Solid state synthesis under supramolecular control of a 2D heterotetratopic self-complementary tecton tailored to halogen bonding

Article abstract of DOI:10.1039/b605958a

We describe the synthesis and characterization, by single crystal X-ray analysis, of a 1D heteroditopic self-complementary tecton for halogen bonding. It was designed to also incorporate double bonds and to possess heteropolar π-π stacking groups in order to carefully control its supramolecular organization in the solid state. As a result of this supramolecular control, by UV irradiation in the solid state the compound dimerizes forming a 2D heterotetratopic self-complementary tecton tailored to halogen bonding based self-assembly. This 2D tecton crystallizes clathrating chloroform molecules. the Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2006.

Full text of DOI:10.1039/b605958a

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PAPER
www.rsc.org/njc | New Journal of Chemistry
Solid state synthesis under supramolecular control of a 2D
heterotetratopic self-complementary tecton tailored to halogen bondingwz
Giovanni Marras,a Pierangelo Metrangolo,*a Franck Meyer,a Tullio Pilati,b
Giuseppe Resnati*a and Ashwani Vijc
Received (in Montpellier, France) 26th April 2006, Accepted 21st June 2006
First published as an Advance Article on the web 31st July 2006
DOI: 10.1039/b605958a
We describe the synthesis and characterization, by single crystal X-ray analysis, of a 1D
heteroditopic self-complementary tecton for halogen bonding. It was designed to also incorporate
double bonds and to possess heteropolar p–p stacking groups in order to carefully control its
supramolecular organization in the solid state. As a result of this supramolecular control, by UV
irradiation in the solid state the compound dimerizes forming a 2D heterotetratopic self-
complementary tecton tailored to halogen bonding based self-assembly. This 2D tecton
crystallizes clathrating chloroform molecules.
olefins for photoreaction in the solid state and in solution.4
Introduction
Among these interactions, p–p donor–acceptor interactions
Solid state synthesis is one of the most fascinating and rapidly
have been used extensively as a steering device for potentially
emerging fields of Chemistry.1 The interest in this innovative
photoreactive structures5 as these interactions present the
solventless approach lies in the high yields, the reduced for-
advantage that p–p stacked aromatic rings lie at a distance
mation of undesired side-products, and sustainability thanks
that roughly corresponds to that needed for the photocycliza-
to the particularly low waste produced by these kinds of
tion of double bonds in the solid state (typical cut-off distance
of p–p stacking 3.9 A).6
On the other hand, the use of non-covalent interactions to
reactions. Moreover, the highly organized environment of
the solid state is an attractive medium for conducting stereo-
selective reactions. In particular, the topochemical control of
dictate the self-assembly of unsaturated molecules around
UV-promoted [2 + 2] cycloaddition reactions in the solid state
templates provides a very reliable and efficient tool to force
represents a promising way to form covalent bonds in a regio-
unsaturated modules to meet Schmidt’s requirements. The
and stereoselective manner. The seminal work of Schmidt2
regiocontrol in covalent bond formation has been recently
clearly established the requirements two double bonds should
achieved through the organization of olefinic modules by
hydrogen bonding-based templates.7 Following an analogous
meet for undergoing [2 + 2] photoaddition in the solid state.
strategy, we have used an Nꢀ ꢀ ꢀI halogen bonding (XB)8-based
The olefins have to be oriented in a parallel manner and the
distance between their centres has to be lower than 4.2 A. This
template to direct the topochemical alignment of double bonds
can be realized by achieving control over the pattern of
in the solid state. Our template operated at two levels:
organization of the unsaturated modules in their crystal
intramolecular p–p interactions pre-organize the template
arms, and the alignment of template arms is translated into
packing.
