Halide effect in electron rich and deficient discotic phthalocyanines

Article abstract of DOI:10.1039/b917169j

A series of discotic octa- and tetra-alkylthio substituted phthalocyanines containing four Cl, Br, I atoms or twelve fluorine atoms have been prepared. All compounds display columnar mesomorphism as confirmed by polarized optical microscopy, thermal analysis, and variable temperature X-ray diffraction. Phthalocyanines containing halide atoms do not crystallize but form glassy or partially crystalline hexagonal columnar phases. Glass transition temperatures increase with increasing size of the halide atoms and with decreasing length of the alkyl chains. In contrast, all octa- and tetra-alkylthio substituted phthalocyanines crystallize and octa-substituted derivatives with aliphatic chain lengths of C_5-7 exhibit tilted (rectangular) columnar mesophases. Cyclic and differential pulse voltammetry, UV-Vis spectroscopy, and quantum chemical calculations at the DFT level have been employed to determine frontier orbital energies of all synthesized and some reference phthalocyanines. Octa- and tetra-alkylthio substituted phthalocyanines are typical p-type semiconductors and the introduction of four Cl, Br, or I atoms lowers frontier orbital energies by only up to 0.1 eV and the optical gap by up to 0.03 eV. A significant decrease in LUMO energy by 0.5 eV to about -4 eV is observed for the fluorinated phthalocyanine, which is a value right at the border of organic n-type semiconductors that may be stable in air.

Full text of DOI:10.1039/b917169j

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PAPER
www.rsc.org/materials | Journal of Materials Chemistry
Halide effect in electron rich and deficient discotic phthalocyanines†‡x
Mohamed Ahmida,a Raymond Larocque,a M. Sharif Ahmed,a Alina Vacaru,a Bertrand Donnio,b Daniel Guillonb
a
*
and S. Holger Eichhorn
Received 19th August 2009, Accepted 12th November 2009
First published as an Advance Article on the web 3rd December 2009
DOI: 10.1039/b917169j
A series of discotic octa- and tetra-alkylthio substituted phthalocyanines containing four Cl, Br, I
atoms or twelve fluorine atoms have been prepared. All compounds display columnar mesomorphism
as confirmed by polarized optical microscopy, thermal analysis, and variable temperature X-ray
diffraction. Phthalocyanines containing halide atoms do not crystallize but form glassy or partially
crystalline hexagonal columnar phases. Glass transition temperatures increase with increasing size of
the halide atoms and with decreasing length of the alkyl chains. In contrast, all octa- and tetra-alkylthio
substituted phthalocyanines crystallize and octa-substituted derivatives with aliphatic chain lengths of
C5–7 exhibit tilted (rectangular) columnar mesophases. Cyclic and differential pulse voltammetry,
UV-Vis spectroscopy, and quantum chemical calculations at the DFT level have been employed to
determine frontier orbital energies of all synthesized and some reference phthalocyanines. Octa- and
tetra-alkylthio substituted phthalocyanines are typical p-type semiconductors and the introduction of
four Cl, Br, or I atoms lowers frontier orbital energies by only up to 0.1 eV and the optical gap by up to
0.03 eV. A significant decrease in LUMO energy by 0.5 eV to about ꢀ4 eV is observed for the
fluorinated phthalocyanine, which is a value right at the border of organic n-type semiconductors that
may be stable in air.
resolved microwave conductivity have been reported for
conventional columnar mesophases of discotic Pcs.10
Introduction
Discotic liquid crystals (DLCs) have been investigated as an
alternative class of organic semiconductors.1 These compounds
may self-organize into columnar stacks that provide high and
anisotropic charge carrier mobilities along the columnar stacks
due to overlapping p-orbital systems.2,3 In addition to efficient
charge transport and the advantages generic to most organic
semiconductors, such as low temperature solution processing
and synthetically adjustable properties, DLCs promise to be
capable of self-healing and can be used in the formation of highly
anisotropic materials.
While charge carrier mobility benefits from the high p–p
stacking forces of Pcs11 these forces are also responsible for the
formation of highly viscous thermotropic columnar mesophases
and strong aggregation in solution. Both properties complicate
processing of columnar mesophases of discotic Pcs into aligned
monodomains that are essential for device applications. More
fluid columnar mesophases of discotic Pcs are usually more
amenable to alignment and techniques such as zone casting,12
surface and confinement directed alignment,9,13,14 and mechan-
ical alignment via intermediate lyotropic mesophases15 have been
successfully applied.
Phthalocyanines (Pcs) have been used as semi- and photo-
conductors for decades because of their exceptional electro-
optical properties and high stability.4,5 Their large discoid
conjugated macrocycle and strong p–p stacking forces make
them ideal building blocks for DLCs.6–9 High ‘‘intrinsic’’ charge
carrier mobilities of 0.2–0.4 cm2 Vꢀ1sꢀ1 measured by time
Crystallization of DLCs is another obstacle for device appli-
cations if major structural rearrangements and polycrystalline
materials of small domain size are generated, as it is the case for
most discotic Pcs. The ‘‘macroscopic’’ charge conduction of
polycrystalline films is drastically diminished because charge
carriers are trapped at grain boundaries between crystalline
domains, although values of ‘‘intrinsic’’ mobility are usually
higher in the crystalline phases than in mesophases since p–p
interactions are less disturbed by molecular motion.10,16,17 An
obvious remedy is the suppression of crystallization by the
formation of anisotropic glasses of hexagonal columnar (Colh)
mesophases or discotic plastic crystal phases that may also
improve mechanical properties and charge conduction.17,18
General approaches to glassy DLCs have been developed but
mostly for triphenylenes. The exchange of one ether linkage in
hexaalkoxy triphenylenes by an ester group suppresses crystal-
lization and has been studied in great detail.19,20 Linking DLCs
together to main-chain oligomers also ensures the formation of
aUniversity of Windsor, Dept. of Chemistry and Biochemistry, Windsor,
Ontario, Canada N9B 3P4. E-mail: eichhorn@uwindsor.ca; Fax: +1 519
973 7098; Tel: +1 519 253 3000 ext 3990
bIPCMS—Organic Materials, 23, rue du Loess, BP 43, F-67034
Strasbourg, Cedex 2, France. E-mail: Daniel.Guillon@ipcms.u-strasbg.fr;
Fax: +33 3 88 10 72 46; Tel: +33 3 88 10 71 47
† Electronic supplementary information (ESI) available: 19F NMR,
polarized optical microscopy, TGA, X-ray diffraction, UV-Vis spectra,
cyclic voltammetry, and DFT calculations. See DOI: 10.1039/b917169j
€
‡ This paper is dedicated to Prof. Dieter Wohrle on the occasion of his
70th birthday.
x This paper is part of a Journal of Materials Chemistry issue highlighting
the work of emerging investigators in materials chemistry.
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glasses but these materials could not be processed into larger
domains of uniform alignment21 with the possible exception of
star-shaped oligomers.22 However, stable glasses are already
formed by dimers of differently substituted triphenylenes and
their columnar mesophases can be uniformly aligned.23 The
examples of discotic Pcs forming anisotropic glasses upon cool-
ing of the preceding columnar mesophases are limited to
derivatives substituted with dendrons24 and mixtures of unsym-
metrically substituted discotic Pcs.25
of only three types of electron deficient discotic Pcs, two are
octa-substituted with p-electron withdrawing carbonyloxy
and sulfonyl groups,29,31 and one is based on the tetrapyr-
azinoporphyrazine core.32
Presented here are the synthesis, mesomorphism and deter-
mination of frontier orbital energies of discotic copper(II)
phthalocyanines (Pcs) 17–27 (Scheme 1) as an extension of our
previous work on alkylthio- and chorine-substituted Pcs.25,36
Introduction of halide atoms resulted in the formation of glassy
hexagonal columnar mesophases (Colh) and tetra-alkyl substi-
tution suppressed the formation of titled columnar mesophases.
