Synthesis and properties of an unsymmetrical triazole-functionalized (phthalocyaninato)zinc complex

Article abstract of DOI:10.1002/ejoc.200500105

The synthesis of 5,6-dicyano-1H-1,2,3-benzotriazole (2) was significantly simplified and its overall yield was increased. This opens up the possibility for an extended use of 2 as a precursor for triazole-functionalized phthalocyanines. One of them, the unsymmetrical {9,10,16,17,23,24-hexakis(3,5- di-tert-butylphenoxy)[1,2,3]triazolo[4,5-b]phthalocyaninato}-zinc (5) was prepared in a statistical condensation of 2 and 4,5-bis(3,5-di-tert- butylphenoxy)phthalonitrile (3) with subsequent separation by column chromatography. The triazole-functionalized (phthalocyanine)zinc complex 5 shows interesting spectral properties in solutions depending on the chemical medium because of the reactions which are typical for the triazole fragment. These are acid ionization of NH, coordination to metal ions, N-alkylation and N-acylation, among others. Compound 5 was characterized in detail using UV/Vis, ¹H and ¹³C NMR spectroscopy, mass spectrometry (MALDI-TOF), and elemental analysis. Wiley-VCH Verlag GmbH & Co. KGaA, 2005.

Full text of DOI:10.1002/ejoc.200500105

FULL PAPER
Synthesis and Properties of an Unsymmetrical Triazole-Functionalized
(Phthalocyaninato)zinc Complex
Sergej Vagin,*[a][‡] Antje Frickenschmidt[b] Bernd Kammerer[c] and Michael Hanack[a]
Keywords: Phthalocyanines / Metal complexes / Unsymmetrical derivatization / Triazole / Spectroscopic properties / Zinc
The synthesis of 5,6-dicyano-1H-1,2,3-benzotriazole (2) was
significantly simplified and its overall yield was increased.
This opens up the possibility for an extended use of 2 as a
precursor for triazole-functionalized phthalocyanines. One of
them, the unsymmetrical {9,10,16,17,23,24-hexakis(3,5-di-
tert-butylphenoxy)[1,2,3]triazolo[4,5-b]phthalocyaninato}-
zinc (5) was prepared in a statistical condensation of 2 and
4,5-bis(3,5-di-tert-butylphenoxy)phthalonitrile (3) with sub-
sequent separation by column chromatography. The triazole-
esting spectral properties in solutions depending on the
chemical medium because of the reactions which are typical
for the triazole fragment. These are acid ionization of NH,
coordination to metal ions, N-alkylation and N-acylation,
among others. Compound 5 was characterized in detail using
UV/Vis, 1H and 13C NMR spectroscopy, mass spectrometry
(MALDI-TOF), and elemental analysis.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
functionalized (phthalocyanine)zinc complex 5 shows inter- Germany, 2005)
ties, causing intramolecular and intermolecular electron
Introduction
and energy transfers, etc.[2] Unsymmetrical phthalocyanines
are required for the generation of second-order nonlinear
optical effects and are expected to give a higher third-order
nonlinear optical response in comparison to the symmetri-
cal Pc’s.[3] The latter property promotes a new application
of phthalocyanines, namely optical limiting.[3,4] Certain un-
symmetrical functionalization of the Pc’s periphery is often
preferable for the formation of highly organized phthalocy-
anine thin films, polymer-grafted materials or metal-sup-
ported phthalocyanine monolayers and other self-organized
systems based on phthalocyanines and their complexes.[2,5]
Unsymmetrical phthalocyanines possessing certain hydro-
philic and lipophilic groups at the same time have a poten-
tial as biologically active materials, and are intensively
studied for example, for their use in cancer therapy.[6]
A plethora of symmetrical and unsymmetrical phthalo-
cyanines functionalized with different substituents have
been prepared to date.[2,7] Among them, the phthalocyan-
ines containing additional heteroatoms in the macrocycle,
e.g. N and S, or fused heterocyclic rings, have received spe-
cial attention, since such structures very often enable dif-
ferent interesting properties of these macrocycles. Thus,
various pyrazine-, phenanthroline-, N-substituted imida-
zole-, thia- and selenadiazole- and other heterocycle-annu-
lated phthalocyanines and porphyrazines were prepared
and intensively investigated.[8,9] 1,2,3-Triazole-function-
alized phthalocyanines, which are especially interesting,
have not been reported yet, besides a poorly characterized
[tetra(triazolo)phthalocyaninato]cobalt compound.[10] The
only reported property of the latter is its solubility in water/
alkali solution. Additionally, its UV/Vis spectra in DMF,
Phthalocyanines and their metal complexes (Pc’s and
PcM’s), as well as their analogues, e.g. porphyrazines, naph-
thalocyanines, etc., have been studied for many years, and
they are still the subject of intense investigation. The high
level of interest in this type of compounds is due to their
potential application in materials science. Phthalocyanines
are used as dyes and catalysts for different processes, as li-
quid crystals and semiconductors, gas sensors and photo-
sensitizers, as active materials in nonlinear optical and elec-
trochromic devices and recordable optical information car-
