Molecular assemblies from imidazolyl-containing haloalkenes and haloalkynes: Competition between halogen and hydrogen bonding

Article abstract of DOI:10.1002/chem.200601508

The structural characterization of molecular assemblies constructed from imidazolyl-containing haloalkenes and haloalkynes is reported. 1-(3-Iodopropargyl)imidazole (2) and 1-(2,3,3-triiodoallyl)imidazole (5) were synthesized from 1-propargylimidazole (1). In the solid state, these wholly organic modules self-assemble through N...I halogen-bonding interactions, thus giving rise to polymeric chains. The N...I interaction observed in 2 (d(N...I) = 2.717 A, spherical angle sign C(sp)-I...N = 175.8°) is quite strong relative to previously reported data. The N...I interaction in 5 (d(N...I) = 2.901 A, spherical angle signC(sp ²)-I...N = 173.6°) is weaker, in accordance with the order C(sp)-X←base>C(sp²)-X←base. Compound 5 was found to give a 1:1 cocrystal 4 with morpholinium iodide (6). In the X-ray crystal studies of 4, N...I halogen-bonding interactions similar to those observed in 5 were shown not to be present, as the arrangement of the molecules is governed by two interwoven hydrogenbonding networks. The first network involves N-H...O interactions between nearby morpholinium cations, and the second network is based on N-H...N hydrogen bonding between morpholinium cations and imidazolyl groups. Both hydrogen-bonding schemes are charge-assisted. Halogen bonding is not completely wiped out, however, as the triiodoalkene fragment forms a halogen bond with an iodide anion in its vicinity (d(I...I) = 3.470 A, spherical angle signC(sp²)-I...I = 170.7°). X-ray crystal studies of 6 show a completely different arrangement from that observed in 4, namely, N-H...O interactions are not present. In crystalline 6, morpholinium cations are interconnected through C-H...O bridges (d(H...O)=2.521 and 2.676 A), and the NH₂⁺ groups interact with nearby iodide anions (d(H...I)=2.633 and 2.698 A).

Full text of DOI:10.1002/chem.200601508

DOI: 10.1002/chem.200601508
Molecular Assemblies from Imidazolyl-Containing Haloalkenes and
Haloalkynes: Competition between Halogen and Hydrogen Bonding
[
a]
[a]
[a]
[b]
Karim Bouchmella, Bruno Boury, Sylvain G. Dutremez,* and Arie van der Lee
!
Abstract: The structural characteriza-
tion of molecular assemblies construct-
ed from imidazolyl-containing haloal-
kenes and haloalkynes is reported. 1-
X
base. Compound 5 was found to
hydrogen bonding between morpholini-
um cations and imidazolyl groups. Both
hydrogen-bonding schemes are charge-
assisted. Halogen bonding is not com-
pletely wiped out, however, as the
triiodoalkene fragment forms a halo-
give a 1:1 cocrystal 4 with morpholini-
um iodide (6). In the X-ray crystal
studies of 4, N···I halogen-bonding in-
teractions similar to those observed in
5 were shown not to be present, as the
arrangement of the molecules is gov-
erned by two interwoven hydrogen-
bonding networks. The first network in-
volves N-H···O interactions between
nearby morpholinium cations, and the
second network is based on N-H···N
(
(
3-Iodopropargyl)imidazole (2) and 1-
2,3,3-triiodoallyl)imidazole (5) were
synthesized from 1-propargylimidazole
1). In the solid state, these wholly or-
gen bond with an iodide anion in its vi-
2
(
cinity (d
A
H
R
U
G
A
H
R
U
G
ganic modules self-assemble through
N···I halogen-bonding interactions, thus
giving rise to polymeric chains. The
170.78). X-ray crystal studies of 6 show
completely different arrangement
a
from that observed in 4, namely, N-
H···O interactions are not present. In
crystalline 6, morpholinium cations are
N···I interaction observed in
(N···I)=2.717 Š, aC(sp)-I···N=
75.88) is quite strong relative to previ-
ously reported data. The N···I interac-
2
(
d
ACHTREUNG
1
interconnected
bridges (d(H···O)=2.521 and 2.676 Š),
and the NH2 groups interact with
through
C-H···O
Keywords: crystal engineering ·
donor–acceptor systems · halogen
bonding
AHCTREUNG
2
+
tion in 5 (d
A
C
H
T
R
E
U
N
G
(N···I)=2.901 Š, aC(sp )-
A
H
R
U
G
·
hydrogen bonds
·
I···N=173.68) is weaker, in accordance
nearby iodide anions (d(H···I)=2.633
A
H
R
U
self-assembly
!
2
with the order C(sp)-X base>C
A
H
R
U
G
and 2.698 Š).
Introduction and Background
tion for the synthesis of wholly organic architectures is their
topological resemblance to existing inorganic systems; there-
fore, it is often found that the former exhibit properties sim-
ilar to those of the latter. For example, wholly organic struc-
Currently, an intense research effort is being devoted to the
construction of wholly organic architectures with controlled
topologies by use of noncovalent bonding. This modular ap-
proach circumvents the construction of a large number of
covalent bonds, thus simplifying the synthetic task and mini-
mizing the chance of side reactions. This activity encompass-
es several areas of research, such as supramolecular chemis-
try, crystal engineering, and materials science. One motiva-
[1,2]
[3]
tures are capable of assembling into 2D
and 3D net-
works that resemble structurally and functionally pillared
clays and zeolites.
