Assembly of benzene-1,3,5-tris(methylenephosphonic acid) and guanidinium salt: Single crystal-X-ray characterisation and 31P, solid state NMR investigations

Article abstract of DOI:10.1039/b406938b

The co-crystallisation of benzene-1,3,5 1,3,5-tris(methylenephosphonic acid) [C₉H₁₅O₉P₃] 1 with guanidinium chloride [CH₆N₃]Cl, yields compound 2 that possesses the following composition [C

Full text of DOI:10.1039/b406938b

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P A P E R
Assembly of benzene-1,3,5-tris(methylenephosphonic acid) and
31
guanidinium salt: Single crystal-X-ray characterisation and P
solid state NMR investigationsw
a
bc
Jana Sopkova-de Oliveira Santos,* Valerie Montouillout,* Franck Fayon,c Christian
´
Fernandez,b Lise Delain-Bioton,d Didier Villemind and Paul-Alain Jaffres*d
a
´
Centre d’Etude et de Recherche sur le Medicament de Normandie (CERMN), Universite de
Caen, 5 rue Vaubenard,, F-14032 Caen, France. E-mail: sopkova@pharmacie.unicaen.fr
´
´
b
c
d
´
Laboratoire Catalyse et Spectrochimie, UMR CNRS 6506, Ecole Nationale Superieure
d’Ingenieur de Caen, Universite de Caen, ENSICAEN, 6 Bd du Marechal Juin, F-14050 Caen,
France. E-mail: christian.fernandez@ismra.fr
´
´
´
´
Centre de Recherche sur les Materiaux a Haute Temperature, UPR CNRS 4212, 1D avenue
de la Recherche Scientifique, F-45071 Orleans cedex 2, France.
`
´
´
E-mail: montouillout@cnrs-orleans.fr
´
Laboratoire de Chimie Moleculaire et Thioorganique, UMR CNRS 6507, Ecole Nationale
Superieure d’Ingenieur de Caen, Universite de Caen, ENSICAEN, 6 Bd du Marechal Juin,
´
´
´
´
F-14050 Caen, France. E-mail: jaffres@ismra.fr
Received (in Montpellier, France) 10th May 2004, Accepted 11th June 2004
First published as an Advance Article on the web 16th September 2004
The co-crystallisation of benzene-1,3,5-tris(methylenephosphonic acid) [C9H15O9P3] 1 with guanidinium
chloride [CH6N3]Cl, yields compound 2 that possesses the following composition [CH6N3]3 [C9H13O9P3]
[C9H14O9P3]. The crystal structure of this supramolecular material, which possesses six crystallographically
inequivalent phosphorus atoms, is reported. The packing of this 3D-supramolecular arrangement reveals the
presence of 33 hydrogen bonds engaging the couples phosphonic acid-guanidinium and phosphonic acid-
phosphonic acid. Solid-State MAS NMR of the sensitive 31P nucleus in this supramolecular arrangement is
used in order to develop alternative analytical method to get information on supra-molecular assemblies. 31P
through-space single quantum – double quantum correlation experiments have been performed leading to
two possible assignments of the 6 crystallographic P sites to the corresponding resonances in the 1D 31P
MAS NMR spectrum.
Phosphonates and phosphonic acids that are close to phos-
Introduction
phate functions present in biological systems form attractive
building blocks that may be useful to design materials based on
hydrogen bonding. These substrates have been widely used to
form coordination materials based on the interaction with a
metal to produce metal-phosphonate hybrid bulk materials11
or immobilised materials.12 A second possibility to design
materials formed by phosphonic acids as building blocks
consists in engaging these substrates into a hydrogen bond
network. This approach which is as yet less developed than the
metal-phosphonate approach, may be achieved by the genera-
tion of hydrogen bonds between two phosphonic acid func-
tions or between phosphonic acids and another partner.