riers, among other uses.[1] The reasons for the applicability
of phthalocyanines and related compounds to that extended
area of materials science are the peculiarities of their mol-
ecular and electronic structure.[1]
Among phthalocyanines, those with an unsymmetrical
substitution pattern on the periphery of the macrocycle are
of high interest due to their special chemical, physical, and
optical properties.[2] Unsymmetrical substitution in Pc’s and
PcM’s results in specific redistribution of their electron den-
sity, leading to a change in the general dipole moment and
appearance of push-pull effects, changing the redox proper-
[a] Universität Tübingen, Institut für Organische Chemie,
Auf der Morgenstelle 18, 72076 Tübingen, Germany
E-mail: sergej.vagin@uni-tuebingen.de
[b] Universitätsklinikum Tübingen, Medizinische Klinik,
Otfried-Müller-Str. 10, 72076 Tübingen, Germany
[c] Universitätsklinikum Tübingen, Abteilung Klinische Pharma-
kologie,
Otfried-Müller-Str. 45, 72076 Tübingen, Germany
[‡] On leave from: Ivanovo State University of Chemistry and
Technology, Organic Chemistry Department,
153460 Ivanovo, F. Engels 7, Russia
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DOI: 10.1002/ejoc.200500105
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S. Vagin, A. Frickenschmidt, B. Kammerer, M. Hanack
FULL PAPER
concentrated H2SO4, and aqueous NaOH were tabu- Scheme 1.[10,14–16] Additionally, the starting material 1,2-di-
lated.[10] It is known, that imidazolo- or triazolo-porphyraz- bromo-4,5-dinitrobenzene is not commercially available and
ine derivatives, both symmetrical and unsymmetrical, with needs to be prepared as well.[14b]
free NH function of the fused heterocycle rings were not
Therefore, we have developed an alternative route, which
formed in a cyclotetramerization reaction of the corre- also is a multi-step synthesis, but with good yields except
sponding dinitriles.[8a,9c] Therefore, it is of interest whether for the last step to yield 2, which, however, is acceptable for
the unsymmetrical triazole-annulated phthalocyanine with this type of reaction (see Scheme 2 and below). The starting
a free triazole NH group can be obtained in a statistical material o-phenylenediamine is cheap and commercially
cross-condensation from the suitable phthalodinitriles. The available. The only difficult step in this route is the last one,
lack of information on 1,2,3-triazole-fused phthalocyanines in which 5,6-dibromo-1H-benzotriazole 1 is treated with ex-
is mostly due to the difficult synthesis of the corresponding cess CuICN (Rosenmund–von-Braun reaction). The usual
starting material, the dicyanobenzotriazole
Scheme 1). Triazole-fused phthalocyanines, e.g.
2
(see conditions for the Rosenmund–von-Braun reaction (heating
in of the mixture of dibromobenzenes with CuCN in hot
5
Scheme 3, require more attention, because this type of func- DMF) were not applicable in the case of 1, since dibro-
tionalization can give unique properties to a phthalocyan- mobenzotriazole 1 forms strong complexes with copper(i)
ine both from the synthetic (further peripheral functionaliz- cyanide, similar to other benzotriazoles and metal salts.[17]
ation) and the spectroscopic point of view. Benzotriazoles
are amphoteric compounds, which can form different com-
plexes with metal ions and can give different derivatives by
substitution of the N–H atom.[11] The known substituents
at the triazole ring are alkyl, acyl, sulfonyl, amino, and
other groups, the introduction of which can activate the tri-
azole for further reactions. Thus, N-aminobenzotriazole can
be easily oxidized with formation of benzyne.[12] We expect
that an N-aminotriazole-fused phthalocyanine can be a pre-
Scheme 2.
cursor for the generation of the unknown dehydrophthalo-
cyanine.[13a] The analogous dehydrobenzoporphyrazine was
These complexes are practically insoluble in DMF, and
generated recently by us by a different approach and the substitution of bromine in 1 by the cyano group does
trapped with furan,[13b] showing that, in general, this type not occur under reflux in DMF even with a high excess of
of intermediate can exist.
CuCN. However, pyridine is known to solubilize these types
of complexes.[17] Therefore, we have performed the Rosen-
mund–von-Braun reaction in a mixture of Py/DMF (ap-
prox. 40:60) with excess CuCN under reflux for 24 h. Usage
of a rather high excess of CuCN is necessary for a complete
substitution of both bromine atoms in 1. If the reaction
time or the amount of CuCN were lowered, a noticeable
amount of monobromo-monocyano product was obtained.
The additional important step is the workup of the product,
since after the reaction is completed, 2 remains as a stable
copper complex (coordination through the triazole func-
tionality). The only possibility found for destroying this
complex was its treatment with concentrated nitric acid, as
described in the Exp. Sect. The final purification of dinitrile
2 was achieved by crystallization from an ethanol/water
mixture with charcoal.
