Halogen-bonded and interpenetrated networks through the self-assembly of diiodoperfluoroarene and tetrapyridyl tectons

Article abstract of DOI:10.1016/j.jfluchem.2010.06.001

The formation of two organic interpenetrated networks on halogen bonding driven self-assembly of diiodoperfluorarenes with tetrapyridyl tectons is described. Both architectures exhibit two-dimensional square 4⁴ networks; with either a 2-fold interpenetration of class IIa or a 3-fold interpenetration of class Ia. Diiodoperfluoroarenes are proven robust tectons in the design of interpenetrated networks based on the expansion strategy.

Full text of DOI:10.1016/j.jfluchem.2010.06.001

Journal of Fluorine Chemistry 131 (2010) 1218–1224
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Halogen-bonded and interpenetrated networks through the self-assembly of
diiodoperfluoroarene and tetrapyridyl tectons
a
c
d
a,b,**
a,b
Michele Baldrighi a, Pierangelo Metrangolo
, Franck Meyer , Tullio Pilati , Davide Proserpio ,
Giuseppe Resnati a,b,c, , Giancarlo Terraneo
*
a NFMLab - D.C.M.I.C. ‘‘Giulio Natta’’, Politecnico di Milano, Via L. Mancinelli 7, 20131 Milan, Italy
b CNST - IIT@POLIMI, Politecnico di Milano, Via G. Pascoli 70/3, 20133 Milan, Italy
c C.N.R. - I.S.T.M., University of Milan, Via C. Golgi 19, 20133 Milan, Italy
d Department of Structural Chemistry and Inorganic Stereochemistry, University of Milan, 21, via Venezian, 20133 Milan, Italy
A R T I C L E I N F O
A B S T R A C T
Article history:
The formation of two organic interpenetrated networks on halogen bonding driven self-assembly of
diiodoperfluorarenes with tetrapyridyl tectons is described. Both architectures exhibit two-dimensional
square 44 networks; with either a 2-fold interpenetration of class IIa or a 3-fold interpenetration of class
Ia. Diiodoperfluoroarenes are proven robust tectons in the design of interpenetrated networks based on
the expansion strategy.
Received 18 April 2010
Received in revised form 28 May 2010
Accepted 1 June 2010
Available online 10 June 2010
ß 2010 Elsevier B.V. All rights reserved.
Keywords:
Diiodoperfluoroarenes
Self-assembly
Halogen bonding
Interpenetrated networks
Supramolecular chemistry
1. Introduction
coordination. Quite often organic interpenetrated networks are
formed in the pursuit of porous lattice structures when tetra-
The design and self-assembly of interpenetrated networks is an
important topic in supramolecular chemistry. Interpenetrating
networks can be thought of as polymeric analogues of molecular
catenanes and rotaxanes, and they involve the intimate entangle-
ment of two or more polymeric networks [1]. Defining feature of
interpenetration is the condition that the entanglement of the
topological nets is such that, although there is no direct connection
between the networks, they cannot be separated (in a topological
sense) without requiring the breaking of network connections.
Infinite 2D and 3D networks with a variety of interpenetration
modes have been built [2].
dentate tectons are connected by organic linkers. The geometric
and chemical attributes of linkers allow for producing convenient-
ly open framework topologies. When the 2D or 3D primary
networks, formed via HB or metal–ligand coordination, possess
open structures with large voids, the starting building modules can
be accommodated within these voids, namely interpenetration is
present in the overall crystal architecture and reduces the
unoccupied space within the crystal lattice.
As a complement of HB, halogen bonding (XB), namely any
noncovalent interactions involving halogen atoms as acceptors
of electronic density, is emerging as
a new item in the
Much of the recent progress in this area is based on tailor-made
building blocks, either organic or metal–organic, and their self-
assembly was based on hydrogen bonding (HB) and metal–ligand
supramolecular toolbox [3]. During the last decade, this
interaction has ensured the deliberate construction of supramo-
lecular architectures involving ionic or neutral tectons [4] and
showing interesting properties in diverse areas of Materials
Science [5]. Few examples of halogen-bonded interpenetrated
networks have been reported in the literature so far [6].
However, XB has proven to exert an unprecedented level of
control over the formation of entangled structures. This level of
control is related to the remarkably high directionality of the XB
which preferentially develops on the extension of the C-halogen
covalent bond, the stronger XBs resulting in the more linear
arrangements.
