Tetra-3-[(2-diethylamino)ethyl]-7-oxo-4-methylcoumarin-substituted zinc phthalocyanines: Synthesis, characterization and aggregation effects on photophysical/photochemical properties

Article abstract of DOI:10.1016/j.jphotochem.2010.05.021

A synthesis of a novel zinc phthalocyanine with four 3-[(2-diethylamino) ethyl]-7-oxo-4-methylcoumarin dye groups at the non-peripheral positions was performed and characterized. The photophysical and photochemical properties of the peripherally (p) and non-peripherally (np) tetra-3-[(2-diethylamino)ethyl]- 7-oxo-4-methylcoumarin substituted zinc (II) phthalocyanines are reported. The effects of the position of the substituents and the aggregation on the photophysical/photochemical properties of these complexes are also investigated. General trends are described for photodegredation, singlet oxygen and fluorescence quantum yields, and fluorescence lifetimes in dimethylsulphoxide (DMSO) for np-ZnPc and in both DMSO and DMSO + Triton-X 100 solutions for p-ZnPc. The fluorescence of the tetra-substituted zinc phthalocyanine complexes (np-ZnPc and p-ZnPc) are effectively quenched addition of 1,4-benzoquinone (BQ).

Full text of DOI:10.1016/j.jphotochem.2010.05.021

Journal of Photochemistry and Photobiology A: Chemistry 213 (2010) 171–179
Contents lists available at ScienceDirect
Journal of Photochemistry and Photobiology A:
Chemistry
journal homepage: www.elsevier.com/locate/jphotochem
Tetra-3-[(2-diethylamino)ethyl]-7-oxo-4-methylcoumarin-substituted zinc
phthalocyanines: Synthesis, characterization and aggregation effects on
photophysical/photochemical properties
Aliye Aslı Esenpınara, 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:
A synthesis of a novel zinc phthalocyanine with four 3-[(2-diethylamino)ethyl]-7-oxo-4-methylcoumarin
dye groups at the non-peripheral positions was performed and characterized. The photophysical
and photochemical properties of the peripherally (p) and non-peripherally (np) tetra-3-[(2-
diethylamino)ethyl]-7-oxo-4-methylcoumarin substituted zinc (II) phthalocyanines are reported. The
effects of the position of the substituents and the aggregation on the photophysical/photochemical prop-
erties of these complexes are also investigated. General trends are described for photodegredation, singlet
oxygen and fluorescence quantum yields, and fluorescence lifetimes in dimethylsulphoxide (DMSO) for
np-ZnPc and in both DMSO and DMSO + Triton-X 100 solutions for p-ZnPc. The fluorescence of the tetra-
substituted zinc phthalocyanine complexes (np-ZnPc and p-ZnPc) are effectively quenched addition of
1,4-benzoquinone (BQ).
Received 25 February 2010
Received in revised form 10 May 2010
Accepted 31 May 2010
Available online 8 June 2010
Keywords:
Coumarin (2H-chromen-2-one)
Fluorescence
Phthalocyanine
Quantum yield
Singlet oxygen
Zinc
© 2010 Elsevier B.V. All rights reserved.
1. Introduction
On the other hand, coumarin (2H-1-benzopyran-2-one, 2H-
chromen-2-one) and its derivatives are biologically active sub-
Since their accidental synthesis in 1928, phthalocyanines (Pcs)
have enjoyed considerable industrial importance as dyes, paints
and color for metal surfaces, fabrics and plastics. In recent years,
various Pc complexes have been synthesized, characterized and
investigated in terms of their properties [1,2]. Pcs are highly stable
and versatile aromatic macrocyclic compounds, capable of includ-
ing more than 70 metallic and non-metallic ions in the ring cavity.
The optical and electronic properties of the phthalocyanine macro-
cycles make them suitable for a wide range of applications [3].
Some technological applications of these macrocycles have been
intensively investigated, such as dyes and pigments [4], light emit-
ting diodes [5], in optical limiting devices [6–8], in molecular
electronics [9], for non-linear optical applications [10], as liquid
crystals [11,12], gas sensors [13], semiconductor materials [14], in
photovoltaic cells [15,16], photodynamic therapy [17–20] and for
electrochromic displays [21,22]. Numerous studies have been per-
formed to modify these macrocyclic compounds with the goal of
tuning their properties and utilizing their efficacy for the above
applications [23–25].
stances with numerous metabolites, and widespread in nature [26].
Some coumarin derivatives were used as anticoagulants, additives
in food and cosmetics, reagents in the preparation of insecticides
and as optical brighteners [27–32]. Coumarins are one kind of
significant organic fluorescent chromophores and widely used in
synthesizing laser dyes, fluorescent whiteners, organic nonlinear
optical materials and so on [33].
Some of the coumarin derivatives show anti-clotting activity
[34,35]. For example, carbochromen (3-diethylaminoethyl-7-
ethoxycarbonylmethoxy-4-methylcoumarin) is a potent specific
coronary vasodilator used for many years in the treatment of angina
pectoris [27,36]. A number of coumarin metal complexes have been
synthesized and their biological activities have been determined
[37].