However, the careful engineering of the supramolecular
the alignment of olefins at the distance needed for photoreac-
arrangement of the modules in the crystal packing is quite
tion, thanks to the highly directional Nꢀ ꢀ ꢀI XB. The [2 + 2]
hard, owing to the sensitivity of crystal structure to molecular
photocyclization of trans-1,2-bis(4-pyridyl)ethylene has given
the corresponding cycloadduct stereospecifically.9
structure. It has been demonstrated that steering groups such
as chloro, bromo, fluoro, trifluoro, and methoxy and acetoxy
The formation of halogen-bonded supramolecular architec-
groups3 can force molecules to pack in the desired crystalline
tures has been extensively studied in our group.10 In most
order. Also, the use of directing intermolecular interactions
cases, telechelic donor (D) and acceptor (A) modules self-
has proved fruitful in dictating the topochemical alignment of
assemble by XB into infinite 1D chains in which D and A
alternate systematically. On the other hand, only a few exam-
a NFMLab - DCMIC ‘‘G. Natta’’, Via L. Mancinelli 7, 20131 Milan,
ples of heteroditopic self-complementary modules for XB
Italy Campus of Como, Politecnico di Milano, Via Castelnuovo 7,
(possessing XB-D and -A groups in the same molecular
structure) have been described in the literature.11 With this
in mind, we have synthesized the 1D heteroditopic self-com-
plementary tecton 4 tailored to XB-based self-assembly. It was
designed in order to possess terminal XB-D and -A groups,
and to incorporate electron-rich and electron-poor aromatics
connected by a double bond. It was expected that such a
molecule self-organizes into 1D infinite polar chains thanks to
self-complementary XB. Moreover, as a result of heteropolar
22100 Como, Italy. E-mail: pierangelo.metrangolo@polimi.it.
E-mail: giuseppe.resnati@polimi.it; Fax: +39 02 2399 3180; Tel:
+39 02 2399 3041 (P. M.), 3032 (G. R.); http://nfmlab.
chem.polimi.it
b CNR–ISTM, University of Milan, Via C. Golgi 19, 20133 Milan,
Italy
c AFRL/PRSP, 10 E. Saturn Blvd., Edwards AFB, CA 93524, USA
w The HTML version of this article has been enhanced with additional
colour images.
z Electronic supplementary information (ESI) available: Figures of 4
and 5 and a DSC plot. See DOI: 10.1039/b605958a
ꢁc
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p–p stacking between adjacent chains, the double bonds of the
different modules 4 should organize in order to meet Schmidt’s
requirements for regiocontrolled photocyclization in the solid
state.
Results and discussion
The synthesis of the stilbene derivative 3 was achieved by a
Wittig reaction between the phosphonium salt 1 and the para-
(dimethylamino)benzaldehyde 2 in THF, by using n-BuLi. A
96 : 4 mixture of trans : cis isomers was obtained in 84%
overall yield; stereoisomers were easily separated by chroma-
tography. Iodination of the tetrafluorobenzene group12 was
carried out with n-BuLi–I2 in THF affording 4 in 85% yield
(Scheme 1).
Fig. 1 Two ORTEPIII views of the structure of the self-complemen-
tary tecton 4 tailored to XB, with its numbering scheme. Ellipsoids at
50% probability level; H atoms not to scale. Colour code: black,
carbon and hydrogen; blue, nitrogen; green, fluorine; purple, iodine.
Orange-yellow prismatic crystals have been obtained upon
slow evaporation of the solvent at room temperature from a
chloroform solution of the heteroditopic XB tecton 4. The
single crystal X-ray analysis of those crystals gave details on
the molecular and supramolecular structure of 4, which crys-
tallizes in the monoclinic space group P21/c. The whole
molecule assumes a nearly planar conformation to maximize
the superposition of p orbitals as typical for all 4-dimethyl-
aminostilbenes and polyfluorostilbenes. The two aromatic
rings in 4 are slightly rotated relative to each other (by an
angle of only 5.341) and the N atom is characterized by a near
planarity (C–N–C angles in the range 116.53–119.391, Fig. 1).
The coplanarity of tetrafluoroaromatic ring and double bond
is strengthened by two intramolecular Hꢀ ꢀ ꢀF hydrogen bonds
(F1ꢀ ꢀ ꢀH8 is 2.35 A and F4ꢀ ꢀ ꢀH7 is 2.43 A).
types of interactions between aromatic rings: through the
1 1 1
2 2 2
centre at , , only two antiparallel iodotetrafluoro benzenes
interact, having 3.908 A between their centroids (red full
circles in Fig. 2), while through the centre at 12,0,21 two
molecules are completely superposed with two pairs of tetra-
fluorobenzene and benzene ring centroids at a distance of
3.901 A. Interestingly, the distance of the centroids of the
double bonds for this couple of molecules is only 3.758 A,
nearly a pre-reactive state of the [2 + 2] reaction. Schmidt’s
rule is thus respected and the molecule undergoes solid state
cycloaddition by UV photoirradiation.