These structures are held together by an appropriate syn-
thon which, very often, relies on hydrogen bonding or
charge-assisted hydrogen bonding. Among the most fre-
quently used moieties with hydrogen-bonding capabilities,
pyridine, its analogues, and carboxylates occupy the first
rank. Another building block that has become quite popular
in recent years is imidazole, and the chemistry of this het-
erocycle is now becoming quite rich and versatile. Indeed,
many facets of imidazole chemistry resemble aspects of pyri-
dine chemistry. Just like pyridine, imidazole is capable of as-
sembling through acid–base chemistry with a large number
of molecules possessing acidic sites, especially carboxylic
acids, and form numerous coordination complexes with
[
a] K. Bouchmella, Prof. Dr. B. Boury, Dr. S. G. Dutremez
Laboratoire “Chimie MolØculaire et Organisation du Solide”
UMR 5637
UniversitØ Montpellier II, Case Courrier 007
Place E. Bataillon, 34095 Montpellier Cedex 5 (France)
Fax: (+33)467-143-852
E-mail: dutremez@univ-montp2.fr
[
b] Dr. A. van der Lee
Institut EuropØen des Membranes, CNRS–UMR 5635
UniversitØ de Montpellier II, Case Courrier 047
Place E. Bataillon, 34095 Montpellier Cedex 5 (France)
[4,5]
many metals.
Alkylation of imidazoles gives imidazolium
6130
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 6130 – 6138

FULL PAPER
[
34–36]
salts that show many similarities with pyridinium salts, and
these salts have proven interesting for a number of reasons:
some of them are liquid at, or just above, room temperature
the halide ion and type of organic cation.
Polymers with
1:1 stoichiometries result from the interaction of diiodoace-
and a polymeric network is also
obtained by cocrystallization of diiodohexatriyne with tri-
[36–38]
tylene with halide ions,
[6,7]
or exhibit liquid crystallinity.
Imidazolium-based ionic liq-
[39]
uids are used as media in organic reactions because they are
environmentally benign and, in some cases, they perform
phenylphosphine oxide.
In that connection, Goroff and
co-workers recently reported some spectacular results: the
polymerization of diiododiacetylene was achieved in the
solid state despite the explosiveness of this molecule. This
“tour de force” was accomplished by forming halogen-
bonded complexes between diiododiacetylene and oxal-
[8]
better than the usually used organic solvents. As a result
[9]
of their high ionic conductivities, they have considerable
potential as electrolytes for batteries and capacitors. Finally,
imidazolium salts are useful starting materials for the prepa-
ration of metal complexes bearing N-heterocyclic carbene li-
amide-containing hosts terminated with nitrile groups at both
[10]
[40]
gands.
ends.
In these host–guest complexes, the diacetylenic
In recent years, halogen bonding has become an increas-
ingly important interaction in crystal engineering for the as-
guest is suitably oriented for topochemical polymerization.
Previous attempts to do the same using host molecules with
pyridyl groups instead of nitrile groups had been unsuccess-
ful as a result of steric problems.
In solution, the strength of the interaction of 1-iodoacety-
[11]
sembly of small organic building blocks.
It is a charge-
[41]
transfer interaction of the n!s* type between an electron-
rich atom and a halogen atom bonded to an electron-defi-
cient organic fragment or belonging to a dihalogen mole-
lenes with Lewis bases has been measured by means of vi-
[12]
[42]
cule. It is a directional interaction that shows many simi-
larities with hydrogen bonding: its strength depends not
only on the distance between the bonded atoms but, also,
on the D···X-Y angle (D=donor atom; X=halogen; Y=
carbon, halogen). Furthermore, it was suggested early on
that halogen bonding might be comparable in energy with
brational spectroscopy.
This technique has proven very
useful in the determination of the formation constants of
[43]
such acid–base complexes.
The interactions between
[D ]DMSO and diiodohexatriyne and diiodooctatetrayne
6
1
3
have been investigated by C NMR spectroscopy. The
chemical shifts of the carbon atoms bonded to iodine moved
from about d=1 ppm in CDCl3 to approximately d=
[13]
hydrogen bonding, and recent results from computational
[14]
studies have confirmed this idea.
15 ppm in [D ]DMSO. This effect was attributed to polariza-
6
Many reports are available concerning halogen bonding
in which the donor is a nitrogen-containing group, especially
tion of the iodoalkyne triple bond in a Lewis acid–base com-
[39]
plex with the solvent. These results were reproduced com-
[12,15–24]
[44]
pyridine and its analogues.
Surprisingly, reports are
putationally.
Additional support for this interpretation
quite scarce concerning the study of halogen-bonded sys-
tems in which imidazolyl groups take part. The diiodine ba-
sicity of imidazoles has been measured by means of the for-
mation constant of diiodine–imidazole complexes in heptane
was obtained from good correlation with various empirical
models of solvent basicity, including Gutmannꢁs donor num-
[45]
bers and Taft and Kamletꢁs b values.
Furthermore, poor
N
correlation to Reichardtꢁs E T values and Taft and Kamletꢁs
p* parameters suggests that solvent polarity does not play a
[25]
at 298 K, but the structural characterization of architec-
tures sustained by halogen bonding in which imidazolyl
groups are involved has not been reported. C-halogen···N in-
teractions have been observed by X-ray crystal studies of
[45]
2
role. Interestingly, the resonance of the I-C(sp ) moiety of
A
H
R
U
G
1
3
iodoarenes in C NMR spectroscopic analysis does not un-
dergo a downfield shift on changing from a noncoordinating
[26,27]
Schiff-base-containing triazoles and 5-bromotetrazole,
to a coordinating solvent, even though complexation
[46]
but such interactions are overpowered by hydrogen bonding
occurs. It was proposed that this phenomenon is because
the nonrelativistic complexation shifts and the change in the
spin-orbit-induced heavy-atom effect of iodine compensate
each other.
in the solid-state structures of 3-chloro-1H-1,2,4-triazole and
[28]
3-bromo-1H-1,2,4-triazole.
