7.67 (t, J = 1.7 Hz, 1H, PhH), 7.48 (t, J = 2 Hz, 1H,
PhH), 7.43 (m, 2H, PhH), 6.57 (d, J = 2 Hz, 4H, PhH), 6.27 (t, J =
2.2 Hz, 2H, PhH) ppm. 13C NMR (75 MHz, CD3OD): d = 159.9,
˜
102.9 ppm. IR: v = 3280, 1595, 1487, 1345, 1151, 1001, 867, 818,
678 cm21. MS (MALDI-TOF): calcd for [M]+ 294.09, found
294.20. C18H14O4 (294.09)?2H2O: calcd C 65.45, H 5.49; found
C 65.96, H 5.25%. Crystals were obtained by slow evaporation
of a solution of 2 in ethyl acetate. X-ray data for 2 (the structure
was solved using the SQUEEZE command): empirical formula:
(4C18H14O4, C4H8O2, 6H2O); formula mass: 1479.49; crystal
system: monoclinic; space group: P21/c; unit cell dimensions: a
= 15.0657(3) Å, b = 9.2696(2) Å, c = 28.1087(6) Å; b =
91.7970(10)u; V = 3923.53(14) Å3; Z = 2; density (calcd): 1.252
Mg m23; crystal size: 0.11 6 0.08 6 0.06 mm; h range for data
collection: 1.95–28.34u; reflections collected: 35 365; indepen-
dent reflections: 9642 [Rint = 0.0564]; refinement method: full-
matrix least squares on F2; data/restraints/parameters: 9643/
11/480; goodness-of-fit on F2: 1.052; final R indices [I > 2s(I)]:
R1 = 0.0820, wR2 = 0.2526; R indices (all data): R1 = 0.1189, wR2
= 0.2763. CCDC: 934375.
˜
144.5, 143.0, 129.9, 126.8, 126.3, 106.6, 102.6 ppm. IR: v =
3340, 3180, 1606, 1597, 1511, 1472, 1332, 1306, 1210, 1155,
1007, 824, 773, 708, 677 cm21. MS (ESI) calcd for [M + Na]+
317.08, found 317.08. C18H14O4 (294.09)?2H2O: calcd C 65.45,
H 5.49; found C 64.97, H 5.56%.
3,3999,5,5999-Tetramethoxy-1,19:49,199:499,1999-quaterphenyl (39)
The reaction was conducted under a nitrogen atmosphere. A
degassed aqueous solution of Na2CO3 (2 M, 60 mL) was
transferred by cannula to a degassed solution of 1-bromo-3,5-
dimethoxybenzene (1.375 g, 6.33 mmol) and Pd(PPh3)4 (0.120
g) in toluene (60 mL). After the cannulation of a solution of
biphenyl-4,49-diboronic acid bis(neopentyl glycol) ester (1 g,
2.64 mmol) in MeOH (60 mL), the reaction mixture was
refluxed during four days. The mixture was allowed to reach
room temperature and extracted three times with CH2Cl2. The
combined organic layers were dried over MgSO4 and concen-
trated under reduced pressure. The crude product was purified
over a silica gel chromatography (CH2Cl2/n-pentane 50/50) to
3,399,5,599-Tetramethoxy-1,19:39,199-terphenyl (49)
The reaction was conducted under a nitrogen atmosphere. A
degassed aqueous solution of Na2CO3 (2 M, 64 mL) was
transferred by cannula to
a degassed solution of 1,3-
dibromobenzene (1.89 g, 8 mmol) and Pd(PPh3)4 (0.45 g) in
toluene (64 mL). After the cannulation of a solution of 3,5-
dimethoxyphenylboronic acid (3.40 g, 18.7 mmol) in MeOH
(62 mL), the reaction mixture was refluxed overnight. The
mixture was allowed to reach room temperature and extracted
three times with CH2Cl2. The combined organic layers were
dried over MgSO4 and concentrated under reduced pressure.