A major disadvantage of Pcs is their low solubility in com-
mon organic solvents or in water. Their insolubility causes
difficulties for many applications rendering the syntheses of sol-
uble derivatives an important task. Peripheral substitution with
bulky groups or long alkyl, alkoxy or alkylthio chains leads to
phthalocyanine products which are soluble in apolar solvents
[1].
In view of the biological importance of both coumarins and Pcs
it is worthwhile to combine these two functional molecules into
a single compound and combine via synthetic methodology and
∗
Corresponding author. Tel.: +90 216 3479641x1370; fax: +90 216 3478783.
E-mail addresses: mbulut@marmara.edu.tr, mustafabulut50@gmail.com
(M. Bulut).
1010-6030/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jphotochem.2010.05.021

172
A.A. Esenpınar et al. / Journal of Photochemistry and Photobiology A: Chemistry 213 (2010) 171–179
n2Std are the refractive indices of solvents for the sample and stan-
dard, respectively. Unsubstituted ZnPc (in DMSO) (˚F = 0.20) [43]
was employed as the standard. Both the sample and standard were
excited at the same wavelength. The absorbance of the solutions
was ranged between 0.04 and 0.05 at the excitation wavelength.
Natural radiative lifetimes (ꢀ0) were determined using Pho-
tochem CAD program which uses the Strickler–Berg equation [44].
The fluorescence lifetimes (ꢀF) were evaluated using Eq. (2).
prepare and characterize their ZnPc derivatives, which may also
exhibit biological activities.
In this work, we report the synthesis and characterization of a
newly synthesized non-peripherally ZnPc bearing four substituents
of 3-[(2-diethylamino)ethyl]-7-oxy-4-methylcoumarin. Photode-
gredation, singlet oxygen and fluorescence quantum yields, and
fluorescence lifetimes are investigated for np-ZnPc in DMSO and
for p-ZnPc in DMSO and DMSO + Triton-X 100. The effects of
the central metal atom, substitution position and aggregation on
the photophysical and photochemical properties of studied com-
pounds are investigated. The fluorescence quenching properties of
these complexes are also reported. The combined structures of the
coumarin and Pc can be a potential candidate for the application of
PDT.
ꢀF
˚
F
=
(2)
ꢀ0
2.4. Photochemical parameters
2.4.1. Singlet oxygen quantum yields
Singlet oxygen quantum yield (˚ꢁ) determinations were car-
ried out by using the experimental set-up described in literature
[45–47]. Typically, 3 mL portion of the respective unsubstituted,
peripherally and non-peripherally tetra- substituted zinc (II)
phthalocyanine (ZnPc, np-ZnPc and p-ZnPc) solutions (concen-
tration = 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 [45–47]. ˚ꢁ was determined in air using
the relative method using ZnPc (in DMSO) as a reference. DPBF was
used as chemical quenchers for singlet oxygen in DMSO. Eq. (3) was
2. Experimental
2.1. Materials
All reagents and solvents were of reagent grade quality and were
obtained from commercial suppliers. 3-[(2-Diethylamino)ethyl]-
7-hydroxy-4-methylcoumarin hydrochloride was purchased
from the Aldrich Chemical Company. 1,3-Diphenylisobenzofuran
(DPBF) was purchased from Fluka. 1,2-Dicyano-3-nitrobenzene
[38], 1,2-dicyano-4-nitrobenzene [39], 3-[(2-diethylamino)ethyl]-
7-[(2,3-dicyanophenoxy)]-4-methylcoumarin
and 2(3),9(10),16(17),23(24)-tetrakis[7-oxo-(3-
[(2-diethylamino)ethyl)]-4-methylcoumarin]-phthalocyanine
(p-ZnPc) [40] were synthesized and purified according to well
known literature.
employed for the calculations of ˚ꢁ
:
(1)
Std
R · I
abs
RStd · Iabs
˚
= ˚Std
(3)
ꢁ
ꢁ
where ˚Sꢁtd is the singlet oxygen quantum yields for the standard
ZnPc (˚Sꢁtd = 0.67 in DMSO) [48]. R and RStd are the DPBF photo-
2.2. Equipment
bleaching rates in the presence of the respective samples (np-ZnPc
Std
abs
and p-ZnPc) and standard, respectively. Iabs and I
are the rates
The IR spectra were recorded on a Shimadzu Fourier Trans-
form FTIR-8300 using KBr pellets. 1H NMR spectra were recorded
on a Varian 500 MHz spectrometer in CDCl3 at Gebze Institute
of Technology. Elemental analysis 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 Daltonic Autoflex III MALDI-TOF spectrome-
ter at Marmara University. Absorption spectra in the UV–vis region
were recorded with a Shimadzu 2001 UV and Shimadzu UV-1601
spectrophotometers. Fluorescence excitation and emission spectra
were recorded on a Varian Eclipse spectrofluorometer using 1 cm
pathlength cuvettes at room temperature.