Fluorinated Pc 17 has sufficiently low lying frontier orbitals to
function as an n-type discotic material.
Applications of discotic Pcs in electronic devices not only
require optimization of their phase behaviour and alignment but
also their electronic properties such as their frontier orbital
energies. Adjustment of frontier orbital energies permits control
over charge injection at electrode interfaces or between different
organic semiconductors.
Electronic properties of Pcs have been studied in great detail26–28
but few studies, other than on charge conduction, have been
conducted on discotic or potentially discotic Pcs.14,29–32 Pcs are
inherently electron rich p-type semiconductors and this especially
applies to discotic Pcs because most of them are substituted with
p-donating alkyl, alkyloxy, and alkylthio groups. Electron defi-
cient Pcs are sparse and have been prepared by exchanging the
benzene rings with N-heterocycles,28,32,33 by perfluorination of the
macrocycle and attached alkyl groups,28,34 and by the attachment
of p-electron withdrawing sulfonate groups.35 We are aware
Results and discussion
Synthesis
Pcs 17–27 were synthesized according to Scheme 1. Starting
materials 1, 2, and 5 are commercially available; phthalodinitriles
3 and 4 were prepared following literature procedures.37 Phtha-
lodinitriles 7–14 were obtained from 2–5 by nucleophilic substi-
tutions with alkylthiols at 50 ꢁC in the presence of Cs2CO3.
About 10% higher yields were obtained with dimethylimidazo-
lidinone as solvent when compared to DMF under the same
conditions. Mono-substituted phthalodinitriles 7–9 and 11 were
obtained as mixtures with di-substituted phthalodinitriles and
were separated by fractionated crystallization and column
chromatography. All other mono-and di-substituted phthalodi-
nitriles 10 and 12–16 did not contain mixtures of side products
and were purified by column chromatography. Subsequent
cyclization of 7–16 using the established lithium pentanolate
procedure38,39 gave the corresponding Pcs 18–27 in fair yields of
50–60%. Pcs 24–27 were also prepared in the presence of a large
excess of lithium octanolate at 80–90 ꢁC, which increased the
yield by up to 10% in comparison to the lithium pentanolate
procedure but require a reaction time of 3 d instead of 2 h.
Compounds 7, 10, 14, 16, 18, 21, 25 and 27 have been previously
synthesized.25,40–43
Altered conditions wereꢁrequired for the preparation of Pc 17;
1 was substituted at ꢀ10 C to ensure the regioselective substi-
tution at the 4 and 5 positions to give a mixture of mono-
substituted phthalodinitrile 6 and di-substituted phthalodinitrile
that was separated by column chromatography. The 1,2,4-
substitution pattern of 6 was confirmed by 19F and 13C NMR
spectroscopy. Cyclization of 6 in lithium pentanolate produced
a mixture of Pcs containing octylthio and pentyloxy groups
suggesting that fluorine atoms were substituted by pentanolate
groups under these conditions. The amenability of fluorine atoms
of perfluoro Pcs to nucleophilic substitution has been demon-
strated previously.44 Pc 17 was prepared from 6 in a mixture of
ꢁ
quinoline and anhydrous CuCl2 at 180 C in 24% yield.
All Pcs were characterized by UV-Vis and IR spectroscopy as
well as by MALDI-MS and elemental analysis. The results
agreed with the theoretically expected values and in the case of
Pcs 18,25 21,40 2542 and 2725,41 also with reported values. It is
assumed that Pcs 17–23 were formed as statistical mixtures of
four regioisomers but all attempts to verify this by NMR
measurements on metal-free precursors were not successful due
Scheme 1 Reaction conditions: (a) 1.5 eq. RSH, Cs2CO3, dimethylimi-
dazolidinone (DMI) or DMF, 50 ꢁC (2–5) or ꢀ10 ꢁC (1); (b) 2.5 eq. RSH,
Cs2CO3, DMI, 50 ꢁC; (c) 1.4 eq. Li, pentanol, rfl., 2h, Ar followed by 8 eq.
CuAc2, HAc, 60 ꢁC, 1 h for 18–27 or quinoline/1 eq. CuCl2/180 ꢁC for 17.
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to strong aggregation even in solvents such as pyridine and
interfering solvent peaks in the aromatic range. Equally unsuc-
cessful were attempts to separate the isomers of Pc 18 by HPLC
on silica and mixtures of toluene and pyridine as solvent. Some
less aggregating tetra-substituted Pcs have been studied in more
detail and, with few specific exceptions,45 occurred as statistical
mixtures of regioisomers (12.5% C4h-, 25% C2v-, 50% Cs-, and
12.5% D2h-isomer).39,46
decrease in viscosity at 80–100 ꢁC upon heating but these events
do not coincide with their glass transitions determined by DSC,
which occur at much lower temperatures. What is observed by
ꢁ
DSC are slopes in the baseline between 60 and 130 C that may
be caused by weak and broad 2nd-order transitions.
Decomposition temperatures were independently determined
by TGA in He at a heating rate of 2 C minꢀ1. ꢁThe first main
ꢁ
ꢁ
weight loss occurs at temperatures between 290 C and 310 C
for Pcs 18–27 but the onset of weight loss, defined as loss of
0.2 wt%, is at much lower temperatures of 250 ꢁC to 260 ꢁC.
Cleavage of the S–alkyl bond is proposed as the first thermal
decomposition step because typical fragment ions of aliphatic
chains and no halides were observed by simultaneous EI-MS
analysis of the evolved gases. Cleavage of the S–alkyl bond is also
the primary fragmentation in CI-MS.25 The onset of weight loss
of Pc 17 is at 200 ꢁC, which suggests that the S–alkyl bond is
easily cleaved in 17 presumably because of the electron with-
drawing fluorine atoms.
Mesomorphism
All eleven Pcs 17–27 display thermotropic columnar meso-
morphism as well as lyotropic mesomorphism in organic solvents.
Their thermotropic mesomorphism was studied by polarized
optical microscopy (POM), thermal gravimetric analysis (TGA),
differential scanning calorimetry (DSC), and variable tempera-
ture X-ray diffraction (XRD) and is summarized in Fig. 1. Their
lyotropic mesomorphism is not presented here but has previously
been reported for Pcs 18 and 27 as well as related compounds.25,36
Variable temperature POM measurements revealed no
DSC measurements revealed glass transitions for Pcs 18–20
and 22 while Pcs 17, 21, and 23–27 showed melting transitions
(Fig. 1 and 2). The melting transitions of 17, 21 and 23 are broad
and crystallization is suppressed at cooling rates of 5 ꢁC minꢀ1 or
ꢁ
changes to the birefringent textures upon heating from 20 C to
ꢁ
temperatures above 300 C with the exception of melting tran-
ꢁ
faster but proceeds for 17 within several hours at 25 C. Broad
sitions for Pcs 17, 24, 26 and 27. Optically visible decomposition
sets in at about 320 ꢁC for all Pcs but Pc 17 that already
decomposes at about 250 ꢁC. Consequently, no natural defect
textures could be obtained but areas with fan-shaped textures
were observed for all eleven Pcs and are characteristic of
columnar discotic mesophases. Pcs 18, 19, and 20 show a sudden
humps and slopes in the baselines of the DSC curves of Pcs 18–22
suggest additional thermal transitions between 60 ꢁC and 130 ꢁC
that coincide with a decrease in viscosity observed by POM.
However, no coinciding changes are observed in the variable
temperature XRD patterns other than the typical small shifts in
d-spacings with temperature.
Unusually strong is the odd–even effect observed for the
reversible melting temperatures of Pcs 24–27. Pcs 24 and 26 with
odd numbered hydrocarbon chains melt at almost 100 ꢁC higher
temperatures than their even numbered counterparts. We note
that Pc 27 melts at a much higher temperature of 74 ꢁC (onset) in
its first heating run and that Pcs 24–26 show several weak crystal–
crystal transitions that indicate rich crystalline polymorphism.
