Self-organization of phthalocyanine-[60]fullerene dyads in liquid crystals

Article abstract of DOI:10.1021/jo7022763

(Chemical Equation Presented) The use of blends in which a mesogen induces mesomorphism into a non-mesogenic compound has made possible the self-organization of phthalocyanine - [60]fullerene (Pc-C₆₀) dyads into liquid crystals. Pc-C₆₀ dyads 1, 2, or 3, in which two photoactive units are brought together by a phenylenevinylene spacer, have been synthesized through a Heck reaction that links 4-vinylbenzaldehyde to a monoiodophthalocyanine precursor, followed by standard cycloaddition of azomethine ylides - generated from the formylPc derivative and N-methylglycine - to one of the double bonds of C₆₀. The mesomorphic and thermal properties of different mixtures formed by the liquid-crystalline phthalocyanine 4 and dyads 1, 2, or 3 were examined using polarizing optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD). DSC diagrams of the blends show clear transitions from the crystalline state to a mesophase, and the measured structural parameters obtained from the powder diffraction experiments are consistent with a discotic hexagonal columnar (Col_h) structure. Considering that segregation in domains of separated molecules of Pc-C₆₀ dyad and phthalocyanine 4 would preclude mesomorphism due to the mismatch in the column diameter and to the lack of mesogenic character of the pure dyads, a predominance of alternating stacking is proposed. Additionally, the observed decrease in the calculated density of the blend mesophases relative to the mesophase of pure compound 4 is important evidence in this direction.

Full text of DOI:10.1021/jo7022763

Self-Organization of Phthalocyanine-[60]Fullerene Dyads in Liquid
Crystals
Andre´s de la Escosura,† M. Victoria Mart´ınez-D´ıaz,† Joaqu´ın Barbera´,*,‡ and
Toma´s Torres*,†
Departamento de Qu´ımica Orga´nica, UniVersidad Auto´noma de Madrid, Cantoblanco, 28049-Madrid,
Spain, and the Departamento de Qu´ımica Orga´nica-ICMA, UniVersidad de Zaragoza-CSIC, 50009
Zaragoza, Spain
tomas.torres@uam.es; jbarbera@unizar.es
ReceiVed October 22, 2007
The use of blends in which a mesogen induces mesomorphism into a non-mesogenic compound has
made possible the self-organization of phthalocyanine-[60]fullerene (Pc-C60) dyads into liquid crystals.
Pc-C60 dyads 1, 2, or 3, in which two photoactive units are brought together by a phenylenevinylene
spacer, have been synthesized through a Heck reaction that links 4-vinylbenzaldehyde to a monoiodoph-
thalocyanine precursor, followed by standard cycloaddition of azomethine ylidessgenerated from the
formylPc derivative and N-methylglycinesto one of the double bonds of C60. The mesomorphic and
thermal properties of different mixtures formed by the liquid-crystalline phthalocyanine 4 and dyads 1,
2, or 3 were examined using polarizing optical microscopy (POM), differential scanning calorimetry
(DSC), and X-ray diffraction (XRD). DSC diagrams of the blends show clear transitions from the crystalline
state to a mesophase, and the measured structural parameters obtained from the powder diffraction
experiments are consistent with a discotic hexagonal columnar (Colh) structure. Considering that segregation
in domains of separated molecules of Pc-C60 dyad and phthalocyanine 4 would preclude mesomorphism
due to the mismatch in the column diameter and to the lack of mesogenic character of the pure dyads,
a predominance of alternating stacking is proposed. Additionally, the observed decrease in the calculated
density of the blend mesophases relative to the mesophase of pure compound 4 is important evidence in
this direction.
Introduction
attracted growing attention,2 since these photoactive systems
can give rise to long-lived photoinduced charge-separated states,3
opening the way to devices capable of performing complex
functions such as molecular switches, receptors, or photovoltaic
cells.
Phthalocyanines (Pcs), one of the best known synthetic
porphyrin analogues, have been considered for many years
fashionable building blocks to construct functional materials for
technological applications.1 More recently, donor-acceptor
dyads formed by phthalocyanine and fullerene moieties have
It has been shown that the efficiency of organic photovoltaics
can be improved by controlling the supramolecular organization
of the molecules at the nanometric scale.4 Self-organization in
liquid-crystalline phases offers a unique route to the formation
of columnar stacks of photoactive molecules.5 There are already
* Address correspondence to this authors.
† Universidad Auto´noma de Madrid.
‡ Universidad de Zaragoza-CSIC.
10.1021/jo7022763 CCC: $40.75 © 2008 American Chemical Society
Published on Web 01/16/2008
J. Org. Chem. 2008, 73, 1475-1480
1475

de la Escosura et al.