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.
of light absorption by the samples (np-ZnPc and p-ZnPc) and stan-
dard, respectively. To avoid chain reactions induced by DPBF in the
presence of singlet oxygen [49], the concentration of quencher was
lowered to ∼3 × 10−5 M. Solutions of sensitizer containing DPBF
was prepared in the dark and irradiated in the Q band region using
the above set-up. DPBF degradation at 417 nm was monitored. The
light intensity was 6.66 × 1015 photons/s cm2 for ˚ꢁ determina-
tions.
2.4.2. Photodegredation quantum yields
Determinations of photodegredation quantum yield (˚d) were
carried out as previously described in the literature [45–47]. ˚d
was determined using Eq. (4),
(C0 − Ct)VNA
˚
=
(4)
d
IabsSt
where C0 and Ct are the samples (np-ZnPc and p-ZnPc) con-
centrations before and after irradiation, respectively, V, NA, S,
t and Iabs are reaction volume, the Avogadro’s constant, irradi-
ated cell area, irradiation time and the overlap integral of the
radiation light source intensity, respectively. A light intensity of
2.22 × 1016 photons/s cm2 was employed for ˚d determinations.
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) [41,42]
2.4.3. Fluorescence quenching by 1,4-benzoquinone (BQ)
Fluorescence quenching experiments on the substituted ZnPc
derivatives (np-ZnPc and p-ZnPc) were carried out by the addi-
tion of different concentrations 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 M. The fluorescence
spectra of substituted ZnPc derivatives (np-ZnPc and p-ZnPc) at
each BQ concentration were recorded, and the changes in fluores-
cence intensity related to BQ concentration by the Stern–Volmer
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 (np-ZnPc and p-ZnPc) and the standard,
respectively. A and AStd are the relative absorbance of the sam-
ple and standard at the excitation wavelength, respectively. n2 and

A.A. Esenpınar et al. / Journal of Photochemistry and Photobiology A: Chemistry 213 (2010) 171–179
173
(S–V) equation [50] as shown in Eq. (5):
2.5.3. 2(3),9(10),16(17),23(24)-Tetrakis[7-oxo-(3-[(2-
diethylamino)ethyl)]-4-methylcoumarin]-phthalocyanine
(p-ZnPc)
This phthalocyanine complex was synthesized according to lit-
erature procedure [40].
I0
= 1 + KSV[BQ]
(5)
I
where I0 and I are the fluorescence intensities of fluorophore in the
absence and presence of quencher, respectively. [BQ] is the con-
centration of the quencher and KSV is the Stern–Volmer constant
which is the product of the bimolecular quenching constant (kq)
and the ꢀF and is expressed in Eq. (6).
Compound p-ZnPc: Yield: 0.040 g (77%); m.p.: >300 ◦C. IR ꢂmax
(cm−1): 3051 (aryl CH), 2916-2947 (alkyl CH), 1701 (C O lactone),
1604, 1465 (C C), 1238 (Ar–O–Ar). UV–vis (DMF) ꢃmax (log ε) (nm):
679 (4.08), 617 (4.38), 337 (4.56). Anal. Calcd. for C96H92 N12O12Zn:
C 69.02; H 5.51; N 10.06%. Found: C 68.16; H 5.59; N 9.84%. MS
(MALDI-TOF) m/z: 1669 [M]+, 1670 [M+1]+
KSV = kq · ꢀF
(6)
3. Result and discussion
The ratios of I0/I were calculated and plotted against [BQ]
according to Eq. (5), and KSV is determined from the slope.
3.1. Syntheses and characterization
2.5. Synthesis
3-[(2-Diethylamino)ethyl]-7-[(2,3-dicyanophenoxy)]-4-
methylcoumarin (1) was prepared by K2CO3 catalyzed nucleophilic
aromatic nitro displacement of 1,2-dicyano-3-nitrobenzene
2.5.1. 3-[(2-Diethylamino)ethyl]-7-[(2,3-dicyanophenoxy)]-4-
methylcoumarin
(1)
3-[(2-Diethylamino)ethyl]-7-hydroxy-4-methylcoumarin
hydrochloride
nitrobenzene (0.277 g, 1.60 mmol) were added successively
with stirring to dry dimethylformamide (DMF) (10 mL) and
DMSO (5 mL). After stirring for 15 min, finely ground anhydrous
K2CO3 (0.332 g, 2.40 mmol) was added portionwise over 2 h.
After heating (50 ◦C) and stirring for 5 days under nitrogen the
reaction mixture was poured into iced water and acidified with
aqueous HCl solution. The precipitate formed was filtered, washed
with water until neutral and the crude product was dried. The
yellow product (1) obtained as pure. The compound is soluble in
ethanol, methanol, tetrahydrofuran, chloroform, dichloromethane,
dimethylformamide and dimethylsulfoxide.
with
3-[(2-diethylamino)ethyl]-7-hydroxy-4-methylcoumarin
hydrochloride in DMF/DMSO (2/1) under N2 atmosphere at room
temperature and the yield was 87%.