It is known that a statistical cross-condensation of substi-
tuted phthalonitriles always results in a mixture of phthalo-
cyanines, however, this method is commonly used for the
preparation of different unsymmetrical Pc’s.[8a,18] The tem-
plate cross-condensation of dinitrile 2 with a threefold ex-
cess of 4,5-bis(3,5-di-tert-butylphenoxy)phthalonitrile (3) in
the presence of an equimolar amount of Zn(OAc)2·2H2O in
quinoline gave a mixture of compounds consisting mainly
Scheme 1.
In the following we report on the synthesis and proper-
ties of a mono(triazole)-annulated phthalocyanine complex,
soluble in many common organic solvents for example
CHCl3, THF or DMF, namely {9,10,16,17,23,24-hexa-
kis(3,5-bis-tert-butylphenoxy)[1,2,3]triazolo[4,5-b]phthalo-
cyaninato}zinc (5). Additionally, the improved synthesis of
5,6-dicyano-1H-1,2,3-benzotriazole (2) is reported.
Results and Discussion
Synthesis
As mentioned above, the precursor for a triazole-annu- of symmetrical [octakis(3,5-di-tert-butylphenoxy)phthalo-
lated phthalocyanine, the dicyanobenzotriazole 2 (see cyaninato]zinc complex 4 and the desired 3-to-1 (A3B) cycli-
Schemes 1, 2 and 3), is relatively difficult to obtain. The zation product 5 (see Scheme 3). Compound 3 was chosen
synthesis described in the literature includes several steps, for the cross-condensation with 2 because of two reasons.
some of which proceed with low yields, as shown in First, di-tert-butylphenoxy substituents in 3 lead to a high
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An Unsymmetrical Triazole-Functionalized (Phthalocyaninato)zinc Complex
FULL PAPER
Scheme 3.
solubility of the desired phthalocyanine 5 in common or-
When higher amounts of pyridine were added to the elu-
ganic solvents. Second, these types of substituents give sim- ent, other colored compounds were eluted from the column
1
ple H and 13C NMR spectra, thus facilitating the struc- as a complex mixture according to the analysis using the
tural characterization of the cross-condensation products. It MADLI-TOF technique. Among other peaks in the
was found to be important not to use an excess of Zn(OAc)2 MALDI-TOF spectrum of this mixture, the signal of the
for this synthesis because of the strong tendency of triazole- A2B2 (m/z = 1477) product, also expected from the statisti-
functionalized phthalocyanines to form Zn complexes cal condensation, was observed.
through the triazole ring, which could not be demetallated
to give 5 and which disturb the purification of the desired
product and lower its yield.
UV/Vis Spectra
The separation of 4 and 5 was achieved by column
chromatography using pure dichloromethane or CH2Cl2
The UV/Vis absorption of 5 is unique in comparison, for
with small amounts of THF to elute PcZn 4. Phthalocyan- example with the symmetrical PcZn 4. The Q band is split
ine complex 5 is eluted upon addition of higher amounts of into two components (Qx and Qy bands) due to the lowered
THF or traces of pyridine. The separation was monitored symmetry of 5 (see Figure 1). The Qx band of 5 in compari-
continuously by UV/Vis, since 4 and 5 have UV/Vis spectra, son to 4 shifts noticeably to the red because of the conjuga-
which are distinct enough to draw a conclusion about the tion effect with the triazole ring, whereas the Qy band re-
composition of eluted fractions, considering the relative in- mains practically at the same position as the Q band in 4.
tensity of absorption bands (see below). A complete purifi- This is in agreement with the four-orbital theory of elec-
cation of 5 was achieved with a second chromatographic tronic spectra of phthalocyanines and more recent calcula-
step. However, one has to take into account the unusual tions.[19] The positions of the absorption maxima in 4 or 5
behavior of 5 during chromatography: it was observed that depend on the solvent, which is also a common feature of
a part of 5 was eluted very quickly upon addition of small phthalocyanines. Additionally, the ratio of the intensities of
amounts of THF to CH2Cl2, whereas the other part of 5 the Qx and Qy bands in 5 was found to be sensitive to the
stays on the column and moves down only upon addition nature of the solvent, which might be due to the tendency of
of higher amounts of THF or Py. Both fractions are, never- 5 to dimerization in nonaromatic solvents with low polarity
theless, the same compound according to UV/Vis and through the triazole ring. The UV/Vis spectrum of 4 freshly
MALDI-TOF analysis. Additionally, they show the same dissolved in hexane shows practically no interaction be-
behavior when checked by TLC (silica gel, CH2Cl2/THF tween the phthalocyanine molecules in solution at least at
mixtures), moving with equal Rf values as tailing spots. The low concentrations (Ͻ10–5 m), which is not the case for 5
explanation for this behavior lies in the ability of the phthal- (see Figure 1). The strong decrease in absorption of the Qx
ocyanine complex 5 to form relatively stable coordination band indicates some kind of interaction between molecules
complexes and intermolecular hydrogen bonds through the of 5 involving the fused triazole ring. Indeed, according to
triazole functionality, depending on the solvent {compare theory,[19] it is expected that the changes in electronic struc-
for example with [tri(benzo)(pyridino)porphyrazinato]- ture of the triazole ring annulated to a phthalocyanine sys-
zinc[18b]}. The tendency towards dimerization of 5 was also tem should affect mostly the transition polarized along the
observed in its MALDI-TOF spectrum (see below).
x axis (see Scheme 3), namely the Qx band.
