Highly soluble 7-oxy-3-(4-methoxyphenyl)coumarin bearing zinc phthalocyanines: Synthesis and investigation of photophysical and photochemical properties

Article abstract of DOI:10.1016/j.jphotochem.2011.07.014

The synthesis of 7-oxy-3-(4-methoxyphenyl)coumarin-substituted peripherally and non-peripherally tetrakis- and peripherally octakis-tetrachloro zinc(II) phthalocyanine complexes are described for the first time in this study. The new compounds have been c

Full text of DOI:10.1016/j.jphotochem.2011.07.014

Journal of Photochemistry and Photobiology A: Chemistry 223 (2011) 37–49
Contents lists available at ScienceDirect
Journal of Photochemistry and Photobiology A:
Chemistry
journal homepage: www.elsevier.com/locate/jphotochem
Highly soluble 7-oxy-3-(4-methoxyphenyl)coumarin bearing zinc
phthalocyanines: Synthesis and investigation of photophysical and
photochemical properties
Mehmet Pis¸ kina, Mahmut Durmus¸ b, Mustafa Buluta,∗
a Marmara University, Faculty of Art and Science, Department of Chemistry, 34722 Kadikoy-Istanbul, Turkey
b Gebze Institute of Technology, Department of Chemistry, P.O. Box 141, Gebze 41400, Kocaeli, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 11 May 2011
Received in revised form 13 July 2011
Accepted 23 July 2011
Available online 30 July 2011
The synthesis of 7-oxy-3-(4-methoxyphenyl)coumarin-substituted peripherally and non-peripherally
tetrakis- and peripherally octakis-tetrachloro zinc(II) phthalocyanine complexes are described for the
first time in this study. The new compounds have been characterized by elemental analysis, IR, 1H NMR,
UV–vis spectroscopy and mass spectra. The photophysical and photochemical properties are impor-
tant for photodynamic therapy applications and these properties of studied phthalocyanine complexes
are investigated in N,N-dimethyl formamide (DMF). The effects of the number of the substitution and
the position (peripheral or non-peripheral) on the photophysical and photochemical parameters of the
zinc(II) phthalocyanine complexes are reported. The fluorescence quenching behaviour of the studied
zinc(II) phthalocyanine complexes by the addition of 1,4-benzoquinone are also described.
© 2011 Elsevier B.V. All rights reserved.
Keywords:
Phthalocyanine
Coumarin (2H-chromen-2-one)
Zinc
Fluorescence
Quantum yield
Singlet oxygen
1. Introduction
containing ortho-dihydroxy substituents [10]. Also, the chemical-
structure/biological activity study of the coumarins showed that
As an important group of organic heterocyclic compounds,
coumarin (2H-1-benzopyran-2-one) and its derivatives, have
been extensively exploited in biological, chemical and physical
fields. Coumarins have outstanding optical properties, includ-
ing an extended spectral range, superior photostability and
good solubility in common solvents. Many natural and synthetic
coumarin derivatives are widely used as laser dyes [1]. The med-
ical properties of the coumarins include inhibitions of platelet
aggregation and steroid 5-reductase, antibacterial, anticancer and
anti HIV-1 activities have been studied [2]. 7-Hydroxycoumarin
derivatives have been reported to inhibit the proliferation of a
number of human malignant cell lines in vitro [3,4] and have
demonstrated activity against several types of animal tumors
[5–7]. These compounds have also been reported in clinical
trials to demonstrate activity against prostate cancer, malig-
nant melanoma, and metastatic renal cell carcinoma [8,9]. For
coumarins, generally the in vitro structure–activity relationship
studies have shown that cytotoxicity is found with derivatives
the addition of a cathecolic group to the basic structure induces
increased cytotoxic activity in tumor cell lines [10]. The different
cytotoxic values found for the coumarins could be related to the
presence and the positions of the hydroxyl groups in their struc-
tures.
Phthalocyanines (Pcs) and related macrocyclic compounds have
found widespread application in various areas including liquid
crystals, non-linear optical devices, catalysts, electrochromic and
photochromic materials, chemical sensors, data storage systems,
organic photovoltaics in solar cells [11,12] and second generation
photosensitizers for photodynamic therapy (PDT) [13].
Numerous studies have been carried out to modify these macro-
cyclic compounds with the goal of moderating their properties
and optimizing their performance for advanced materials. A deci-
sive disadvantage of metal free phthalocyanines (Pcs) and metallo
phthalocyanines (MPcs) is their low solubility in organic sol-
vents or water. While the solubility in organic solvents can be
increased by introducing alkyl or alkoxy groups [14], the solubility
in aqueous solutions can also be increased by introducing sul-
fonates, carboxylates, phosphanates or quaternized amino groups
into the peripheral and non-peripheral positions of the phthalo-
cyanine framework [15]. In contrast to octa-substituted systems,
tetra-substituted phthalocyanines are obtained as a mixture of
∗
Corresponding author. Tel.: +90 216 3479641 1370; fax: +90 216 3478783.
E-mail addresses: mbulut@marmara.edu.tr, mustafabulut50@gmail.com
(M. Bulut).
1010-6030/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jphotochem.2011.07.014