(0.500 g,
1.60 mmol)
and
1,2-dicyano-3-
Cyclotetramerization of the phthalonitrile derivative (1) was
accomplished in anhydrous 2-N,N-dimethylaminoethanol (DMAE)
in the presence of anhydrous Zn(CH3COO)2 salt at 145 ◦C afford-
ing np-ZnPc (Fig. 1). The p-ZnPc was prepared according to the
literature [40] (Fig. 2). The tetraoxycoumarin substituted np-ZnPc
was purified on silica gel column chromatography with chloroform
as an eluent. Characterization of the products involved a combina-
tion of methods including elemental analysis, 1H NMR, IR, UV–vis,
fluorescence and MALDI-TOF spectroscopy.
Spectral data of the newly synthesized compounds are consis-
tent with the proposed structures. The IR spectrum of compound
1 clearly indicates the appearance of the new absorption bands
at 2230 cm−1 (C≡N) and 1278 cm−1 (Ar–O–Ar). After reaction of
the dinitrile derivative (1), the sharp peak for the C≡N vibration
around 2230 cm−1 disappeared and the color of the reaction was
converted to green. The C O and C C bands for np-ZnPc in IR spec-
tra was broader and shorter than those of 1 because of the H-type
aggregation of coumarin moiety.
Compound 1: Yield: 0.562 g (87%); m.p.: 150–153 ◦C. IR (KBr pel-
let) ꢂmax (cm−1): 3075 (aryl CH), 2810–2919 (alkyl CH), 2230 (C≡N),
1709 (C O lactone), 1614 and 1572 (C C), 1278 (Ar–O–Ar). 1H NMR
(CDCl3) ıH: 7.87 (t, 1H, Ar–H), 7.80 (d, 8 Hz, 1H, Ar–H), 7.60 (dd,
8 Hz, 3 Hz, 1H, Ar–H), 7.54 (dd, 8 Hz, 2 Hz, 1H, Ar–H), 7.12 (d, 8 Hz,
1H, Ar–H), 7.10 (dd, 8 Hz, 2 Hz, 1H, Ar–H), 3.41 (t, 2H, ArCH2CH2),
3.01 (q, 4H, NCH2), 2.06 (t, 2H, ArCH2), 2.42 (s, 3H, CH3), 1.02 (t,
6H, NCH2CH3). UV–vis ꢃmax (nm) (log ε) (THF) (1.061 × 10−5 M):
316 (4.18). Anal. Calcd. for C24H23N3O3: C 71.82; H 5.73; N 10.47%.
Found: C 70.94; H 5.02; N 10.41%. MS (MALDI-TOF) m/z: 401 [M]+,
402 [M+1]+.
The 1H NMR spectrum of 1 exhibited aromatic protons at
7.87, 7.80, 7.60, 7.54, 7.12, 7.10 ppm and aliphatic protons at
3.41 ppm ArCH2CH2, 3.01 ppm NCH2, 2.06 ppm ArCH2, 2.42 ppm
CH3, 1.02 ppm NCH2CH3.
The mass spectra of np-ZnPc confirmed the proposed struc-
ture. The [M+] peak was identified easily. The MALDI-TOF MS
spectra provided definitive characterization of the structure of
newly synthesized compounds. Linear mode positive ion MALDI
mass spectra were obtained in 7-hydroxycoumarin (umbelliferone)
MALDI matrix. The protonated molecular ion peak of the complex
np-ZnPc was observed at 1669 Da.
2.5.2. 1(4)-Tetrakis-[7-oxo-(3-[(2-diethylamino)ethyl)]-4-
methylcoumarin]-phthalocyaninato zinc (II)
(np-ZnPc)
The mixture of compound 1 (0.1 g, 0.25 mmol) and anhydrous
Zn(CH3COO)2 (0.014 g, 0.06 mmol) was heated at 145 ◦C with 2 mL
of dry 2-N,N-dimethylaminoethanol in a sealed tube, and stirred for
24 h. After cooling to room temperature, the reaction mixture was
treated with acetone, the precipitate then filtered off and washed
with water to remove unreacted Zn(CH3COO)2. The green product
was purified on silica gel column chromatography with chloroform
as eluent. The compound is soluble in chloroform, dimethylfor-
mamide and dimethylsulfoxide.