* Corresponding author at: NFMLab - D.C.M.I.C. ‘‘Giulio Natta’’, Politecnico di
Milano, Via L. Mancinelli 7, 20131 Milan, Italy. Tel.: +39 02 2399 3032;
fax: +39 02 2399 3180.
** Co-corresponding author at: NFMLab - D.C.M.I.C. ‘‘Giulio Natta’’, Politecnico di
Milano, Via L. Mancinelli 7, 20131 Milan, Italy. Tel.: +39 02 2399 3041;
fax: +39 02 2399 3180.
E-mail addresses: pierangelo.metrangolo@polimi.it (P. Metrangolo),
giuseppe.resnati@polimi.it (G. Resnati).
0022-1139/$ – see front matter ß 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2010.06.001

M. Baldrighi et al. / Journal of Fluorine C
[
hemistry 131 (2010) 1218–1224
1219
The XB directionality is related to the fact that the electron
density around halogen atoms is anisotropically distributed and in
the elongation of the C-halogen bond a region of positive
electrostatic potential is present (s-hole) [7]. This positive region
accounts for the directionality of the approach of the high electron
density site of the electron donor to the halogen atom.
As a consequence of the high polarizability of the iodine atom
and the ability of fluorine to boost the electron-acceptor potential
of iodine, diiodoperfluoroarenes are particularly effective and
telechelic XB-donors. Moreover, we have already demonstrated
that the geometry of the XB-donor sites on starting diiodoper-
fluoroarene modules strongly influences the geometry of the
noncovalent co-polymers obtained on self-assembly with XB-
acceptors. For instance, when 1,4-diiodotetrafluorobenzene is co-
crystallized with 4,40-bipyridine (XB-acceptor), linear 1D infinite
chains are obtained wherein the two modules alternate thanks to
the presence of Nꢀ ꢀ ꢀI XBs [8]. On the other hand, when 1,2-
diiodotetrafluorobenzene is co-crystallized with the same XB-
acceptor, infinite chains wherein the two modules alternate are
obtained once more, and the 608 angle of the XB-donor sites on the
perfluoroarene ring translates into the wave-like arrangement of
the infinite chain [9]. For these reasons, diiodoperfluoroarenes can
be considered very reliable XB-tectons in geometry-based crystal
engineering.
Scheme 1. XB-acceptor (1 and 2) and XB-donor (3 and 4) modules involved in the
self-assembly processes.
linkers of tetrapyridyl tectons. The selected building blocks
functionalized with four pyridyl rings are the tetrapyridylpentaer-
ythritol 1 (TPPE) and the tetrakis(4-pyridyl)cyclobutane 2 (TPCB).
Few interpenetrated organic networks have been obtained from
the tetrapyridyl XB-acceptors 1 and a 3-fold interpenetrated
organometallic network was formed when a Zn2+ salt was bound to
two TPCB and two dipyridylethylene molecules [11].
1,4-Diiodotetrafluorobenzene 3 was chosen as XB-donor linker.
Considering that the directionality of XB can translate the
geometry of the starting modules into the topology of the obtained
supramolecular architectures (Scheme 1), the simplest way to
enlarge the cavities of the primary network formed on self-
assembly of tectons with a given geometry was to increase the
length of one, or both, the starting modules. In other words, our
concept was to tune the size of the cavity of the primary networks
by changing the size of the compounding modules. 4,40-Diiodooc-
tafluorostilbene 4 was thus prepared with the aim to obtain
networks with larger cavities allowing for higher interpenetration.
The use of the diiodoperfluoroarenes 3 and 4 in the formation of
interpenetrated networks gives also the possibility to study how
As to interpenetrated networks sustained by XB, we have
recently described the self-assembly of a three-component system
made up of the kryptand K.2.2.2, KI, and
a,v-diiodoperfluoroalk-
anes. The scavenging of potassium cations by the K.2.2.2 allowed
for obtaining naked iodide anions that were able to bind three
different perfluorinated modules resulting into corrugated honey-
comb-like (6,3) networks. When 1,6-diiodoperfluorohexane and
1,8-diiodoperfluorooctane were used, the obtained (6,3) networks
were large enough to give rise to the fascinating and rare
interpenetration pattern of Borromean links [10].