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Figure 1. UV/Vis spectra of 4 and 5 in different solvents.
Figure 2. Spectra of 5 in (a) THF + 20% Py; (b) THF over solid
NaOH; (c) CHCl3/approx. 5×10–3 m CF3COOH; (d) THF + 20%
Py over solid Ni(OAc)2·4H2O; (e) THF + 20% Py after addition
of a small amount of acetic anhydride.
Polar solvents like methanol or acetonitrile do not solu-
bilize 4 or 5, but 5 is relatively soluble in DMF, in contrast
to 4, which is practically insoluble in DMF.
Benzotriazoles are weak acids and can dissolve in aque-
ous alkali,[11] which is also the case for the tetra(triazole)- atom, but not on the triazole ring, although the latter one
substituted (phthalocyaninato)cobalt complex.[10] We have is amphoteric.[11] This can be seen from the spectral changes
studied the UV/Vis spectra of 5 in the presence of bases. taking place upon titration of 5 with CF3COOH in CHCl3.
The UV/Vis spectrum of 5 in THF, CHCl3 or pyridine cor- If protonation of the triazole ring would occur, the Qx band
responds to a “neutral monomeric form” of the triazole- should have shifted hypsochromically because of the elec-
annulated phthalocyanine complex 5 [see Figures 1 and 2 tron-withdrawing effect of the positively charged triazole
and Table 1; for log(ε) values in CHCl3/0.1% Py see Exp. fragment. In contrast, both Qx and Qy bands shift to the
Sect.]. Addition of 1 drop of tetrabutylammonium hydrox- red upon the first protonation, which indicates protonation
ide in MeOH (1 m) into a cuvette with a solution of 5 in of the meso-nitrogen atom of the macrocycle.[20] The expec-
THF resulted in a 27 nm bathochromic shift of the Qx band tation of a blue-shift of the Qx band upon protonation of
due to ionization of the N–H bond of the triazole ring. This the triazole ring was also supported with the following ex-
is because the formed anionic triazole fragment is a periment: acetic anhydride (2 drops) was added into the cu-
stronger electron donor towards the Pc macrocycle in com- vette containing the solution of 5 (2 mL, approx. 10–5 m) in
parison with the nonionized triazole ring.
a THF/Py mixture (4:1) and the UV/Vis spectra were re-
The same spectral changes occur slowly when solid corded, showing the complete change of the spectrum of 5
NaOH is added to a solution of 5 in THF. They are com- within 3 min. The resulting UV/Vis spectrum belongs to a
pletely reversible, since upon neutralization of the basic derivative of 5 with acetylated triazole ring, and the Qx
solution with CF3COOH the UV/Vis spectrum of the start- band shifted slightly to the blue because of the electron-
ing material 5 reappears. The excess of acid first leads to withdrawing effect of the acetyl group and showing the in-
the protonation of the macrocycle on the meso-nitrogen crease of the intensity of the Q bands (see Figure 2).
Table 1. UV/Vis data of compounds 4 and 5.
Compound
Solvent
Additive
Absorption bands, λmax [nm] (rel. intens.)
B
Qx
Qy
Satellites
4
5
5
5
5
5
5
5
5
5
5
5
5
5
n-hexane
n-hexane
CHCl3
–
–
–
–
–
364 (0.331)
361 (0.519)
354 (0.558)
355 (0.574)
360 (0.559)
353 (0.745)
–
359 (0.643)
358 (0.666)
358 (0.646)
357 (0.655)
358 (0.607)
353 (0.469)
363 (0.421)
679 (1.00)
648 (0.154)
612 (0.165)
620 (shoulder)
619 (0.217)
614 (0.191)
616 (0.210)
616 (0.265)
616 (0.280)
615 (0.233)
616 (0.259)
615 (0.238)
618 (0.241)
701 (0.613)
699 (1.00)
696 (1.00)
699 (1.00)
722 (0.864)
723 (0.947)
711 (0.977)
717 (0.925)
710 (1.00)
717 (0.795)
712 (0.878)
734 (1.00)
693 (1.00)
681 (1.00)
683 (0.875)
677 (0.864)
680 (0.887)
682 (1.00)
682 (1.00)
679 (1.00)
681 (1.00)
679 (0.995)
684 (1.00)
682 (1.00)
703 (0.778)
685 (0.928)
650 (0.291)
649 (shoulder)
643 (0.196)
THF
THF + 20%Py
THF
647 (0.217)
NaOH
660 (shoulder)
662 (shoulder)
651 (0.302)
657 (0.345)
651 (0.295)
THF
Bu4N+OH– (traces)
Zn(OAc)2·2H2O
Ni(OAc)2·4H2O
ZnCl2
THF + 20%Py
THF + 20%Py
THF + 20%Py
THF + 20%Py
THF + 20%Py
CHCl3
NiCl2
CoCl2
CF3COOH (traces)
(CH3CO)2O
658 (shoulder)
[a]
640 (shoulder)
620 (0.200)
THF + 20%Py
[a] Bands are overlapping with absorption of cobalt salt.
