Molecular tectonics: Generation of 1-D interdigitated and 2-D interwoven helical silver coordination networks by oligoethylene glycol based tectons bearing two benzonitrile moieties

Article abstract of DOI:10.1039/b611415f

Ligands based on oligoethylene glycol units bearing at their extremities benzonitrile groups behave in the crystalline phase as tectons and lead in the presence of silver cation to different coordination networks. Depending on the number of glycol units, 1-D stair type or 1-D interdigitated and 2-D interwoven architectures composed of helical strands are obtained. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.

Full text of DOI:10.1039/b611415f

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Molecular tectonics: generation of 1-D interdigitated and 2-D interwoven
helical silver coordination networks by oligoethylene glycol based tectons
bearing two benzonitrile moietiesw
Julien Bourlier, Mir Wais Hosseini,* Jean-Marc Planeix and Nathalie Kyritsakas
Received (in Durham, UK) 7th August 2006, Accepted 6th November 2006
First published as an Advance Article on the web 7th December 2006
DOI: 10.1039/b611415f
Ligands based on oligoethylene glycol units bearing at their extremities benzonitrile groups
behave in the crystalline phase as tectons and lead in the presence of silver cation to different
coordination networks. Depending on the number of glycol units, 1-D stair type or 1-D
interdigitated and 2-D interwoven architectures composed of helical strands are obtained.
Introduction
Results and discussion
For some time now, we have been active in a domain called
molecular tectonics.1–4 This approach deals with the design
and formation of molecular networks and is based on iterative
molecular recognition processes between construction units or
tectons.5,6 The concepts and strategies developed in this area
may be applied to the design and generation of coordination
networks.3,6,7 The latter, also called coordination polymers,8
are infinite metallo-organic architectures generated upon mu-
tual bridging between organic tectons and metal centres. These
molecular assemblies are usually obtained in the crystalline
phase under self-assembly conditions. For ca. two decades,
this class of architecture has been attracting constant attention
and many examples have been reported.8–19 A major challenge
in this area remains the fine understanding, both in terms of
connectivity and topology, of the subtle factors governing the
formation of these structures. Currently, we are rather far
from that level and the majority of cases reported are the
result of mixing and observing. In order to get a better insight,
we believe that systematic studies based on incremental
changes in the structure of the organic ligand and/or in the
nature of the metal centre are of prime importance. Pursuing
our efforts to better understand the formation of coordination
networks and to design and generate new metallo-organic
frameworks (for some recent publications see refs. 20–25) we
have undertaken a systematic study on the design of construc-
tion units combining both primary and secondary coordina-
tion sites.26,27
Design of the tectons 1–5
In the continuation of our systematic effort to better under-
stand the parameters governing the formation of coordination
networks, we have explored the possibility of combining
primary and secondary coordination sites within the structure
of tectons. For this purpose, tectons 1–5 (Scheme 1) were
designed. These molecules are based on oligoethylene glycol
fragments bearing at their extremities benzonitrile groups.
Concerning the benzonitrile group as coordination site, it is
worth noting that in order to increase its coordination ability,
the junction between the aryl group and the oligoethylene
glycol unit is ensured, at the position 4 with respect to the
nitrile moiety, by an ether link. This should indeed increase the
electronic density on the nitrile group through electronic
delocalisation. Dealing with the oligoethylene glycol connect-
ing fragment, owing to its conformational flexibility, depend-
ing on the number of glycol introduced, this spacer may adopt
a curved arrangement thus offering a semi circular disposition
of oxygen atoms capable of surrounding the metal cation.
Thus, one may regard these ligands as construction units
offering two nitrile groups as primary coordination sites and
oxygen atoms involved in their junctions as secondary binding
In the present contribution we expand on this idea and
report on the synthesis of tecton 1–5 as well as on the
structural investigations of a variety of 1- and 2-D coordina-
tion networks obtained in the solid state in the presence of
silver salts.
Laboratoire de Chimie de Coordination Organique, UMR CNRS
´
7140, Universite Louis Pasteur, F-67000 Strasbourg, France. E-mail:
hosseini@chimie.u-strasbg.fr
w The HTML version of this article has been enhanced with additional
colour images.