The rigid rod-like behaviour of perfluoroalkyl chains and the
remarkable directionality of XB were also employed for the
deliberate construction of highly interpenetrated neutral networks
by self-assembly of diiodoperfluorolkanes with tetradentate XB-
acceptors. Specifically, the self-assembly of tetrapyridylpentaer-
ythritol with 1,6-diiodoperfluorohexane and 1,8-diiodoperfluor-
ooctane afforded architectures exhibiting 2D square 44 networks
with 4-fold and 5-fold interpenetration of class IIIa and class Ia,
respectively. On the other hand, when tetrapyridylpentaerythritol
self-assembles with 1,4-diiodoperfluorobutane or with tetrakis(4-
iodotetrafluorophenyl)pentaerythritol, a rare 8-fold diamondoid
network of class Ia or a notable 10-fold diamondoid network were
formed. This last interpenetration is one of the highest degrees of
interpenetration reported to date for organic structures [6a].
With these results in mind, we decided to investigate the use of
differently sized diiodoperfluoroarenes as telechelic and XB-based
the remarkable tendency of perfluoroarenes to give rise to
stacking interactions influences the network topologies and
interpenetration modes [12].
pꢀ ꢀ ꢀp
Specifically, the pentaerythritol-based module 1 was self-
assembled with the XB-donor module 4 and the tetrapyridylcy-
clobutane 2 with the benzene derivative 3. The obtained structures
5 and 6 both exhibit two-dimensional square 44 networks, the
former having a 3-fold interpenetration of class Ia and the latter a
2-fold interpenetration of class IIa (Scheme 2).
[(Scheme_2)TD$FIG]
Scheme 2. Formation of square networks 5 and 6 upon self-assembly of modules 1 and 4, and 2 and 3, respectively.

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_
2. Results and discussion
2.1. Synthesis of starting building blocks
Entangled systems are frequently formed from tetradentate
tectons, the molecular geometry of which is translated into the
topology of the obtained framework thanks to the use of rigid
organic linkers which connect the tetradentate tectons and
increase their spacing in a process which is often referred to as
expansion [13]. Tetradentate tectons based on pentaerythritol
and cyclobutane cores appeared to be a particularly attractive
starting building block as several architectures incorporating
this tetradentate core have been reported [14]. Modules 1 and 2
were thus used in this study. The tetrakis(4-pyridyl)pentaery-
thritol (1) was prepared by an improved synthetic protocol
starting from pentaerythritol (7) and 4-chloropyridine (8) in the
presence of tBuOK in DMSO (Scheme 3). The rctt-tetrakis(4-
pyridyl)cyclobutane (2) was synthesized by irradiating at
300 nm the co-crystal obtained from trans-1,2-bis(4-pyridy-
l)ethylene and tetrakis(4-iodotetrafluoro-phenyl)pentaerythri-
tol [15]. We have already reported that the supramolecular
control exerted by the crystal packing over the regio- and
stereochemistry of the [2 + 2] photochemical cycloaddition
Fig. 1. Schematic representation (spacefill style by using Mercury 2.3 [17]) of the 2D
square network formed on self-assembly of molecules 1 and 4. The network given
by molecules A and C is reported, molecules B and D give a very similar network. H
atoms have been omitted for clarity; colour codes: grey, carbon; yellow-green,
fluorine; blue, nitrogen; red, oxygen; purple, iodine. (For interpretation of the
references to color in this figure legend, the reader is referred to the web version of
the article.)
2.2. Synthesis and crystal structure analysis of the complex 5
The co-crystal 5 was obtained upon slow and isothermal
evaporation at room temperature of a 9:1 MeOH/CH2Cl2 solution
containing the tetrapyridyl compound 1 and the diiodinated
module 4 in a 1:2 ratio. The co-crystal 5 melts at 242–244 8C,
namely much higher than the starting compounds (1 melts at
198 8C, and 4 melts at 207–210 8C) thus confirming the expected
formation of a new crystalline species, rather than a mechanical
mixture of starting compounds.
Single crystal X-ray diffraction analyses of 5 shows [16] that the
pentaerythrytol derivative 1 and the diiodinated module 4 are
present in a 1:2 ratio. Nꢀ ꢀ ꢀI XBs are largely responsible for the self-
assembly of the complementary modules 1 and 4 to give co-crystal
secures the formation of
stereochemical yields.
