Peripheral functionalization of subphthalocyanines

Article abstract of DOI:10.1002/ejoc.200801250

The optimization of synthetic methodologies that lead to novel synthetically and electronically valuable SubPc molecules is of great interest for the use of these molecules in applied fields. In this work, we describe some useful procedures for the incorp

Full text of DOI:10.1002/ejoc.200801250

FULL PAPER
DOI: 10.1002/ejoc.200801250
Peripheral Functionalization of Subphthalocyanines
David González-Rodríguez[a] and Tomás Torres*[a]
Keywords: Subphthalocyanines / Phthalocyanines / Chromophores / Macrocycles / Cross-coupling
The optimization of synthetic methodologies that lead to
novel synthetically and electronically valuable SubPc mole-
cules is of great interest for the use of these molecules in
reactions, have been optimized in order to obtain high yields
and avoid SubPc decomposition. In addition, we report on
the scope of the use of ether functionalities in the condensa-
applied fields. In this work, we describe some useful pro- tion reaction with BCl3 and on the synthesis of a trihydroxy-
cedures for the incorporation of diverse functional groups in
the periphery of the SubPc macrocycle. Different metal-cata-
lyzed cross-coupling reactions, including Stille or Suzuki
couplings and palladium-catalyzed borylation or amination
SubPc, a very valuable compound that could be obtained by
deprotection of a silyloxy-SubPc precursor.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2009)
Introduction
Organic molecular materials enjoy a number of charac-
teristics that make them very attractive for application in
nanoscale optoelectronic devices.[1] Their functional versa-
tility and the possibility of influencing their properties by
modification of the molecular structure have prompted syn-
thetic chemists to investigate novel, reliable and efficient
methods for their functionalization. Key issues for optimal
performance, such as the molecular electronic characteris-
tics, the supramolecular organization, the interaction with
other molecules, or the processability of the bulk material,
can now be controlled to some extent by rational synthetic
design.
Among these organic materials, subphthalocyanines
(SubPcs, Figure 1)[2] are emerging as promising chromo-
phores with potential applications in optical data storage,[3]
nonlinear optics,[4] energy and electron transfer systems,[5]
light-emitting diodes,[6] anion sensing,[7] and supramolec-
ular chemistry.[8] These aromatic macrocycles possess a
singular conical structure[9] imposed by steric factors and
stabilized by the tetrahedral nature of a central boron atom
that, to date, is the only element that has been fitted within
the central cavity. SubPcs are prepared by a condensation
reaction of phthalonitriles in the presence of a boron halide
(usually BCl3),[2,10] which leads to the templated formation
of a three-membered ring, as opposed to other metals that
lead to the more widely known four-membered phthalocy-
anines (Pcs).[11]
Figure 1. Different modes of subphthalocyanine reactivity.
Regarding their functionalization, SubPcs are versatile
molecules whose reactivity can be divided in three different
groups (Figure 1):[2] a) axial reactivity, b) peripheral reactiv-
ity and c) ring expansion reactions. The three of them differ
in the reactive center: a) the axial B–X bond, b) the periph-
eral functional groups on the aromatic carbon atoms, or c)
the imine-type core, respectively. Both axial and peripheral
reactions produce modified SubPcs while ring expansion re-
sults in the loss of the SubPc constrained skeleton and the
formation of low-symmetry Pcs.[12]
[a] Departamento de Química Orgánica, Facultad de Ciencias,
Universidad Autónoma de Madrid,
Cantoblanco, 28049 Madrid, Spain
Fax: +34-91-497-3966
E-mail: tomas.torres@uam.es
Supporting information for this article is available on the
WWW under http://www.eurjoc.org or from the author.
Eur. J. Org. Chem. 2009, 1871–1879
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D. González-Rodríguez, T. Torres
FULL PAPER
Despite the numerous examples in the literature concern- In addition, we report on the scope of the use of ether func-
ing the axial functionalization of SubPcs,[13] the functionali- tionalities in the condensation reaction with BCl3 and on
zation of the peripheral benzene rings have not been yet the synthesis of a trihydroxySubPc, a very valuable com-
developed to the same scope.[14] Quite often, the main prob- pound that could be obtained by cleavage of the silyloxy-
lem encountered in the functionalization of these singular SubPc precursor.
molecules is their chemical instability, which usually leads
to decomposition via ring-opening. Indeed, the constrained
SubPc ring is frequently destroyed in the presence of nu-
cleophiles at high temperatures or in acidic or basic media.
Results and Discussion
In addition, the harsh conditions required for their synthe-
The C3-symmetrical regioisomer of a triiodoSubPc (C3-
sis limit to a great extent the kind of functional groups that 1)[5b] was made to react using diverse cross-coupling meth-
can be introduced in the precursor phthalonitriles, the most odologies (Scheme 1), such as Stille[16] or Suzuki[17] reac-
typical being: halogen atoms, nitro groups, tert-butyl tions and palladium-catalyzed borylation[18] or amin-
groups, thioethers, or sulphones. A good number of func- ation[19] procedures. Compound C3-1 was chosen as the
tional groups, like amines, ethers, sulfoxides,[15] carbonyl de- common starting material in these reactions due to three
rivatives, or unsaturated bonds react rapidly with the boron main reasons: i) iodoarenes are usually the best-suited pre-
reagents employed in SubPc synthesis so their use is most cursors in Pd-catalyzed cross-couplings, ii) the C3-sym-
frequently restricted. The development of novel functionali- metry of the SubPc helped in the monitoring of the reaction
zation approaches of the SubPc core is therefore of utmost and in the characterization of the products, and iii) the ax-
importance, since it will grant a wider functional versatility ial position is protected with a phenoxy group, since chloro-
to these chromophores that could be exploited in several SubPcs were found to be less stable in most of the reaction
applied fields. conditions described hereafter and led quite often to de-
In this work, we describe some useful procedures for the composition products.