Scheme 1
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sites. The designed principle used here is flexible and allows,
while keeping the number and nature of the primary sites
fixed, to vary the number and location of the secondary
interaction sites.
Choice of the metal
Concerning the metal centre, Ag+ cation was selected because
of its spherical nature and thus rather loose coordination
requirements both in terms of coordination number and
geometry. A further reason why silver cation was chosen is
because the formation of Ag–N and Ag–O bonds is reversible
and thus well suited for the formation, by self-assembly
processes, of periodic architectures in the solid state. Since
compounds 1–5 are neutral tectons, the silver cation must be
associated with a counter ion in the solid state. In order to
avoid binding competition between tectons 1–5 and the anion
À
À
for silver cation, AsF6 and SbF6 anions were chosen
because of their rather weakly coordination propensity.
Synthesis of tectons 1–5
The preparation of compounds 1–5 was straightforward and
based on the condensation of 4-cyanophenol 6 with commer-
cially available 1,2-dibromoethane 7 for the synthesis of 1 or
ditosylate derivatives 8–11 for the preparation of 2–5 in
refluxing CH3CN in the presence of K2CO3 (see experimental
section).
Structural investigations
Crystals of both compounds 1 and 2 were obtained and their
solid state structures have been investigated. All five com-
pounds 1–5 have been combined with AgAsF6 and AgSbF6
salts. However, although crystals have been obtained in the
case of compounds 1 and 3–5, for compound 2 no crystalline
material could be obtained.
Free tectons 1 and 2
The solid state structure of the free tecton 1 was investigated
by X-ray diffraction on single crystal (monoclinic, space group
P2(1)/n). The structural determination (see Table 1) revealed
that for the compound 1 there is an inversion centre at the
midpoint of the central C–C bond and the ethylene glycol
fragment adopts the anti conformation with the OCCO dihe-
dral angle of 1801 (Fig. 1). The two benzonitrile groups
connected to the ethylene glycol unit through ether junctions
(dPhC–O = 1.366 A, dC–O = 1.432 A, OCO angle = 117.91) are
perfectly coplanar. The nitrile moiety (dCN = 1.151 A) is
almost linear to the phenyl ring with the CCN angle of 179.21.
The consecutive compounds 1 are arranged parallel to each
other with 3.97 A distance between the phenyl rings centroids.
The solid state structure of the free tecton 2 was investigated
by X-ray diffraction on single crystal (monoclinic, space group
C2/c). The structural determination (see Table 1) revealed that
for 2 the central oxygen atom lies on a twofold axis with the
diethylene glycol fragment adopting the gauche conformation
(OCCO dihedral angle of À68.01 and À68.21) (Fig. 2). The two
benzonitrile groups connected to the diethylene glycol unit
through ether junctions (dPhC–O = 1.359 A, dC–O = 1.434 A,
OCO angle = 119.71) are divergently oriented and the com-
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Fig. 1 The solid state structure of 1 showing the anti conformation
adopted by the ethylene glycol moiety and the packing of consecutive
units. For the sake of clarity, H atoms are not represented. For bond
distances and angles see text.
Fig. 3 A portion of the 1-D stair type coordination networks formed
between 1 and Ag+ cation showing the cyclic fragment and the
positioning of the anions. For sake of clarity, H atoms are not
represented. For bond distances and angles see text.
pound 2 presents a bent type structure. The nitrile moiety
(dCN = 1.148 A) is slightly bent with respect to the phenyl
group with the CCN angle of 176.61. The consecutive com-
pounds 2 are arranged parallel to each other with 4.60 A
distance between the phenyl rings centroids.
Considering these two construction units and the silver
cation offering a coordination number of three with a dis-
torted trigonal geometry, the observed cationic 1-D stair type
network may be described in two different manners (Fig. 3–5).
The interconnection of both conformers through silver nitro-
gen bonds (Ag–N distances of 2.186 A and 2.193 A, NAgN
angle of 152.01) leads to the formation of a centrosymmetric
[4 + 4] metallamacrocycle (Fig. 3 and Fig. 5 left). The
interconnection (Fig. 4 and Fig. 5 left), again through Ag–N
bonds (Ag–N distances of 2.345 A and 2.193 A, NAgN angles
of 98.51 and 108.81) of the metallamacrocycles by the gauche
conformer leads to the formation of the final architecture. It is
worth noting that no interactions between the oxygen atoms of
the glycol units and the silver cation is observed implying that
the oxygen atoms do not play the role of secondary interaction
sites. This might be due to geometric (restricted length of the
spacer) and electronic (electronic delocalisation on the nitrile
group) reasons.