The photoirradiation was performed by using a Rayonet
instrument at 300 nm. Finely powdered crystals of tecton 4
were placed between two glass slides and irradiated for 24 h at
room temperature to give the cycloadduct 5 in 80% yield, as a
yellow powder (Scheme 2). The 1H-NMR spectrum of the
photoirradiated product revealed unequivocally the cyclo-
butane ring formation (single peak at 4.80 ppm, Fig. 3) and
proved its complete regio- and stereospecificity.9
As concerns the supramolecular organization of 4 in the
crystal packing, the molecules are arranged in a head-to-tail
fashion into 1D infinite chains, as expected for a telechelic self-
complementary XB heteroditopic tecton. Two molecules ap-
proach each other in a perpendicular fashion (Fig. 2, the
1
2
1
2
C
Ar–Niꢀ ꢀ ꢀI angle (i = 1 + x, ꢂ y, + z) is 97.381). The
Niꢀ ꢀ ꢀI distance is 3.093 A, about 12% shorter than the sum of
van der Waals radii for N and I (3.53 A).13 The Niꢀ ꢀ ꢀI–C angle
is 169.821, in good agreement with an n - s* electron
donation from N to I atoms. The head-to-tail arrangement
of the dipolar modules 4 ensures that each 1D chain is polar.
Coupling of antiparallel 1D dipoles14 and the p–p attraction
between opposite quadrupolar moments (Fig. 2) generates a
centrosymmetric 2D structure with adjacent chains running in
opposite directions. These 2D structures are bonded together
in the third dimension by only residual forces. There are two
Fig. 2 A view down the crystallographic c axis of the crystal packing
of the XB-based self-complementary tecton 4 (capped-stick style).
Colour code: dark grey, carbon; blue, nitrogen; green, fluorine; purple,
iodine. Halogen bonds are dotted black lines. Red full circles indicate
the centroids of aromatic rings and double bonds.
Scheme 1 Synthesis of the 1D heteroditopic self-complementary
tecton 4 tailored to XB.
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Scheme 2 Solid state photoreaction of 4 to yield the 2D hetero-
tetratopic self-complementary tecton 5 tailored to XB-based self-
assembly.
As shown in Fig. 2, in the crystal packing the modules 4 are
organized in well-defined and isolated photoreactive couples.
A 100% maximum could be therefore predicted, but the
photoirradiation of 4 never leads to its total conversion into
the corresponding cyclobutane derivative 5. A detailed discus-
sion of the reasons why the optimized yield is about 80% is far
beyond the scope of this article. However, different irradiation
times and wavelengths have never resulted in quantitative
yields; moreover, an equilibrium mechanism responsible for
the 80% yield has also been excluded. Cases of anomalous
photoreactivity in the solid state have been already reported in
the literature.3f,15 Low solid state yields could mean that the
deformations in the reacting crystal prevent subsequent reac-
Fig. 4 A ORTEPIII view of structure of the XB-based self-comple-
mentary tecton 5 with its numbering scheme. Ellipsoids at 50%
probability level; H atoms not to scale. Colour code: black, carbon
and hydrogen; blue, nitrogen; green, fluorine; purple, iodine.
tivity. This can be ascribed to the high strength, directionality,
and limited flexibility of XB, which is preserved in the photo-
reacted crystal and probably induces a tremendous deforma-
tion of the crystal lattice of 4 on cyclobutane formation. In
order to verify this hypothesis, we also studied the photo-
reactivity of 3, which, missing the iodine atom, doesn’t give
XB. While this compound is isostructural with 4, under
irradiation it gives the corresponding cyclobutane with a
100% yield.16 This result can be a confirmation of the role
played by XB in determining the anomalous photoreactivity
observed in 4.
Good-quality single crystals suitable for X-ray analysis of
photoreacted product 5 were grown from chloroform. 5
Crystallizes in the monoclinic P21/n space group as chloro-
form clathrate, with a 1 : 2, 5 : CHCl3 ratio. Being consistent
with the E stereochemistry of starting stilbene 4, the cyclobu-
tane derivative 5 has the rctt stereochemistry, with pairs of
iodotetrafluorobenzene and dimethylaminobenzene pendants
pointing to opposite directions with respect to the plane of the
cyclobutane ring (Fig. 4). Cyclobutane 5 lies, in the crystal, on
an inversion centre and being obtained through a solid state
reaction between two molecules related by a centre of sym-
metry, it has a Ci stereochemistry. The conformation of 5 is
influenced by two intramolecular Hꢀ ꢀ ꢀF bonds, namely
H1ꢀ ꢀ ꢀF1 (2.37 A) and H2ꢀ ꢀ ꢀF4 (2.41 A). These bonds lock
the two fluorinated rings in a position nearly perpendicular to
the cyclobutane ring (the dihedral angle between the mean
square planes of the rings is 86.021). The angle between the
cyclobutane and the dimethylanilino rings is 57.781.