Interestingly, no systematic odd–even effect was detected in
metal-free and copper(II) octa-alkoxy substituted Pcs.10,47
Phase assignments given in Fig. 1 are based on variable
temperature XRD analysis. Isomer mixtures of Pcs 17–23
Fig. 1 Phase behaviour of Pcs 17–27. Listed are onset temperatures in
ꢁC (DH in kJ molꢀ1) and mid-points of glass transitions measured by
DSC at 5 ꢁC minꢀ1and 10 ꢁC minꢀ1, respectively. Approximate decom-
position temperatures are given as onset of weight loss (ꢀ0.2 wt%)
Fig. 2 DSC curves of Pcs 17–21 on heating at 10 ꢁC minꢀ1 (Tg ¼ glass
transition; Tm ¼ melting transition). The curves were shifted for clarity.
measured by TGA at 2 ꢁC minꢀ1
.
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Table 1 Mesophases and parameters determined by XRD. Tables of all
reflections are provided in the ESI
Other common reflections observed in the diffraction patterns
of Pcs 17–27 are a broad halo at 2q ¼ 19–24ꢁ, indicative of an
amorphous packing of aliphatic side chains, and a reflection of
the intracolumnar p–p stacking at 2q ¼ 25–27ꢁ. The reflection of
the intracolumnar p–p stacking is intense for tetra-alkylthio
substituted Pcs 17–23 but weak and broad for octa-alkylthio
substituted Pcs 24–27, which implies that Pcs 17–23 have a much
higher intracolumnar stacking order than Pcs 24–27. Tetra-
alkylthio substituted Pcs also show shorter stacking distances by
Lattice
parameters/A
Intracolumnar
ꢀ
stacking/A
Compound T/ꢁC Phase
ꢀ
17
25
90
25
25
25
25
25
100
25
130
25
100
25
Colh,crys
Colh
Colh
a ¼ 25.4
a ¼ 26.4
a ¼ 24.4
a ¼ 22.1
3.30
3.31
3.35
3.37
3.41
3.36
3.34
3.35
3.35
3.5
18
19
20
21
22
Colh
Colh,glass a ¼ 25.4
Colh
a ¼ 25.9
ꢀ
up to 0.3 A than octa-alkylthio substituted Pcs.
Colh,glass a ¼ 20.4
The halo of the aliphatic side chains is unusually narrow for Pc
17 at temperatures below its broad melting transition. This
narrowing suggests that partial crystallization of the side chains
occurs and verifies that the phase transition detected by DSC is
indeed that of partially melting/crystallizing side chains. Conse-
quently, the low temperature Colh phase of Pc 17 is labelled
Colh,cryst in contrast to the fully crystalline tilted columnar
phases of Pcs 21 and 24–27. The restricted crystallization of the
side chains in Pc 17 is likely the reason why 17 does not adopt
a tilted columnar phase typical for most crystalline phases of
discotic Pcs.8,6,49
Colh
Colh
Colr
Colr
Colr
Colh
a ¼ 20.8
23
24
25
26
27
a ¼ 20.8
a ¼ 43.4, b ¼ 21.6
a ¼ 45.48, b ¼ 23.28 3.5
a ¼ 47.7, b ¼ 25.5
a ¼ 27.3
3.6
3.5
Diffraction patterns of Pcs 18–20 and 22 contain an additional
broad reflection (halo) at about 2q ¼ 12ꢁ that increases in
intensity with increasing size of the attached halide atoms and is
absent in Pcs 21 and 23. 2D XRD of an aligned sample of Pc 20
reveals that this reflection aligns with the lattice of the 2D
hexagonal columnar phase (Fig. 4a). Consequently, this reflec-
tion likely originates from a periodic lateral (intercolumnar)
packing of halide atoms. This periodic packing must be exclu-
ꢀ
sively intermolecular in nature because the spacing of 7–8 A does
not match any distances between halide atoms within one
molecule of Pcs 18–20 and 22.
Fig. 3 1D-XRD diffraction patterns of Pcs 17–21 and 26 at 25 ꢁC. The
Both intercolumnar and intracolumnar packing distances are
affected by the different halide atoms in Pcs 17–20 as indicated
by the shifting maxima of the (10) and (001) reflections in Fig. 3.
patterns were shifted for clarity.
ꢀ
Unexpectedly, the lattice constant ‘‘a’’ decreases from 26 A to
containing four alkylthio groups all display hexagonal columnar
mesophases (Table 1 and Fig. 3). Diffraction patterns of Pcs 17,
21 and 23 contained the (11) and (20) reflections in addition to
the intense fundamental (10) reflection, which unambiguously
identifies a 2D hexagonal symmetry of the columnar packing. Pcs
18–21 only show the (10) reflection and their hexagonal packing
was verified by 2D XRD measurements along the columnar axis
of shear aligned films that revealed the characteristic hexagonal
pattern (Fig. 4b).48
ꢀ
24 A to 22 A when the size of the halide atoms was increased
ꢀ
ꢀ
from F to Cl to Br, respectively, and then increased again to 25 A
ꢀ
and 26 A for substituents I and H in Pcs 20 and 21, respectively.
The intracolumnar stacking distance slightly increases with
ꢀ
increasing size of halide atoms from 3.30 A in 17 to 3.41 A in 20
ꢀ
ꢀ
ꢀ
and is 3.36 A in 21. The increase in stacking distance of 0.1 A
between Pcs 17 and 20 is much smaller than the difference in van
der Waals radii between F and I of 0.51 A.50 This discrepancy is
ꢀ
likely a result of differences in average mutual rotation angle
between stacked Pc cores although contributions of electronic
differences that alter p–p interactions cannot be excluded.
Differences in average mutual rotation angle may also be the
reason for the unexpected changes in intercolumnar spacing
whereas the observed small differences in stacking distance
should only have a marginal effect on the intercolumnar spacing.
Diffraction patterns of octa-alkylthio substituted Pcs 24–27
confirm the formation of conventional crystal phases as well as
rectangular columnar mesophases for Pcs 24–2651 and a hexag-
onal columnar mesophase for Pc 27. The Patterson symmetry of
the Colrd phases of 25 and 26 is likely c2mm, all observed
reflections obey h + k ¼ 2n, while the symmetry of 24 is p2gg
because of the presence of a (43) reflection (h + k s 2n). Octa-
alkylthio Pcs with longer alkyl chains than octyl have been
Fig. 4 (a) 2D XRD pattern of Pc 20 orthogonal to the aligned columnar
stacks; arrow marks the broad reflection at about 2q ¼ 12ꢁ. (b) 2D XRD
pattern of Pc 18 along the (partially) aligned columnar stacks.
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reported to all form hexagonal columnar mesophases.52
A
change from Colh to Colrd mesophases with decreasing length of
aliphatic chains is common in discotic Pcs5,8,53,54 and other dis-
cotic liquid crystals.55 The high propensity of CuPc to form tilted
columnar stacks may be reasoned with the formation of axial
Cu–N interactions between adjacent macrocycles.49
In contrast, shortening of octyl to pentyl chains in tetra-
alkylthio substituted Pcs 22 and 23 does not induce a tilted
columnar mesophase. A change from octa- to tetra-alkylthio
substitution and likely the presence of a mixture of four isomers
are responsible for the suppression of the formation of tilted
columnar mesophases, but the presence of halide atoms is not
required. Suppression of crystallization in Pcs 18–20, on the
other hand, is specific to the presence of halide atoms because Pcs
21 and 23, that do not contain halide atoms but also are mixtures
of four isomers, do crystallize.
Glass formation in DLCs is associated with restricted rotation
of the discotic molecules about their stacking axis19,56 and this
model is used here for reasoning the observed ‘‘halide-effect’’.
The activation energy for rotation about the stacking axis should
increase with increasing size (van der Waals radius) of the halide
atoms and rotational barriers in Pcs 18–20 are apparently suffi-
ciently high to freeze in molecular motion before crystallization
occurs. The observed short stacking distances and the increase in
glass transition temperatures with increasing size of halide atoms
are consistent with this model.