FIGURE 1. Components for the liquid-crystalline phthalocyanine-C60 blends.
in the literature many examples of liquid crystals formed by
either phthalocyanine6 or fullerene7 derivatives. However, to
the best of our knowledge, mesogenic Pc-C60 dyads have never
been reported, most probably due to the tedious purification of
the unsymmetrically substituted phthalocyanines when they
possess long hydrocarbon chains at the periphery, which is a
structural requirement to induce mesomorphism on this class
of discotic molecules. Moreover, a bulky unit such as C60 cannot
be easily accommodated into a LC columnar organization.
The use of blends, in which a mesogen induces mesomor-
phism to a non-mesogenic compound, represents an elegant
strategy to overcome this problem.8 Herein, we describe for the
first time the organization of Pc-C60 dyads within liquid-
crystalline phases. In this study, a hexagonal columnar phase
was obtained by simply blending either compounds 1, 2, or 3,
bearing at the periphery butoxy, propylsulfonyl, and tert-butyl
substituents, respectively, with the discotic mesogen Zn(II)-
octakis(hexadecylthio)phthalocyanine (4) (Figure 1). Different
types of substituents (electron donor butoxy, electron deficient
propylsulfonyl, bulky tert-butyl groups) have been introduced
at the periphery of the Pc moiety of the dyad to establish their
influence in the final organization within the blend. Although
(1) (a) Hanack, M.; Heckmann, H.; Polley, R. In Methods in Organic
Chemistry (Houben-Weyl); Schaumann, E., Ed.; Thieme: Stuttgart, Ger-
many, 1998; Vol. E 9d, p 717. (b) de la Torre, G.; Nicolau, M.; Torres, T.
In Phthalocyanines: Synthesis, Supramolecular Organization and Physical
Properties (Supramolecular PhotosensitiVe and ElectroactiVe Materials);
Nalwa, H. S., Ed.; Academic Press: New York, 2001. (c) The Porphyrin
Handbook; Kadish, K. M., Smith, K. M., Guilard, R., Eds.; Academic
Press: San Diego, CA, 2003; Vols. 15-20. (d) de la Torre, G.; Va´zquez,
P.; Agullo´-Lo´pez, F.; Torres, T. J. Mater. Chem. 1998, 8, 1671-1683. (e)
de la Torre, G.; Va´zquez, P.; Agullo´-Lo´pez, F.; Torres, T. Chem. ReV. 2004,
104, 3723-3750. (f) de la Torre, G.; Torres, T.; Claessens, C. G. Chem.
Commun. 2007, 2000-2015.
(2) (a) Linssen, T. G.; Durr, K.; Hanack, M.; Hirsch, A. Chem. Commun.
1995, 103-104. (b) Durr, K.; Fiedler, S.; Linssen, T.; Hirsch, A.; Hanack,
M. Chem. Ber. 1997, 130, 1375-1378. (c) Sastre, A.; Gouloumis, A.;
Vaquez, P.; Torres, T.; Doan, V.; Schwartz, B. J.; Wudl, F.; Echegoyen,
L.; Rivera, J. Org. Lett. 1999, 1, 1807-1810. (d) Gouloumis, A.; Liu, S.-
G.; Sastre, A.; Va´zquez, P.; Echegoyen, L.; Torres, T. Chem. Eur. J. 2000,
6, 3600-3607.
(3) (a) Guldi, D. M.; Gouloumis, A.; Va´zquez, P.; Torres, T. Chem.
Commun. 2002, 2056-2057. (b) Guldi, D. M.; Ramey, J.; Mart´ınez-D´ıaz,
M. V.; de la Escosura, A.; Torres, T.; Da Ros, T.; Prato, M. Chem. Commun.
2002, 2774-2775. (c) Loi, M. A.; Neugebauer, H.; Denk, P.; Brabec, C.
J.; Sariciftci, N. S.; Gouloumis, A.; Va´zquez, P.; Torres, T. J. Mater. Chem.
2003, 13, 700-704. (d) Guldi, D. M.; Zilbermann, I.; Gouloumis, A.;
Va´zquez, P.; Torres, T. J. Phys. Chem. B 2004, 108, 18485-18494. (e)
El-Khouly, M. E.; Ito, O.; Smith, P. M.; D’Souza, F. J. Photochem.
Photobiol. C: Photochem. ReV. 2004, 5, 79-104. (f) Guldi, D. M.;
Gouloumis, A.; Va´zquez, P.; Torres, T.; Georgakilas, V.; Prato, M. J. Am.
Chem. Soc. 2005, 127, 5811-5813. (g) de la Escosura, A.; Mart´ınez-D´ıaz,
M. V.; Guldi, D. M.; Torres, T. J. Am. Chem. Soc. 2006, 128, 4112-4118.
(h) Ballesteros, B.; de la Torre, G.; Torres, T.; Hug, G. L.; Rahman, G. M.
A.; Guldi, D. M. Tetrahedron 2006, 62, 2097-2101. (i) Gouloumis, A.; de
la Escosura, A.; Va´zquez, P.; Torres, T.; Guldi, D. M.; Neugebauer, H.;
Winder, C.; Drees, M.; Sariciftci, N. S. Org. Lett. 2006, 8, 5187-5190. (j)
Isosomppi, M.; Tkachenko, N. V.; Efimov, A.; Vahasalo, H.; Jukola, J.;
Vainiotalo, P.; Lemmetyinen, H. Chem. Phys. Lett. 2006, 430, 36-40.