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An Unsymmetrical Triazole-Functionalized (Phthalocyaninato)zinc Complex
FULL PAPER
Addition of several solid metal salts, e.g. Zn, Ni, Co
chlorides and acetates, to the solution of 5 in THF/Py re-
sulted in a red shift of the Qx band, similarly to the above-
described acid ionization of the triazole NH group, but with
lower shift values, depending on the nature of the metal.
The shift of the Qx band maximum in these cases is due
to the removal of the NH proton of the triazole ring and
coordination of the latter to the metal ion. The presence of
pyridine as the base is necessary, since we did not observe
the described spectral changes upon addition of metal salts
to 5 in pure THF. All UV/Vis data are summarized in
Table 1.
1H and 13C NMR Spectra
The NMR spectra of compounds 4 and 5 are completely
in agreement with their structures. The symmetrical PcZn 4
1
gave very simple H and 13C NMR spectra in CDCl3/10%
[D8]THF (see Exp. Sect. and Scheme 3) with good resolu-
tion of the carbon signals of the aryloxy substituents, al-
though the carbon signals of the phthalocyanine macrocy-
cle were poorly resolved with the C-1 signals not resolved
at all. 3-, 6-, and 8-H in 4 appear as singlets with a relative
broadening for the 3-H signal. In contrast, the spectra of 5
Figure 3. 1H NMR (aromatic region) of compounds 4 in CDCl3/
[D8]THF (a) and 5 in [D8]THF (b).
in [D8]THF are more complicated because of the loss of
the symmetry, but they are better resolved. In general, the
deuterated THF was found from our experience to be one
1
of the best solvents for obtaining well-resolved H and 13C
The NH tautomerism of the triazole ring in 5 can be a
reason for the broadening of the γ-H signal as well. 1H
NMR measurements on 5 in less polar solvents or at lower
temperatures could decrease the rates of tautomer intercon-
version, thus leading to a split γ-H signal and, probably, to
the appearance of two NH proton signals. However, it also
would cause broadening, shifting, and splitting of other sig-
nals of phthalocyanine protons due to aggregation and
other effects, resulting, in general, in poorly resolved spec-
tra. On the other hand, 5 is not soluble enough in solvents
which are noticeably more polar than THF. Nevertheless,
we found the information obtained from the 1H NMR spec-
trum of 5 in [D8]THF at 20 °C to be sufficient for proving
the structure of the compound.
Despite good resolution of all other carbon signals in 5,
signals C-α, -β, -δ, and even -γ were not found in the 13C
NMR spectrum of 5, probably, due to masking by other
strong signals or due to a substantial broadening. The sig-
nal of C-γ, which should be the most intense of the latter
four, would be expected in the range δ = 110–120 ppm,
where many other intense carbon signals appear (see Exp.
Sect.).
NMR spectra of aryl- and aryloxy-substituted phthalocy-
anines.[21,13b] Less polar or noncoordinating solvents often
lead to a noticeable aggregation of phthalocyanines at the
concentrations required for NMR measurements.
Each of the types of protons and carbons of 5 in [D8]-
THF (see Scheme 3) gives groups of signals consisting
1
mainly of three. Thus, in the H NMR spectrum of 5, pro-
tons 6-H give three doublets, protons 8-H give one triplet
and one multiplet, and protons 3-H appear as three sharp
singlets, whereas the γ-protons appear as a broadened sig-
nal (see Figure 3). The protons of the tert-butyl groups also
gave three singlets, two of them close to each other and the
third noticeably down-field-shifted. The same difference in
the shifts can be noticed for all other types of protons.
Probably, the stronger down-field-shifted signals in the
mentioned groups belong to the protons of the substituents
closest to the triazole fragment. The signal of the NH pro-
ton of the triazole ring was not found at all, probably be-
cause of the tautomerism occurring with a rate close to the
relaxation time of the proton under the conditions of the
measurements (20 °C, [D8]THF) or due to the masking by
the intense signals of aromatic protons in the region δ =
7.0–7.5 ppm. An additional reason could be the deuterio
exchange in the case where some D2O is present in [D8]-
THF, since the concentration of 5 in [D8]THF was relatively
low. However, for a concentrated solution of compound 1
MS (MALDI-TOF) Spectra
The data on MALDI-TOF spectra of compounds 4 and
in [D6]DMSO we also did not observe the NH signal (see 5 fully support their structures. Phthalocyanine complex 4
Exp. Sect.).