Fig. 5 Cyclic voltammograms of Pcs 17 (solid line), 18 (dashed line) and
21 (dash doted line) in 0.1 M TBAP–CH2Cl2 solution vs. Ag/Ag+.
Table 2 Half-wave potentials (E1/2, V vs. Ag/AgCl) of Pcs determined by
cyclic voltammetry in CH2Cl2 solution (2–6 ꢂ 10ꢀ5 M, 0.1 M TBAP,
glassy carbon working electrode, scan rate of 0.100 V sꢀ1
)
E1/2 (OX)a/V E1/2 (Red-I)a/V E1/2 (Red-II)a/V DEgapb/V
CuPc vs. Ag/Ag+
vs. Ag/Ag+
vs. Ag/Ag+
(¼ eV)
17
18
19
19c
20
21
26
26c
28
1.47
1.06
1.01
—
0.97
0.85
0.94
—
ꢀ0.38
ꢀ0.80
ꢀ0.88
ꢀ0.76
ꢀ0.87
ꢀ0.99
ꢀ0.91
ꢀ0.79
n.o.d
ꢀ0.65
ꢀ1.08
ꢀ1.01
ꢀ0.97
ꢀ1.19
ꢀ1.27
ꢀ1.15
ꢀ1.09
n.o.d
1.85
1.86
1.89
—
1.84
1.84
1.85
—
Specific halide–halide interactions may also add to the rota-
tional barrier and have been used in crystal engineering.57
However, present models propose 90ꢁ and 180ꢁ angles between
two interacting halide-C groups as ideal geometry,58 which
excludes intracolumnar and suggests intercolumnar halide–
halide interactions as contributors to the rotational barrier. In
ꢀ
fact, the broad reflection at about 7–8 A observed in the XRD
1.85
—
a
b
E1/2 ¼ (Ep,a + Ep,c)/2 at 100 mV sꢀ1
.
DE ¼ E1/2 (first oxidation) ꢀ E1/2
patterns of Pcs 18–20 may be a result of periodic packing due to
intercolumnar halide–halide interactions. A conclusive analysis,
however, requires more detailed experimental and theoretical
studies that are beyond the scope of this work.
c
(first reduction) ¼ HOMO–LUMO gap. Measurement in pyridine
under otherwise identical conditions. The oxidation potentials of 18
and 24 are outside the electrochemical window of pyridine. The first
d
two reduction peaks could not be resolved with certainty presumably
due to strong aggregation. A peak was observed at ꢀ0.84 V by
differential pulse voltammetry and likely is the third reduction step.
Other examples of ‘‘halide effects’’ in DLCs include the
promotion of mesomorphism in discotic triphenylene deriva-
tives. Tribromo-trialkoxy triphenylene displays a hexagonal
columnar mesophase whereas the non-brominated trialkoxy
triphenylene is not mesomorphic.59 However, no glass transitions
but crystallizations have been reported for the more fluid and less
tightly stacked columnar mesophases of tribromo-trialkoxy and
tribromo-trialkylthio triphenylenes.35
Pcs 17–21 and 26 in CH2Cl2 solution show one quasi-reversible
oxidation and two quasi-reversible one-electron reductions in the
covered electrochemical window of ꢀ2.0 V to 2.0 V (Table 2 and
Fig. 5). Pc 28 was quasi-reversibly oxidized but the 1st and 2nd
reduction peaks are too weak and broad to be determined with
certainty presumably because of low solubility and strong
aggregation. A value of ꢀ0.1 V (vs. Ag/AgCl) was reported in the
literature for the 1st reduction potential but no experimental
details were given.60
Electronic properties
Pcs 17–21, 26 and reference compound perfluoro phthalocya-
ninato copper (28 in Fig. 5) were studied by cyclic voltammetry
(CV), UV-Vis spectroscopy and quantum chemical calculations
at the DFT level of theory to determine their frontier orbital
energies and the contributions of the macrocycles to the
frontier orbitals. All Pcs were measured in CH2Cl2 solution at
concentrations of 2–6 ꢂ 10ꢀ5 M and compounds 19 and
26 were also run in pyridine to test for aggregation effects.
Tetrabutylammonium perchlorate (TBAP) at a concentration
of 0.1 M was added as the supportive electrolyte in all
measurements.
The quasi-reversible character of the redox processes was
confirmed by a constant increase of DEp with increasing scan
rates and a DEp larger than 0.059 V (approximately 0.100 V) at
a scan rate of 0.100 V sꢀ1 61
. The peak currents increased linearly
as a function of the square root of scan rates (Ip/n1/2) for scan
rates ranging from 0.050–0.500 V sꢀ1, indicating that the elec-
trode reactions are merely diffusion-controlled for all redox
processes. A diffusion-controlled mass transfer mechanism is
also supported by the fact that peak current ratios (Ipc/Ipa) for all
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processes are approximately unity and do not vary considerably
with scan rates.
CV measurements on copper(II) Pcs are generally not much
affected by aggregation67 but CV curves of Pcs containing other
metal ions may show large changes due to aggregation, such as
the splitting of the first reduction wave into two waves.68
Previous investigations on copper(II) Pcs also established that
oxidations and reductions occur solely on the macrocycle and
not the copper ion.27
Pcs 18–20 and 26 have similar redox potentials while 21 is
easily oxidized and more difficult to reduce by about 0.1 V. Pc 17
is significantly more electron deficient, manifested by a +0.5 V
shift of the oxidation and reduction potentials in comparison to
26. In contrast, the energy gap between oxidation and reduction
potentials is practically constant for all measured compounds
with values between 1.84 V and 1.89 V.
Density functional theory (DFT) calculations were performed
to gain more insight into the electronic properties. The hybrid
density functional UB3LYP69 with LANL2DZ70 basis set was
chosen for both geometry and property calculations in vacuum
because they have been successfully employed in calculations on
other copper(II) Pcs.71 Alkyl groups of Pcs 17–21 and 26 were
replaced by methyl groups for DFT calculations to reduce
computation time. The statistically preferred Cs-isomer (50%)
was chosen for calculations on Pcs 17–21 and 31 that consist of
four different isomers. Comparative calculations on all four
isomers of 18 determined a maximum variation in frontier orbital
energies of 0.3 eV and in HOMO–LUMO gap of 0.13 eV.
Calculated frontier orbital energies of the Cs- and D2h-isomers
Frontier orbital energies of the air stable n-type semiconductor
Pc 28 were determined by CV and optical gap measurements in
solution and are in good agreement with values obtained by
other techniques.62,63 The oxidation potential of discotic Pc 17 is
shifted by ꢀ0.38 V in comparison to Pc 28, which makes Pc 17
a borderline case n-type semiconductor with regard to air
stability.60,64
A comparison of the reduction potential of Pc 17 (ꢀ0.34 V vs.
SCE ¼ Ag/AgCl + 0.045) with reported 1st reduction potentials
of electron deficient octa-carbonyloxy and octa-alkylsulfonyl
substituted
discotic
Pcs31
and
octa(dodecyl)tetrapyr-
azinoporphyrazines32 (ꢀ0.45 V, ꢀ0.14 V and ꢀ0.41 to ꢀ0.55 V
vs. SCE, respectively) places Pc 17 second of the four. However,
replacement of the thioether groups of Pc 17 by p-electron
withdrawing groups (e.g. by oxidation of the thioether to alkyl-
sulfonyl groups) should generate a derivative that is more elec-
tron deficient than Pc 28.
Exchange of four SR groups by I, Br, and Cl (e.g. conversion of
Pc 27 to Pcs 18–20) exerts only minor changes on the redox
potentials despite the differences in electronegativity between S, I,
Br, and Cl. A small systematic change is observed for their
oxidationpotentialsthatincreasefrom0.85Vto1.06Vintheorder
21 < 26 < 20 < 19 < 18. Thelarge shifts in redoxpotentialsobserved
for the fluorinated Pcs 17 and 28 are mainly generated by the
additional F-atoms in 1,4-positions. Comparative DFT calcula-
tionson Pc31 (Fig. 6), the fluorinatedanalogueofPc 18, predict no
significant difference in frontier orbital energies between the two.
