Discotic liquid-crystalline materials based on porphycenes: A mesogenic metalloporphycene-tetracyanoquinodimethane (TCNQ) adduct

Article abstract of DOI:10.1002/chem.200700125

A number of substituted zinc(II) porphycenes and porphyrins have been synthesized as potentially mesogenic materials. One of the resulting porphycenes, bearing eight decyloxy chains, exhibits two mesophases, a transient lamellar phase (Lam) and a highly o

Full text of DOI:10.1002/chem.200700125

FULL PAPER
DOI: 10.1002/chem.200700125
Discotic Liquid-Crystalline Materials Based on Porphycenes: A Mesogenic
Metalloporphycene–Tetracyanoquinodimethane (TCNQ) Adduct
Marcin Ste˛pien´,[a, c] Bertrand Donnio,[b] and Jonathan L. Sessler*[a]
Abstract:
A
number of substituted
porphycene also forms an electron
donor–acceptor (EDA) complex with
ophase (Colh) that is thermally stable
up to ca. 2008C. The EDA interaction
between porphycene and TCNQ has
been probed using electronic and vi-
brational spectroscopy. A mixture of
zinc(II) porphyrins, isomeric with the
above porphycene complex, forms a
zinc(II) porphycenes and porphyrins
have been synthesized as potentially
mesogenic materials. One of the result-
ing porphycenes, bearing eight decy-
loxy chains, exhibits two mesophases, a
transient lamellar phase (Lam) and a
highly ordered lamello-columnar phase
(LCol), with remarkably different struc-
tural characteristics. The same zinc(II)
tetracyanoquinodimethane
(TCNQ),
generating a hexagonal columnar mes-
Keywords:
systems
donor–acceptor
liquid crystals
·
·
rectangular
(Colr).
columnar
mesophase
metallomesogens · porphyrinoids ·
X-ray diffraction
Introduction
of the aromatic core affect not only the stability of the mes-
ophase but also its electronic and optical characteristics.[16]
The porphyrin ring is an extremely valuable structural
motif for the construction of mesogens and metallomeso-
gens.[17] It can coordinate a wide range of metal ions and is
available with a range of peripheral substitution, some of
which are fairly easy to synthesize. These features not only
provide for structural diversity but also allow the electronic
and optical properties to be fine-tuned. To date, discotic
mesogens have been obtained from both meso- and b-substi-
Since the report of the first discotic mesogens by Chandrase-
khar in 1977,[1] this class of liquid crystals has attracted con-
siderable attention.[2–4] Discotic mesogens are of interest be-
cause their unusual structural features often result in unique
physical properties that may be employed in the construc-
tion of functional organic materials.[5] In particular, discotic
mesogens have shown promise as organic conductors with
enhanced carrier mobilities,[6,7] high-efficiency photodio-
des,[8–11] and optoelectronic data storage media.[12] Most dis-
cotic mesogens are built around large p-electron systems,
both carbo- and heterocyclic, such as triphenylenes,[13] coro-
nenes,[14] phthalocyanines, or porphyrins.[15] The properties
tuted porphyrins bearing
a
variety of functional
groups.[10,18–30] Generally, all the substituents are identical,
but unsymmetrically substituted porphyrin discotics are also
known.[29] In most cases, zinc coordination confers the great-
est stability on the porphyrin-based mesophases; however,
other ions, such as CuII,[27] MoV,[23] SiIV,[30] and VIV,[26] have
been studied and have also proved effective.[17]
´
[a] Dr. M. Ste˛pien, Prof. J. L. Sessler
Department of Chemistry & Biochemistry
University of Texas, 1 University Station A5300
Austin, TX 78712(USA)
Fax : (+1)512-471-7550
E-mail: sessler@mail.utexas.edu
A potentially interesting class of mesogens can be ob-
tained by appropriate functionalization of porphyrin ana-
logues (porphyrinoids). This family of macrocycles, charac-
terized by unusual structural diversity, includes expand-
ed,[31,32] contracted,[33] and isomeric[34] porphyrins, as well as
a range of core-modified systems.[35,36] Consequently, por-
phyrin analogues possess many intriguing properties, such as
extremely strong and red-shifted electronic absorptions,[37]
controllable conformational flexibility,[38] or the ability to
bind anions,[34,39] features that might lead to liquid-crystal
systems with unusual functionalities. Unfortunately, the task
of making a mesogenic porphyrinoid combines the usual
[b] Dr. B. Donnio
Institut de Physique et Chimie des MatØriaux de Strasbourg
UMR 7504 (CNRS-UniversitØ Louis Pasteur), 23 rue du Loess BP 43
67034 Strasbourg Cedex 2(France)
´
[c] Dr. M. Ste˛pien
Present address: Wydział Chemii, Uniwersytet Wrocławski
ul. F. Joliot-Curie 14, 50-383 Wrocław (Poland)
Supporting information for this article is available on the WWW
under http://www.chemeurj.org/ or from the author.
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6853

challenges of liquid-crystal research (design difficulties, tedi-
ous preparation of homologues, purification problems) with
those of porphyrinoid chemistry (low yields, instability of in-
termediates, etc.). Recently we reported the first discotic
liquid crystals based on expanded porphyrins.[40–42] The first
of these, a system called hydrazinophyrin, was characterized
as a free base and was found to exist as a columnar meso-
rin derivatives bearing a greater number of alkoxy chains
(1b and 2b) gave rise to liquid crystalline behavior, but that
the nature of the mesogens formed from the two cores dif-
fered. We also found that the addition of the electron defi-
cient agent tetracyanoquinodimethane (TCNQ) to the por-
phycenes helped stabilize the formation of liquid crystalline
phases.
phase as judged from polarizing optical microscopy.[40]
A
second liquid crystalline system was obtained by preparing
the uranyl complexes of a hexaazamacrocycle called alaska-
phyrin.[42] Both of these mesogens were Schiff-base derived
and hence inherently susceptible to hydrolytic instability.
Recently, however, we found that mesomorphic behavior
could also be induced in appropriately substituted cyclo[8]-
pyrroles by addition of electron-acceptor molecules, such as
polynitroaromatics.[41] These supramolecular liquid crystals
are of interest because of the unique optical properties of
cyclo[8]pyrrole and because of their potential utility as ex-
plosives sensors.
Results and Discussion
Synthesis of porphycenes and porphyrins: As in the case of
porphyrins and the other porphyrinoid systems alluded to
above, we felt the most straightforward approach to produc-
ing mesogenic materials or those in which liquid crystallinity
could be induced by addition of an appropriate additive (so-
called protomesogens) would involve peripheral substitution
with appropriately chosen solubilizing “tails”. However,
unlike porphyrins, in porphycenes the meso positions are
not uniformly distributed around the ring. Therefore, we
considered that meso-functionalization would be less likely
to provide discotic mesophases and, accordingly, decided to
focus on the construction of b-substituted porphycenes. As a
general rule, b-substituted porphycenes are also better li-
gands for metal cations than the corresponding meso deriva-
tives, a feature that was expected to abet metal insertion
once the putative mesogens were constructed. With these
considerations in mind, and taking into account some of the
successful substitution patterns known to induce mesomor-
phism in regular porphyrins,[21,27] structures 1a,b were
chosen as specific targets.
The requisite b-substituted pyrroles 4a,b were obtained
in two steps using the method of Zard and Barton
(Scheme 2).[44] Further steps followed the established route
to b-octasubstituted porphycenes,[45] and started with iodina-
tion of 4 to the iodopyrrole 5, which was then converted
into the respective bipyrrole 6 using Ullman coupling. Die-
ster 6 was then saponified and decarboxylated to yield the
a-free bipyrrole 7, which was subsequently formylated (to
give 8) under Vilsmeier conditions. Free base porphycenes
9a,b were then obtained by subjecting precursors 8a,b to
McMurry coupling. Subsequent metal insertion provided the
desired zinc complexes 1a,b.
In the present contribution we describe our efforts to pre-
pare metallomesogens based on porphycene, an artificial
macrocyclic system isomeric with porphyrin. Porphycene,
also known as [18]porphyrin(2.0.2.0), originally synthesized
R
in 1986 by Vogel and co-workers,[43] was the first porphyrin
isomer to be reported in the literature. Subsequent studies
showed that its chemistry and physical properties often
depart in significant ways from those of the parent porphy-
rin macrocycle.[31] One of the key differences involves the
optical signature (porphycenes are blue rather than purple).
