Tetra[6,7]quinoxalinoporphyrazines: The effect of an additional benzene ring on photophysical and photochemical properties

Article abstract of DOI:10.1002/ejoc.200901149

Synthetic methods for a series of zinc tetra[6,7]quinoxalinoporphyrazines (6,7-TQP) with peripheral chains connected through the S, O and. N heteroatoms as well as through the C-C bond were developed. Photophysical and photochemical properties of 6,7-TQP were compared with tetrapyrazinoporphyrazines (TPP) bearing the same peripheral substitueras to disclose the effect of insertion of a benzene ring between the pyrazine and porphyrazine moieties. The influence of the peripheral heteroatom in the group of 6,7-TQP is also discussed. Prepared 6,7-TQP have their main absorption band (Q-band) strongly batho- and hyperchromically shifted (λmax = 730-770 nm in pyridine, ε up to 500000 dm³mol^-1 cm^-1) in comparison to TPP. They showed high singlet oxygen quantum yields (φ_Δ = 0.50-0.74) and relatively low fluorescence quantum, yields (φ_F < 0.08).

Full text of DOI:10.1002/ejoc.200901149

FULL PAPER
DOI: 10.1002/ejoc.200901149
Tetra[6,7]quinoxalinoporphyrazines: The Effect of an Additional Benzene Ring
on Photophysical and Photochemical Properties
Veronika Novakova,[a] Petr Zimcik,*[a] Miroslav Miletin,[a] Kamil Kopecky,[a] and
Zbynek Musil[a]
Keywords: Absorption / Fluorescence / Nucleophilic substitution / Phthalocyanines / Singlet oxygen
Synthetic methods for a series of zinc tetra[6,7]quinoxalino- ence of the peripheral heteroatom in the group of 6,7-TQP is
porphyrazines (6,7-TQP) with peripheral chains connected
through the S, O and N heteroatoms as well as through the
C–C bond were developed. Photophysical and photochemi-
cal properties of 6,7-TQP were compared with tetrapyrazino-
porphyrazines (TPP) bearing the same peripheral substitu-
ents to disclose the effect of insertion of a benzene ring be-
tween the pyrazine and porphyrazine moieties. The influ-
also discussed. Prepared 6,7-TQP have their main absorption
band (Q-band) strongly batho- and hyperchromically shifted
(λmax = 730–770 nm in pyridine, ε up to 500000 dm3 mol–1
cm–1) in comparison to TPP. They showed high singlet oxy-
gen quantum yields (Φ∆ = 0.50–0.74) and relatively low
fluorescence quantum yields (ΦF Ͻ 0.08).
ripheral substitution of the Pc ring.[10] However, a more
pronounced effect is generally achieved by enlargement of
the π-conjugated system.[11,12] Thus, condensation of an-
other aromatic ring to the Pc core can shift the absorption
bathochromically, resulting in naphthalocyanines (Ncs) or
tetra[6,7]quinoxalinoporphyrazines (6,7-TQPs) if the ring is
benzene or pyrazine, respectively. Ncs are well known and
widely investigated compounds.[13,14] 6,7-TQPs have been
discovered only recently[15,16] because of the lack of reliable
synthetic methods leading to their precursors. However, re-
cent developments[17–19] in the synthesis of a key starting
material 4,5-diaminophthalonitrile (1) will surely lead to
more extensive exploration of this class of organic dyes.
All up to now, prepared and investigated 6,7-TQPs have
their peripheral chains connected solely through carbon.[20]
However, a heteroatom connecting the peripheral chain is
known to alter substantially the behaviour of the whole
macrocycle.[21] Recently, we developed a synthetic method
to alkylamino 6,7-TQP derivatives.[22] In the presented
work, we show a synthetic route to the series of 6,7-TQPs
bearing peripheral chains connected through the S and O
heteroatoms as well as through the C–C bond. To reveal
the effect of enlargement of the macrocyclic system on the
photophysical and photochemical properties, we compared
prepared 6,7-TQPs with their lower homologues from a
group of tetrapyrazinoporphyrazines (TPPs) bearing the
same substituents.
Introduction
Phthalocyanine (Pc) and their derivatives have attracted
the steady attention of researchers for a long time because
of the prospective photophysical and photochemical prop-
erties of these compounds. They found their place in many
different areas as industrial dyes[1,2] chemical sensors,[3]
fluorophors,[4] electrocatalysts[5,6] photosensitizers in photo-
dynamic therapy[7] and antennas in artificial photosynthesis
or solar energy conversion.[8,9] Since many of the above-
mentioned applications are based on excitation by light, the
absorption profile of newly prepared Pc chromophores
serves often as the first feature to reveal their potential im-
pact for practical use. Light of longer wavelength is less
scattered by the environment, allowing the ray of activating
light to be aimed at a particular target. At the same time,
human tissues are also more permeable to light of longer
wavelengths (close to 800 nm), thus allowing a deeper thera-
peutic hit in, for example, photodynamic therapy. A high
extinction coefficient (ε) of the activating wavelength is ben-
eficial, as it ensures the same effect at lower dye concentra-
tion. In summary, redshifted absorption and higher ε are
considered to be advantageous in many applications.
Pcs have their main absorption band (Q-band) between
670–700 nm with ε usually up to 200000 dm3 mol–1 cm–1.
The absorption maximum can be redshifted by suitable pe-
[a] Department of Pharmaceutical Chemistry and Drug Control,
Faculty of Pharmacy in Hradec Kralove, Charles University in
Prague,
Results and Discussion
Heyrovskeho 1203, Hradec Kralove, 50005, Czech Republic
Fax: +420-495067167
Synthesis
E-mail: petr.zimcik@faf.cuni.cz
Similarly to Pc and related compounds, the synthesis of
the 6,7-TQPs was performed by cyclotetramerization of
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.200901149.