Optical HOMO–LUMO gaps were measured by UV-Vis
spectroscopy in pyridine solution. A small but systematic
increase of the gap from 1.67 eV to 1.77 eV in the order 26 < 17 <
18 < 19 < 20 < 21 < 28 was determined. Pyridine was used
because solutions that are optically free of aggregates can be
obtained at concentrations between 10ꢀ5 M and 10ꢀ6 M whereas
solutions of Pcs 17–21 in CH2Cl2 show aggregation at concen-
trations below 10ꢀ6 M. This raises the question whether aggre-
gation altered the redox potentials in the higher concentrated
CH2Cl2 solutions used for CV.
Comparative CV measurements on weakly and strongly
aggregating Pcs 26 and 19, respectively, were conducted in
pyridine (5–6 ꢂ 10ꢀ5 M solutions) to investigate aggregation
effects (Table 2). Both pyridine solutions were optically free of
aggregates and the first reduction potentials of 26 and 19 both
shifted by +0.120 V in comparison to the values obtained in
CH2Cl2. This confirms that differences in aggregation did not
affect the measured redox potentials because 26 was not aggre-
gated and 19 was strongly aggregated in the CH2Cl2 solution
used for CV. A positive shift of the redox potentials is expected
for a change to the donor solvent pyridine65 although negative
shifts have been reported when pyridine strongly coordinates to
the central metal ion of a Pc such as Al.66
Fig. 6 Comparison of EHOMO and ELUMO of Pcs 17–21, 26, 28, and 32
determined by CV in CH2Cl2 solution and calculated at the DFT level
(UB3LYP/LANL2DZ) (top). Chemical structures of Pcs 28–32 (bottom).
Experimental values of 32 were determined by UPS on thin films and
ELUMO of 28 was calculated from EHOMO and the optical gap in pyridine.
EHOMO and ELUMO were calculated from electrochemical measurements
ox
by EHOMO–LUMO (eV) ¼ ꢀ[E1/2 ꢀ (0.48 V)] ꢀ 4.8 eV (0.48 V is the E1/2
of ferrocene/ferrocenium (Fc) vs. Ag/AgCl).
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were 0.2 to 0.3 eV lower than for isomers with C4h and C2v
symmetry.
1,4-positions were studied by comparing octa-fluorinated
2,3-subsituted Pc 29 with 1,4-subsituted Pc 30. The calculated
frontier orbital energies of Pc 29 are in excellent agreement with
experimental values63 and a larger HOMO–LUMO gap but
lower frontier orbital energies are predicted for Pc 29 in
comparison to Pc 30. This result agrees with comparative optical
measurements on other 2,3- and 1,4-substituted Pcs that revealed
always larger gaps for 2,3-susbtituted Pcs.73
A comparison of HOMO and LUMO energies obtained by CV
and DFT calculations is given in Fig. 6. Relative changes of
EHOMO and ELUMO are in good agreement with the values
determined by CV, except for 21, while the absolute values of
measured and calculated frontier orbital energies expectedly
differ by up to 0.6 eV. Calculated orbital energies were generally
lower than the experimental values and differed more for EHOMO
than for ELUMO. No optimization was attempted, e.g. by
including solvent interactions, because our interest is the
prediction of relative changes.
DFT calculations also reveal that the macrocycle and not the
substituents predominantly contributes to the HOMO and
LUMO orbitals in Pcs 17–31, which is important for charge
conduction along discotic columnar stacks because the transfer
integral is less affected by the mutual rotation of stacked
macrocycles.3,53
Values of optical, electrochemical and calculated HOMO–
LUMO gaps are compared in Fig. 7. Relative changes were in
good agreement for all three methods except for compounds 21
and 26. Calculations predict a decrease in gap for 21 in
comparison to 20 but this was not observed experimentally. For
compound 26 calculated and electrochemically measured gaps
are both slightly larger than for 20 but the optical gap is signifi-
cantly lower. The HOMO–LUMO gap of the pigment Pc 32 was
determined on solid films by UV-Vis spectroscopy and by
ultraviolet photoemission spectroscopy (UPS) and are expected
to be lower than values in solution.72
Conclusions
A change from octa-alkylthio to tetra-alkylthio substitution of
discotic Pcs suppresses the formation of tilted columnar phases
for aliphatic chains shorter than C8 and the introduction of
halide atoms (tetra-alkylthio tetra-halide substitution) also
suppresses crystallization. Above room temperature glasses of
hexagonal columnar mesophases are accessible by selecting
larger halides and/or shorter aliphatic chains as exemplified in
Pcs 20 and 22. In contrast, frontier orbital energies and HOMO–
LUMO gaps of the discotic Pcs are little affected by a change
from octa- to tetra-alkylthio substitution and by the introduction
of four Cl, Br, and I atoms. Only the attachment of twelve
F-atoms in Pc 17 significantly lowers frontier orbital energies by
about 0.5 eV. An ELUMO of about ꢀ4.0 eV places Pc 17 at the
border to potentially air stable organic n-type semiconductors
but is 0.38 eV higher than ELUMO of the established n-type
semiconductor perfluoro Pc 28. Derivatives of Pc 17 with an
ELUMO well below ꢀ4.0 eV may be obtained by the replacement
of the thioether groups with electron withdrawing groups such as
alkylsulfonyl. However, the comparatively lower thermal and
chemical stability of Pc 17 may be detrimental to its application
in devices.
All calculated HOMO–LUMO gaps are about 0.2–0.3 eV
higher than the values obtained by CV and the optical gaps are
about 0.2 eV below the electrochemical values. A difference
between calculated and experimental values was expected as
outlined above and the difference between electrochemical and
optical values is in part a solvent effect because the former were
determined in pyridine and the latter in CH2Cl2. A difference in
optical and electrochemical HOMO–LUMO gaps of only
0.02 eV was obtained for Pc 26 when both measurements were
conducted in CH2Cl2.
Calculations of orbital energies for Pcs 18 and 31 predict
a small difference in energies between the tetra-chlorinated and
tetra-fluorinated derivatives as stated earlier. Differences in
frontier orbital energies between halide substitution in 2,3- and
Experimental
Methods
UV-Vis spectra of solutions in THF (spectroscopic grade) were
recorded on a Varian Cary 50 Conc. UV-Visible Spectropho-
1
tometer. H NMR and 13C NMR spectra were run on Bruker
NMR spectrometers (DRX 500 MHz, DPX 300 MHz and DPX
300 MHz with auto-tune). Deuterated chloroform, THF, and
pyridine were used as solvents and their residual proton signals
functioned as reference signals. Multiplicities of the peaks are
given as s ¼ singlet, d ¼ doublet, t ¼ triplet, m ¼ multiplet.
Coupling constants for 1st-order spin systems are given in Hz.
Data are presented in the following order (multiplicity, integra-
tion, coupling constant). Fourier transform infrared spectra (FT-
IR) were obtained on a Bruker Vector 22. Mass spectrometry
measurements were performed by Kirk Green at the Regional
Center for Mass Spectrometry and MALDI-MS data were
obtained on a Waters/Micromass Micro MX. Some MS
measurements were also run on a Finnigan MAT 8222 (DCI),
a Bruker TOF (MALDI), a ZAB2-SE-FDP (FD), and an
Fig. 7 Comparison of HOMO–LUMO gaps of Pcs 17–21, 26, 28 and 32,
measured by CV in CH2Cl2 solution, by UV-Vis spectroscopy in pyridine
and calculated at the DFT level (UB3LYP/LANL2DZ). UPS and optical
values for Pc 32 were taken from Hill and Kahn72 and Zahn et al.,62
respectively.