3.2. Electronic absorption spectroscopic properties
The electronic spectra of the non-peripherally tetra-substituted
phthalocyanine complex (np-ZnPc) showed intense Q absorption
band at 693 nm (Fig. 3) in DMSO. The spectrum showed monomeric
behaviour evidenced by a single (narrow) Q band, typical for met-
allated phthalocyanine complexes [51]. In DMSO, the absorption
spectra of peripherally tetra-substituted compound (p-ZnPc) indi-
cate its co-facial aggregation, as evidenced by the presence of two
peaks in the Q band region (Fig. 3, Table 1). The lower energy
(red-shifted) band at 678 nm is due to the monomeric species,
while the higher energy (blue-shifted) band at 639 nm is due to the
aggregated species. The addition of surfactants such as Triton-X
Compound np-ZnPc: Yield: 0.045 g (43%); m.p.: >300 ◦C. IR (KBr
pellet) ꢂmax (cm−1): 3058 (aryl CH), 2916-2974 (alkyl CH), 1706
(C=O lactone), 1616, 1581 (C C), 1244 (Ar–O–Ar). UV–vis ꢃmax
(log ε) (nm) (DMF) (1.271 × 10−5 M): 687 (4.87), 312 (4.56). Anal.
Calcd. for C96H92 N12O12Zn: C 69.02; H 5.51; N 10.06%. Found:
C 68.76; H 5.59; N 9.84%. MS (MALDI-TOF) m/z: 1669 [M]+, 1670
[M+1]+.

174
A.A. Esenpınar et al. / Journal of Photochemistry and Photobiology A: Chemistry 213 (2010) 171–179
Fig. 1. Synthesis route of the non-peripherally tetra-3-[(2-diethylamino)ethyl]-7-oxo-4-methylcoumarin-substituted zinc (II) phthalocyanines complex (np-ZnPc).
100 can reduce aggregation. The aggregated molecules are dis-
sociated thanks to the intercalation of the surfactant. Addition
of Triton-X 100 (0.1 mL) to DMSO solution of the peripherally
tetra-substituted zinc phthalocyanine complex (p-ZnPc) (con-
centration = 1.0 × 10−5 M) brings about considerable increase in
intensity of the low energy side of the Q band (Fig. 4), suggesting
that the molecules are aggregated and that addition of Triton-X 100
enhances monomerization. The electronic spectra of the peripher-
ally tetra-substituted phthalocyanine complex (p-ZnPc) showed
intense Q absorption band at 677 nm (Fig. 4) in DMSO + Triton-X
100 solution.
In DMSO, the Q bands were observed at 672 nm (ZnPc), 693 nm
(np-ZnPc), 678 nm (p-ZnPc) (Table 1). The Q band was observed
at 677 nm for complex p-ZnPc in DMSO + Triton-X 100 solution
(Table 1). Thus substitution of the ZnPc with coumarin sub-
stituents increased the wavelength of the Q band. The Q band of
the non-peripherally tetra-substituted compound (np-ZnPc) was
red-shifted 15 nm compared to the peripherally tetra-substituted
complex (p-ZnPc) in DMSO (Table 1). The observed red spec-
tral shift is typical of phthalocyanines with substituents at the
non-peripheral positions and has been explained [52,53] due to
linear combination of the atomic orbitals (LCAO) coefficients at the
non-peripheral positions of the highest occupied molecular orbital
(HOMO) being greater than those at the peripheral positions. As a
result, the HOMO level is more destabilized upon non-peripherally
substitution than peripherally substitution. Essentially, the energy
gap (ꢁE) between the HOMO and lowest unoccupied molec-
ular orbital (LUMO) becomes smaller, resulting in a ∼20 nm
bathochromic shift. The B-bands were broad due to the superim-
position of the B1 and B2 bands in the 300–350 nm regions. The
shoulder between 400 and 420 nm may be due to charge transfer
from the electron-rich ring to the electron-poor metal (Fig. 3).
Aggregation is usually depicted as a coplanar association of rings
progressing from monomer to dimer and higher order complexes.
It is dependent on the concentration, nature of the solvent, periph-
eral substituents, center metal ions and temperature [54,55]. In the
aggregated state the electronic structure of the complexed phthalo-
cyanine rings is perturbed resulting in alternation of the ground and
excited state electronic structure [56].
The aggregation behaviour of the coumarin substituted phthalo-
cyanine complexes (np-ZnPc and p-ZnPc) were investigated at
different concentrations in DMSO for complex np-ZnPc and in
DMSO + Triton-X 100 for complex p-ZnPc (Fig. 5 as an example
for complex np-ZnPc in DMSO). In DMSO or DMSO + Triton-X 100
solutions, as the concentration was increased, the intensity of the
Q band absorption also increased and there were no new bands
(normally blue-shifted) due to the aggregated species for complex
np-ZnPc in DMSO and for complex p-ZnPc in DMSO + Triton-X 100
Table 1
Absorption, excitation and emission spectral data for unsubstituted (ZnPc) and non-peripherally tetra-substituted zinc phthalocyanine (np-ZnPc) in DMSO and for periph-
erally tetra-substituted zinc phthalocyanine (p-ZnPc) in DMSO or DMSO + Triton-X 100 (TX).