The crude product was purified over a silica gel chromato-
graphy (CH2Cl2/n-pentane 50/50) to give 49 as a white powder
(2.47 g, 88%). M.p. 87 uC. 1H NMR (300 MHz, CDCl3): d = 7.77
(t, J = 1.8 Hz, 1H, PhH), 7.58 (t, J = 1.8 Hz, 1H, PhH), 7.51 (m,
2H, PhH), 6.78 (d, J = 2.2 Hz, 4H, PhH), 6.49 (t, J = 2.2 Hz, 2H,
PhH), 3.86 (s, 12H, PhH) ppm. 13C NMR (75 MHz, CDCl3): d =
161.1, 143.4, 141.8, 129.1, 126.5, 126.2, 105.6, 99.5, 55.5 ppm.
1
give 39 as a white powder (1.012 g, 90%). M.p. 162–163 uC. H
NMR (300 MHz, CDCl3): d = 7.72 (dd, J = 8.8 Hz, J = 4.6 Hz, 8H,
PhH), 6.81 (d, J = 2.3 Hz, 4H, PhH), 6.49 (t, J = 2.3 Hz, 2H,
PhH), 3.86 (s, 12H, OMe) ppm. 13C NMR (75 MHz, CDCl3): d =
161.7, 143.1, 140.5, 140.1, 127.9, 127.6, 105.6, 99.8, 55.8 ppm.
˜
IR: v = 3002, 2945, 2833, 1586, 1460, 1332, 1220, 1202, 1163,
1082, 1040, 1030, 821, 688 cm21. MS (ESI) calcd for [M + H]+
427.191, found 427.181. C28H26O4 (426.18): calcd C 78.85, H
6.14; found C 76.42, H 6.30%. Crystals were obtained by slow
diffusion of n-pentane into a CH2Cl2 solution of 39. X-ray data
for 39: empirical formula: C28H26O4; formula mass: 426.49;
crystal system: monoclinic; space group: P21/c; unit cell
dimensions: a = 15.6242(12) Å, b = 8.1550(6) Å, c = 8.4742(6)
Å; b = 96.557(2)u, V = 1072.68(14) Å3; Z = 2; density (calcd):
1.320 Mg m23; crystal size: 0.09 6 0.06 6 0.04 mm; h range
for data collection: 2.62–28.28u; reflections collected: 6060;
independent reflections: 2637 [Rint = 0.0252]; refinement
method: full-matrix least squares on F2; data/restraints/
parameters: 2637/0/147; goodness-of-fit on F2: 1.045; final R
indices [I > 2s(I)]: R1 = 0.0517, wR2 = 0.1320; R indices (all
data): R1 = 0.0857, wR2 = 0.1517. CCDC: 934387.
˜
IR: v = 3000, 1591, 1461, 1421, 1388, 1345, 1295, 1295, 1201,
1154, 1065, 923, 842, 824, 794, 697 cm21. MS (ESI) calcd for [M
+ Na]+ 373.14, found 373.14. C22H22O4: calcd C 75.41, H 6.33;
found C 75.37, H 6.37%. Crystals were obtained by slow
diffusion of n-pentane into a CH2Cl2 solution of 5. X-ray data
for 49: empirical formula: C22H22O4; formula mass: 350.40;
¯
crystal system: triclinic; space group: P1; unit cell dimensions:
a = 7.8893(2) Å, b = 9.9296(2) Å, c = 11.9272(3) Å; a =
74.7250(10)u, b = 81.3570(10)u, c = 83.1840(10)u; V = 888.04(4)
Å3; Z = 2; density (calcd): 1.310 Mg m23; crystal size: 0.12 6
0.10 6 0.10 mm; h range for data collection: 1.78–30.11u;
reflections collected: 12 010; independent reflections: 4728
[Rint = 0.0184]; refinement method: full-matrix least squares on
F2; data/restraints/parameters: 4728/0/239; goodness-of-fit on
F2: 1.035; final R indices [I > 2s(I)]: R1 = 0.0424, wR2 = 0.1159; R
indices (all data): R1 = 0.0538, wR2 = 0.1246. CCDC: 934377.