The supramolecular organization of 5 in its crystal packing
is governed by XB, which is by far the dominant intermole-
cular interaction. The cycloadduct 5 possesses two XB donor
sites and two XB acceptor sites and behaves as a 2D hetero-
tetratopic self-complementary tecton. In order to match its
multivalency, a 2D infinite network is formed, which has a
[4.4] topology, if the molecular centroids are used as nodes
(Fig. 5). The Nꢀ ꢀ ꢀI distance is 2.907 A (17% shorter than the
sum of van der Waals radii for N and I), while the Nꢀ ꢀ ꢀI–C
and C–Nꢀ ꢀ ꢀI angles are 176.651 and 102.331, respectively.
Fig. 3 1H-NMR spectra of XB-based self-complementary tectons 4
and 5.
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indication that Nꢀ ꢀ ꢀI XB in 5 is stronger than in 4. This
demonstrates the high coherence of the crystal matrix of 5,
which is based on multiple self-complementary XB.
Conclusions
Molecules with multiple binding sites are important tectons in
supramolecular chemistry. Such heteromultitopic molecules
are designed, a priori, to bind ion pairs19 and for the design
of programmed metallosupramolecular architectures.20 A fas-
cinating goal is also the application of heteromultitopic mole-
cules as ‘‘artificial enzymes’’ for directing the formation of
covalent bonds.21 Heterotopic tectons for XB-based crystal
engineering are definitely rare in the literature.11 A particularly
fine example of these tectons was reported by Desiraju et al.
who synthesized the 4,40-diiodo-400,400 0-dinitrotetraphenyl-
methane and reported its single crystal X-ray structure. This
heterotetratopic self-complementary tecton based on XB self-
assembles in a beautiful halogen-bonded diamondoid net-
work. On the other hand, the covalent synthesis of this tecton
is quite lengthy and gives a low overall yield.22
Fig. 5 A view down the crystallographic c axis of the crystal packing
of the XB-based self-complementary tecton 5 (ball-and-stick style).
Colour code: dark grey, carbon; light grey, hydrogen; blue, nitrogen;
light green, fluorine; green, chlorine; purple, iodine. Halogen bonds
are dotted black lines. Only one population of the two existing ones for
the disordered chloroform molecules has been reported for the sake of
clarity.
With the aim of applying the tools of supramolecular
chemistry to control the solid state synthesis of complex
heterotopic tectons tailored to XB-based crystal engineering,
we have synthesized the 1D self-complementary tecton 4. On
irradiation in the solid state, this tecton undergoes topochemi-
cally controlled photoreaction and yields the heterotetratopic
2D self-complementary tecton 5. This latter tecton self-orga-
nizes in the solid state thanks to strong and directional XB. A
2D architecture is formed wherein large voids are organized
into columns along the crystallographic a axis. These voids are
filled in with clathrated solvent molecules, which can be
removed under low pressure.
These values are consistent with a XB much stronger in tecton
5 than in 4. This may be related to the higher electron density
at N and a lower electron density at I in cyclobutane 5 than in
stilbene 4. Indeed, an intramolecular charge transfer, from the
dimethylamino group to the tetrafluorobenzene ring, may
occur in the stilbene 4 but it is prevented in the cyclobutane
derivative 5. As a consequence of this, the N atom in 5 is
less planarized than in 4 (C–N–C angles in the range
113.40–117.281).
The use of topochemically controlled photoreactions to
conduct molecular synthesis by design of polydentate ligands
for coordination-driven self-assembly of molecular frame-
works has been proven to be a particularly effective strate-
gy.5c,23 The results described in this paper show the first
application of this strategy to the design of heteromultitopic
tectons for XB-based crystal engineering.
The strength and directionality of the Nꢀ ꢀ ꢀI XB prevent the
tendency of tecton 5 to pack more efficiently by optimizing its
pattern of self-complementary p–p stacking interactions. 5
Could form up to eight p–p interactions, which are expected
to be particularly strong due to the opposite sign of the
quadrupolar moments of the involved rings. On the contrary,
no such interactions are formed and large columnar voids are
present along the crystallographic a axis of the halogen-
bonded [4.4] network of 5. These voids are filled in with
disordered chloroform molecules (see ESI, Fig. 6 and 7z),
which orient their acidic hydrogen atoms towards the aniline
rings (aniline ring-centroid–hydrogen distance 3.000 A).17
Removal of the clathrated chloroform can be obtained by
evaporation at reduced pressure, with the crystals retaining
their shapes but becoming opaque. Differential scanning
calorimetry (DSC) analysis of freshly prepared crystals of 5
has demonstrated that chloroform loss starts at room tem-
perature and is complete at 130 1C. Melting of the sample
occurs with decomposition at 251 1C (see ESI, Fig. 8z). While
the overall crystal packing of 4 is determined by both Nꢀ ꢀ ꢀI
XB and p–p interactions, only Nꢀ ꢀ ꢀI XB is present in 5.