incorporation of diverse functional groups in the periphery
Tributylstannane derivatives were found to be appropri-
of the SubPc macrocycle. Different metal-catalyzed cross- ate sources for the introduction of synthetically valuable vi-
coupling reactions were tested as a reasonable continuation nyl and ethynyl moieties via Stille cross-coupling reaction
of the work developed in our group on the coupling of in the presence of (tetrakistriphenylphosphane)palladi-
iodoSubPcs with terminal alkynes.[14,5c] These include the um(II) [Pd(PPh3)4].[20] The reactions were carried out using
well-known Stille or Suzuki couplings and palladium-cata- an excess of the stannane reagent in order to achieve total
lyzed borylation or amination reactions. In many cases, the substitution on each of the three reactive positions. The
typical synthetic procedures for these transformations had 72% and 64% yields obtained for C3-2 and C3-3, respec-
to be modified so that SubPc decomposition was avoided. tively, can be considered quite high, taking into account
Scheme 1. Palladium-catalyzed cross-coupling reactions carried out on triiodoSubPc C3-1.
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Peripheral Functionalization of Subphthalocyanines
that three C–C bonds are being formed. The extension of sensitive functional groups have been reported.[26] These es-
the conjugation in the final products is clearly manifested sentially comprise the addition of crown-ethers[26a] or cer-
in their absorption spectra. Concretely, the Q-band of the tain electron-rich chelating phosphanes,[26c] which allow the
macrocycle experiences a red shift of 13 nm for C3-2 and reaction to take place at room temperature, and the use of
11 nm for C3-3 with respect to C3-1.
milder bases, such as cesium carbonate.[26b] Indeed, it was
For the synthesis of triphenylSubPc C3-4, the use of typi- found that carrying out the reaction in the presence of the
cal Suzuki reaction conditions, namely aqueous carbonate Cs2CO3 base resulted in excellent yields of C3-6 (87%)[5b]
or hydroxide bases in organic solvents such as acetone or and C3-7 (74%). However, this result was, specially for C3-
dimethoxyethane,[17] resulted in the immediate decomposi- 7, rather difficult to reproduce and in some instances the
tion of the macrocycle. Nonetheless, we found that the reaction proceeded very slowly, ultimately leading to the de-
weaker basicity and poorer nucleophilicity of fluoride composition of the macrocycle. It was noted that the rela-
ions[21] respected the structure of the macrocycle, while ef- tive loading ratio of palladium with respect to the chelating
fecting a high-yielding phenyl-phenyl coupling (87%). In phosphane and SubPc C3-1 was determinant for the suc-
view of the high diversity of commercial aryl boronic acids/ cessful formation of C3-6 and C3-7, yielding the best results
esters and their synthetic ease, this mild procedure may be upon addition of 3% Pd2(dba)3 and 3% BINAP ligand per
very practical for the incorporation of a wide range of func- aryl iodide moiety.
tionalities to the SubPc chromophore.
Interestingly, the sequential introduction of the three
Due to our interest in the preparation of synthetic inter- amino groups into the SubPc aromatic ring gives rise to a
mediates which may be employed for the direct carbon–car- spectacular change of the color of the reaction from intense
bon coupling of different active units, the synthesis of pink (C3-1) to blue and, finally, green (C3-6). Intermediate
SubPc C3-5, bearing pinacol boronate groups in the periph- compounds 8 and 9, substituted with one or two di-
eral benzene rings, was as well projected. The most com- phenylamino groups, were isolated as a mixture of regioiso-
mon method for the introduction of boronic acids/esters on mers in the reaction of the C1 regioisomer 1 (C1-1) and
aromatic rings involves the quenching of previously formed 2 equiv. (per SubPc) of the amine (Scheme 2).
aryllithium or magnesium reagents with boronic esters.[17]
SubPcs are destroyed immediately in these conditions and,
for the synthesis of C3-5, a milder procedure was consid-
ered, making use of a reported palladium-catalyzed reac-
tion between diboronic esters and aryl iodides.[18a] We want
to remark that compound C3-5, together with SubPcs C3-2
and C3-3, represent very interesting scaffolds for subsequent
coupling of other units (via Suzuki, Heck or Sonogashira
couplings, respectively) or as monomers in reactions leading
to branched functional polymers.
Finally, since we are interested in modulating the elec-
tronic properties of SubPcs by way of their peripheral func-
tionalization, a suitable method for the introduction of
amine groups into the macrocycle was searched. Direct con-
densation reaction of amino-substituted phthalonitriles in
the presence of BCl3 does not lead, as expected, to any
SubPc product, not even in the case of the poorly basic 4-
diphenylaminophthalonitrile. During the last years, how-
ever, the development of catalytic procedures for carbon–
nitrogen bond formation has been the subject of an intense
research in organometallic chemistry, mainly represented by
the work performed in the groups of Hartwig and Buch-
wald.[19] These kind of amination reactions are commonly
carried out in the presence of palladium complexes with
chelating (BINAP or DPPF, among others)[22] or sterically
encumbered phosphanes (tri-o-tolyl, tri-tert-butyl, biaryl-
phosphanes).[23] For the completion of the catalytic cycle,
a base, usually sodium tert-butoxide, is required.[24] More
recently, the use of copper complexes has represented an
alternative to palladium catalysts in specific cases.[25]
In the first attempts at synthesizing SubPc 6, we observed
that the use of this kind of alkoxide bases in refluxing tolu-
ene produced the decomposition of the macrocycle. Several
alternatives to this general method, compatible with base- 2 equiv. of diphenylamine.
Scheme 2. Products of the amination reaction of SubPc C1-1 with
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UV/Vis experiments showed that the introduction of
each amino group into the macrocycle gave rise to a broad-
ening and a red shift of the SubPc Q-band of about 15 nm,
as well as to the manifestation of new features around
450 nm, which are probably due to n-π* transitions (Fig-
ure 2). These significant changes in the electronic absorp-
tion of these molecules produced a variety of different col-
ors. Thus, SubPcs C1-1, 8, 9 and C1-6 are, respectively, pink,
blue, green-blue and green solids. In diluted solutions, how-
ever, compounds 8 and 9 present dark red colors, similar to
those of thioether-substituted SubPcs.