2 in quantitative chemical and
Our previous studies demonstrated that differently sized
diiodoperfluoroalkanes were particularly successful organic lin-
kers in the expansion strategy to highly interpenetrated networks
[6a]. In this paper we decided to explore if diiodoperfluoroarenes
are equally effective linkers. 1,4-Diiodotetrafluorobenzene 3 is
commercially available and 4,40-diiodooctafluorostilbene 4 was
synthesized by a two step sequence (Scheme 4). First a Wittig
reaction between triphenyl-(2,3,5,6-tetrafluorobenzyl)phospho-
nium bromide (9) and 2,3,5,6-tetrafluorobenzaldehyde (10) gave
the trans-1,2-bis-(1,2,4,5-tetrafluorophenyl)-ethylene (11) which
was diiodinated to the target product 4 with n-BuLi/I2 (94% overall
yield).
˚
5. Nꢀ ꢀ ꢀI distances span the range of 2.785–2.819 A (approximately
80% of the sum of Van der Waals radii of N and I) and Nꢀ ꢀ ꢀI–C angles
are 175.3–178.88, consistent with the directionality typical for XBs.
The topology of the primary network formed by the self-
assembly of 1 and 4 is a nice example of the paradigm of the
expansion of a tetratopic starting module by a linear linker. Each
pentaerythritol derivative 1 behaves as a tetratopic XB-acceptor
and each stilbene module 4 functions as a linear and ditopic XB-
donor spacing two tetradentate pentaerythritol derivatives 1. 2D,
parallel, and square networks having a 44 topology are formed and
they are compounded by rhombic meshes having a side length of
[(Scheme_3)TD$FIG]
˚
31.208 A (Fig. 1).
The asymmetric unit of the co-crystal 5 consists in two
molecules of 4, indicated here as A and B, and two half molecules of
1, indicated as C and D, both with the mass centre on a
crystallographic 2-fold symmetry axis (Fig. 2). Due to this
asymmetric unit, two independent and parallel 2D square
networks containing molecules A and C, and B and D, respectively,
are obtained. The couples of molecule A, B and C, D have very
similar conformations, and the directionality of the XB transfer this
similarity to the two independent and parallel 2D square networks,
closely resembling each other.
Scheme 3. Synthesis of XB-acceptor module 1.
[(Scheme_4)TD$FIG]
The overall crystal packing is formed by alternating layers
containing either A, C or B, D molecules. Each layer result from the
interpenetration of three different square networks with the
˚
shortest interpenetration vector [1 0 0] of 19.707 A (Figs. 3 and 4).
Finally, it may be worth noting that few short contacts other
than Nꢀ ꢀ ꢀI XBs contribute to the crystal packing of the complex 5.
Modules 1 and 4 of the same layer interact each other through a net
˚
of Hꢀ ꢀ ꢀF HBs (the shorter being 2.44 A), and modules 1 and 4 of
adjacent layers loosely interact through weak
involving perfluoroarene and pyridine rings (centroid-centroid
p p stacking
ꢀ ꢀ ꢀ
˚
Scheme 4. Synthesis of XB-donor module 4.
distance of 3.754 A).

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M. Baldrighi et al. / Journal of Fluorine C
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hemistry 131 (2010) 1218–1224
1221
Fig. 2. Asymmetric unit of co-crystal 5 (by using ORTEP-3 [18]) with numbering
scheme and atomic displacement parameters (ADPs) at 50% probability level. Two
complete TPPE molecules C and D are reported at the corners. H atoms have been
omitted for clarity; colour codes: grey, carbon; yellow-green, fluorine; blue,
nitrogen; red, oxygen; purple, iodine. (For interpretation of the references to color
in this figure legend, the reader is referred to the web version of the article.)
Fig. 4. Top: schematic representation (by using TOPOS 4.0 [19]) of the 3-fold
interpenetrated network of 5. Colours as in Fig. 3, top. Bottom: TOPOS schematic
representation of the 2-fold interpenetrated networks of 6. Colours as Fig. 7, top.
(For interpretation of the references to color in this figure legend, the reader is
referred to the web version of the article.)
2.3. Synthesis and crystal structure analysis of the complex 6
Single crystals of the complex 6 were prepared by isothermal
(r.t.) evaporation of a methanol solution containing the two
starting modules 2 and 3 in a 1:2 ratio. Good-quality single crystals
in the form of colourless prisms were obtained after 3 days. The
crystals melted at 190–193 8C, much higher than the mean value of
the starting compounds melting points (218–220 8C and 108–
110 8C for 2 and 3, respectively).