This, in turn, has led us to consider that porphycene-based
discotic mesphases could be of interest as potential photo-
diode materials since, at least in principle, they might be ex-
pected to respond to different wavelengths than systems
based on porphyrins. Therefore, we decided to check wheth-
er the porphycene ring meets the structural requirements
necessary for mesophase formation. Toward this end, we
synthesized
two
functionalized
porphycenes
1a,b
(Scheme 1) and explored their phase behavior. Additionally,
two complementary porphyrin systems 2a,b were obtained
as isomeric mixtures and studied in parallel with porphy-
cenes 1a,b. We found that both the porphycene and porphy-
Reduction of pyrroles 4a,b afforded the unstable carbi-
nols 10a,b, which were subjected to silica-catalyzed self-con-
densation,[46] followed by oxidation with DDQ. In analogy
to what has been observed in the case of other acid-cata-
lyzed condensations involving activated pyrroles, this reac-
tion proceeds reversibly in the case of 10a,b, and necessarily
results in “scrambling” of the substitution pattern.[46,47] As a
consequence, the free-base porphyrins 11a,b were obtained
as inseparable mixtures of isomers I–IV (Scheme 3). These
mixtures were then converted into the corresponding zinc
complexes 2a,b, which likewise could not be separated into
the individual components.
Scheme 1.
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Discotic Liquid-Crystalline Materials
FULL PAPER
Scheme 2. Synthesis of Zn porphycenes 1a,b: i) AcONH4; ii) CNCH2COOEt, THF/iPrOH, DBU; iii) I2, NaI, NaHCO3, DCE, H2O, D; iv) 1) Boc2O,
DMAP, CH2Cl2, 2) Cu, toluene, D, 3) 1808C, vacuum; v) KOH, glycol, 2008C; vi) 1) POCl3, DMF/DCE, D, 2) AcONa, H2O, D; vii) TiCl4, Zn, CuCl,
THF, D; viii) Zn(OAc)2, CHCl3, MeOH, D.
A
Table 1. Thermodynamic data for the zinc complexes of porphycenes
and porphyrins.
Compound
Transitional properties[a]
1a
1b
Cr1
{Lam}
207 [34]
Cr2
LCol
Cr
Cr
Colh
Cr
Colr c2mm
223 [39]
I
I
I
I
I
I
I
G
55[b]
ꢁ90 [ꢁ17]
255 [41]
123 [43]
170–200[c]
146 [35]
90 [17]
1a·DMAP
1b·DMAP
1b·nTCNQ
2a
Cr
ꢁ110[b]
2b
[a] Transition temperatures are given in8C, and the corresponding enthal-
py changes are included in square brackets [DH in kJmolꢀ1]. Cr, Cr1, Cr2
refer to phases that are crystalline or solid; Colr and Colh to rectangular
and hexagonal columnar phase, respectively; Lam, lamellar phase; LCol
,
lamello-columnar phase; I, isotropic liquid. [b] Determined from varia-
ble-temperature XRD analyses. [c] Range of clearing points observed for
different batches by POM and XRD.
two phase transitions, at 207 and 2238C, both of which show
good reversibility and display enthalpies exceeding
30 kJmolꢀ1. The high enthalpy value observed for the
second transition provides support for the postulate that the
intermediate phase is not a liquid crystal. Indeed, the phase
showed low fluidity and its XRD pattern was typical of a
crystalline material (cf. Supporting Information). It was
therefore concluded that 1a exhibits temperature-dependent
polymorphism and both of its anisotropic phases are crystal-
line.
Scheme 3. Synthesis of Zn porphyrins 2a,b: i) LiAlH4, THF; ii) 1) silica
gel, CH2Cl2, 2) DDQ; iii) Zn(OAc)2, CHCl3, MeOH, D.
AHCTREUNG
Phase behavior of porphycene complexes: The transitional
properties of compounds 1a,b were investigated using polar-
izing optical microscopy (POM), differential scanning calo-
rimetry (DSC) and X-ray diffraction (XRD). The resulting
temperature data, mainly corresponding to DSC measure-
ments, are summarized in Table 1. Compound 1a exhibits
The phase behavior of compound 1b is more complicated
and was partly elucidated using X-ray diffraction (XRD)
analysis. In its initial form, obtained by evaporation from a
dichloromethane solution, 1b exists as a metastable lamellar
mesophase (Lam) from room temperature up to about
558C. On further heating, the Lam phase transforms into a
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J. L. Sessler et al.
more ordered phase, which was identified as lamello-colum-
nar (LCol) on the basis of XRD, before finally clearing to
produce an isotropic liquid at 908C. When this latter iso-
tropic species is allowed to cool slowly, only the LCol phase
is produced as inferred from XRD analysis. Several DSC
cycles were performed for 1b at different scan rates and
with different intervals between scans. On the basis of these
analyses, it is proposed that the Lam phase (and possibly an-
other unidentified phase) may be recovered from the iso-
tropic liquid phase under certain conditions. Unfortunately,
this interpretation is tentative since the isotropic liquid of
1b is prone to supercooling and the DSC results are not
fully conclusive.
mesogenic meso-tetraarylporphyrins.[27] In the present case,
this smectic-like arrangement can be explained by consider-
ing the conformational flexibility of 1b. Each molecule of
1b adopts a conformation that is not discoid but lath-like,
with the lateral chains stretching in opposite directions (see
also the later discussion of the LCol phase). Furthermore, the
absence of apparent p–p interactions is consistent with
there being little if any translational order within the layer.
As the rotation of the laths within the layer is hindered, the
phase may be referred to as a “biaxial” smectic-like phase.
Phases of this kind (discotic lamellar) have been document-
ed for other discotic systems.[48]
The XRD pattern recorded for 1b at 808C (Figure 1) is
indicative of the formation of a lamello-columnar meso-
phase (LCol), similar to those observed recently for lath-like
perylene diimides[49] and for disc-lath mixtures of phthalo-
cyanines and perylenes.[50] Three sharp reflections, with re-
ciprocal spacings in the ratio 1:2:3, are observed in the
small-angle region at 34.8, 17.5, and 11.55 Š, respectively.
Accordingly, these are assigned as (001), (002), and (003) re-
flections. The presence of these higher order features indi-
cates that the layered structure is very pronounced. Two
broad halos were observed in the wide-angle part, corre-
sponding to the liquid-like order of the molten chains (hch at
4.5 Š) and to the stacking of the flat molecular cores (h0 at
3.5 Š). Additionally, two sharp wide-angle peaks are seen at
4.15 and 4.4 Š that are ascribed to specific interactions be-
tween aromatic cores. These assigned interactions likely cor-
respond to an intermolecular in-plane ordering, such as col-
umnar stacking within the layers (ribbons of columns). Fi-
nally, a number of less intense, but nevertheless sharp reflec-
tions appear in the middle-angle range that could be suc-
cessfully indexed as (h0l) with h=1 and 2and l=0, 1, 2, 3,
and 5 in a monoclinic system. The resulting indexation pro-
vides a very good agreement between the experimental and
calculated reciprocal spacings (Table 2). An additional re-
flection at 8.3 Š was indexed as (020) for reasons given
below. The resulting elementary monoclinic cell has a
volume of ca. 6000 Š3, corresponding to approximately two
molecules of 1b.
The XRD pattern of the 1b Lam phase recorded at 508C
is shown in Figure 1. Two sharp reflections in the small-
angle part at 30.5 and 15.15 Š with a 1:2ratio were observed
and considered indicative of a lamellar structure. Two addi-
tional broad scattering halos were also seen at 4.4 Š (ascri-
bed to the molten chains) and at 8.8 Š (reflecting double
periodicity) that are indicative of a liquid-like phase. For a
smectic phase derived from 1b, a mapped out chain area,
2
Ach, of about 28 Š can be deduced (assuming four chains
on each end of the molecule), in reasonable agreement with
the value expected for the cross-sectional area of a molten
aliphatic chain in a smectic phase.
The absence of features ascribable to offset or face-to-
face stacking interactions, which is remarkable for such
planar molecules, has previously been noticed in the discotic
lamellar phases reported by Ohta et al. for certain related
Based on the comparison of the cell dimensions derived
from XRD with the molecular dimensions of 1b obtained
from molecular modeling, a structural model of the LCol
phase is proposed (Figure 2). As a consequence of the ge-
ometry of the porphycene ring and the substitution pattern
employed, it is proposed that molecules of 1b assume a
lath-like conformation with the alkyl chains aligned parallel
to the long axis of the lath, as in the Lam phase described
above. With the chains fully outstretched, the longer dimen-
sion of 1b becomes ca. 40 Š, comparable to the c lattice
constant of the LCol phase (c=35.4 Š, the chains being
partly molten, and the cores tilted). The LCol phase can
therefore be imagined to form smectic layers parallel to the
ab plane. The next step was to determine how these layers
were packed. This was done as outlined below.
To determine the packing arrangement in 1b at 808C, the
value of the cell constant b was determined based on a
Figure 1. X-ray diffraction pattern obtained for 1b at 508C (top) and
808C (bottom).
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Discotic Liquid-Crystalline Materials
FULL PAPER
Table 2. XRD data for liquid crystalline phases derived from compounds
1 and 2.