The electron-poor portion of the charge-transfer complex
is generally an electron-deficient organic halide, and so 1,4-
diiodotetrafluorobenzene has been used quite extensive-
We describe herein the syntheses of wholly organic archi-
tectures in which halogen-bonding interactions between imi-
dazolyl groups and haloalkene and haloalkyne moieties are
present. This structural study provides new examples of the
utilization of imidazole in the construction of self-assembled
networks and improves the current knowledge of halogen
bonding with halogenated alkenes and alkynes. The mole-
cules that were selected are 1-(3-iodopropargyl)imidazole
(2) and 1-(2,3,3-triiodoallyl)imidazole (5). Insight into the
solid-state organization of these organic modules is of para-
mount importance to the design of novel functional materi-
als with specific properties (e.g., high microporosity, nonlin-
ear optical response, and liquid crystallinity) and quite val-
uable in case solid-state reactivity is sought. Also, these
compounds are good models for future computational stud-
[
12,15,16,18,24,29,30]
ly.
Halogen bonding in which the halide is at-
tached to a double or triple bond is known, but these sys-
tems have been the subject of much fewer studies. Polymeric
chains result from the interaction between tetraiodoethylene
[16,31]
(
TIE) and diamines.
Also, this alkene has been cocrys-
tallized with various diacetylenic molecules in the hope of
obtaining host–guest complexes in which the diacetylenic
fragments are suitably oriented for topochemical polymeri-
[32,33]
zation.
Halogen bonding involving haloalkynes has been
studied in both the solid state and solution. Various com-
plexes between 1-halo-2-phenylacetylenes and halide ions
have been prepared, and the structures and stoichiometries
of these complexes were found to depend on the nature of
Chem. Eur. J. 2007, 13, 6130 – 6138
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
6131

S. G. Dutremez et al.
ies. The approach followed herein is similar to that chosen
measurements showed that large amounts of silver were
present in the solid, presumably coordinated to the imida-
zole ring of 2. Several attempts were made to remove the
silver by decomplexation with dithizone, KCN, and 1,4,8,11-
tetraazacyclotetradecane, but these attempts led to decom-
position of the product or met with only limited success.
The best method to purify the material consisted of washing
the crude solid on a glass frit with hot acetonitrile, decreas-
ing the volume of the filtrate on a rotary evaporator, and al-
lowing the material to crystallize in a freezer.
[17]
[23]
[26]
[47]
by Czugler,
van der Boom,
Drabent,
and others,
namely, the acceptor and donor sites are present in the same
molecule. By employing this approach, the chances for dis-
turbance by competing interactions are at a minimum. We
also report that these 1D heteroditopic tectons are capable
of forming cocrystals with other organic modules with hy-
drogen-bonding capabilities and that, in this case, halogen
bonding is no longer the structure-directing interaction in
the solid.
Iodination of 1 with three equivalents of the iodine–mor-
pholine complex does not lead to 2, but solid 3 is obtained
1
Results and Discussion
instead. H NMR spectroscopic analysis showed that 3 is a
mixture of 5 and morpholinium iodide in a 1:3 ratio
(Scheme 1). It is noteworthy that 3 was obtained even when
an excess of 1 was used. Clearly, under these conditions, ad-
dition of iodine across the triple bond of 2 is more facile
than iodination of 1. Washing 3 with acetonitrile yields an-
other solid 4, whose composition is 5·1morpholinium iodide.
As will be seen later, the fraction of morpholinium iodide
that is not washed away is part of a cocrystal with 5. Com-
pound 5 is obtained by suspending 4 in a saturated aqueous
solution of NaHCO3.
Syntheses: 1-Propargylimidazole (1) is a known compound
that has been prepared by N-propargylation of imidazole
[48]
using different methods.
Alternative procedures utilized
microwave irradiation in the presence of various types of
magnesium oxide catalysts or made use of solid–liquid
[49,50]
phase-transfer catalysis.
In some cases, the reaction is
complicated by the formation of substantial amounts of 1-
[50a]
propadienyl-1H-imidazole.
We prepared 1 by the reac-
tion between lithiated imidazole and propargyl bromide in
anhydrous THF, at À788C, in 82% yield after purification
by distillation under reduced pressure.
Structure of 2: X-ray quality crystals of 2 were obtained by
dissolving a small amount of powder in acetonitrile and al-
lowing the solution to come slowly to dryness. In the solid
(Table 1), molecules of 2 form layers that pile up along the
a axis (Figure 1). Looking at one layer from the top, one can
see polymeric chains that run along the c axis. These chains
resemble undulating wires and are the result of C(sp)-I···N
interactions between molecules. These findings explain why
2 is only soluble in coordinating solvents such as dimethyl
sulfoxide (DMSO) and acetonitrile: the C(sp)-I···N interac-
tions must be broken for the solid to dissolve. The N···I dis-
tance is 2.717 Š and the C(sp)-I···N angle is 175.88. These
values are indicative of strong halogen-bonding interac-
Compounds 2 and 5 have been synthesized before and
[51]
tested for antibacterial and antifungal activities.
Com-
pound 2 was obtained by allowing imidazole to react with 3-
iodopropargyl 4-methylbenzenesulfonate in DMFat room
temperature. Compound 5 was prepared similarly by using
2,3,3-triiodoallyl 4-methylbenzenesulfonate instead of 3-io-
dopropargyl 4-methylbenzenesulfonate. Our synthetic ap-
proach was different (Scheme 1): iodoalkyne 2 was synthe-
[11]
tions. The I···N distance is longer than that found in the
[
53]
PhCꢀCI·morpholine complex (2.51 Š)
and shorter than
[54]
the I···N distance in solid ICꢀCCN (2.93 Š). These results
are consistent with the fact that morpholine is a stronger
base
than
imidazole
(pK (morpholine)=5.5;
b
pK (imidazole)=7.01) and the fact that nitrile groups are
b
only weakly basic moieties. There are no I···p interactions
such as those observed in the platinum–alkynyl compounds
[55]
prepared by Adams and Bowen.