Compound
Solvent
Q band ꢃmax (nm)
(log ε)
Excitation ꢃEx (nm)
Emission ꢃEm (nm)
Stokes shift ꢄStokes (nm)
ZnPca
np-ZnPc
p-ZnPc
p-ZnPc
DMSO
DMSO
DMSO
DMSO + TX
672
693
678, 639
677
5.14
5.11
4.56, 4.48
4.70
672
693
681
678
682
703
687
687
10
10
9
10
a
Ref: [62].

A.A. Esenpınar et al. / Journal of Photochemistry and Photobiology A: Chemistry 213 (2010) 171–179
175
Fig. 2. Synthesis route of the peripherally tetra-3-[(2-diethylamino)ethyl]-7-oxo-4-methylcoumarin-substituted zinc (II) phthalocyanines complex (p-ZnPc).
solution (Fig. 5 as an example for complex np-ZnPc in DMSO).
Thus, the non-peripherally tetra-substituted phthalocyanine com-
plex (np-ZnPc) did not show aggregation in DMSO at different
concentrations. The peripherally tetra-substituted compound (p-
ZnPc) showed a little aggregation in DMSO + Triton-X 100 solution.
Lambert-Beer low was obeyed for all of these compounds in the
concentrations ranging from 1.4 × 10−5 to 4 × 10−6 M.
3.3. Fluorescence quantum yields and lifetimes
Fig. 6 shows the absorption, fluorescence emission and excita-
tion spectra for the compounds (np-ZnPc and p-ZnPc) in DMSO.
p-ZnPc was aggregated in DMSO, but the fluorescence spectra show
Fig. 4. Absortion spectral changes for peripherally tetra-substituted phthalocyanine
complex (p-ZnPc) observed on addition of Triton-X 100 in DMSO. Concentra-
tion = 1 × 10−5 M.
Fig. 3. Absorption spectrum of tetra-substituted zinc phthalocyanine complexes
(np-ZnPc and p-ZnPc) in DMSO. Concentration = 1 × 10−5 M.

176
A.A. Esenpınar et al. / Journal of Photochemistry and Photobiology A: Chemistry 213 (2010) 171–179
only the monomer species which fluoresced as judged by the nar-
rowing of the fluorescence peak. Fluorescence emission peaks were
observed at 703 nm for np-ZnPc and 687 nm for p-ZnPc in DMSO
(Table 1). The excitation spectrum was similar to absorption spec-
trum and both were mirror images of the fluorescent spectrum for
complex np-ZnPc in DMSO (Fig. 6a). The excitation spectrum was
different from absorption spectrum for complex p-ZnPc in DMSO
due to the aggregation of this complex in DMSO (Fig. 6b). This obser-
vation is typical of aggregated species. Aggregated MPc complexes
are not known [57] to fluoresce since aggregation lowers the pho-
toactivity of molecules through dissipation of energy by aggregates.
The proximity of the wavelength of each component of the Q-band
absorption to the Q band maxima of the excitation spectra for np-
ZnPc suggests that the nuclear configurations of the ground and
excited states were similar and not affected by excitation in DMSO.
The observed Stokes shifts (Table 1) were typical of MPc complexes
in DMSO or DMSO + Triton-X 100 solutions. The fluorescence emis-
sion peak of p-ZnPc is lower than np-ZnPc in DMSO (Fig. 6a and
6b) and the addition of the Triton-X 100 increased the intensity of
the emission peak of p-ZnPc.
Fig. 5. Aggregation behaviour of np-ZnPc in DMSO 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).
The fluorescence quantum yields (˚F) of the studied zinc
phthalocyanine complexes are given in Table 2. The ˚F value of
non-peripherally complex was similar and typical of MPc com-
plexes in DMSO (Table 2). But the ˚F value of the peripherally
complex was lower than MPc complexes due to the aggregation
of this complex in DMSO. The ˚F values of the substituted zinc
phthalocyanine complexes are lower compared to unsubstituted
zinc phthalocyanine complex in DMSO, which implies that the pres-
ence of the coumarin substituents certainly results in fluorescence
quenching. The ˚F value of p-ZnPc was lower than that of np-
ZnPc due to the aggregation. The addition of the Triton-X 100 in
the DMSO solutions of the p-ZnPc increased the ˚F values of this
complex due to the decrease in aggregation in the presence of the
Triton-X 100 (Table 2).
Fluorescence lifetime (ꢀF) refers to the average time a molecule
stays in its excited state before fluorescing, and its value is directly
related to that of ˚F; i.e. the longer lifetime, the higher the quan-
tum yield of fluorescence. Any factor that shortens the fluorescence
lifetime of a fluorophore indirectly reduces the value of ˚F. Such
factors include internal conversion and intersystem crossing.