[a]
[a,d]
Phase and parameters[d,e]
dexp/Š
00l/hkl/hk[b]
I[c]
dtheo/Š
1b, Lam, 508C
30.5
15.15
8.8
001
002M
h
VS
15.2
br
br
30.4
d=30.5 Š
3
V
mol =3350 Š
2
A
A
mol =110 Š
ch =27.5 Š
4.4
hch
2
1b, LCol, 808C
a=10.42Š
b=16.6 Š
c=35.4 Š
34.8
17.4
11.55
10.25
9.4
001
002
003
100
101
020
VS
M
M
M
M
M
34.8
17.4
11.6
10.25
9.4
b=100.548
3
V
V
cell =6020 Š
mol =3400 Š
8.3
8.2102
8.3
3
W
8.2
Z ꢁ27.15
103
W
7.07
6.95
5.9
5.4
005
006
105
200
VW
VW
W
6.96
5.8
5.3
5.1
W
5.1
4.95
4.7
4.5
201/007
202/106
hch
W
W
VS
S
4.95/4.97
4.7
Figure 2. Proposed packing diagram for the LCol phase of 1b. The Figure
is proportionally scaled, the thickness of the molecules being 3.6 Š. It
should be noted that the aryl rings are not coplanar with the porphycene
core.
4.4
h2
4.15
3.95
h1
h0
W
2b, Colr c2mm, 708C
a=59.4 Š
29.7
20
11
31
22
51
42W
33
71
53
hch
h0
VS
VS
M
W
VW
29.7
26.35
16.4
13.15
11.0
26.35
16.25
13.15
10.9
10.4
8.8
8.1
7.55
4.6
original porphycene[43] (Figure 2). The packing can alterna-
tively be viewed as a combination of tilted columnar stacks
along a, with an antiparallel repeat of columns along b. If
we assume that this repeat is generated by a 21 axis, the
(010) reflections should be systematically absent, a conclu-
sion that agrees with the experiment.
b=29.4 Š
S=1745 Š
2
2
S
V
N
col =872.5 Š
3
mol =3350 Š
col =1
10.45
VW
W
VW
broad
sharp
8.8
8.15
7.55
h=Vmol/Scol =3.83 Š
3.8
Phase behavior of porphyrins 2a,b: In analogy to what was
seen in the case of the porphycene complex 1a, the mixture
of isomeric zinc porphyrins 2a displayed no evidence of
mesomorphic behavior. Rather, it exhibits a single crystal-
line phase which melts to produce an isotropic liquid at
about 1468C. Such behavior stands in contrast to the meso-
morphism originally reported for zinc meso-tetra(p-alkoxy-
phenyl)porphyrins.[21] Subsequent studies revealed that these
compounds were not in fact mesogenic,[52] and that the re-
ported phases were actually crystalline. Moreover, the high
enthalpies and microscopic textures provided for these pre-
viously reported compounds[21] are very similar to those ob-
served for 1a and 2a, neither of which is mesogenic.
1b·nTCNQ, Colh, 1408C
a=28.9 Š
24.94
14.5
12.5
8.15
4.6
10
11
20
h
hch
h0
VS
S
S
broad
broad
sharp
25.01
14.45
12.5
2
S=722.25 Š
3
V
mol =3945 Š (1:1)
d=5.46 Š (1:1)
3
V
mol =7525 Š (2:1)
3.3
d=10.42Š (2:1)
[a] dexp and dtheo are the experimentally measured and theoretical diffrac-
tion spacings, respectively. The distances are given in Š. [b] 00l/hkl/hk
are the Miller indices of the reflections of 1D lamellar, 3D LCol, and 2D
Col phases, respectively. [c] Intensity of the reflections: VS very strong, S
strong, M medium, W weak, VW very weak. Derivation of lattice param-
eters is given in the Experimental Section.
On the other hand, compound 2b forms a liquid crystal-
line phase that is stable at room temperature and clears
above 708C. The X-ray pattern of 2b, recorded at 708C
(Figure 3), is consistent with a centered columnar rectangu-
lar phase Colr where the columns are packed in accord with
an overall c2mm symmetry. The two intense and sharp
small-angle reflections were indexed as the fundamental re-
flections (20) and (11) of a rectangular lattice. The indices
of the remaining higher order reflections (Table 2) were de-
duced from the symmetry relationships of the c2mm plane
group. These latter reflections are accompanied by two
halos, one at 4.6 Š, corresponding to molten alkyl chains,
single reflection at 8.3 Š. At first, this reflection was as-
sumed to be (010). With this assumption, the calculated cell
volume (ꢁ3000 Š3) corresponds to approximately one mol-
ecule of 1b. However, the width of the porphycene core, es-
timated as 13.7 Š, exceeds both the a constant and the pro-
posed value of b. Based on this mismatch, it was concluded
that the reflection at 8.3 Š is in fact (020) and the actual
(010) peak is not observed. The molecules can then be fitted
onto the ab plane according to the “herringbone” packing
pattern typical of aromatic molecules,[51] an alignment that
was actually observed in the crystal structure of Vogelꢁs
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J. L. Sessler et al.
and another at 3.8 Š, ascribed to a stacking of the aromatic
rings. The proposed model of the Colr mesophase is shown
in Figure 4. Molecules of 2b are stacked into columns (1
molecule per columnar slice 3.8 Š thick), and their molecu-
lar planes are tilted with respect to the column axis. The col-
umns then self-organize to produce the final two-dimension-
al centered rectangular lattice.
phyrins.[54–59] In fact, a number of EDA-stabilized liquid crys-
tals are known,[60,61] including ferrimagnetically coupled col-
umnar systems based on a MnIII porphyrin.[62,63] The adduct
1b·nTCNQ was thus prepared. This was done by taking a
solution containing roughly equimolar amounts of 1b and
TCNQ and subjecting it to precipitation from MeOH/
CH2Cl2. The properties of the resulting adduct are strongly
dependent on workup conditions, which is probably a conse-
quence of small variations in the overall complex stoichiom-
etry.
Variable-temperature POM observations showed that
1b·nTCNQ is crystalline from ambient temperature up to
about 1108C. Above this temperature, the material under-
goes a phase transition, eventually yielding a homogeneous
texture consisting of large cylindrical domains (Figure 5).
Figure 3. X-ray diffraction pattern of 2b recorded at 708C.
Figure 5. Polarizing optical microscopy textures of 1b·nTCNQ obtained
by heating the solid powder to 1808C (left image) and by cooling the iso-
tropic melt (right image).
Figure 4. Proposed packing model for the Colr c2mm mesophase of 2b.
Formation and properties of the TCNQ adduct: Of the two
porphycene complexes studied, only 1b exhibits LC phases.
However, the kinetic and thermodynamic stability of these
latter phases is limited. We were, therefore, interested in ex-
ploring whether the mesomorphic behavior of 1b could be
enhanced via the addition of appropriately chosen small
molecules. In one attempt made along these lines, the 1:1
adducts of 1a,b and 4-(dimethylamino)pyridine (DMAP)
were prepared. DMAP was chosen because it is known to
form particularly stable complexes with zinc porphyrins.[53]
In the case of the porphycenes 1a,b, it was reasoned that
the axially bound DMAP ligand would introduce an axial
dipole that could improve the thermal stability of the liquid
crystal phase. While an increase in the melting temperatures
was observed, unfortunately, neither 1a·DMAP nor
1b·DMAP showed any mesomorphic properties.
The phase is fluid and retains its birefringence up to about
2008C, at which point it clears into the isotropic liquid
phase. The clearing process is largely irreversible, a finding
that is considered due to phase separation (1b·nTCNQ
cannot be generated by fusing its components). However, if
the isotropic liquid is cooled immediately after clearing
most of the mesophase is recovered. The resulting texture is
identical with that obtained on heating. However, the pat-
tern only forms locally and is not as uniformly distributed,
showing a mixture of isotropic and birefringent zones.
The XRD pattern recorded for 1b·nTCNQ at 1408C is
shown in Figure 6. It is characterized by the presence of
three sharp small angle X-ray reflections, with reciprocal
pffiffiffi
spacings in the ratio 1: 3:2. These three features are most
readily assigned as the (10), (11), and (20) reflections of a
hexagonal lattice with a parameter a=28.9 Š. The presence
of two broad halos at 4.6 Š (hch) and at 8.15 Š (h) con-
firmed the fluid nature of the mesophase, the former signal
corresponding to the molten chains in liquid-like order. An
additional sharper signal was seen at 3.3 Š (h0), correspond-
ing to the stacking of consecutive aromatic molecules.
Given this lack of success in terms of stabilizing a liquid
crystalline phase, we decided to test the effect of combining
1b with tetracyanoquinodimethane (TCNQ). TCNQ is one
of several electron-deficient cyano compounds that form
electron donor–acceptor (EDA) complexes with metallopor-
6858
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Discotic Liquid-Crystalline Materials
FULL PAPER
Figure 7. Proposed structural model for the mesophase produced by
1b·nTCNQ.
Figure 6. X-ray diffraction pattern obtained for 1b·nTCNQ at 1408C.