This difference is be-
cause the nitrogen atom at the 3-position of the imidazole
ring is more basic than the p cloud of the triple bond. It is
also noteworthy that acetonitrile molecules are not present
in the structure; there again, these findings agree with the
fact that imidazolyl groups are stronger bases than nitrile
moieties. Neighbouring imidazole groups in each layer are
parallel. The centroid···centroid distance between adjacent
rings is 4.377 Š, and the angle between the centroid···cent-
roid vector and the ring normal is 40.98. These parameters
Scheme 1. Syntheses of compounds 2–6.
sized by allowing alkyne 1 to react with N-iodosuccinimide
[52]
(
NIS) in the presence of 10 mol% AgNO3.
Elemental
[56–58]
analysis of the resulting pale-yellow solid gave unsatisfactory
results. Furthermore, energy-dispersive spectroscopy (EDS)
are indicative of weak p···p interactions.
Yet, given the
large number of such interactions in 2, it is likely that their
6132
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ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 6130 – 6138

Interactions in Organic Architectures
FULL PAPER
Table 1. Crystal data and experimental details of data collection and refinement of 2, 4, 5 and 6.
ring). This weak interaction is
of type III according to the
classification developed by
Compound
2
4
5
6
empirical formula
formula weight
crystal colour
crystal size [mm]
crystal system
space group
a [Š]
b [Š]
c [Š]
a [8]
C
232.02
colourless
0.15”0.20”0.30
monoclinic
6
H
5
I
1
N
2
C
10
H
15
I
4
N
3
O
1
C
6
H
5
I
3
N
2
4 10 1 1 1
C H I N O
215.035
pale yellow
[59]
700.87
pale yellow
0.05”0.05”0.16
monoclinic
485.83
light brown
0.28”0.30”0.35 0.06”0.10”0.27
monoclinic monoclinic
P2 /n (no. 14) P2 /c (no. 14)
4.79500(10)
16.5970(3)
13.3515(3)
90
Malone et al., and the H···Cg
distance is the same as that typ-
ically found in complexes be-
tween alkanes and aromatic
P2
1
/c (no. 14)
P2
1
/c (no. 14)
1
1
[60]
8.863(4)
4.377(2)
18.677(1)
90
12.4431(6)
14.9315(6)
9.6060(4)
90
6.6135(5)
10.4064(8)
10.1808(8)
90
species.
Structure of 5: X-ray-quality
crystals of 5 were grown from
acetonitrile. In the solid state
(Table 1), molecules of 5 pile
up in stacks along the a axis
b [8]
g [8]
V [Š ]
Z
95.507(4)
90
721.2(5)
4
97.002(4)
90
1771.43(13)
4
95.008(4)
90
1058.49(4)
4
98.893(7)
90
692.25(9)
4
3
T [K]
173
2.137
173
2.628
173
3.026
173
2.063
(
Figure 2). The stacks are not
isolated but interact with one
another: cut through the
stacks along the bc plane shows
that alkene self-assembles
À3
1
calcd [gcm
]
F
A
C
H
T
R
E
U
N
G
(000)
432
4.349
1264
7.031
856
8.741
408
4.527
À1
m [mm
]
a
T
min, Tmax
0.49, 0.52
0.71073
0.70, 0.73
0.71073
0.07, 0.09
0.71073
0.37, 0.76
0.71073
graphite-monochromated
MoKa radiation [Š]
q range [8]
5
into polymeric chains that run
parallel to the b axis. The mole-
3.027–32.295
À12ꢁhꢁ12
À6ꢁkꢁ6
À27ꢁlꢁ27
12416
3.163–32.304
À18ꢁhꢁ17
À21ꢁkꢁ22
À14ꢁlꢁ14
27703
2.885–32.312
À7ꢁhꢁ6
À24ꢁkꢁ24
À19ꢁlꢁ19
20287
3.118–32.258
À9ꢁhꢁ9
À14ꢁkꢁ15
À15ꢁlꢁ14
12928
index ranges
cules
are
interconnected
through halogen bonds, with
each halogen bond involving
the imidazolyl group of one
molecule and the =CI2 frag-
ment of the next molecule. The
chains are zigzag-shaped as a
result of the crooked form of
the organic module. In each
molecule, the imidazolyl group
and the CI=CI2 fragment lie
data collected
unique data, Rint
observed data (I >2s(I ))
o o
2371, 0.049
1518
5804, 0.067
2238
3493, 0.029
2710
4381, 0.105
1518
L.S. parameters, restraints
82, 0
0.0501, 0.0355
0.0804, 0.0361
163, 0
0.0437, 0.0404
0.1354, 0.0482
100, 0
65, 0
[
a]
[b]
R,
R,
R
R
w
(obsd reflns)
(all reflns)
0.0208, 0.0255
0.0310, 0.0257
12.7, À6.97,
10.7
0.001986
0.9781
0.0344, 0.0201
0.0603, 0.0219
À34.0, 23.9, À69.7,
22.6, À29.9
0.000920
1.0155
À1.20, 0.83
[
a]
[b]
w
[
c]
weighting scheme,
A
i
13.7, 0.705, 9.65, 8.30, À7.54, 3.87,
6.66, 1.05
1.79, À1.38
0.001276
1.1424
max shift/esd
0.000185
1.1126
À1.38, 1.44
goodness-of-fit
D1min, D1max [e Š
À3
]
À1.25, 1.59
À1.18, 0.99
2
o
2
2
2
o
2
1/2
2 2
[
[
a] R=ꢀjjF
o
jÀjF
c
jj/ꢀjF
o
j.