According to the first strategy, Clearfield et al. synthesised a
macrocyclic leaflet13 based on hydrogen bonding between
phosphonic acid functions. The second strategy was employed
by Schrader et al. to design spheroidal molecular assemblies
based on the interaction of a symmetrical tris-(phosphonic acid
monomethyl ester) and symmetrical tris-ammonium or tris-
amidinium compounds.14 According to molecular modelling
the authors indicate that the assemblies are based on both
hydrogen bonding and electrostatic interactions. Glidewell and
Ferguson report several crystal structures obtained by crystal-
lisation of a phosphonic acid with a diamine15 or a di-phos-
phonic acid with di-amine16 derivatives. In the first case they
report 1D, 2D or 3D structures while according to the second
approach 3D structure were obtained. In all these structures
The design of new materials based on supramolecular assem-
blies has received considerable interest due to their potential
application as NLO materials,1 magnetic materials2 or as
sensors.3 Supramolecular assemblies can be the result of weak
links (hydrogen bonds, p–p interactions, electrostatic inter-
actions. . .) between organic molecules only or on the contrary
between organic and metallic substrates.4 The knowledge of
the supramolecular interactions is also essential to understand
the kinetic or the mechanism of action of enzymes. In this field
the interaction of guanidine function (arginine, creatine. . .)
with molecules possessing a phosphate moiety (e.g.: ADP)
plays a central role in the course of reactions catalysed by
enzymes (e.g. Arginine Kinase,5 creatine kinase6). Organogels
or hydrogels chemistry is another dynamic field of research
where macroscopic properties are coming from the supramo-
lecular assembly of small molecules.7,8 Noteworthy, much of
the attention has been focused on the interaction via hydrogen
bonds of functions possessing nitrogen (amine, amide, nitrile)
and oxygenated functions9 like ketone, carboxylic acid, nitro,
amide or sulfonic acid.10
w Electronic supplementary information: tables of relevant intermole-
cular hydrogen bonding parameters, PO bond lengths and OPO angles
in crystalline complex 2. See http://www.rsc.org/suppdata/nj/b4/
b406938b/
T h i s j o u r n a l i s & T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
1244
N e w J . C h e m . , 2 0 0 4 , 2 8 , 1 2 4 4 – 1 2 4 9

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Table 1 Crystal data and details of measurements for material 2
one proton is transferred from the phosphonic acid to the
amine. Finally Clearfield et al.17 have recently reported the
synthesis of three dimensional materials based on hydrogen
bonds between a tris(phosphonic acid) and different amine or
pyridine derivatives.
The structure elucidation of a supramolecular assembly at
the solid state is usually resolved from single crystal X-ray
diffraction data. Powder diffraction has been used with success
in a few cases to describe supramolecular assembly.18 Never-
theless for complex structures this approach is not suitable so
far. In this case, high-resolution solid-state NMR can provide
complementary structural information.19,20 For example, 2D
31P through-space or through-bond homonuclear correlation
methods have been used to evidence the number of crystal-
lographically inequivalent P sites in crystalline pyrophosphate
allowing to discriminate between the possible space group
symmetries.21,22
We report herein the X-ray structure of an original supra-
molecular assembly obtained by crystallisation of tris-phos-
phonic 1 with guanidinium chloride leading to material 2. In
order to develop alternative analytical techniques to get in-
formation about the structure of supramolecular assembly
engaging phosphorus atom (phosphonic acid . . .), two-dimen-
sional 31P through-space single quantum – double quantum
(SQ–DQ) MAS NMR correlation experiment has been per-
formed. According to this experiment we report the attribution
of the resonances of the 1D 31P MAS NMR spectrum to their
crystallographic locations.