3,3999,5,5999-Tetrahydroxy-1,19:49,199:499,1999-quaterphenyl (3)
The reaction was conducted under a nitrogen atmosphere. At
278 uC, to a solution of 7 (700 mg, 1.64 mmol) in freshly
distilled CH2Cl2 (45 mL) was added dropwise a solution of
BBr3 (1 M in CH2Cl2, 7.88 mL). The resulting reaction mixture
was stirred overnight at room temperature. Then, a small
[1,19:39,199-Terphenyl]-3,399,5,599-tetraol (4)
The reaction was conducted under nitrogen. At 278 uC, to a
solution of 49 (0.670 g, 1.9 mmol) in freshly distilled CH2Cl2
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amount of water was carefully added (10 mL). The mixture was
washed with an aqueous Na2CO3 solution (2 M, 400 mL) and
then acidified with HCl 37% until acid pH. The water phase
was extracted three times with diethyl ether and the organic
layers were combined and concentrated under reduced
pressure to afford 3 as a brownish powder (580 mg, 95%).
M.p. > 300 uC. 1H NMR (300 MHz, CD3OD): d = 7.70 (complex,
8H, PhH), 6.60 (d, J = 2.1 Hz, 4H PhH), 6.27 (t, J = 2.1 Hz, 2H,
PhH) ppm. 13C NMR (75 MHz, CD3OD): d 102.5, 108.4, 127.2,
under reduced pressure to afford 5 as a grayish solid (826 mg,
quantitative). M.p. > 300 uC. H NMR (300 MHz, CD3OD): d =
1
7.62 (s, 3H, PhH), 6.61 (d, J = 2.2 Hz, 6H, PhH), 6.29 (t, J = 2.2
Hz, 3H, PhH) ppm. 13C NMR (75 MHz, CD3OD): d = 160.2,
˜
144.8, 144.7, 125.8, 106.9, 103.0 ppm. IR: v = 3282, 1610, 1592,
1512, 1490, 1428, 1335, 1195, 1156, 1002, 825, 686 cm21. MS
(ESI) calcd for [M + H]+ 403.118, found 403.117. C24H18O6
(402.11)?4H2O: calcd C 60.76, H 5.52; found C 60.67, H 5.42%.
Crystals were obtained by slow diffusion of chloroform into an
acetone solution of 5. X-ray data for 5: empirical formula:
C30H32O9 (C24H18O6, 2C3H6O, H2O); formula mass: 536.56;
crystal system: monoclinic; space group: P21/c; unit cell
dimensions: a = 12.0986(4) Å, b = 20.2849(5) Å, c = 11.2091(3)
Å; b = 98.4490(10)u, V = 2721.07(13) Å3; Z = 4; density (calcd):
1.310 Mg m23; crystal size: 0.06 6 0.05 6 0.05 mm; h range
for data collection: 1.98–29.08u; reflections collected: 22 721;
independent reflections: 6951 [Rint = 0.0335]; refinement
method: full-matrix least squares on F2; data/restraints/
parameters: 6951/3/368; goodness-of-fit on F2: 1.001; final R
indices [I > 2s(I)]: R1 = 0.0472, wR2 = 0.1236; R indices (all
data): R1 = 0.0753, wR2 = 0.1403. CCDC: 934378.
˜
139.7, 142.7, 158.8 ppm. IR: v = 3260, 2914, 2830, 1592, 1481,
1344, 1168, 1151, 998, 812, 681 cm21. MS (MALDI-TOF) calcd
for [M]+ 370.121, found 370.2.
59-(3,5-Dimethoxyphenyl)-3,399,5,599-tetramethoxy-
1,19:39,199-terphenyl (59)
The reaction was conducted under a nitrogen atmosphere. A
degassed aqueous solution of Na2CO3 (2 M, 64 mL) was
transferred by cannula to a degassed solution of 1,3,5-
tribromobenzene (1 g, 3.17 mmol) and Pd(PPh3)4 (0.18 g) in
toluene (64 mL). After the cannulation of a solution of 3,5-
dimethoxyphenylboronic acid (2.07 g, 11.4 mmol) in MeOH
(62 mL), the reaction mixture was refluxed overnight. The
mixture was allowed to reach room temperature and extracted
three times with CH2Cl2. The combined organic layers were
dried over MgSO4 and concentrated under reduced pressure.
