Columnar mesomorphic organizations in cyclotriphosphazenes

Article abstract of DOI:10.1021/ja051042w

A synthetic strategy has been developed to prepare cyclotriphosphazenes that bear polycatenar aromatic esters as promesogenic units linked to phosphorus atoms. The microsegregation of the rigid and flexible parts of the system and the space-filling proper

Full text of DOI:10.1021/ja051042w

Published on Web 06/07/2005
Columnar Mesomorphic Organizations in
Cyclotriphosphazenes
Joaqu ´ı n Barber a´ , Manuel Bardaj ´ı , Josefina Jim e´ nez,* Antonio Laguna,‡
†
‡
,‡
‡
,†
†
‡
M. Pilar Mart ´ı nez, Luis Oriol,* Jos e´ Luis Serrano, and Irene Zaragozano
Contribution from the Polymer and Liquid Crystal GroupsDepartamento de Qu ´ı mica Org a´ nica,
and Departamento de Qu ´ı mica Inorg a´ nica, Instituto de Ciencia de Materiales de Arag o´ n,
UniVersidad de Zaragoza-C.S.I.C., 50009 Zaragoza, Spain
Received February 18, 2005; E-mail: jjimvil@unizar.es; loriol@unizar.es
Abstract: A synthetic strategy has been developed to prepare cyclotriphosphazenes that bear polycatenar
aromatic esters as promesogenic units linked to phosphorus atoms. The microsegregation of the rigid and
flexible parts of the system and the space-filling properties are the driving forces that determine the kind
of mesomorphism exhibited by the organocyclotriphosphazenes. Mesogenic units that contain only one
terminal alkyl chain give rise to calamitic mesomorphism, since the molecules are arranged to give a
cylindrical superstructure with the aromatic promesogenic cores elongated in a manner approximately
perpendicular to the cyclotriphosphazene ring. On the other hand, mesogenic units that contain three long
terminal chains exhibit columnar mesophases. In this case, a discotic structure consisting of promesogenic
cores arranged approximately parallel to the cyclotriphosphazene ring can explain the columnar organization.
h
The X-ray diffraction patterns corresponding to the Col mesophase of the cyclotriphosphazene with
dodecyloxy chains (8) indicate the presence of helical ordering, which was confirmed for a homologous
compound bearing stereogenic centers on two of the terminal chains (11). All of the synthesized
phosphazenes show a high thermal stability.
Introduction
of the skeleton from the near-infrared to about 210 to 190 nm
in the ultraviolet, high flexibility, high thermal stability, and
A great deal of scientific and technological effort has been
devoted to molecular columnar assemblies in recent years,
mainly due to their applications as electronic materials. In
particular, discotic liquid crystals are a promising type of
material, since their self-ordering facilitates the formation of
one-dimensional columnar superstructures. As a result, mo-
lecular systems with a high thermal stability, columnar meso-
morphism at temperatures close to room temperature, and a high
tendency to yield oriented monodomains are in great demand.
Phosphazenes comprise a broad class of molecules based on
the repeating unit [NPR2], including cyclic or linear oligomers
and polymers. The most striking characteristic of this type of
compound is the associated synthetic versatility, which enables
the introduction of almost any side group R on phosphorus and
allows the properties to be tailored by the choice of appropriate
low flammability of the inorganic backbone, make them of
considerable interest for both fundamental and applied materials
1
5
research.
Promesogenic units have also been attached to polyphos-
phazenes in an effort to obtain liquid crystals. However, since
the first reported example of liquid crystallinity in side-chain
2
6a,b
polyphosphazenes in 1987, only a few exploratory examples
have been described, and these incorporate calamitic prome-
sogenic units (mainly azobenzene or biphenyl groups) with only
one terminal chain, which are separated from the skeleton by a
5
a,6c
flexible spacer.
Previous works showed that specific poly-
phosphazenes, particularly those with fluoroalkoxy or simple
aryloxy side groups, are capable of an unusual mesophase-like
behavior, a phenomenon that is still not fully understood.7
3
functional groups. For example, in the case of polymers, it is
possible to design materials with special properties such as
electrical conductivity, catalytic properties, or biomedical
activity.3c,4 Other properties, such as the optical transparency
(
3) (a) Mark, J. E.; Allcock, H. R.; West, R. Inorganic Polymers; Prentice
Hall: Englewood Clifts, NJ, 1992; pp 61-141. (b) For a number of
references see also: Honeyman, C. H.; Manners, I.; Morrissey, C. T.;
Allcock, H. R. J. Am. Chem. Soc. 1995, 117, 7035. (c) Allcock, H. R.
Chemistry and Applications of Polyphosphazenes; Wiley-Interscience: New
York, 2003.
†
Departamento de Qu ´ı mica Org a´ nica.
Departamento de Qu ´ı mica Inorg a´ nica.
(
4) (a) Allcock, H. R.; Desorcie, J. L.; Riding, G. H. Polyhedron 1987, 6,
119. (b) Chandrasekhar, V.; Justin-Thomas, K. R. Appl. Organomet. Chem.
1993, 7, 1.
‡
(
1) See for instance: (a) Dimitrakopoulos, C. D.; Malenfant, P. R. L. AdV.
Mater. 2002, 14, 99. (b) Segue, I.; Jolinat, P.; Destruel, P.; Farenc, J.; Mamy,
R.; Bock, H.; Nguyen, J. I. T. P. J. Appl. Phys. 2001, 89, 5442. (c) Schmidt-
Mende, L.; Fechtenk o¨ tter, A.; M u¨ llen, K.; Moons, E.; Friend, R. H.;
Mackenzie, J. D. Science 2001, 293, 1119.
(5) (a) Allcock, H. R.; Klingenberg, E. H. Macromolecules 1995, 28, 4351,
and references therein. (b) Singler, R. E.; Willingham, R. A.; Noel, C.;
Friedrich, C.; Bosio, L.; Atkins, E. Macromolecules 1991, 24, 510.
(6) (a) Kim, C.; Allcock, H. R. Macromolecules 1987, 20, 1726. (b) Singler,
R. E.; Willingham, R. A.; Lenz, R. W.; Furukawa, A.; Finkelmann, H.
Macromolecules 1987, 20, 1727. (c) Jaglowski, A. J.; Singler, R. E.; Atkins,
E. Macromolecules 1995, 28, 1668, and references therein.
(2) Piris, J.; Debije, M. G.; Stutzmann, N.; Laursen, B. W.; Pisula, W.; Watson,
M. D.; Bjørnholm, T.; M u¨ llen, K.; Warman, J. M. AdV. Funct. Mater. 2004,
1
4, 1053.