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ꢀ
Applied Biosystems Voyager DE Pro MALDI-TOF with
a reflector mirror (N2 laser at 337 nm). HPLC separations were
performed on a Merck-Hitachi-System (L-3000 Photo Diode
Array Detector, L-6200A Intelligent Pump, T-6300 Column
Thermostat, AS 2000A Autosampler) equipped with 250-4
Merck LiChrospher Si-60 (10 mm) and LiChrospher RP-18
(5mm) columns.
pentanol were dried over molecular sieve 4 A. Li band was sliced
under Ar and used without removal of its Li oxide layer. All
other solvents, anhydrous CuCl2, Cs2CO3, and alkylthiols were
used without further purification.
4-Octylthio-3,5,6-trifluorobenzene-1,2-dicarbonitrile (6). 5.2 g
(16.0 mmol) Cs2CO3 were added to a solution of 2.33 g
(15.2 mmol) octanethiol and 2.0 g (10.1 mmol) of 1 in 20 mL
DMI under stirring and argon at ꢀ10 ꢁC. The mixture was
Polarized light microscopy was performed on an Olympus
TPM51 polarized light microscope that is equipped with
a Linkam variable temperature stage HCS410 and digital
photographic imaging system (DITO1). Calorimetric studies
were performed on a Mettler Toledo DSC 822e and thermal
gravimetric analysis was performed on a Mettler Toledo TGA
SDTA 851e. Helium (99.99%) was used to purge the system at
a flow rate of 60 mL minꢀ1. Samples were held at 30 ꢁC for 30 min
before heated to 550 ꢁC at a rate of 5 ꢁC minꢀ1. All samples were
run in aluminium crucibles. A Pfeiffer Vacuum ThermostarTM
mass spectrometer (1–300 amu) was attached to the TGA via
a thin glass capillary for evolved gas analysis. XRD measure-
ments were run on a Bruker D8 Discover diffractometer equip-
ped with a Hi-Star area detector and GADDS software package.
The tube is operated at 40 kV and 40 mA and CuKa1 radiation
ꢁ
stirred for 24 h at ꢀ10 C and then poured into 50 mL 0.1 M
aqueous HCl. The product was extracted with DCM (2 ꢂ 30 mL)
and the combined DCM fractions were extracted with 10%
aqueous Na2CO3 solution (2 ꢂ 50 mL), with deionized water (3
ꢂ 50 mL), and dried over MgSO4. Evaporation of the solvent
gave a yellow oil that was a mixture of the 4-octylthio- and
4,5-dioctylthio substituted products. Separation by column
chromatography on RP-18 using acetonitrile as eluent yielded 6
as yellow oil in 41% yield (1.34 g).
IR (as film on KBr): n ¼ 2238 cmꢀ1 (C^N). 1H NMR
(300 MHz, CDCl3): d (ppm) ¼ 3.13 (t, 7.5 Hz, 2H, SCH2), 1.62
(m, 2H, CH2), 1.42 (m, 2H, CH2), 1.27 (m, 8H, CH2), 0.87 (t, 7.2
Hz, 3H, CH3). 13C NMR (300 MHz, CDCl3): d (ppm) ¼ 159.06
(ddd, 259/6/3 Hz, F-Carom.), 153.17 (ddd, 261/13/6.5 Hz, F-
ꢀ
(l ¼ 1.54187 A) with an initial beam diameter of 0.5 mm is used.
Compound 3 was studied as self-supported bulk material and
aligned fibres. Sample detector distances were varied between
15.0 cm and 9.0 cm. A modified Instec hot & cold stage HCS 402
operated via controllers STC 200 and LN2-P (for below ambient
temperatures) was used for variable temperature XRD and IR
measurements.
Carom.), 149.09 (ddd, 266/17/3.5 Hz, F-Carom.), 125.21 (m, arom.),
116.39 (s, CN), 109.21 (d, 11 Hz, CN), 102.91 and 100.24 (m,
arom.), 34.24, 31.73, 29.86, 29.06, 28.94, 28.37, 22.63 (CH2),
14.09 (CH3). 19F NMR (300 MHz, CDCl3): d (ppm) ¼ ꢀ21.01
(dd, 9/11 Hz, Farom), ꢀ37.22 (dd, 9/22 Hz, Farom), 51.27 (dd, 11/
22 Hz, Farom). MS (EI): m/z (%) ¼ 326(19) M+, 214(10)
M+ꢀC8H16, 57(100). C16H17F3N2S (398.31): calculated C, 58.88;
H, 5.25; N, 8.58; found C, 59.10; H, 5.45; N, 8.39%.
Electrochemical measurements were performed using a stan-
dard one-compartment, three-electrode electrochemical cell
connected to an Electrochemical Analyzer BAS 100B/W (Bio-
analytical Systems). The working electrode was a glassy carbon
electrode (3 mm diameter) and was freshly polished and ultra-
sonically rinsed with ethanol before each measurement. Silver
(Ag/0.1 M AgNO3 in CH3CN) and platinum wires were used as
reference and counter electrodes, respectively. Solvents were
obtained from a solvent purification system (Innovative Tech-
nology Inc. MA, USA, Pure-Solv 400) and tetrabutylammonium
perchlorate (TBAClO4) of electrochemical grade was used as
supporting electrolyte (Aldrich). Ferrocene (Fluka) functioned
as internal standard and all measurements were conducted under
dry argon.
4-Octylthio-5-bromobenzene-1,2-dicarbonitrile (8), 4-octylthio-
5-iodobenzene-1,2-dicarbonitrile (9), 4-octylthiobenzene-1,2-
dicarbonitrile (10), 4-pentylthio-5-chlorobenzene-1,2-dicarboni-
trile (11) and 4-pentylthiobenzene-1,2-dicarbonitrile (12). Cs2CO3
(16.0 mmol, 5.20 g) were added to a solution of octanethiol
(15.2 mmol, 2.22 g) or pentanethiol (15.2 mmol, 1.58 g) and
10.1 mmol of 3 (2.88 g), 4 (3.84 g), or 5 (1.75 g) in 20 mL of DMI
under argon. The mixture was stirred for 2 d at 50 ꢁC, cooled to
room temperature, and added to 50 mL 0.1 M aqueous HCl. A
yellow precipitate was filtered off, washed with 10% aqueous
Na2CO3 solution (2 ꢂ 50 mL), with deionized water (3 ꢂ
50 mL), and dried in vacuum. Recrystallization from hexane
gave pale yellow solids. The crude reaction mixtures of 8, 9, and
11 also contained the dialkylthio substituted derivatives in about
DFT calculations were performed with a CAChe WorkSystem
Pro Version 6.1 software (Fujitsu America) and with Gaussian 03
(Gaussian, Inc.: Pittsburgh, PA, 2004).
1
20 mol% according to H NMR. Recrystallization from diiso-
propylether gave fractions of 8, 9, and 11 with a content
>90 mol%, which were further purified by column chromatog-
raphy on silica gel using isopropylether–hexane as eluent. Pure 8,
9, and 11 were isolated as pale yellow solids in 62% (2.18 g), 70%
(2.82 g), and 55% (1.47g), respectively. Compounds 10 and 12
were purified by column chromatography on silica gel using
isopropylether–hexane 1 : 2 as eluent to give the pure products as
white crystalline powders in yields of 84% (2.30 g) and 89%
(2.07 g), respectively.