Coordination network formed between tecton 1 and silver cation
Upon combining the tecton 1 with AgAsF6 or AgSbF6,
crystalline materials were obtained (see experimental section).
The X-ray diffraction studies on single crystals revealed that
both combinations are isomorphous (see Table 1). Thus, here
we only describe the structure of 1-AgSbF6, given that for the
other structure only minute differences in bond distances and
ꢀ
angles are observed. The crystal (triclinic, P1) is only com-
À
posed of the tecton 1, Ag+ cation and SbF6 anion with a
1/Ag+ ratio of 3/2. No solvent molecules are present in the
lattice. Concerning the organic tecton 1, interestingly, the
latter adopts two different conformations (Fig. 3). One lying
about an inversion centre with the glycol unit (dC–O = 1.432
A, dC–C = 1.515 A) in anti conformation (OCCO dihedral
angle of 180.01) as in the case of the free compound 1
mentioned above and the other in a general position with
the glycol unit (dC–O = 1.400 A, dC–C = 1.511 A) adopting the
gauche conformation (OCCO dihedral angle of 87.61). The
conformer’s ratio anti/gauche is 2/3. Consequently, compound
1 offers two geometrically different tectons (linear for the anti
conformer and bent for the gauche conformer) presenting two
sets of two nitrile groups (dC–N = 1.142 A and 1.147 A for anti
and gauche conformers, respectively).
The other possible way to describe the stair type 1-D net-
work is to consider first the formation of a 1-D zigzag type
arrangement resulting from the interconnection of tectons 1 in
gauche conformation by silver cations (Fig. 5 right) and, in
a second step, their interconnection by tectons 1 in anti
conformation.
Fig. 2 A portion of the solid state structure of 2 showing the gauche
conformation adopted by the ethylene glycol moieties and the packing
of consecutive units. For sake of clarity, H atoms are not represented.
For bond distances and angles see text.
Fig. 4 A portion of the 1-D stair type coordination networks formed
between 1 and Ag+ cation showing the interconnection of the cyclic
units by the tecton 1. For sake of clarity, H atoms and anions are not
represented. For bond distances and angles see text.
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Fig. 6 A portion of the 1-D interdigitated network formed between 3
and Ag+. The interdigitation between the two helical strands (a) of the
opposite handedness is due to the interactions between the oxygen
atoms of the triethylene glycol units of the tecton 3 adopting a curved
conformation within one strand and metal cations belonging to the
other strand (b and c). For sake of clarity, carbon atoms belonging to
different strands are differentiated by colour and H atoms and anions
are not represented. For bond distances and angles see text.
Fig. 5 Schematic representation of the two possible descriptions for
the formation of the stair type architecture observed when the tecton 1
was combined with silver cation.
Although the 1-D arrangement presents large cyclic type
cavities, the latter are not empty but occupied by SbF6À anions
for which the Sb cation lies on an inversion centre (Fig. 3).
Consequently, no entanglement is observed. No specific inter-
action between the anions and the cationic part is detected.
The 1-D networks are packed in a parallel fashion.
the two peripheral units. Thus, the coordination number for
the cation is six and its coordination geometry is a severely
distorted octahedron. The distance between two consecutive
silver cations belonging to different interconnected strands is
10.106 A. For the observed duplex architecture, the aryl
groups of the two strands are arranged in the parallel fashion
with 3.881 A distance between their centroids (Fig. 6c). It is
worth noting that the interconnection of the two helical
strands does not lead to formation of an interwoven arrange-
ment but to an interdigitated architecture. Indeed, the two
strands do not cross each other (Fig. 7). The 1-D networks arÀe
packed in parallel and the empty space is occupied by AsF6
anions which were found to be disordered. No specific inter-
actions between the anions and the cationic part of the
structure could be detected.
Coordination network formed between tecton 3 and silver cation
The mixing of the tecton 3 with AgAsF6 leads to the formation
of crystalline materials (see experimental section) that was
analysed by X-ray diffraction on single crystals (see Table 1).