8994
9
J. AM. CHEM. SOC. 2005, 127, 8994-9002
10.1021/ja051042w CCC: $30.25 © 2005 American Chemical Society

Mesomorphic Organizations in Cyclotriphosphazenes
A R T I C L E S
Cyclophosphazenes are also very attractive in this area
because they are excellent models for structure-reactivity
studies at a macromolecular level. Furthermore, the multiarmed
rigid ring allows the exploration of nonconventional dendritic
substitution of the chlorine atoms. However, after 2 days under
reflux, the P{ H} NMR spectrum showed incomplete substitu-
31
1
tion, with signals corresponding to the pentasubstituted com-
3
pound [N3P3Cl(OR′)5] [22.57 (t) and 7.34 (d) ppm, J(P-P) )
8
12
structures. Several liquid crystalline cyclophosphazenes have
83.1 Hz] and the hexasubstituted derivative 8. The addition
also been described and, unlike polymers, mesomorphic phases
were found even when the promesogenic unit (containing
of an excess of the alcohol to the reaction mixture and extended
heating under reflux did not yield 8 as a single compound. The
9
9a-d
9b,c
31
1
biphenyl, Schiff bases,
or azo
groups, also with only
P{ H} NMR spectrum of the crude of reaction indicated a
one terminal chain) was directly linked to the rigid cyclophos-
phazene ring. Furthermore, despite the apparent D3h symmetry
of these derivatives, they exhibit calamitic phases that are mainly
smectic in nature.
mixture of compounds with very similar phosphorus atoms (with
signals between 9 and 10 ppm), probably due to reactions
involving side groups. This mixture could not be purified by
conventional chromatographic techniques.
In this paper we report the molecular design, synthesis, and
thermal and mesomorphic properties of a series of cyclotriphos-
phazenes with polycatenar promesogenic groups. Particular
emphasis is given to the effect of the number and length of
alkyloxy terminal chains in the promesogenic units linked to
the phosphazene ring on the mesomorphic ordering. The space-
filling properties of the cyclotriphosphazene derivatives lead
to calamitic or columnar assemblies of these materials through
conformational changes.
As will be discussed below, the interesting structural features
of compound 8 encouraged us to synthesize an organocyclo-
phosphazene having nonequivalent mesogenic groups, as well
as stereogenic centers in terminal chains. With this purpose,
the synthesis of 11 was accomplished. The use of a smaller
amount of acid chloride (1.08 mol/mol of OH) in the esterifi-
cation reaction led to a mixture containing not only the
hexasubstituted derivative but also the compound with five
promesogenic groups and one 4-hydroxylphenoxy unit (10),
which was carefully purified by chromatography using a silica
gel column and hexane/ethyl acetate (20/1) as eluent. By
treatment of 10 with an excess of the corresponding acid
chloride, in the presence of NEt3 in THF, it was possible to
isolate compound 11 containing ca. 4% of 10 (as measured by
Results and Discussion
Synthesis and Structural Characterization. The reaction
sequences used for the cyclic phosphazene trimers 3-11 are
shown in Scheme 1. Hexachlorocyclotriphosphazene was reacted
with excess 4-benzyloxyphenol in the presence of Cs2CO3 in
acetone to yield trimer 1. The 4-benzyloxyphenoxy units of
trimer 1 were converted to 4-hydroxyphenoxy groups with
cyclohexene in a mixture of THF/ethanol, in the presence of
Pd(OH)2 as a catalyst, to give 2. Treatment of trimer 2 with an
excess of the corresponding acid chloride (1.3 mol/mol of OH),
in the presene of NEt3 in THF, led to trimers 3-9.
1
H NMR data), which could not be purified, even by chromato-
graphic techniques.
All cyclic phosphazene trimers (1-11) were characterized
1
31
1
13
1
by IR; H, P{ H}, and C{ H} NMR spectroscopy; mass
spectrometry (LSIMS or MALDI-TOF techniques); and mi-
croanalysis. All these data are summarized in the Experimental
Section (for 1, 2, 8, 10 and 11) and in the Supporing Information
(
for 3-7 and 9). The IR spectra of all of these compounds
The synthesis of compounds 1 and 2 has been described
previously, but this involved different, less efficient methods;
-1
13
feature peaks at around 1200 cm (br) (PdN) (due to the
31
1
phosphazene ring), and the P{ H} NMR spectra consist of a
singlet for 1-9 and an AB2 pattern for 10, with signals at similar
positions to those observed for other (phenoxy)cyclotriphos-
1
was prepared using NaOC6H4OCH2Ph-4 as the nucleophile
10
instead 4-benzyloxyphenol, and 2 was synthesized by treating
hexakis(4-methoxyphenoxy)cyclotriphosphazene with boron
14
phazenes. In the case of 11, this last spectrum also showed a
1
0a,b
tribromide
or by deprotection of benzyl ether groups in 1
single resonance, which is due to the similarity between the P
by hydrogenation under pressure in the presence of a Pd
1
13
1
environments in this compound. The H and C{ H} NMR
spectra are also consistent with the formulas indicated. For
example, in addition to signals for the protons in the aromatic
catalyst.1
0c
It is worth pointing out that the commonly used method of
nucleophilic substitution of aryl oxides on the cyclic halophos-
phazene trimer11 did not give the target compounds. The reaction
of hexachlorocyclotriphosphazene [N3P3Cl6] with the alcohol
R′OH [OR′ ) OC6H4{OC(O)C6H2(3,4,5-OC12H25)3}-4] in a 1:6
molar ratio in the presence of Cs2CO3 in acetone gave
1
ring (OC6H4O, AA′BB′ spin system), the H NMR spectrum
of 1 contains resonances for benzyloxy protons at 4.97 (s, OCH2)
and 7.39-7.30 (m, C6H5) ppm. These signals were replaced by
a signal at 8.33 (s) due to OH protons after conversion to 2.
1
The H NMR spectra of trimers 3-11 also showed resonances
corresponding to the other aromatic protons and the protons of
the terminal alkyl chains. In the case of 10, the signal
(
7) (a) Allen, G.; Lewis, J.; Todd, S. M. Polymer 1970, 11, 14. (b) Singler, R.
E.; Schneider, N. S.; Hagnauer, G. L. Polym. Eng. Sci. 1975, 15, 321. (c)
Kojima, M.; Magill, J. H. Makromol. Chem. 1985, 189, 649. (d) Wuderlich,
B.; Grebowicz, J. AdV. Polym. Sci. 1984, 60/61, 1.
(11) (a) Carriedo, G. A.; Fern a´ ndez-Catuxo, L.; Garc ´ı a-Alonso, F. J.; G o´ mez-
Elipe, P.; Gonz a´ lez, P. A.; S a´ nchez, G. J. Appl. Polym. Sci. 1996, 59, 1879.
(b) Carriedo, G. A.; Fern a´ ndez-Catuxo, L.; Garc ´ı a-Alonso, F. J.; G o´ mez-
Elipe, P.; Gonz a´ lez, P. A. Macromolecules 1996, 29, 5320. (c) Allcock,
H. R. Phosphorus-Nitrogen Compounds; Academic Press: New York,
1972; Chapters 6 and 7. (d) Allen, C. W. Chem. ReV. 1991, 91, 119. (e)
De Jaeger, R.; Gleria, M. Prog. Polym. Sci. 1998, 23, 179.
(
8) Majoral, J. P.; Caminade, A. M. Chem. ReV. 1999, 99, 845, and references
therein.
(
9) (a) Moriya, K.; Suzuki, T.; Kawanishi, Y.; Masuda, T.; Mizusaki, H.;
Nakagawa, S.; Ikematsu, H.; Mizuno, K.; Yano, S.; Kajiwara, M. Appl.
