Highly singlet oxygen generative water-soluble coumarin substituted zinc(II) phthalocyanine photosensitizers for photodynamic therapy

Article abstract of DOI:10.1016/j.poly.2012.04.034

New tetra-non-peripherally and peripherally ethyl butyrate or butanoic acid and their sodium salts bearing coumarin substituted zinc(II) phthalocyanine complexes have been synthesized and characterized for the first time. Butanoic acid bearing coumarin su

Full text of DOI:10.1016/j.poly.2012.04.034

Polyhedron 41 (2012) 92–103
Contents lists available at SciVerse ScienceDirect
Polyhedron
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Highly singlet oxygen generative water-soluble coumarin substituted zinc(II)
phthalocyanine photosensitizers for photodynamic therapy
Meryem Çamur a, Mahmut Durmusß b, Mustafa Bulut c,
⇑
a Kırklareli University, Department of Chemistry, 39100 Kırklareli, Turkey
b Gebze Institute of Technology, Department of Chemistry, P.O. Box 141, Gebze 41400, Turkey
c Marmara University, Department of Chemistry, 34722 Göztepe-Istanbul, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
New tetra-non-peripherally and peripherally ethyl butyrate or butanoic acid and their sodium salts bear-
ing coumarin substituted zinc(II) phthalocyanine complexes have been synthesized and characterized for
the first time. Butanoic acid bearing coumarin substituted zinc(II) phthalocyanine complexes and their
sodium salts show excellent solubility in aqueous solution. Photophysical and photochemical properties
of these phthalocyanines were investigated. General trends are described for photodegradation, fluores-
cence and singlet oxygen quantum yields as well as fluorescence lifetimes of these compounds. The value
of singlet oxygen quantum yields ranged from 0.65 to 0.93 in phosphate-buffered saline + Triton X-100
solution indicating that they can produce singlet oxygen in high efficiency. This study also presented
the synthesized water soluble zinc(II) phthalocyanines strongly bind to bovine serum albumin.
Ó 2012 Elsevier Ltd. All rights reserved.
Received 7 March 2012
Accepted 25 April 2012
Available online 5 May 2012
Keywords:
Phthalocyanine
Coumarin (2H-1-benzopyran-2-one)
Zinc
Water soluble
Photodynamic therapy
Singlet oxygen
1. Introduction
their solubility in number of solvents and to obtain Pcs containing
carboxylic acid moieties [20,21].
Phthalocyanines (Pcs) are macrocyclic compounds which pos-
sess a kind of properties of potential significance in applied
sciences [1]. There are extensive researches into the applications
of Pcs in liquid crystals [2], non-linear optics [3], gas sensors [4],
semiconductor devices [5] and electrochromic displays [6]. Pcs
are also identified as having excellent potential in the photody-
namic therapy (PDT) of certain types of cancers [7]. For PDT appli-
cations, the drug is injected into the patient’s blood stream, and
since the blood itself is a hydrophilic system, water solubility
becomes critical for a potential photosensitizer for PDT [8]. Pcs
have been suggested as the second-generation photosensitizers
because of their many advantages such as the high absorption in
the red visible region, strong efficiency to produce singlet oxygen,
ease of chemical modification, and low dark toxicity [9,10]. Zinc(II)
Pc complexes have attracted much interest because of their consid-
erably long triplet lifetimes [7,11]. Water-soluble Pcs are the most
promising photosensitizers [12,13]. Peripheral substitution with
carboxy [14], quaternary ammonium [15], sulfonate [16], glucose
[17], phosphonate [18] or polyoxyethylene [19] groups enhances
solubility in a wide pH range of aqueous solutions. Ester function-
alities have often been added on the periphery of Pcs to improve
Coumarin (2H-1-benzopyran-2-one) containing compounds
have obtained meaningful importance due to their wide use in
the synthetic chemistry and their biological activities [22,23].
Coumarin derivatives show photochemical and photophysical
properties, which give them usefulness in a variety of applications
such as optical brighteners, laser dyes, non-linear optical chro-
mophores, solar energy collectors, fluorescent labels and probes
in biology and medicine [24–29].
Recently, we have successfully prepared Pcs substituted with
the coumarin framework, which showed excellent fluorescence
properties with quantum yield of almost unity [30,31]. The aim
of our ongoing research is to synthesize water-soluble zinc(II) Pc
complexes substituted with coumarin moieties as potential PDT
agents. In this study, the synthesis, characterization and spectro-
scopic behaviour as well as photophysical (fluorescence quantum
yields and lifetimes) and photochemical (singlet oxygen and
photodegradation quantum yields) properties of new zinc(II) Pcs
tetra substituted with 7,8-di-(ethyl 4-oxybutyrate)-3-(4-oxyphe-
nyl)coumarin (5 and 6), the sodium salt of 7,8-di-(4-oxybutanoic
acid)-3-(4-oxyphenyl)coumarin (5a and 6a) and 7,8-di-(4-oxybu-
tanoic acid)-3-(4-oxyphenyl)coumarin (5b and 6b) substituents
at non-peripheral or peripheral positions (namely
a- or b-posi-
tions) of the macrocycle ring. Butanoic acid bearing coumarin
substituted Zn(II) Pc complexes and their sodium salts were solu-
ble in aqueous solution.
⇑
Corresponding author. Tel.: +90 216 3479641/1370; fax: +90 216 3478783.
E-mail addresses: mbulut@marmara.edu.tr, mustafabulut50@gmail.com(M. Bulut).
0277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2012.04.034