2
Formula
Molecular weight (g ꢀ molꢁ1
C42H90O36P12N18
897.48
293(2)
)
T (K)
Crystal size (mm)
System
0.7 ꢂ 0.5 ꢂ 0.2
Triclinic
ꢀ
P1
Space group
a (A)
b (A)
8.0657(5)
9.7732(7)
23.7540(10)
84.167(6)
90.429(7)
82.825(7)
1847.81(19)
1.613
c (A)
a (1)
b (1)
g (1)
Cell volume (A3)
Dx (mg mꢁ3
)
y range (1)
2 to 27
No of reflections used for cell refinement 25
Maximum indices: h, k, l
m (mmꢁ1
ꢁ10 to10, ꢁ12 to12, 0–30
)
0.378
Measured reflections
Unique reflections
8231
8033
Unique reflections with I 4 2s(I)
Rint
7386
0.0136
a
R (all data)b
0.0422
0.1233
wR2 (on F2, all data)b
(A ¼ 0.0686, B ¼ 1.8746)
Goodness of fit on F2c
1.098
664
Number of refined parameters
Max., Min. electron density/eAꢁ3
0.531, ꢁ0.438
Results and discussion
Rint ¼ S|F0 ꢁ F0 (mean)| / S[F02] R ¼ S||F0| ꢁ |Fc|| / S[F0] wR2 ¼
a
2
2
{S[w(F0 ꢁ FC2)2] / S[w(F02)2]}1/2, where w ¼ 1 / [s2(F02) þ (AP)2
þ
2
b
Synthesis and X-ray characterization
2
c
2
BP] P ¼ (F0 þ 2Fc2) / 3. S ¼ {S[w(F0 ꢁ Fc2)]/ (no. reflectionꢁtotal
Compound 1 (benzene-1,3,5-tris(methylenephosphonic acid)
[C9H15O9P3]) was synthesised by the hydrolysis of the ester
functions of the corresponding tris-phosphonate23 and its
crystal structure was previously reported.24 The co-crystallisa-
tion of compound 1 with guanidinium chloride [CH6N3]Cl
(Scheme 1) by slow evaporation of water yields compound 2
(Scheme 1) as colourless crystals of different sizes (from small
mono-crystal to a microcrystalline powder).
The elemental analysis of these crystals is in agreement with
the following composition for compound 2: [CH6N3]3
[C9H13O9P3] [C9H14O9P3]. This result indicates that chlorine
anions are excluded from the crystal in the course of the
crystallisation. Therefore the positive charges hold by the
guanidinium cations are balanced by the presence of phospho-
nic anions moieties. The DSC analysis of material 2 reveals an
exothermic transition (fusion) starting at 260 1C and with a
maximum at 288 1C. The structure of material 2 was obtained
from X-ray diffraction on single crystal (Table 1). The asym-
metric unit is composed as expected from elemental analysis,
by three guanidinium cations and two molecules 1 (Fig. 1).
no. of parameters refined)}1/2
.
Molecule 1 has a different conformation in material 2 than it
adopts when it crystallises alone.24 Indeed, in material 2, the
phosphonic functions placed in the three benzylic positions are
not located on the same side of the benzene ring (two phos-
phonic functions on one side and the third one (Phosphorus
atom P2A for molecule A and phosphorus atom P2B for
molecule B) on the other side). The positions of the hydrogen
atoms, which were determined by Fourier difference maps,
indicate that the phosphorus atoms P1A and P1B are bearing a
negative charge on the oxygen atoms O11A and O11B (Fig. 2).
According to X-ray diffraction the third negative charge, that
Fig. 1 Asymmetric unit of material 2.
Scheme 1 Synthesis of material 2.
N e w J . C h e m . , 2 0 0 4 , 2 8 , 1 2 4 4 – 1 2 4 9
1245

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Fig. 2 Molecules 1A and 1B present in material 2.
balance the three positive charges due to the guanidinium
cations, is hold by the oxygen atom O33A which is bonded
to the phosphorus P3A. The other phosphonic functions (P2A,
P2B and P3B), are neutral. It should be mentioned that two
crystallographic positions are suitable for the oxygen atoms
O12B and O13B. Two guanidinium cations are placed parallel
to the ab plane while the third guanidinium is parallel to the ac
plane.
Fig. 3 Packing of material 2.
(from 2.477 to 2.531 A; average: 2.507 A) and can be classi-
fied27 as very strong (o2.50 A) and strong hydrogen bonds
(2.50–2.65 A). This observation can be explained by the presence
of homonuclear hydrogen bonds engaging two functions posses-
sing similar electronic behaviours.28 The P–O bond length (see
supporting information-Table 4) is also in agreement with the
position of the H atoms on the phosphonic acid. Indeed the P–O
distances are around 2.50 A for a double bond, around 2.55 A
for single bond when the oxygen is bearing a hydrogen (P–OH)
and around 2.51 A for a single bond when the oxygen is
negatively charged (P–Oꢁ). Nevertheless two P–O bonds that
are connected via a hydrogen bond, have an intermediate length
(P3B–O33B–H and P3A–O33A respectively 1.529 and 1.526 A).
This hydrogen bond, characterized by a short O. . .O distance
(2.48 A), corresponds to a very strong hydrogen bond (dO. . .O
o2.50 A) that can be explained by the existence of a negative
charge assisted hydrogen bonding.29 This type of strong inter-
action is usually observed when two partners, possessing a
similar electronic repartition, are involved.