732
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2010, 732–739

Photophysical and Photochemical Properties of Enlarged Phthalocyanines
aromatic ortho-dicarbonitriles. In this case, suitably 2,3-di- modified, giving comparable yields (83% this work, 78%
substituted quinoxaline-6,7-dicarbonitriles were prepared. published) in much shorter time (15 min instead of 24 h)
A choice of peripheral substituents was lead by the idea without the necessity of anhydrous conditions.
of lowering undesirable aggregation of the final 6,7-TQP
Thereafter, the prepared precursors were subjected to a
macrocycle. Aggregation induces a release of energy by dif- cyclotetramerization reaction. TPP1, TPP3 and TPP4 were
ferent relaxation channels (usually through heat) that would synthesized according to published procedures. The several-
misrepresent the obtained photophysical and photochemi- step method using cyclization of appropriate precursor (2,
cal data. The synthesis of the precursors was carried out 3, 5, 6 and 9) via magnesium butoxide initiator followed
via two different approaches (Scheme 1). Compounds 2 and by demetallation by p-toluenesulfonic acid and subsequent
3 having their substituents connected through the C–C chelation of zinc into the centre of the metal-free macro-
bond were prepared by condensing 1 with appropriately cycle by using anhydrous zinc acetate was revealed as the
substituted vicinal diketones (Method A) that were pre- best approach to TQP1–TQP4 and TPP2 (Figure 1). Other
pared similarly to published procedures.[23,24] As the reac- procedures using lithium butoxide as initiator or employing
tion is facilitated in acidic medium, acetic acid was used the template effect of the zinc cation in high boiling solvents
as the solvent. Method B employing the recently developed (DMF, DMAE, quinoline) did not lead to better results. It
intermediate 2,3-dichloroquinoxaline-6,7-dicarbonitrile (4) is interesting to point out that the magnesium butoxide
[22]
was used for the synthesis of heteroatom-linked periph- method was also successful in the preparation of TQP3,
eral chain bearing precursors 5–7. The chlorine atoms on although our previous attempts did not lead to the desired
the electron-deficient positions of 4 are easily exchanged by product.[22]
nucleophilic substitution with amines to compound 5.
Thiolates and phenolates as stronger nucleophiles reacted
rapidly with 4 under mild conditions to yield precursors 6
and 7, respectively, in good yields. Most of the studied TPPs
were synthesized by published procedures. That is why only
precursor 9 had to be prepared newly by condensation of di-
aminomaleonitrile with the appropriate diketone by apply-
ing method A. Also, a published synthesis of 12[25] was
Figure 1. Structures of macrocycles investigated in this work.
The problematic part of the synthesis was TQP1, where
a major, deep-blue side product sticking to the baseline of
the TLC plate (toluene/pyridine, 5:1) was observed aside
from the anticipated product (Rf = 0.72). Its appearance
was detected even for the Mg complex. A longer reaction
time led to a significantly more intense fraction on the start.
We isolated both fractions by scraping them from the TLC
plate. The mass spectrum (MALDI-TOF) of the fraction
with Rf = 0.72 corresponded to desired MgTQP1 (cluster
at m/z = 1544), whereas the mass spectrum of the fraction
from the start was composed of clusters at m/z = 1444,
1344, 1244, 1144, etc., corresponding to the stepwise loss of
peripheral butoxycarbonyl groups (∆m/z = 100). When pure
MgTQP1 was isolated and converted into the zinc complex,
similar side products were detected on the start, which were
more pronounced when a higher temperature was used dur-
ing the chelation step. We suggest therefore that a higher
temperature may lead to cleavage of peripheral chains, lead-
ing to products with stronger aggregation (sticking to the
baseline of the TLC plate). As a consequence, we changed
Scheme 1. Synthesis of precursors. Reagents and conditions: (a)
acetic acid, THF, reflux, 3–9 h; (b) EtOH, diethyl oxalate, 140 °C,
8 h; (c) 1,2-dichloroethane, SOCl2, DMF, reflux, 3 h; (d) for 5: di-
ethylamine, THF, room temp., overnight; for 6, 2-methylpropan-2-
thiol, NaOH/water, THF, room temp., 15 min; for 7: 2,6-diisopro-
pylphenol, NaOH/water, THF, room temp., 130 min; (e) acetic
acid, reflux, 2–9 h.
Eur. J. Org. Chem. 2010, 732–739
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
733

V. Novakova, P. Zimcik, M. Miletin, K. Kopecky, Z. Musil
FULL PAPER
the reaction conditions by shortening the reaction time dur- jugated system of Pc via condensation of pyrazine rings
ing tetramerization with Mg butoxide to 3 h and lowering (6,7-TQP) is lower than in the case of isosteric benzene
the temperature below 120 °C during chelation step, and rings (Nc). While the absorption maximum of TQP4 lies at
under these conditions, MgTQP1 was obtained with only 754 nm (pyridine), similar octa(alkylsulfanyl)Nc absorbs at
minor side products.
777 nm (THF).[13] Such a hypsochromic effect of the intro-
Cyclotetramerization of aryloxy derivatives of TPP and duction of nitrogen atoms into the macrocyclic core is in
analogous compounds is known to be complicated by accordance with analogous dependences described between
transetherification.[21,26,27] The ether linkages in 7 and 12 Pc and their aza analogues (TPP).[30]
are not stable under conditions of the general method de-
scribed above, as the carbon atoms in the 2- and 3-positions
of the quinoxaline (7) and in the 5- and 6-positions of the
pyrazine ring (12) are strongly electron deficient and are
attacked by the alkoxide used as the initiator. Recently,
Makhseed et al. described a successful method for the
cyclotetramerization of 7 into TPP5 by employing zinc ace-
tate in dry quinoline,[25] but our attempts to repeat their
procedure failed. Satisfactory results were achieved with the
method developed for similar compounds by Mørkved et
al.[28,29] by employing cyclotetramerization of 7 or 12 di-
rectly in a melt with a Zn(quinoline)2Cl2 complex.
Due to the presence of aggregation inhibiting substitu-
ents, all prepared compounds showed very good solubility
Figure 2. Normalized absorption spectra of TPP (dashed lines) and
in common laboratory solvents. A peculiar behaviour was
TQP (solid lines) in pyridine [1 (c), 2 (b), 3 (e), 4 (d) and 5 (a)].
observed only for TQP2, which was practically insoluble
(only slightly in DMF and pyridine) despite its bulky neo-
pentyl substituents. For comparison, its homologue TPP2
or isoster TQP4 showed very good solubility.
The position of the Q-band was influenced also by the
heteroatom connecting the peripheral chain or by conjuga-
tion of the peripheral carbonyl group with the 6,7-TQP π-
system (Figure 2, Table 1). Aliphatic alkyls do not contrib-
ute to a redshift and compounds with such modification
usually absorb at the same wavelength as unsubstituted
macrocycles.[31,32] TQP2 can be therefore considered as the
UV/Vis Absorption
The shapes of the absorption spectra of prepared TQP1– standard for comparison. The butoxycarbonyl groups of
TQP5 were typical for similar macrocycles (TPP, Pc, Nc) TQP1 shifted the position of the Q-band significantly
with a low-energy Q-band in the area 730–770 nm and a bathochromically due to the strong conjugation of the car-
high-energy B-band in the area 320–430 nm (Figure 2). The bonyl group with the π-system of the TQP core. The elec-
significant redshift of approximately 100 nm compared to tron-donating N,N-diethylamine (TQP3) and tert-butyl-
the corresponding TPP is obvious from Table 1. The most sulfanyl (TQP4) groups also have a positive effect on the
manifested redshift (∆λ) occurred between derivatives bear- bathochromic shift caused by the participation of the lone
ing peripheral substituents linked by a C–C bond. It is note- pair of electrons of the nitrogen and sulfur on the π-system
worthy that the effect induced by enlargement of the π-con- of the macrocycle. However, the effect was only weak (4 nm
Table 1. Photophysical, photochemical and spectroscopic data of the studied compounds in pyridine.