Scheme 3. Condensation reaction of different ether-substituted
phthalonitriles, leading to SubPcs 10, 13, and 11, 12 (as a statistical
mixture of C3 and C1 regioisomers). a: The condensation reaction
with 3,6-dimethoxyphthalonitrile did not lead to any SubPc mate-
rial. b: Isopropyl ether groups were cleaved during the condensa-
tion reaction, resulting in traces of trihydroxySubPc.
large number of different SubPc products, probably re-
sulting from all the possible cleavages of the ether groups
and their axially hydroxy-substituted analogues produced
in the presence of the silica gel (see below). Only traces of
the corresponding hexaoctyloxySubPc 13 (as identified by
FAB-MS), being the less polar compound in this mixture,
could be isolated.
However, we thought that the idea of employing the bo-
ron halide to perform the condensation reaction and, at the
same time, to completely cleave the ether substituents could
be an entry to trihydroxySubPcs. Therefore, 4-isopro-
Figure 2. Electronic absorption spectra of CHCl3 solutions of
SubPcs C1-1, 8, 9 and C1-6. The Q-band is red-shifted by ca. 15 nm
for each diphenylamino group in the periphery of the SubPc
macrocycle.
As stated in the introduction, the drastic conditions re- poxyphthalonitrile was made to react with an excess of
quired for the synthesis of SubPcs prevents the incorpora- BCl3 forming a product that was not soluble in CH2Cl2 but
tion of a good number of functional groups. Among these, very soluble in methanol. This compound was identified by
ether groups, which have been widely employed in Pc chem- 1H NMR and FAB-MS as the mixture of regioisomers of
istry, are one of the most important. So far, the high ten- trihydroxysubphthalocyanine bearing a hydroxyl group in
dency of boron Lewis acids to cleave ether groups[27] pre- its axial position (due to axial substitution during
cluded the synthesis of oxygen-substituted macrocycles chromatography on silica gel, see below). Nonetheless, the
from alkyloxyphthalonitriles.[28] The magnitude of this oxy- yield was very low (Ͻ1%) and the complete purification of
gen–carbon cleavage is closely related to the tendency of this compound could not be achieved.
this carbon atom to stabilize an eventual positive charge
The sought trihydroxySubPc coud be finally obtained,
[(Alkyl)3C Ͼ (Alkyl)2HC Ͼ (Alkyl)H2C Ͼ CH3 Ͼ Ph].[27a] however, via deprotection reaction of the silyloxy groups in
In order to investigate the applicability of ether function- compound 12. Substitution of the original axial chlorine
alized benzodinitriles in the BCl3-templated formation of atom by a phenoxy group was again essential for the success
SubPcs we made to react different precursors (Scheme 3).
of this synthetic route. On one hand, the purification of the
We found that methoxy-, phenoxy-[5b] and silyloxy- chloroSubPc derivative formed in the condensation reaction
phthalonitriles were robust enough to survive the cyclo- of 4-(tert-butyldimethylsilyloxy)-phthalonitrile with BCl3 by
trimerization reaction conditions and SubPcs 10, 11, 12 column chromatography resulted in poor yields, due to the
could be obtained in moderate to low yields (usually below fast substitution of the axial chlorine atom by an hydroxy
40%). However, the position of these substituents on the group within the silica gel phase. On the other hand, the
starting phthalonitrile was found to be determinant for axial phenoxy ligand acted again as a protecting group dur-
cyclotrimerization. For instance, whereas SubPc 10 could ing the subsequent cleavage of the silyl ether substituents,
be obtained in 21% yield from 4,5-dimethoxyphthalonitrile, where the corresponding chloroSubPc decomposed rapidly.
its 3,6-substituted isomer did not lead to any SubPc prod- Therefore, the phenoxy ligand was introduced just after the
uct. On the other hand, the condensation of 4,5-dioctyl- cyclotrimerization reaction, without isolating the corre-
oxyphthalonitrile did lead to a magenta-coloured material sponding chloroSubPc intermediate, leading to compound
but TLC analysis of the reaction revealed the presence of a 12.
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Peripheral Functionalization of Subphthalocyanines
Several fluoride-mediated deprotection procedures[29]
were applied to SubPc 12, all of them leading to trihydroxy-
SubPc 14 as a mixture of C3 and C1 regioisomers
(Scheme 4).
corded with a Hewlett–Packard 8453 instrument. IR spectra were
recorded on a Bruker Vector 22 spectrophotometer. LSI-MS and
HR-MS spectra were determined on a VG AutoSpec apparatus.
1H and 13C NMR spectra were recorded with a Bruker AC-300
instrument. Elemental analyses were performed with a Perkin–El-
mer 2400 CHN equipment. Elemental analyses were not always
possible to obtain reliably, so the identification of the compound
was made by HR-MS analysis. Column chromatography was car-
ried out on Merck silica gel 60 (230–400 mesh, 60 Å), and TLC on
aluminum sheets precoated with Merck silica gel 60 F254). Chemi-
cals were purchased from commercial suppliers and used without
further purification. 4-Isopropoxyphthalonitrile,[32] 4-phenoxy-
phthalonitrile,[33]
4,5-dimethoxyphthalonitrile,[34]
3,6-dimeth-
oxyphthalonitrile,[35] and 4,5-dioctyloxyphthalonitrile[36] were pre-
pared according to the reported procedures. The synthesis and
characterization of the C3 and C1 regioisomers of SubPcs 1[5b] and
6,[5b] as well as SubPc 11,[37] has been described in the literature.
4-(tert-Butyldimethylsilyloxy)phthalonitrile:
A mixture of 4-hy-
droxyphthalonitrile (1.44 g, 10 mmol) and tert-butyldimethylsilyl
chloride (1.66 g, 11 mmol) was dissolved in THF. To the stirred
solution, triethylamine (5 mL) was slowly added at room tempera-
ture and the mixture was further stirred at that temperature for
16 h.[38] The solvent was then eliminated and the resulting yellowish
oil was subjected to purification by flash column chromatography
on silica gel using a 20:1 mixture of hexane/ethyl acetate as eluent.