These hydrogen bonds yield a 3D structure (Fig. 3) formed
by layers (parallel to the ab plane) of dimer of molecule 1.
These dimers are connected together through hydrogen bonds
between different phosphonic acid groups and between phos-
phonic acid functions and the guanidinium cations GC and
GD, placed parallel to the ab plane. The guanidinium cation
GE and four O–H. . .O bonds link together these planes. In
view of the packing, very small tunnels, delimited by the
guanidinium cations, are formed along the a axis, but the size
of these channels are not sufficient to expect some porosity in
the material.
The study of the packing (Fig. 3) reveals a complex network
of hydrogen bonds (33 hydrogen bonds, see supporting infor-
mation-Table 3) that can be classified in two categories: (1)
hydrogen bonds between the phosphonic acid functions acting
as acceptor (A) and the guanidinium cations as donor (D); (2)
hydrogen bonds between phosphonic acid functions. The
guanidinium cations engaged 22 hydrogen bonds with the
phosphonic acid for a total of 18 hydrogen atoms borne by
the nitrogen of the guanidinium. This observation indicates
that some hydrogen atoms are engaged in bifurcated hydrogen
bonds. Indeed the hydrogen atoms H21C, H21D, H22D,
H32D and H31E are in contact with two acceptors. Note-
worthy the D. . .A length engaging the bifurcated hydrogen
bonds correspond to the longest distances (2.976 to 3.477 A)
indicating the weakness of these bonds. Another characteristic
of the hydrogen bonds between the oxygen atoms from the
phosphonic acid functions and the nitrogen atoms of the
guanidinium cations is their length. Indeed, the shortest dis-
tance D. . .A is 2.86 A for an average distance of 3.024 A. These
values, which are certainly due to the weak acidity of the
guanidinium ion (pKa¼13.5),25 are consistent with the hydro-
gen bond lengths observed when a guanidinium cation and a
phosphate are in contact.26 Furthermore the positive charge is
distributed on the three nitrogen atoms of the guanidinium ion
leading to a weak electrostatic interaction between the guani-
dinium (D) and the negatively charged oxygen atoms of the
phosphonic acid.
The second type of hydrogen bond is observed between
phosphonic functions leading to ten O. . .H–O interactions
across the structure. These bonds are stronger than the N–
H. . .O hydrogen bonds according to the d(O. . .O) distances
NMR
The 31P MAS NMR spectra (proton decoupled) of a mixture of
single crystals and microcrystals of material 2 are depicted in
1246
N e w J . C h e m . , 2 0 0 4 , 2 8 , 1 2 4 4 – 1 2 4 9

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trends between 31P isotropic chemical shift values and structure
in solids.
To provide additional constraints required for the spectral
assignment, we have used 31P double quantum homonuclear
dipolar recoupling experiment under MAS conditions. In this
experiment, the coherence transfer between coupled nuclei is
driven by the 31P–31P through-space dipolar interactions giving
rise to the observation of P–P nearest-neighbour spatial proxi-
mities in a two-dimensional (2D) single-quantum (SQ) double-
quantum (DQ) correlation spectrum. This method has already
been applied with success for resonance assignment in crystal-
line orthophosphates34 and pyrophosphates.35 Dealing with
strong heteronuclear dipolar interactions in the sample, it is
necessary to apply high power 1H heteronuclear decoupling at
the same time as double quantum homonuclear recoupling.
1
Moreover, it has been shown that the H decoupling rf-field
Fig. 4 1H decoupled 31P MAS spectra of mixture of single crystals
and microcrystal of compound 2. The decoupling sequences were (a)
continuous wave decoupling (CW) and (b) SPINAL-64 and the
decoupling power was 100 kHz.
strength should be three times the 31P rf-field strength used for
double quantum recoupling.36 In this context, we have used the
C14 double quantum recoupling37 sequence which requires
moderate 31P rf-field strength (nrf ¼ 3.5*nR) even at relatively
high spinning frequency (nR ¼ 10 to 15 kHz) allowing efficient
1H decoupling. Moreover, as our supramolecular assembly
should be considered as a multispin system, we have used
relatively short excitation and reconversion times, preventing
from relaxation effects and/or relayed transfer processes.