Despite of the fact it is hard to directly correlate crystal
packing and the strength of intermolecular interactions to
melting points, nevertheless, the fact that the melting tempera-
ture of 5 is higher than the one of 4, may be a further
Experimental
Materials and methods
Commercial HPLC-grade solvents were used without further
purification. Starting materials were purchased from Sigma–
Aldrich, Acros Organics, and Apollo Scientific. Reactions
were carried out in oven-dried glassware under a nitrogen
atmosphere. 1H-NMR and 19F-NMR spectra were recorded at
ambient temperature with a Bruker AV 500 spectrometer.
Unless otherwise stated, CDCl3 was used as both solvent
and internal standard in 1H-NMR spectra. For 19F-NMR
spectra, CDCl3 was used as solvent and CFCl3 as an internal
standard. IR spectra were obtained using a Nicolet Nexus
FT-IR spectrometer equipped with an UATR unit. Chroma-
tographic separations were performed on silica gel 230–400
mesh. The X-ray crystal structures were determined using a
Bruker SMART APEX diffractometer. Melting points were
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determined with a Reichert instrument by observing the melt-
ing and crystallizing process through an optical microscope.
The photoreaction was carried out in a Rayonet RPR-100
instrument using monochromatic irradiation at l = 300 nm.
DSC analyses were carried out with a Linkam DSC600 hot
stage (10 1C minꢂ1).
19F-NMR (470 MHz, CDCl3): d ꢂ140.0 (2F, m), ꢂ122.5
(4F, m); MS (ESI) m/z 843 (M + H)+. IR (powder, cmꢂ1):
2994, 2882, 1595, 1517, 1465, 1008, 959, 914, 809, 750.
X-Ray crystallography
Crystal data. 4 C16H12F4IN, M = 421.17, prism, 0.34 ꢃ
0.27 ꢃ 0.14 mm3, monoclinic, space group P21/c, a =
10.174(2), b = 11.671(2) c = 13.043(4) A, b = 103.26(3)1,
V = 1507.4(6) A3, Z = 4, Dc = 1.856 g cmꢂ3, F000 = 816,
MoKa radiation, l = 0.71073 A, m = 2.162 mmꢂ1, T =
293(2) K, 2ymax = 61.341, 28 489 reflections collected, 4649
unique (Rint = 0.0297), 3733 with Io 4 2s(Io), absorption
corrections Tmin/Tmax = 0.416. Solved using SIR2002,24 and
refined with SHELX-97,25 full-matrix least squares on F2, 217
parameters, 7 restraints on H atoms parameters, GoF = 1.006,
R1 = 0.0423, wR2 = 0.1048 (all reflections), ꢂ1.30 o Dr o
0.93 e Aꢂ3
Syntheses
N,N-Dimethyl-4-(E)-[2-(2,3,5,6-tetrafluorophenyl)-vinyl]ani-
line 3. 250 mg (0.5 mmol) of phosphonium salt 1 were
suspended in 1 mL of THF at ꢂ70 1C. 0.7 mmol of n-BuLi
(1.6 M) were added and the mixture was warmed up to room
temperature. After 30 min, 150 mg (1 mmol) of aldehyde 2
were added and the mixture was left for 24 h while stirring.
The solution was then washed with a saturated water solution
of NH4Cl, the aqueous phase was extracted 3 times with
CH2Cl2 and the combined organic layers were dried over
Na2SO4. The crude material was purified by chromatography
with n-hexane–CH2Cl2 mixture (2 : 1) as eluent to give 124 mg
of product 3 (84% yield).
Yellow solid; lmax = 372 nm; mp = 127–130 1C; 1H-NMR
(500 MHz, CDCl3): d 7.45 (2H, d, J = 8.8 Hz, H arom.), 7.44
(1H, d, J = 16.1 Hz, CH), 6.87 (1H, d, J = 16.1 Hz, CH), 6.85
(1H, m, H arom.), 6.72 (2H, d, J = 8.8 Hz, H arom.), 3.02
(6H, s, CH3); 19F-NMR (470 MHz, CDCl3): d ꢂ144.7 (2F, m),
ꢂ141.3 (2F, m); MS (ESI) m/z 295 (M+). IR (powder, cmꢂ1):
3074, 2889, 2807, 1599, 1522, 1492, 1446, 1349, 1225, 1165,
1042, 969, 926, 850, 806, 705.