The crude product was purified over a silica gel chromato-
graphy (CH2Cl2/n-pentane 50/50) to give 59 as a white powder
Tetrakis(39,59-dimethoxy-[1,19-biphenyl]-4-yl)methane (69)
The reaction was conducted under a nitrogen atmosphere. A
degassed aqueous solution of Na2CO3 (2 M, 60 mL) was
transferred by cannula to a degassed solution of tetrakis(4-
bromophenyl)methane (1.26 g, 1.98 mmol) and Pd(PPh3)4 (113
mg) in toluene (60 mL). After the cannulation of a solution of
3,5-dimethoxyphenylboronic acid (1.43 g, 7.92 mmol) in
MeOH (60 mL), the reaction mixture was refluxed for 4 days.
The mixture was allowed to reach room temperature and
extracted three times with CH2Cl2. The combined organic
layers were dried over MgSO4 and concentrated under reduced
pressure. The crude product was purified over a silica gel
chromatography (CH2Cl2/n-pentane, 50/50) to give 69 as a
white solid (1.347 g, 80%). M.p. 270 uC. 1H NMR (300 MHz,
CDCl3): d = 7.55 (d, J = 8.4 Hz, 8H, PhH), 7.43 (d, J = 8.4 Hz, 8H,
PhH), 6.75 (d, J = 2.2 Hz, 8H, PhH), 6.45 (t, J = 2.2 Hz, 4H, PhH)
ppm. 13C NMR (75 MHz, CDCl3): d = 161.6, 146.6, 143.0, 139.1,
1
(1.387 g, 90%). M.p. 204 uC. H NMR (300 MHz, CDCl3): d =
7.78 (s, 3H, PhH), 6.84 (d, J = 2.4 Hz, 6H, PhH), 6.51 (t, J = 2.2
Hz, 3H, PhH), 3.86 (s, 18H, OMe) ppm. 13C NMR (75 MHz,
CDCl3): d = 159.6, 141.5, 140.6, 123.8, 103.9, 97.9, 53.9 ppm. IR:
˜
h = 3000, 2940, 1588, 1463, 1424, 1399, 1325, 1258, 1194, 1150,
1060, 830, 698, 675 cm21. MS (ESI) calcd for [M + H]+ 487.212,
found 487.199. C30H30O6 (486.20): calcd C 74.06, H 6.21; found
C 73.44, H 6.24%. Crystals were obtained by slow diffusion of
n-pentane into a CH2Cl2 solution of 59. X-ray data for 59:
empirical formula: C30H30O6; formula mass: 486.54; crystal
¯
system: triclinic; space group: P1; unit cell dimensions: a =
10.6996(4) Å, b = 10.8140(4) Å, c = 11.0347(4) Å; a = 84.070(2)u, b
= 89.396(2)u, c = 87.954(2)u; V = 1269.10(8) Å3; Z = 2; density
(calcd): 1.273 Mg m23; crystal size: 0.09 6 0.06 6 0.05 mm; h
range for data collection: 1.89–28.00u; reflections collected:
22 207; independent reflections: 5896 [Rint = 0.0387]; refine-
ment method: full-matrix least squares on F2; data/restraints/
parameters: 5896/0/331; goodness-of-fit on F2: 1.053; final R
indices [I > 2s(I)]: R1 = 0.0512, wR2 = 0.1377; R indices (all
data): R1 = 0.0821, wR2 = 0.1573. CCDC: 934381.
˜
131.7, 126.8, 105.5, 99.7, 64.7, 55.8 ppm. IR: v = 2910, 1693,
1591, 1454, 1330, 1146, 1153, 1058, 1014, 814, 668 cm21. MS
(ESI) calcd for [M + Na]+ 887.355, found 887.334. C57H52O8
(864.37): calcd C 79.14, H 6.06; found C 77.99, H 6.24%.
Crystals were obtained by slow diffusion of toluene into a
CH2Cl2 solution of 69. X-ray data for 69: empirical formula:
C
57H52O8; formula mass: 864.99; crystal system: orthorhom-
bic; space group: Pbcn; unit cell dimensions: a = 27.539(2) Å, b
= 7.4754(4) Å, c = 25.6914(19) Å; V = 5289.0(6) Å3; Z = 4; density
(calcd): 1.086 Mg m23; crystal size: 0.06 6 0.05 6 0.02 mm; h
range for data collection: 1.48–28.36u; reflections collected:
38 147; independent reflections: 6409 [Rint = 0.1237]; refine-
ment method: full-matrix least squares on F2; data/restraints/
parameters: 6409/0/299; goodness-of-fit on F2: 1.002; final R
indices [I > 2s(I)]: R1 = 0.0801, wR2 = 0.1819; R indices (all
data): R1 = 0.1466, wR2 = 0.2031. CCDC: 934382.