It is important to perform this last step as quickly as possible, since
the Si–O bond in the product were found to cleave slowly on silica
gel. 4-(tert-Butyldimethylsilyloxy)phthalonitrile was obtained as a
white solid (2.12 g; 82%); m.p. 45–47 °C. 1H NMR (300 MHz,
CDCl3, 25 °C): δ = 7.67 (d, Jo = 8.8 Hz, 1 H), 7.19 (d, Jm = 1.2 Hz,
1 H), 7.12 (dd, Jo = 8.8 Hz, Jm = 1.2 Hz, 1 H), 0.98 (s, 9 H), 0.27
(s, 6 H) ppm. 13C NMR (75.5 MHz, CDCl3, 25 °C): δ = 159.7,
135.3, 125.0, 124.8, 117.5, 115.6, 106.7, 25.6, 25.4, 18.2 ppm. LSI-
MS (m-NBA): m/z = 258 [M]+ (15%), 201 [M – C(CH3)3]+ (100%).
Scheme 4. Synthesis of trihydroxySubPc 14 (micture of C3 and C1
regioisomers) by deprotection of SubPc 12 using three different
methods (A, B and C).
The reaction between boron trifluoride etherate and 12
in CH2Cl2 (method A, Scheme 4) proceeded very slowly
and only traces of deprotected material were detected after
2 d at room temperature. However, the addition of o-hy- HRLSI-MS (C14H18N2OSi) [M]+: calcd. 258.1188; found 258.1191.
FT-IR (KBr): ν = 2989, 2934, 2888, 2850 (C–H), 2230 (CϵN),
˜
droxybenzaldehyde (method B) greatly accelerates the pro-
cess[30] and SubPc 14 could be obtained in 26% yield after
12 h. In fact, it has been reported that the reaction between
boron trifluoride and salicylaldehide derivatives rapidly
generates a complex that releases hydrofluoric acid, the ac-
tual species that effects the O–Si bond cleavage.[31] The use
of THF solutions of the typical tetrabutylammonium fluo-
ride reagent (method C) resulted in the deprotection of the
silylether groups in similar yields (30%) as method B,
though the reaction rate was higher (3 h at 0 °C). It is im-
portant that the reaction temperature and time do not ex-
ceed these values or otherwise the decomposition of the
SubPc macrocycle starts to compete.
1599, 1486, 1257, 1225 (C–O), 853, 796, 741, 689 cm–1. Elemental
analysis (C14H18N2OSi): calcd. C 65.08, H 7.02, N 10.84; found C
64.27, H 7.65, N 10.34.
4-(Diphenylamino)phthalonitrile: To a stirred suspension of 4-nitro-
phthalonitrile (2.1 g, 12.1 mmol) and dry K2CO3 (2.5 g, 18.1 mmol)
in dry dimethylacetamide (DMAC) (20 mL) was added diphenyl-
amine (2.04 g, 12.1 mmol). The resulting mixture was stirred under
argon at room temperature for 12 h. Subsequently, the mixture was
poured onto 100 mL of cold water and the precipitate was collected
by filtration and subjected to column chromatography on silica gel
using a 1:2 mixture of CH2Cl2/hexane as the eluent. 4-(Di-
phenylamino)phthalonitrile was obtained as a light yellow solid
(3.10 g; 86%). Alternatively, this product can also be prepared via a
Pd-catalyzed amination reaction between 4-iodophthalonitrile and
diphenylamine, following a similar procedure to the one described
below for the amination of SubPcs; m.p. 136–138 °C. 1H NMR
(300 MHz, CDCl3, 25 °C): δ = 7.47 (d, Jo = 8.2 Hz, 1 H), 7.45–
7.35 (m, 5 H), 7.26 (t, JoЈ = 8.0 Hz, 2 H), 7.17 (d, Jo = 8.0 Hz, 4
H), 7.15 (m, 1 H), 7.09 (dd, Jo = 8.2 Hz, Jm = 1.8 Hz, 1 H) ppm.
13C NMR (75.5 MHz, CDCl3, 25 °C): δ = 151.6, 144.4, 134.3,
130.3, 126.6, 126.5, 121.9, 121.1, 116.7, 116.3, 115.6, 104.1 ppm.
Conclusions
In this work we have developed different methodologies
to functionalize the peripheral positions of SubPcs that pre-
serve the structure of the macrocycle. These and other syn-
thetic approaches will certainly be very useful for the em-
ployment of these singular chromophores in applied fields.
LSI-MS (m-NBA): m/z
=
295 [M]+ (100%). HRLSI-MS
(C20H13N3) [M]+: calcd. 295.1109; found 295.1111. FT-IR (KBr):
ν = 3077, 2221 (CϵN), 1595, 1498 (C=C), 1326 (C–N), 1197, 1132,
˜
Experimental Section
817, 751, 716 cm–1.
General Methods: Melting points (m.p.) were determined in a Büchi
Trivinyl-Subphthalocyanine C3-2: A mixture of triiodoSubPc C3-2
504392-S apparatus and are uncorrected. UV/Vis spectra were re-
(43 mg, 0.05 mmol) and Pd(PPh3)4 (8.6 mg, 0.0075 mmol) was
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D. González-Rodríguez, T. Torres
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placed in a 25-mL oven-dried round-bottomed flask. The flask was
purged with argon and dry and deoxygenated toluene (2 mL) was
added. Then, a solution of tributyl(vinyl)tin (0.25 mmol) in dry and
deoxygenated toluene (1 mL) was added through a syringe. The
mixture was then stirred to reflux for 6 h. The solvent was evapo-
rated and the solid residue was thoroughly washed with cold hex-
ane and subjected to column chromatography on silica gel in a
4:1 mixture of hexane/THF. Compound C3-2 was further purified
washing with hexane and methanol, obtaining a dark purple solid
119.1 ppm. LSI-MS (m-NBA): m/z = 716 [M]+ (30%). HRLSI-MS
(C48H29N6OB) [M]+: calcd. 716.2496; found 716.2512. UV/Vis
(CHCl3): λmax [log ε (dm3 mol–1 cm–1)] = 578 (4.5), 527 (sh), 332
(4.4), 288 (4.4) nm. FT-IR (KBr): ν = 3039, 3021 (C–H), 1593,
˜
1469 (C=C), 1300, 1246, 1117, 1047 (B–O), 943, 863, 803, 752, 713,
684 cm–1. Elemental analysis (C24H13BN6O): calcd. C 69.93, H
3.18, N 20.39; found C 69.77, H 3.27, N 20.34.