Due to purification problems, attempts to determine the
stoichiometry of 1b·nTCNQ were not conclusive. Reported
metalloporphyrin–TCNQ adducts characterized by X-ray
crystallography have either 1:1 or 2:1 stoichiometry.[59] The
1:1 adducts consist of infinite alternating stacks of donor
and acceptor molecules (AD)8, whereas in the 2:1 systems
the stacks are of the form (DAD)8, with two metallopor-
phyrin molecules (D) acting to sandwich one TCNQ mole-
cule (A). Using the column cross-section area determined
by XRD and the estimated molecular volumes, it is possible
to calculate the repeating periodicity along the column (d)
for each stoichiometry (Table 2). The d values obtained for
the 1:1 and 2:1 adducts are 5.46 and 10.42 Š, respectively.
This corresponds to 2.73 and 3.47 Š per aromatic ring. Only
the latter value matches the spacing between aromatic rings
expected for stacked structures of this type. For instance, in
the TCNQ–Cu(octaethylporphyrin) adducts, the p–p distan-
ces were in the range 3.29–3.31 Š.[59] Therefore, the stoichi-
ometry of 1b·nTCNQ can be tentatively assigned as close to
2:1. It is, however, possible that the actual stacking sequence
may be partly disordered, that is, both 2:1 and 1:1 sequences
are randomly interspersed, with only a short-range correla-
tion length.
Figure 8. UV-vis-NIR electronic absorption spectra of 1b (dilute CH2Cl2
solution, c and thin film, g) and 1b·nTCNQ (thin film, a). Spec-
tra were corrected for scattering and normalized to the intensity of the
most intense
Q band. The inset shows the entire spectrum of the
1b·nTCNQ film.
This band, which is absent in the spectrum of 1b, corre-
sponds to a charge transfer (CT) transition between 1b and
TCNQ.[55] When 1b·nTCNQ is dissolved in CH2Cl2 the CT
band is no longer observed, indicating that the EDA interac-
tion is not operative in solution.
Additional insight into the structure of the 1b·nTCNQ
complex came from vibrational spectroscopy. The infrared
spectrum of the adduct contains a series of bands at about
2200 cmꢀ1, which are absent in the spectrum of 1b, and
which correspond to the stretching vibrations of the CN
bond (Figure 9). Variations in the frequency of the CN
Figure 7 shows the proposed model for the 1b·nTCNQ
mesophase. The molecules of 1b and TCNQ form columnar
stacks as described above, which are further organized into
a hexagonal array. As the column diameter (28.9 Š) is
smaller than the diameter of an individual molecule of 1b
(with alkyl substituents fully extended), it is assumed that
the chains are either partly coiled or that these substituents
interdigitate between adjacent columns.
Manifestations of the EDA interaction between 1b and
TCNQ could be observed in the 1b·nTCNQ adduct using
UV/Vis-NIR spectroscopy (Figure 8). Comparison of the
solid-state electronic spectra of 1b and 1b·nTCNQ revealed
qualitative differences in the appearance of porphycene ab-
sorption bands (Soret and Q) indicating that the porphycene
chromophore is affected by the presence of TCNQ. More
importantly, an extremely broad and strongly red-shifted
band (ca. 1200 nm, 8300 cmꢀ1) is observed for 1b·nTCNQ.
Figure 9. Vibrational spectra recorded for 1b (upper trace) and
1b·nTCNQ (lower trace). The region of CN stretching frequencies is ex-
panded.
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6859

J. L. Sessler et al.
stretches are known to be correlated with the degree of
charge transfer (Z) between the donor molecule (here 1b)
and TCNQ.[64] Of the five CN stretching bands observed for
1b·nTCNQ, three correspond to Z values of 0.3, 0.5 and 0.8
(Table 3). The two remaining bands have significantly lower
Experimental Section
General: Ethyl isocyanoacetate (Fluka), 1,8-diazabicyclo[5.4.0]undec-7-
G
ene (DBU, Acros), di-tert-butyl dicarbonate (Acros), copper (99.7%,
dendritic 3 mm, Aldrich) and 4-(dimethylamino)pyridine (DMAP, Al-
drich) were used as received. Tetrahydrofuran, N,N-dimethylformamide
(DMF), and toluene were dried by passing through activated alumina
columns. Other solvents were reagent grade and used as received. Unless
noted otherwise, TLC analyses were performed on analytical silica gel
plates with a fluorescent indicator (Whatman) using 10% ethyl acetate in
hexanes as the mobile phase.
Table 3. CN stretching frequencies and degrees of charge transfer for
1b·nTCNQ and reference compounds.
Compound
TCNQ[c]
ꢁnCN/cmꢀ1[a]
Z[b]
0.0
1.0
0.3
0.5
0.8
Instrumentation and methods: Proton, 13C, and two-dimensional NMR
spectra were measured on Varian Unity Plus (300 MHz for 1H), Varian
Mercury (400 MHz), and Bruker Avance spectrometers (500 MHz).
Unless noted otherwise, all spectra were recorded at room temperature.
2227
2183
2214
2203
2193
2171
2164
K+
A
1b·nTCNQ
Gradient-selected H,13C correlation spectra were recorded with a resolu-
1
tion of 1024 to 2048 in the t1 domain. Chemical shifts were referenced to
residual solvent signals (7.24 ppm for C1HCl3 in CDCl3, 77.0 ppm for
13CDCl3). High-resolution chemical ionization (CI) mass spectra were ob-
tained on a Waters (Micromass) Autospec mass spectrometer and the
low-resolution electrospray ionization (ESI) spectrum was obtained on a
Finnigan LCQ Classic mass spectrometer. Electronic spectra were ob-
tained on a Cary 5000 UV/Vis-NIR spectrophotometer (courtesy of the
Center for Nano- and Molecular Science and Technology at UT Austin).
Elemental analyses were carried out at Midwest Microlab, Indianapolis,
IN (USA). DSC data (30 to 2208C, 10 deg per min) were collected using
a Perkin Elmer DSC 7 calorimeter. DMAP-containing samples were
crimped in airtight pans to reduce the loss of DMAP on heating. Optical
microscopy observations were carried out using an Olympus BX41 polar-
izing microscope equipped with a hot stage (Instec Inc., model HCS402)
and a 4 megapixel CCD camera.
n/a
n/a
[a] CN stretching frequency (in cmꢀ1). [b] Degree of charge transfer cal-
culated using the literature method.[64] [c] Literature data.[64]
frequencies, which would correspond to Z > 1. This appar-
ent discrepancy can, however, be rationalized by assuming
that some of the TCNQ molecules coordinate to the zinc
ion of 1b via a CN group.[57,58] To the extent this takes place,
it is expected to result in an additional lowering of the
stretching frequencies.
XRD analysis: The XRD patterns were obtained with two different ex-
perimental set-ups. In all cases, a linear monochromatic CuKa1 beam (l=
1.5405 Š) was obtained using a sealed-tube generator (900 W) equipped
with a bent quartz monochromator. In the first set-up, the transmission
Guinier geometry was used, whereas a Debye–Scherrer-like geometry
was used in the second experimental set-up. In all cases, the crude
powder was filled in Lindemann capillaries of 1 mm diameter and 10 mm
wall thickness. An initial set of diffraction patterns was recorded on an
image plate; periodicities up to 80 Š can be measured, and the sample
temperature controlled to within Æ0.38C from 20 to 3508C. The second
set of diffraction patterns was recorded with a curved Inel CPS 120 coun-
ter gas-filled detector linked to a data acquisition computer; periodicities
up to 60 Š can be measured, and the sample temperature controlled to
within Æ0.058C from 20 to 2008C. In each case, exposure times were
varied from 1 to 24 h.
Conclusion
In this contribution we have shown for the first time that
the use of porphyrins as the structural basis for mesogenic
materials can be extended to include the quintessential por-
phyrin isomer porphycene. In the context of this work, we
have found that the zinc porphycene 1b is a particularly ver-
satile system. It exhibits two structurally distinct mesophas-
es, a discotic lamellar phase, Lam, and a lamello-columnar
phase, LCol, characterized by three-dimensional translational
order. Such findings stand in marked contrast to what is
seen in the case of the isomeric porphyrin system 2b, which
gives rise to a rectangular columnar phase. We have also
found that porphycene 1b, when combined with the electron
acceptor TCNQ, forms a hexagonal columnar phase Colh
that exhibits improved thermal stability. Porphycene 1b is,
therefore, a novel adaptable system that can act as either a
disc (in the Colh phase) or a lath (in the Lam and LCol
phases). This diversity leads us to suggest that this and other
porphyrin isomers may be further engineered to provide sys-
tems with very different packing geometries. Thus, in a
broader sense, the findings reported herein provide support
for the emerging notion that porphyrin analogues can be
successfully exploited as structural motifs for the design of
new mesogens and metallomesogens. This, in turn, could
spawn new applications for discotic liquid crystals.