M. Çamur et al. / Polyhedron 41 (2012) 92–103
93
C, 67.31; H, 5.13; N, 4.49. Found: C, 67.20; H, 5.05; N, 4.38%. MS
2. Experimental
(MALDI-TOF); m/z 624, found: m/z 624 [M]+, 647 [M+Na]+.
2.1. Materials and equipment
2.2.3. 7,8-Di-(ethyl 4-oxybutyrate)-3-[p-(3,4-
dicyanophenoxy)phenyl]coumarin (4)
Unsubstituted zinc(II) phthalocyanine (ZnPc) and 1,3-
diphenylisobenzofuran (DPBF) were purchased from Aldrich. Zinc(II)
acetate, potassium carbonate (K2CO3), 9,10-antracenediyl-bis(meth-
ylene)dimalonic acid (ADMA), 1,8-diazabicyclo [5.4.0] undec-7-ene
(DBU) and ethyl 4-bromobutyrate were purchased from Fluka.
All solvents were dried as described by Perrin and Armarego [32]
before use. 7,8-Dihydroxy-3-[p-(20,30-dicyanophenoxy)phenyl]cou-
marin (1) [33], 7,8-dihydroxy-3-[p-(30,40-dicyanophenoxy)phenyl]
coumarin (2) [34] and mixed sulphonated zinc phthalocyanine
(ZnPcSmix) [35] were synthesized and purified according to litera-
ture procedures.
Yield: 0.900 g (38%). M.p.: 109 °C. FT-IR (KBr),
m
max/(cmꢁ1):
3066–3031 (Ar–CH), 2986–2948 (Aliphatic -CH), 2227 (C„N),
1719 (C@O, lactone), 1612 (C@C), 1586–1483 (Ar C@C), 1288
(Ar–O–Ar), 1176 (Ar-O-C). 1H NMR (CDCl3, 500 MHz): 7.85 (s, 1H,
coumarin 4-H), 7.78 (dd, J = 8 and 2 Hz, 2H, Ar-H), 7.65 (d,
J = 8 Hz, 1H, Ar-H), 7.50 (d, J = 3 Hz, 1H, Ar-H), 7.35 (dd, J = 8 and
2 Hz, 1H, Ar-H), 7.21 (d, J = 8 Hz, 1H, Ar-H), 7.12 (dd, J = 8 and
2 Hz, 2H, Ar-H), 6.90 (d, J = 8 Hz, 1H, Ar-H), 4.22–4.15 (m, 4H,
–aCH2–), 3.91 (t, J = 6 Hz, 4H, -dCH2-), 2.26 (t, J = 6 Hz, 4H, –bCH2–
), 2.17–2.10 (m, 4H, –cCH2–), 1.31 (t, J = 6 Hz, 6H, –CH3). UV–Vis
(CHCl3) kmax (nm) (loge): 339 (4.51). Anal. Calc. for C35H32N2O9:
Infrared spectra (IR) were recorded on a Shimadzu FTIR-8300
Fourier Transform Infrared Spectrophotometer using KBr pellets,
electronic absorption spectra were recorded on a Shimadzu UV-
2450 and Shimadzu UV-2001 UV–vis spectrophotometers. Elemen-
tal analyses were performed by the Instrumental Analysis Labora-
tory of the TUBITAK Marmara Research Centre. 1H NMR spectra
were recorded on a Varian Unity Inova 500 MHz spectrometer
using TMS as an internal standard. Mass spectra were performed
on a Bruker Autoflex III MALDI-TOF spectrometer using 2,5-dihy-
droxybenzoic acid (DHB, 0.02 g/mL in THF) as matrix. MALDI sam-
ples were prepared by mixing the complex (0.02 g/mL in DMF)
with the matrix solution (1:10 v/v) in a 0.5 mL Eppendorf micro
tube. Finally, 1 ꢀ 10ꢁ3 mL of this mixture was deposited on the
sample plate, dried at room temperature and then analyzed.
Photo-irradiations were performed using a General Electric quartz
line lamp (300 W). A 600 nm glass cut off filter (Intor) and a water
filter were used to filter off ultraviolet and infrared radiations,
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.
C, 67.31; H, 5.13; N, 4.49. Found: C, 67.43; H, 5.22; N, 4.41%. MS
(MALDI-TOF); m/z 624, found: m/z 624 [M]+, 647 [M+Na]+.
2.2.4. General procedure for the synthesis of zinc phthalocyanines (5
and 6)
A mixture of either 3 or 4 (0.500 g, 0.801 mmol), Zn(AcO)2
(0.037 g, 0.202 mmol) and 10 lL 1,8-diazabicyclo [5.4.0] undec-
7-ene (DBU) in dry hexanol (2 mL) was heated under reflux with
stirring for 24 h under argon atmosphere. After cooling to room
temperature, methanol (5 mL) was added to precipitate the prod-
uct. The green product was filtered and washed with water, meth-
anol, ethanol, acetonitrile, ethyl acetate, acetone, acetic acid and
diethyl ether. The crude products were purified by column chro-
matography on silica gel with CHCl3 as eluent.
2.2.5. 1(4), 8(11), 15(18), 22(25)-Tetrakis[7,8-di-(ethyl 4-
oxybutyrate)-3-(4-oxyphenyl)coumarin]phthalocyaninato zinc (II) (5)
Yield: 0.320 g (62%). M.p.: >300 °C. FT-IR (KBr),
m
max/(cmꢁ1):
3078–3042 (Ar–CH), 2955–2923 (aliphatic CH), 1726 (C@O,
lactone), 1605 (C@C), 1507–1480 (Ar C@C), 1285–1242 (Ar–O–
Ar), 1169–1071 (Ar–O–C). 1H NMR (CDCl3, 500 MHz): 7.72–7.67
(m, 8H, Ar-H), 7.57–7.49 (m, 10H, Ar-H), 7.41–7.38 (m, 4H, Ar-H),
7.16–7.03 (m, 10H, Ar-H), 6.82–6.76 (m, 8H, Ar-H), 4.07–3.99 (m,
16H, -aCH2-), 2.62–2.46 (m, 16H, –dCH2–), 2.14–2.05 (m, 16H,
–bCH2–), 1.61–1.54 (m, 16H, -cCH2-), 1.22–1.18 (m, 24H, -CH3).
2.2. Synthesis
2.2.1. General procedure for the synthesis of phthalonitriles (3 and 4)
A
mixture of 7,8-dihydroxy-3-[p-(20,30-dicyanophenoxy)
UV–Vis kmax (DMF) (nm) (loge): 349 (5.06), 628 (shoulder, 4.47),
phenyl]coumarin (1) or 7,8-dihydroxy-3-[p-(30,40-dicyanophen-
oxy)phenyl]coumarin (2) (1.50 g, 3.79 mmol), and ethyl
4-bromobutyrate (1.85 g, 9.47 mmol) were dissolved in dry DMF
(10 mL), and anhydrous K2CO3 (1.57 g, 11.36 mmol) was added.
After stirring for 4 days under argon atmosphere, the reaction mix-
ture was poured into ice water. The precipitate formed was filtered,
washed with water and dried over anhydrous Na2SO4. The crude
products were purified by column chromatography on silica gel with
CHCl3 as eluent.
694 (5.20). Anal. Calc. for C140H128N8O36Zn: C, 65.60; H, 4.99; N,
4.37. Found: C, 65.74; H, 5.06; N, 4.45%. MS (MALDI-TOF, DHB as
matrix); m/z 2561, found: m/z 2561 [M]+.
2.2.6. 2(3), 9(10), 16(17), 23(24)-Tetrakis[7,8-di-(ethyl
4-oxybutyrate)-3-(4-oxyphenyl)coumarin]phthalocyaninato zinc (II)
(6)
Yield: 0.357 g (70%). M.p.: >300 °C. FT-IR (KBr),
m
max/(cmꢁ1):
3068–3039 (Ar–CH), 2955–2857 (aliphatic CH), 1726 (C@O,
lactone), 1604 (C@C), 1508–1466 (Ar C@C), 126–1232 (Ar–O–Ar),
1170–1074 (Ar–O–C). 1H NMR (CDCl3, 500 MHz): 7.76–7.66 (m,
8H, Ar-H), 7.59–7.45 (m, 10H, Ar-H), 7.35–7.26 (m, 4H, Ar-H),
7.12–7.05 (m, 10H, Ar-H), 6.79–6.75 (m, 8H, Ar-H), 4.12–4.01 (m,
16H, –aCH2–), 2.61–2.47 (m, 16H, –dCH2–), 2.11–2.06 (m, 16H,
–bCH2–), 1.56–1.51 (m, 16H, –cCH2–), 1.22–1.19 (m, 24H, -CH3).
2.2.2. 7,8-Di-(ethyl 4-oxybutyrate)-3-[p-(20,30-
dicyanophenoxy)phenyl]coumarin (3)
Yield: 0.840 g (36%). M.p.: 99 °C. FT-IR (KBr),
m
max/(cmꢁ1):
3084–3062 (Ar–CH), 2986–2941 (Aliphatic –CH), 2231 (C„N),
1721 (C@O, lactone), 1611 (C@C), 1574–1455 (Ar C@C), 1282
(Ar–O–Ar), 1177 (Ar-O-C). 1H NMR (CDCl3, 500 MHz): 7.83 (s, 1H,
coumarin 4-H), 7.81 (dd, J = 8 and 2 Hz, 2H, Ar-H), 7.64 (t,
J = 6 Hz, 1H, Ar-H), 7.53 (d, J = 8 Hz, 1H, Ar-H), 7.27 (d, J = 8 Hz,
1H, Ar-H), 7.22 (d, J = 8 Hz, 1H, Ar-H), 7.19 (dd, J = 8 and 2 Hz,
2H, Ar-H), 6.95 (d, J = 8 Hz, 1H, Ar-H), 4.20–4.12 (m, 4H, –aCH2–),
3.94 (t, J = 6 Hz, 4H, –dCH2–), 2.25 (t, J = 6 Hz, 4H, –bCH2–),
2.18–2.10 (m, 4H, –cCH2–), 1.30 (t, J = 6 Hz, 6H, –CH3). UV–Vis
UV–Vis kmax (DMF) (nm) (log e): 355 (5.20), 615 (shoulder, 4.52),
679 (5.19). Anal. Calc. for C140H128N8O36Zn: C, 65.60; H, 4.99; N,
4.37. Found: C, 65.73; H, 5.08; N, 4.45%. MS (MALDI-TOF, DHB as
matrix); m/z 2561, found: m/z 2561 [M]+.
2.2.7. General procedure for the synthesis of sodium salts of zinc
metallo phthalocyanines (5a and 6a)
Compound 5 or 6 (0.100 g, 0.039 mmol) were dissolved in tetra-
hydrofuran (THF) (1.5 mL) and added slowly to a NaOH solution in
(CHCl3) kmax (nm) (loge): 336 (4.54). Anal. Calc. for C35H32N2O9:

94
M. Çamur et al. / Polyhedron 41 (2012) 92–103
water/ethanol (1:5) (1 M, 50 mL). The mixture was stirred at 40 °C
for 5 h, and the resulting precipitate was filtered and washed
repeatedly with ethanol and chloroform. The crude product was
dissolved in water and neutralized using 1 M HCl until pH 7. Com-
pound 5a or 6a precipitated upon addition of ethanol to yield a
green solid. Resulting precipitate was filtered and washed repeat-
edly with ethanol and chloroform.
(5.21). Anal. Calc. for C124H96N8O36Zn: C, 63.67; H, 4.11; N, 4.79.
Found: C, 63.74; H, 4.03; N, 4.67%. MS (MALDI-TOF, DHB as ma-
trix); m/z 2337, found: m/z 2337 [M]+.
3. Results and discussion
3.1. Synthesis and characterization
2.2.8. 1(4), 8(11), 15(18), 22(25)-Tetrakis{7,8-di[sodium
(4-oxybutanoat)]-3-(4-oxyphenyl)coumarin}phthalocyaninato zinc
(II) (5a)
The general synthetic route for the synthesis of new phthalo-
nitriles (3 and 4) and zinc(II) Pcs derivatives (5, 6, 5a–b and
6a–b) are given in Scheme 1. The synthesis of the phthalonitriles
(3 and 4) was based on the alkylation reaction of compounds 1
or 2 with ethyl 4-bromobutyrate in the presence of dry K2CO3 as
a base in dry DMF at room temperature. Zn(II) Pcs (5 and 6) were
obtained presence of the anhydrous Zn(AcO)2 and DBU in dry hex-
anol at 160 °C. Hydrolysis of the ester groups on the compounds 5
and 6 using NaOH in a mixed solvent system (THF/EtOH/H2O),
according to Ref. [36], gave the highly water-soluble Pcs (5a and
6a) bearing eight sodium carboxylate groups. Upon addition of
1 M HCl to an aqueous solution of 5a and 6a until pH 2, octacarb-
oxylic acid group bearing Pcs (5b and 6b) were obtained (Scheme
2).
In the IR spectra of 3 and 4, alkyl groups (–CH2 and –CH3) gave
intense absorptions at 2986–2941 and 2986–2948 cmꢁ1, C„N
bands were observed at 2231 and 2227 cmꢁ1, lactone C@O groups
were observed at 1721 and 1719 cmꢁ1, respectively. In the 1H NMR
analysis of 3 and 4 in CDCl3, the proton of coumarin at the four
position appeared as singlet at 7.83 and 7.85 ppm, respectively.
The aromatic protons were observed between 7.81–6.95 ppm for
3 and 7.78–6.90 ppm for 4. The multiplets at 4.20–4.12 ppm for 3
and 4.22–4.15 ppm for 4 indicated the presence of –OCH2– groups
adjacent to ester group, triplets at 3.94 ppm for 3 and 3.91 ppm for
4 indicated the presence of –OCH2– groups adjacent to aromatic
ring. The –CCH2C– protons in the long chains appeared at the range
of 2.25–2.10 ppm for 3 and 2.26–2.10 ppm for 4 as triplet and mul-
tiplet. The –CH3 protons at the end of the chains were observed as
triplet at 1.30 ppm for 3 and 1.31 ppm for 4. The mass spectra of 3
and 4 confirmed the proposed structures. Molecular ion peaks
were easily identified at m/z = 624 [M]+ for 3 and 4.
Yield: 0.090 g (92%). M.p.: >300 °C. FT-IR (KBr),
m
max/(cmꢁ1):
3078 (Ar–CH), 2965 (aliphatic CH), 1708 (C@O, lactone), 1559
(C@C), 1422–1399 (Ar C@C), 1228 (Ar–O–Ar). 1H NMR (D2O,
500 MHz): 7.76–7.11 (m, 40H, Ar-H), 4.01–3.80 (m, 16H, –bCH2–),
2.28–2.23 (m, 16H, –dCH2–), 1.98–1.90 (m, 16H, –cCH2–). UV–Vis
kmax (DMF) (nm) (log
e): 329 (4.80), 636 (shoulder, 4.30), 697
(4.87). Anal. Calc. for C124H88N8O36ZnNa8: C, 59.21; H, 3.50; N,
4.46. Found: C, 59.34; H, 3.62; N, 4.55%. MS (MALDI-TOF, DHB as
matrix); m/z 2513, found: m/z 2513 [M]+.
2.2.9. 2(3), 9(10), 16(17), 23(24)-Tetrakis{7,8-di[sodium(4-
oxybutanoat)]-3-(4-oxyphenyl)coumarin}phthalocyaninato zinc (II)
(6a)
Yield: 0.092 g (94%). M.p.: >300 °C. FT-IR (KBr),
m
max/(cmꢁ1):
3057 (Ar–CH), 2965 (aliphatic CH), 1705 (C@O, lactone), 1558
(C@C), 1474–1422 (Ar C@C), 1237 (Ar–O–Ar). 1H NMR (D2O,
500 MHz): 7.81–7.06 (m, 40H, Ar-H), 4.01–3.81 (m, 16H, –bCH2–),
2.29–2.22 (m, 16H, –dCH2–), 1.98–1.88 (m, 16H, –cCH2–). UV–Vis
kmax (DMF) (nm) (log
e): 345 (4.93), 639 (shoulder, 4.50), 685
(4.81). Anal. Calc. for C124H88N8O36ZnNa8: C, 59.21; H, 3.50; N,
4.46. Found: C, 59.09; H, 3.42; N, 4.57%. MS (MALDI-TOF, DHB as
matrix); m/z 2513, found: m/z 2513 [M]+.
2.2.10. General procedure for the synthesis of butanoic acid derivatives
of zinc metallo phthalocyanines (5b and 6b)
Compound 5a or 6a (0.05 g, 0.02 mmol) was dissolved in water
and 1 M HCl was added until pH 2. The resulting green precipitate
was filtered and washed water and ethanol.
The sharp vibration for the C„N groups in the IR spectra of
phthalonitriles 3 and 4 at 2231 and 2227 cmꢁ1, respectively, disap-
peared after conversion into Zn (II) Pcs (5 and 6). The 1H NMR spec-
tra of Pc complexes (5, 6, 5a–b and 6a–b) showed aromatic
protons as multiplets. In the 1H NMR analyses of 5b and 6b, the
carboxylic acid protons appear as a broad singlet at 12.40 and
12.18 ppm, respectively. Integration of the peaks correctly corre-
sponded to the expected total number of protons for each complex.
In the mass spectra of Pc complexes (5, 6, 5a–b and 6a–b), the
presence of molecular ion peaks at m/z = 2561 [M]+ for 5 and 6,
m/z = 2513 [M]+ for 5a and 6a and m/z = 2337 [M]+ for 5b and 6b,
confirmed the proposed structures. The elemental analyses for all
complexes gave satisfactory results that were close to calculated
values.
2.2.11. 1(4), 8(11), 15(18), 22(25)-Tetrakis[7,8-di-(4-oxybutanoic
acid)-3-(4-oxyphenyl)coumarin]phthalocyaninato zinc (II) (5b)
Yield: 0.040 g (87%). M.p.: >300 °C. FT-IR (KBr),
m
max/(cmꢁ1):
3440 (carboxylic acid OH), 3070 (Ar–CH), 2944 (aliphatic CH),
1705 (C@O, lactone), 1604 (C@C), 1508–1452 (Ar C@C),
1281–1239 (Ar–O–Ar), 1121–1076 (Ar–O–C). 1H NMR (DMSO-d6,
500 MHz): 12.40 (br, s, 8H, –COOH), 8.22–8.08 (m, 8H, Ar-H),
8.03–7.82 (m, 8H, Ar-H), 7.66–7.51 (m, 10H, Ar-H), 7.45–7.38 (m,
4H, Ar-H), 7.33–6.88 (m, 10H, Ar-H), 4.08–4.00 (m, 16H, –bCH2–),
2.45–2.36 (m, 16H, –dCH2–), 2.02–1.87 (m, 16H, –cCH2–). UV–Vis
kmax (DMF) (nm) (loge): 348 (5.01), 628 (shoulder, 4.49), 693
(5.22). Anal. Calc. for C124H96N8O36Zn: C, 63.67; H, 4.11; N, 4.79.
Found: C, 63.58; H, 4.19; N, 4.70%. MS (MALDI-TOF, DHB as ma-
trix); m/z 2337, found: m/z 2337 [M]+.
2.2.12. 2(3), 9(10), 16(17), 23(24)-Tetrakis[7,8-di-(4-oxybutanoic
3.2. Electronic absorption spectra
acid)3-(4-oxyphenyl)coumarin]phthalocyaninato zinc (II) (6b)
Yield: 0.033 g (71%). M.p.: >300 °C. FT-IR (KBr),
m
max/(cmꢁ1):
The electronic spectra of the studied Zn(II) Pc complexes
showed characteristic absorption in the Q band region at around
678–697 nm in DMF, Table 1. The B bands were observed at around
330–355 nm (Fig. 1). The spectra showed monomeric behaviour
evidenced by a single Q band, typical of metallated Pc complexes
in DMF. The Q bands were observed at: 694 nm (for 5), 697 nm
(for 5a), 693 nm (for 5b), 679 nm (for 6), 685 nm (for 6a) and
678 nm (for 6b), Table 1. The red shifts were observed for Zn(II)
Pc complexes (5, 6, 5a–b and 6a–b) following substitution with
3436 (carboxylic acid OH), 3042 (Ar–CH), 2993 (aliphatic CH),
1710 (C@O, lactone), 1600 (C@C), 1506–1467 (Ar C@C),
1277–1228 (Ar–O–Ar), 1116–1073 (Ar–O–C). 1H NMR (DMSO-d6,
500 MHz): 12.18 (br, s, 8H, -COOH), 8.26–7.79 (m, 10H, Ar-H),
7.63–7.55 (m, 8H, Ar-H), 7.51–7.42 (m, 10H, Ar-H), 7.24–7.18 (m,
4H, Ar-H), 7.15–6.97 (m, 8H, Ar-H), 4.09–4.04 (m, 16H, –bCH2–),
2.46–2.36 (m, 16H, –dCH2–), 2.07–1.95 (m, 16H, –cCH2–). UV–Vis
kmax (DMF) (nm) (log
e): 356 (5.16), 616 (shoulder, 4.53), 678