Fluorescence lifetimes (ꢀF) were calculated using the
Strickler–Berg equation. Using this equation, a good correlation
has been [42] found for the experimentally and theoretically deter-
mined fluorescence lifetimes for the phthalocyanine molecules
as is the case in this work for np-ZnPc in DMSO and p-ZnPc in
both DMSO and DMSO + Triton-X 100 solutions. While ꢀF value of
non-peripherally complex (np-ZnPc) was higher the ꢀF value of
peripherally complex (p-ZnPc) was lower than unsubstituted ZnPc
complex in DMSO because of the aggregation of p-ZnPc complex
in this solvent (Table 2). The addition of Triton-X 100 increased
the ꢀF value of non-peripherally complex (np-ZnPc). The natural
radiative lifetime (ꢀ0) values of tetra-substituted zinc phthalo-
cyanine complexes (np-ZnPc and p-ZnPc) were also longer when
compared to unsubstituted ZnPc in DMSO. The rate constants
for fluorescence (kF) of tetra-substituted zinc phthalocyanine
Fig. 6. Absorption, excitation and emission spectra of the compound np-ZnPc (a)
and p-ZnPc (b) in DMSO. Excitation wavelength = 655 nm.
Table 2
Photophysical and photochemical parameters for unsubstituted (ZnPc) and non-peripherally tetra-substituted zinc phthalocyanine (np-ZnPc) in DMSO and for peripherally
tetra-substituted zinc phthalocyanine (p-ZnPc) in DMSO or DMSO + Triton-X 100 (TX).
a
Compound
Solvent
˚
F
ꢀF (ns)
ꢀ0 (ns)
kF (s−1
)
(×108)
˚
d
(×10−4
)
˚
ꢁ
ZnPcb
np-ZnPc
p-ZnPc
p-ZnPc
DMSO
DMSO
DMSO
DMSO + TX
0.18
0.13
0.03
0.10
1.22
1.39
0.88
2.65
6.80
10.73
29.46
26.53
1.47
0.93
0.34
0.38
2.61
5.70
0.40
4.72
0.67
0.90
0.33
0.55
a
kF is the rate constant for fluorescence. Values calculated using kF = ˚F/ꢀF.
[62].
b

A.A. Esenpınar et al. / Journal of Photochemistry and Photobiology A: Chemistry 213 (2010) 171–179
177
complexes (np-ZnPc and p-ZnPc) were lower when compared to
unsubstituted ZnPc in DMSO. kF value for p-ZnPc was lower than
np-ZnPc in DMSO. The addition of the Triton-X 100 also increased
the kF value of the peripherally substituted complex.
3.4. Singlet oxygen quantum yields
Singlet oxygen quantum yields (˚ꢁ) were determined in DMSO
and DMSO + Triton-X 100 solutions using a chemical method using
DPBF as a quencher. The disappearance of DPBF spectra was
monitored using UV–vis spectrophotometer. Many factors are
responsible for the magnitude of the determined quantum yield
of singlet oxygen including; triplet 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.
It is believed that during photosensitization, the phthalocyanine
molecule is first excited to the singlet state and through intersys-
Fig. 8. The photodegredation of compound np-ZnPc in DMSO showing the disap-
pearance of the Q-band at one minutes intervals (inset: plot of absorbance versus
time).
tem crossing forms the triplet state, and then transfers the energy
ꢀ
to ground state oxygen, O2(3 g), generating excited singlet state
oxygen, O2(1ꢁg), the chief cytotoxic species, which subsequently
oxidizes the substrate by Type II mechanism.
MPc complexes is characterized by a decrease in the Q band and
the formation of weak bands between 500 and 600 nm [58]. Thus,
we propose that during photodegredation, the zinc phthalocya-
nine complexes were partly transformed to an anion (Pc−3) species.
This type of transformation has been observed before during the
photodegredation of phthalocyanine complexes [59].
All the studied zinc phthalocyanine complexes showed about
the same stability with ˚d of the order of 10−4 (Table 2). The ˚d
values, found in this study, are similar to zinc phthalocyanine com-
plexes having different substituents on the phthalocyanine ring in
literature [57,60,61].
Stable zinc phthalocyanine complexes show ˚d values as low as
10−6 and for unstable molecules, values of the order of 10−3 have
been reported [57]. It seems that zinc phthalocyanine complexes in
this study also show similar ˚d values and stability to the known
zinc phthalocyanine complexes.
There was no change in the Q band intensity during the ˚ꢁ
determinations, confirming that complexes were not degraded
during singlet oxygen studies (Fig. 7 as an example for complex
np-ZnPc in DMSO). The ˚ꢁ value of np-ZnPc was higher when
compared to unsubstituted ZnPc in DMSO. The ˚ꢁ value of p-ZnPc
was lower when compared to unsubstituted ZnPc in DMSO and
DMSO + Triton-X 100 solutions due to the aggregation of this com-
plex. np-ZnPc showed highest ˚ꢁ value in DMSO (Table 2). The
addition of the Triton-X 100 reduced the aggregation of p-ZnPc
and increased the ˚ꢁ value of this complex from 0.33 to 0.55.
3.5. Photodegradation studies
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
clean photodegradation not associated with phototransformation
into different forms of MPc absorbing in the visible region.