38
M. Pis¸kin et al. / Journal of Photochemistry and Photobiology A: Chemistry 223 (2011) 37–49
constitutional isomers by statistical synthesis starting from cor-
responding mono-substituted phthalonitriles or corresponding
diiminoisoindolines. Depending on their substituent positions two
types (non-peripherally and peripherally substituted) of tetra-
substituted macrocycles which show significant differences in their
chemical and physical behaviour can be obtained.
(4) [40] were synthesized and purified according to well-
known literature procedures. Then starting materials 5,
and were obtained by the reaction of 7-hydroxy-3-(4-
6
7
methoxyphenyl)coumarin (1) with 2, 3 and 4, respectively.
2.2. Measurements
Recently, there has been considerable interest in the
tetrapyrrolic photosensitizers by Dudkowiak et al. [16–20].
Pc complexes which are a class of the tetrapyrrolic photosensitiz-
ers have found applications as photosensitizers in PDT as second
generation photosensitizers [21,22]. The zinc(II) Pc complexes have
attracted much interest because of their appreciably long triplet
lifetimes [23–25], high selectivity for tumoral targets and enhanced
cytotoxic efficiency due to singlet oxygen photogeneration [23].
Addition of groups to the peripheral positions of MPc com-
plexes is known to influence the properties of the MPc to a large
degree [26–30]. For instance, the peripheral substituents increase
the distance between the planar macrocycle rings carrying the
␲-electrons thereby making solvation easier. Solvents affect aggre-
gation in Pc complexes. Organic solvents are known to reduce
aggregation whereas aqueous medium results in highly aggregated
complexes. However, many Pc complexes remain aggregated even
in non-aqueous solutions [31–33]. Aromatic solvents such as ben-
zene or toluene are known to give narrow Q-bands for Pc complexes
whereas broadening is observed in non-aromatic solvents [34].
The zinc(II) Pc complexes show fascinating photophysical and
photochemical properties especially high singlet oxygen quantum
yields which are very important for PDT of cancer. In this study,
the studied zinc(II) phthalocyanine complexes have good singlet
oxygen quantum yields and show potential as Type-II photosen-
sitizers. In this work, we report on the effects of the coumarin
groups as substituent and the position of the substituent (periph-
eral or non-peripheral) on the photophysical and photochemical
parameters. Aggregation behaviour, photophysical (fluorescence
lifetime and quantum yields) and photochemical (singlet oxygen
generation and photodegradation quantum yields) properties are
investigated in this study. This work also explores the effects of
ring substitutions and position on the fluorescence quenching of
zinc Pc by 1,4-benzoquinone (BQ) using the Stern–Volmer rela-
tionship. Since PDT activity is mainly based on singlet oxygen, its
production is determined by the dye-sensitized photooxidation
of 1,3-diphenylisobenzofuran (DPBF), a specific scavenger of this
toxic species [35]. Studies of the photostability of zinc Pc com-
plexes during photosensitization reactions are also of immense
importance. Herein, we report the synthesis, spectroscopic, pho-
tophysical and photochemical properties of novel zinc Pcs with
7-oxy-3-(4-methoxyphenyl)coumarin (Scheme 1).
Absorption spectra in the UV–visible region were recorded with
a Shimadzu 2001 UV spectrophotometer. Fluorescence excitation
and emission spectra were recorded on a Varian Eclipse spectroflu-
oremeter using 1 cm pathlength cuvettes at room temperature. IR
spectra (KBr pellets) were recorded on a Bio-Rad FTS 175C FTIR
spectrometer. Elemental analyses carried out using a LECO CHN
932 was performed by the Instrumental Analysis Laboratory of
TUBITAK Ankara Test and Analysis Laboratory. Mass spectra were
performed on a Bruker Autoflex III MALDI-TOF spectrometer. A 2,5-
dihydroxybenzoic acid (DHB, 20 mg/mL in THF) was used as matrix.
MALDI samples were prepared by mixing the complex (2 mg/mL
in THF) with the matrix solution (1:10 v/v) in a 0.5 mL Eppendorf
micro tube. Finally, 1 ␮L of this mixture was deposited on the sam-
ple plate, dried at room temperature and then analyzed. 1H NMR
spectra were recorded in CDCl3 on a Varian 500 MHz spectrometer.
Photo-irradiations were done using a General Electric quartz
line lamp (300 W). A 600 nm glass cut off filter (Schott) and a
water filter were used to filter off ultraviolet and infrared radia-
tions respectively. An interference filter (Intor, 670 nm with a band
width of 40 nm) was additionally placed in the light path before the
sample. Light intensities were measured with a POWER MAX5100
(Molelectron detector incorporated) power meter.
2.3. Photophysical parameters
2.3.1. Fluorescence quantum yields and lifetimes
Fluorescence quantum yields (˚F) were determined by the com-
parative method using Eq. (1) [41],
F · AStd · n2
˚
F
= ˚F(Std)
(1)
FStd · A · n2
Std
where F and FStd are the areas under the fluorescence emission
curves of the samples (8–10) and the standard, respectively. A and
AStd are the respective absorbances of the samples and standard
at the excitation wavelengths, respectively. n2 and nS2td are the
refractive indices of solvents used for the sample and standard,
respectively. Unsubstituted ZnPc (in DMSO) (˚F = 0.20) [42] was
employed as the standard. Both the samples and standard were
excited at the same wavelength. The absorbance of the solutions at
the excitation wavelength ranged between 0.04 and 0.05.
Natural radiative (ꢀ0) lifetimes were determined using Pho-
tochemCAD program which uses the Strickler–Berg equation
[43,44]. The fluorescence lifetimes (ꢀF) were evaluated using Eq.
(2).
2. Experimental
2.1. Materials
ꢀF
˚
F
=
(2)
All reagents and solvents were of reagent grade quality
and were obtained from commercial suppliers. All solvents
were purified as described in Perrin and Armarego before
use [36]. Zinc(II) acetate dihydrate, K2CO3 and unsubsti-
tuted zinc phthalocyanine were purchased from the Aldrich
Chemical Company. 1,3-Diphenylisobenzofuran (DPBF) was pur-
chased from Fluka. Silica gel was purchased from Merck.
7-Hydroxy-3-(4-methoxyphenyl)coumarin (1) was prepared by
Perkin condensation of p-methoxyphenylacetic acid with 2,4-
dihydroxybenzaldehyde in acetic anhydride in the presence of
NaOAc as the base [37] with subsequent deacylation of the 7-
acetoxy-3-(4-methoxyphenyl)coumarin. 4-Nitrophthalonitrile (2)
[38], 3-nitrophthalonitrile (3) [39], and 4,5-dichlorophthalonitrile
ꢀ0
2.4. Photophysical parameters
2.4.1. Singlet oxygen quantum yields
Singlet oxygen (˚ꢁ) quantum yield determinations were car-
ried out using the experimental set-up described in literature [45],
in DMF. Typically, a 3 mL portion of the respective substituted
zinc(II) Pc (8–10) solutions (C = 1 × 10−5 M) containing the singlet
oxygen quencher was irradiated in the Q band region with the
photo-irradiation set-up described in references [45]. Singlet oxy-
gen quantum yields (˚ꢁ) were determined in air using the relative
method with unsubstituted ZnPc (in DMF) as reference. DPBF was