Organomet. Chem. 1998, 12, 771, and references therein. (b) Moriya, K.;
Suzuki, T.; Yano, S.; Kajiwara, M. Liq. Cryst. 1995, 19, 711. (c) Moriya,
K.; Suzuki, T.; Yano, S.; Kajiwara, M. Trans. Mater. Res. Soc. Jpn. 1999,
(12) The assignment of the signals in this spectrum to the different phosphorus
atoms was made taking into account its multiplicity and its chemical shifts,
which appear in similar positions to those observed in other similar
aryloxycyclotriphosphazenes. See, for instance: Allcock, H. R.; Laredo,
W. R.; deDenus, C. R.; Taylor, J. P. Macromolecules 1999, 32, 7719.
(13) Allcock, H. R. J. Am. Chem. Soc. 1964, 86, 2591.
2
4, 481. (d) Moriya, K.; Kawanishi, Y.; Yano, S.; Kajiwara, M. Chem.
Commun. 2000, 1111. (e) Moriya, K.; Ikematsu, H.; Nakagawa, S.; Yano,
S.; Negita, K. Jpn. J. Appl. Phys. 2001, 40, L340.
(
10) (a) Medici, A.; Fantin, G.; Pedrini, P.; Gleria, M.; Minto, F. Macromolecules
1
992, 25, 2569. (b) Allcock, H. R.; Cameron, C. G. Macromolecules 1994,
2
7, 3125. (c) Allcock, H. R.; Al-Shali, S.; Ngo, D. C.; Visscher, K. B.;
(14) Allcock, H. R.; Connolly, M. S.; Sisko, J. T.; Al-Shali, S. Macromolecules
1988, 21, 323.
Parvez, M. J. Chem. Soc., Dalton Trans. 1996, 3549.
J. AM. CHEM. SOC.
9
VOL. 127, NO. 25, 2005 8995

A R T I C L E S
Scheme 1
Barber a´ et al.
corresponding to the OH proton was observed at 6.1 ppm. This
last spectrum, along with that of 11, was more complicated as
a result of the nonequivalence of all the promesogenic groups.
Thermal and Mesomorphic Properties. The thermal and
mesomorphic properties of the organocyclotriphosphazenes were
studied by thermogravimetry (TGA), differential scanning
calorimetry (DSC), polarizing optical microscopy (POM), and
X-ray diffraction. The results are summarized in Table 1.
The polycatenar organocyclotriphosphazenes generally exhibit
a high thermal stability according to thermogravimetric analysis,
which shows a single, rapid decomposition at above 300 °C.
The study of the mesomorphic properties revealed liquid
crystalline behavior that depended on the number and length
of terminal chains. For example, compound 3, which has
promesogenic units with one terminal chain, displays an
enantiotropic nematic phase. The calamitic nature of this
compound is explained in terms of the model previously
proposed by Moriya and co-workers. In such a system, the
mesogenic side groups are arranged approximately perpendicular
to the cyclotriphosphazene ring, forming parallel triplets pointing
upward and downward to give a calamitic superstructure capable
of being organized in a nematic phase (see Figure 1).
1
5
However, when mesogenic units with a greater number of
terminal chains are introduced, the organocyclotriphosphazenes
(
15) (a) Levelut, A. M.; Moriya, K. Liq. Cryst. 1996, 20, 119. (b) Moriya, K.;
Suzuki, T.; Yano, S.; Miyajima, S. J. Phys. Chem. B 2001, 105, 7920.
8996 J. AM. CHEM. SOC.
9
VOL. 127, NO. 25, 2005

Mesomorphic Organizations in Cyclotriphosphazenes
A R T I C L E S
Table 1. Thermal and Mesomorphic Properties of the
Cyclotriphosphazenes
The incorporation of three terminal chains in each of the
mesogenic cores (compounds 5-9) eventually stabilizes the
columnar mesomorphism. Compound 5 was synthesized in order
to explore the possibility of obtaining monocrystals for X-ray
measurements. However, this compound is an amorphous
material that only exhibits a glass transition in both the first
and second DSC scans. The presence of longer alkyl chains
results in mesomorphism, but the thermal behavior depends on
the length of these terminal chains. Compound 6 is a waxy
material at room temperature and can be plastically deformed
by mechanical stress. The study of 6 by POM did not show a
well-defined birefringent texture, and the material became
isotropic at above 70 °C. On cooling this compound (10 °C/
min), an isotropic (I)-mesophase (M) transition occurred at
around 35 °C and this was characterized by an ill-defined
pseudo-fan-shaped texture with some dark regions, which is
consistent with a columnar mesophase (Figure 2a). The texture
was retained at room temperature. On the DSC traces only a
peak was observed, both on heating and cooling processes.
However, the enthalpy change corresponding to the endothermic
peak detected at 67 °C in the heating scan (26.4) and to the
exothermic peak detected at 34 °C on cooling (11.2) differs
significantly. These findings are reproducible and point to partial
crystallization of the sample, despite the fact that an exothermic
crystallization peak was not clearly detected in the DSC curves
or by optical microscopy.
a
a
thermal transitionsb
(∆H, kJ/mol)
compd
2%a
T
onset
T
max
3
4
5
6
7
8
9
364
313
338
303
361
263
361
150
260
393
387
403
381
384
388
395
387
360
407
399
411
387
400
400
406
396
378
K 125 (60.0) N 129 (1.6) I
K [61 (8.6) Col] 88 (81.0) I
c
g 75 I
K, Colr 67 (26.4) I
d
K 38 (16.4) Colh 67 (7.9) I
K 2 (68.0) Colh 59 (7.8) I
K 32 (162.7) Colh 65 (9.7) I
Colh 54 (4.9) I
1
1
0
1
Colh 54 (7.6) I
a
Temperatures are in °C. 2% weight loss corresponds to the temperature
that brings about 2% weight loss, Tonset corresponds to the onset of the
decomposition detected on the weight loss curve, and Tmax was read at the
maximum of the derivative thermogravimetric curve (10 °C/min, under
b
nitrogen atmosphere). Temperature in °C detected by DSC and read at
the maximum of the peak of the second scan (10 °C/min). ∆H values in
kJ/mol are in parentheses. The nature of the mesophase was characterized
c
d
by POM and X-ray diffraction. Monotropic transition. See the text for
explanation.
Cyclophosphazene 7 is a waxy compound that is susceptible
to plastic deformation at room temperature. On heating the
sample, the viscosity decreased and a mesophase was clearly
observed. Finally, isotropization was detected at around 65 °C.