5 C32H24F8I2N2 ꢀ 2CHCl3, M = 1081.07, prism, 0.40 ꢃ 0.29
ꢃ 0.17 mm3, monoclinic, space group P21/n, a = 6.1825(8),
b = 18.9953(15) c = 16.605(2) A, b = 90.93(1)1, V =
1949.8(4) A3, Z = 2, Dc = 1.841 g cmꢂ3, F000 = 1048, MoKa
radiation, l = 0.71073 A, m = 2.091 mmꢂ1, T = 293(2) K,
2ymax = 61.281, 40 089 reflections collected, 5976 unique (Rint
= 0.0212), 5206 with Io 4 2s(Io), absorption corrections Tmin
/
Tmax = 0.830. Solved using SIR2002,24 and refined with
SHELX-97,25 full-matrix least squares on F2, 279 parameters,
6 restraints on the aromatic H atoms parameters, GoF =
1.045, R1 = 0.0327, wR2 = 0.0801 (all reflections), ꢂ0.47 o
Dr o 0.67 e Aꢂ3. CCDC reference numbers 604218 (4) and
604217 (5). For crystallographic data in CIF or other electro-
nic format see DOI: 10.1039/b605958a
N,N-Dimethyl-4-(E)-[2-(2,3,5,6-tetrafluoro-4-iodophenyl)-vinyl]
aniline 4. 420 mg (1.42 mmol) of compound 3 were stirred in 4
mL of THF at ꢂ70 1C. 1.71 mmol of n-BuLi (1.6 M) were
added and the mixture was warmed up to room temperature.
After 30 min, the reaction was cooled down to ꢂ70 1C and a
solution of 505 mg (1.99 mmol) of I2 in 1 mL of THF was
added. After 2 h, the solution was then washed with a
saturated water solution of Na2S2O3, the aqueous phase was
extracted 3 times with CH2Cl2 and the combined organic
layers were dried over Na2SO4. The crude material was
purified by chromatography with n-hexane–CH2Cl2 mixture
(2 : 1) as eluent to give 508 mg of product (85% yield).
Yellow solid; lmax = 382 nm; mp = 210 1C; 1H-NMR (500
MHz, CDCl3): d 7.45 (1H, d, J = 16.7 Hz, CH), 7.44 (2H, d, J
= 8.8 Hz, H arom.), 6.83 (1H, d, J = 16.7 Hz, CH), 6.71 (2H,
d, J = 8.8 Hz, H arom.), 3.02 (6H, s, CH3); 19F-NMR (470
MHz, CDCl3): d ꢂ142.3 (2F, m), ꢂ123.3 (2F, m); MS (ESI)
m/z 422 (M + H)+. IR (powder, cmꢂ1): 3089, 2899, 2820,
1595, 1519, 1466, 1445, 1332, 1219, 1192, 1165, 1125, 1054,
954, 940, 814, 797.
Acknowledgements
We would like to thank EU (COST D29/0011/03 and D31/
0017/05), MIUR (PRIN 2005), and Fondazione Cariplo
(Bandi aperti 2005—Progetti finalizzati al reclutamento di
giovani ricercatori internazionali) for financial support. Ales-
sandra Forni is also acknowledged for the helpful discussion.
References
1 G. W. V. Cave, C. L. Raston and J. L. Scott, Chem. Commun.,
2001, 2159.
2 G. M. J. Schmidt, Pure Appl. Chem., 1971, 27, 647.
3 (a) J. Liu, N. L. Wendt and K. J. Boarman, Org. Lett., 2005, 7,
1007; (b) J. Liu and K. J. Boarman, Chem. Commun., 2005, 340; (c)
L. R. MacGillivray, CrystEngComm, 2004, 6, 77; (d) K. Vishnu-
murthy, T. N. G. Row and K. Venkatesan, J. Chem. Soc., Perkin
Trans. 2, 1997, 615; (e) K. Vishnumurthy, T. N. G. Row and K.
Venkatesan, J. Chem. Soc., Perkin Trans. 2, 1996, 1475, and
references cited therein; (f) G. R. Desiraju, R. Kamala, B. H.
Kumari and J. A. R. P. Sarma, J. Chem. Soc., Perkin Trans. 2,
1984, 181.
4 (a) Q. Chu, D. C. Swenson and L. R. MacGillivray, Angew. Chem.,
Int. Ed., 2005, 44, 3569; (b) Y. Vida Pol, R. Suau, E. Perez-
Inestrosa and D. M. Bassani, Chem. Commun., 2004, 1270; (c) V.