M. Pis¸kin et al. / Journal of Photochemistry and Photobiology A: Chemistry 223 (2011) 37–49
39
OR
N
N
N
O
O
OH
O2N
CN
CN
RO
CN
CN
ii
i
N
N
RO
OR
Zn
N
N
N
1
2
5
H3CO
OR
8
OR
RO
NO2
N
N
OR
N
O
O
OH
CN
CN
CN
CN
ii
i
N
N
Zn
N
N
N
OR
H3CO
3
1
6
RO
9
Cl
OR
N
N
N
N
N
N
O
O
OH
RO
Cl
Cl
Cl
CN
CN
Cl
OR
RO
Cl
CN
CN
ii
i
N
Zn
N
H3CO
4
1
7
RO
Cl
10
O
O
R=
H3CO
Scheme 1. Synthesis of tetra- and chloro-octa-(7-oxy-3-(4-methoxyphenyl)coumarin)-substituted zinc(II) phthalocyanine complexes (8–10). (i) DMF, K2CO3, RT; (ii) DMAE,
Zn(OAc)2·2H2O, reflux.
used as chemical quenchers for singlet oxygen in DMF. Eq. (3) was
employed for the calculations:
setup described above. DPBF degradation at 417 nm was monitored.
The light intensity 6.60 × 1015 photons s−1 cm−2 was used for ˚ꢁ
determinations.
Std
R · I
abs
RStd · Iabs
˚
= ˚Std
(3)
ꢁ
ꢁ
2.4.2. Photodegradation quantum yields
Photodegradation quantum yield (˚d) determinations were
carried out using the experimental set-up described in literature
[45]. Photodegradation quantum yields were determined using Eq.
(4),
where ˚Sꢁtd is the singlet oxygen quantum yield for the standard
unsubstituted ZnPc (˚ꢁStd = 0.56 in DMF) [42]. R and RStd are the
DPBF photobleaching rates in the presence of the respective sam-
Std
abs
ples (8–10) and standards, respectively. Iabs and I
are absorbed
(C0 − Ct) · V · NA
˚
=
(4)
light by the samples (8–10) and standards, respectively. To avoid
chain reactions induced by DPBF in the presence of singlet oxygen
[46], the concentration of quenchers was lowered to ∼3 × 10−5 M.
Solutions of sensitizer (C = 1 × 10−5 M) containing DPBF was pre-
pared in the dark and irradiated in the Q band region using the
d
Iabs · S · t
where C0 and Ct are the samples (8–10) before and after irradia-
tion respectively, V is the reaction volume, NA is the Avogadro’s
constant, S is the irradiated cell area, t is the irradiation time

40
M. Pis¸kin et al. / Journal of Photochemistry and Photobiology A: Chemistry 223 (2011) 37–49
and Iabs is the overlap integral of the radiation source light inten-
sity and the absorption of the samples (8–10). A light intensity
of 2.20 × 1016 photons s−1 cm−2 was employed for ˚d determina-
tions.
accomplished by column chromatography with silica gel using
dichloromethane/methanol (20/1) as eluent. The compound (6)
is soluble in chloroform (CHCl3), dichloromethane, THF, DMF and
DMSO. Yield: 0.61 g (76%). M.p.: 123 ◦C. FT-IR [(KBr) ꢂmax/cm−1]:
3096 (Ar–CH), 2955–2840 (CH), 2239 (C N), 1718 (C O lactone),
1608 and 1470 (C C), 1281 (Ar–O–Ar). 1H NMR (CDCl3): ı, ppm:
Aromatic protons: 7.95 (d, 6.83 Hz, 1H), 7.94 (d, 8,30 Hz, 1H), 7.88
(t, 1H), 7.86 (d, 7.56 Hz, 1H), 7.7 (d, 7.57 Hz, 2H), 7.55 (d, 8.30 Hz,
1H), 7.36 (s, 1H), 7.02 (d, 7.57 Hz, 2H), aliphatic protons: 8.24 (s,
1H, CH), 3.81 (s, 3H, –OCH3). Anal. Calc. for C24H14N2O4 (394.38):
C, 73.09; H, 3.58; N, 7.10%; Found: C, 72.88; H, 3.48; N, 6.96%. MS
(MALDI-TOF) m/z: 394.89 [M]+.
2.4.3. Fluorescence quenching by 1,4-benzoquinone (BQ)
Fluorescence quenching experiments on the substituted ZnPc
complexes (8–10) were carried out by the addition of different con-
centrations of BQ to a fixed concentration of the complexes, and
the concentrations of BQ in the resulting mixtures were 0, 0.008,
0.016, 0.024, 0.032 and 0.040 mol dm−3. The fluorescence spectra of
substituted ZnPc complexes (8–10) at each BQ concentration were
recorded, and the changes in fluorescence intensity related to BQ
concentration by the Stern–Volmer (SV) equation [47] (Eq. (5)):
2.5.3. 4-Chloro-5-[3-(4-methoxyphenyl)-2H-chromen-7-yloxy]
phthalonitrile (7)
I0
= 1 + KSV[BQ]
(5)
7-Hydroxy-3-(4-methoxyphenyl)coumarin
(1)
(0.40 g,
I
1.50 mmol) was dissolved in dried DMF (8 mL) under argon
atmosphere and 4,5-dichlorophthalonitrile (4) (0.29 g, 1.50 mmol)
was added. After stirring for 15 min, finely ground anhydrous
potassium carbonate (0.41 g, 3.00 mmol) was added in por-
tion during 2 h with efficient stirring. The reaction mixture
was stirred under argon atmosphere at room temperature for
48 h. The reaction mixture was then poured into cold water
(150 mL) and the precipitate was filtered off and washed with
water to the yellow product. Purification of this product was
accomplished by column chromatography with silica gel using
dichloromethane/methanol (20/1) as eluent. The compound 7 is
soluble in CHCl3, dichloromethane, THF, DMF and DMSO. Yield:
0.51 g (79%). M.p.: 105 ◦C. FT-IR [(KBr) ꢂmax/cm−1]: 3090 (Ar–CH),
2924 (CH), 2234 (C≡N), 1732 (C O lactone), 1606 (C C), 1277
(Ar–O–Ar). 1H NMR (CDCl3): ı, ppm: Aromatic protons: 7.90 (d,
2 Hz 1H), 7.65 (dd, 9.0 Hz, 2 Hz, 2H), 7.60 (dd, 8.5 Hz, 2 Hz, 1H),
7.23 (d, 2 Hz, 1H), 7.02 (d, 2 Hz, 1H), 6.96 (dd, 9.0 Hz, 2 Hz, 3H),
aliphatic protons: 7.75 (s, 1H), 3.83 (s, 3H, –OCH3). Anal. Calc.
for C24H13ClN2O4 (428,82): C, 67.22; H, 3.06; N, 6.53%; Found: C
67.04; H 2.92; N 6.50%. MS (MALDI-TOF) m/z: 428.97 [M]+.
where I0 and I are the fluorescence intensities of fluorophore in
the absence and presence of quencher, respectively. KSV is the
Stern–Volmer constant; and this is the product of the bimolecu-
lar quenching constant (kq) and the fluorescence lifetime ꢀF (Eq.
(6)):
KSV = kqꢀF
(6)
The ratios I0/I were calculated and plotted against [BQ] according
to Eq. (5), and KSV determined from the slope.
2.5. Synthesis
2.5.1. 4-[3-(4-Methoxyphenyl)-2-oxo-2H-chromen-7-
yloxy]phthalonitrile
(5)
7-Hydroxy-3-(4-methoxyphenyl)coumarin
(1)
(0.5 g,
1.86 mmol) and 4-nitrophthalonitrile (2) (0.32 g, 1.86 mmol)
were dissolved in dried DMF (9 mL) under argon atmosphere. After
stirring for 15 min, finely ground anhydrous potassium carbonate
(0.38 g, 2.80 mmol) was added in portion during 2 h with efficient
stirring. The reaction mixture was stirred under argon atmosphere
at room temperature for 48 h. The reaction mixture was then
poured into cold water (150 mL) and the precipitate was filtered
off and washed with water to the pink product. Purification of
this product was accomplished by column chromatography with
silica gel using dichloromethane/methanol (5/2) as eluent. The
compound (5) is soluble in tetrahydrofurane (THF), DMF and
dimethylsulfoxide (DMSO). Yield: 0.59 g (80%). M.p.: 114 ◦C. FT-IR
[(KBr) ꢂmax/cm−1]: 3084 (Ar–CH), 2964 (CH), 2230 (C N), 1723
(C O lactone), 1592 (C C), 1284 (Ar–O–Ar). 1H NMR (CDCl3): ı,
ppm: Aromatic protons: 7.79 (d, 8.79 Hz, 1H), 7.68 (d, 8.79 Hz,
2H), 7.62 (d, 8.54 Hz, 1H), 7.38 (d, 2.44 Hz, 1H), 7.34 (d, 8.79 Hz,
1H), 7.07 (d, 1.96 Hz, 1H), 6.98 (d, 8.79 Hz, 3H), aliphatic protons:
7.78 (s, 1H, CH), 3.86 (s, 3H, –OCH3). Anal. Calc. for C24H14N2O4
(394.38): C, 73.09; H, 3.58; N, 7.10%; Found: C 72.93, H 3.47, N
6.93%. MS (MALDI-TOF) m/z: 394.98 [M]+.
2.5.4. 2(3),9(10),16(17),23(24)-Tetrakis[3-(4-methoxyphenyl)-2-
oxo-2H-chromen-7-yloxy]phthalocyaninato zinc(II)
(8)
A mixture of 5 (0.3 g, 0.76 mmol), zinc(II) acetate dihydrate
(0.17 g, 0.76 mmol) and N,N-dimethylaminoethanol (DMAE) (2 mL)
was heated to reflux temperature for 16 h under argon atmo-
sphere in a round-bottomed flask. The resulting green suspension
was cooled to room temperature and the crude product was pre-
cipitated by addition of acetic acid. The green solid product was
precipitated and collected by filtration and washed several times
with hot acetic acid, water, methanol, ethanol, ethyl acetate, ace-
tonitrile, acetone, diethyl ether. The crude green product was
purified by column chromatography with silica gel using CHCl3
as eluent. The compound 8 is soluble in CHCl3, dichloromethane,
toluene, THF, DMF and DMSO. Yield: 0.09 g (30%). M.p. > 300 ◦C.
UV–vis (DMF): ꢃmax/nm (log ε): 353 (5.04), 609 (4.50), 678 (5.22,
FWHM = 23 nm). FT-IR [(KBr) ꢂmax/cm−1]: 3066 (Ar–CH), 2954 (CH),
1724 (C O, lactone), 1604 (C C), 1253 (Ar–O–Ar). 1H NMR (CDCl3):
ı, ppm: Aromatic protons: 7.92–6.40 (m, 44H), aliphatic protons:
3.73 (s, 12H). Anal. Calc. for C96H56N8O16Zn (1642,93): C, 70.18; H,
3.44; N, 6.82%; Found: C 69.92, H 3.17, N 6.59%. MS (MALDI-TOF)
m/z: 1642,44 [M]+, 1664,40 [M+Na]+.
2.5.2. 3-[3-(4-Methoxyphenyl)-2-oxo-2H-chromen-7-
yloxy]phthalonitrile
(6)
7-Hydroxy-3-(4-methoxyphenyl)coumarin
(1)
(0.55 g,
2.05 mmol) was dissolved in dried DMF (10 mL) under argon
atmosphere and 3-nitrophthalonitrile (3) (0.35 g, 2.05 mmol) was
added. After stirring for 15 min, finely ground anhydrous potassium
carbonate (0.56 g, 4.10 mmol) was added in portion during 2 h with
efficient stirring. The reaction mixture was stirred under argon
atmosphere at room temperature for 54 h. The reaction mixture
was then poured into cold water (170 mL) and the precipitate was
filtered off and washed with water. Purification of this product was
2.5.5. 1(4),8(11),15(18),22(25)-Tetrakis[3-(4-methoxyphenyl)-2-
oxo-2H-chromen-7-yloxy]phthalocyaninato zinc(II)
(9)
A mixture of 6 (0.3 g, 0.76 mmol), zinc(II) acetate dihydrate
(0.17 g, 0.76 mmol) and DMAE (2 mL) was heated to reflux for
16 h under argon atmosphere in a round-bottomed flask. The