(4) Schmidt-Mende, L.; Fechtenko¨tter, A.; Mu¨llen, K.; Moons, E.; Friend,
R. H.; MacKenzie, J. D. Science 2001, 293, 1119-1122.
(5) Kumar, S. Chem. Soc. ReV. 2006, 35, 83-109.
(6) (a) van Nostrum, C. F.; Nolte, R. J. M. Chem. Commun. 1996, 2385-
2392. (b) Eichhorn, H.; Bruce, D.; Woehrle, W. D. AdV. Mater. 1998, 10,
419-422. (c) Duro, J. A.; de la Torre, G.; Barbera, J.; Serrano, J. L.; Torres,
T. Chem. Mater. 1996, 8, 1061-1064. (d) Swarts, J. C.; Langner, E. H.
G.; Krokeide-Hove, N.; Cook, M. J. J. Mater. Chem. 2001, 11, 225-236.
(e) Maeda, F.; Hatsusaka, K.; Ohta, K.; Kimura, M. J. Mater. Chem. 2003,
13, 243-251.
(7) (a) Chuard, T.; Deschenaux, R. J. Mater. Chem. 2002, 12, 1944-
1951. (b) Campidelli, S.; Va´zquez, E.; Milic, D.; Prato, M.; Barbera´, J.;
Guldi, D. M.; Marcaccio, M.; Paolucci, D.; Paolucci, F.; Deschenaux, R.
J. Mater. Chem. 2004, 14, 1266-1272. (c) Allard, E.; Oswald, F.; Donnio,
B.; Guillon, D.; Delgado, J. L.; Langa, F.; Deschenaux, R. Org. Lett. 2005,
7, 383-386. (d) Lenoble, J.; Maringa, N.; Campidelli, S.; Donnio, B.;
Guillon, D.; Deschenaux, R. Org. Lett. 2006, 8, 1851-1854. (e) Sawamura,
M.; Kawai, K.; Matsuo, Y.; Kanie, K.; Kato, T.; Nakamura, E. Nature 2002,
419, 702. (f) Matsuo, Y.; Muramatsu, A.; Hamasaki, R.; Mizoshita, N.;
Kato, T.; Nakamura, E. J. Am. Chem. Soc. 2004, 126, 432. (g) Matsuo, Y.;
Muramatsu, A.; Kamikawa, Y.; Kato, T.; Nakamura, E. J. Am. Chem. Soc.
2006, 128, 9586. (h) Zhong, Y.-W.; Matsuo, Y.; Nakamura, E. J. Am. Chem.
Soc. 2007, 129, 3052-3053.
(8) (a) Goldmann, D.; Janietz, D.; Schmidt, C.; Wendorff, J. H. Angew.
Chem., Int. Ed. 2000, 39, 1851-1854. (b) Reczek, J. J.; Villazor, K. R.;
Lynch, V.; Swager, T. M.; Iverson, B. L. J. Am. Chem. Soc. 2006, 128,
7995-8002.
1476 J. Org. Chem., Vol. 73, No. 4, 2008

Self-Organization of Phthalocyanine-[60]Fullerene Dyads
SCHEME 1. Synthesis of Pc-C60 Dyads 1, 2, and 3
SCHEME 2. Synthesis of Propylsulfonyl-Substituted Phthalocyanines 5b and 9
the self-organization of a non-mesogenic fullerene derivative
into columnar liquid crystals has already been described
following a similar strategy,9 the well-known photoinduced
charge-transfer properties of Pc-C60 dyads make the current
approach potentially more suitable for the construction of new
efficient phthalocyanine-based photovoltaic devices.
reaction of the resulting Pc-formyl derivatives 6a-c with C60
and sarcosine led to the target dyads.
In the case of the propylsulfonyl-substituted derivatives, the
required Pd(II)-iodophthalocyanine precursor 5 was not de-
scribed in the literature. Attempts to prepare it by cross
condensation of the corresponding phthalonitriles in the presence
of Pd(OAc)2 led to the compound in very low yields. This result
is not due to a lower reactivity of the 3,4-bis(propylsulfonyl)-
phthalonitrile but to the necessary change of the solvent used
in the macrocyclization to avoid nucleophilic displacement of
the sulfonyl groups. Instead, an alternative route was employed
in which 1,3-diiminoisoindolines 713 and 8 were reacted in a
refluxing mixture of DMF and o-DCB, leading to the formation
of a statistical mixture of metal-free Pcs, from which phthalo-
cyanines 5b and 9 were separated by column chromatography
(Scheme 2). For the Heck reaction of 5b with 4-vinylbenzal-
dehyde, 1.1 equiv of Pd(OAc)2 was used to accomplish in the
same step both the C-C coupling and the introduction of the
Pd atom into the central cavity of the macrocycle. The synthesis
of the free-base formylPc 6b was also attempted employing
Results and Discussion
Synthesis. The synthesis of Pc-C60 dyads 1,3g 2, and 3 was
carried out in two steps (Scheme 1). First, iodophthalocyanine
precursors 5a-c, bearing butoxy,10 propylsulfonyl, and tert-
butyl substituents,11 respectively, were connected to 4-vinyl-
benzaldehyde12 by means of a Heck reaction. Subsequent Prato
(9) (a) Kimura, M.; Saito, Y.; Ohta, K.; Hanabusa, K.; Shirai, H.;
Kobayashi, N. J. Am. Chem. Soc. 2002, 124, 5274-5275. (b) Bushby, R.