Estimation of molecular volumes:[65–67] Molecular volumes Vmol were cal-
culated using the formula:
M
l1NA
Vmol
¼
where M is the molecular weight of the motif, NA is the Avogadro
number, 1 is the volume mass (ꢁ1 gcmꢀ3), and l(T) is a temperature
correction coefficient at the temperature of experiment (T). It is defined
as
VCH ðT0Þ
2
l ¼
VCH ðTÞ
2
where
V
ðTÞ ¼ 26:5616 þ 0:02023 ꢂ T
CH2
is the volume of a methylene group (in Š3) at a given temperature (in
8C), and T0 =258C. (The temperature variation of molecular volume of
the complex is expected to follow the trend determined experimentally
for the methylene group).
6860
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Chem. Eur. J. 2007, 13, 6853 – 6863

Discotic Liquid-Crystalline Materials
FULL PAPER
Derivation of lattice parameters: The dimensions of the monoclinic cell
of the 1b LCol phase were obtained by numerical fitting to the experi-
mental diffraction spacings using the formula
CDCl3): d = 179.87, 149.12, 148.87, 137.46, 129.86, 128.05, 124.64, 123.11,
119.78, 116.01, 113.49, 69.47, 69.24, 31.90, 29.66, 29.60, 29.57, 29.45, 29.35,
29.31, 26.07, 22.70, 14.10, 11.22 ppm; HR-MS (CI+): m/z: calcd for
C64H101N2O6: 993.7660; found: 993.7656 [M+H+].
vffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
u
h2 l2 2hlcosb
General procedure for the synthesis of porphycenes via the McMurry
coupling of diformylbipirroles: In a 250 mL three-necked round-bot-
tomed flask equipped with a reflux condenser and a septum inlet were
placed zinc powder (0.98 mg, 15.1 mmol) and copper(I) chloride (48 mg,
0.48 mmol). The apparatus was filled with argon and oxygen-free tetrahy-
drofuran (50 mL) was introduced through a cannula. Titanium tetrachlor-
ide (0.83 mL, 7.55 mmol) was added dropwise over 30 minutes using a sy-
ringe. The mixture was then heated under reflux for 3 h. Subsequently, a
solution of diformylbipyrrole (0.30 mmol) in oxygen-free tetrahydrofuran
(50 mL) was slowly added to the boiling mixture through a cannula.
After completion of the addition (0.5–1 h), the septum was replaced with
a glass stopper and the reaction mixture was kept under reflux for 12h.
After that time, the mixture was cooled down to room temperature and
then to 08C using an ice bath. Aqueous ammonia (6%, 15 mL) was
added dropwise over 1 h. The reaction mixture was then diluted with di-
chloromethane and filtered through a Celite plug, yielding a fluorescent
yellow-orange filtrate that spontaneously changed color to green-blue
upon contact with air. The plug was washed with more dichloromethane
and the combined organic fractions were dried with anhydrous sodium
sulfate. The solvents were removed under reduced pressure and the
crude product was purified as described below.
u
þ
þ
t
1
dhkl
k2
b2
a2 c2
ac
¼
þ
sin2b
The intracolumnar repeating distance h is calculated directly from the es-
timated molecular volume according to
ZV
h ¼
S
in which Z is the number of molecules (aggregation number) within the
elementary fraction of the column (here Z is chosen equal to 1 as the
molecule is disc-like), and S is the lattice area (columnar cross-section).
For a hexagonal lattice
pffiffi
3
S ¼ a2
2
where
2d10
pffiffi
a ¼
3
3,6,13,16-Tetramethyl-2,7,12,17-tetrakis(4-decyloxyphenyl)porphycene
(9a): From 8a (500 mg, 0.73 mmol). The crude product was purified by
column chromatography (200 mm”35 mm, silica gel, 10% ethyl acetate/
hexanes) and crystallized from dichloromethane/hexane to give a dark
solid. Yield: 195 mg (41%). Rf =0.56 (10% ethyl acetate/hexanes);
1H NMR (300 MHz, CDCl3): d = 9.30 (s, 4H, meso-H), 7.83 (d, 3J=
is the lattice parameter obtained from the XRD analysis.
For the Lam phase: Amol =Vmol/d, Ach =Amol/Nch, where Nch is the number
of chains.
For the Colr phase, the lattice parameters a and b are deduced from the
3
following
mathematical
expression:
a=2d20,
and
1/dhk =
9.0 Hz, 8H, phenyl 2,6-H), 7.24 (d, J=9.0 Hz, 8H, phenyl 3,5-H), 4.16 (t,
pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
ðh2=a2 þ k2=b2Þ, where a, b are the parameters of the Colr phase, S is
3J=6.8 Hz, 8H, decyl a-CH2), 3.61 (s, 12H, pyrrole CH3), 1.91 (m, 8H,
decyl b-CH2), 1.57 (m, 8H, decyl g-CH2), 1.48–1.22 (m, 48H, decyl CH2),
ꢁ1.24 (b, 2H, NH), 0.90 ppm (t, 3J=6.8 Hz, 12H, decyl CH3); 13C NMR
the lattice area, Scol is the columnar cross-section (S=a”b, Scol =1= S).
2
Syntheses of compounds 3–7 have been reported previously.[41]
(75 MHz, CDCl3): d
= 158.75, 143.66, 142.67, 137.51, 133.93, 131.57,
General procedure for the formylation of a,a’-unsubstituted bipyrroles:
In a 50 mL round-bottomed flask equipped with a stirring bar and a
reflux condenser were placed an a-free bipyrrole (2mmol), dry 1,2-di-
chloroethane (DCE, 15 mL) and absolute DMF (15 mL). The mixture
was flushed with argon and cooled to 08C in an ice bath. Distilled POCl3
(0.73 mL, 8 mmol) was added via a syringe within 30 minutes. The mix-
ture was then heated to 608C in an oil bath and stirred for 1 hour. Subse-
quently the mixture was poured into aqueous sodium acetate (13 g per
100 mL of water) and heated to 858C for another hour. After cooling to
room temperature, the mixture was extracted with DCE and then with
dichloromethane. The combined organic extracts were dried using anhy-
drous sodium sulfate, and the solvent was removed on a rotary evapora-
tor. The crude product was purified by flash column chromatography
over silica gel (25% ethyl acetate/hexanes).
128.09, 114.40, 114.33, 113.49, 113.46, 68.24, 31.94, 29.66, 29.50, 29.43,
29.37 (”2), 26.18, 22.71, 17.46, 14.15 ppm, ; HR-MS (ESI+): m/z: calcd
for C88H119N4O4: 1295.9231; found: 1295.9214 [M+H+].
3,6,13,16-Tetramethyl-2,7,12,17-tetrakis(3,4-didecyloxyphenyl)porphycene
(9b): From 8b (428 mg, 0.431 mmol). The crude product was purified
twice by flash column chromatography (250 mm”35 mm, silica gel, 5%
ethyl acetate/hexanes, then 2.5% ethyl acetate/hexanes). Finally, the
product was triturated with hot methanol to give a viscous dark oil with
blue luster. Yield: 137 mg (33%). Rf =0.84 (10% ethyl acetate/hexanes);
1H NMR (300 MHz, CDCl3): d = 9.33 (s, 4H, meso-H), 7.46 (d, 4J=
1.7 Hz, 4H, phenyl 2-H), 7.40 (dd, 4J=1.7 Hz, 3J=8.1 Hz, 4H, phenyl 6-
3
3
H), 7.21 (d, J=8.1 Hz, 4H, phenyl 5-H), 4.20 (t, J=6.8 Hz, 8H, decyl a-
CH2), 4.14 (t, 3J=6.8 Hz, 8H, decyl a-CH2), 3.61 (s, 12H, pyrrole CH3),
1.95 (m, 8H, decyl b-CH2), 1.91 (m, 8H, decyl b-CH2), 1.64–1.17 (m,
56H, decyl CH2), 0.89 (t, 3J=6.8 Hz, 12H, decyl CH3), 0.83 ppm (t, 3J=
6.8 Hz, 12H, decyl CH3), NH signal overlaps with the alkyl region;
13C NMR (126 MHz, CDCl3): d = 148.88, 148.86, 143.94, 142.65, 137.57,
131.60, 128.64, 125.77, 118.56, 113.57, 69.56, 69.45, 31.96, 31.89, 29.72,
29.65, 29.64, 29.57, 29.54, 29.50, 29.48, 29.46, 29.40, 29.34, 26.19, 26.13,
22.72, 22.66, 17.49, 14.14, 14.08 ppm; MS (ESI+): m/z: calcd for
C128H199N4O8: 1920.5; found: 1920.6 [M+H+].
5,5’-Diformyl-3,3’-dimethyl-4,4’-bis(4-decyloxyphenyl)-2,2’-bipyrrole (8a):
From 7a (1.25 g, 2 mmol). Gray powder. Yield: 1.11 (82%). Rf =0.17
1
(20% ethyl acetate/hexanes); H NMR (300 MHz, CDCl3): d = 10.20 (b,
2H, NH), 9.41 (s, 2H, CHO), 7.32 (d, 3J=9.0 Hz, 4H, phenyl 3,5-H), 6.98
(d, 3J=9.0 Hz, 4H, phenyl 2,6-H), 4.00 (t, 3J=6.8 Hz, 4H, a-decyl), 2.18
(s, 6H, pyrrole CH3), 1.81 (m, 4H, b-decyl), 1.47 (m, 4H, g-decyl), 1.38–
1.20 (m, 24H, decyl CH2), 0.87 ppm (t, 3J=6.8 Hz, 6H, decyl CH3);
13C NMR (75 MHz, CDCl3): d = 179.82, 158.98, 137.30, 131.44, 129.87,
128.18, 124.20, 119.81, 114.52, 68.11, 31.90, 29.60, 29.57, 29.41, 29.32 (”2),
29.29, 26.07, 22.68, 14.12 ppm; HR-MS (CI+): m/z: calcd for
C44H60N2O4: 680.4553; found: 680.4564 [M +].