[a]
Substitution
Compound
λmax / nm
∆λ / nm
Φ∆
ΦF,[a] λF / nm
Ref.
(ε / dm3 mol–1 cm–1)
C (COOBu)
TQP1
TPP1
770 (247000)
658 (158400)
112
0.50
0.015, 780
0.11, 672[b]
[23]
0.52[b]
C (neopentyl)
TQP2
TPP2
750 (174000)
642 (227400)
108
0.64
0.56
0.039, 755
0.24, 648
N
S
TQP3
TPP3
754 (223600)
664 (183100)
90
0.63
0.020
0.032, 760
n.d.[c]
[33]
[33]
TQP4
TPP4
754 (510000)
657 (298000)
97
0.74
0.65
0.042, 759
0.30, 663
O
TQP5
TPP5
730 (411000)
628 (200200)
102
0.69
0.61
0.075, 735
0.29, 637
[a] Mean of three independent measurements, estimated error Ϯ15%. No changes in absorption spectra were observed during the measure-
ments. [b] Measured in DMF. [c] Not detected.
734
www.eurjoc.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2010, 732–739

Photophysical and Photochemical Properties of Enlarged Phthalocyanines
when compared to TQP2). These heteroatom linkages in-
Conclusions
duced much stronger bathochromic shifts of 22 and 15 nm
in their corresponding TPP derivatives TPP3 and TPP4,
respectively, when compared to TPP2. Conversely to other
heteroatom-substituted 6,7-TQP and TPP, aryloxy substitu-
tion induced a hypsochromic shift of the Q-band maximum,
again more pronounced at the latter type of macrocycles.
As regards a strength of absorption, the 6,7-TQP core
has noticeably a positive effect. The TQP core induces 1.3–
2.0 times higher ε than corresponding TPP. The only excep-
tion is the low value for TQP2, which is most likely influ-
enced by its low solubility. In the group of 6,7-TQP, the
sulfur- and oxygen-substituted derivatives (TQP4 and
TQP5) showed ε values over 400000 dm3 mol–1 cm–1, which
is approximately two times higher than those connected
through carbon or nitrogen (TQP1–TQP3).
In conclusion, heteroatom-substituted 6,7-TQPs benefit
from an expanded π-system and the associated batho- and
hyperchromically shifted absorption in the Q-band area in
comparison to investigated TPP homologues. The enlarge-
ment of the macrocyclic core leads to an increase in the
values of Φ∆ and a decrease in the values of ΦF when com-
pared to the values obtained for the TPP system. As a con-
sequence, TQPs may be useful tools in applications em-
ploying singlet oxygen, but not in those based on fluores-
cence emission. Heteroatom linkage was shown to influence
substantially both the photophysical and photochemical
properties of the basic macrocyclic core. Due to a strong
absorption in the near-infrared region as well as to strong
singlet oxygen production, these novel 6,7-TQPs may be-
come an attractive alternative to established porphyrinoid
compounds in applications based on absorption of light
and singlet oxygen production (e.g., photodynamic therapy,
photooxidation, photodegradation of waste waters).
Singlet Oxygen Production and Fluorescence Emission
The efficiency with which the 6,7-TQPs can generate sin-
glet oxygen was evaluated quantitatively by determination
of their singlet oxygen quantum yields (Φ∆) in pyridine. No
changes in the absorption spectra of the 6,7-TQPs were ob-
served during measurements, suggesting that neither photo-
degradation nor aggregation took place. The results are
summarized in Table 1.
Experimental Section
Materials and Methods: All organic solvents were of analytical
grade. Anhydrous butanol was stored over magnesium and distilled
prior to use. TLC was performed on Merck aluminium sheets with
silica gel 60 F254. Merck Kieselgel 60 (0.040–0.063 mm) was used
for column chromatography. The infrared spectra were measured
with an IR Spectrometer Nicolet Impact 400 in KBr pellets. The
1H and 13C NMR spectra were recorded with a Varian Mercury –
All investigated 6,7-TQPs showed high Φ∆, indicating
very efficient transformation of absorbed light energy into
singlet oxygen. Singlet oxygen quantum yields for the corre-
sponding TPP derivatives are lower (except TQP1), indicat-
ing a positive effect of the 6,7-TQP core on singlet oxygen
production. Alkylsulfanyl TQP4 appeared to be the strong-
est singlet oxygen producer, confirming similar findings at
heteroatom-substituted TPP homologues.[21] As regards
alkylamino substitution, quantum yields of singlet oxygen
as well as fluorescence quantum yields are extremely low for
TPP3 due to quenching of excited states by intramolecular
photoinduced electron transfer.[33] A similar effect was ex-
pected for TQP but the enlarged system of TQP3 showed
a Φ∆ value of 0.63, which is comparable with other 6,7-
TQPs in the series, suggesting that photoinduced electron
transfer is not a thermodynamically favourable way for the
excited state of the macrocycle to relax. For comparison to
our data in Table 1, Mitzel et al.[15] described Φ∆ = 0.56
(THF) for acetylenic zinc 6,7-TQP.
As the absorbed energy is released mainly through singlet
oxygen production, the fluorescence quantum yields of all
TQPs were relatively low (ΦF Ͻ 0.08, Table 1), generally
several times lower than the value for the corresponding
TPPs. The shapes of the fluorescence emission spectra were
typical for Pcs and related compounds with only small
Stokes shift (Figure S3, Supporting Information). The fact
that the excitation spectra superimposed the absorption
spectra confirmed that the compounds were exclusively in
the monomeric form during the measurements of fluores-
cence as well as singlet oxygen.
Vx BB 300 (299.95 MHz for H and 75.43 MHz for 13C). The re-
1
ported chemical shifts are relative to Me4Si. Elemental analysis was
carried out with an Automatic Microanalyser EA1110CE (Fisons
Instruments S.p.A., Milano, Italy). The UV/Vis spectra were re-
corded by using a UV-2401PC spectrophotometer (Shimadzu
Europa, GmbH, Duisburg, Germany). The fluorescence spectra
were obtained with an AMINCO-Bowman Series 2 luminescence
spectrometer (SLM-Aminco, Urbana, IL, USA). The MALDI-
TOF mass spectra were collected with a Voyager-DE STR mass
spectrometer (Applied Biosystems, Framingham, MA, USA) cal-
ibrated externally with a five-point calibration procedure by using
Peptide Calibration Mix1 (LaserBio Labs, Sophia-Antipolis,
France). The sample solution (0.5 µL) was spotted onto a target
plate, air-dried and covered with 0.5 µL of a matrix solution con-
sisting of 10 µg of α-cyano-4-hydroxycinnamic acid in 100 µL ace-
tonitrile. In the case of TPP2 and TQP3, trans-2-[3-(4-tert-
butylphenyl)-2-methyl-2-propenylidene]malononitrile in DCM
(1 mg/500 µL) was used as matrix.