The single crystal X-ray diffraction analysis reveals the crystal
structure of 6 presents several similarities to 5. The starting
modules 2 and 3 are present in a 1:2 ratio (Fig. 5), they behave as a
tetratopic XB-acceptor and as a linear ditopic XB-donor, respec-
tively, and the diiodinated module 3 functions as a linear spacer
expanding the tetradentate module 2.
˚
2.794–3.040 A (the shortest one corresponding to approximately
79% of the sum of Van der Waals radii) and Nꢀ ꢀ ꢀI–C angles are
162.2–177.78, once again perfectly consistent with the preferred
directionality of the XB. Also in complex 5, Nꢀ ꢀ ꢀI XBs produce 2D
square networks having a 44 topology (Fig. 6) and the overall
crystal packing consists in loosely interacting layers formed on
interpenetration of the square networks having a 44 topology
(Fig. 7). However, the meshes of the square networks of 6 are
˚
parallelograms having sides of 21.051 and 21.681 A and the layers
present in the overall crystal packing are formed thanks to a 2-fold
interpenetration of class IIa [21] (interpenetration vector along
[1 0 1]) (Figs. 4 and 7).
Here too Nꢀ ꢀ ꢀI XBs are largely responsible for the complemen-
tary modules self-assembly [20]. Nꢀ ꢀ ꢀI distances span the range
[(Fig._3)TD$FIG]
[F(ig._5)TD$FIG]
Fig. 3. Top: view along the c-axis of 3-fold interpenetration for one layer formed by
A and C molecules. Molecules B and D give very similar interpenetrating meshes.
Bottom: view along the b-axis of the alternating layers formed by A, C molecules
(bright brown) and B, D molecules (dark brown) in co-crystal 5. (For interpretation
of the references to color in this figure legend, the reader is referred to the web
version of the article.)
Fig. 5. Asymmetric unit in the crystal structure of 6 (by using ORTEP-3 [18]) with
numering scheme and ADPs at 50% probability level. H atoms have been omitted for
clarity; colour codes: grey, carbon; yellow-green, fluorine; blue, nitrogen; purple,
iodine. (For interpretation of the references to color in this figure legend, the reader
is referred to the web version of the article.)

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M. Baldrighi et al. / Journal of Fluorine Chemistry 131 (2010) 1218–1224
Clearly the remarkable tendency of perfluoroarenes to give rise to
stacking interactions does not influence their reliability in
pꢀ ꢀ ꢀp
geometry-based crystal engineering.
In summary, XB-donor and -acceptor modules with similar
geometries and different sizes afford self-assembled networks
with similar topologies and different sizes. The larger modules
afford more extended networks and the resulting larger voids
allow for a higher interpenetration. The generality of this design
principle is still under study by co-crystallizing 1 with 3 and 2 with
4 and using 2,4,6-triiodotrifluorobenzene as tridentate XB-donor
spacers of bi- and tridentate XB-acceptors.
Fig. 6. Schematic representation (spacefill style by using Mercury 2.3 [17]) of the 2D
square network formed on self-assembly of molecules 2 and 3, forming the complex
6. H atoms have been omitted for clarity; colour codes: grey, carbon; yellow-green,
fluorine; blue, nitrogen; purple, iodine. (For interpretation of the references to color
in this figure legend, the reader is referred to the web version of the article.)
4. Experimental
4.1. Materials and methods
[(Fig._7)TD$FIG]
Commercial HPLC-grade solvents were used without further
purification. Starting materials were purchased from Sigma–
Aldrich, Acros Organics, and Apollo Scientific. The mass spectra
were recorded on a GC–MS AGILENT GC-MSD5975. 1H NMR and
19F NMR spectra were recorded at ambient temperature with a
Bruker AV500 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 internal
standard. All chemical shift values are given in ppm. Melting points
were determined with a Reichert instrument by observing the
melting and crystallising process through an optical microscope.