The result of the double quantum 31P dipolar coupling
experiment is reported in Fig. 5. The spectrum is shown as a
single-quantum – single-quantum (SQ–SQ) correlation spec-
trum obtained by a shearing transformation of the experimen-
tal SQ–DQ spectrum.38 It allows to evidence two distinct auto-
correlation peaks located on the diagonal of the 2D spectrum
which reflect the through-space proximity between two crystal-
lographically equivalent P sites. According to the internuclear
P–P distances (Table 2), these two resonances could be attrib-
uted to the P2B and P2A sites which have the shortest P–P
distances with other crystallographically equivalent sites.
Therefore two hypotheses can be formulated.
Fig. 4. Different schemes of broadband proton decoupling
have been used in order to increase the resolution of the 1D
31
P MAS NMR spectrum (high power continuous wave
irradiation CW, TPPM decoupling30 and SPINAL-64 decou-
pling31). As illustrated in Fig. 4(b), the best spectral resolution
was achieved using the new SPINAL-64 decoupling sequence.
While 5 resonances with relative intensity in the ratio 1:1:1:2:1
and individual line widths of about 140 Hz (obtained by
deconvolution32) are observed in the CW decoupled spectrum
(Fig. 4(a)), the spectrum acquired with the SPINAL decoupling
sequence exhibits 6 peaks with the same intensity and line
widths of 80 Hz. In addition, 31P proton mediated spin
diffusion MAS experiment33 (not shown) indicates that all
these resonances belong to the same phase. Therefore, these
six resolved peaks, located at 30.0, 25.2, 21.7, 20.5, 20.1 and
17.8 ppm respectively (labelled from 1 to 6 in Fig. 4(b)), are
related to the 6 crystallographically inequivalent phosphorus
sites characterized by X-ray diffraction on material 2. Never-
theless, the attribution of these resonances to the crystallo-
graphic P sites is not obvious by considering only empirical
The hypothesis 1 corresponds to the attribution of the
resonances 1 and 2 (at 30.0 and 25.2 ppm) to the phosphorus
atoms P2A and P2B, respectively. In the 2D spectrum, the
Fig. 5 1H decoupled 31P 2D through space SQ–SQ spectrum of mixture of single crystals and microcrystal of compound 2.
N e w J . C h e m . , 2 0 0 4 , 2 8 , 1 2 4 4 – 1 2 4 9
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Table 2 Through-space distances (up to 8.6 A) between the phos-
phorus atoms in materials 2
cationic charged, borne by the guanidinium moieties, are
balanced by the equivalent number of deprotonated phospho-
nic acid. Compound 2 is formed by hydrogen bonds between
phosphonic acid and guanidinium cations but also by several
hydrogen bonds between phosphonic acid functions. This
observation illustrates the ability of the phosphonic acid to
assemble to itself and to form very strong hydrogen bonds,
leading to the formation of small channels running along the a
axe. Further works, dealing with the use of more rigid tripho-
sphonic acids to design porous supramolecular assemblies
based on their interactions with guanidinium cation, are pre-
sently investigated. The characterisation of material 2 by using
31P MAS NMR is also reported. The 1D 31P MAS spectra with
SPINAL-64 proton decoupling reveals the presence of 6 dis-
tinct 31P resonances in agreement with the six inequivalent
crystallographic P sites in compound 2 according to the X-ray
structure. 2D 31P through-space single quantum – quantum
MAS NMR correlation experiment has been used to probe the
through-space connectivities between the different 31P sites. On
the basis of a qualitative analysis of the correlation peak
intensities, an attribution of the 31P resonances to the distinct
crystallographic phosphorus locations in the structure is
proposed.