The following compounds were prepared according to literature
procedures: 1,[17] 4, 5, 10,[22] 8 and TPP1,[23] TPP3,[34] 11 and
TPP4.[30] 2,2,7,7-Tetramethyloctane-4,5-dione was prepared simi-
larly to a published procedure[24] in 51% yield (yellow oil). 1H
NMR (300 MHz, CDCl3, 25 °C): δ = 0.99 (s, 18 H, CH3), 2.63 (s,
4 H, CH2) ppm. 13C NMR (75 MHz, CDCl3, 25 °C): δ = 29.6, 31.2,
46.8, 200.2 ppm.
Synthesis of Precursors
Dibutyl 6,7-Dicyanoquinoxaline-2,3-dicarboxylate (2): Dibutyl 2,3-
dioxosuccinate[23] (326.6 mg, 1.26 mmol) was dissolved in glacial
acetic acid (15 mL) and heated to reflux. 4,5-Diaminophthalo-
nitrile (1; 200 mg, 1.26 mmol) in THF (5 mL) was added and reflux
Eur. J. Org. Chem. 2010, 732–739
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
735

V. Novakova, P. Zimcik, M. Miletin, K. Kopecky, Z. Musil
FULL PAPER
was continued for 3 h. The crude product was purified by column
chromatography on silica (chloroform) to obtain a pale-yellow so-
was evaporated under reduced pressure, and the residue was ex-
tracted with chloroform and purified by column chromatography
lid (242.4 mg, 51%). M.p. 118.1–119.4 °C. 1H NMR (300 MHz, on silica (toluene), yielding a colourless oil that solidified after a
CDCl3, 25 °C): δ = 0.99 (t, J = 7.4 Hz, 6 H, CH3), 1.48 (sext., J =
while (200 mg, 37%). M.p. 96–97 °C. 1H NMR (300 MHz, CDCl3,
7.5 Hz, 4 H, CH2CH3), 1.82 (p, J = 7.1 Hz, 4 H, OCH2CH2), 4.50 25 °C): δ = 1.01 (s, 18 H, CH3), 3.09 (s, 4 H, CH2) ppm. 13C NMR
(t, J = 6.7 Hz, 4 H, OCH2), 8.72 (s, 2 H, ArH) ppm. 13C NMR (75 MHz, CDCl3, 25 °C): δ = 159.79, 129.51, 113.31, 46.89, 34.08,
(75 MHz, CDCl3, 25 °C): δ = 163.35, 147.79, 141.65, 137.30, 29.69 ppm. IR (KBr): ν = 3478, 2961, 2904, 2869, 2241, 1524, 1472,
˜
116.66, 114.15, 67.45, 30.35, 18.99, 13.63 ppm. IR (KBr): ν = 3468,
1430, 1396, 1378, 1320, 1229, 1199, 1129, 851, 670 cm–1. C16H22N4
˜
3096, 3067, 3045, 2961, 2937, 2875, 2239 (CN), 1747, 1471, 1435, (270.37): calcd. C 71.08, H 8.20, N 20.72; found C 71.03, H 8.64,
1360, 1336, 1279, 1220, 1195, 1135, 1073, 936 cm–1. C20H20N4O4 N 20.51.
(380.40): calcd. C 63.15, H 5.30, N 14.73; found C 63.99, H 5.74,
N 14.83.
5,6-Bis(2,6-diisopropylphenoxy)pyrazine-2,3-dicarbonitrile (12): 2,6-
Diisopropylphenol (446 mg, 2.5 mmol) was stirred for 15 min at
2,3-Dineopentylquinoxaline-6,7-dicarbonitrile (3): 4,5-Diaminoph-
thalonitrile (1; 632 mg, 4 mmol) was added to a stirred solution
of 2,2,7,7-tetramethyloctane-4,5-dione (400 mg, 2 mmol) in glacial
acetic acid (20 mL), and the mixture was heated at reflux for 9 h.
The solvent was evaporated, and the product was purified by col-
umn chromatography on silica (chloroform), yielding a white solid
(460 mg, 71%). M.p. 154–157 °C (MeOH). 1H NMR (300 MHz,
CDCl3, 25 °C): δ = 1.04 (s, 18 H, CH3), 3.10 (s, 4 H, CH2), 8.50 (s,
2 H, ArH) ppm. 13C NMR (75 MHz, CDCl3, 25 °C): δ = 161.04,
140.89, 136.66, 115.16, 113.20, 47.54, 34.08, 29.83 ppm. IR (KBr):
room temperature in 1  aqueous NaOH (2.4 mL, 2.4 mmol). 5,6-
Dichloropyrazine-2,3-dicarbonitrile[35] (200 mg, 1 mmol) in THF
(15 mL) was added dropwise, and the mixture was stirred for
15 min at room temperature. The crude product was concentrated
to dryness, and the brownish-yellow solid was washed thoroughly
with water and purified by column chromatography on silica (tolu-
ene/hexane, 1:1), yielding a white solid (404 mg, 83%). M.p. 208.5–
209.5 °C (MeOH) {ref.[25] m.p. 253 °C (n-hexane)}. 1H NMR
(300 MHz, CDCl3, 25 °C): δ = 7.39–7.24 (m, 6 H, aromH), 2.82
(sept., J = 7 Hz, 4 H, CH), 1.23 (d, J = 7 Hz, 24 H, CH3) ppm.
13C NMR (75 MHz, CDCl3, 25 °C): δ = 23.2, 28.0, 112.6, 124.2,
ν = 3447, 2965, 2903, 2866, 2240 (CN), 1556, 1473, 1398, 1366,
˜
1335, 1226, 1200, 1131 cm–1. C20H24N4 (320.43): calcd. C 74.97, H
7.55, N 17.48; found C 74.48, H 7.79, N 17.65.
124.6, 127.6, 139.8, 146.3, 151.1 ppm. IR (KBr): ν = 3068, 3032,
˜
2967, 2930, 2871, 2360, 2344, 2237, 1545, 1460, 1441, 1403, 1385,
1357, 1331, 1258, 1233, 1142, 1112, 1089, 1062, 937, 849, 793,
750 cm–1. C30H34N4O (482.62): calcd. C 74.66, H 7.10, N 11.61;
found C 74.40, H 7.31, N 11.99.