On cooling of the sample from the isotropic state, the transition
I-M was detected at a similar temperature, and well-defined
textures were observed. The pseudo-focal-conic fan-shaped
texture along with a homeotropic one exhibited by this
compound at 60 °C is shown in Figure 2b. Both textures are
compatible with a Colh phase. On subsequent cooling, the texture
observed by POM remained unchanged and the material
appeared to be liquid crystalline at room temperature. However,
the DSC study of this compound also reveals a phase transition
at around 40 °C, both on heating and cooling cycles, and this
transition has a relatively low ∆H. Compound 8, which has
dodecyloxy terminal chains, was clearly mesomorphic at room
temperature. The phase became isotropic at around 60 °C. This
material diplays similar textures to compound 7 but has a high
tendency to orient homeotropically between glass substrates
without any treatment. In fact, homeotropic monodomains can
be obtained by slow cooling (<2 °C/min). The DSC traces show
evidence of a transition at around 0 °C, which is most probably
due to crystallization of the compound, according to the high
enthalpy observed for this transition. However, only slight
Figure 1. Nematic ordering 3 according to the model proposed by Moriya
and co-workers.
tend to assemble in a columnar organization. Compound 4
contains mesogenic cores with two decyloxy terminal chains
and is a crystalline material that melts at 88 °C to give a
monotropic mesophase on cooling from the isotropic phase.
However, this compound immediately crystallized, thus prevent-
ing the development of a well-defined texture. Nevertheless, a
grainy texture with mosaic-like regions was observed, which
became homeotropic under mechanical stress. On this basis, the
mesophase has been tentatively assigned as columnar. The
monotropic nature of this mesophase precluded an X-ray
diffraction study as crystallization occurred during exposure to
X-rays.
Figure 2. Microphotographs of compounds (cooled from the I phase at 10 °C/min): (a) 6 taken at 30 °C; (b) 7 taken at 60 °C; (c) 11 taken at 30 °C.
J. AM. CHEM. SOC. VOL. 127, NO. 25, 2005 8997
9

A R T I C L E S
Barber a´ et al.
modifications of the mesomorphic texture were observed by
POM study down to -20 °C (see Supporting Information).
Compound 9, having the longest terminal alkyl chains, is a
crystalline material at room temperature that melts into a
columnar mesophase at 32 °C and finally becomes isotropic at
around 65 °C. DSC and POM measurements of this compound
put in evidence the tendency of this material to crystallize (with
a high enthalpic change).
Finally, POM and DSC measurements of compounds 10
(synthetic precursor of 11) and 11 indicated that both exhibit a
similar thermal behavior to the homologous compound 8: a
Colh mesophase at room temperature that becomes isotropic at
approximately 54 °C. A typical texture observed for compound
Figure 3. X-ray diffraction pattern of the Colh mesophase of 7 taken at
48 °C.
1
1 is shown in Figure 2c. However, in contrast to compound 8,
Table 2. X-ray Diffraction Data for the Columnar Mesophases of
Cyclophosphazenes
evidence of crystallization was not detected on cooling from
the isotropic phase on the DSC study.
wave
vector constants
q (Å-1)
(Å)
lattice
T
S
S
0
R
Structural Characterization. In an effort to gain more
information on the different phases, X-ray measurements were
performed on samples of the columnar materials at different
temperatures. First, diffraction experiments were performed at
room temperature both in the virgin state and in samples cooled
from the isotropic liquid. The diffraction patterns of virgin
samples of 6, 7, and 9 indicate (at least partially) a crystalline
structure, as revealed by the presence of a large number of sharp
reflections over the whole angular range. Similar patterns were
obtained from samples that had been heated to the isotropic
liquid and then slowly cooled to room temperature. The above-
mentioned softness observed for 6 probably arises from the
persistence of some proportion of mesomorphic phase even at
room temperature. In fact, crystallization on 6 can be avoided
by a quick cooling from mesophase to room temperature (see
below). However, the X-ray pattern of 7 at room temperature
indicates that this phase must be crystalline in nature, as the
crystallization could not be avoided and the DSC peak corre-
sponding to this transition is reproducible regardless of the
cooling rate. The softness of this phase at room temperature (it
exhibits plastic deformation) suggests that the crystalline
structure contains a large degree of disorder. This situation is
supported by the presence in the X-ray patterns of a diffuse
halo at about 4.5 Å, which is characteristic of the liquidlike
arrangement of the chains (see Supporting Information). Finally,
the X-ray diffraction patterns taken at room temperature for 9,
which contain a high number of sharp reflections in the whole
angular range, also confirm the crystalline nature of this
cyclophosphazene.
compd
(
°
C) phase
d
hk (Å)b
(Å2)c (Å2)d (Å)e
6a rt Colr d11 ) 28.3 (28.1)
d31 ) 17.3 (17.3)
0.224 a ) 62 976.5 426 11.6
0.363 b ) 31.5
d
2
2
) 13.8 (14.0)
0.449
0.546
d51 ) 12.0 (11.5)
d60, d13 ) 10.2 (10.3) 0.610
48 Colh d10 ) 32.5
rt Colh d10 ) 35.0
40 Colh d10 ) 36.9
rt Colh d10 ) 35.3
rt Colh d10 ) 36.4
7
8
9
0
1
0.193 a ) 37.5 1219 405 11.4
0.180 a ) 40.4 1414 419 11.5
0.170 a ) 42.6 1572 421 11.6
0.178 a ) 40.7 1433 457 12.1
0.173 a ) 42.0 1529 483 12.4
1
1
a
b
Sample quickly cooled from mesophase to room temperature. Cal-
c
d
culated spacings are in parentheses. Column cross section. Core cross
section. e Core radius.
Figure 4. (a) X-ray pattern of the rectangular columnar mesophase of
compound 6 taken at room temperature; (b) small-angle region.
due to short-range correlations between the conformationally
disordered hydrocarbon chains and confirms the liquid-crystal-
line character of the mesophases.
In contrast to this, when compound 8 was studied by X-ray
diffraction at room temperature, both on virgin samples and
samples cooled from the isotropic liquid, in all cases the patterns
were consistent with a hexagonal columnar mesophase. The
same type of pattern was found for the high-temperature phase
of 7 and 9 and confirms that these compounds exhibit a Colh
mesophase (see Figure 3). The measured hexagonal lattice
constant a is deduced from the d10 reflection observed in the
patterns and calculated as a ) (2/x3)d10. The cross-sectional
area of a column (surface of the unit cell) is calculated as ad10.
All these values are gathered in Table 2. As expected, an
increase in the lattice constant a and in the column cross-
sectional area is observed upon increasing the chain length. In
the high-angle region of the patterns, there is only a diffuse
halo corresponding to a distance of about 4.5 Å. This halo is
In the case of compound 6, with the aim of obtaining the
pure liquid crystal phase and precluding crystallization, a sample
of the compound was heated to the isotropic liquid, slowly
cooled to the mesophase transition temperature and then quickly
cooled to room temperature. This procedure caused the me-
sophase to freeze for a sufficient period of time for study by
X-ray diffraction prior to the onset of crystallization (Figure
4). This situation was confirmed by the absence of sharp
reflections at high angles and the presence in this region of only
the diffuse halo corresponding to a distance of about 4.4 Å,
which is typical in disklike liquid crystals. Although long-
exposure patterns could not be registered, due to the tendency
of the compound to slowly crystallize, the X-ray photographs
clearly indicate that the liquid crystal phase is of a columnar
8998 J. AM. CHEM. SOC.
9
VOL. 127, NO. 25, 2005

Mesomorphic Organizations in Cyclotriphosphazenes
A R T I C L E S
Figure 5. X-ray pattern of an aligned sample in the Colh mesophase: (a) compound 8 taken at room temperature; (b) compound 9 taken at 40 °C; (c)
compound 11 taken at room temperature. The capillary axis is vertical. Diffuse spots in the first layer line are indicated with an arrow.
nonhexagonal type. The structure is most probably rectangular
columnar, and the proposed lattice constants, as deduced from
the observed reflections, are gathered in Table 2. Assuming that
there are two columns per unit cell, the cross-sectional area of
each column is calculated as ab/2. This value appears consistent
with those calculated for the columnar cross section of the rest
of the compounds taking into account the differences in chain
length.16 Identical X-ray results were obtained within the
experimental error when the sample was investigated at higher
temperatures (52 and 60 °C).