General procedure for the synthesis of b-aryl porphyrins: A suspension
of lithium aluminium hydride (95 mg, 2.5 mmol) in dry tetrahydrofuran
(35 mL) was placed in a 100 mL round-bottomed flask filled with argon
and equipped with a stir bar and a septum inlet. A solution of the 2-
ethoxycarbonyl ester derivative (4a or 4b, 1 mmol) in dry tetrahydrofur-
an (15 mL) was quickly added with stirring. The progress of the reaction
was monitored with thin layer chromatography. When the starting mate-
rial was consumed ethyl acetate (10 mL) was added and the mixture was
poured into aqueous ammonium chloride (50 mL). The mixture was ex-
tracted with dichloromethane, the combined organic extracts were dried
with anhydrous potassium carbonate, and the solvent was removed under
5,5’-Diformyl-3,3’-dimethyl-4,4’-bis(3,4-didecyloxyphenyl)-2,2’-bipyrrole
(8b): From 7b (0.94 mg, 1 mmol). Yield 0.75 g (76%). Rf =0.38 (20%
1
ethyl acetate/hexanes); H NMR (300 MHz, CDCl3): d = 10.07 (brs, 2H,
NH), 9.44 (s, 2H, CHO), 6.98–6.86 (m, 6H, ortho + meta), 4.04 (t, 3J=
6.8 Hz, 4H, decyl a-CH2), 4.01 (t, 3J=6.8 Hz, 4H, decyl a-CH2), 2.19 (s,
6H, pyrrole CH3), 1.90–1.76 (m, 8H, decyl b-CH2), 1.5–1.40 (m, 8H,
decyl g-CH2), 1.40–1.15 (m, 48H, decyl CH2), 0.87 (t, 3J=6.8 Hz, 6H,
3
decyl CH3), 0.85 ppm (t, J=6.8 Hz, 6H, decyl CH3); 13C NMR (75 MHz,
Chem. Eur. J. 2007, 13, 6853 – 6863
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6861

J. L. Sessler et al.
reduced pressure. The resulting unstable carbinol (10a or 10b) was dis-
solved in dry dichloromethane (90 mL) and placed under argon in a
tal analysis for C88H116N4O4Zn: C 77.76, H 8.60, N 4.12; found: C 77.52,
H 8.62, N 4.07.
Compound 2b: 1H NMR (500 MHz, CDCl3, data for isomer I only): d =
10.20 (s, 4H, meso-H), 7.72(d, 4J=2.0 Hz, 4H, phenyl 2-H), 7.67 (dd,
4J=2.0 Hz, 3J=8.2Hz, 4H, phenyl 6-H), 7.35 (d, 3J=8.2Hz, 4H, phenyl
250 mL round-bottomed flask equipped with
a stir bar. Silica gel
(500 mg) was then added and the reaction mixture was protected from
light. After 20 h of stirring at room temperature 2,3-dichloro-5,6-dicyano-
p-benzoquinone (DDQ, 170 mg, 0.75 mmol) was added and the solvent
was removed on a rotary evaporator. The crude product (containing
silica gel) was purified by flash column chromatography (200 mm”
25 mm, silica gel, dichloromethane).
3
3
5-H), 4.27 (t, J=6.8 Hz, 8H, decyl a-CH2), 4.23 (t, J=6.8 Hz, 8H, decyl
a-CH2), 3.59 (s, 12H, pyrrole CH3), 2.01 (m, 8H, decyl b-CH2), 1.96 (m,
8H, decyl b-CH2), 1.69–1.14 (m, 56H, decyl CH2), 0.90 (t, 3J=6.8 Hz,
12H, decyl CH3), 0.81 ppm (t, 3J=6.8 Hz, 12H, decyl CH3); 13C NMR
(126 MHz, CDCl3, data for isomer I only): d = 149.39, 148.99, 148.77,
148.09, 142.45, 137.34, 129.42, 125.03, 118.44, 114.15, 100.88, 69.82, 69.75,
32.22, 32.12, 30.00, 29.93, 29.91, 29.86, 29.85, 29.82, 29.76, 29.74, 29.67,
29.57, 26.51, 26.43, 22.98, 22.89, 14.38, 14.30, 12.75 ppm; UV/Vis (CH2Cl2,
298 K): lmax (log e, e in mꢀ1 cmꢀ1) = 412(5.47), 538 (4.33), 575 nm (4.51);
elemental analysis for C128H196N4O8Zn: C 77.48, H 9.96, N 2.82; found: C
77.86, H 10.38, N 2.44.
Compound 11a (mixture of isomers): From 5b (385 mg, 1 mmol). Yield:
98 mg (30%, two steps). 1H NMR (400 MHz, CDCl3): d = 10.04–10.23
(4H, meso-H), 8.09–7.95 (8H, phenyl 2,6-H), 7.37–7.19 (8H, phenyl 3,5-
H), 4.21–4.08 (8H, decyl a-CH2), 3.67–3.54 (12H, pyrrole CH3), 1.99–
1.87 (8H, decyl b-CH2), 1.64–1.53 (8H, decyl g-CH2), 1.52–1.20 (48H,
decyl CH2), 0.92(t, 12H, decyl CH 3), ꢀ3.46 ppm (b, 2H, NH); HR-MS
(CI+): m/z: calcd for C88H119N4O4: 1295.9231; found: 1295.9214 [M+H+
].
Preparation of DMAP complexes: The zinc(II) porphycene (ca. 20 mmol)
and 4-(N,N-dimethylamino)pyridine (6 mg, ca. 5 equiv) were dissolved in
a mixture of dichloromethane (5 mL) and methanol (5 mL). Dichlorome-
thane was then slowly removed on a rotary evaporator until the entire
product precipitated from the solution. The precipitate was then deca-
nted and dried under vacuum.
Compound 11b (mixture of isomers): From 5b (200 mg, 0.37 mmol).
Yield: 45 mg (26%, two steps). 1H NMR (300 MHz, CDCl3): d = 10.15–
10.29 (4H, meso-H), 7.77–7.29 (12H, phenyl 2,5,6-H), 4.31–4.00 (16H,
decyl a-CH2), 3.74–3.55 (12H, pyrrole Me), 2.06–1.88 (16H, decyl b-
CH2), 1.69–1.12(112H, decyl CH 2), 0.89 (t, 12H, decyl CH3), 0.81 (t,
12H, decyl CH3), ꢀ3.44 ppm (b, 2H, NH); MS (CI+): m/z: calcd for
Compound 1a·DMAP: 1H NMR (400 MHz, CDCl3): d = 9.36 (s, 4H,
3
3
C
C
128H199N4O8: 1920.5; found: 1920 [M+H+]; elemental analysis for
128H198N4O8: C 80.03, H 10.39, N 2.92; found: C 80.05, H 10.36, N 2.92.
meso-H), 7.88 (d, J=7.8 Hz, 8H, phenyl 2,6-H), 7.25 (d, J=7.8 Hz, 8H,
phenyl 3,5-H), 4.64 (d, 3J=6.8 Hz, 2H, pyridine meta-H), 4.17 (t, 3J=
6.3 Hz, 8H, decyl a-CH2), 3.62(s, 12H, pyrrole CH 3), 2.52 (brd, 3J=
6.8 Hz, 2H, pyridine ortho-H), 2.11 (b, 6H, NMe2), 1.93 (m, 8H, decyl b-
General procedure for the ZnII metallation of porphycenes and porphyr-
ins: A free base porphycene or porphyrin (ca. 100 mg) and zinc(II) ace-
tate dihydrate (fivefold molar excess) were dissolved in a mixture of
chloroform (15 mL) and methanol (15 mL). The mixture was heated at
reflux for 1 h and cooled to room temperature. The mixture was washed
with water, the organic phase was dried with anhydrous sodium sulfate,
and the solvents were removed under reduced pressure. Finally the prod-
uct was recrystallized from dichloromethane/methanol. Yields were quan-
titative.
3
CH2), 1.62–1.22 (m, 56H, decyl CH2), 0.90 ppm (t, J=6.8 Hz, 12H, decyl
CH3).