2,3-Bis(tert-butylsulfanyl)quinoxaline-6,7-dicarbonitrile (6): 2,3-
Dichloroquinoxaline-6,7-dicarbonitrile (4; 120 mg, 0.48 mmol) was
dissolved in THF (50 mL), and this solution was poured into a
solution of 2-methylpropan-2-thiol (104 mg, 1.2 mmol) in 1 
aqueous NaOH (1 mL). This solution was stirred for 15 min at
room temperature. The crude product was purified on silica (tolu-
ene/chloroform, 4:1) to gain a bright yellow solid (127 mg, 74%).
General Procedure for the Synthesis of Zinc(II) Tetra[6,7]quinoxal-
inoporphyrazines TQP1–4: Magnesium turnings and a small crystal
of iodine were heated at reflux for 3 h in anhydrous butanol. The
appropriate precursor (2, 3, 5 or 6) was added, and the reaction
mixture was heated at reflux for 3 h (TQP1 and TQP2) or 6 h
(TQP3 and TQP4). The mixture was left to cool down, and it was
then poured into water/methanol/acetic acid 5:5:1 (6:3:1 in the case
of TQP4) (30–100 mL) and stirred for 30 min at room temperature.
The precipitate (MgTQP) was collected. Purification of crude
MgTQP and demetallation to metal-free TQP is mentioned at each
compound preparation. Thereafter, metal-free TQP was dissolved
in pyridine, anhydrous zinc acetate in DMF was added and the
reaction mixture was heated at reflux for 2 h (6 h in the case of
TQP4). The mixture was concentrated under reduced pressure and
water was added. The solid was collected and purified by column
chromatography on silica (except TQP2 and TQP4). Mobile phases
are mentioned bellow.
1
M.p. 219–221 °C. H NMR (300 MHz, CDCl3, 25 °C): δ = 1.72 (s,
18 H, CH3), 8.25 (s, 2 H, ArH) ppm. 13C NMR (75 MHz, CDCl3,
25 °C):
δ = 161.82, 139.21, 134.44, 115.39, 112.10, 51.53,
29.74 ppm. IR (KBr): ν = 3522, 2996, 2964, 2923, 2904, 2864, 2621,
˜
2235 (CN), 1509, 1477, 1456, 1389, 1366, 1360, 1268, 1221, 1166,
1150, 1113, 1030, 899 cm–1. C18H20N4S2 (356.51): calcd. C 60.64,
H 5.65, N 15.72; found C 60.42, H 5.75, N 15.68.
2,3-Bis(2,6-diisopropylphenoxy)quinoxaline-6,7-dicarbonitrile
(7):
2,6-Diisopropylphenol (890 mg, 5 mmol) was added to 1  aqueous
NaOH (5 mL), and the mixture was stirred for 40 min at room
temperature. This solution was then dropped portionwise into a
THF (100 mL) suspension of 2,3-dichloroquinoxaline-6,7-dicar-
bonitrile (4; 470 mg, 1.9 mmol). The mixture was stirred at room
temperature for 70 min and THF was then evaporated. The suspen-
sion was diluted with water and filtered. Crude product was puri-
fied by column chromatography on silica (toluene) and recrys-
tallized from MeOH, yielding a white solid (570 mg, 56%). M.p.
2,3,11,12,20,21,29,30-Octakis(butoxycarbonyl)tetra[6,7]quinoxalino-
porphyrazine Zinc(II) (TQP1): This compound was prepared ac-
cording to general procedure mentioned above by using magnesium
(112 mg, 5.52 mmol) and compound 2 (250 mg, 0.79 mmol).
MgTQP1 was purified by column chromatography on silica (tolu-
ene/pyridine, 10:2) to obtain the Mg intermediate (93 mg,
0.060 mmol). This intermediate was dissolved in chloroform
(15 mL) and p-toluenesulfonic acid (180 mg, 1.05 mmol) in THF
(5 mL) was added; the solution was stirred for 45 min at room tem-
perature. The solvents were evaporated, and the product was thor-
oughly washed with water and acetone. Metallation was performed
according to the general procedure with metal-free TQP (47 mg,
0.031 mmol) and anhydrous zinc acetate (86 mg, 0.47 mmol). Mo-
bile phase toluene/pyridine, 5:1. Blue solid (41 mg, overall yield
16%). 1H NMR (300 MHz, CDCl3/[D5]pyridine, 25 °C): δ = 0.70
(br. s, 24 H, CH3), 1.26 (br. s, 16 H, CH2CH3), 1.59 (br. s, 16 H,
OCH2CH2), 4.28 (br. s, 16 H, OCH2), 9.01 (br. s, 8 H, ArH) ppm.
1
248.5–249.0 °C (MeOH). H NMR (300 MHz, CDCl3, 25 °C): δ =
1.23 (br. s, 24 H, CH3), 2.97 (sept., J = 6.7 Hz, 8 H, CH3CHCH3),
7.29–7.41 (m, 6 H, ArH), 8.08 (s, 2 H, ArH) ppm. 13C NMR
(75 MHz, CDCl3, 25 °C): δ = 151.67, 146.76, 140.13, 139.70,
133.37, 127.25, 124.46, 115.12, 112.36, 27.98, 23.55 ppm. IR (KBr):
ν = 3474, 2965, 2930, 2870, 2238 (CN), 1617, 1588, 1567, 1502,
˜
1456, 1393, 1363, 1346, 1330, 1252, 1230, 1211, 1173, 1157, 1144,
1092, 1062 cm–1. C34H36N4O2 (532.68): calcd. C 76.66, H 6.81, N
10.52; found C 76.44, H 7.06, N 10.57.
5,6-Dineopentylpyrazine-2,3-dicarbonitrile (9): 2,3-Diaminomaleo-
nitrile (848 mg, 8 mmol) was added to a stirred solution of 2,2,7,7-
tetramethyloctane-4,5-dione (400 mg, 2 mmol) in glacial acetic acid
(20 mL), and the mixture was heated at reflux for 9 h. The solvent
736
www.eurjoc.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2010, 732–739

Photophysical and Photochemical Properties of Enlarged Phthalocyanines
13C NMR (75 MHz, CDCl3/[D5]pyridine, 25 °C): δ = 163.74,
151.00, 143.71, 139.63, 137.87, 65.66, 29.73, 18.73, 12.91 ppm. IR
column chromatography on silica (chloroform/pyridine, 10:1) to
obtain a dark-green solid. MgTQP4 was dissolved in chloroform
(KBr): ν = 3448, 2959, 2930, 2873, 1726, 1450, 1401, 1374, 1286, (15 mL), p-toluenesulfonic acid (160 mg, 0.9 mmol) in THF (3 mL)
˜
1223, 1159, 1137, 1067, 1035 cm–1. UV/Vis (pyridine): λ (ε,
was added and the solution was stirred for 45 min at room tempera-
dm3 mol–1 cm–1) = 770 (247000), 729 (42300), 698 (39700), 367 ture. Insoluble light-green solid (metal-free TQP) was collected and
(96800), 324 (95100) nm. MS (MALDI-TOF): m/z = 1585 [M]+. washed thoroughly with various solvents (chloroform, toluene,
C80H80N16O16Zn·3H2O (1587.00 + 3ϫ18.01): calcd. C 58.55, H
5.3, N 13.66; found C 58.49, H 5.2, N 13.61.