J.; Hamley, I. W.; Liu, Q.; Lozman, O. R.; Lydon, J. E. J. Mater. Chem.
2005, 15, 4429-4434.
(10) Garc´ıa-Frutos, E.; D´ıaz, D. D.; Va´zquez, P.; Torres, T. Synlett 2006,
3231.
(11) Maya, E. M.; Va´zquez, P.; Torres, T. Chem. Eur. J. 1999, 5, 2004-
2013.
(12) Mckean, D. R.; Parrinello, G.; Renaldo, A. F.; Stille, J. K. J. Org.
Chem. 1987, 52, 422-424.
(13) Maya, E. M.; Haisch, P.; Va´zquez, P.; Torres, T. Tetrahedron 1998,
54, 4397.
J. Org. Chem, Vol. 73, No. 4, 2008 1477

de la Escosura et al.
TABLE 1. Phase Transition Temperatures and Enthalpies for
Compound 4 and Blends 4/1, 4/2, and 4/3 Determined by
Differential Scanning Calorimetrya
TABLE 2. X-ray Measurements on the Liquid-Crystalline Phases
of Compound 4 and (1:1) Blends of 4/1, 4/2 and 4/3a
lattice
constant
a (Å)
calcd
density
(g‚cm-3
T [°C] (∆H [J/g])
T [°C]
T
dmeas
(Å)
dcalcd
(Å)
sample (°C)
M
hkl
)
sample
Cr
1st scan
2nd scan
Colh
(∆H [J/g])
I
4
110 Colh 30.8
31.0 100
17.9 110
15.5 200
35.8
1.12
4
•
•
89 (35)
61 (13)
70 (15)
-
34 (54)
24 (17)
26 (11)
-
•
•
•
•
260 (4.3)
>250b
•
•
•
•
18.2
15.4
4/1
4/2
4/3
•
>250b
4.6 (br)
3.5
-
>250b
a Key: (•) phase is observed; (-) phase is not observed. Cr ) crystalline
phase. Colh ) hexagonal columnar. I ) isotropic liquid phase. b Transition
observed only by POM.
4/1
4/2
110 Colh 30.8
30.8 100
35.6
37.8
0.99
0.91
4.6 (br)
3.45
90 Colh 32.8
32.7 100
18.9 110
16.4 200
19.1
16.1
4.6 (br)
lower amounts of the catalyst without success. Another impor-
tant reaction parameter to be controlled was the temperature,
since some extent of deiodination and homocoupling competitive
processes from the starting iodoPc have been detected over
80 °C.
(Alkylsulfonyl)Pc derivatives are very rare in the literature
despite their interesting properties. For instance, they are unique
examples of soluble electron-acceptor phthalocyanines with a
low tendency toward aggregation. Both iodoPc 5b and the
formylPc 6b are intermediate compounds in the synthesis of
dyad 2, but also interesting derivatives in general for the organic
chemists working on phthalocyanine synthesis.
3.5
25 Colh 30.8
17.6
4/3
30.7 100
17.7 110
15.3 200
35.4
0.96
15.3
4.6 (br)
3.4
a Colh: hexagonal columnar mesophase. dmeas and dcalc are the measured
and calculated diffraction spacing. Br ) broad. hkl are the indexations of
the reflections corresponding to the Colh phase. a is the lattice parameter
of the hexagonal columnar phase. For the calculation of a see the Supporting
Information.
1 lists the phase transition temperatures and enthalpy changes
established by DSC and POM experiments. In optical micros-
copy, all blends showed birefringence in a wide range up to
250 °C, although characteristic textures were not observed. The
mesophases of the blends were found to be very viscous at low
temperatures, and fluidity appeared only when the samples were
heated well above 100 °C. As a consequence of this, not every
DSC peak could be confirmed optically.
DSC diagrams of blends 4/1 and 4/2 show unequivocal
transitions from the crystalline state to a mesophase (Supporting
Information). Interestingly, the crystal-mesophase transition
temperatures of the blends are slightly lower than that of the
pure intrinsically mesogenic compound 4. For instance, while
4 enters the liquid-crystalline phase at 89 °C, the heating curves
for blends 4/1 and 4/2 show melting peaks at 61 and 70 °C,
respectively. Repetitive heating and cooling scans result in a
decrease of these transition temperatures and therefore in a
broadening of the mesophase range. Concerning blend 4/3, its
DSC curves resemble the ones described above but are more
poorly resolved, probably due to the bulkiness of the tert-butyl
groups in dyad 3, and it is not possible to clearly identify the
transition peaks. The DSC curves are consistent with blend 4/3
being mesomorphic at room temperature, which was confirmed
by XRD (see below).