M. Çamur et al. / Polyhedron 41 (2012) 92–103
95
OH
OH
HO
HO
O
O
O
O
CN
(1)
(2)
O
O
O
CN
CN
CN
O
O
Br
Br
a
O
a
K2CO3, DMF, Ar
Room temp., 4 days
K2CO3, DMF, Ar
Room temp., 4 days
O
O
O
O
O
O
b
c
c
b
O
O
d
d
O
O
O
O
O
O
O
O
CN
(3)
(4)
O
CN
O
CN
CN
Zn(AcO)2
Zn(AcO)2
Hexanol, DBU
Hexanol, DBU
160oC, 24 h
160oC, 24 h
OR
RO
OR
N
N
N
N
N
N
N
N
Zn
N
OR
O
O
Zn
N
O
RO
N
N
O
OR
N
N
N
N
O
O
O
O
OR
R=
OR
(6)
(5)
Scheme 1. Synthesis of phthalonitriles (3 and 4) and Zn(II) Pc complexes tetra substituted with 7,8-di-(ethyl 4-oxybutyrate)-3-(4-oxyphenyl)coumarin (5 and 6).
coumarin moieties (Q band is 670 nm for unsubstituted ZnPc in
DMF).
absorption also increased and there were no new bands (normally
blue shifted) due to the aggregated species. The studied Pc com-
plexes (5, 6, 5b and 6b) did not show aggregation in DMF. The com-
plexes 5a and 6a showed a little aggregation in DMF.
The Q bands of the non-peripheral substituted complexes are
red shifted when compared to the corresponding peripheral substi-
tuted complexes in DMF (Fig. 1). The red shifts are 15 nm between
5 and 6 or 5b and 6b, 12 nm between 5a and 6a. The observed red
shifts are typical of Pcs with substituents at the non-peripheral
positions and have been explained in the literatures [37,38]. In
phosphate-buffered saline (PBS), the absorption spectra of
butanoic acid bearing coumarin substituted Zn(II) Pc complexes
(5b and 6b) and their sodium salts (5a and 6a) showed cofacial
aggregation, as evidenced by the presence of two non-vibrational
peaks in the Q band region, Fig. 2. The lower energy (red-shifted)
bands at 700 nm for 5a, 703 nm for 5b, 697 nm for 6a and
690 nm for 6b are due to the monomeric species, while the higher
energy (blue-shifted) bands at 654 nm for 5a, 642 nm for 5b,
653 nm for 6a and 630 nm for 6b are due to the aggregated species.
The complexes 5a and 6a also showed a little aggregation in DMF
(Fig. 1). Addition of Triton X-100 (0.1 mL) to an solution in PBS of
butanoic acid bearing coumarin substituted Zn(II) Pc complexes
(5b and 6b) and their sodium salts (5a and 6a) (concentrations:
1.0 ꢀ 10ꢁ5 M) caused important increase in intensity of the low en-
ergy side of the Q band (Fig. 2), suggesting that the molecules are
aggregated and that addition of Triton X-100 breaks up the
aggregates.
3.3. Fluorescence spectra, fluorescence quantum yields and lifetimes
Fig. 4 shows fluorescence emission, absorption and excitation
spectra of complex 5 in DMF and complex 5b in PBS + Triton
X-100 solution as examples of the studied Zn(II) Pcs. Fluorescence
emission and excitation peaks were listed in Table 1. The studied
butanoic acid bearing coumarin substituted Zn(II) Pc complexes
(5b and 6b) and their sodium salts (5a and 6a) did not show fluo-
rescence emission in PBS. Sodium salts (5a and 6a) also did not
show fluorescence emission in DMF. Aggregated Pc complexes
are not known to fluorescence. The aggregation lowers the photo-
activity of molecules through dispersion of energy by aggregates
[7]. The addition of the Triton X-100 to the PBS solutions of com-
plexes increased the intensity of the fluorescence emission peaks
of the complexes. The excitation spectra were similar to absorption
spectra and both had mirror images of the fluorescent spectra for
Zn(II) Pc complexes (5, 6, 5b and 6b) in DMF (Fig. 4, for complexes
5 and 5b as examples). The proximity of the wavelength of every
ingredient of the Q band absorption to the Q band maxima of the
excitation spectra for Pc complexes (5, 6, 5b and 6b) proposed that
the nuclear configurations of the ground and excited states were
similar and not affected by excitation. The observed Stokes shifts
(Table 1) were typical of Zn(II) Pc complexes [39–42].
In this study, the aggregation behaviour of the Zn(II) Pc com-
plexes (5, 6, 5a–b and 6a–b) were investigated at different concen-
trations in DMF (Fig. 3, as an example for complex 5). In DMF, as
the concentration was increased, the intensity of the Q band