tetrahydrofuran, diethyl ether, hexane, ethanol, water, methanol,
ethyl acetate and pyridine). Metallation was performed according
to the general procedure with metal-free TQP (86 mg, 0.06 mmol)
and anhydrous zinc acetate (570 mg, 3.1 mmol). The crude product
was washed thoroughly with water, methanol and hexane, yielding
a dark green solid (33 mg, overall yield 16%). 1H NMR (300 MHz,
CDCl3/[D5]pyridine, 25 °C): δ = 1.96 (br. s, 72 H, CH3), 9.61 (s, 8
H, ArH) ppm. 13C NMR (75 MHz, CDCl3/[D5]pyridine, 25 °C): δ
= 156.62, 153.48, 139.11, 136.74, 121.36, 50.40, 30.26 ppm. IR
2,3,11,12,20,21,29,30-Octa(neopentyl)tetra[6,7]quinoxalinoporphyr-
azine Zinc(II) (TQP2): This compound was prepared according to
general procedure mentioned above by using magnesium (30 mg,
1.4 mmol) and compound 3 (65 mg, 0.2 mmol). MgTQP2 precipi-
tated from the solvent during cyclotetramerization and was col-
lected by filtration, washed thoroughly with water, methanol and
dichloromethane and recrystallized from hot DMF. Purple needles
were collected and washed with DMF and ethanol, yielding 16 mg
of a purple solid of magnesium complex. This intermediate (16 mg,
0.012 mmol) was suspended in DMF and heated at 180 °C and p-
toluenesulfonic acid (50 mg, 0.26 mmol) in DMF (2 mL) was
added. After 10 min of heating, the solution was left to cool down,
diluted with water (10 mL) and stirred for 30 min at room tempera-
ture. The green precipitate (metal free TQP) was collected and
washed with water and methanol. Metallation was performed ac-
cording to the general procedure with metal-free TQP (15 mg,
0.012 mmol) and zinc acetate (50 mg, 0.27 mmol). The solution was
concentrated under reduced pressure, diluted with water and the
blue precipitate was collected and recrystallized from hot DMF,
(KBr): ν = 3447, 2961, 2920, 2860, 2361, 1719, 1516, 1457, 1362,
˜
1337, 1252, 1123, 1018, 892 cm–1. UV/Vis (pyridine): λ (ε,
dm3 mol–1 cm–1) = 754 (509800), 717 (60000), 674 (64200), 383
(183200) nm. MS (MALDI-TOF): m/z = 1488 [M]+, 1432 [M –
C4H9]+, 1376 [M – 2C4H9]+, 1320 [M – 3C4H9]+, 1264 [M –
4C4H9]+. C72H80N16S8Zn·3H2O (1491.44 + 3ϫ18.01): calcd. C
55.95, H 5.6, N 14.50; found C 55.79, H 5.7, N 14.45.
2,3,11,12,20,21,29,30-Octakis(2,6-diisopropylphenoxy)tetra[6,7]quin-
oxalinoporphyrazine Zinc(II) (TQP5): Precursor 7 (500 mg,
0.94 mmol) and Zn(quinoline)2Cl2 (370 mg, 0.94 mmol, prepared
according to the literature[28]) were mixed and heated at 310 °C
under an atmosphere of argon for 1 h. The product was washed
with methanol/water/acetic acid (5:5:1) and purified by column
chromatography on silica (toluene/hexane/pyridine, 100:30:1). Iso-
lated product was washed with methanol, yielding a pale green so-
lid (120 mg, 23%). 1H NMR (300 MHz, CDCl3, 25 °C): δ = 1.45
(s, 96 H, CH3), 3.63 (sept., J = 6.8 Hz, 16 H, CH3CHCH3), 7.48–
yielding a blue solid (11 mg, overall yield 16%). IR (KBr): ν =
˜
3420, 2954, 2904, 2966, 1654, 1474, 1449, 1380, 1365, 1329, 1305,
1230, 1190, 1149, 1083, 1047, 1025, 896 cm–1. UV/Vis (pyridine): λ
(ε, dm3 mol–1 cm–1) = 750 (173800), 712 (20800), 671 (22500), 365
( 5 6 6 0 0 ) n m . M S ( M A L D I - T O F ) : m / z = 1 3 4 5 [ M ] +
.
C80H96N16Zn·3H2O (1347.14 + 3ϫ18.01): calcd. C 68.57, H 7.30, 7.58 (m, 24 H, ArH), 9.88 (s, 8 H, ArH) ppm. 13C NMR (75 MHz,
N 15.99; found C 68.61, H 7.20, N 16.03. The solubility of TQP2
CDCl3, 25 °C): δ = 153.78, 148.24, 141.36, 139.30, 137.58, 127.74,
was not sufficient for NMR analyses.
125.32, 121.37, 28.54, 24.00, 23.19 ppm. IR (KBr): ν = 3433, 2964,
˜
2930, 2870, 1421, 1324, 1229, 1183, 1164, 1145, 1092, 1041 cm–1.
UV/Vis (pyridine): λ (ε, dm3 mol–1 cm–1) = 730 (410800), 695
(49800), 654 (55800), 371 (148200), 322 (76400) nm. MS (MALDI-
TOF): m/z = 2193 [M]+. C136H144N16O8Zn·3H2O (2196.11 +
3ϫ18.01): calcd. C 72.59, H 6.7, N 9.96; found C 72.63, H 6.7, N
10.05.
2,3,11,12,20,21,29,30-Octakis(diethylamino)tetra[6,7]quinoxalino-
porphyrazine Zinc(II) (TQP3): This compound was prepared ac-
cording to the general procedure mentioned above by using magne-
sium (10 mg, 0.43 mmol) and compound 5 (20 mg, 0.062 mmol).