+
ꢀ
The crystal (triclinic, P1) is composed of compound 3, Ag
cation and AsF6À anion with a 3/Ag+ ratio of 1/1. No solvent
molecules are present in the lattice. Dealing with the organic
tecton 3, among the three ethylene glycol fragments, the two
oxygen atoms of the central unit are disordered over two
positions. All three ethylene glycol units (C–O distance in the
range of 1.422–1.484 A, C–C distance in the range of
1.487–1.511 A) adopt the gauche conformation. Consequently,
the spacer unit connecting the two benzonitrile groups
(dC–N = 1.124 A and 1.150 A) adopts a helical conformation
offering a pocket bearing four oxygen atoms (Fig. 6a). The
interconnection, through Ag–N bond (Ag–N distances of
2.225 A and 2.238 A) of consecutive tectons 3 by the silver
cation (NAgN angle of 133.21) leads to the formation of a 1-D
helical strand (Fig. 6a). The distance between two consecutive
silver cations within the same strand is 15.58 A.
Coordination network formed between tecton 4 and silver cation
Upon combining the tecton 4 with either AgAsF6 or AgSbF6,
again crystalline materials were obtained (see experimental
section) and analysed by single crystals X-ray diffraction. As in
the case of 1 mentioned above, the structural investigation on
both crystals revealed that they are isomorphous (see Table 1).
Again here we only describe the structure of 4-AgSbF6 since
for the other structure only small differences in bond distances
Interestingly, two helical strands of opposite chirality form
an achiral double strand 1-D network (Fig. 6b). The driving
force for the formation of this peculiar duplex is due to silver
oxygen interactions. Indeed, all four oxygen atoms of triethy-
lene glycol units of one strand are involved in interactions with
the silver cation belonging to the other strand with two short
Ag–O distances of ca 2.5 A for the disordered central unit and
two long Ag–O distances (dAg–O = 2.789 A and 2.897 A) for
Fig. 7 A schematic representation of the interdigitation of two helical
strands with opposite helicity leading to a 1-D achiral architecture.
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identical to the one described above for 3 (Fig. 7). The 1-D
networks are packed in a parallel fÀashion and the empty space
is occupied by disordered SbF6 anions with no specific
interactions with the cationic part of the structure.
Coordination network formed between tecton 5 and silver cation
The combination of the tecton 5 with AgSbF6 affords also
crystalline material (see experimental section). The structural
study by X-ray diffraction on single crystals (see Table 1)
revealed that the crystal (orthorhombic, P212121) is composed
of compound 5, Ag+ cation and SbF6 anion with a 5/Ag+
À
ratio of 1/1. For the tecton 5, as for compound 4, the
pentaethylene glycol spacer is not disordered. As for tectons
3 and 4, all ethylene glycol units (C–O distance in the range of
1.400–1.435 A, C–C distance in the range of 1.475–1.500 A)
adopt the gauche conformation (OCCO dihedral angles of
À67.21, À68.81, 69.31, À59.01, À66.91). The linker between the
two benzonitrile groups (dC–N = 1.138 A and 1.139 A) adopts
a loop type conformation (Fig. 9a). The interconnection of
tectons 5 by silver cations (NAgN angle of 128.71) through
Ag–N bond (Ag–N distances of 2.182 A and 2.192 A) leads to
the formation of a 1-D helical strand (Fig. 9a). Within this
strand the distance between two consecutive silver cations is
12.87 A.
Fig. 8 A portion of the 1-D interdigitated network formed between 4
and Ag+. The interdigitation between the two helical strands (a) of the
opposite handedness is due to the interactions between the O atoms of
the tetraethylene glycol units of the tecton 4 adopting a loop type
conformation within one strand and metal cations belonging to other
strand (b and c). For sake of clarity, carbon atoms belonging to
different strands are differentiated by colour and H atoms and anions
are not represented. For bond distances and angles see text.