Darcos, K. Griffith, X. Sallenave, J.-P. Desvergne, C. Guyard-
Duhayon, B. Hasenknopf and D. M. Bassani, Photochem. Photo-
biol. Sci., 2003, 2, 1152; (d) N. Shan and W. Jones, Green Chem.,
2003, 5, 728; (e) D. G. Amirsakis, A. M. Elizarov, M. A. Garcia-
Garibay, P. T. Glink, J. F. Stoddart, A. J. P. White and D. J.
Williams, Angew. Chem., Int. Ed., 2003, 42, 1126; (f) H. Zitt, I. Dix,
H. Hopf and P. G. Jones, Eur. J. Org. Chem., 2002, 2298; (g)
4,40-[(1a,2a,3b,4b)-2,4-bis-(2,3,5,6-tetrafluoro-4-iodophenyl)-
cyclobutane-1,3-diyl]-bis-(N,N-dimethyl)aniline 5. Finely pow-
dered crystals of 4 put between two glass slides were irradiated
for 24 h. The crude material was then purified by chromato-
graphy with toluene as eluent to give the cycloadduct 5 in 80%
isolated yield.
Pale yellow solid; mp = 251 1C (dec.); 1H-NMR (500 MHz,
CDCl3): d 7.07 (4H, d, J = 8.6 Hz, H arom.), 6.59 (4H, d, J =
8.6 Hz, H arom.), 4.80 (4H, s, CH), 2.89 (12H, s, CH3);
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View Article Online
D. G. Amirsakis, M. A. Garcia-Garibay, S. J. Rowan, J. F.
Stoddart, A. J. P. White and D. J. Williams, Angew. Chem., Int.
Ed., 2001, 40, 4256; (h) K. S. Feldman and R. F. Campbell, J. Org.
Chem., 1995, 60, 1924.
5 (a) G. R. Desiraju and J. A. R. P. Sarma, J. Chem. Soc., Chem.
Commun., 1983, 45; (b) G. R. Desiraju and J. A. R. P. Sarma, J.
Chem. Soc., Chem. Commun., 1991, 1239; (c) C. V. K. Sharma, K.
Panneerselvam, L. Shimoni, H. Katz, H. L. Carrell and G. R.
Desiraju, Chem. Mater., 1994, 6, 1282; (d) W. J. Feast, P. W.
Griffiths, J. M. Rawson and J. Hulliger, Chem. Commun., 2001,
2488; (f) A. R. P. S. Jagarlapudi, F. H. Allen, V. J. Hoy, J. A. K.
Howard, R. Thaimattam, K. Biradha and G. R. Desiraju, Chem.
Commun., 1997, 101; (g) A. D. Bond, J. Griffiths, J. M. Rawson
and J. Hulliger, Chem. Commun., 2001, 2488.
12 J. Leroy, B. Schollhorn, J.-L. Syssa-Magale, K. Boubekeur and
´
¨
P. Palvadeau, J. Fluorine Chem., 2004, 125, 1379.
13 See: http://www.webelements.com.
14 (a) R. Glaser, N. Knotts and H. Wu, Chemtracts: Org. Chem.,
2003, 16, 643; (b) R. Glaser, in Anisotropic Organic Materials-
Approaches to Polar Order, ACS Symposium Series 798, ed. R.
Glaser and P. Kaszynski, American Chemical Society, Washington
DC, 2001.
15 (a) G. R. Desiraju and V. Kannan, Proc. Indian Acad. Sci., Chem.
Sci., 1986, 96, 351; (b) S. K. Kearsley, in Organic Solid State
Chemistry, ed. G. R. Desiraju, Elsevier, Amsterdam, 1987, pp.
69–113.
Lovenich, H. Puschmann and C. Taliani, Chem. Commun., 2001,
¨
505; (e) G. W. Coates, A. R. Dunn, L. M. Henling, J. W. Ziller, E.
B. Lobkovsky and R. H. Grubbs, J. Am. Chem. Soc., 1998, 120,
3641; (f) G. W. Coates, A. R. Dunn, L. M. Henling, D. A.
Dougherty and R. H. Grubbs, Angew. Chem., Int. Ed. Engl.,
1997, 36, 248; (g) J. H. Williams, Acc. Chem. Res., 1993, 26, 593.
6 K. I. Nattinen and K. Rissanen, Cryst. Growth Des., 2003, 3,
339.