[b] R
w
=[ꢀ(w(F ÀF ) )/ꢀ(w(F ) )]
.
[c] w=[weight]”[1À(DF/6s(F)) ] ; almost perpendicular to each
c
weight]=1.0/[A
0
T
0
(x) + A
1
T
1
(x) + … + AnÀ1TnÀ1(x)] where A are the Chebychev coefficients listed in the
i
other. Intermolecular I···N dis-
Table and x=Fcalcd/Fmax
.
tances are 2.901 Š and the C-
2
A
H
R
U
G
thus indicating that this interac-
tion is reasonably strong; how-
ever, it is weaker than that ob-
served in alkyne 2, in accord-
ance with the order C(sp)-
!
2
!
X
base>C
A
H
R
U
G
3
!
[11]
A
H
R
U
G
The I···N dis-
tance reported herein is slightly
shorter than those observed
previously in complexes of TIE
[16,32,33]
with nitrogen bases.
The
Figure 1. View along the b axis showing the layered structure of 2 and the N···I interactions between molecules
in each layer.
only exceptions are 1,2-bis(4-
pyridyl)ethylene·TIE
[16]
(
2.840 Š)
and 1,4-bis(3-qui-
The centroid···cent-
[33]
contribution to the stabilization of the structure is not zero.
There is also a C-H···p contact between the methylene
group of one molecule and the imidazole ring of an adjacent
molecule in the same layer. The H···Cg distance is 2.70 Š,
the C-H···Cg angle is 132.08, and the angle between the H–
Cg axis and H–Hperp vector is 6.68 (Cg: centroid position;
Hperp: orthogonal projection of the H position onto the
nolyl)-1,3-butadiyne·TIE (2.884 Š).
roid distance between two adjacent imidazole rings in one
stack is 4.795 Š, and the angle between the centroid···cent-
roid vector and the ring normal is 50.18. These parameters
[56–58]
are indicative of negligible p···p interactions.
In addi-
tion, CH ···imidazole contacts similar to those observed in
2
solid 2 are not present.
Chem. Eur. J. 2007, 13, 6130 – 6138
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
6133

S. G. Dutremez et al.
with the fact that morpholine is
a stronger base than imidazole
(
see
the
aforementioned
pK values). However, there
b
exist examples in the literature
in which the protonation
scheme disagrees with the acidi-
ty constants derived from solu-
tion. This phenomenon was ob-
served in the X-ray crystal
structure of [NH (CH ) ] -
A
T
E
N
2 3 2 12
A
H
R
U
G
A
H
R
N
A
H
R
U
G
3
2
A
H
R
U
G
(H TMA=trimesic
3
[65]
acid). We have obtained con-
firmation that our assignment is
correct by comparing the CÀN
Figure 2. View along the a axis showing one layer of 5 and the N···I interactions between molecules in that
layer.
Structure of 4: Single crystals of 4 were grown from acetoni-
trile. A view of the packing is shown in Figure 3 and the cor-
responding crystallographic data are listed in Table 1. Close
inspection of the structure shows that there is no stacking of
the molecules as seen in crystalline 2 and 5. Furthermore,
the I···N halogen-bonding interactions observed in 5 are no
longer present. There is, however, one halogen bond be-
tween the iodide anion and one iodine atom from the =CI
2
2
fragment. The I···I distance is 3.470 Š and the I···I-C
A
H
R
U
G
angle is 170.78. This interaction is appreciably stronger than
that found in the [2,2’-bpy(H)]I ·TIE (bpy=bipyridine)
3
complex, for which I···I interactions between the TIE mole-
cules and the triiodide anions amount to 3.643 and
[61]
3
.672 Š. The organization of 4 is governed by two hydro-
gen-bonding networks that are interwoven: the first network
involves N-H···O interactions between nearby morpholinium
cations, and the second network is based on N-H···N hydro-
gen bonding between morpholinium cations and imidazolyl
groups. Both hydrogen-bonding schemes are charge-assisted.
Interactions between the morpholinium cations generate
Figure 3. View showing the organization of 4 in the crystalline state.
+
polymeric chains. The N H···O distance is 1.983 Š, the
+
N···O distance is 2.843 Š, and the N H···O angle is 180.08.
bond lengths of the imidazole ring and the CÀN bond
+
The N H···O and N···O distances are comparable to those
lengths of the morpholinium cation with known data. For
the imidazole ring, the C(12)ÀN(8) bond length is 1.369 Š
and C(12)ÀN(11) is 1.301 Š (Figure 4). These values lie in
found in the X-ray crystal structures of morpholinium pen-
+
[62]
taiodide (N H···O=2.102 Š, N···O=2.863 Š)
and mor-
+
pholinium triiodide (N H···O=2.13 and 2.18 Š, N···O=
.849 and 2.838 Š).
the same range as those found in 5 (i.e., d
A
T
E
N
(CÀN)=1.344 Š,
[63]
+
2
However, the N H···O angle ob-
d(C=N)=1.318 Š). A search through the Cambridge Struc-
A
H
R
U
G
served in crystalline 4 is flat, which suggests that the hydro-
gen-bonding interaction is stronger (aN H···O=125.18 in
tural Database (CSD) indicates that for neutral imidazole
moieties the mean CÀN bond length is 1.356 Š and the
+
morpholinium pentaiodide and 157 and 1488 in morpholini-
+
um triiodide). The N H···N distance is 1.790 Š, the N···N
+
distance is 2.797 Š, and the N H···N angle is 179.88. The
only reported structure in which an imidazolyl nitrogen
+
atom interacts with a NH2 fragment is that of 1-hydroxy-
methyl-4,5,6,7-tetrahydro-1H-imidazo(4,5-c)pyridine-6-car-
A
H
R
N
[
64]
+
boxylic acid monohydrate. In this case, the N H···N dis-
+
tance is 1.956 Š, the N···N distance is 2.824 Š, and the N
H···N angle is 171.58.