M. Pis¸kin et al. / Journal of Photochemistry and Photobiology A: Chemistry 223 (2011) 37–49
41
resulting green suspension was cooled to room temperature and
the crude product was precipitated by addition of acetic acid. The
green solid product was precipitated and collected by filtration
and washed several times with hot acetic acid, water, methanol,
ethanol, ethyl acetate, acetonitrile, acetone and diethyl ether. The
crude green product was purified by column chromatography
with silica gel using CHCl3 as eluent. The compound 9 is sol-
uble in CHCl3, dichloromethane, toluene, THF, DMF and DMSO.
Yield: 0.10 g (32%). M.p. > 300 ◦C. UV–vis (DMF): ꢃmax/nm (log ε):
340 (4.31), 619 (4.83), 690 (5.10, FWHM = 22 nm). FT-IR [(KBr)
ꢂmax/cm−1]: 3040 (Ar–H), 2920 (CH), 1722 (C O, lactone), 1609
(C C), 1251 (Ar–O–Ar). 1H NMR (CDCl3): ı, ppm: Aromatic pro-
tons: 7.88–6.84 (m, 44H), aliphatic protons: 3.74 (s, 12H). Anal.
Calc. for C96H56N8O16Zn (1642,93): C, 70.18; H, 3.44; N, 6.82%;
Found: C 69.95, H 3.20, N 6.68%. MS (MALDI-TOF) m/z: 1642.57
[M]+.
of 7-oxy-3-(4-methoxyphenyl)coumarin substituted phthaloni-
triles (5–7). In both cases, a mixture of four possible structural
isomers is obtained for tetra-substituted zinc(II) Pcs. The four prob-
able isomers can be designed by their molecular symmetry as
C4h, C2v, Cs and D2h. In this study, synthesized tetrakis-(7-oxy-3-
(4-methoxyphenyl)coumarin substituted zinc(II) Pc complexes are
obtained as isomer mixtures as expected. No attempt was made to
separate the isomers of complexes 8 and 9.
Generally, phthalocyanine complexes are insoluble in most
organic solvents; however introduction of substituents on the
ring increases the solubility. All studied zinc(II) Pc complexes
(8–10) exhibited excellent solubility in organic solvents such
as dichloromethane, CHCl3, THF, DMF and DMSO. The new
compounds were characterized by UV–vis, FT-IR and NMR spec-
troscopies, MALDI-TOF mass spectra and elemental analysis. The
analyses are consistent with the predicted structures as shown in
Section 2.
Comparison of the IR spectra at each step gave some insights on
the nature of the products. The –OH stretching band of 7-hydroxy-
3-(4-methoxyphenyl)coumarin group at 3173 cm−1 disappeared
for all dinitrile compounds in the IR spectra. The IR spectra of
the all dinitrile compounds showed a sharp peak at around 2230-
2239 cm−1 for C≡N stretching. These peaks disappeared and the
color changed to green after conversion, indicative of phthalocya-
nines formation.
2.5.6. Octakis{[2,9,16,23-(3-(4-methoxyphenyl)-2-oxo-2H-
chromen-7-yloxy)-3,10,17,24-chloro]}phthalocyaninato zinc(II)
(10)
A mixture of 7 (0.3 g, 0.70 mmol), zinc(II) acetate dihydrate
(0.15 g, 0.7 mmol) and DMAE (2 mL) was heated to reflux tem-
perature for 16 h under argon atmosphere in a round-bottomed
flask. The resulting green suspension was cooled to room tem-
perature and the crude product was precipitated by addition of
acetic acid. The green solid product was precipitated and collected
by filtration and washed several times with hot acetic acid, water,
methanol, ethanol, ethyl acetate, acetonitrile, acetone and diethyl
ether. The crude green product was purified by column chromatog-
raphy with silica gel using CHCl3 as eluent. The compound 10 is
soluble in CHCl3, dichloromethane, toluene, THF, DMF and DMSO.
Yield: 0.09 g (29%). M.p. > 300 ◦C. UV–vis (DMF): ꢃmax/nm (log ε):
349 (4.32), 612 (4.91), 679 (4.99, FWHM = 23 nm). FT-IR [(KBr)
ꢂmax/cm−1]: 3043 (Ar–CH), 2845 (CH), 1719 (C O, lactone), 1608
(C C), 1245 (Ar–O–Ar). 1H NMR (CDCl3): ı, ppm: Aromatic protons:
6.50–8.00 (m, 40H), aliphatic protons: 3.74 (s, 12H). Anal. Calc. for
The 1H NMR spectra of substituted dinitrile compounds (5–7)
were recorded in CDCl3. Aromatic and aliphatic protons signals
were obtained in their respective regions in the 1H NMR spec-
tra. In the 1H NMR spectra of substituted dinitrile compounds
(5–7), the aromatic protons were observed at between 7.79 and
6.98 ppm for compound 5, 7.95 and 7.36 ppm for compound 6
and 7.90 and 6.96 ppm for compound 7 integrating totally 10 pro-
tons for compounds 5 and 6, and 9 protons for compounds 7. The
aliphatic methyl protons were observed at 3.86 ppm for compound
5, 3.81 ppm for compound 6, 3.83 ppm for compound 7 integrating
3 protons for each compound. The protons for coumarin lactone
ring were observed at 7.78 ppm for compound 5, 8.24 ppm for com-
pound 6, 7.75 ppm for compound 7 integrating 1 proton for each
compound.
C96H52Cl4N8O16Zn (1780.71): C, 64.75; H, 2.94; N, 6.29; Zn, 3.67%;
Found: C 64.58, H 2.80, N 7.78%. MS (MALDI-TOF) m/z: 1780.95
[M]+.
In the mass spectra of phthalonitrile compounds obtained by
the MALDI-TOF technique, the molecular ion peaks were observed
at m/z: 394.98 [M]+ for 5, 394.89 [M]+ for 6 and 428.97 [M]+ for 7.
The C≡N stretching peaks of the dinitrile compounds at
around 2230–2240 cm−1 disappeared after formation of the
phthalocyanine complexes. In the IR spectra for Pc complexes
(8–10), vibrations bands were observed at: 3040–3066 cm−1
for aromatic C–H stretching, 2845–2954 cm−1 for aliphatic C–H
stretching, 1719–1724 cm−1 for C O vibration of the ester groups,
1604–1609 cm−1 for aromatic C C stretching and 1246–1253 cm−1
for Ar–O–Ar stretching.
3. Results and discussion
3.1. Synthesis and characterization
The preparation of 7-oxy-3-(4-methoxyphenyl)coumarin
substituted
phthalonitriles
from
7-hydroxy-3-(4-
methoxyphenyl)coumarin (1) and 4-nitrophthalonitrile (2),
3-nitrophthalonitrile (3) or 4,5-dichlorophthalonitrile (4)
(Scheme 1) through base catalysed nucleophilic aromatic dis-
placement reaction [48,49]. The reactions were carried out in
DMF at room temperature and gave yields of about 76–80%. The
7-oxy-3-(4-methoxyphenyl)coumarin substituted phthalonitriles
(5–7) were purified by column chromatography in each case
using a mixed solvent system of dichloromethane/methanol as
eluent.
The preparation of phthalocyanine derivatives from the aro-
matic 1,2-dinitriles occurs under different reaction conditions.
The syntheses of zinc(II) Pc complexes (8–10) were achieved
by treatment of 7-oxy-3-(4-methoxyphenyl)coumarin substituted
phthalonitriles (5–7) with zinc(II) acetate in DMAE (Scheme 1).
The 7-oxy-3-(4-methoxyphenyl) coumarin substituted phthalo-
cyanines (8–10) were washed several times with different solvents
and then were purified by column chromatography with silica gel
using CHCl3 as eluent. Tetra- and octa-substituted zinc(II) phthalo-
cyanine complexes (8-10) were prepared by cyclotetramerization
The 1H NMR spectra of Pcs (8–10) were recorded in CDCl3. The
1H NMR spectra of substituted phthalocyanine complexes (8–10)
have broad absorptions when compared with that of correspond-
ing phthalonitrile derivatives (5–7). It is likely that broadness is due
to both chemical exchange caused by aggregation–disaggregation
equilibrium in CDCl3 and the fact that the product obtained in
this reaction is a mixture of four positional isomers (for tetra-
substituted complexes) which are expected to show chemical
shifts which slightly differ from each other. The 7-oxy-3-(4-
methoxyphenyl)coumarin substituted zinc(II) Pc complexes were
found to be pure by 1H NMR with all the substituents and ring
protons observed in their respective regions. In the 1H NMR spec-
tra of Pcs (8–10), the aromatic protons were observed at between
7.92 and 6.40 ppm for compound (8), 7.88 and 6.84 ppm for com-
pound (9) and 8.00 and 6.50 ppm for compound (10) integrating
totally 44, 44, 40 protons for each Pcs respectively. The aliphatic