The photoreaction was carried out in
instrument using monochromatic irradiation at
a
Rayonet RPR-100
= 300 nm.
l
4.2. Tetrakis(4-pyridyl)pentaerythritol (1)
68 mg (0.5 mmol) of pentaerythritol (7) and 280 mg (2.5 mmol)
of tBuOK are stirred in 1 mL of DMSO at room temperature for
40 min. Then, 590 mg (10.4 mmol) of 4-chloropyridine (8) diluted
in 1 mL of DMSO are added slowly and the reaction is heated at
50 8C. After 24 h, a saturated aqueous solution of NaCl is added, the
aqueous layer is extracted 4 times with CH2Cl2 and the combined
organic layers are dried over Na2SO4. After evaporation of the
solvent, the crude material is chromatographed on silica gel (240–
400 mesh, eluent CH2Cl2/MeOH 2:1) to give 200 mg of the
tetrakis(4-pyridyl)pentaerythritol (1) in 90% yield. mp = 198 8C; 1H
Fig. 7. Top: schematic view of the 2-fold interpenetration for one layer in co-crystal
6. Bottom: overall crystal packing in 6 formed by loosely interacting layers.
NMR:
d, J = 6.4 Hz, H arom.); IR:
1424, 1278, 1214, 1025, 842, 816, 654 cmꢁ1
d
4.47 (8H, s, CH2), 6.80 (8H, d, J = 6.4 Hz, H arom.), 8.40 (8H,
3. Conclusions
n
max = 3025, 2944, 1598, 1504, 1464,
.
This paper described how the supramolecular architecture 5 is
composed of alternating layers of independent 2D square networks
with a 3-fold interpenetration. The individual nets in the layer are
related by a unique vector of translation and are classified as class
Ia. Similarly, the overall crystal packing of the co-crystal 6 is
formed by layers of parallel square networks with a 2-fold
interpenetration of class IIa.
4.3. Trans-1,2-bis-(1,2,4,5-tetrafluorophenyl)-ethylene (11)
600 mg (1.19 mmol) of triphenyl-(2,3,5,6-tetrafluoro-benzyl)-
phosphonium bromide (9) and 62 mg (1.54 mmol) of NaH are
stirred in 3 mL of DMF for 30 min. 0.15 mL (1.31 mmol) of 2,3,5,6-
tetrafluorobenzaldehyde (10) are then added to the mixture and
the solution is heated at 40 8C. After 3 h, the reaction is poured on
H2O and the white solid is filtered and residue is chromatographied
on silica gel (240–400 mesh, eluent n-hexane/CH2Cl2 4:1) to give
339 mg of trans-1,2-bis-(1,2,4,5-tetrafluorophenyl)-ethylene (11)
2
˚
The rhombs of 5 are 591 A and the parallelograms of 6 are
2
˚
358 A , namely the network meshes in 5 are larger than in 6. This
diversity is related to the different sizes of starting module: The
distances between adjacent nitrogens of the same molecule in the
same mesh are 11.9 and 5.6 A for tetrapyridylpentaerythritol 1 and
in 88% yield. mp = 135–138 8C; 1H NMR:
d
7.03 (2H, m, H arom.),
˚
9.6, and 5.3 A for tetrapyridylcyclobutane 2, the distances between
7.46 (2H, s, CH55CH); 19F NMR:
d
= ꢁ142.9 (4F, m, CF–C), ꢁ139.8
˚
adjacent iodines in the same molecule in the same mesh are 13.7 A
(4F, m, CF–CH); m/z (EI): 324 {Mꢂ+}.
˚
˚
for diiodostilbene 4 and 7.0 A for diiodobenzene 3. The direction-
ality of the XB can transfer these molecular differences to the
supramolecular networks thanks to the ability of diiodoperfluor-
oarenes to work cleanly as XB-donor spacers of XB-acceptors.
The larger voids present in 5 allow for higher interpenetration.
Diiodoperfluoroarenes are thus proven robust tectons in the design
of interpenetrated networks based on the expansion strategy [13].
4.4. Trans-1,2-bis-(2,3,5,6-tetrafluoro-4-iodophenyl)-ethylene (4)
300 mg (0.92 mmol) of perfluorinated olefine derivative 11 is
stirred in suspension in 3 mL of THF at ꢁ70 8C. 1.73 mL of n-BuLi
(1.6 M) is added slowly and the mixture is warmed up to room
temperature. After 20 mn, 561 mg I2 (2.21 mmol) is added and the

M. Baldrighi et al. / Journal of Fluorine Chemistry 131 (2010) 1218–1224
1223
solution is mixed 25 mn. Then, the reaction is hydrolysed with
4.9.2. Crystallographic data for 6
Na2S2O3 sat., the aqueous layer is extracted 3 times with CH2Cl2
and the organic phase is dried over Na2SO4. After evaporation of
the solvent, 503 mg (95% yield) of the compound 4 is recovered in
pure form without further purification.