Tripinacolborate-Subphthalocyanine C3-5: A 10 mL flask, charged
with the palladium catalyst PdCl2(dppf) (2.7 mg, 0.0045 mmol),
KOAc (44 mg, 0.45 mmol), diboronic pinacol ester (46 mg,
0.18 mmol) and subphthalocyanine C3-1 (43 mg, 0.05 mmol), was
flushed with argon. Then, freshly distilled DMSO (3 mL) was
added and the mixture was stirred at 70 °C for 16 h. The product
was extracted with toluene (20 mL), washed with water (2ϫ10 mL)
and dried with anhydrous magnesium sulfate. After filtration and
evaporation, the solid residue was dissolved in cold hexane and
filtered. The solvent was then eliminated at low pressure, obtaining
compound C3-5 as a pink viscous solid (27 mg, 62% yield); m.p. Ͼ
1
(20 mg, 72% yield); m.p. Ͼ 250 °C. H NMR (300 MHz, CDCl3,
25 °C): δ = 8.74 (d, Jm = 1.8 Hz, 3 H), 8.63 (d, Jo = 8.0 Hz, 3 H),
3
3
7.87 (dd, Jo = 8.0 Hz, Jm = 1.8 Hz, 3 H), 6.91 (dd, JE = 17.4, JZ
= 10.9 Hz, 3 H), 6.68 (dd, Jo = JoЈ = 7.6 Hz, 2 H), 6.53 (t, JoЈ
=
3
3
7.6 Hz, 1 H), 5.98 (d, JE = 17.4, 3 H), 5.38 (d, JZ = 10.9, 3 H),
5.34 (d, Jo = 7.6 Hz, 2 H) ppm. 13C NMR (75.5 MHz, CDCl3,
25 °C): δ = 152.5, 151.3, 151.1, 139.5, 136.5, 131.6, 130.0, 128.9,
127.8, 122.2, 121.5, 119.9, 119.1, 116.3 ppm. LSI-MS (m-NBA):
m/z = 566 [M]+ (15%). HRLSI-MS (C36H23N6OB) [M]+: calcd.
566.2026; found 566.2042. UV/Vis (CHCl3): λmax [log ε (dm3 mol–1
cm–1)] = 584 (4.6), 538 (sh), 336 (4.3), 267 (4.3) nm. FT-IR (KBr):
250 °C. 1H NMR (300 MHz, CDCl3, 25 °C): δ = 9.26 (d, Jm
1.8 Hz, 3 H), 8.60 (d, Jo = 8.2 Hz, 3 H), 8.26 (dd, Jo = 8.2 Hz, Jm
= 1.8 Hz, 3 H), 7.08 (dd, Jo = JoЈ = 7.6 Hz, 2 H), 6.80 (t, JoЈ
=
ν = 3065, 3038, 1643 (C=C), 1599, 1540, 1466, 1407, 1355, 1235,
˜
=
1126, 1039 (B–O), 860, 714 cm–1.
7.6 Hz, 1 H), 5.19 (d, Jo = 7.6 Hz, 2 H), 1.18 (s, 36 H) ppm. LSI-
MS (m-NBA): m/z = 866 [M]+ (5%). HRLSI-MS (C48H50B4N6O7)
[M]+: calcd. 866.4113; found 866.4100. UV/Vis (CHCl3): λmax [log
ε (dm3 mol–1 cm–1)] = 575 (4.6), 523 (sh), 322 (4.2), 282 (4.2) nm.
Elemental analysis (C48H50B4N6O7): calcd. C 66.56, H 5.82, N
9.70; found C 66.22, H 5.73, N 9.85.
Triethynyl-Subphthalocyanine C3-3: A mixture of triiodoSubPc C3-
3 (43 mg, 0.05 mmol) and Pd(PPh3)4 (8.6 mg, 0.0075 mmol) was
placed in a 25-mL oven-dried round-bottomed flask. The flask was
purged with argon and dry and deoxygenated toluene (2 mL) was
added. Then, a solution of tributyl(ethynyl)tin (0.22 mmol) in dry
and deoxygenated toluene (1 mL) was added through a syringe.
The mixture was stirred to reflux for 6 h. The solvent was then
evaporated and the solid residue was thoroughly washed with cold
hexane and subjected to column chromatography on silica gel in a
4:1 mixture of hexane/THF. Compound C3-3 was further purified
washing with hexane and methanol, obtaining a dark purple solid
Tricyclohexamine-Subphthalocyanine C3-7: An oven-dried 25 mL
flask was charged with finely ground Cs2CO3 (147 mg, 0.45 mmol),
Pd2(dba)3 (4 mg, 0.0045 mmol), BINAP (2.8 mg, 0.0045 mmol),
freshly distilled piperidine (51 mg, 0.6 mmol) and SubPc C3-1
(43 mg, 0.05 mmol). The flask was then purged with argon and dry
toluene (5 mL) was added through a syringe. The mixture was
heated to reflux under argon atmosphere with continuous stirring
for 8 h. The solution was cooled to room temperature, diluted with
toluene (20 mL), filtered and concentrated to ca. 2–3 mL. The
crude product was then purified by flash chromatography on silica
gel using a 4:1 mixture of hexane/THF as eluent. SubPc C3-7 could
be further purified washing with cold hexane and cold methanol,
obtaining a deep green solid (27 mg, 74% yield); m.p. Ͼ 250 °C.