In marked contrast to the other two above discussed
structures obtained for tectons 3 and 4, here, instead of an
achiral 1-D duplex arrangement, a chiral 2-D interwoven
architecture is obtained (Fig. 9b). Indeed, all consecutive
helical strands of the same handedness in the same plane
and angles are observed. As in the case of 3 mentioned above,
the crystal (monoclinic, P2(1)/Àc) is only composed of com-
pound 4, Ag+ cation and SbF6 anion with a 4/Ag+ ratio of
1/1. In contrast to the previous structure, the tetraethylene
glycol moieties of the tecton 4 are not disordered. All glycol
units (C–O distance in the range of 1.387–1.436 A, C–C
distance in the range of 1.488–1.502 A) adopt the gauche
conformation (OCCO dihedral angles of 58.71, À63.31,
À76.01 and À79.31) leading to a helical turn (Fig. 8a) for the
tetraethylene glycol spacer connecting the two benzonitrile
groups (dC–N = 1.144 A and 1.148 A). Once again, the
interconnection of consecutive tectons 4 by the silver cation
(NAgN angle of 110.31) through Ag–N bond (Ag–N distances
of 2.249 A and 2.256 A) leads to the formation of a 1-D helical
strand (Fig. 8a). The distance between two consecutive silver
cations within the same strand is 13.86 A.
As in the case of 3, two helical strands of the opposite
chirality form an achiral double strand 1-D network (Fig. 8b).
This arrangement also results from silver–oxygen interactions.
Among the five oxygen atoms of tetraethylene glycol units of
one strand three of them are involved in interactions with the
silver cation belonging to the other strand with Ag–O distance
in the range of 2.504 A to 2.607 A. The Ag–O distances for the
remaining two oxygen atoms are 3.252 A and 3.800 A. The
coordination number for the cation is five and its coordination
geometry is a strongly distorted square based pyramidal. The
distance between two consecutive silver cations belonging to
different interconnected strands is 10.62 A. The aryl groups of
the two strands are again arranged in the parallel fashion with
a shorter (3.740 A) distance between their centroids (Fig. 8c).
The interdigitated arrangement of the two helical strands is
Fig. 9 A portion of the 2-D interwoven chiral network formed
between 5 and Ag+. The entanglement between consecutive helical
strands (a) of the same handedness is due to the interactions between
the O atoms of the pentaethylene glycol units of 5 adopting a loop type
arrangement within each strands and metal cations belonging to
consecutive strands (b). For sake of clarity, carbon atoms belonging
to different strands are differentiated by colour and H atoms and
anions are not represented. For bond distances and angles see text.
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coordination sites as well as other metal cations is currently
under investigation.
Experimental section
Synthesis
Compound 1. 4-Cyanophenol 6 (2.76 g, 23.2 mmol) and
K2CO3 in excess (6.41 g, 46.4 mmol) were dissolved in
acetonitrile (150 mL). The mixture was stirred before 1,2-
dibromoethane 7 (2.18 g, 11.6 mmol) was added. The mixture
was refluxed overnight. The solvent was removed under
reduced pressure. A saturated aqueous potassium carbonate
(50 mL) solution was added to the residue and the organic
mixture was extracted with CH2Cl2 (3 Â 50 mL). Organic
layers were combined and the solvent was removed. The
residue thus obtained was purified by column chromatography
(ethyl acetate/cyclohexane: 40/60). The pure compound 1 was
Fig. 10 A schematic representation of the entanglement of consecu-
tive helical strands of the same helicity leading to a 2-D interwoven
chiral architecture.
interact with each other through silver oxygen interactions.
Among the six oxygen atoms of pentaethylene glycol units of
one strand, three of them are involved in interactions with the
silver cation belonging to the next strand with Ag–O distances
of 2.621 A, 2.667 A and 2.710 A. The Ag–O distances for the
remaining three oxygen atoms are 3.010 A, 3.176 A and 4.871
A. The coordination number for the silver cation is five. The
distance of 7.476 A between two consecutive silver cations
belonging to neighboring strands is considerably shorter than
those observed in the case of 3 or 4. The crystal is chiral
(P212121 space group) and made by packing of homochiral
2-D interwoven networks (Fig. 10). The SbF6À anions are not
disordered and occupy the empty space between 2-D net-
works. Once again, no specific interaction between the cationic
part of the structure and anions is observed. It is worth noting
that although the crystal studied is chiral, it is reasonable to
assume that crystals with the opposite chirality must be
present in the mixture of crystals (racemic mixture).