P1A
P2A
P3A
P1B
P2B
P3B
P1A
P2A
P3A
P1B
8.066
4.762
4.81
4.703
6.470
7.261
7.265
5.801
8.553
7.615
7.981
8.110
5.530
7.538
4.762
4.81
4.908
5.12
8.066
4.862
6.761
6.221
6.879
7.449
4.470
5.530
7.538
4.703
6.470
7.261
7.265
4.862
6.761
6.221
6.879
8.066
6.103
7.519
5.801
6.103
7.519
8.066
4.857
5.849
7.499
4.616
6.202
7.346
7.516
P2B
P3B
8.553
4.857
5.849
7.499
5.147
8.066
4.878
6.884
6.936
Experimental
General methods
1H, 13C and 31P NMR spectra (liquid-state) were recorded on a
Bruker AC 250 spectrometer. The 31P solid-state magic angle
spinning (MAS) NMR experiments (number of scan: 4; recy-
cling delay: 60 s; pulse angle: 451) were performed at RT (it
must be noted that due to the Magic Angle Spinning, the
temperature inside the rotor is estimated to be close to 30 C)
with a spinning frequency of 10 kH, using a 2.5 mm MAS
probehead on a Bruker Avance 400 spectrometer operating at
a resonance frequency of n0 ¼ 162 MHz. The one-dimensional
31P MAS spectra were acquired using a single pulse followed
by a broadband 1H decoupling during the acquisition (1H nrf ¼
100 kHz). The two-dimensional 31P through-space single
quantum – double quantum (SQ–DQ) MAS NMR correlation
– spectrum (contact time: 1 ms; number of scan: 16; recycling
delay: 1s) was acquired using the C14 recoupling sequence37 to
achieve an efficient broadband excitation and reconversion of
double quantum coherence (nrf ¼ 35 kHz ¼3.5*nrot). Short
excitation and reconversion periods of 980 ms were used. The
excitation was preceded by a cross-polarization sequence to
reduce the experiment time, and a 1H SPINAL-64 decoupling24
was applied during all the sequence. The 31P chemical shifts
were referenced relative to 85% H3PO4 aqueous solution.
Elemental analyse was recorded on a CE Instrument NA
2500.
7.615
7.981
8.110
7.449
4.470
4.616
6.202
7.346
7.516
4.878
6.884
6.936
8.066
resonance 2 shows two main cross-correlation peaks with the
resonances 3 and 6. In addition, the correlation peak between
resonances 2 and 3 is of higher intensity. According to the
structure, the nearest neighbouring P sites of the phosphorus
atom P2B are two phosphorus atoms P1B and one phosphorus
atom P3B. Therefore, the resonances 3 and 6 are assigned to the
phosphorus sites P1B and P3B, respectively. This is also com-
patible with the observation of a cross-peak between the reso-
nances 3 (P1B) and 6 (P3B) for which the internuclear P–P
distance is 4.61 A. Similarly, the resonance 1 (P2A) exhibits two
partly overlapping cross-correlation peaks with resonances 4
and 5, the correlation between 1 and 5 being of highest intensity.
According to the X-ray structure, this leads to the attribution of
the resonances 4 and 5 to the crystallographic sites P3A and
P1A, respectively. This is supported by the observed cross-
correlation between resonances 4 (P3A) and 5 (P1A) for a P–P
distance of 4.70 A. The proposed assignment, for which the
resonances 2, 3, 6 are attributed to the 3 inequivalent P sites of
the molecule 1B and the resonances 1, 4, 5 to the molecule 1A, is
also in agreement with the remaining intense correlation peak (4
–6) and those of weaker intensities corresponding to longer
range dipolar interactions (d(P–P) 4 6 A).
Syntheses
Benzene-1,3,5-tris(methylenephosphonic acid) 1. Benzene-1,3,5-
tris(diethoxyphosphoryl-methyl)23 (5.71 g; 10.8 mmol) and
37% aqueous HCl (150 ml) was heated at reflux for 24 h.
The excess of HCl and water was removed in vacuo to afford
compound 1 as a white powder (3.58 g, 92%). Single crystals
were isolated by recrystallisation in methanol/water (7/1) with
a slow diffusion of diethylether. m.p.(DSC, 40 1C/min) ¼ 294
The second hypothesis corresponds to the attribution of the
resonances 1 and 2 to the crystallographic sites P2B and P2A,
respectively. A similar analysis based on the observed cross-
peak intensities leads to the assignment of the resonances 3, 4,
5, 6 to the sites P1A, P3B, P1B, and P3A. It should be noted
that, in this case, the resonances 2, 3, 6 are attributed to the 3
inequivalent P sites of the molecule 1A and the resonances 1, 4,
5 to the molecule 1B. Nevertheless, the presence of a cross-
correlation between the P1A and P3B sites, for which the
internuclear distance is of 7.61 A, makes this second possibility
more unlikely.