Synthesis
Tetrafluorobenzene-1,2-dicarbonitrile 1, 4,5-dichlorobenzene-
1,2-dicarbonitrile 2, and 4-nitrobenzene-1,2-dicarbonitrile 5 are
commercially available. 4,5-Dibromobenzene-1,2-dicarbonitrile
3, 4,5-diiodobenzene-1,2-dicarbonitrile 4, 4-octylthio-5-chloro-
benzene-1,2-dicarbonitrile 7, 4,5-dioctylthio-benzene-1,2-dicar-
bonitrile 16, Pc 18 and Pc 27 were synthesized following
procedures described previously. 4-Octylthio-benzene-1,2-dicar-
bonitrile 10, 4,5-dihexylthio-benzene-1,2-dicarbonitrile 14, Pc 21
and Pc 25 have been previously reported but were prepared
by different methods. Dimethylimidazolidinone (DMI) and
Compound 8: mp ¼ 77 ꢁC. IR (as film on KBr): n ¼ 2229 cmꢀ1
1
(C^N). H NMR (300 MHz, CDCl3): d (ppm) ¼ 7.89 (s, 1H,
arom.), 7.40 (s, 1H, arom.), 2.99 (t, 7.4 Hz, 2H, SCH2), 1.78
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(m, 2H, CH2), 1.48 (m, 2H, CH2), 1.34–1.28 (m, 8H, CH2), 0.89
(t, 7.0 Hz, 3H, CH3). 13C NMR (300 MHz, CDCl3): d (ppm) ¼
149.64 (arom.), 136.82 (arom.), 128.70 (arom.), 126.29 (arom.),
115.38 (arom.), 115.29 (arom.), 114.81 (CN), 111.28 (CN), 32.96,
hexane gave pale yellow solids. The crude reaction mixtures of
13, 14, and 15 were purified by column chromatography on silica
gel using isopropylether–hexane mixtures as eluent. Compounds
13, 14, and 15 were obtained as pale yellow solids in yields of 58%
(1.95 g), 64% (2.33 g), and 67% (2.63 g), respectively.
32.12, 29.44, 29.41, 29.30, 27.97, 23.00 (CH2), 14.46 (CH3). MS
+
(EI): m/z (%) ¼ 352(25) M+, 240(24) M+ꢀC8H16, 112(7) C8H16
,
Compound 13: mp ¼ 67 ꢁC. IR (as film on KBr): n ¼ 2229 cmꢀ1
1
43(100). C16H19BrN2S (351.31): calculated C, 54.70; H, 5.45; N,
(C^N). H NMR (300 MHz, CDCl3): d (ppm) ¼ 7.40 (s, 2H,
7.97; found C, 54.59; H, 5.57; N, 7.80%.
Compound 9: mp ¼ 86 ꢁC. IR (as film on KBr): n ¼ 2230 cmꢀ1
arom.), 3.01 (t, 7.2 Hz, 4H, SCH2), 1.75 (m, 4H, CH2), 1.5–1.3
(m, 8H, CH2), 0.92 (t, 7.1 Hz, 6H, CH3). 13C NMR (300 MHz,
CDCl3): d (ppm) ¼ 144.3 (arom.), 128.2 (arom.), 115.8 (arom.),
111.2 (CN), 32.8, 31.1, 27.9, 22.3, 14.0 (CH3). C18H24N2S2
(332.53): calculated C, 65.02; H, 7.27; N, 8.42; found C, 65.09; H,
7.34; N, 8.36%.
1
(C^N). H NMR (300 MHz, CDCl3): d (ppm) ¼ 8.13 (s, 1H,
arom.), 7.33 (s, 1H, arom.), 2.99 (t, 7.3 Hz, 2H, SCH2), 1.79 (m,
2H, CH2), 1.51 (m, 2H, CH2), 1.35–1.28 (m, 8H, CH2), 0.89 (t,
6.7 Hz, 3H, CH3). 13C NMR (300 MHz, CDCl3): d (ppm) ¼
152.96 (arom.), 143.29 (arom.), 127.58 (arom.), 115.95 (arom.),
115.58 (arom.), 114.63 (CN), 111.08 (CN), 101.82 (I-Carom),
34.24, 32.12, 29.44, 29.42, 29.33, 27.89, 23.01 (CH2), 14.48 (CH3).
MS (EI): m/z (%) ¼ 398(66) M+, 286(49) M+ꢀC8H16, 112(8)
C8H16+, 43(100). C16H19IN2S (398.31): calculated C, 48.25; H,
4.81; N, 7.03; found C, 48.43; H, 5.06; N, 6.86%.
Compound 14: mp ¼ 71 ꢁC. IR (as film on KBr): n ¼ 2228 cmꢀ1
1
(C^N). H NMR (300 MHz, CDCl3): d (ppm) ¼ 7.40 (s, 2H,
arom.), 3.01 (t, 7.2 Hz, 4H, SCH2), 1.74 (m, 4H, CH2), 1.48 (m,
4H, CH2), 1.3–1.2 (m, 8H, CH2), 0.89 (t, 6.9 Hz, 6H, CH3). 13C
NMR (300 MHz, CDCl3): d (ppm) ¼ 144.3 (arom.), 128.2
(arom.), 115.8 (arom.), 111.1 (CN), 32.8, 31.4, 28.7, 28.1, 22.6,
14.1 (CH3).
Compound 10: mp ¼ 36 ꢁC. IR (as film on KBr): n ¼ 2228 cmꢀ1
(C^N). 1H NMR (300 MHz, CDCl3): d (ppm) ¼ 7.63 (d, 8.3 Hz,
1H, arom.), 7.55 (d, 2.0 Hz, 1H, arom.), 7.48 (dd, 8.3, 2.0 Hz, 1H,
arom.), 3.00 (t, 7.3 Hz, 2H, SCH2), 1.72 (m, 2H, CH2), 1.46 (m,
Compound 15: mp ¼ 61 ꢁC. IR (as film on KBr): n ¼ 2229 cmꢀ1
1
(C^N). H NMR (300 MHz, CDCl3): d (ppm) ¼ 7.40 (s, 2H,
arom.), 3.01 (t, 7.2 Hz, 4H, SCH2), 1.74 (m, 4H, CH2), 1.48 (m,
4H, CH2), 1.29 (m, 12H, CH2), 0.89 (t, 7.0 Hz, 6H, CH3). 13C
NMR (300 MHz, CDCl3): d (ppm) ¼ 144.3 (arom.), 128.2
(arom.), 115.8 (arom.), 111.1 (CN), 32.8, 31.7, 29.0, 28.9, 28.2,
22.7, 14.2 (CH3). C22H32N2S (388.63): calculated C, 67.99; H,
8.30; N, 7.21; found C, 68.10; H, 8.39; N, 7.16%.
2H, CH2), 1.32–1.28 (m, 8H, CH2), 0.89 (t, 6.7 Hz, 3H, CH3). 13
C
NMR (300 MHz, CDCl3): d (ppm) ¼ 147.92 (arom.), 133.53
(arom.), 130.33 (arom.), 130.21 (arom.), 116.63 (arom.), 115.96
(arom.), 115.59 (CN), 111.01 (CN), 32.26, 32.12, 29.47, 29.40,
29.19, 28.55, 23.00 (CH2), 14.46 (CH3). MS (EI): m/z (%) ¼
272(100) M+, 160(53) M+ꢀC8H16.
ꢁ
Compound 11: mp ¼ 135 C. IR (as film on KBr): n ¼ 2229
Preparation of copper(II)-2,9,16,23 (and 2,10,17,24; 2,10,16,24;
1
cmꢀ1 (C^N). H NMR (300 MHz, CDCl3): d (ppm) ¼ 7.70 (s,
2,9,17,24)-tetraoctylthio-1,3,4,8,10,11,15,17,18,22,24,25
(and
1H, arom.), 7.45 (s, 1H, arom.), 2.99 (t, 8.4 Hz, 2H, SCH2), 1.78
(m, 2H, CH2), 1.58–1.31 (m, 4H, CH2), 0.94 (t, 7.5 Hz, 3H, CH3).
13C NMR (300 MHz, CDCl3): d (ppm) ¼ 147.3 (arom.), 136.0
(arom.), 133.1 (arom.), 128.6 (arom.), 114.8 (arom.), 114.5
(arom.), 114.4 (CN), 110.9 (CN), 31.9, 30.9, 27.3, 22.1 (CH2),
13.8 (CH3). C13H13ClN2S (264.78): calculated C, 58.97; H, 4.95;
N, 10.58; found C, 59.09; H, 5.17; N, 10.36%.