1
obtained as a white solid in 76% yield. Mp = 204 1C. H-
NMR (CDCl3, d, ppm): 4.39 (s, 4H, CH2), 7.00 (d, 4H, arom,
J = 9 Hz), 7.61 (d, 4H, arom, J = 9 Hz). 13C-NMR (CDCl3,
d, ppm): 69.9, 104.1, 115.1, 119.3, 134.1, 161.8. Calculated for
C16H12N2O2 (264.28): C 72.72, H 4.58, N 10.60; found C
72.20, H 4.59, N 10.19%.
Compound 2. 4-Cyanophenol 6 (2 g, 16.7 mmol) and K2CO3
(4.64 g, 33.4 mmol) were dissolved in acetonitrile (150 mL). To
the stirred mixture, compound 8 (3.47 g, 8,39 mmol) was
added. The solution was heated to reflux overnight. Solvent
was removed under reduced pressure. A saturated aqueous
potassium carbonate (50 mL) solution was added to the
residue and the organic mixture was extracted with CH2Cl2
(3 Â 50 mL). The organic layers were combined and the
solvent was removed. The residue was purified by column
chromatography (ethyl acetate/cyclohexane: 40/60). The pure
compound 2 was obtained as a white solid in 74% yield. Mp
= 135 1C. 1H-NMR (CDCl3, d, ppm): 3.94 (t, 4H, CH2,
J = 4.8 Hz), 4.19 (t, 4H, CH2, J = 4.8 Hz), 6.95 (d, 4H, arom,
J = 9 Hz), 7.57 (d, 4H, arom, J = 9 Hz). 13C-NMR (CDCl3,
d, ppm): 67.7, 69.7, 104.3, 115.3, 119.1, 134.0, 161.9. Calcu-
lated for C18H16N2O3 (308.33): C 70.12, H 5.23, N 9.09; found
C 69.85, H 5.205, N 8.98%.
Conclusion
Compounds 1 and 3–5 composed of oligoethylene glycol units
and two benzonitrile groups behave as tectons when combined
with silver cation and lead to the formation of coordination
networks in the crystalline phase. The type of architecture
obtained is correlated to the number of glycol units connecting
the two benzonitrile groups. In the presence of silver cation
tecton 1, based on the ethylene glycol unit, leads mainly to the
formation of a stair type 1-D network with no interaction
between the oxygen atoms of the glycol unit and the metal
cation. This absence of interactions is probably due to geo-
metric (restricted length of the spacer) and electronic (electro-
nic delocalisation on the nitrile group) reasons. In marked
contrast and as expected from their design, for tectons 3–5,
based on tri-, tetra- and pentaethylene glycol fragments,
respectively, both nitrile groups and oligoethylene fragments
act as primary and secondary coordination sites, respectively
and participate in the binding of silver cation. All three tectons
3–5 lead to the formation of helical strands. Interestingly, for
both tectons 3 and 4 the 1-D network obtained results from
the interdigitation of two helical strands of opposite helicity
through the interactions of oxygen atoms belonging to one
strand with the cation belonging to the other strand. In the
case of tecton 5, consecutive helical strands of the same
handedness are interwoven through glycol-metal type interac-
tions. The overall architecture is a chiral 2-D network. Based
on the same strategy, the use of other primary and secondary
Compound 3. 4-Cyanophenol 6 (2 g, 16.7 mmol) and K2CO3
(4.64 g, 33.4 mmol) were dissolved in acetonitrile (150 mL).
The mixture was stirred before compound 9 (3.84 g, 8.39
mmol) was added. The solution was refluxed overnight. Sol-
vent was removed under vacuum. The residue was suspended
in CH2Cl2 (50 mL) and stirred before the solid was removed by
filtration. This operation was repeated twice. The solvent was
evaporated affording the compound 3 as a light yellow solid in
1
84% yield. Mp = 119 1C. H-NMR (CDCl3, d, ppm): 3.74
(s, 4H, CH2), 3.87 (t, 4H, CH2, J = 4.8 Hz), 4.16 (t, 4H, CH2,
J = 4.8 Hz), 6.95 (d, 4H, arom, J = 9 Hz), 7.57 (d, 4H, arom,
J = 9 Hz). 13C-NMR (CDCl3, d, ppm): 67.7, 69.5, 70.9, 104.2,
115.3, 119.1, 134.0, 162.0. Calculated for C20H20N2O4
(352.38): C 68.17, H 5.72, N 7.95; found C 68.02, H 5.69, N
7.87%.