Compound 1b·DMAP: 1H NMR (300 MHz, CDCl3): d = 9.42(s, 4H,
meso-H), 7.53 (b, 4H, phenyl 2-H), 7.46 (ꢁd, phenyl 6-H), 7.23 (d, 4H,
3
phenyl 5-H), 4.79 (b, 2H, pyridine meta-H), 4.22 (t, J=6.8 Hz, 8H, decyl
a-CH2), 4.17 (t, 3J=6.8 Hz, 8H, decyl a-CH2), 3.96 (b, 2H, pyridine
ortho-H), 3.64 (s, 12H, pyrrole CH3), 2.23 (b, 6H, NMe2), 1.96 (m, 8H,
decyl b-CH2), 1.91 (m, 8H, decyl b-CH2), 1.64–1.16 (m, 56H, decyl CH2),
0.90 (t, 3J=6.8 Hz, 12H, decyl CH3), 0.82ppm (t, 3J=6.8 Hz, 12H, decyl
CH3).
Compound 1a: 1H NMR (400 MHz, CDCl3): d = 9.48 (s, 4H, meso-H),
7.88 (d, 3J=9.0 Hz, 8H, phenyl 2,6-H), 7.27 (d, 3J=9.0 Hz, 8H, phenyl
3
3,5-H), 4.18 (t, J=6.8 Hz, 8H, decyl a-CH2), 3.71 (s, 12H, pyrrole CH3),
Preparation of 1b·nTCNQ: A solution of 1b (40 mg, ca. 20 mmol) in di-
chloromethane (10 mL) was combined with tetracyanoquinodimethane
(4.8 mg, 1.2equiv) dissolved in methanol (20 mL). Dichloromethane was
slowly removed on a rotary evaporator (at normal pressure) thereby al-
lowing the porphycene material to precipitate completely. The mother
liquor was carefully removed with a syringe and the resulting precipitate
was dried under vacuum.
1.93 (m, 8H, decyl b-CH2), 1.58 (m, 8H, decyl g-CH2), 1.48–1.25 (m,
48H, decyl CH2), 0.90 ppm (t, 3J=6.8 Hz, 12H, decyl CH3); 13C NMR
(126 MHz, CDCl3): d = 158.69, 146.93, 143.47, 141.64, 133.76, 131.64,
128.94, 114.34, 113.22, 68.26, 31.95, 29.68, 29.63, 29.52, 29.48, 29.38, 26.22,
22.72, 17.03, 14.14 ppm; UV/Vis (CH2Cl2, 298 K): lmax (log e,
e in
mꢀ1 cmꢀ1) = 396 (5.33), 595 (4.47), 642nm (5.04); HR-MS (FAB): m/z:
calcd for C88H116N4O4Zn: 1356.8288; found: 1356.8246 [M +]; elemental
analysis for C88H116N4O4Zn: C 77.76, H 8.60, N 4.12; found: C 77.52, H
8.41, N 4.16.
Compound 1b: 1H NMR (400 MHz, CDCl3): d = 9.59 (s, 4H, meso-H),
7.51 (d, 4J=1.7 Hz, 4H, phenyl 2-H), 7.48 (dd, 4J=1.7, 3J=8.1 Hz, 4H,
phenyl 6-H), 7.25 (d, 3J=8.1 Hz, 4H, phenyl 5-H), 4.22 (t, 3J=6.8 Hz,
8H, decyl a-CH2), 4.14 (t, 3J=6.8 Hz, 8H, decyl a-CH2), 3.75 (s, 12H,
pyrrole CH3), 1.97 (m, 8H, decyl b-CH2), 1.89 (m, 8H, decyl b-CH2),
1.64–1.16 (m, 56H, decyl CH2), 0.90 (t, 3J=6.8 Hz, 12H, decyl CH3),
0.82ppm (t, 3J=6.8 Hz, 12H, decyl CH3); 13C NMR (100 MHz, CDCl3):
Acknowledgements
This work was supported by the US National Science Foundation (grant
no. CHE-0515670 to J.L.S.), CNRS, and the University Louis Pasteur-
Strasbourg, France (financial support to B.D.). Thanks are given to Phil-
lip-Morris USA for supplying the polarizing microscope and the Texas
Materials Institute for allowing use of the differential scanning calorime-
ter. M.S. thanks the University of Wrocław for providing access to an
NMR spectrometer. We also thank Vladimir Roznyatovskiy for his help
in obtaining microanalytical data for compound 11b.
d
= 148.73, 147.22, 143.45, 131.73, 129.47, 69.45, 59.48, 28.26, 31.97,
31.88, 29.74, 29.66 (”2), 29.57 (”2), 29.51 (”2), 29.45, 29.42, 29.34, 26.21,
26.12, 22.73, 22.65, 14.16, 14.08 ppm; UV/Vis (CH2Cl2, 298 K): lmax (log e,
e in mꢀ1 cmꢀ1) = 271 (4.84), 396 (5.29), 594 (4.42), 640 nm (5.03); HR-MS
(CI+): m/z: calcd for
C128H197N4O8Zn: 1982.4423; found: 1982.4414
[M+H+]; elemental analysis for C128H196N4O8Zn: C 77.48, H 9.96, N
2.82; found: C 77.66, H 10.01, N 2.86.
[1] S. Chandrasekhar, B. K. Sadashiva, K. A. Suresh, Pramana 1977, 9,
471–480.
Compound 2a: 1H NMR (400 MHz, CDCl3): d = 9.12–10.06 (4H, meso-
H), 8.08–7.91 (8H, phenyl 2,6-H), 7.42–7.24 (8H, phenyl 3,5-H), 4.29–
4.16 (8H, decyl a-CH2), 3.56–3.19 (12H, pyrrole CH3), 2.05–1.92 (8H,
decyl b-CH2), 1.69–1.57 (8H, decyl g-CH2), 1.52–1.20 (48H, decyl CH2),
0.95–0.87 ppm (t, 12H, decyl CH3); UV/Vis (CH2Cl2, 298 K): lmax (log e,
e in mꢀ1 cmꢀ1) = 411 (5.59), 537 (4.40), 575 nm (4.58); HR-MS (CI+): m/
z: calcd for C88H116N4O4Zn: 1356.8288; found: 1356.8275 [M +]; elemen-
[2] E. Dalcanale in Comprehensive Supramolecular Chemistry, Vol. 10
(Eds.: J. L. Atwood, J. E. D. Davies, D. D. MacNicol, F. Vçgtle, D. N.
Reinhoudt), Pergamon, Oxford 1996, p. pp. 583–635.
[3] N. Boden, B. Movaghar in Handbook of Liquid Crystals, Vol. 2B
(Eds.: D. Demus, J. Goodby, G. W. Gray, H.-W. Spiess, V. Vill),
Wiley-VCH, Weinheim, 1998, pp. 798.
6862
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Chem. Eur. J. 2007, 13, 6853 – 6863

Discotic Liquid-Crystalline Materials
FULL PAPER
[4] R. J. Bushby, O. R. Lozman, Curr. Opin. Colloid Interface Sci. 2002,
7, 343–354.
[37] D. Seidel, V. Lynch, J. L. Sessler, Angew.Chem. 2002, 114, 1480–
1483; Angew. Chem. Int. Ed. 2002, 41, 1422–1424.
´
[5] J. Simon, P. Bassoul, Design of Molecular Materials: Supramolecular
Engineering, Wiley-VCH, Weinheim, 2001.
[38] P. J. Chmielewski, L. Latos-Graz˙ynski, K. Rachlewicz, Chem. Eur. J.
1995, 1, 68–73.
[6] J. Nelson, Science 2001, 293, 1059–1060.
[39] A. Jasat, D. Dolphin, Chem. Rev. 1997, 97, 2267–2340.
[40] J. L. Sessler, W. B. Callaway, S. P. Dudek, R. W. Date, V. Lynch,
D. W. Bruce, Chem. Commun. 2003, 2422–2423.
[7] V. Percec, M. Glodde, T. K. Bera, Y. Miura, I. Shiyanovskaya, K. D.
Singer, V. S. K. Balagurusamy, P. A. Heiney, I. Schnell, A. Rapp, H.-
W. Spiess, S. D. Hudson, H. Duan, Nature 2002, 419, 384–387.
[8] L. Schmidt-Mende, A. Fechtenkçtter, K. Müllen, E. Moons, R. H.
Friend, J. D. MacKenzie, Science 2001, 293, 1119–1122.
[9] J. Y. Kim, A. J. Bard, Chem. Phys. Lett. 2004, 383, 11–15.
[10] M. A. Fox, J. V. Grant, D. Melamed, T. Torimoto, C. Liu, A. J. Bard,
Chem. Mater. 1998, 10, 1771–1776.
´
[41] M. Ste˛pien, B. Donnio, J. L. Sessler, Angew.Chem. 2007, 119, 1453–
1457; Angew. Chem. Int. Ed. 2007, 46, 1431–1435.
[42] J. L. Sessler, W. B. Callaway, S. P. Dudek, R. W. Date, D. W. Bruce,
Inorg. Chem. 2004, 43, 6650–6653.
[43] E. Vogel, M. Kçcher, H. Schmickler, J. Lex, Angew.Chem. 1986, 98,
262–264; Angew. Chem. Int. Ed. Engl. 1986, 25, 257–259.