96
M. Çamur et al. / Polyhedron 41 (2012) 92–103
R1O
R2O
RO
OR1
OR2
OR
N
N
N
N
N
N
N
N
N
N
Zn
N
N
Zn
N
N
THF, NaOH
HCl
N
N
N
Zn
N
OR1
OR2
N
OR
N
N
N
N
N
OR1
OR2
OR
(5a)
(5b)
(5)
OR1
OR2
OR
N
N
N
N
N
N
N
N
N
N
N
N
Zn
N
THF, NaOH
OR1
OR2
OR
HCl
Zn
Zn
R1O
N
N
R2O
N
N
RO
N
N
N
N
N
N
N
OR1
OR2
OR
(6a)
(6b)
(6)
+
-
+
NaO
-
HO
O
O
O
O
O
NaO
HO
O
O
O
O
O
O
O
O
O
O
O O
O
O O
R=
R1=
R2=
Scheme 2. Synthesis of butanoic acid bearing coumarin substited Zn(II) Pc complexes (5b and 6b) and their sodium salts (5a and 6a).
Table 1
Absorption, excitation and emission spectral data for non-peripherally and peripherally substituted zinc(II) Pcs.
Compound
Solvent
Q band kmax, (nm)
log
e
Excitation kEx, (nm)
Emission kEm, (nm)
Stokes shift (nm)
5
6
5a
DMF
DMF
DMF
PBS
PBS + Triton X-100
DMF
PBS
PBS + Triton X-100
DMF
PBS
PBS + Triton X-100
DMF
PBS
694
679
697
654, 700
699
685
653, 697
682
693
642, 703
697
5.16
5.19
4.87
4.65
5.09
4.81
4.73
5.10
5.22
4.92
5.38
5.21
4.26
4.94
5.37
695
679
–
–
700
–
705
690
–
–
708
–
11
11
–
–
9
6a
5b
6b
–
–
–
–
685
694
–
698
679
–
692
704
–
709
688
–
10
11
–
12
10
–
678
630, 690
680
PBS + Triton X-100
DMF
681
670
691
676
11
6
ZnPca
670
a
Data from Ref. [39].
The fluorescence quantum yields (UF) of 5, 6, 5a–b and 6a–b
The sF values of non-peripherally substituted complexes (5, 5a
and 5b) were longer than peripherally substituted complexes (6,
6a and 6b) in both DMF and PBS + Triton X-100 solution. The nat-
are given in Table 2. Fluorescence quantum yield (UF) values for
5, 6, 5a–b and 6a–b are lower than those for unsubstituted Zn(II)
Pc in DMF, PBS and PBS + Triton X-100 solutions. Complexes 5
and 6 have higher fluorescence quantum yield (UF) values than
butanoic acid bearing coumarin substituted Zn(II) Pc complexes
(5b and 6b) in DMF and their sodium salts (5a and 6a) in PBS + Tri-
ton X-100 solution. This implies that the hydrolysis of the ester
groups of 5 and 6 caused some fluorescence quenching.
ural radiative lifetime (s0) values of substituted complexes (5, 6,
5a–b and 6a–b) were also longer when compared to unsubstituted
Zn(II) Pc in DMF. The rate constants for fluorescence (kF) of substi-
tuted complexes (5, 6, 5a–b and 6a–b) were lower than unsubsti-
tuted Zn(II) Pc in DMF.
Fluorescence lifetimes (
s
F) were calculated using the Strickler–
3.4. Singlet oxygen quantum yields
Berg equation. The sF values of the ethyl butyrate and butanoic
acid bearing coumarin substituted Zn(II) Pc complexes (5, 6, 5b
and 6b) were slightly longer than unsubstituted Zn(II) Pc in DMF.
Energy transfer between the triplet state of photosensitizers
and ground state molecular oxygen leads to the production of