The transition of the blends from the mesophase to the
isotropic liquid was detected in all cases by optical microscopy.
Although it is difficult to determine the temperature at which
the transition occurs because it is slow and because of the
absence of DSC peaks, we conclude that the mesophases are
stable at least up to 250 °C (temperature close to the clearing
point of pure 4).
XRD studies were performed to identify the type of me-
sophase structure displayed by the mixed systems 4/1, 4/2, and
4/3 (X-ray diffractograms included in the Supporting Informa-
tion). Table 2 summarizes the lattice parameters obtained from
these experiments, carried out at temperatures close to 100 °C,
except for blend 4/3, which is liquid cystalline at room
temperature.
The mesogenic phthalocyanine 4 was synthesized with a 49%
yield by a standard macrocyclation procedure of 4,5-bis-
(hexadecylthio)phthalonitrile14 in the presence of ZnCl2 and
DMAE as solvent.
All the compounds were fully characterized by NMR, FTIR,
1
MALDI-MS, and UV/vis spectroscopy. The H NMR spectra
in CDCl3 of dyads 2 and 3 are poorly resolved due to
aggregation at the experimental NMR concentrations. However,
signals assigned to the pyrrolidine ring can be clearly observed
between 4.3 and 5.2 ppm, as well as the N-CH3 resonance at
2.95 ppm. Concerning mass spectrometry, peaks corresponding
to the [M - C60]+ fragment appear in the MALDI-TOF spectra
of dyads, together with the molecular ions [M+] or [M + H]+
as major species. Split Q-bands are observed in the UV/vis
spectra in CHCl3 of dyad 2 and its precursors. In both cases
(dyads 2 and 3) the Q-bands are shifted to higher wavelengths
when compared to the spectra of the monoiodo precursors, as
a consequence of the extended π-conjugation (all the spectra
are shown in the Supporting Information).
Study of the Liquid-Crystalline Properties. The mesomor-
phic and thermal properties of each of the pure components,
i.e., phthalocyanine 4 and the Pc-C60 dyads 1, 2, and 3, were
examined before blending, using polarizing optical microscopy
(POM), differential scanning calorimetry (DSC), and X-ray
diffraction (XRD). Compound 4 shows, as previously described
for analogous phthalocyanines,15 a hexagonal columnar (Colh)
mesophase between 89 and 260 °C (first heating cycle) or
between 43 and 260 °C (second heating cycle). In contrast, the
dyads 1, 2, and 3 do not present mesomorphic behavior but are
crystalline and do not melt below 350 °C. Once the pure
components were studied, 1:1 mixtures of phthalocyanine 4 and
the dyads 1, 2, or 3 were prepared by evaporation of the solvent
from THF solutions, and their phase behavior evaluated. Table
(14) Del Rey, B.; Mart´ınez-D´ıaz, M. V.; Barbera´, J.; Torres, T. J.
Porphyrins Phthalocyanines 2000, 4, 569-573.
(15) Ban, K.; Nishizawa, K.; Ohta, K.; Sirai, K. J. Mater. Chem. 2000,
10, 1083-1085.
1478 J. Org. Chem., Vol. 73, No. 4, 2008

Self-Organization of Phthalocyanine-[60]Fullerene Dyads
mesogenic dyads in which the phthalocyanine is linked to
another photo- or electroactive subunit. Since phthalocyanine-
based dyads, including the Pc-C60 dyad 1,3g can undergo
photoinduced electron transfer in appropriate conditions, the
current approach could be also potentially useful in the
photovoltaics field for improving the morphology in bulk
heterojunctions by increasing the dissociation efficiency of
bound electron-hole pairs at the donor-acceptor interface.
Future experiments will be devoted to explore the photovoltaic
properties of these kinds of systems.
Experimental Section
Pc-C60 Dyad 2. A mixture of C60 (40 mg, 0.055 mmol) and
sarcosine (1.6 mg, 0.018 mmol) was dissolved in 6 mL of o-DCB
under argon atmosphere at 60 °C. Afterward, a solution of
phthalocyanine 6b (25 mg, 0.018 mmol) in 4 mL of o-DCB was
added. The reaction mixture was heated at 110 °C for an additional
8 h. After being cooled to room temperature the solvent was
evaporated. The crude was purified by column chromatography on
silica gel. Nonreacted C60 was eluted with toluene, while a mixture
of toluene/THF (20:1) was used to elute compound 2. Finally, the
product was triturated with methanol and washed with acetone and
ethyl acetate, obtaining 15 mg of a dark blue solid. Yield: 40%.
FIGURE 2. Schematic representation of the most probable structure
of the mesophases formed by the Pc/Pc-C60 blends 4/1, 4/2, and 4/3.