Compound 4. 4-Cyanophenol 6 (597 mg, 5.01 mmol) and
K2CO3 (1.4 g, 10.1 mmol) were dissolved in acetonitrile
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(50 mL). The mixture was stirred and compound 10 (1.26 g,
2.51 mmol) was added. The solution was heated to reflux
overnight. Solvent was removed under reduced pressure. The
residue was suspended in CH2Cl2 (25 mL) and stirred before
the solid was removed by filtration. This operation was
repeated twice. The solvent was evaporated to dryness afford-
ing the desired compound 4 as a white solid in obtained in
93% yield. Mp = 52 1C. 1H-NMR (CDCl3, d, ppm): 3.68
(m, 8H, CH2), 3.85 (t, 4H, CH2, J = 4.8 Hz), 4.15 (t, 4H, CH2,
J = 4.8 Hz), 6.95 (d, 4H, arom, J = 9 Hz), 7.56 (d, 4H, arom,
J = 9 Hz). 13C-NMR (CDCl3, d, ppm): 67.8, 69.4, 70.7, 70.9,
104.1, 115.3, 119.2, 134.0, 162.1. Calculated for C22H24N2O5
(396.44): C 66.65, H 6.10, N 7.07; found C 66.85, H 6.25, N
6.93%.
(0.75 mL) of silver salt was added (AgSbF6: 3.75 mg; AgAsF6
3.75 mg). The tubes were sealed with a stopper and kept in the
dark at rt. After two weeks, colourless crystals were obtained.
5-AgSbF6. In a crystallisation tube (height = 15 cm,
diameter = 4 mm) a 1,2-dichloroethane solution (0.75 mL)
of 5 (3.75 mg) was layered with a 50/50 1,2-dichloroethane/
EtOH solution (0.75 mL) before an EtOH solution (0.75 mL)
of AgSbF6 (3.75 mg) was added. The tube was sealed with a
stopper and kept in the dark at rt. After two weeks, colourless
crystals were obtained.
Crystallography. Data were collected at 173(2) K on a
Bruker SMART CCD Diffractometer equipped with an
Oxford Cryosystem liquid N2 device, using graphite-mono-
chromated Mo Ka radiation (see Table 1). For all structures,
diffraction data were corrected for absorption and structural
determination was achieved using SHELXS-97. All hydrogen
atoms have been calculated except those connected to disor-
dered atoms. CCDC 624584–624587 contains the supplemen-
tary crystallographic data for this paper. For crystallographic
data in CIF or other electronic format see DOI: 10.1039/
b611415f
Compound 5. 4-Cyanophenol 6 (435 mg, 3.65 mmol) and
K2CO3 (1 g, 7.24 mmol) were dissolved in acetonitrile (50 mL).
The mixture was stirred and compound 11 (1 g, 1.83 mmol)
was added. The solution was refluxed overnight. Solvent was
removed under vacuum. The residue was suspended in CH2Cl2
(25 mL) and stirred before the solid was removed by filtration.
This operation was repeated twice. The solvent was evapo-
rated to dryness leaving the pure compound 5 as a white solid
in 82% yield. Mp = 44 1C. 1H-NMR (CDCl3, d, ppm):
3.61–3.73 (m, 12H, CH2), 3.85 (t, 4H, CH2, J = 4.8 Hz),
4.15 (t, 4H, CH2, J = 4.8 Hz), 6.94 (d, 4H, arom, J = 9 Hz),
7.56 (d, 4H, arom, J = 9 Hz). 13C-NMR (CDCl3, d, ppm):
67.8, 69.4, 70.6, 70.9, 104.1, 115.3, 119.2, 134.0, 162.1. Calcu-
lated for C24H28N2O6 (440.49): C 65.44, H 6.41, N 6.36; found
C 65.18, H 6.29, N 6.33%.
Acknowledgements
Universite Louis Pasteur, Institut Universitaire de France, the
´
CNRS and the Ministry of Education and Research
are acknowledged for financial support and for scholarship
to J. B.
Crystallisation conditions
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