42
M. Pis¸kin et al. / Journal of Photochemistry and Photobiology A: Chemistry 223 (2011) 37–49
Table 1
Absorption, excitation and emission spectral data for unsubstituted (ZnPc), peripherally tetrakis (8), non-peripherally tetrakis (9) and peripherally octakis-tetra-chloro
substituted (10) zinc(II) phthalocyanine complexes in DMF.
Compound
Q band ꢃmax, (nm)
log ε
Excitation ꢃEx (nm)
Emission ꢃEm (nm)
Stokes shift ꢄStokes, ×104 (kJ/mol)
8
9
678
690
679
670
5.22
5.15
4.99
5.37
679
691
679
670
689
702
687
676
1.08
0.99
1.49
1.99
10
ZnPca
a
Data from Ref. [61].
methyl protons were observed at 3.73, 3.74, 3.74 ppm for all Pcs
respectively integrating totally 12 protons for each Pcs (8, 9 and
10).
In the mass spectra of phthalocyanines obtained by the MALDI-
TOF technique, the molecular ion peaks were observed at m/z:
1642.44 [M]+ for 8, 1642.57 [M]+ for 9, 1780.95 [M]+ for 10 (Fig. 1).
tion properties of the molecules. While the aggregated molecules
exhibit high FWHM values, the non-aggregated molecules show
low FWHM values. The FWHM values of the substituted zinc(II)
Pc complexes (8–10) are approximately 20 nm in DMF and sim-
ilar to non-aggregated phthalocyanine complexes studied in the
literature [59,60].
3.4. Fluorescence spectra
3.2. Ground state electronic absorption spectra
Fig. 4 shows fluorescence emission, absorption and excita-
tion spectra of 7-oxy-3-(4-methoxyphenyl)coumarin substituted
zinc(II) Pc complexes 8 (Fig. 4A), 9 (Fig. 4B) and 10 (Fig. 4C) in
DMF. Fluorescence emission peaks were listed in Table 1. The
observed Stokes shifts were within the region observed for zinc(II)
Pc complexes. All zinc(II) Pc complexes (8–10) showed similar flu-
orescence behaviour in DMF (Fig. 4). The excitation spectra were
similar to absorption spectra and both were mirror images of the
fluorescent spectra for all zinc(II) Pc complexes in DMF. The proxim-
ity of the wavelength of each component of the Q-band absorption
to the Q-band maxima of the excitation spectra for all zinc(II) Pc
complexes suggest that the nuclear configurations of the ground
and excited states are similar and not affected by excitation.
The
electronic
spectra
of
the
7-oxy-3-(4-
methoxyphenyl)coumarin substituted zinc(II) Pc complexes
(8–10) showed characteristic absorption in the Q band region at
around 678–690 nm in DMF, Table 1. The B bands were observed
at around 340–353 nm (Fig. 2). The spectra showed monomeric
behaviour evidenced by a single (narrow) Q band, typical of
metallated phthalocyanine complexes [50]. In DMF, the Q bands
were observed at: 670 nm for unsubstituted (ZnPc), 678 nm for
peripherally tetrakis (8), 690 nm for non-peripherally tetrakis (9)
and 679 nm for peripherally octakis-tetra-chloro substituted (10)
zinc(II) phthalocyanine complexes, Table 1. The red-shifts were
observed for zinc(II) Pc complexes following substitution with
coumarin groups. The observed Q band absorptions of the studied
complexes (8–10) are similar with those of ZnPcs bearing similar
substituents like alkoxyl- and phenoxyl-groups [51,52]. The Q band
of the non-peripheral substituted complex (9) is red-shifted when
compared to the corresponding peripheral tetra-(8) and octa-(10)
substituted complexes in DMF (Fig. 2). The red-shifts are 12 nm
(0.99 × 104 kJ/mol) between 8 and 9, 11 nm (1.08 × 104 kJ/mol)
between 9 and 10. The observed red spectral shifts are typical of
Pcs with substituents at the non-peripheral positions and have
been explained in the literature [53].
3.5. Fluorescence quantum yields and lifetimes
The fluorescence quantum yields (˚F) of the studied zinc Pc
complexes (8, 9 and 10) are given in Table 2. The ˚F values of the
zinc Pc complexes are similar and typical of other studied zinc Pc
complexes in DMF [51,61–64]. For comparison among the studied
zinc(II) Pc complexes, the ˚F values of the peripherally chloro octa-
substituted zinc(II) Pc (10) is the lowest among the studied zinc(II)
Pc complexes, it could be attributed to a little aggregation of this
complex in DMF.
The fluorescence lifetime (ꢀF) values (Table 2) were calcu-
lated by Eq. (2) using natural radiative lifetime (ꢀ0) values. The
ꢀF values of the substituted zinc(II) Pc complexes are higher
compared to unsubstituted zinc(II) Pc complexes in DMF, sug-
gesting less quenching by substitution. ꢀF values are higher for
non-peripherally tetra-substituted zinc(II) Pc complex (9) when
compared to peripherally tetra-substituted (8) and peripherally
octa-substituted (10) zinc(II) Pc complex, Table 2, suggesting more
quenching by peripherally-tetra and octa-substitution compared
to non-peripherally substitution. However, the ꢀF values are typical
for zinc(II) Pc complexes [51,61–64].
3.3. Aggregation studies
Aggregation is usually depicted as a coplanar association of
rings progressing from monomer to dimer and higher order com-
plexes. It is dependent on the concentration, nature of the solvent,
nature of the substituents, complexed metal ions and temperature
[54]. It has been established that Pcs can form H- and J-aggregates
depending on the orientation of the induced transition dipoles
of their constituent monomers [55]. In H-aggregates, the compo-
nent monomers are arranged into a face-to-face conformation, and
transition dipoles are perpendicular to the line connecting their
centers [56,57]. In the aggregated state the electronic structure
of the complexed phthalocyanine rings are perturbed resulting in
alternation of the ground and excited state electronic structures
[58]. In this study, the aggregation behaviour of 7-oxy-3-(4-
methoxyphenyl)coumarin substituted zinc(II) Pc complexes (8-10)
were investigated at different concentrations in DMF (Fig. 3, for
complex 9 as an example). The Beer–Lambert law was obeyed for
all of these compounds at concentrations ranging from 1.4 × 10−5
to 4 × 10−6 M. The 7-oxy-3-(4-methoxyphenyl)coumarin substi-
tuted zinc(II) Pc complexes did not show aggregation at these
concentration ranging in DMF. The full width at half maximum
(FWHM) values are another main evidence about the aggrega-
Table 2
Photophysical and photochemical parameters of unsubstituted (ZnPc), peripher-
ally tetrakis (8), non-peripherally tetrakis (9) and peripherally octakis-tetra-chloro
substituted (10) zinc(II) phthalocyanine complexes in DMF.
Compound
˚
F
ꢀF (ns) ꢀ0 (ns) akF (s−1) (×107)
˚
d
(×10−5
)
˚
ꢁ
8
9
0.16
0.19
0.13
0.17
1.44
2.50
1.87
1.03
9.00
13.17
14.43
6.05
11.11
7.60
6.95
3.69
12.72
8.99
2.3
0.72
0.76
0.70
0.56
10
ZnPcb
16.53
a
kF is the rate constant for fluorescence. Values calculated using kF = ˚F/ꢀF.
Data from Ref. [61].
b