Powder diffraction patterns of all samples contain the typical
reflections of a columnar mesophase of substituted phthalocya-
nines. In the low-angle region, a set of up to three reflections
corresponding to a reciprocal spacing ratio of 1:31/2:2, consistent
with a two-dimensional hexagonal lattice, is present. Hence, a
discotic hexagonal columnar (Colh) structure of the mesophases
can be proposed. The hexagonal lattice constant a can be
deduced from these spacing values.
1
Mp >250 °C. H NMR (300 MHz, CDCl3) δ 10.0-9.5 (m, 6H),
9.2-8.8 (m, 2H), 8.2 (m, 1H), 7.9 (m, 4H), 7.7, 7.3 (AB system,
2H), 5,12 (s, 1H), 5.1 (d, J ) 9.38 Hz, 1H), 4.37 (d, J ) 9.38 Hz,
1H), 4.1 (m, 12H), 2.95 (s, 3H), 2.2 (m, 12H), 1.2 ppm (m, 18H).
FT-IR (KBr) ν 3443 (ArC-H), 2962, 2922, 2852 (CH), 1637 (Cd
C), 1508, 1458 (C-N), 1292, 1145, 1082 (SO2), 1030, 921, 875
cm-1. UV/vis (CHCl3) λmax (log ꢀ) 698 (4.98), 665 (5.08), 644
(4.77), 605 (4.56), 432 (4.05), 342 (5.02), 257 nm (5.21). MALDI-
TOF MS (dithranol) m/z 2130 [M + H]+, 2129 [M+], 1408 [M -
C60]+. Anal. Calcd for C121H62N9O12PdS6 (2132.65): C, 68.15; H,
2.93; N, 5.91; S, 9.02. Found: C, 68.03; H, 3.01; N, 5.87; S, 8.98.
Pc-C60 Dyad 3. A mixture of C60 (96 mg, 0.13 mmol) and
sarcosine (4 mg, 0.045 mmol) was dissolved in 10 mL of o-DCB
under argon atmosphere at 60 °C. Afterward, a solution of
phthalocyanine 6c (39 mg, 0.045 mmol) in 5 mL of o-DCB was
added. The reaction mixture was heated at 110 °C for an additional
8 h. After being cooled to room temperature the solvent was
evaporated. The crude was purified by column chromatography on
silica gel. Nonreacted C60 was eluted with toluene, while a mixture
of toluene/THF (50:1) was used to elute compound 3. Further
purification by a Bio-Beads column in THF was carried out to
remove bisaduct derivatives. Finally, the product was triturated with
methanol and washed with acetone and ethyl acetate, obtaining 28
In the high-angle region of the X-ray patterns there are two
diffuse scattering haloes: the first, very broad and typically
observed in liquid-crystalline phases, corresponds to an average
distance of 4.6 Å and arises from short-range interactions
between the conformationally disordered aliphatic chains; the
second is not so broad and corresponds to a distance of 3.4-
3.5 Å, characteristic of the stacking of the disc-like molecules.
In all cases, the measured structural parameters are consistent
with a discotic hexagonal columnar (Colh) structure, and the
decrease in the calculated density of the blend mesophases
relative to the pure mesophase of compound 4 (Table 2) suggest
an alternating stacking. However, considering that the order
arising from the fullerene moieties is not visible in the powder
diffractograms, the existence of some disorder cannot be
excluded from these results (i.e., the alternating stacking is
probably not long range). We actually propose a mixed model
as the most probable one to explain the mesophase structure,
with a predominance of alternating stacks of dyad and phtha-
locyanine 4 and some domains with randomly distributed Pc-
C60 molecules. Figure 2 schematically depicts a hypothetical
representation of the proposed alternating stacks. The predomi-
nance of alternating stacking is evident considering that segrega-
tion in domains of separated molecules of dyad and phthalo-
cyanine 4 would preclude mesomorphism due to the mismatch
in the column diameter and to the lack of mesogenic character
of the pure dyads.
1
mg of a dark green solid. Yield: 39%. Mp >250 °C. H NMR
(300 MHz, CDCl3) δ 8.6 (m, 9H), 7.9 (m, 3H), 7.7 (m, 4H), 7.7,
7.4 (AB system, 2H), 5.06 (s, 1H), 5.05 (d, J ) 8.8 Hz, 1H), 4.34
(d, J ) 8.8 Hz, 1H), 2.95 (s, 3H), 1.7 ppm (m, 27H). FT-IR (KBr)
ν 3442 (ArC-H), 2952, 2778, (CH), 1611 (CdC), 1487 (C-N),
1089, 747, 527 cm-1. UV/vis (CHCl3) λmax (log ꢀ) 692 (5.19), 621
(4.48), 435 (4.32), 347 (5.04), 256 nm (5.20). HR-MALDI-TOF
MS (dithranol) m/z (C115H51N9Zn) calcd 1621.3556, found 1621.3552.