M. Çamur et al. / Polyhedron 41 (2012) 92–103
97
Fig. 1. Absorption spectra of: (A) non-peripheral substituted Zn(II) Pc complexes (5, 5a and 5b) and (B) peripheral substituted Zn(II) Pc complexes (6, 6a and 6b) in DMF.
Concentration = 1.0 ꢀ 10ꢁ5 M.
singlet oxygen. There is an essentiality of high efficiency of transfer
of energy between excited triplet state of MPc and ground state of
oxygen to generate large amounts of singlet oxygen, necessary for
PDT.
complexes are lower when compared to unsubstituted Zn(II) Pc
UD = 0.56) in DMF except for 6 (UD = 0.56) and 6b (UD = 0.61).
(
The UD values of peripherally substituted complexes (6, 6a and
6b) are higher when compared to the non-peripherally substituted
complexes (5, 5a and 5b) in DMF, PBS or PBS + Triton X-100 solu-
tions (Table 2). The UD values of the butanoic acid bearing couma-
rin substituted Zn(II) Pcs (5b and 6b) were longer than ethyl
butyrate bearing coumarin substituted Zn(II) Pcs (5 and 6) in
DMF. Table 2 shows that lower UD values observed in PBS solutions
compared to in DMF. The addition of the Triton X-100 reduced the
aggregation and dramatically increased the UD values of complexes
in PBS. The UD of butanoic acid bearing coumarin substituted Zn(II)
Pcs and their sodium salts were 0.90 for 5b, 0.91 for 6b, 0.65 for 5a
and 0.93 for 6a in PBS + Triton X-100 solution while carboxyl poly-
meric Zn(II) Pc was 0.55 in pH 7.4 buffer solution [43] and
ZnPc(COOH)8 had a UD about 0.52 at pH 10 [44] in the literature.
The UD of butanoic acid bearing coumarin substituted Zn(II) Pcs
(5b and 6b) and their sodium salts (5a and 6a) are also higher when
Singlet oxygen quantum yields (UD), give a sign of the potential
of the complexes as photosensitizers in applications where singlet
oxygen is needed, (e.g. for Type II mechanism). The UD values were
determined in DMF, PBS and PBS + Triton X-100 solutions using a
chemical method using DPBF or ADMA as a quencher. The disap-
pearance of DPBF (or ADMA) spectra was monitored using UV–Vis
spectrophotometer. Many factors are responsible for the magnitude
of the determined quantum yield of singlet oxygen including; trip-
let excited state energy, ability of substituents and solvents to
quench the singlet oxygen, the triplet excited state lifetime and
the efficiency of the energy transfer between the triplet excited
state and the ground state of oxygen. There was no decrease in
the Q band of formation of new bands during UD determinations,
confirming that complexes were not degraded during singlet oxy-
gen studies (Fig. 5A as an example for 6b in DMF and Fig. 5B as
an example for 5a in PBS + Triton X-100). The UD values of studied
compared to ZnPcSmix
(UD = 0.45) in aqueous solution. The large
UD of 5a–b and 6a–b in PBS + Triton X-100 solution indicated they