C
24H20N4ꢀ2(C6F4I2), Mr = 1168.16, crystal size 0.24 mm
ꢃ 0.20 mm ꢃ 0.11 mm, monoclinic, space group P21/n, a =
˚
14.343(3),
b = 14.639(3),
˚
c = 18.563(4) A,
b
(Mo
= 101.68(4),
) = 3.333
max = 60.008, absorption correc-
tion based on multiscan procedure (Tmin/Tmax = 0.803),
Rave = 0.0325, 11,151 unique data, 8736 with Io > 2 (Io); refined
V = 3821.0(14) A , Z = 4, Dc = 2.031 g cmꢁ3
,
m
Ka
3
mp = 200–210 8C; 1H NMR:
d
7.44 (2H, s, CH55CH); 19F NMR:
mmꢁ1, 108,808 data collected, 2
u
d
= ꢁ141.5 (4F, m, CF–C), ꢁ122.1 (4F, m, CF–CI); m/z (EI): 526
{Mꢂ+}.
s
parameters 549, 126 restraints on atomic and thermal parameters
of H atoms, final disagreement factors for all/observed reflections
4.5. Tetrakis(4-pyridyl)cyclobutane 2
Rw(F2) = 0.0886/0.0801, R(F) = 0.0466/0ꢁ.03343, goodness-of-fit =
˚
TPCB 2 was prepared quantitatively by photocyclization of a
complex made of trans-1,2-bis(4-pyridyl)ethylene and tetrakis(4-
iodotetrafluoro-phenyl)pentaerythritol at 300 nm [15].
1.009, min/max residues ꢁ1.08/1.39 e A
.
All crystallographic data (excluding structure factors) were
deposited to the Cambridge Crystallographic Data Centre as
supplementary publication Nos. CCDC 772762 for (5) and CCDC
7727621 for (6). Copies of the data can be obtained free of charge
on application to CCDC, 2 Union Road, Cambridge CB2 1EZ, UK, e-
mail: deposit@ccdc.cam.ac.uk.
mp = 234 8C; 1H NMR:
d 4.47 (4H, s, CH), 6.99 (8H, d, J = 6.0 Hz,
H arom.), 8.44 (8H, d, J = 6.0 Hz, CH–N arom.); IR:
3024, 2904, 1595, 1551, 1412, 1137, 1068, 992, 814 cmꢁ1
nmax = 3060,
.
4.6. Formation of co-crystals 5 and 6
Acknowledgments
Co-crystals 5 and 6 were obtained by dissolving at room
temperature, in a vial of clear borosilicate glass, 1 equiv. of
tetrakis(4-pyridyl) derivative (1 and 2: 10 mg) and 2 equiv. of
fluorinated compound (3 and 4) in a mixture MeOH–CH2Cl2 for 5
and MeOH for 6. The open vial was placed in a closed cylindrical
wide-mouth bottle containing vaseline oil. The solvent was
allowed to partially diffuse at room temperature.
The financial support from Fondazione Cariplo (Project ‘‘New-
Generation Fluorinated Materials as Smart Reporter Agents in 19F
MRI’’) and MIUR (Project ‘‘Engineering of the Self-assembly of
Molecular Functional Materials via Fluorous Interactions’’) are
gratefully acknowledged.
References
4.7. Co-crystal 5: tetrakis(4-pyridyl)pentaerythritol (1)/1,2-bis-
(2,3,5,6-tetrafluoro-4-iodophenyl)-ethylene (4)
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C
25H24N4O4ꢀ2(C14H2F8I2), Mr = 1596.39, crystal size 0.24 mm
ꢃ 0.20 mm ꢃ 0.15 mm, orthorhombic, space group C2221,
3
˚
˚
a = 19.707(2), b = 20.001(2), c = 27.233(3) A, V = 10734(2) A , Z = 8,
Dc = 1.976 g cmꢁ3 ) = 2.428 mmꢁ1, 102,079 data collected,
(Mo K
max = 61.528, absorption correction based on multiscan procedure
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,
m
a
2u
Io > 2s(Io); refined parameters 731, H atoms calculated, final
disagreement factors for all/observed reflections Rw(F2) = 0.0813/
0.0753, R(F) = 0.0504/0.0341, goodness-of-fit = 1.077, min/max
ꢁ3
˚
residues ꢁ0.41/1.14 e A
.

1224
M. Baldrighi et al. / Journal of Fluorine Chemistry 131 (2010) 1218–1224
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˚
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˚
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˚
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