Anal. Calcd for C115H51N9Zn‚H2O (1642.101): C, 84,11; H, 3.25;
N, 7.68. Found: C, 84.25; H, 3.29; N, 7.40.
Conclusions
Mesogenic Phthalocyanine 4. A mixture of 4,5-bis(hexade-
cylthio)phthalonitrile12 (300 mg, 0.47 mmol), ZnCl2 (16 mg, 0.12
mmol), and DBU (0.07 mL, 0.47 mmol) in DMAE (5 mL) was
refluxed under argon for 16 h. The reaction mixture was cooled
and separated by filtration. The remaining precipitate was washed
with methanol. The residue was purified by column chromatography
(silica gel, CHCl3/hexane 9:1) and triturated with ethyl acetate to
In conclusion, induced mesomorphism by blending a non-
mesogenic molecule with a mesogen one represents a new
strategy to organize phthalocyanine-C60 dyads into liquid
crystals. In particular, the discotic phthalocyanine 4 was mixed
with different non-mesogenic Pc-C60 dyads (namely, 1, 2, or
3). In all cases, a hexagonal columnar mesophase was observed
whatever the peripheral substituent on the phthalocyanine unit.
We envisage that the same approach described in this paper
could be used to organize at a supramolecular level other non-
1
afford 188 mg of 4 as a dark green solid. Yield: 61%. H NMR
(200 MHz, CDCl3) δ 8.29 (br s, 8H), 3.1 (m, 16H), 1.8 (m, 16H),
1.4-1.0 (m, 208H), 0.84 ppm (t, J ) 7.0 Hz, 24H). MS-LSIMS
(3-NOBA) m/z 393 [M + H+]. FT-IR (KBr) ν 3074, 2930, 2855
J. Org. Chem, Vol. 73, No. 4, 2008 1479

de la Escosura et al.
(C-H), 1480, 1390, 1350, 1275, 1080, 975, 750 cm-1 (S-CH2).
UV/vis (CHCl3) λmax (log ꢀ) 711 (5.36), 640 (4.57), 368 (4.84),
330 nm (4.75). MALDI-TOF MS (dithranol) m/z 2625.8 [M+].
Iodophthalocyanine 5b. A DMF/o-DCB (1:1, 5 mL) solution
of 1,3-diiminoisoindolines 713 (60 mg, 0.22 mmol) and 8 (316 mg,
0.89 mmol) was heated at 140 °C under argon atmosphere for 12
h. After being cooled to room temperature, the solvent was removed
under reduced pressure and the crude was triturated with methanol/
water (3:1). The resulting dark blue solid was then purified by
column chromatography on silica gel, using CHCl3/THF (40:1) as
eluent. The symmetrically substituted phthalocyanine was first
eluted followed by the monoiodo derivative 5b. Yield: 35%. Mp
7.2 (m, 4H), 1.6 ppm (m, 27H). FT-IR (KBr) ν 3423 (ArC-H),
2955, 2865 (CH), 1697 (CHO), 1595 (CdC), 1488, 1089, 747 cm-1
.
UV/vis (CHCl3) λmax (log ꢀ) 698 (5.21), 683 (5.17), 622 (4.47),
357 (5.0), 293 nm (4.51). MALDI-TOF MS (dithranol) m/z 874.3
[M+].
1,3-Diiminoisoindoline 8. A stirred solution of sodium (160 mg,
7.0 mmol) in methanol (120 mL) was cooled to 0 °C in an ice-
water bath. 4,5-Bis(propylsulfonyl)phthalonitrile16 (3.0 g, 8.8 mmol)
was then added and ammonia was bubbled through the reaction
mixture. After 20 min, the solution became yellowish and TLC
showed that there was no unreacted starting material. The solvent
was then evaporated and the residue was subjected to column
chromatography on silica gel (CHCl2/methanol 9:1). In this way,
1.42 g of compound 8 was isolated as a yellow solid. Yield: 45%.
Mp 128-130 °C. 1H NMR (200 MHz, methanol-d4) δ 8.68 (s, 2H),
3.64 (t, J ) 7.0 Hz, 4H), 1.8 (m, 4H), 1.10 ppm (t, J ) 7.5 Hz,
6H). 13C NMR (300 MHz, methanol-d4) δ 143.9, 142.7, 127.6,
108.4, 57.5, 23.3, 14.2 ppm. FT-IR (KBr) ν 3305 (NH), 2926, 2857
(CH), 1678, 1634 (CdN), 1300, 1185, 1145 (SO2), 1101, 655, 588
cm-1. MS (EI) m/z 357 [M+], 251 [M - C3H7SO2]+, 144 [M - 2
× C3H7SO2]+.
1
>250 °C. H NMR (300 MHz, CDCl3) δ 10.40 (s, 2H), 10.02 (s,
1H), 9.99 (s, 1H), 9.78 (s, 1H), 9.75 (s, 1H), 9.54 (s, 1H), 8.95 (d,
J ) 8.2 Hz, 1H), 8.65 (d, J ) 8.2 Hz, 1H), 4.1 (m, 12H), 2.3 (m,
12H), 1.2 (m, 18H), -1.52 ppm (br s, 2H). FT-IR (KBr) ν 3465
(ArC-H), 2970, 2924, 2873 (CH), 1294, 1143, 1097 cm-1 (SO2).