1H NMR (300 MHz, CDCl3, 25 °C): δ = 8.57 (d, Jo = 8.8 Hz, 3
H), 8.18 (d, Jm = 2.0 Hz, 3 H), 7.43 (dd, Jo = 8.8 Hz, Jm = 2.0 Hz,
3 H), 6.74 (dd, Jo = JoЈ = 7.6 Hz, 2 H), 6.59 (t, JoЈ = 7.6 Hz, 1 H),
5.43 (d, Jo = 7.6 Hz, 2 H), 3.49 (m, 12 H), 1.85–1.40 (m, 18 H)
ppm. LSI-MS (m-NBA): m/z = 737 [M]+ (10%), 644 [M – axial
phenoxy group]+ (20%). HRLSI-MS (C45H44BN9O) [M]+: calcd.
737.3762; found 737.3760. UV/Vis (CHCl3): λmax [log ε (dm3 mol–1
1
(18 mg, 64% yield); m.p. Ͼ 250 °C. H NMR (300 MHz, CDCl3,
25 °C): δ = 8.96 (d, Jm = 1.8 Hz, 3 H), 8.76 (d, Jo = 8.2 Hz, 3 H),
7.99 (dd, Jo = 8.2 Hz, Jm = 1.8 Hz, 3 H), 6.76 (dd, Jo = JoЈ
=
7.6 Hz, 2 H), 6.64 (t, JoЈ = 7.6 Hz, 1 H), 5.37 (d, Jo = 7.6 Hz, 2 H),
3.35 (s, 3 H) ppm. 13C NMR (75.5 MHz, CDCl3, 25 °C): δ = 152.0,
151.0, 150.8, 137.1, 132.1, 131.6, 129.1, 128.7, 123.2, 122.7, 121.3,
118.8, 89.1, 78.2 ppm. LSI-MS (m-NBA): m/z = 560 [M]+ (10%).
HRLSI-MS (C36H17BN6O) [M]+: calcd. 560.1557; found 560.1587.
UV/Vis (CHCl3): λmax [log ε (dm3 mol–1 cm–1)] = 582 (4.5), 531 (sh),
341 (4.2), 277 (4.2) nm. FT-IR (KBr): ν = 3316, 3022 (C–H), 2132
˜
(CϵC), 1613, 1443, 1359, 1232, 1126, 1042 (B–O), 863, 722, 677
cm–1.
Triphenyl-Subphthalocyanine C3-4: A magnetically stirred mixture
of triiodoSubPc C3-1 (43 mg, 0.05 mmol), phenylboric acid (22 mg,
0.18 mmol), Pd(PPh3)4 (8.6 mg, 0.0075 mmol) and powdered CsF
(68 mg, 0.45 mmol) in 4 mL of DME was heated to reflux for 5 h.
After cooling to room temperature, CH2Cl2 (30 mL) was added
and the resulting solution was washed twice with water (10 mL)
and dried with Na2SO4. The drying agent was filtered and the sol-
vent was removed, yielding a dark purple solid that was subjected
to column chromatography on silica gel using a 4:1 mixture of hex-
ane/ethyl acetate. Compound C3-4 was then washed with methanol,
obtaining a dark purple solid (31 mg, 87% yield); m.p. Ͼ 250 °C.
cm–1)] = 621 (4.4), 449 (4.0), 304 (4.2) nm. FT-IR (KBr): ν = 3035,
˜
2967 (C–H), 1601, 1534, 1487, 1466, 1306 (C–N), 1243, 1221, 1107,
1066 (B–O), 903, 751, 697 cm–1.
Procedure for the Synthesis of SubPcs 8 and 9: An oven-dried 25 mL
flask was charged with finely ground Cs2CO3 (147 mg, 0.45 mmol),
Pd2(dba)3 (4 mg, 0.0045 mmol), BINAP (2.8 mg, 0.0045 mmol), di-
phenylamine (39 mg, 0.1 mmol) and SubPc C1-1 (43 mg,
0.05 mmol). The flask was then purged with argon and dry toluene
1H NMR (300 MHz, CDCl3, 25 °C): δ = 9.07 (d, Jm = 1.6 Hz, 3 (5 mL) was added through a syringe. The mixture was heated to
H), 8.87 (d, Jo = 8.2 Hz, 3 H), 7.13 (dd, Jo = 8.2 Hz, Jm = 1.6 Hz, reflux under argon atmosphere with continuous stirring for 8 h in
3 H), 7.77 (d, Jo = 7.6 Hz, 6 H), 7.43 (dd, Jo = JoЈ = 7.6 Hz, 6 H),
both cases. The solution was cooled to room temperature, diluted
7.31 (t, JoЈ = 7.6 Hz, 3 H), 6.81 (dd, Jo = JoЈ = 7.6 Hz, 2 H), 6.66 with toluene (20 mL), filtered and concentrated to ca. 2–3 mL. The
(t, JoЈ = 7.6 Hz, 1 H), 5.50 (d, Jo = 7.6 Hz, 2 H) ppm. 13C NMR
(75.5 MHz, CDCl3, 25 °C): δ = 152.5, 151.6, 151.2, 143.1, 140.4,
crude product was then purified by flash chromatography on silica
gel using a 4:1 mixture of hexane/THF as eluent. Subphthalocyan-
131.7, 129.7, 129.0, 128.9, 128.0, 127.7, 122.5, 121.5, 120.6, ines 8, 9 and C1-6,[5b] eluting in that order, could be further purified
1876
www.eurjoc.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 1871–1879

Peripheral Functionalization of Subphthalocyanines
1
washing with cold hexane and cold methanol. 10 mg (24%) of pre-
12 was obtained as a reddish viscous solid (0.16 g, 11% yield). H
cursor SubPc C1-1 was recovered from this reaction.