gives the only cluster peak corresponding to its molecular
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S. Vagin, A. Frickenschmidt, B. Kammerer, M. Hanack
FULL PAPER
ion [M+] without any fragmentation (m/z = 2212) and with showing that molecular ions of 5 fragment to give a poorly
a good fit to the calculated isotopic distribution (when mea- resolved peak at m/z = 1816–1820. Other heaviest fragments
sured with internal standard). This indicates that under ap- appeared at approx. m/z = 1418, 1404, 1312, 1152, 751, 697,
plied conditions the phthalocyanine charging proceeds 684, 633, 608, 554, 542, 488, 477, 455, and 424, when a
through electron removal and not through protonation. wider m/z window was taken. Therefore, the loss of periph-
Compound 5 gives a weak cluster peak at m/z = 3688, eral aryl groups without fragmentation of the macrocycle
which was attributed to a dimeric species (dimerization was not observed in this case. Surprisingly, the heaviest
through the triazole functionality), and two cluster peaks fragments in the PSD spectrum of 4 correspond to the loss
at m/z = 1844 and approx. 1816 (see Figure 4). The ratio of of N or CH2 [M+ – 14], one tert-butyl group [M+ – 57]
their intensities depends on the laser energy, but the peak (weak signal), and of the fragment with m/z = 171, giving
at m/z = 1844 is always the most intense. Calculation of the the peak at m/z = 2042, which we find difficult to assign.
isotopic distribution for the molecular ion of 5 [M+] fits The next intense peaks in the PSD spectrum of 4 are ob-
with the cluster peak at m/z = 1844 (when measured with served at m/z = 1706, 1694, 1206, 1193, 1147, 642, 630, 554,
internal standard). The cluster peak at m/z = 1816 corre- 542, 473, and some others, indicating the rupture of the
sponds to a fragmentation of 5 with the loss of dinitrogen, macrocycle without the loss of peripheral substituents as
which is a common type of fragmentation for benzotri- well. The comparison of the fragmentation patterns of 4
azoles (see Figure 4).[22] However, the isotopic distribution and 5 reveals some similarity in the region of lower masses,
of this peak shows that it is probably due to several species, and shows that the rupture of both macrocycles starts with
such as [M+ – N2] and [MH+ – N2]. Additional measure- the loss of the fragments related to bis(3,5-di-tert-butyl-
ments using the PSD (Post-Source-Decay) technique were phenoxy)isoindoline. MALDI-TOF measurements on com-
also carried out (m/z = 1831–1865 window was taken), pound 5 in the negative mode using the same matrix gave
cluster peaks which correspond to a molecular ion [M– –
H] (formed upon NH group dissociation) and to a fragment
without N2. The difference between the values of the first
isotopic peak of the molecular ion formed upon ionization
of 5 in positive and negative modes was exactly one mass
unit.
IR Spectra
The IR spectra of 4 and 5 are practically identical, since
the main absorption bands in the region 650–1650 cm–1 are
due to the peripheral aryloxy substituents, which are pres-
ent in high number in both compounds. For this reason it
is understandable that many other vibrations in the men-
tioned wavenumber region, which are due to the phthalocy-
anine core, are partially or completely masked, and the
change of the core symmetry from 4 to 5 or addition of the
triazole ring does not lead therefore to a change of the
whole IR spectrum. The NH functionality of the triazole
ring in 5, which is expected to give vibration bands at 3100–
3400 cm–1, is also not observed, probably, because of the
very low intensity of the corresponding bands in compari-
son with other bands in the spectrum and because of the
covering by the broad absorption band of water in KBr.
Conclusions
We have shown the applicability of the statistical synthe-
sis for the preparation of the unsymmetrical phthalocyanine
complex 5 containing a triazole functionality on the periph-
ery. Compound 5 is highly soluble in common organic sol-
vents with medium polarity. Phthalocyanine complex 5 was
found to possess unique spectral properties depending on
the chemical medium due to the reactivity of the triazole
fragment. Many reactions which are characteristic for
benzotriazole, for example N-alkylation, N-acylation and
Figure 4. MALDI-TOF spectrum of compound 5 (a) and its
zoomed view (b, c), measured without internal standard.