M. Pis¸kin et al. / Journal of Photochemistry and Photobiology A: Chemistry 223 (2011) 37–49
43
Fig. 1. Mass spectra of the phthalocyanine complexes: (A) for complex 8, (B) for complex 9 and (C) for complex 10.
The ꢀ0 and the rate constants for fluorescence (kF) values are also
given in Table 2. The ꢀ0 values of the substituted zinc(II) Pc com-
plexes (8–10) are higher than unsubstituted zinc(II) Pc complex
in DMF. The chloro octa-substituted zinc(II) Pc complex showed
the highest ꢀ0 value than peripherally and non-peripherally tetra-
substituted zinc(II) Pc complexes (8 and 9) in DMF (Table 2). This is
due to the heavy atom effect of chlorine atom. The non-peripheral
substituted zinc(II) Pc complex (9) showed higher ꢀ0 value than
peripheral substituted zinc(II) Pc complex (8) complexes in DMF
(Table 2) due to the position effect. The heavy chlorine atoms
reduce the rate constants for fluorescence (kF) increase the natural
radiative lifetime (ꢀ0). The rate constants for fluorescence (kF) of
substituted zinc(II) Pc complex (8) is the highest among the stud-
ied zinc Pc complexes. The fluorescence quantum yields (˚F) of