Very interesting structural information is given by the X-ray
patterns taken on aligned samples of compound 8, which were
obtained by mechanical alignment of the sample in the capillary
tube. The resulting X-ray patterns contain a pair of low-angle
strong arcs centered on the equator (direction perpendicular to
the capillary axis)sthese correspond to the d10 reflectionsand
a nearly isotropic diffuse halo at 4.5 Å (Figure 5a). A pattern
such as this means that the mesophase is oriented with the
column axes in the direction of the capillary axis (stretching
direction), as it is usual in columnar mesophases, and the
aliphatic chains remain disordered. The presence of only a
maximum at low angles is not inconsistent with a hexagonal
columnar mesophase.17 In addition, several middle-angle diffuse
spots are apparent, and these are not common in classical
discotic liquid crystals. A diffuse spot is observed in the
direction of the meridian (direction of the capillary axis) and
this corresponds to a distance of about 15.5 Å. The presence of
this scattering suggests some kind of modulation of the
electronic density along the column axis. Moreover, a diffuse
scattering maximum, split into four spots, is situated sym-
metrically with respect to the equator and the meridian. These
spots correspond to a modulation of the electronic density with
a period of about 28.5 Å in the direction of the column axes.
The fact that these spots are off the meridian is probably
18
consistent with some kind of helical order. This feature is more
clearly visible for compound 11 and will be discussed below.
The diffuse spot at 15.5 Å centered on the meridian could be
consistent with a structure in which the columns are “broken”
into blocks of stacked molecules. A reasonable value for the
mesophase density is obtained if we assume that each of these
-3
blocks contains three molecules (estimated density 1.08 g cm ).
These defects in the columnar packing would be related to the
peculiar geometry of the molecules, which have a 3-fold axis
perpendicular to the cyclophosphazene ring that leads to a
molecule with a star shape. The stacking of this kind of molecule
would generate an empty space between the arms of the “star”,
and this mismatch can be compensated if two neighboring blocks
are rotated with respect to each other. The fact that 28.5 Å is
almost twice 15.5 Å suggests that the blocks are rotated by 60°
with respect to each other. In this way the arms of each block
would be able to locate themselves between the arms of the
neighboring block, thus giving more efficient space filling. It
is not clear why 15.5 Å thick blocks of three molecules act as
units before making the 60° turn around the column axis. At
first sight, for best space filling a turn would be expected to
occur after each individual molecule, giving an alternating
structure. The reason for the actual behavior may be that the
benzoyloxyphenyl groups have tendency to stack parallel to each
other, and the eclipsed stacking is left out every three mole-
cules after being forced to rotate by the increasing overcrowding
of the rigid arms and alkoxy chains. However, it should be borne
in mind that the diffuseness of the maxima under discussion
indicates that the described distribution in blocks and the
alternating twist structure only extend over short distances.
Similarly to compound 8, oriented patterns of the mesophases
of 7 and 9 (as well as 10) could be obtained by mechanical
alignment of the samples. The resulting X-ray patterns contain
a pair of low-angle strong arcs centered on the equator, which
correspond to the d10 reflection, and a nearly-isotropic diffuse
halo at 4.5 Å (Figure 5b). However, in contrast to compound
(
16) Estimations of packing density led to reasonable values if we consider two
columns per unit cell. The relationship between the density (F) of the
compounds and the number (Z) of molecules in the unit cell is given by
the following equation: F ) (M/N)/(V/Z), where M is the molar mass (g)
3
(
3217 g for 6), N the Avogadro number, and V the unit cell volume (cm ).
3
-24
V (in cm ) is calculated by the formula V ) abc x 10 for a rectangular
lattice, where a, b, c are the lattice constants in Å. Considering a density
equal to 1 g cm- , this means that in the proposed rectangular columnar
structure the average stacking distance (c constant) would be 4.5 Å for Z
8
, no other features are observed in these diffractograms, and
3
this means that there is no evidence of helical order in the
mesophases of these compounds.
In an attempt to favor the helical order suggested for
compound 8, the synthesis of compound 11, containing two
)
2. This distance is reasonable compared to those found in other columnar
mesophases and are in agreement with the diffuse halo observed in the
X-ray patterns.
(
17) (a) Kohne, B.; Praefcke, K.; Stephan, W. Chimia 1986, 40, 14. (b)
Strzelecka, H.; Jallabert, C.; Veber, M.; Davidson, P.; Levelut, A. M. Mol.
Cryst. Liq. Cryst. 1988, 161, 395. (c) Malth eˆ te, J.; Levelut, A. M. AdV.
Mater. 1991, 3, 602. (d) Zheng, H.; Xu, B.; Swager, T. M. Chem. Mater.
(18) (a) Levelut, A. M.; Oswald, P.; Ghanem, A.; Malth eˆ te, J. J. Phys. 1984,
745. (b) Livolant, F.; Levelut, A. M.; Doucet, J.; Benoit, J. P. Nature 1989,
339, 724. (c) Barber a´ , J.; Cavero, E.; Lehmann, M.; Serrano, J. L.; Sierra,
T.; V a´ zquez, J. T. J. Am. Chem. Soc. 2003, 125, 4527.
1
996, 8, 907. (e) Barber a´ , J.; Gim e´ nez, R.; Serrano, J. L. Chem. Mater.
000, 12, 481.
2
J. AM. CHEM. SOC.
9
VOL. 127, NO. 25, 2005 8999

A R T I C L E S
Barber a´ et al.
Figure 6. Schematic model for the helical columnar assembly of cyclotriphosphazene 11. Four molecules rotated by 90° are needed to complete a full turn
chiral terminal chains are indicated with asterisks).
(
stereogenic centers, was carried out. In a first approach, the
incorporation of a promesogenic unit with branched terminal
chains having two stereogenic centers may hinder regular
stacking of the organocyclotriphosphazenes and could conse-
quently favor helical ordering. The X-ray patterns taken on
compound 11, as well as on its precursor 10, confirm that the
mesophase of these compounds is columnar hexagonal (Table
The model proposed by Moriya et al. to explain the calamitic
mesomorphism in cyclotriphosphazenes with a terminal chain
does not account for the columnar mesomorphism exhibited by
these columnar cyclotriphosphazenes. When the number of
terminal chains increases, there is a significant change in the
relationship between the volumes of the hard part (cyclotri-
phosphazene ring and mesogenic cores) and the soft part
(aliphatic terminal chains) of these multiarmed dendritic mol-
ecules. The segregation of the two parts of the molecule and
the space-filling properties create a tendency for the molecules
to adopt a discotic structure, which allows a higher degree of
interaction between the neighboring molecules and explains the
cross-sectional area of columns measured by X-ray diffraction.