7 (a) D. B. Varshney, X. Gao, T. Friscic
´
and L. R. MacGillivray,
and L. R.
16 P. Metrangolo, F. Meyer, T. Pilati and G. Resnati, unpublished
results.
Angew. Chem., Int. Ed., 2006, 45, 646; (b) T. Friscic
´
MacGillivray, Chem. Commun., 2005, 5748; (c) N. Shan and W.
Jones, Tetrahedron Lett., 2003, 44, 3687; (d) G. S. Papaefstathiou,
A. J. Kipp and L. R. MacGillivray, Chem. Commun., 2001, 2462;
(e) L. R. MacGillivray, J. L. Reid and J. A. Ripmeester, J. Am.
Chem. Soc., 2000, 122, 7817.
17 Such CH–p interactions are effective only if the distances are
shorter than 3.1 A18
.
18 G. Grossmann, M. J. Potrzebowski, S. Olejniczak, N. E. Zio"-
´
kowska, G. D. Bujacz, W. Ciesielski, W. Prezdo, V. Nazarov and
V. Golovko, New J. Chem., 2003, 27, 1095, and references cited
therein.
8 P. Metrangolo, H. Neukirch, T. Pilati and G. Resnati, Acc. Chem.
Res., 2005, 38, 386.
19 As an example: D. Garozzo, G. Gattuso, A. Notti, A. Pappalardo,
S. Pappalardo, M. F. Parisi, M. Perez and I. Pisagatti, Angew.
Chem., Int. Ed., 2005, 44, 4892.
20 C. J. Baylies, L. P. Harding, J. C. Jeffrey, T. Riis-Johannessen and
C. R. Rice, Angew. Chem., Int. Ed., 2004, 43, 4515.
´
21 (a) D. B. Varshney, X. Gao, T. Friscic and L. R. MacGillivray,
9 (a) E. Guido, P. Metrangolo, W. Panzeri, T. Pilati, G. Resnati, M.
Ursini and T. A. Logothetis, J. Fluorine Chem., 2005, 126, 197; (b)
T. Caronna, R. Liantonio, T. A. Logothetis, P. Metrangolo, T.
Pilati and G. Resnati, J. Am. Chem. Soc., 2004, 126, 4500.
10 (a) P. Metrangolo and G. Resnati, Chem.–Eur. J., 2001, 7, 2511; (b)
P. Metrangolo and G. Resnati, in Encyclopedia of Supramolecular
Chemistry, ed. J. L. Atwood and J. W. Steed, Marcel Dekker Inc.,
New York, 2004, p. 628; (c) P. Metrangolo, F. Meyer, G. Resnati
and M. Ursini, in Fluorine-containing synthons, ACS Symposium
Series 911, ed. V. A. Soloshonok, Oxford University Press/Amer-
ican Chemical Society, Washington DC, 2005, p. 513.
Angew. Chem., Int. Ed., 2006, 45, 646; (b) F. Diederich and P. J.
Stang, Templated Organic Synthesis, Wiley-VCH, Weinheim, 2000;
(c) M. C. T. Fyfe and J. F. Stoddart, Acc. Chem. Res., 1997, 30,
393.
22 R. Thaimattam, C. V. K. Sharma, A. Clearfield and G. R.
Desiraju, Cryst. Growth Des., 2001, 1, 103.
11 (a) A. C. B. Lucassen, M. Vartanian, G. Leitus and M. E. van der
Boom, Cryst. Growth Des., 2005, 5, 1671; (b) R. Glaser, N. Chen,
H. Wu, N. Knotts and M. Kaupp, J. Am. Chem. Soc., 2004, 126,
4412; (c) S. Berski, Z. Ciunik, K. Drabent, Z. Latajka and J.
Panek, J. Phys. Chem. B, 2004, 108, 12327; (d) P. K. Thallapally,
G. R. Desiraju, M. Bagieu-Beucher, R. Masse, C. Bourgogne and
J. F. Nicoud, Chem. Commun., 2002, 1052; (e) A. D. Bond, J.
23 G. S. Papaefstathiou, T. D. Hamilton, T. Friscic
MacGillivray, Chem. Commun., 2004, 270.
´
and L. R.
24 A. Altomare, G. Cascarano, C. Giacovazzo, A. Guagliardi, M. C.
Burla, G. Polidori and M. Camalli, J. Appl. Crystallogr., 1994, 27,
435.
25 G. M. Sheldrick, SHELXL-97, Program for refinement of crystal
structures, University of Gottingen, Germany, 1997.
¨
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1402 | New J. Chem., 2006, 30, 1397–1402