NMR (300 MHz, CDCl3, 25 °C): δ = 8.70–8.62 (m), 8.25–8.15 (m),
7.42–7.33 (m), 6.76 (dd, Jo = JoЈ = 7.6 Hz), 6.60 (t, JoЈ = 7.6 Hz),
5.39 (d, Jo = 7.6 Hz), 1.07 (m), 0.35 (m) ppm. 13C NMR
(75.5 MHz, CDCl3, 25 °C): δ = 159.6, 151.4, 150.8, 150.6, 150.5,
150.4, 149.2, 148.9, 130.9, 130.6, 128.8, 125.2, 125.1, 123.3, 121.4,
119.4, 118.9, 112.7, 112.6, 29.7, 25.7, 18.5 ppm. LSI-MS (m-NBA):
m/z = 878 [M]+ (100%), 785 [M – axial phenoxy group]+ (95%).
HRLSI-MS (C48H29BN6O4) [M]+: calcd. 878.3999; found
878.4015. UV/Vis (CHCl3): λmax [log ε (dm3 mol–1 cm–1)] = 573
Subphthalocyanine 8 (Mixture of 3 Regioisomers): (9 mg, 20%
yield); m.p. Ͼ 250 °C. 1H NMR (300 MHz, CDCl3, 25 °C): δ =
9.18–9.05 (m), 8.6–8.3 (m), 8.3–8.0 (m), 7.67–7.58 (m), 7.40–7.28
(m), 7.26–7.08 (m), 6.78–6.68 (m), 6.65–6.57 (m), 5.40–5.30 (m)
ppm. 13C NMR (75.5 MHz, CDCl3, 25 °C): δ = 153.3, 153.1, 152.9,
152.3, 152.1, 151.5, 151.0, 150.7, 150.2, 149.3, 149.2, 148.7, 147.0,
138.0, 137.7, 137.4, 133.6, 132.1, 131.5, 131.0, 130.9, 130.5, 128.8,
128.6, 128.3, 131.3, 131.2, 129.8, 128.9, 125.63, 125.58, 125.5,
124.3, 124.2, 123.5, 123.4, 123.32, 123.27, 123.2, 123.1, 121.7,
119.0, 114.1, 114.0, 113.9, 96.0, 95.6, 95.5, 95.3. LSI-MS (m-NBA):
m/z = 907 [M]+ (10%), 814 [M – axial phenoxy group]+ (10%).
HRLSI-MS (C42H24BI2N7O) [M]+: calcd. 907.0225; found
907.0225. UV/Vis (CHCl3): λmax [log ε (dm3 mol–1 cm–1)] = 593
(4.5), 526 (sh), 330 (4.1), 271 (4.3) nm. FT-IR (KBr): ν = 2936,
˜
2884, 2850, 1525, 1471, 1430, 1318, 1266, 1055 (B–O), 817, 752,
710 cm–1.
Trihydroxy-Subphthalocyanine 14 (1:3 Mixture of C3 and C1 Re-
gioisomers)
(4.6), 487 (4.0), 309 (4.4), 276 (4.5) nm. FT-IR (KBr): ν = 3045
˜
(C–H), 1603, 1547, 1477, 1445, 1322 (C–N), 1269, 1183, 1065 (B–
Method A: This method is essentially the same as Method B, but
without salicylaldehyde; it proceeded very slowly, and only traces of
deprotected material were detected after 2 d at room temperature.
O), 826, 747, 703 cm–1.
Subphthalocyanine 9 (Mixture of 3 Regioisomers): (13 mg, 27%
yield); m.p. Ͼ 250 °C. 1H NMR (300 MHz, CDCl3, 25 °C): δ =
9.18–9.02 (m), 8.60–8.25 (m), 8.15–7.95 (m), 7.58–7.45 (m), 7.4–7.0
(m), 6.79–6.69 (m), 6.64–6.55 (m), 5.45–5.31 (m) ppm. 13C NMR
(75.5 MHz, CDCl3, 25 °C): δ = 153.6, 152.8, 152.7, 152.1, 152.0,
151.5, 151.2, 150.7, 150.5, 150.3, 150.2, 149.6, 149.4, 148.7, 147.22,
147.17, 147.1, 138.0, 137.7, 137.4, 133.6, 133.4, 132.1, 131.5, 131.2,
131.0, 130.94, 130.88, 130.5, 129.0, 128.4, 128.2, 129.73, 129.67,
128.9, 125.6, 125.5, 125.4, 125.3, 124.4, 124.3, 124.2, 123.4, 123.3,
123.1, 123.0, 122.9, 121.3, 118.9, 114.5, 114.4, 114.0, 113.9, 95.0,
94.7 ppm. LSI-MS (m-NBA): m/z = 949 [M]+ (10%), 856 [M –
axial phenoxy group]+ (10%). HRLSI-MS (C54H34BIN8O) [M]+:
calcd. 948.1993; found 948.2015. UV/Vis (CHCl3): λmax [log ε
(dm3 mol–1 cm–1)] = 608 (4.5), 453 (4.0), 305 (4.5) nm. FT-IR (KBr):
Method B: To a mixture of SubPc 12 (35 mg, 0.04 mmol), and sali-
cylaldehyde (29 mg, 0.24 mmol) in CH2Cl2 (3 mL) was added, at
room temperature, BF3·Et2O (0.1 mL, 1 mmol). The solution color
immediately changed from intense pink to blue. The mixture was
stirred for 24 h at room temperature and the solvent was evapo-
rated. The solid residue was dissolved in ethyl acetate, the solution
recovering its original pink color, and 0.1  HCl was added (2 mL).
The organic layer was washed with brine (10 mL) and dried with
MgSO4. Compound 14 was purified by column chromatography
on silica gel using a 10:1 mixture of CH2Cl2/THF as eluent. Pre-
cipitation from a hexane/CH2Cl2 mixture yielded a pink solid
(6 mg, 26% yield).
ν = 3061, 3022 (C–H), 1607, 1480, 1445, 1320 (C–N), 1277, 1183,
˜
1059 (B–O), 825, 756, 699 cm–1.