98
M. Çamur et al. / Polyhedron 41 (2012) 92–103
Fig. 2. Absorption spectra of: (A) sodium salt of Zn(II) Pc complexes (5a and 6a) and (B) butanoic acid bearing coumarin substituted Zn(II) Pc complexes (5b and 6b) in PBS
and PBS + Triton X-100 solutions. Concentration = 1.0 ꢀ 10ꢁ5 M.
Fig. 3. Absorption spectral changes of complex 5 in DMF at different concentrations. 1.2 ꢀ 10ꢁ5 (A), 1.0 ꢀ 10ꢁ5 (B), 8.0 ꢀ 10ꢁ6 (C), 6.0 ꢀ 10ꢁ6 (D), 4.0 ꢀ 10ꢁ6 (E), 2.0 ꢀ 10ꢁ6 (E)
M. (Inset: Plot of absorbance versus concentration).

M. Çamur et al. / Polyhedron 41 (2012) 92–103
99
Fig. 4. Absorption, excitation and emission spectra of: (A) complex
5 in DMF and (B) complex 5b in PBS + Triton X-100. Excitation wavelengths: 660 nm.
Concentration = 2.0x10ꢁ6 M.
can produce singlet oxygen in high efficiency, which facilitated to
strong cytotoxicity in photodynamic therapy; or high oxidization
capacity in photocatalysis [43].
decay rates did not observe in the B band in the UV region due
to the visible light irradiation (near the Q band regions of com-
plexes) was used for photodegradation studies. All the studied
Zn(II) Pc complexes showed about the same stability with Ud of
the order of 10ꢁ4. Stable Zn(II) Pc complexes show Ud values as
low as 10ꢁ6 and for unstable molecules, values of the order of
10ꢁ3 have been reported [7]. It seems studied Pc complexes show
also similar Ud values and stability to the known Zn(II) Pc
complexes.
3.5. Photodegradation studies
Degradation of the molecules under irradiation can be used to
study their stability and this is particularly important for those
molecules intended for use as photocatalysts. The collapse of the
absorption spectra without any distortion of the shape confirms
clean photodegradation not associated with phototransformation
into different forms of MPc absorbing in the visible region.
3.6. Fluorescence quenching studies by 1,4-benzoquinone (BQ)
Table 2 shows that all substituted complexes (5, 6, 5a, 5b and
6a, 6b) were more stable to degradation compared to unsubstitut-
ed Zn(II) Pc in DMF. Fig. 6 (as an example for 5) shows that for
Zn(II) Pc complexes, there was a change in spectra following pho-
todegradation. The spectral changes involved a decrease in the Q
band in the visible region for substituted complexes. The similar
The fluorescence quenching of Zn(II) Pc 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 6b by BQ in DMF solution. The slope of
the plots shown in inset of Fig. 7 gave KSV value, listed in Table
3. The KSV values of the peripherally and non-peripherally substi-

100
M. Çamur et al. / Polyhedron 41 (2012) 92–103
Table 2
Photophysical and photochemical parameters of non-peripherally and peripherally substituted zinc(II) Pcs.
Compound
Solvent
UF
sF (ns)
s0 (ns)
akF (sꢁ1) (x109)
Ud (ꢀ10ꢁ4
)
UD
5
6
5a
DMF
DMF
DMF
PBS
PBS + Triton X-100
DMF
PBS
PBS + Triton X-100
DMF
PBS
PBS + Triton X-100
DMF
PBS
0.12
0.12
–
–
0.04
–
1.27
1.14
–
–
0.60
–
10.57
8.95
–
0.12
0.12
–
–
0.07
–
14.98
12.74
1.70
0.19
1.52
0.46
0.56
3.29
13.10
0.24
2.20
8.49
0.25
3.02
0.23
0.45
0.56
0.10
0.06
0.65
0.12
0.05
0.93
0.53
0.03
0.90
0.61
0.02
0.91
0.56
–
14.29
–
–
12.40
9.43
–
7.81
8.80
–
6a
–
–
–
0.04
0.11
–
0.07
0.10
–
0.52
1.08
–
1.05
1.04
–
0.08
0.11
–
0.13
0.11
–
5b
6b
PBS + Triton X-100
DMF
0.06
0.17
0.55
1.03
17.43
6.05
0.06
0.17
ZnPcb
a
kF is the rate constant for fluorescence. Values calculated using kF
Data from Ref. [39].
= UF/sF.
b
Fig. 5. Absorbance changes for the determination of singlet oxygen quantum yield of: (A) complex 6b in DMF using DPBF as a singlet oxygen quencher and (B) complex 5a in
PBS + Triton X-100 using ADMA as a singlet oxygen quencher. Concentration = 1.0 ꢀ 10ꢁ5 M. (Inset: plots of DPBF or ADMA absorbance versus time).

M. Çamur et al. / Polyhedron 41 (2012) 92–103
101
Fig. 6. Absorbance changes during the photodegradation study of complex 5 in DMF showing the disappearance of the Q band at 30 s intervals. Concentration = 1.0 ꢀ 10ꢁ5 M.
(Inset: plot of Q band absorbance versus time).
Fig. 7. Fluorescence emission spectral changes of 6b (1.0 ꢀ 10ꢁ5 M) on addition of different concentrations of BQ in DMF. [BQ] = 0, 0.008, 0.016, 0.024, 0.032, 0.040 M. (Inset:
Stern–Volmer plots for BQ quenching of 5, 6, 5b and 6b in DMF).
Table 3
Fluorescence quenching data for Pcs by BQ in DMF and binding data for interaction of BSA with water soluble zinc(II) Pcs in PBS and
PBS + Triton X-100 solutions.
Kb /10ꢁ6 (Mꢁ1
)
n
BQ
SV
BSA
SV
K
(Mꢁ1
)
K
/105 (Mꢁ1
)
KBqQ /108 (Mꢁ1 sꢁ1
)
KBqSA/1013 (Mꢁ1 sꢁ1
)
Compound
Solvent
5
6
5a
6a
5b
DMF
DMF
PBS
PBS
DMF
PBS
19.91
24.36
–
–
–
2.46
4.36
–
7.12
–
4.73
1.57
2.35
–
–
3.65
–
–
–
–
–
–
–
2.46
4.36
–
7.12
–
4.79
3.02
–
1.91
–
1.33
1.38
–
1.20
–
–
37.82
–
39.13
–
6b
DMF
PBS
4.45
–
4.73
2.63
1.28
tuted Zn(II) Pc complexes (5, 6, 5b and 6b) were lower than unsub-
stituted Zn(II) Pc (KSV = 57.60 Mꢁ1). The substitution with couma-
rin seems to decrease the KSV values of the complexes in DMF.
The bimolecular quenching constant (kq) values of the substituted
Zn (II) Pc complexes ( 5, 6, 5b and 6b) were also lower than for
unsubstituted Zn(II) Pc (kq = 5.59 ꢀ 108 Mꢁ1sꢁ1).