In this discotic structure, the aromatic promesogenic cores tend
to arrange themselves in two levels: three promesogenic units
are located in a plane above the phosphazene ring (upper level)
and the other three in a plane below (lower level) as a
consequence of the orientation of the P-O bonds. This situation
gives rise to a supramolecular organization that is reminiscent
of two three-arm star-shaped compounds forced to pack in
columns. Figure 6 displays the columnar organization of
compound 11 according to this model and the X-ray data. The
aliphatic chains surround the rigid central core and allow
efficient packing of the molecules. Estimations about the radius
of the columnar core, i.e., the inner part of the columns, which
includes the cyclotriphosphazene ring and the benzoyloxyphenyl
units, are listed in Table 2. On the basis of the percentage
contribution of the central core to the molar mass and assuming
that the density is similar in the central core and in the aliphatic
chains, we calculate the fraction of the column cross section
2
). The measured d10 spacing and hence the hexagonal lattice
constant a are slightly larger for 11 than those for 8, despite
the fact that the number of aliphatic carbonssand hence the
molecular masssis smaller in 11. This suggests that the
molecular conformation adopted by each compound is different
and therefore the packing is also different. X-ray patterns of
aligned samples of 11 show certain peculiar features (Figure
5
c). Apart from the small-angle d10 reflection centered on the
equator and the almost isotropic large-angle diffuse halo, the
diffraction patterns contain a set of diffuse spots located on
equally spaced layer lines parallel to the equator. The innermost
maxima on the first and second layers lie approximately on
straight lines radiating from the origin, producing a cross-like
pattern. These features are consistent with a helical structure
with the axis of the helix parallel to the columns (meridian
1
9
18
direction), as it has been described for other chiral compounds.
The helical pitch, deduced from the spacing between the layer
lines, is 18.4 Å. The number of molecules per helical turn can
be deduced from the pattern, bearing in mind that on the fourth
layer line (located at 4.60 Å) there is a strong scattering
maximum centered on the meridian. This indicates that there
are exactly four molecules per turn of the helix, and these are
separated on average by a stacking distance of 4.60 Å. The
-3
0 0
corresponding to the central core (S ). From S the core radii R
density calculated for this structure is 1.04 g cm . The existence
of a hexagonal columnar mesophase with a helical organization
in this compound can be described as follows: the molecules
stack with their main planes parallel to each other, and they
rotate around the column axis in such a way that two neighbor-
ing molecules are mutually rotated by an angle of π/2 (360°/
are deduced and compared with the theoretical radius of the
core. Using Dreiding stereomodels and ChemBats3D software,
this theoretical radius is estimated to be about 13 Å. As the R
values shown in Table 2 are smaller (especially in the case of
compounds 6-9), it is deduced that the rigid branches are tilted
with respect to the lattice plane, i.e., the plane perpendicular to
the column axis. These dendritic molecules show mesomorphic
behavior resembling that exhibited by mesomorphic calamitic
4
). Therefore, four molecules of compound 11 are needed to
complete a full turn, the helical pitch being 4.6 × 4 ) 18.4 Å.
It is noteworthy that the helical order for this compound extends
for longer distances than in the case of compound 8. This fact
is deduced from the above-mentioned presence of several layer
lines of spots and by the higher intensity of these spots.
(
19) (a) Lehmann, M.; Gearba, R. I.; Koch, M. H. J.; Ivanov, D. A. Chem.
Mater. 2004, 16, 374. (b) Ryu, S. Y.; Kim, S.; Seo, J.; Kim, Y. W.; Kwon,
O. H.; Jang, D. J.; Park, S. Y. Chem. Commun. 2004, 70.
9000 J. AM. CHEM. SOC.
9
VOL. 127, NO. 25, 2005

Mesomorphic Organizations in Cyclotriphosphazenes
A R T I C L E S
or columnar materials derived from the flexible DAB or
PAMAM dendrimers,20 despite the fact that these cyclophos-
phazenes have a rigid core. However, both calamitic and discotic
models are compatible in these compounds as a consequence
of the different conformations adopted by the molecules
Synthesis of [N
3 3 6 4 2 6 3 3
P (OC H OCH Ph-4) ] (1). A mixture of [N P -
Cl ] (0.348 g, 1 mmol), 4-benzyloxyphenol (1.321 g, 6.6 mmol), and
6
2 3
Cs CO (4.88 g, 15 mmol) in acetone (50 mL) was heated under reflux
and stirred for 15 h. The volatile materials were evaporated under
vacuum, and the residue was extracted with dichloromethane (3 × 10
mL). Evaporation of the solvent to ca. 1 mL and addition of hexane
led to the precipitation of 1 as a white solid. Yield: 1.105 g, 83%.
(conformational freedom on the P-O-C bonds) in an effort to
optimize space filling.
Anal. Calcd (%) for C78
66 3 12 3
H N O P (1330.32): C, 70.42; H, 5.0; N,
3
1
.16. Found: C, 70.74; H, 4.71; N, 3.26. IR (Nujol): 1193 (s, br),
Conclusions
-1
31
1
175 (s, br) (PdN); 952 cm (s) (P-O). P{ H} NMR (CDCl
3
):
): δ ) 7.39-7.30 (m,
6 4
H O), 6.76 (“d”, J ) 9 Hz,
1
δ ) 10.05 (s, 3P; N
P
3 3
ring). H NMR (CDCl
3
The synthesis of a series of organocyclotriphosphazenes has
been successfully achieved by esterification of the corresponding
5
2
1
H; C
H; OC
6
H
5
), 6.85 (“d”, J ) 9 Hz, 2H; OC
H O), 4.97 (s, 2H; OCH ). C{ H} NMR (CDCl ): δ )
4 2 3
13
1
6
4-hydroxyphenoxy derivatives. The mesomorphic properties of
55.98, 144.74, 137.05, 128.72, 128.10, 127.58, 122.06, 115.56 (12C;
the cyclotriphosphazenes strongly depend on the number of
terminal alkyl chains. Incorporation of the mesogenic unit with
one terminal chain gives rise to calamitic mesomorphism, which
is explained in terms of a cylindrical superstructure. However,
the presence of a larger number of terminal chains causes the
molecule to adopt a discotic structure in order to optimize the
space-filling properties and the interactions of soft and rigid
parts of the molecules. Evidence of helicity in the columnar
mesophase of compound 8 has been detected by X-ray diffrac-
tion. The incorporation of stereogenic centers in the alkyl chains
allowed confirmation of the helical columnar ordering in the
mesophase by X-ray diffraction measurements of aligned
samples. The great synthetic versatility of cyclotriphosphazenes,
+
aromatic carbons); 70.66 (1C; OCH
2
). MS (LSIMS ) m/z (%): 1330
+
(100) [M ] and peaks derived from the sequential loss of OCH
2
Ph,
C H OCH Ph, and OC H OCH Ph.