3276
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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An Unsymmetrical Triazole-Functionalized (Phthalocyaninato)zinc Complex
FULL PAPER
drate). 1H NMR ([D6]DMSO, numbering according to the no-
menclature): δ = 6.14 (s, broad, approx. 4 H, NH, H2O); 8.80 (s, 2
H, 4,7-H) ppm. 13C NMR ([D6]DMSO, numbering according to
the nomenclature): δ = 110.2 (s, C-5,6), 116.5 (s, CϵN), 124.5 (s,
C-4,7), 139.8 (s, C-8,9) ppm. EI MS: m/z (%) = 169.1 (100) [M+],
141.1 (68) [M+ – N2], 114.1 (18) [M+ – N2 – HCN], 87.2 (19), 63.2
(16). C8H3N5·1.25H2O (169.2 + 22.5): calcd. C 50.13, H 2.89, N
36.54; found C 50.00, H 2.59, N 36.42. Some part of 2 was purified
by column chromatography (CHCl3/THF) and obtained as a water-
free compound. FT-IR spectra of the hydrate and water-free 2 (w/
others, are expected to be also typical for this phthalocyan-
ine. Thus, the activity of 5 towards acetic anhydride under
acylation conditions was observed in preliminary experi-
ments using UV/Vis spectrophotometry. These types of re-
actions could be useful, for example, for binding the phthalo-
cyanine to different surfaces, polymers, and biologically
active molecules, which is of high interest for many applica-
tions in materials science. Additionally, the triazole frag-
ment is an excellent precursor group for further unsymmet-
rical chemical modifications of the phthalocyanine macro- f 2) show some difference. FT-IR of the hydrate (KBr): ν = 3586
˜
(s) (absent for w/f 2), 3363 (m), broad (absent for w/f 2), 3275 (vw)
shoulder (appears as sharp medium intensity band for w/f 2), 3106
(m), 3036 (m), 2238 (s), 1623 (m), 1494 (w), 1405 (w), 1385 (vw)
(appears as medium intensity band for w/f 2) 1369 (w), 1312 (m),
1275 (m), 1218 (s), 1163 (m), 1075 (m), 990 (s) (splits into two at
1009 and 981 for w/f 2), 919 (m), 888 (m), 826 (vw) (medium for
w/f 2), 775 (m), (very weak for w/f 2), 655 (vw), (more intense for
w/f 2), 530 (s), 475 (m), broad (absent in w/f 2) cm–1.
cycle. The work on these topics is continuing within our
research group.
Experimental Section
General: 4,5-Bis(3,5-di-tert-butylphenoxy)phthalonitrile (3) was
prepared according to a procedure previously described.[23] Other
chemicals and solvents were purchased from commercial sources
and were used without additional purification, unless mentioned.
4,5-Dibromo-o-phenylenediamine was prepared according to the
route described in ref.[9a]
[2,3,9,10,16,17,23,24-Octakis(3,5-bis-tert-butylphenoxy)phthalocy-
aninato]zinc (4) and {9,10,16,17,23,24-hexakis(3,5-di-tert-butylphen-
oxy)[1,2,3]triazolo[4,5-b]phthalocyaninato}zinc (5): Dinitriles 2 (0.34 g,
2 mmol) and
3 (3.2 g, 6 mmol) were mixed with Zn(OAc)2·
Instrumentation: UV/Vis: Shimadzu UV-365; 1H and 13C NMR:
Bruker AC 250 (1H: 250.131 MHz; 13C: 62.902 MHz). MS (EI,
MALDI-TOF): Finnigan TSQ 70 MAT, Bruker Autoflex. Elemen-
tal analysis: Euro EA 3000. FT-IR: Bruker Tensor 27.
2H2O (0.44 g, 2 mmol) and quinoline (3 mL), first passed through
the column with basic alumina. The mixture was heated up to
200 °C and was allowed to react for 1.5 h. After cooling, the solidi-
fied mass was washed thoroughly with aqueous methanol, dried
and subjected to column chromatography on silica gel. Using
dichloromethane allowed the elution of the main part of 4. Gradual
addition of THF (starting from 0.2%) to CH2Cl2 resulted in elution
of an additional part of 4, followed by 5. Addition of traces of
pyridine helped to complete elution of 5. The course of chromatog-
raphy was continuously monitored by UV/Vis spectroscopy. Ad-
ditionally, TLC control (silica gel) using CH2Cl2 with traces of
THF can be applied to verify the separation of compounds: 4 has
a higher Rf value than 5 and also moves rather quickly with pure
CH2Cl2 (Rf Ϸ 0.6–0.8) in contrast to 5. All collected fractions with
phthalocyanine complex 5 were purified additionally by a second
chromatography, the solvent was completely evaporated and the
residue was washed several times with methanol with decantation.
5,6-Dibromo-1H-benzotriazole (1): 4,5-Dibromo-o-phenylenediam-
ine (20 g, 0.075 mol)[9a] was dissolved in CH3COOH (125 mL) and
H2O (20 mL), and the solution was cooled to 0 °C. NaNO2 (5.6 g,
0.081 mol), dissolved in H2O (10 mL), was added dropwise to this
solution with good stirring, maintaining a temperature of 0 °C or
below. The formed voluminous precipitate was filtered off, washed
with a small portion of water, dried and crystallized from aqueous
ethanol, giving slightly orange needles. Yield 17 g (82%) after dry-
ing. Crystallization with charcoal gave practically colorless crystals.
C6H3Br2N3 (276.9): calcd. C 26.02, H 1.09, N 15.17; found C 25.96,
H 1.06, N 14.87. EI MS: m/z (%) = 276.9 (100) [M+], 248.9 (92)
[M+ – N2]. 1H NMR ([D6]DMSO, numbering according to the no-
menclature): δ = 8.27 (s, 2 H, 4,7-H) ppm. 13C NMR ([D6]DMSO,
numbering according to the nomenclature): δ = 119.9 (s, broad-
ened, C-4,7), 120.9 (s, C-5,6), 139.3 (s, broad, C-8,9) ppm.