44
M. Pis¸kin et al. / Journal of Photochemistry and Photobiology A: Chemistry 223 (2011) 37–49
0.3
0.2
0.1
0
(678 nm) 8
9 (690 nm)
(679 nm) 10
300
400
500
600
700
800
Wavelength (nm)
Fig. 2. Absorption spectra of substituted zinc(II) phthalocyanine complexes (8, 9 and 10) in DMF. Concentration = 1 × 10−5 M.
the studied complexes (8–10) higher than those of ZnPcs bearing
similar substituents like phenoxyl-groups of (˚F) [51,52].
tion, the photosensitizer molecule is first excited to the singlet
state and through intersystem crossing forms the triplet state,
and then transfers the energy to ground state oxygen, O2(3ꢅg),
generating excited singlet state oxygen, O2(1ꢁg), the chief cyto-
toxic species, which subsequently oxidizes the substrate by Type II
mechanism.
There was no change in the Q band intensity during the ˚ꢁ
determinations, confirming that complexes were not degraded
during singlet oxygen studies (Fig. 5 as an example for complex 8).
The singlet oxygen generation was measured in air. The ˚ꢁ values
of the substituted zinc(II) Pc complexes (8–10) are higher when
3.6. Singlet oxygen quantum yields
Many factors are responsible for the magnitude of the deter-
mined quantum yield of singlet oxygen including; triplet excited
state energy, ability of substituents and solvents to quench the sin-
glet oxygen, the triplet excited state lifetime and the efficiency
of the energy transfer between the triplet excited state and the
ground state of oxygen. It is believed that during photosensitiza-
2
2.5
y = 141223x
R2 = 0.9845
2
A
B
C
D
E
1.5
1
1.5
1
0.5
0
0.00E+00
5.00E-06
1.00E-05
1.50E-05
F
Concentration
0.5
0
300
400
500
600
700
800
Wavelength (nm)
Fig. 3. Absorption spectral changes of 9 in DMF at different concentrations: 14 × 10−6 (A), 12 × 10−6 (B), 10 × 10−6 (C), 8 × 10−6 (D), 6 × 10−6 (E), 4 × 10−6 (F) M (Inset: plot
of absorbance versus concentration).

M. Pis¸kin et al. / Journal of Photochemistry and Photobiology A: Chemistry 223 (2011) 37–49
45
1
Excitation (679 nm)
Absorption (678 nm)
A
0.8
0.6
0.4
0.2
0
Emission (689 nm)
500
550
600
650
700
750
800
Wavelength (nm)
Exication (691 nm)
0.8
0.6
0.4
0.2
0
B
Emission (702 nm)
Absorption (690 nm)
500
550
600
650
700
750
800
850
Wavelength (nm)
0.5
0.4
0.3
0.2
0.1
0
C
Emission (687 nm)
Exication (679 nm)
Absorption (679 nm)
500
550
600
650
700
750
800
Wavelength (nm)
Fig. 4. Absorption, excitation and emission spectra of the compounds: (A) for complex 8, (B) for complex 9 and (C) for complex 10 in DMF. Excitation wavelength = 645 nm
for 8 and 10, 660 nm for 9.
compared to unsubstituted zinc(II) Pc complex in DMF (Table 2).
The ˚ꢁ value of chloro octa substituted complex (10) slightly lower
than other substituted zinc(II) Pc complexes in DMF, it could be
attributed to a little aggregation of this complex in DMF. The non-
peripherally tetra-substituted zinc(II) Pc complex (9) showed the
highest ˚ꢁ value among the studied zinc(II) Pc complexes (Table 2)
may be due to absorption of light at longer wavelength than periph-
erally substitution. The ˚ꢁ values of the studied complexes (8–10)
were also measured under nitrogen atmosphere. Nitrogen was
purged in the solutions of the samples for 15 min before singlet oxy-
gen determination. The ˚ꢁ values of complexes 8 and 9 increased
from 0.72 to 0.83 and from 0.76 to 0.94, respectively. The ˚ꢁ value
of complex 10 reduced from 0.70 to 0.63 under nitrogen atmo-
sphere. The ˚ꢁ values of the studied complexes (8–10) higher than
those of ZnPcs bearing similar substituents like phenoxyl-groups of
˚
values [51,52].
ꢁ

46
M. Pis¸kin et al. / Journal of Photochemistry and Photobiology A: Chemistry 223 (2011) 37–49
1.6
1.6
1.2
0.8
0.4
0
y = -0.072x + 1.4447
R² = 0.9965
1.2
0 sec
0.8
5 sec
10 sec
0.4
0
0
2
4
6
8
10
Time (sec)
300
400
500
600
700
Wavelength (nm)
Fig. 5. The absorption spectral changes during the determination of singlet oxygen quantum yields. This determination was for compound 8 in DMF at a concentration of
1 × 10−5 M (Inset: plot of DPBF absorbance versus time).
3.7. Photodegradation studies
[51,52]. Stable zinc phthalocyanine molecules show ˚d values as
low as 10−6 and for unstable molecules, values of the order of
10−3 have been reported [52]. Table 2 shows that all substituted
complexes (8–10) were less stable to degradation compared to
unsubstituted ZnPc in DMF. Thus, the substitution of ZnPc with 7-
oxy-3-(4-methoxyphenyl)coumarin groups seem to decrease the
stability of the complexes in DMF. The non-peripherally substi-
tuted zinc(II) Pc complex (9) was less stable when compared to
the other substituted complexes (8 and 10). The peripherally sub-
stituted complex (8) is the most stable than the other complexes.
It seems zinc(II) metal and 7-oxy-3-(4-methoxyphenyl)coumarin
Degradation of the molecules under irradiation can be used
to study their stability and this is especially important for those
molecules intended for use as photocatalysts. The collapse of the
absorption spectra without any distortion of the shape confirms
photodegradation not associated with phototransformation into
different forms of MPc absorbing in the visible region (Fig. 6 as
an example for complex 9 in DMF) The ˚d values, found in this
study, are higher than phthalocyanine derivatives having different
metals and substituents on the phthalocyanine ring in literature
1.8
1.8
1.5
1.2
1.5
y = -0.0004x + 1.6299
R² = 0.986
0.9
0.6
0.3
0
1.2
0.9
0.6
0.3
0
0 sec
300 sec
0
300
600
900
1200
1500
600 sec
900 sec
1200 sec
1500 sec
Time (sec)
300
400
500
600
700
800
Wavelength(nm)
Fig. 6. The absorption spectral changes of compound 9 in DMF under light irradiation showing the disappearance of the Q-band at five minutes intervals (Inset: plot of
absorbance versus time).