6
4
2
6
4
2
Synthesis of [N P (OC H OH-4) ] (2). To a solution of [N P (OC H -
3
3
6
4
6
3
3
6
4
2 6
OCH Ph-4) ] (1) (1.33 g, 1 mmol) in dry THF (10 mL) were added
cyclohexene (6 mL), palladium hydroxide (20 wt % on carbon, 0.4 g),
and ethanol (6 mL). The mixture was heated under reflux for 6 h and
filtered. The solvent was evaporated and subsequent addition of
dichloromethane (20 mL) led to the precipitation of the product as a
white solid. Yield: 0.734 g, 93%.
Anal. Calcd (%) for C36
30 3 12 3
H N O P (789.57): C, 54.76; H, 3.83; N,
5
3
.32. Found: C, 54.36; H, 3.72; N, 5.61. IR (Nujol): 3274 (m, br),
-
1
203 (m, br) (O-H); 1187 (s), 1175 (s, br) (PdN); 950 cm (s) (P-
31
1
1
O). P{ H} NMR [(CD
(CD CO]: δ ) 8.33 (s, 1H; OC
OH).13C{
(6C; OC
derived from the sequential loss of OC
Synthesis of [N (OC {OC(O)C
3 2
)
3 3
CO]: δ ) 11.62 (s, 3P; N P ring). H NMR
2
1
as templates for the design of supermolecular liquid crystals,
[
3
)
2
6
H
4
6 4
OH), 6.72 (s, 4H; OC H -
opens up new possibilities for the preparation of novel dendritic
columnar assemblies at room temperature for optical and
electronic applications.
1
H} NMR [(CD ) CO]: δ ) 155.35, 144.57, 122.72, 116.66
O). MS (LSIMS ) m/z (%): 790 (100) [M ] and peaks
3
2
+
+
6
H
4
6 4
H OH.
3
P
3
6
H
4
6
H
2
(3-R
2
,4-R
1
,5-R
3
)-4})
6
]
Experimental Section
[R ) n-OC H , R ) R ) H (3); R ) R ) n-OC H , R ) H
1
10 21
2
3
1
2
10 21
3
(
R
R
4); R
1
) R
) R
) R
2
) R
) n-OC10
) n-OC14
3
) n-OCH
3
(5); R
1
) R
) R
2
) R
) R
3
) n-OC
) n-OC12
6
H
13 (6);
General Data. Instrumentation and general experimental techniques
1
) R
2
3
H
21 (7); R
1
2
3
H
25 (8);
(
elemental analysis, IR, NMR, thermogravimetry, and optical micros-
1
) R
2
3
H
29 (9)]. These compounds were prepared in
22
copy) were as described earlier. MALDI-TOF mass spectrometry was
carried out on a REFLEX III Bruker instrument using dithranol as
matrix. DSC was performed using a DSC 2910 from TA Instruments
with samples (2-5 mg) sealed in aluminum pans and a scanning rate
of 10 °C/min under a nitrogen atmosphere. In general, the peaks
obtained were broad and the transition temperatures were therefore read
at the maximum of the peaks. The X-ray diffraction patterns were
obtained with a pinhole camera (Anton-Paar) operating with a point-
focused Ni-filtered Cu KR beam. The samples were held in Lindemann
glass capillary tubes (1 mm diameter) and heated, when necessary, with
a variable-temperature oven. The patterns were collected on flat
photographic films. The capillary axis and the film were perpendicular
to the X-ray beam. Spacings were obtained using Bragg’s law. Aligned
samples were achieved by scratching the inner wall of the capillary in
the direction of its axis with a metal rod at a temperature at which the
mesophase is sufficiently fluid.
a similar manner. The following procedure is typical (see Supporting
Information for details of the rest of compounds). A mixture of
[
N
3
P
3
(OC
6
H
4
OH-4)
(1.56 mmol, 1.081 g), and NEt
distilled, dry THF (10 mL) was stirred for 48 h at room temperature.
The precipitated [NHEt ]Cl was filtered off and washed with THF
6
] (2) (0.158 g, 0.2 mmol), ClC(O)C
6 2
H (3,4,5-
OC12
H )
25 3
3
(0.84 mL, 6 mmol) in freshly
3
(
2 × 3 mL). The volatile materials were evaporated in vacuo. The
resulting pale yellow oil was purified by chromatography using a silica
gel column and hexane/ethyl acetate (20/1) as eluent. Compound 8 was
finally dried in vacuo at 40 °C for 48 h.
Yield: 0.674 g, 75%. Anal. Calcd (%) for C294
486 3 36 3
H N O P
(
0
(
3
4732.03): C, 74.62; H, 10.35; N, 0.89. Found: C, 75.03; H, 9.82; N,
.83. IR (Nujol): 1732 cm (s) (CdO); 1201 (s, br), 1172 (vs, br)
-
1
PdN); 954 cm (s) (P-O). 31P{ H} NMR (CDCl
-
1
1
): δ ) 9.21 (s,
],
], 3.94 [t,
), 0.87 (br,
): δ ) 164.95 [1C; C(O)]; 153.00,
48.09, 143.10, 123.75, 123.02, 121.89, 108.48 (12C; aromatic carbons);
3.60, 69.23 (3C; OCH ), 32.02, 29.87, 29.76, 29.58, 29.47, 26.22,
2.78 (30C; CH ), 14.19 (3C; CH ). MALDI-TOF (9-nitroanthracene
3
1
P; N P
3 3
ring). H NMR (CDCl
3
3
6 2 25 3
): δ ) 7.31 [s, 2H; C H (OC12H )
7
.11 (m, 4H; OC
6
H
4
O), 4.01 [t, J(H,H) ) 5.9 Hz, 2H; OCH
], 1.77-1.26 (m, 60H; CH
). C{ H} NMR (CDCl
2
Acid chlorides23 were prepared by literature methods. All of the
reactions were carried out under a dry argon atmosphere.
3
J(H,H) ) 5.6 Hz, 4H; OCH
2
2
13
1
9
1
7
2
H; CH
3
3
(
20) (a) Barber a´ , J.; Gim e´ nez, R.; Marcos, M.; Serrano, J. L. Liq. Cryst. 2002,
2
2
9, 309. (b) Serrano, J. L.; Marcos, M.; Mart ´ı n, R.; G o´ nzalez, M.; Barber a´ ,
J. Chem. Mater. 2003, 15, 3866. (c) Barber a´ , J.; Marcos, M.; Serrano, J.
L. Chem. Eur. J. 1999, 5, 1834. (d) Marcos, M.; Gim e´ nez, R.; Serrano, J.
L.; Donnio, B.; Heinrich, B.; Guillon, D. Chem. Eur. J. 2001, 7, 1006. (e)
Donnio, B.; Barber a´ , J.; Gim e´ nez, R.; Guillon, D.; Marcos, M.; Serrano, J.
L. Macromolecules 2002, 35, 370.
2
3
+
with silver triflate): m/z 4839 (M + Ag).