The binding of an H species to the morpholine nitrogen
+
Figure 4. ORTEP diagram of 4 showing ellipsoids at the 50% probability
atom rather than to the imidazolyl nitrogen atom agrees
level and the atom numbering scheme.
6134
www.chemeurj.org
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 6130 – 6138

Interactions in Organic Architectures
FULL PAPER
[
66]
mean C=N bond length is 1.313 Š.
These bond lengths
the current knowledge of halogen bonding with halogenated
alkenes and alkynes. 1-(3-Iodopropargyl)imidazole (2) and
1-(2,3,3-triiodoallyl)imidazole (5) were synthesized and their
solid-state organization studied. As anticipated, these wholly
organic modules self-assemble through N···I halogen-bond-
ing interactions. The N···I interaction observed in 2 is quite
tend to become almost equal when the imidazole nitrogen
atom is protonated or alkylated (mean d
(CÀN)=1.326 Š
(C=N)=1.323 Š). Concerning the morpholini-
um cation, the C(15)ÀN(16) bond length is 1.478 Š and
C(17)ÀN(16) is 1.490 Š (Figure 4). These values are similar
to those observed in the X-ray crystal structure of morpholi-
AHCTREUNG
[66]
and mean d
ACHTREUNG
[11]
strong relative to data surveyed by Metrangolo et al. The
nium iodide 6 (discussed below; i.e., d
.488 Š). In addition, they are much longer than the CÀN
bond lengths found in the structure of morpholine at 150 K
A
H
R
U
G
N···I interaction found in 5 is weaker, in accordance with
!
2
!
[11]
1
the order C(sp)-X base>C
A
H
R
U
G
The use of
linear modules has made possible the preparation of poly-
meric chains that run throughout the solid, and the use of
organic modules with shapes other than linear should make
possible the preparation of 3D networks with open cavities.
In addition, this study provides valuable information that
can be used to organize suitably diacetylenic molecules for
solid-state polymerization, as demonstrated recently by
[67]
(
i.e., 1.466 and 1.469 Š).
[40]
Goroff and co-workers.
We also report that these molecules are capable of form-
ing cocrystals with other organic modules that possess hy-
drogen-bonding capabilities, as testified by the X-ray crystal
structure of 4. In this case, the N···I halogen-bonding
scheme observed in 5 is disrupted because the imidazolyl
group, the most basic moiety in the molecule, is part of the
hydrogen-bonding network. Nonetheless, halogen bonding is
quite persistent as the triiodoalkene fragment is found to
participate in a halogen bond with a surrounding anion.
Attempts are currently being made by us to modify the
solid-state organization of 2 and 5 to prepare novel func-
tional materials. In particular, complexation of the imi-
dazole nitrogen atom with a metal is being studied. Other
types of halogen-bonding schemes are also being inves-
tigated, especially through alkylation of the imidazole nitro-
[69]
gen atom with an alkyl halide or using pyridinium perha-
lometallate salts similar to those utilized by Brammer
et al.
Figure 5. View showing the organization of 6 in the crystalline state.
[70]
lographic data are listed in Table 1. The structure of 6 differs
significantly from that of 4 as it is not sustained by N-H···O
interactions. In crystalline 6, morpholinium cations are inter-
Experimental Section
connected through C-H···O bridges (d
ACHTREUNG
+
2
General considerations: The synthesis of 1 was carried out in an inert at-
mosphere of argon using standard Schlenk-line techniques. THFwas dis-
tilled over sodium/benzophenone prior to use.
ACHTREUNG
observed herein are close to the mean H···O distance found
for complexes in which a CH Cl molecule interacts with a
1
13
Solution H and C NMR spectra were obtained on a Bruker Avance
2
2
1
[68]
DPX 200 instrument. H NMR chemical shifts were referenced to the
C-O-C acceptor (2.50 Š).
Furthermore, similar C-H···O
1
3
protio impurity of the NMR solvent and C NMR chemical shifts to the
NMR solvent. Infrared spectra were recorded on a Thermo Nicolet
bridges were found to govern the organization of morpho-
[67]
line in the solid state (H···O=2.63 Š). Concerning N-H···I
distances, those observed in 6 are much shorter than that
found in the X-ray crystal structure of morpholinium pen-
À1
Avatar 320 FT-IR spectrometer with a resolution of 4 cm . Fast-atom
bombardment (FAB) mass spectra were obtained on
a Jeol JMS-
SX102 A instrument and electrospray ionization (ESI) mass spectra on a
Micromass QTOFspectrometer. Melting points were measured on a
Büchi B-540 melting point apparatus and are uncorrected. Energy-disper-
sive spectroscopic (EDS) measurements were carried out using an
Oxford X-ray detector mounted on a Cambridge S360 scanning electron
microscope. Prior to EDS analysis, the sample was coated with thermally
evaporated carbon. Elemental analysis was performed in-house using a
Thermo Finnigan FLASH EA 1112 Series analyzer. Determination of
the iodine content was carried out at the Service Central de Microanalyse
of the Centre National de la Recherche Scientifique (CNRS; Vernaison,
France).
[62]
taiodide (2.788 Š). Also, N-H···I angles are wider (161.6
and 152.68 in 6 versus 148.88 in morpholinium pentaiodide).