1,3,4,8,9,11,15,16,18,22,23,25; 1,3,4,8,9,11,15,17,18,22,23,25;
1,3,4,8,10,11,15,16,18,22,23,25)-dodecafluorophthalocyaninato
(17). Compound 6 (1.8 mmol, 600 mg), anhydrous CuCl2
(1.8 mmol, 247 mg) and quinoline (3 mL filtered through acti-
vated Al2O3) were added into a glass tube in a glove box. The
glass tube was removed from the glove box, flame sealed, and
heated to 180 ꢁC for 20 h. The reaction mixture was suspended in
toluene (15 mL), extracted with 0.01 M HCl (4 ꢂ 10 mL), washed
with water and dried over MgSO4. The crude product was
further purified by column chromatography on silica gel with
toluene as solvent. The toluene fraction containing the product
was concentrated and 11 was precipitated out by the addition of
acetone to yield 150 mg (0.11 mmol, 24%)
Compound 12: mp ¼ 53 ꢁC. IR (as film on KBr): n ¼ 2228 cmꢀ1
(C^N). 1H NMR (300 MHz, CDCl3): d (ppm) ¼ 7.64 (d, 8.1 Hz,
1H, arom.), 7.55 (d, 1.8 Hz, 1H, arom.), 7.46 (dd, 8.1 Hz, 1.9 Hz,
1H, arom.), 3.01 (t, 7.0 Hz, 2H, SCH2), 1.73 (m, 2H, CH2), 1.49–
1.35 (m, 4H, CH2), 0.93 (t, 7.2 Hz, 3H, CH3). 13C NMR (500
MHz, CDCl3): d (ppm) ¼ 147.6 (arom.), 133.2 (arom.), 130.1
(arom.), 129.9 (arom.), 116.3 (arom.), 115.6 (arom.), 115.2 (CN),
110.7 (CN), 31.9 (CH2), 30.9 (CH2), 27.9 (CH2), 22.2 (CH2), 13.9
(CH3). MS (EI): m/z (%) ¼ 230(100) M+, 160(41) M+ꢀC5H10.
C13H14N2S (230.33): calculated C, 58.97; H, 4.95; N, 10.58;
found C, 58.81; H, 4.99; N, 10.44%.
Compound 17: IR (as film on KBr): n ¼ 1600 cmꢀ1
(C]Carom.). MS (MALDI-TOF, sinapinic acid, positive): m/z ¼
1367 M+. C64H68N8S4F12Cu (1369.07): calculated C, 56.15; H,
5.01; N, 8.18; found C, 56.47; H, 5.18; N, 7.96%.
General synthetic procedure for the preparation of copper(II)-
2,9,16,23 (and 2,10,17,24; 2,10,16,24; 2,9,17,24)-tetrabromo-
3,10,17,24 (and 3,9,16,23; 3,9,17,23; 3,10,16,23)-tetraoctylth-
iophthalocyaninato (19), copper(II)-2,9,16,23 (and 2,10,17,24;
2,10,16,24; 2,9,17,24)-tetraiodo-3,10,17,24 (and 3,9,16,23;
3,9,17,23; 3,10,16,23)-tetraoctylthiophthalocyaninato (20), cop-
per(II)-2,9,16,23 (and 2,10,17,24; 2,10,16,24; 2,9,17,24)-tetraoc-
tylthiophthalocyaninato (21), copper(II)-2,9,16,23 (and 2,10,17,24;
2,10,16,24; 2,9,17,24)-tetrachloro-3,10,17,24 (and 3,9,16,23;
3,9,17,23; 3,10,16,23)-tetrapentylthiophthalocyaninato (22), and
4,5-Dipentylthio-benzene-1,2-dicarbonitrile (13), 4,5-dihex-
ylthio-benzene-1,2-dicarbonitrile (14), 4,5-diheptylthio-benzene-
1,2-dicarbonitrile (15). Cs2CO3 (25.0 mmol, 8.13 g) was added to
a solution of alkylthiol (25.0 mmol) and 2 (10.1 mmol, 2.00 g) in
20 mL of DMI under argon. The mixture was stirred for 2 d at
ꢁ
50 C, cooled to room temperature, and added to 50 mL 0.1 M
aqueous HCl. A yellow precipitate was filtered off, washed with
10% aqueous Na2CO3 solution (2 ꢂ 50 mL), with deionized
water (3 ꢂ 50 mL), and dried in vacuum. Recrystallization from
1300 | J. Mater. Chem., 2010, 20, 1292–1303
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copper(II)-2,9,16,23 (and 2,10,17,24; 2,10,16,24; 2,9,17,24)-tetra-
pentylthiophthalocyaninato (23). Compounds 8, 9, 10, 11 or 12
(2.0 mmol) were dissolved in 20 cm3 of dry 1-pentanol and heated
to reflux under argon. Lithium (2.88 mmol, 20 mg) was added to
the stirred solutions and the reactions were kept under reflux for
m/z ¼ 1391 M+. C72H96N8S8Cu (1393.65): calculated C, 62.05; H,
6.94; N, 8.04; found C, 62.30; H, 7.18; N, 7.79%.
Compound 25: IR (as film on KBr): n ¼ 1600 cmꢀ1
(C]Carom.). MS (MALDI-TOF, sinapinic acid, positive): m/z ¼
1504 M+. C80H112N8S8Cu (1505.86): calculated C, 63.81; H, 7.50;
N, 7.44; found C, 64.00; H, 7.68; N, 7.21%.
2 h and then cooled to 60 C. 30 cm3 of acetic acid were added
ꢁ
and the dark solutions were stirred for 1 h at 60 ꢁC. The
Compound 26: IR (as film on KBr): n ¼ 1598 cmꢀ1
(C]Carom.). MS (MALDI-TOF, sinapinic acid, positive): m/z ¼
1616 M+. C88H128N8S8Cu (1618.08): calculated C, 65.32; H, 7.97;
N, 6.93; found C, 65.54; H, 8.08; N, 6.73%.
ꢁ
suspensions were cooled to 4 C and the precipitated metal-free
Pcs were filtered off. The obtained crude Pcs were metallated in
a solution of copper(II) acetate (about 6 mmol) in THF at 50 ꢁC
for about 5 h. Progress of the metallation was monitored by UV-
Vis spectroscopy. Addition of methanol at rt precipitated the
copper Pcs and they were again precipitated from diethoxy-
methane solution by the addition of acetone. Silica gel flash
chromatography using toluene–n-hexane mixtures as eluent
yielded 19, 20, 21, 22, and 23 in 54% (396 mg), 48% (398 mg), 62%
(357 mg), 55% (308 mg), and 66% (325 mg), respectively.
Compound 19: IR (as film on KBr): n ¼ 1598 cmꢀ1
(C]Carom.). MS (MALDI-TOF, sinapinic acid, positive): m/z ¼
1468 M+. C64H76N8S4Br4Cu (1468.79): calculated C, 52.34; H,
5.22; N, 7.63; found C, 52.70; H, 5.28; N, 7.51%.
Compound 20: IR (as film on KBr): n ¼ 1596 cmꢀ1
(C]Carom.). MS (MALDI-TOF, sinapinic acid, positive): m/z ¼
1656 M+. C64H76N8S4l4Cu (1656.79): calculated C, 46.40; H,
4.62; N, 6.76; found C, 46.54; H, 4.80; N, 6.59%.
Compound 21: IR (as film on KBr): n ¼ 1602 cmꢀ1
(C]Carom.). MS (MALDI-TOF, sinapinic acid, positive): m/z ¼
1153 M+. C64H80N8S4Cu (1153.21): calculated C, 66.66; H, 6.99;
N, 9.72; found C, 67.03; H, 7.08; N, 9.55%.
Acknowledgements
We thank NSERC, OCE, CFI and OIT for financial support as
well as Dr James Gauld (University of Windsor) and his group
members Dr Llano Jorge, Haining Liu, and Eric Bushnell for
their help with the computational studies.
Notes and references
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