102
M. Çamur et al. / Polyhedron 41 (2012) 92–103
Fig. 8. Fluorescence emission spectral changes of BSA (3.0 ꢀ 10ꢁ5 M) on addition of varying concentrations of complex 5b in PBS. [Pc] = 0, 1.66 ꢀ 10ꢁ6, 3.33 ꢀ 10ꢁ6
5.00 ꢀ 10ꢁ6, 6.66 ꢀ 10ꢁ6, 8.33 ꢀ 10ꢁ6 M. (Inset: Stern–Volmer plots of complexes 5a, 6a, 5b and 6b quenching of BSA in PBS).
,
Fig. 9. Determination of complexes 5a, 6a, 5b and 6b – BSA binding constant and number of binding sites on BSA. [BSA] = 3.0 ꢀ 10ꢁ5 M and [Pc] = 0, 1.66 ꢀ 10ꢁ6, 3.33 ꢀ 10ꢁ6
5.00 ꢀ 10ꢁ6, 6.66 ꢀ 10ꢁ6, 8.33 ꢀ 10ꢁ6 M in PBS.
,
3.7. Interaction of water soluble zinc(II) Pc complexes with BSA
mate fluorescence lifetime of BSA (10 ns) [45,46], the bimolecular
quenching constant (kq) was determined using Eq. (9) (Supporting
information). Diffusion-controlled quenching typically results in
values of kq near 1 ꢀ 10ꢁ10 Mꢁ1 sꢁ1. Values of kq smaller than the
diffusion-controlled value can results from steric shielding of fluo-
rophores or a low quenching efficiency. Apparent values of kq larger
than the diffusion-controlled limit usually indicate some type of
Fig. 8 shows the fluorescence emission spectra of BSA in the
presence of different concentrations of 5b in PBS. The BSA fluores-
cence at 348 nm is mainly attributable to tryptophan residues in
the macromolecule. BSA and the respective water soluble Pc com-
plexes (5a, 5b, 6a and 6b) showed reciprocated fluorescence
quenching on one another; therefore it was possible to determine
Stern–Volmer quenching constants (KSV). The slope of the plots
shown in inset of Fig. 8 gave KSV values and listed in Table 3.
Stern–Volmer (SV) plots (Fig. 8) for the water-soluble ZnPc com-
plexes in PBS were linear with R2 values very close to unity. The
linearity of these plots indicates that fluorescence quenching is rea-
sonably described by a collisional quenching mechanism. It sug-
gested that BSA fluorescence quenching was more effective for
butanoic acid bearing coumarin substituted Pc complexes (5b and
6b) than their sodium salts (5a and 6a) in PBS. Using the approxi-
binding interaction. These values are of the order of 1013 Mꢁ1 sꢁ1
,
which exceed the proposed value of 1010 Mꢁ1 sꢁ1 for diffusion-
controlled (dynamic) quenching (according to the Einstein–Smolu-
chowski approximation) at room temperature [47]. This also is an
indication that the mechanism of BSA quenching by water soluble
Pc complexes (5a, 5b, 6a and 6b) is not diffusion-controlled (i.e.,
not dynamic quenching, but static quenching). The kq values are
higher for butanoic acid bearing coumarin substituted Pc com-
plexes (5b and 6b) than their sodium salts (5a and 6a) in PBS. The
binding constants (Kb) and number of binding sites (n) on BSA were

M. Çamur et al. / Polyhedron 41 (2012) 92–103
103
obtained using Eq. (7) (Supporting information) and the results are
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This work described the synthesis, characterization, spectral,
photophysical and photochemical properties of new Zn(II) Pcs tetra
substituted with 7,8-di-(ethyl 4-oxybutyrate)-3-(4-oxyphenyl)
coumarin (5 and 6), 7,8-di-(sodium 4-oxybutanoat)-3-(4-oxyphe-
nyl)coumarin (5a and 6a) and 7,8-di-(4-oxybutanoic acid)-3-
(4-oxyphenyl)coumarin (5b and 6b) substituents at non-peripheral
or peripheral positions on Pc structure. Butanoic acid bearing cou-
marin substituted Pc complexes and their sodium salts were
shown to be excellent solubility in water. Solvent effect (DMF,
PBS or PBS + Triton X-100) on the photophysical and photochemi-
cal properties of the Pc complexes was determined. Ethyl butyrate
or butanoic acid bearing coumarin substituted Pc complexes were
found to be monomeric in DMF. Their sodium salts showed a little
aggregation in DMF. The butanoic acid bearing coumarin substi-
tuted Pc complexes and their sodium salts showed aggregation in
PBS. All studied Zn(II) Pc complexes showed similar fluorescence
behaviour with MPcs in DMF. The value of UD ranged from 0.10
to 0.61 in DMF, from 0.02 to 0.06 in PBS and from 0.65 to 0.93 in
PBS + Triton X-100 solution gives an indication of the potential of
these complexes as photosensitizers for PDT of cancer. This study
reveals that the water-soluble derivatives bind strongly to serum
albumin; therefore they can easily transferred in the blood. After
injection into the blood stream, these molecules will have to
encounter serum albumin, which presents a reason for their BSA
binding study. This work will definitely improve the hitherto lim-
ited literature on the potentials of water soluble coumarin substi-
tuted Pcs as photosensitizers in PDT.
Acknowledgements
We are thankful to the Research Foundation of Marmara
University, Commission of Scientific Research Project (BAPKO)
[FEN-C-YLP-210311-0061] for supporting this study.
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Appendix A. Supplementary data
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.poly.2012.04.034.