Conclusion
The study described herein provides new examples of the
utilization of imidazole in crystal engineering and improves
Chem. Eur. J. 2007, 13, 6130 – 6138
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
6135

S. G. Dutremez et al.
Materials: The following chemicals were obtained from commercial sour-
ces and used as supplied: imidazole (Aldrich), 2.5m solution of n-butyl-
lithium in hexanes (Aldrich), 80 weight% solution of propargyl bromide
in toluene (Aldrich), N-iodosuccinimide (Acrôs Organics), silver nitrate
47.8 mmol) was added, and the reaction mixture was stirred at room tem-
perature overnight. Removal of the toluene in vacuo furnished a brown
solid identified as 1-(2,3,3-triiodoallyl)imidazole·3morpholinium iodide
1
(3) by H NMR spectroscopic analysis (52.24 g, 96%).
(
Fluka), morpholine (Lancaster), and sodium hydrogencarbonate (Pro-
Solid 3 was placed on a glass frit, washed with acetonitrile, and the result-
labo).
ing yellow powder was dried in vacuo. The washed solid was identified as
1
1
-Propargylimidazole (1): Imidazole
8.51 g, 0.125 mol) was introduced in a
50-mL two-necked flask containing a
magnetic stirring bar and equipped
with pressure-equalizer dropping
funnel. The solid was dissolved in an-
1-(2,3,3-triiodoallyl)imidazole·1morpholinium iodide (4) by H NMR
(
2
spectroscopic and elemental analyses and by a single-crystal X-ray dif-
1
fraction study (26.81 g, 80%). M.p. 132.7–133.98C; H NMR (200.1 MHz,
[D ]DMSO): d=3.11 (t, J=4.80 Hz, 4H; H8), 3.76 (t, J=4.80 Hz, 4H;
6
a
H7), 4.96 (s, 2H; H4), 7.04 (s, 1H; H1), 7.16 (s, 1H; H2), 7.84 (s, 1H;
1
3
H3), 8.69 ppm (broad, 2H; H9); C NMR (50.3 MHz, [D ]DMSO): d=
6
hydrous THF(100 mL) and the solution cooled to À788C. nBuLi solu-
tion (50 mL, 0.125 mol) was added dropwise. The reaction mixture was
kept at À788C for 2 h, during which time a white precipitate formed. The
suspension was transferred with a cannula into a second flask containing
a cold (À788C) solution of propargyl bromide (18.58 g, 0.125 mol) in
THF(50 mL). The reaction mixture was stirred at À788C for 3 h, then at
room temperature overnight. A brown solution was obtained. The sol-
vents were removed in vacuo, and the resulting viscous oil was hydro-
lyzed with deionized water (50 mL). The aqueous solution was washed
with dichloromethane (3”150 mL), these organic fractions were com-
38.1 (C6), 43.8 (C8), 62.0 (C4), 64.2 (C7), 114.8 (C5), 119.9 (C2), 129.6
(C1), 138.4 ppm (C3); MS (ESI) (CH CN): m/z (%): 972.54 (58)
3
+
+
[2C H N CH CI=CI +H] , 701.77 (31) [M+H] , 486.74 (100)
3
3
2
2
2
+
+
[C H N CH CI=CI +H] , 232.97 (55) [C H N CH CꢀCI+H] , 88.07
3
3
2
2
2
3
3
2
2
+
(18) [morpholine+H] ; elemental analysis calcd (%) for C H I N O
1
1
0
15
4
3
(700.87): C 17.14, H 2.16, O 2.28, N 6.00, I 72.43; found: C 17.74, H 2.15,
O 3.36, N 6.57, I 71.88.
1
-(2,3,3-Triiodoallyl)imidazole
(5):
Compound 4 (5.99 g, 12.3 mmol) was
suspended in a saturated aqueous solu-
tion of NaHCO (100 mL; pH 8) and
3
stirred for 3 h. A yellow solid was ob-
bined, and the organic layer was dried over MgSO
4
. The volatiles were
removed and the crude product was purified by vacuum distillation
1
(
708C, 5 mbar). A yellow oil was obtained (11.13 g, 82%). The H NMR
tained after suction filtration (2.54 g,
1
3
spectroscopic data were the same as those given in ref. [48d]; C NMR
1
8
9%). M.p. 123.6–127.68C; H NMR (200.1 MHz, [D
6
]DMSO): d=4.95
(
50.3 MHz, CDCl
3
): d=36.3 (C4), 75.1 (C6), 77.1 (C5), 119.1 (C2), 129.6
(
s, 2H; H4), 6.98 (s, 1H; H1), 7.12 (s, 1H; H2), 7.73 ppm (s, 1H; H3);
2
(
C1), 136.9 ppm (C3); IR (CCl
4
): n˜ =3311 (vs; C(sp)-H), 3117 (w; C
A
H
R
U
G
13
C NMR (50.3 MHz, [D
6
]DMSO): d=36.6 (C6), 62.0 (C4), 115.1 (C5),
CN): m/z (%):
72.50 (44) [2M+H] , 486.75 (100) [M+H] ; elemental analysis calcd
(485.83): C 14.83, H 1.04, N 5.77; found: C 14.90, H
3
À1
H), 2923 (w; C
ACHTREUNG
1
9
19.8 (C2), 129.9 (C1), 138.5 ppm (C3); MS (ESI) (CH
3
+
+
(
NOBA): m/z (%): 213 (14) [2M+H] , 107 (100) [M+H] , 39 (24)
+
+
+
[
CH
2
CꢀCH] .
(
%) for C
6 5 3 2
H I N
1-(3-Iodopropargyl)imidazole (2): N-
0.98, N 5.42.