59-(3,5-Dihydroxyphenyl)-3,399,5,599-tetrahydroxy-
1,19:39,199-terphenyl (5)
The reaction was conducted under a nitrogen atmosphere. At
278 uC, to a solution of 59 (1 g, 2.21 mmol) in freshly distilled
CH2Cl2 (20 mL) was added dropwise a solution of BBr3 (1 M in
CH2Cl2, 14.8 mL). The resulting reaction mixture was stirred
overnight at room temperature. Then, a small amount of water
was carefully added (40 mL). The mixture was washed with an
aqueous Na2CO3 solution (2 M, 250 mL) and then acidified
with HCl 37% until acid pH was reached. The precipitate
formed was filtered, washed with an excess of water and dried
Tetrakis(39,59-dihydroxy-[1,19-biphenyl]-4-yl)methane (6)
The reaction was conducted under a nitrogen atmosphere. At
278 uC, to a solution of 69 (900 mg, 1.04 mmol) in freshly
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distilled CH2Cl2 (60 mL) was added dropwise a solution of
BBr3 (1 M in CH2Cl2, 10 mL). The resulting reaction mixture
was stirred two days at room temperature. Then, a small
amount of water was carefully added (40 mL). The mixture was
washed with an aqueous Na2CO3 solution (2 M, 100 mL) and
then acidified with HCl 37% until acid pH was reached. The
solid was recovered by filtration and dried under reduced
pressure to afford 6 as a brownish powder (750 mg, 95%). M.p.
´
A. Ramsahye, F. Balas, M. Vallet-Regı, M. Sebban,
´
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1
> 300 uC. H NMR (300 MHz, CD3OD): d = 7.47 (d, J = 8.4 Hz,
5974.
8H, PhH), 7.34 (d, J = 8.5 Hz, 8H, PhH), 6.56 (d, J = 2.2 Hz, 8H,
PhH), 6.24 (t, J = 2.2 Hz, 4H, PhH) ppm. 13C (75 MHz, CD3OD):
d = 160.4, 147.7, 144.5, 140.8, 132.9, 127.5, 107.0, 103.1, 65.9
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˜
ppm. IR: v = 3334, 1714, 1596, 1487, 1337, 1197, 1148, 998, 814,
669 cm21. MS (MALDI-TOF) calcd for [M]+ 752.241, found
752.5. C49H36O8 (752.24)?5H2O: calcd C 69.82, H 5.50; C 69.29,
H 4.98%. Crystals were obtained by slow diffusion of toluene
into an ethyl acetate solution of 6. X-ray data for 6: empirical
formula (the structure was solved using the SQUEEZE
command): C49H36O8; formula mass: 752.78; crystal system:
monoclinic; space group: C2/c; unit cell dimensions: a =
32.8482(13) Å, b = 7.0555(2) Å, c = 25.7963(18) Å; b =
128.8150(10)u, V = 4658.3(4) Å3; Z = 4; density (calcd): 1.073
Mg m23; crystal size: 0.07 6 0.05 6 0.05 mm; h range for data
collection: 1.59–28.29u; reflections collected: 21 732; indepen-
dent reflections: 5685 [Rint = 0.0343]; refinement method: full-
matrix least squares on F2; data/restraints/parameters: 5685/0/
262; goodness-of-fit on F2: 1.052; final R indices [I > 2s(I)]: R1 =
0.0609, wR2 = 0.1757; R indices (all data): R1 = 0.0871, wR2 =
0.1910. CCDC: 934376.
ˆ
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Acknowledgements
´
This work was performed at the Universite de Strasbourg with
public funds allocated by the Centre National de la Recherche
Scientifique (CNRS) and the Ministere de l’Enseignement
`
´
Superieur et de la Recherche.
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