4: 1.15 g (35%). UV/Vis (CHCl3): λ (rel. intens.) = 289 (0.185), 357
(0.350), 615 (0.180), 653 (0.165), 683 (1.00) nm. FT-IR (KBr): ν =
˜
2964 (vs), 2868 (w), 1609 (m), 1587 (s), 1450 (s), 1422 (s), 1401 (vs),
1363 (w), 1298 (s), 1270 (m), 1246 (w), 1198 (m), 1141 (w), 1090
(m), 1036 (m), 962 (m), 903 (w), 876 (w), 749 (w), 707 (w) cm–1.
1H NMR (CDCl3/10% [D8]THF): δ = 1.25 (s, 144 H, 10-H); 7.05
(s, 16 H, 6-H); 7.17 (s, 8 H, 8-H); 8.95 (s, broadened, 8 H, 3-H)
ppm. 13C NMR (CDCl3/10% [D8]THF): δ = 31.3 (s, C-10), 34.9 (s,
C-9), 112.6 (s, C-6), 113.8 (s, poorly resolved, C-3), 117.3 (s, C-8),
134.3 (s, poorly resolved, C-2), 150.4 (s, poorly resolved, C-4), 152.4
(s, C-7), 156.9 (s, C-5) ppm. MS (MALDI-TOF, α-cyano-3-hy-
droxycinnamic acid as matrix): m/z = 2212 [M+]. C144H176N8O8Zn
(2212.4): calcd. C 78.18, H 8.02, N 5.06; found C 78.15, H 7.97, N
4.84.
5,6-Dicyano-1H-benzotriazole (2): Compound 1 (9 g, 32.5 mmol)
was dissolved in DMF (60 mL, dried with molecular sieves) and
CuCN (12 g, 134 mmol) was added to the solution, resulting in the
formation of a yellowish precipitate. The suspension was heated
with good stirring up to 140–145 °C, and pyridine (30–40 mL) was
added portion-wise until the main part of the precipitate was dis-
solved. The reaction mixture was heated for 24 h during which two
extra portions of CuCN (3 g, 33.5 mmol each portion) were added
(approx. after 8 and 16 h). Then the hot mixture was poured on
ice/water (approx. 0.5 L) with stirring, the formed precipitate was
ground, filtered off, washed and dried. Then, 25–30% HNO3 was
added to it in small portions with good mixing, until no more evol-
ution of NO2 was observed upon addition of the acid (Caution:
Only in good ventilated hood!). The slightly greenish residue was
filtered off, dried and dissolved in 65% HNO3 (approx. 10–15 mL
per 3 g) with heating. The formed solution was poured hot into ice/
5: 0.36 g (10%). UV/Vis (CHCl3 + 0.1% Py): λ (log ε) = 362 (4.95),
620 (4.53), 651 (4.51), 684 (5.19), 701 (5.25) nm. FT-IR (KBr): ν =
˜
2964 (vs), 2869 (w), 1607 (m), 1587 (s), 1454 (s), 1422 (s), 1402 (vs),
1364 (w), 1297 (s), 1271 (m), 1197 (m), 1141 (w), 1119 (w), 1094
water (100 mL per 10 mL of acid) and placed into the refrigerator (m), 1035 (m), 961 (m), 902 (w), 864 (w), 746 (w), 707 (w) cm–1.
(0 °C) overnight. The formed precipitate was filtered off, washed
with water, dried and recrystallized from water/ethanol (approx.
1:1) with charcoal. Yield 3.1 g (50%) of yellowish crystals (as hy-
1H NMR ([D8]THF): δ = 1.35 (s), 1.36 (s), 1.42 (s) (108 H, 10-H);
4
4
4
7.16 (d, J Ϸ 1.5 Hz), 7.18 (d, J Ϸ 1.7 Hz), 7.24 (d, J Ϸ 1.7 Hz)
(12 H, 6-H); 7.29 (m), 7.39 (t, 4J Ϸ 1.6 Hz) (6 H, 8-H); 9.06 (s),
Eur. J. Org. Chem. 2005, 3271–3278
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© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3277

S. Vagin, A. Frickenschmidt, B. Kammerer, M. Hanack
FULL PAPER
9.08 (s), 9.12 (s) (6 H, 3-H); 9.65 (s, broadened,2 H, γ-H) ppm. 13
C
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(s), 113.3 (s), 113.9 (s) (C-6); 114.1 (s), 114.9 (s), 115.2 (s) (C-3);
117.78 (s), 117.83 (s), 118.3 (s) (C-8); 135.5 (s), 135.6 (s) (C-2);
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(1844.8 + 9): C 75.16, H 7.39, N 8.31; found C 74.99, H 7.31, N
8.36.
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Received: February 8, 2005
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© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Org. Chem. 2005, 3271–3278