Iodosuccinimide (4.07 g, 18.1 mmol)
and silver nitrate (0.31 g, 1.81 mmol)
were added successively to a solution
Morpholinium iodide (6): Solid 3 was
washed with acetonitrile and the re-
sulting filtrate was concentrated to
dryness to yield a brown solid. Recrys-
tallization of the solid from acetoni-
of
100 mL). The reaction mixture was
stirred at room temperature for 3 h
1 (1.92 g, 18.1 mmol) in acetone
(
trile gave
M.p. 195.2–203.08C; H NMR (200.1 MHz, [D
H2), 3.76 (m, 4H; H1), 8.69 ppm (broad, 2H; H3); C NMR (50.3 MHz,
]DMSO): d=43.8 (C2), 64.1 ppm (C1); MS (ESI) (CH CN): m/z (%):
a
crystalline powder identified as
6
(15.2 g, 70.7 mmol).
and then filtered. The solvent was removed on a rotary evaporator. The
residue was washed with water (50 mL) and diethyl ether (50 mL). A
beige solid was recovered (2.61 g, 62%). Elemental analysis of the solid
showed large discrepancies between the experimental and the calculated
values because of the presence of silver in the sample: elemental analysis
1
6
]DMSO): d=3.12 (m, 4H;
13
[
5
8
D
6
3
+
+
18.05 (6) [2M+morpholine+H] , 303.05 (53) [M+morpholine+H] ,
+
8.06 (100) [morpholine+H] ; elemental analysis calcd (%) for
(215.03): C 22.34, H 4.69, O 7.44, N 6.51; found: C 21.98, H
.29, O 7.83, N 6.67.
calcd (%) for C
6 5 1 2
H I N (232.02): C 31.06, H 2.17, N 12.07; found: C
4 10 1 1 1
C H I N O
4
2
6.56, H 1.86, N 10.08.
The solid was purified as follows: Crude 2 (0.17 g) was placed on a glass
frit, and the solid was washed with hot acetonitrile (25 mL). The volume
of the yellow filtrate was reduced on a rotary evaporator, and the con-
centrated solution was placed in a freezer overnight. A crystalline
X-ray diffraction: Intensity measurements were carried out at the joint
X-ray diffraction facility of the Institut Charles Gerhardt and the Institut
EuropØen des Membranes (UniversitØ Montpellier II, France) at 173 K
using an Oxford Diffraction Xcalibur-1 CCD diffractometer. The crystal-
to-detector distance was 50 mm; other data collection parameters were
nearly identical in all four experiments. A total of 678 exposures were
taken using w scans with oscillations of 18. The counting time per frame
varied between 30 and 40 s. The data were corrected for possible intensi-
powder precipitated out which was collected by suction filtration
1
(
0.068 g, 40%). M.p. 227.7–232.48C; H NMR (200.1 MHz, [D
6
]DMSO):
d=5.05 (s, 2H; H4), 6.92 (s, 1H; H1), 7.21 (s, 1H; H2), 7.67 ppm (s, 1H;
1
3
H3); C NMR (50.3 MHz, [D
6
]DMSO): d=13.1 (C6), 38.1 (C4), 88.5
(
C5), 120.3 (C2), 129.6 (C1), 138.0 ppm (C3); IR (KBr): n˜ =3110 (s; C-
[71]
ty decay and absorption using the empirical AbsPack procedure. All
2
3
À1
A
C
H
T
R
E
U
N
G
(sp )-H), 2921 (w; C
A
C
H
T
R
E
U
N
G
(sp )-H), 2174 (m; CꢀC), 1503 cm (vs; ring); MS
[72]
four structures were solved by direct methods using SIR2002 and re-
+
(
(
2
ESI) (CH
%) for C
.44, N 14.06.
3
CN): m/z (%): 232.95 (100) [M+H] ; elemental analysis calcd
[73]
fined by least-squares methods on F using CRYSTALS. The structure
6
H
5
I
1
N
2
(232.02): C 31.06, H 2.17, N 12.07; found: C 32.69, H
of 6 was initially solved in the noncentrosymmetric space group P2
direct methods gave no solution in the centrosymmetric space group P2
c. Upon close inspection of the solution, an inversion center was added
as
1
1
/
Cocrystal 1-(2,3,3-triiodoallyl)imidazole·1morpholinium iodide (4): In an
inert atmosphere, morpholine (25 g, 0.287 mol) was added dropwise to a
cold (08C) solution of iodine (36.47 g, 0.143 mol) in toluene (200 mL).
The solution was stirred at room temperature for 2 h. Alkyne 1 (5.08 g,
[74]
by the Addsym option of the PLATON program. For 2, 5, and 6, the
hydrogen atoms were positioned from difference Fourier maps. In the
case of 4, the hydrogen atoms were positioned by taking into account a
possible hydrogen-bonding interaction between the morpholine molecule
and the imidazole moiety. The nitrogen and oxygen atoms of morpholine
were assigned on the basis of observed bond distances (d
and d
(CÀN)=1.48 Š). As a consequence of correctly assigning these
atoms, temperature factors became “normal”. The nitrogen atom at the
-position of the imidazole ring was assigned by postulating a hydrogen
A
H
R
U
G
AHCTREUNG
3
6136
www.chemeurj.org
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 6130 – 6138

Interactions in Organic Architectures
FULL PAPER
bond with morpholine. There is no interaction between the hydrogen at
the 2-position of the imidazole ring and morpholine. Also, there is no in-
teraction between this hydrogen atom and the iodide anion present in
the lattice. Final R values and the relevant crystallographic data are given
in Table 1. CCDC-623085 (2), -623086 (4), -623088 (5), and -623087 (6)
contain the supplementary crystallographic data for this paper. These
data can be obtained free of charge from The Cambridge Crystallograph-
ic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
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