1
2
1C; H(D2O þ K2CO3): 2.90 (d, J ¼ 21.4 Hz, CH2–P), 6.89
4
(m, J ¼ 1.67 Hz, C–HAr); 31P(D2O þ K2CO3): 24.3 (s); 13C
1
(D2O þ K2CO3): 34.72 (d, JCP ¼ 129.9 Hz, CH2), 129.36 (m,
CHAr), 133.97 (m, CAr).
[C9H14O9P3]ꢁ ꢀ [C9H13O9P3]2ꢁ ꢀ [C(NH2)3]13 2. A solution of
benzene-1,3,5-tris(methylenephosphonic acid) 1 (300 mg; 0.833
mmol) in methanol/water (10 ml/5 ml) was added to a solution
of guanidinium chloride (238 mg; 2.49 mmol) in water (10 ml).
This solution was left at 18 1C for 24 h to produce a white
Conclusion
The auto-assembly of triphosphonic acid 1 with guanidinium
cation produces supramolecular materials 2 in which the
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powder (150 mg). The filtrate was left to evaporate further at
18 1C for 6 weeks, filtered and dried at room temperature to
produce complex 2 (130 mg). Suitable crystals were found for a
single crystal X-ray structure analysis (Found: C, 28.19; H,
5.26; N, 14.14. Calc. For C21H45N9O18P6:C, 28.10; H, 5.05; N,
14.05%; m.p. (DSC, 40 1C/min.), 288 1C. 31P MAS NMR (see
Fig. 4).
11 (a) A. Clearfield, Comments Inorg. Chem., 1990, 10, 89; (b) P.-A.
Jaffres, V. Caignaert and D. Villemin, Chem. Commun., 1999,
1997; (c) G. Alberti, U. Costantino, N. Allulli and J. Tomassini, J.
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Crystallography
Intensity data for compound 1 and complex 2 were collected on
an Enraf-Nonius – CAD4 diffractometer with Mo Ka radiation
(l ¼ 0.71073 A) at room temperature. The crystal structures
were solved by direct methods using SHELX97 package.39 All
non-hydrogen atoms were refined anisotropically. The posi-
tions of H atoms were determined via difference Fourier maps
and refined with isotropic atomic displacement parameters,
with exception of two hydrogen atoms of N1E (H11E, H12E) and
two hydrogen atoms of N3E (H31E, H32E) of the guanidine
cation GE which were calculated and fixed on the N-atoms in
the ideal geometry. The temperature factors of fixed H-atoms
19 E. Gaudin, F. Boucher, M. Evain and F. Taulelle, Chem. Mater.,
2000, 12, 1715.
were refined isotropically. One of the phosphonic groups (P1B
)
of one molecule (1B) in structure of complex 2 is disordered,
and the occupancy factors of disordered positions were refined.
Crystal data and data collection parameters are summarised in
Table 1. CCDC reference number 151632. See http://
www.rsc.org/suppdata/nj/b4/b406938b/ for crystallographic
data in .cif or other electronic format.
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Acknowledgements
The authors thank Dominique Massiot for discussion. We
gratefully acknowledge the ‘‘PunchOrga’’ Network (Pole Uni-
versitaire Normand de Chimie Organique), the ‘‘Ministere de
la Recherche et des Nouvelles Technologies’’, CNRS (Centre
´
National de la Recherche Scientifique), the ‘‘Region Basse-
Normandie’’ and the European Union (FEDER funding) for
financial support.
28 T. Steiner, Angew. Chem. Int. Ed., 2002, 41, 48–76.
29 P. Gilli, V. Berstolasi, V. Ferretti and G. Gilli, J. Am. Chem. Soc.,
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30 A. E. Bennett, C. M. Rienstra, M. Auger, K. V. Lakshmi and R.
G. Griffin, J. Chem. Phys., 1995, 103, 6951.
31 B. M. Fung, A. K. Khitrin and K. Ermolaev, J. Magn. Reson.,
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´
32 D. Massiot, F. Fayon, M. Capron, I. King, S. Le Calve, B.
Alonso, J.-O. Durand, B. Bujoli, Z. Gan and G. Hoatson,
Magnetic Resonance in Chemistry, 2002, 40, 70–76.
33 K. Schmidt-Rohr and H. W. Spiess, ‘‘Multidimensional Solid-State
NMR and Polymers’’, Academic Press, New York, 1994, ch3. pp.
85–98 and ch. 7, pp. 238–274.
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