UV/vis (CHCl3) λmax (log ꢀ) 705 (5.33), 668 (5.26), 640 (4.1), 610
(4.5), 355 (4.88), 283 nm (4.36). MALDI-TOF MS (dithranol) m/z
1276 [M+].
Formylphthalocyanine 6b. A solution of iodophthalocyanine
5b (40 mg, 0.031 mmol), 4-vinylbenzaldehyde11 (10 µL, 0.073
mmol), Et3N (0.1 mL), tetra-n-butylammonium bromide (11 mg,
0.034 mmol), and Pd(OAc)2 (7.7 mg, 0.034 mmol) in 2 mL of
anhydrous DMF was heated at 80 °C for 12 h. After the reaction
mixture was cooled to room temperature the solvent was removed
under reduced pressure. The solid residue was triturated with
methanol/water (3:1), filtered, and purified by chromatography on
silica gel with CHCl3/THF (40:1) as eluent. Compound 6b (20 mg)
Calculation of the Mesophase Parameters. a is the lattice
x
parameter of the hexagonal columnar phase (a ) 2/ 3 × d100
2
2
x
with d100 ) 1/Nhk(∑h,k dhk h +k +hk), and where Nhk is the
number of hk0 reflections); density is calculated by using the
formula F ) M/(VNA), where M is the molar mass (in g) of the
molecule (4) or the blend, NA is Avogadro’s number, and V is the
3
2
-24
x
molecular volume (in cm ) calculated as V ) a c 3/(2 × 10
)
1
(c is the stacking distance, deduced from the outer X-ray scattering
halo, corresponding to about 3.4-3.5 Å).
was obtained as a dark blue solid. Yield: 47%. Mp >250 °C. H
NMR (300 MHz, CDCl3) δ 10.13 (s, 1H), 10.1-9.5 (six s, 6H),
8.95 (br s, 1H), 8.82 (d, J ) 8.2 Hz, 1H), 8.31 (d, J ) 8.19 Hz,
1H), 8.04 (AA′XX′ system, J ) 7.6 Hz, 4H), 7.7, 7.3 (AB system,
2H), 4.1 (m, 12 H), 2.2 (m, 12H), 1.2 ppm (m, 18H). FT-IR (KBr)
ν 3441 (ArC-H), 2961, 2921, 2851 (CH), 1715 (CdO), 1607
(CdC), 1292, 1145, 1097 cm-1 (SO2). UV/vis (CHCl3) λmax (log
ꢀ) 692 (5.09), 661 (5.15), 644 (4.67), 600 (4.49), 345 (4.89), 256
nm (4.79). MALDI-TOF MS (dithranol) m/z 1383 [M + H]+, 1382
[M+].
Acknowledgment. This work has been supported by the
Spanish MEC (CTQ-2005-08933-BQU and CONSOLIDER-
INGENIO 2010 C-07- 25200), the Comunidad de Madrid (S-
0505/PPQ/000225), EU (STRP 516982, HETEROMOLMAT),
and European Science Foundation-MEC (MAT2006-28180-E,
SOHYDS).
Formylphthalocyanine 6c. A solution of tri(tert-butyl)iodoph-
thalocyanine10 (107 mg, 0.12 mmol), 4-vinylbenzaldehyde11 (16
µL, 0.12 mmol), Et3N (0.1 mL), tetra-n-butylammonium bromide
(39 mg, 0.12 mmol), and Pd(OAc)2 (1.5 mg, 0.0066 mmol) in
anhydrous DMF (3 mL) was heated at 80 °C under argon
atmosphere for 12 h. The color changed from blue to green while
the reaction proceeded. Afterward, the solvent was evaporated and
the solid residue was triturated with methanol/water (3:1), filtered,
and purified by column chromatography (SiO2, hexane/dioxane 2:1)
1
Supporting Information Available: Copies of the H NMR
and UV/vis spectra of the Pc-C60 dyads 2 and 3, and their precursors,
copies of the MALDI-TOF spectra of the Pc-C60 dyads 2 and 3,
synthetic scheme of phthalocyanine 4, and DSC curves and X-ray
diffractograms of the mesophases. This material is available free
of charge via the Internet at http://pubs.acs.org.
JO7022763
1
to afford 55 mg of 6c. Yield: 61%. Mp >250 °C. H NMR (300
MHz, DMSO-d6) δ 9.2 (s, 1H) 8.4-8.0 (m, 9H), 7.5-7.3 (m, 5H),
(16) Maya, E. M.; Concepcio´n Garc´ıa, E. M.; Va´zquez, P.; Torres, T. J.
Org. Chem. 2000, 65, 2733-2739.
1480 J. Org. Chem., Vol. 73, No. 4, 2008