Method C: A solution of SubPc 12 (35 mg, 0.04 mmol) in 3 mL of
THF was cooled down to 0 °C and tetrabutylammonium fluoride
monohydrate (420 mg, 1.5 mmol), dissolved in 1 mL of cold THF
was added. The solution color immediately changed from intense
pink to blue. The mixture was stirred for 3 h at 0 °C and then ethyl
acetate was added, the solution recovering its original pink color.
Immediately after, a 0.1  HCl solution was added (2 mL) and the
organic layer was washed with brine (10 mL) and dried with
MgSO4. Compound 14 was then purified by column chromatog-
raphy on silica gel using a 10:1 mixture of CH2Cl2/THF as eluent.
Precipitation from a hexane/CH2Cl2 mixture yielded a pink solid
(7 mg, 30% yield); m.p. Ͼ 250 °C. 1H NMR (300 MHz, MeOD,
25 °C): δ = 8.73–8.67 (m), 8.21–8.15 (m), 7.50–7.40 (m), 6.82–6.70
(m), 6.65–6.55 (m), 5.43–5.37 (m) ppm. 13C NMR (75.5 MHz,
MeOD, 25 °C): δ = 160.6, 160.3, 152.0, 150.9, 150.8, 150.6, 149.8,
149.7, 133.2, 133.0, 128.7, 124.8, 122.2, 121.7, 121.6, 119.1, 119.0,
118.7, 107.9, 107.8, 107.7 ppm. LSI-MS (m-NBA): m/z = 536
[M]+ (5%), 443 [(M-axial group)+] (20%). HRLSI-MS
(C30H17BN6O4) [M]+: calcd. 536.1404; found 536.1386. UV/Vis
(CHCl3): λmax [log ε (dm3 mol–1 cm–1)] = 575 (4.5), 527 (sh), 307
Hexamethoxy-Subphthalocyanine (10): In a 25-mL two-necked
round-bottomed flask, equipped with a condenser, magnetic stirrer
and rubber seal, BCl3 (5 mL, 1  solution in p-xylene) was added
to 4,5-dimethoxyphthalonitrile (0.94 g, 5 mmol) under argon atmo-
sphere. The reaction mixture was stirred under vigorous reflux for
10 min. The solvent was removed by vacuum distillation and the
resulting red-brown solid was subjected to column chromatography
on silica gel using a 3:1 mixture of hexane/ethyl acetate. SubPc 10
was further purified by precipitation from methanol/water (20:1),
obtaining a red solid (0.21 g, 21% yield); m.p. Ͼ 250 °C. 1H NMR
(300 MHz, CDCl3, 25 °C): δ = 8.24 (s, 6 H), 4.21 (s, 18 H) ppm. 13
C
NMR (75.5 MHz, CDCl3, 25 °C): δ = 149.0, 144.2, 128.7, 115.3,
54.3 ppm. LSI-MS (m-NBA): m/z = 610 [M]+ (5%), 575 [M – Cl]+
(20%). HRLSI-MS (C30H24BClN6O6) [M]+: calcd. 610.1539; found
610.1535. UV/Vis (CHCl3): λmax [log ε (dm3 mol–1 cm–1)] = 572
(4.4), 530 (sh), 406 (3.9), 286 (4.1) nm. FT-IR (KBr): ν = 2849 (C–
˜
H), 1515, 1306, 1257, 1171, 953 (B–Cl), 784, 696 cm–1.
Tri(tert-butyldimethylsilyloxy)-Subphthalocyanine 12 (1:3 mixture of
C3 and C1 regioisomers): In a 25-mL two-necked round-bottomed
flask, equipped with a condenser, magnetic stirrer and rubber seal,
BCl3 (5 mL, 1  solution in p-xylene) was added to 4-(tert-butyldi-
methylsilyloxy)phthalonitrile (1.29 g, 5 mmol) under argon atmo-
sphere. The reaction mixture was stirred under vigorous reflux for
10 min. Phenol (470 mg, 5 mmol) was directly added to the reaction
slurry in p-xylene and the mixture was stirred at 100 °C for 3 h.
The solid obtained was washed with a 2:1 mixture of methanol/
water and subjected to flash column chromatography on silica gel
using a 5:1 mixture of hexane/ethyl acetate as eluent. Compound
(4.1), 279 (4.3) nm. FT-IR (KBr): ν = 3378 (O–H), 3045 (C–H),
˜
1595, 1490, 1432, 1377, 1238, 1206, 1105, 1039 (B–O), 983, 810,
756, 708 cm–1.
Supporting Information (see also the footnote on the first page of
this article): Figure S1, 1H NMR spectra of all new compounds,
including 4-(tert-butyldimethylsilyloxy)phthalonitrile, 4-diphenyl-
amino-phthalonitrile, and SubPcs C3-2, C3-3, C3-4, C3-5, C3-7, 8,
9, 10, 12 and 14, as well as complete assignment of 1H and 13C
NMR signals.
Eur. J. Org. Chem. 2009, 1871–1879
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1877

D. González-Rodríguez, T. Torres
FULL PAPER
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Acknowledgments
Funding from Ministerio de Educación
y Ciencia (MEC)
(CTQ2008-00418/BQU, CONSOLIDER-INGENIO 2010 CDS2007-
00010 NANOCIENCIA MOLECULAR), European Science
Foundation (ESF)-MEC (MAT2006-28180-E, SOHYDS), COST
Action D35, and Comunidad de Madrid (S-0505/PPQ/000225) is
acknowledged.
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[2b]
[13]
[14]
a) See ref.
for a general review and ref. 10a for a typical
synthetic procedure; b) Axial functionalization has been widely
utilized in donor-acceptor systems for energy/electron transfer
applications, since it is a more convenient and straightforward
procedure (see ref.[5a,5b,5d,5e,5g–5j]). The σ-bond character of the
axial linkage does not allow, however, for an efficient electronic
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Published Online: February 11, 2009
Eur. J. Org. Chem. 2009, 1871–1879
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www.eurjoc.org
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