MgTQP3 was sufficiently pure for further reaction; thus, it was
dissolved in chloroform (10 mL), trifluoroacetic acid (205 mg,
1.8 mmol) was added and the solution was stirred for 3 h at room
temperature. The solvent was evaporated, and the product was
thoroughly washed with water. Metallation was performed accord-
ing to the general procedure with metal-free TQP (7 mg, 5.4 µmol)
and anhydrous zinc acetate (7 mg, 0.04 mmol). Mobile phase tolu-
ene/pyridine, 10:1. Brown-green solid (3 mg, overall yield 14%). 1H
NMR (300 MHz, CDCl3/[D5]pyridine, 25 °C): δ = 9.45 (br. s, 8 H,
ArH), 3.40 (q, J = 7 Hz, 32 H, NCH2), 0.86 (t, J = 7 Hz, 48 H,
CH3) ppm. 13C NMR (75 MHz, CDCl3/[D5]pyridine, 25 °C): δ =
Synthesis of Zinc(II) Tetrapyrazinoporphyrazines (TPP)
2,3,9,10,16,17,23,24-Octakis(neopentyl)-1,4,8,11,15,18,22,25-(octa-
aza)phthalocyanine Zinc(II) (TPP2): Magnesium turnings (24 mg,
1.0 mmol) and a small crystal of iodine were heated at reflux for
3 h in anhydrous butanol (10 mL). Compound 9 (38 mg,
0.14 mmol) was added, and the reaction mixture was heated at re-
flux for 14 h. The mixture was left to cool down, poured into 50%
(v/v) acetic acid (100 mL) and stirred for 30 min at room tempera-
ture. The precipitate was collected, washed with 5% v/v NaHCO3,
water and methanol to obtain 35 mg of magnesium complex of
TPP. This intermediate was stirred in THF (15 mL) with p-tolu-
enesulfonic acid (52 mg) for 4 h at room temperature. The solvent
was evaporated, and the product was thoroughly washed with
water. This metal-free TPP (30 mg) was then dissolved in chloro-
form, anhydrous zinc acetate (51 mg) in DMF was added, and the
mixture was heated at reflux for 4 h. The mixture was concentrated
and water was added. A blue solid was collected, washed with water
and methanol and purified by column chromatography on silica
(chloroform/ethyl acetate, 20:3) to obtain a blue solid (24 mg,
60%). 1H NMR (300 MHz, pyridine, 25 °C): δ = 1.25 (s, 72 H,
CH3), 3.65 (s, 16 H, CH2) ppm. 13C NMR (75 MHz, pyridine,
11.9, 42.1, 118.7, 120.6, 138.1, 147.4, 153.0 ppm. IR (KBr): ν =
˜
2960, 2922, 2852, 1757, 1713, 1541, 1426, 1338, 1286, 1247, 1158,
1141, 1118, 1090, 1023 cm–1. MS (MALDI-TOF): m/z = 1352
[M]+. UV/Vis (pyridine): λ (ε, dm3 mol–1 cm–1) = 754 (223600), 718
(30700), 673 (33700), 387 (115300) nm.
2,3,11,12,20,21,29,30-Octakis(tert-butylsulfanyl)tetra[6,7]quinoxal-
inoporphyrazine zinc(II) (TQP4): This compound was prepared ac-
cording to the general procedure mentioned above by using magne-
sium (95.3 mg, 3.92 mmol) and compound 6 (200 mg, 0.56 mmol).
MgTQP4 was collected and washed thoroughly with water and
methanol. The crude product was adsorbed to silica, washed thor-
oughly on a glass frit with methanol, dried and then purified by
Eur. J. Org. Chem. 2010, 732–739
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
737

V. Novakova, P. Zimcik, M. Miletin, K. Kopecky, Z. Musil
FULL PAPER
25 °C): δ = 157.53, 152.32, 148.38, 48.03, 34.36, 30.24 ppm. IR
(KBr): ν = 2949, 2927, 2857, 1734, 1636, 1549, 1496, 1459, 1359, [1] M. E. Osugi, P. A. Carneiro, M. V. B. Zanoni, J. Braz. Chem.
˜
1346, 1278, 1238, 1195, 1139, 1093, 1045, 1024 cm–1. UV/Vis (pyr-
idine): λ (ε, dm3 mol–1 cm–1) = 642 (227400), 583 (30200), 356
(111800) nm. MS (MALDI-TOF): m/z = 1144 [M]+. C64H88N16Zn
(1146.90): calcd. C 64.98, H 7.84, N 18.95; found C 65.38, H 8.16,
N 17.56.
Soc. 2003, 14, 660–665.
[2] P. Erk, H. Hengelsberg in The Porphyrin Handbook (Eds.:
K. M. Kadish, K. M. Smith, R. Guilard), Academic Press, San
Diego, 2000, vol. 19, pp. 105–149.
[3] M. Kandaz, M. N. Yarasir, T. Guney, A. Koca, J. Porphyrins
Phthalocyanines 2009, 13, 712–721.
[4] R. P. Hammer, C. V. Owens, S. H. Hwang, C. M. Sayes, S. A.
Soper, Bioconjugate Chem. 2002, 13, 1244–1252.
[5] Ö. A. Osmanbas, A. Koca, I. Özçesmeci, A. I. Okur, A. Gül,
Electrochim. Acta 2008, 53, 4969–4980.
[6] D. Wöhrle, O. Suvorova, R. Gerdes, O. Bartels, L. Lapok, N.
Baziakina, S. Makarov, A. Slodek, J. Porphyrins Phthalocyan-
ines 2004, 8, 1020–1041.
[7] H. Li, T. J. Jensen, F. R. Fronczek, M. G. Vicente, J. Med.
Chem. 2008, 51, 502–511.
[8] M. Quintilani, A. Kahnt, T. Wölfle, W. Hieringer, P. Vázquez,
A. Görling, D. M. Guldi, T. Torres, Chem. Eur. J. 2008, 14,
3765–3775.
2,3,9,10,16,17,23,24-Octakis(diethylamino)-1,4,8,11,15,18,22,25-(oc-
taaza)phthalocyanine Zinc(II) (TPP3): This compound was pre-
pared according to the published procedure.[34] UV/Vis (pyridine):
λ (ε, dm3 mol–1 cm–1) = 664 (183100), 604 (36400), 521 (39800), 385
(138600) nm.
2,3,9,10,16,17,23,24-Octakis(2,6-diisopropylphenoxy)-1,4,8,11,
15,18,22,25-(octaaza)phthalocyanine Zinc(II) (TPP5): Zn(quin-
oline)2Cl2 (246 mg, 0.6 mmol, prepared according to the litera-
ture[28]) and 12 (300 mg, 0.6 mmol) were mixed and heated at
260 °C under reflux for 90 min. The product was washed thor-
oughly with methanol/water (1:1) and purified by column
chromatography on silica (toluene/chloroform/THF/pyridine,
15:15:1:1) to obtain a green solid (85 mg, 27%). 1H NMR
(300 MHz, CDCl3, 25 °C): δ = 7.58 (t, J = 7 Hz, 8 H, aromH), 7.45
(d, J = 8 Hz, 16 H, aromH), 3.32 (sept., J = 7 Hz, 16 H, CH), 1.30
(d, J = 7 Hz, 96 H, CH3) ppm. 13C NMR (75 MHz, CDCl3, 25 °C):
δ = 23.5, 28.1, 124.4, 126.6, 141.0, 142.4, 147.9, 149.7, 151.5 ppm.