M. Pis¸kin et al. / Journal of Photochemistry and Photobiology A: Chemistry 223 (2011) 37–49
47
300
250
200
150
100
50
[BQ]=0
[BQ]=saturated
0
655
675
695
715
735
755
775
795
Wavelength (nm)
Fig. 7. Fluorescence emission spectral changes of 10 (1.00 × 10−5 M) on addition of different concentrations of BQ in DMF. [BQ] = 0, 0.008, 0.016, 0.024 M.
Table 3
sional quenching mechanism. The KSV values of the substituted zinc
phthalocyanine complexes (8, 9 and 10) are lower than unsubsti-
tuted ZnPc in DMF. The peripherally substituted zinc(II) Pc complex
(8) has highest KSV value, while non-peripherally substituted
zinc(II) Pc complex (9) has the lowest KSV in DMF. The substitu-
tion with 7-oxy-3-(4-methoxyphenyl)coumarin groups seems to
decrease the KSV values of the complexes in DMF. The bimolec-
ular quenching rate constant (kq) values of the substituted zinc
phthalocyanine complexes (8, 9 and 10) are also lower than
unsubstituted ZnPc in DMF, thus substitution with 7-oxy-3-(4-
methoxyphenyl)coumarin group seems to decrease the kq values
Fluorescence quenching data for unsubstituted (ZnPc), peripherally tetrakis (8),
non-peripherally tetrakis (9) and peripherally octakis-tetra-chloro substituted (10)
zinc(II) phthalocyanine complexes in DMF.
Compound
KSV (M−1
)
kq/1010 (M−1 s−1
)
8
9
32.42
20.70
28.86
57.60
2.25
0.83
1.54
5.59
10
ZnPca
a
Data from Ref. [61].
of the complexes. Values of kq near 1010
M
−1 s−1 are in agreement
substituted zinc(II) Pc groups increases the ˚d values and decreases
the stability of complexes.
with the theoretical Smoluchowski–Stokes–Einstein approxima-
tion at 298 K [65]. The order in kq values among the substituted
complexes was also as follows: 8 > 10 > 9 in DMF.
3.8. Fluorescence quenching studies by 1,4-benzoquinone [BQ]
The fluorescence quenching of zinc phthalocyanine complexes
by BQ in DMF was found to obey Stern–Volmer kinetics, which is
consistent with diffusion-controlled bimolecular reactions. Fig. 7
shows the quenching of complex (10) by BQ in DMF as an example.
The slope of the plots shown at Fig. 8 gave Stern–Volmer constants
(KSV) values, listed in Table 3. The linearity of these plots indicates
that fluorescence quenching is reasonably described by a colli-
4. Conclusions
In the presented work, the syntheses of new 7-oxy-3-
(4-methoxyphenyl)coumarin substituted peripherally tetra-(8),
non-peripherally tetra-(9) and chloro octa-(10) zinc(II) phthalo-
cyanine complexes were described and new compounds were
characterized by elemental analysis, 1H NMR, MALDI-TOF, IR,
UV–vis and fluorescence spectral data. The photophysical and pho-
tochemical properties of these zinc(II) Pc complexes were also
described in DMF for comparison of the effects of the num-
ber of the substituents and their position on the phthalocyanine
framework. All the studied zinc(II) Pc complexes show excellent
solubity in general organic solvents. The studied zinc(II) com-
plexes are monomeric and showed similar fluorescence behaviour
in DMF. The ˚F values of the studied zinc(II) Pc complexes are
similar and typical for zinc(II) Pc complexes bearing different sub-
stitution. The ˚ꢁ values of zinc(II) Pc complexes ranged from
0.70 to 0.76 gives an indication of the potential of these com-
pounds as photosensitizers in PDT applications. The substitution
of ZnPc with 7-oxy-3-(4-methoxyphenyl)coumarin groups seem to
decrease the photostability of the complexes in DMF. The 7-oxy-3-
(4-methoxyphenyl)coumarin substituted zinc(II) Pc complexes (8,
9 and 10) showed lower Ksv and bimolecular quenching rate con-
stant (kq) values when compared to the unsubstituted ZnPc in DMF.
The (kq) values were found to be close to the diffusion-controlled
8
1.8
10
1.6
9
1.4
1.2
1
0
0
.005
0.01
0.015
0.02
0.025
[BQ]
Fig. 8. Stern–Volmer plots for BQ quenching of coumarin substituted zinc(II)
phthalocyanines (8, 9 and 10). [MPc] = ∼1.00 × 10−5 M in DMF. [BQ] = 0, 0.008, 0.016,
0.024 M.
limits, approximately 1010
M .
−1 s−1

48
M. Pis¸kin et al. / Journal of Photochemistry and Photobiology A: Chemistry 223 (2011) 37–49
[27] D. Wöhrle, V. Schmidt, Octabutoxyphthalocyanine, a new electron donor, J.
Acknowledgement
Chem. Soc. Dalton Trans. (1988) 549–551.
[28] P.D. Hale, W.J. Pietro, M.A. Ratner, D.E. Ellis, T.J. Marks, The electronic structure
of substituted phthalocyanines: a Hartree-Fock-Slater study of octacyano- and
octafluoro-substituted (phthalocyaninato)silicon dihydroxide, J. Am. Chem.
Soc. 109 (1987) 5943–5947.
We are thankful to the Research Foundation of Marmara
University, Commission of Scientific Research Project (BAPKO)
[FEN-C-DRP-110908-0232 and FEN-A-090909-0302].
[29] D. Schlettwein, N.R. Armstrong, Correlation of frontier orbital positions and
conduction type of molecular semiconductors as derived from ups in combi-
nation with electrical and photoelectrochemical experiments, J. Phys. Chem.
98 (1994) 11771–11779.
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