Synthesis of [N (OC {OC(O)C
(OC OH-4)] (10). A mixture of [N (OC
.4 mmol), ClC(O)C (3,4,5-OC12 (2.6 mmol, 1.80 g), and NEt
(1.6 mL, 11.4 mmol) in freshly distilled dry THF (25 mL) was stirred
for 72 h at room temperature. The precipitated [NHEt ]Cl was filtered
3
P
3
6
H
4
6
H
2
(3,4,5-OC12
25 3 5
H ) -4}) -
6
H
4
P
3 3
6
H
4
OH-4) ] (2) (0.316 g,
6
(
21) Saez, I. M.; Goodby, J. W. J. Mater. Chem. 2005, 15, 26.
22) (a) Abizanda, D.; Crespo, O.; Gimeno, M. C.; Jim e´ nez, J.; Laguna, A. Chem.
Eur. J. 2003, 9, 3310. (b) Adell, J. M.; Alonso, M. P.; Barber a´ , J.; Oriol,
L.; Pi n˜ ol, M.; Serrano, J. L. Polymer 2003, 44, 7829.
0
H
6 2
H )
25 3
3
(
3
(
23) Furniss, B. S.; Hannaford, A. J.; Smith, P. W. G.; Tatchell, A. R. Vogel’s
off and washed with THF (3 × 5 mL). Evaporation of the solvent gave
a pale yellow oil, which proved to be a mixture of 8, 10, and ClC(O)-
Textbook of Practical Organic Chemistry; Pearson-Prentice Hall: Essex,
1
989, p 692.
J. AM. CHEM. SOC.
9
VOL. 127, NO. 25, 2005 9001

A R T I C L E S
Barber a´ et al.
C
H (3,4,5-OC12H )
6 2 25 3
. The resulting pale yellow oils of 8 (0.214 g,
Anal. Calcd (%) for C274H N O P
446 3 35 3
(4435.49): C, 74.20; H, 10.14;
1
1.3%) and 10 (0.361 g, 22.1%) were purified by chromatography using
N, 0.95. Found: C, 74.15; H, 11.60; N, 0.74. IR (Nujol): 1732 (s)
-1
31
1
a silica gel column and hexane/ethyl acetate (20/1) as eluent and dried
in vacuo at 40 °C.
(CdO); 1201 (s, br), 1172 (vs, br) (PdN); 954 cm (s) (P-O). P{ H}
1
NMR (CDCl ): δ ) 9.35 (s, 3P; N P ring). H NMR (CDCl ): δ )
3
3
3
3
The data for 10 follow. Anal. Calcd (%) for C251
4074.95): C, 73.98; H, 10.14; N, 1.03. Found: C, 74.03; H, 10.00;
N, 1.02. IR (Nujol): 1732 (s) (CdO); 1201 (s, br), 1172 (vs, br) (PdN);
H
410
N
3
O P
32 3
7.66-6.99 (m, 37H; aromatic protons), 4.40 (m, 1H; OCH), 4.31 (m,
1H; OCH), 4.03-3.93 (m, 30H; OCH ), 1.85-1.26 (m, 326H; CH ),
(
2
2
0.87 (m, 51H; CH3). 13C{
1
H} NMR (CDCl ): δ ) 164.92 [6C; C(O)];
3
-
1
31
1
9
55 cm (s) (P-O). P{ H} NMR (CDCl ): δ ) 10.70 (1P), 9.19
3
1
52.93, 148.11, 143.21, 123.80, 122.98, 121.88, 108.63 (72C; aromatic
carbons); 73.61, 69.33 (17C; OCH), 32.0, 30.52, 29.75, 29.57, 29.47,
6.21, 25.51 22.77, 19.84, 19.72 (162C; CH ), 14.15 (17C; CH ).
2
1
(
2P) (AB
2
system, JAB ) 87.9 Hz; N
(OC12 ], 7.33 [s, 2H; C
], 7.20-7.12 (m, 12H; OC
O), 6.72 (“d”, J ) 8.8 Hz, 2H; OC
O), 6.1 (br, 1H; OH), 4.06-3.94 (m, 30H;
3
P
3
ring). H NMR (CDCl
], 7.32
O), 7.09-7.02
O), 6.51 (“d”,
3
):
δ ) 7.35 [s, 4H; C
6
H
2
H
25
)
3
6 2 25 3
H (OC12H )
2
2
3
[s, 4H; C
6
H
2
(OC12
H
25
)
3
6
H
H
6 4
4
+
MALDI-TOF (dithranol): m/z 4435.5 (M ).
(m, 8H; OC
6
H
4
J ) 8.8 Hz, 2H; OC
OCH ), 1.84-1.26 (m, 300H; CH
CDCl ): δ ) 165.68, 164.96 [5C; C(O)]; 153.1, 153.04, 148.12,
6 4
H
13
1
Acknowledgment. Financial support from the CICYT
2
2 3
), 0.87 (m, 45H; CH ). C{ H} NMR
(MAT2002-04118-C02-01), MEC (CTQ2004-05495-C02-01/
(
3
1
1
48.02, 147.76, 143.49, 143.21, 123.79, 123.47, 122.98, 122.85, 121.94,
21.52, 108.72, 108.62 (66C; aromatic carbons); 73.63, 69.34 (15C;
BQU) projects, and FEDER funds and support from “Gobierno
de Arag o´ n” to research groups are gratefully acknowledged.
Authors acknowledge Dr. T. Sierra for her help and fruitful
discussion about this work.
OCH
2
), 32.01, 29.76, 29.56, 29.47, 26.21, 22.78 (30C; CH
2
), 14.17
+
(
15C; CH
Synthesis of [N
OC {OC(O)C
CH (CH (R)-CH(CH
NEt (0.3 mL, 2 mmol) were added to a solution of 10 (0.074 mmol,
.301 g) in THF (25 mL), and the mixture was stirred for 4 d at room
temperature. The precipitated [NHEt ]Cl was filtered off and washed
3
). MALDI-TOF (dithranol): m/z 4075.1 (M + 1).
3
P
3
(OC
[3,4-O(R)-CH(CH
)O} C(O)Cl (0.26 mmol, 0.103 g) and
6
H
4
{OC(O)C
6
H
2
(3,4,5-OC12
25 3 5
H ) -4}) -
(
{
H
6 4
6
H
3
3
)(CH
2 5
)
CH -4})] (11). 3,4-
3 2
]
)
5
3
2
C
6
H
3
Supporting Information Available: Synthesis and structural
characterization of 3-7, 9; NMR spectra of 9; thermal behavior
and micrographs of 8; X-ray pattern of 7 at room temperature.
This material is available free of charge via the Internet at
http://pubs.acs.org.
3
2
3
0
3
with THF (3 × 5 mL). Evaporation of the solvent gave a pale yellow
oil, which was washed with acetone (2 × 10 mL) and dried in vacuo
at 40 °C for 48 h. The resulting pale yellow oil obtained of 11 contained
ca. 4% of 10. Yield: 0.227 g, 69.3%.
JA051042W
9002 J. AM. CHEM. SOC.
9
VOL. 127, NO. 25, 2005