[9] K. Walzer, B. Maennig, M. Pfeiffer, K. Leo, Chem. Rev. 2007,
107, 1233–1271.
[10] N. Kobayashi, H. Ogata, N. Nonaka, E. A. LukЈyanets, Chem.
Eur. J. 2003, 9, 5123–5134.
[11] N. Kobayashi, S.-i. Nakajima, H. Ogata, T. Fukuda, Chem.
Eur. J. 2004, 10, 6294–6312.
[12] S. G. Makarov, O. N. Suvorova, C. Litwinski, E. A. Ermilov,
B. Röder, O. Tsaryova, T. Dülcks, D. Wöhrle, Eur. J. Inorg.
Chem. 2007, 546–552.
IR (KBr): ν = 3065, 1965, 2931, 2870, 1541, 1401, 1294, 1249,
˜
1213, 1161, 1145, 1094, 1059, 929 cm–1. UV/Vis (pyridine): λ (ε,
dm3 mol–1 cm–1) = 628 (200200), 571 (27700), 372 (117600) nm. MS
(MALDI-TOF): m/z = 1993 [M + H]+. C120H136N16O8Zn·5H2O
(1995.88 + 5ϫ18.01): calcd. C 68.50, H 7.09, N 10.65; found C
68.55, H 6.13, N 10.78.
[13] M. T. M. Choi, P. P. S. Li, D. K. P. Ng, Tetrahedron 2000, 56,
3881–3887.
[14] Y.-O. Yeung, R. C. W. Liu, W.-F. Law, P.-L. Lau, J. Jiang,
D. K. P. Ng, Tetrahedron 1997, 53, 9087–9096.
[15] F. Mitzel, S. FitzGerald, A. Beeby, R. Faust, Chem. Eur. J.
2003, 9, 1233–1241.
[16] F. Mitzel, S. FitzGerald, A. Beeby, R. Faust, Chem. Commun.
2001, 2596–2597.
[17] W. J. Youngblood, J. Org. Chem. 2006, 71, 3345–3356.
[18] Z. Iqbal, A. Lyubimtsev, M. Hanack, Synlett 2008, 2287–2290.
[19] C. Burmester, R. Faust, Synthesis 2008, 1179–1181.
[20] M. Haas, S. X. Liu, A. Neels, S. Decurtins, Eur. J. Org. Chem.
2006, 5467–5478.
[21] P. Zimcik, M. Miletin, M. Kostka, J. Schwarz, Z. Musil, K.
Kopecky, J. Photochem. Photobiol. A: Chem. 2004, 163, 21–28.
[22] Z. Musil, P. Zimcik, M. Miletin, K. Kopecky, J. Lenco, Eur. J.
Org. Chem. 2007, 4535–4542.
Singlet Oxygen and Fluorescence Quantum Yields: Quantum yields
of singlet oxygen formation (Φ∆) were determined in pyridine ac-
cording to a previously published procedure[36] using the decompo-
sition of 1,3-diphenylisobenzofuran (DPBF). Zinc phthalocyanine
(ZnPc) was used as a reference (Φ∆ = 0.61 in pyridine[37]). Absorp-
tion of the dyes in the Q-band area was set approximately to 0.1.
Fluorescence quantum yields (ΦF) were determined in pyridine by
the comparative method using ZnPc as a reference (ΦF = 0.20 in
pyridine[37]). Absorption of the dyes in the Q-band was always be-
low 0.05. The fluorescence quantum yields were calculated accord-
ing to Equation (1).
[23] Z. Musil, P. Zimcik, M. Miletin, K. Kopecky, P. Petrik, J.
Lenco, J. Photochem. Photobiol. A: Chem. 2007, 186, 316–322.
[24] F. Babudri, V. Fiandanese, G. Marchese, A. Punzi, Tetrahedron
Lett. 1995, 36, 7305–7308.
[25] S. Makhseed, J. Samuel, F. Ibrahim, Tetrahedron 2008, 64,
8871–8877.
(1)
[26] S. Makhseed, F. Ibrahim, C. G. Bezzu, N. B. McKeown, Tetra-
hedron Lett. 2007, 48, 7358–7361.
[27] E. H. Mørkved, H. Ossletten, H. Kjøsen, Acta Chem. Scand.
1999, 53, 1117–1121.
[28] E. H. Mørkved, N. K. Afseth, H. Kjøsen, J. Porphyrins Phthal-
ocyanines 2006, 10, 1301–1308.
where F is the integrated area under the emission spectrum, A is
absorbance at excitation wavelength. Superscripts R and S corre-
spond to the reference and sample, respectively. Excitation wave-
length was 370 nm.
[29] E. H. Mørkved, T. Andreassen, P. Bruheim, Polyhedron 2009,
28, 2635–2640.
Supporting Information (see footnote on the first page of this arti-
cle): Additional absorption, fluorescence emission and fluorescence
excitation spectra.
[30] M. Kostka, P. Zimcik, M. Miletin, P. Klemera, K. Kopecky, Z.
Musil, J. Photochem. Photobiol. A: Chem. 2006, 178, 16–25.
[31] P. Zimcik, V. Novakova, M. Miletin, K. Kopecky, Macrohetero-
cycles 2008, 1, 21–29.
[32] S. V. Kudrevich, J. E. Van Lier, Coord. Chem. Rev. 1996, 156,
Acknowledgments
163–182.
[33] V. Novakova, P. Zimcik, K. Kopecky, M. Miletin, J. Kunes, K.
ˇ
Financial support from the Czech Science Foundation (203/07/
P445) under Research project MSM0021620822 is gratefully ac-
knowledged.
Lang, Eur. J. Org. Chem. 2008, 3260–3263.
[34] P. Petrik, P. Zimcik, K. Kopecky, Z. Musil, M. Miletin, V. Lou-
kotova, J. Porphyrins Phthalocyanines 2007, 11, 487–495.
738
www.eurjoc.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2010, 732–739

Photophysical and Photochemical Properties of Enlarged Phthalocyanines
[35] E. H. Mørkved, L. T. Holmaas, H. Kjøsen, G. Hvistendahl,
Acta Chem. Scand. 1996, 50, 1153–1156.
[37]
A. Ogunsipe, D. Maree, T. Nyokong, J. Mol. Struct. 2003, 650,
131–140.
[36] Z. Musil, P. Zimcik, M. Miletin, K. Kopecky, M. Link, P. Pe-
trik, J. Schwarz, J. Porphyrins Phthalocyanines 2006, 10, 122–
131.
Received: October 12, 2009
Published Online: December 18, 2009
Eur. J. Org. Chem. 2010, 732–739
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
739