[44] D. H. R. Barton, J. Kervagoret, S. Z. Zard, Tetrahedron 1990, 46,
7587–7598.
[11] B. A. Gregg, M. A. Fox, A. J. Bard, J. Phys. Chem. 1990, 94, 1586–
1598.
[12] C. Liu, H. Pan, M. A. Fox, A. J. Bard, Science 1993, 261, 897–899.
[13] S. Kumar, Liq.Cryst. 2005, 32, 1089–1113.
[14] M. D. Watson, A. Fechtenkçtter, K. Müllen, Chem. Rev. 2001, 101,
1267–1300.
[15] H. Eichhorn, J. Porphyrins Phthalocyanines 2000, 4, 88–102.
[16] C. A. Hunter, J. K. M. Sanders, J. Am. Chem. Soc. 1990, 112, 5525–
5534.
[17] B. Donnio, D. Guillon, D. W. Bruce, R. Deschenaux, in Comprehen-
sive Coordination Chemistry II: From Biology to Nanotechnology,
Vol. 7 (Eds.: J. A. McCleverty, T. J. Meyer), Elsevier, Oxford 2003,
pp. 357–627.
[45] E. Vogel, P. Koch, X.-L. Hou, J. Lex, M. Lausmann, M. Kisters,
M. A. Aukauloo, P. Richard, R. Guilard, Angew. Chem. 1993, 105,
1670–1673; Angew. Chem. Int. Ed. Engl. 1993, 32, 1600–1604.
[46] N. Ono, K. Maruyama, Chem. Lett. 1989, 1237–1240.
[47] N. Ono, H. Kawamura, M. Bougauchi, K. Maruyama, Tetrahedron
1990, 46, 7483–7496.
[48] B. Alameddine, O. F. Aebischer, W. Amrein, B. Donnio, R. Desche-
naux, D. Guillon, C. Savary, D. Scanu, O. Scheidegger, T. A. Jenny,
Chem. Mater. 2005, 17, 4798–4807.
[49] C. W. Struijk, A. B. Sieval, J. E. J. Dakhorst, M. van Dijk, P. Kimkes,
R. B. M. Koehorst, H. Donker, T. J. Schaafsma, S. J. Picken, A. M.
van de Craats, J. M. Warman, H. Zuilhof, E. J. R. Sudholter, J. Am.
Chem. Soc. 2000, 122, 11057–11066.
[18] J. W. Goodby, P. S. Robinson, B.-K. Teo, P. E. Cladis, Mol. Cryst.
Liq. Cryst. 1980, 56, 303–309.
[19] B. A. Gregg, M. A. Fox, A. J. Bard, J. Chem. Soc. Chem. Commun.
1987, 1134–1135.
[50] G. Zucchi, B. Donnio, Y. H. Geerts, Chem. Mater. 2005, 17, 4273–
4277.
[20] B. A. Gregg, M. A. Fox, A. J. Bard, J. Am. Chem. Soc. 1989, 111,
3024–3029.
[21] S. Kugimiya, M. Takemura, Tetrahedron Lett. 1990, 31, 3157–3160.
[22] Y. Shimizu, M. Miya, A. Nagata, K. Ohta, I. Yamamoto, S. Kusu-
bayashi, Liq. Cryst. 1993, 14, 795–805.
[51] A. Gavezzotti, Acta Crystallogr. Sect. B 1990, 46, 275–283.
[52] Y. Shimizu, M. Miya, A. Nagata, K. Ohta, A. Matsumura, I. Yama-
moto, S. Kusabayashi, Chem. Lett. 1991, 2 5.
[53] K. M. Kadish, L. R. Shiue, R. K. Rhodes, L. A. Bottomley, Inorg.
Chem. 1981, 20, 1274–1277.
[23] A. Nagata, Y. Shimizu, H. Nagamoto, M. Miya, Inorg. Chim. Acta
1995, 238, 169–171.
[54] D. A. Summerville, T. W. Cape, E. D. Johnson, F. Basolo, Inorg.
Chem. 1978, 17, 3297–3300.
[24] L. R. Milgrom, G. Yahioglu, D. W. Bruce, S. Morrone, F. Z. Henari,
W. J. Blau, Adv. Mater. 1997, 9, 313–315.
[25] K. Ohta, N. Yamaguchi, I. Yamamoto, J. Mater. Chem. 1998, 8,
2637–2650.
[55] L. J. Pace, A. Ulman, J. A. Ibers, Inorg. Chem. 1982, 21, 199–207.
[56] D. M. Eichhorn, S. Yang, W. Jarrell, T. F. Baumann, L. S. Beall,
A. J. P. White, D. J. Williams, A. G. M. Barrett, B. M. Hoffman, J.
Chem. Soc. Chem. Commun. 1995, 1703–1704.
[26] B. R. Patel, K. S. Suslick, J. Am. Chem. Soc. 1998, 120, 11802–
11803.
[57] K. Sugiura, K. Ushiroda, M. T. Johnson, J. S. Miller, Y. Sakata, J.
Mater. Chem. 2000, 10, 2507–2514.
[27] K. Ohta, N. Ando, I. Yamamoto, Liq. Cryst. 1999, 26, 663–668.
[28] V. Paganuzzi, P. Guatteri, P. Riccardi, T. Sacchelli, J. Barbera, M.
Costa, E. Dalcanale, Eur. J. Org. Chem. 1999, 1527–1539.
[29] M. Castella, F. López-Calahorra, D. Velasco, H. Finkelmann, Chem.
Commun. 2002, 2348–2349.
[30] T. Sugino, J. Santiago, Y. Shimizu, B. Heinrich, D. Guillon, Liq.
Cryst. 2004, 31, 101–108.
[31] J. L. Sessler, A. Gebauer, E. Vogel, in The Porphyrin Handbook,
Vol. 2 (Eds.: K. M. Kadish, K. M. Smith, R. Guilard), Academic
Press, San Diego, CA 2000, pp. 1–54.
[58] W. Hibbs, A. M. Arif, M. Botoshansky, M. Kaftory, J. S. Miller,
Inorg. Chem. 2003, 42, 2311–2322.
[59] M. M. Olmstead, A. de Bettencourt-Dias, H.-M. Lee, D. Pham,
A. L. Balch, Dalton Trans. 2003, 3227–3232.
[60] F. D. Saeva, G. A. Reynolds, L. Kaszczuk, J. Am. Chem. Soc. 1982,
104, 3524–3525.
[61] K. Praefcke, J. D. Holbrey, J. Inclusion Phenom. Mol. Recognit.
Chem. 1996, 24, 19–41.
[62] K. Griesar, M. A. Athanassopoulou, E. A. Soto Bustamante, Z.
Tomkowicz, A. J. Zaleski, W. Haase, Adv. Mater. 1997, 9, 45–48.
[63] J. P. Hill, T. Sugino, Y. Shimizu, Mol. Cryst. Liq. Cryst. 1999, 332,
119–125.
[32] J. L. Sessler, D. Seidel, Angew.Chem. 2003, 115, 5292–5333; Angew.
Chem. Int. Ed. 2003, 42, 5134–5175.
[33] R. Paolesse, in The Porphyrin Handbook, Vol.
2 (Eds.: K. M.
[64] J. S. Chappell, A. N. Bloch, W. A. Bryden, M. Maxfield, T. O. Poeh-
ler, D. O. Cowan, J. Am. Chem. Soc. 1981, 103, 2442–2443.
[65] F. Morale, R. W. Date, D. Guillon, D. W. Bruce, R. L. Finn, C.
Wilson, A. J. Blake, N. Schrçder, B. Donnio, Chem. Eur. J. 2003, 9,
2484–2501.
[66] B. Donnio, B. Heinrich, H. Allouchi, J. Kain, S. Diele, D. Guillon,
D. W. Bruce, J. Am. Chem. Soc. 2004, 126, 15258–15268.
[67] D. Guillon, Struct. Bonding (Berlin) 1999, 95, 41–82.
Kadish, K. M. Smith, R. Guilard), Academic Press, San Diego, CA
2000, pp. 201–232.
[34] J. L. Sessler, A. Gebauer, S. J. Weghorn in The Porphyrin Hand-
book, Vol. 2 (Eds.: K. M. Kadish, K. M. Smith, R. Guilard), Aca-
demic Press, San Diego, CA 2000, pp. 55–124.
´
[35] L. Latos-Graz˙ynski in The Porphyrin Handbook, Vol. 2 (Eds.: K. M.
Kadish, K. M. Smith, R. Guilard), Academic Press, New York 2000,
pp. 361–416.
[36] T. D. Lash, in The Porphyrin Handbook, Vol. 2 (Eds.: K. M. Kadish,
K. M. Smith, R. Guilard), Academic Press, San Diego, CA 2000,
pp. 125–199.
Received: January 24, 2007
Published online: June 14, 2007
Chem. Eur. J. 2007, 13, 6853 – 6863
ꢀ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
6863