Fig. 8 shows that for zinc phthalocyanine complexes, there
was a change in spectra following photodegredation. The spec-
tral changes involved a decrease in the Q band and an increase
in the absorption near 570 nm, suggesting that this band is due to
reduction products of the complexes. The first ring reduction in
3.6. Fluorescence quenching studies by 1,4-benzoquinone [BQ]
The fluorescence quenching of zinc phthalocyanine complexes
by 1,4-benzoquinone (BQ) in DMSO and DMSO + Triton-X 100 solu-
tions was found to obey Stern–Volmer kinetics, which is consistent
with diffusion-controlled bimolecular reactions. Fig. 9 shows the
quenching of complex p-ZnPc by BQ in DMSO + Triton-X 100 solu-
tion as an example. The slope of the plots shown in Fig. 10 gave KSV
values, listed in Table 3. The KSV values of the tetra-substituted zinc
Fig. 9. Fluorescence emission spectral changes of p-ZnPc (1.00 × 10−5 M) on addi-
tion of different concentrations of BQ in DMSO + Triton-X 100. [BQ] = 0, 0.008, 0.016,
0.024, 0.032, 0.040 M.
Fig. 7. A typical spectrum for the determination of singlet oxygen quantum yield.
This determination was for compound np-ZnPc in DMSO at a concentration of
1 × 10−5 M (inset: plot of DPBF absorbance versus time).

178
A.A. Esenpınar et al. / Journal of Photochemistry and Photobiology A: Chemistry 213 (2010) 171–179
MPc complexes due to the aggregation of this complex in DMSO.
The aggregation decreased the fluorescence quantum yield and life-
time values of the compound p-ZnPc and addition of the Triton-X
100 increased these values. The coumarin substituted compounds
(np-ZnPc and p-ZnPc) have good singlet oxygen quantum yields
(˚ꢁ), especially compound np-ZnPc result in the highest value.
Aggregation decreased the ˚ꢁ value for p-ZnPc. The addition of
the Triton-X 100 reduced the aggregation of the compound p-ZnPc
and increased the ˚ꢁ value of this compound. The value of ˚ꢁ
ranged from 0.33 to 0.90 gives an indication of the potential of
the compounds as photosensitizers in applications where singlet
oxygen is required (Type II mechanism). The coumarin substituted
compounds showed lower Ksv and kq values when compared to the
unsubstituted ZnPc in DMSO and DMSO + Triton-X 100 solutions.
The tetra-substituted zinc phthalocyanine compounds in this study
show similar ˚d values and stabilities to the zinc phthalocyanine
compounds applicable in PDT.
Fig. 10. Stern–Volmer plots for 1,4-benzoquinone (BQ) quenching of np-ZnPc
in DMSO and p-ZnPc in DMSO and DMSO + Triton-X 100. [MPc] ∼1.00 × 10−5 M.
[BQ] = 0, 0.008, 0.016, 0.024, 0.032, 0.040 M.
Acknowledgement
Table 3
We are thankful to the Research Foundation of Marmara
University, Commission of Scientific Research Project (BAPKO)
[FEN-A-090909-0302].
Fluorescence quenching data for unsubstituted (ZnPc) and non-peripherally
tetra-substituted zinc phthalocyanine (np-ZnPc) in DMSO and for peripherally
tetra-substituted zinc phthalocyanine (p-ZnPc) in DMSO or DMSO + Triton-X 100
(TX).
References
Compound
Solvent
KSV (M−1
)
kq/1010 (dm3 mol−1 s−1
)
ZnPca
np-ZnPc
p-ZnPc
p-ZnPc
DMSO
DMSO
DMSO
DMSO + TX
31.90
15.95
20.83
24.00
2.61
1.15
2.36
0.90
[1] C.C. Leznoff, A.B.P. Lever, Phthalocyanines: Properties and Applications, vol.
1–4, VCH Publishers, New York, 1989–1996.
[2] K. Kadish, K.M. Smith, R. Guilard (Eds.), The Porphyrin Handbook, vol. 15–20,
Academic Press, Boston, 2003.
[3] N.B. McKeown, Phthalocyanine Materials Synthesis, Structure and Function,
Cambridge University Press, 1998.
a
Ref: [62].
[4] P. Erk, H. Hengelsberg, Phthalocyanine dyes and pigments, in: K. Kadish, K.M.
Smith, R. Guilard (Eds.), The Porphyrin Handbook, vol. 19, Academic Press,
Boston, 2003, pp. 105–150.
phthalocyanine complexes (np-ZnPc and p-ZnPc) were lower than
unsubstituted ZnPc. When compared, the substituted complexes,
p-ZnPc showed higher KSV value than np-ZnPc in DMSO which
can be due to the steric effect of the non-peripheral complex. The
addition of Triton-X 100 to DMSO solution of p-ZnPc increased the
KSV value of this complex. The substitution with coumarin group
seems to decrease the KSV values of the complexes in DMSO. The
bimolecular quenching constant (kq) values of the substituted zinc
phthalocyanine complexes (np-ZnPc and ZnPc) were also lower
than for unsubstituted ZnPc, thus substitution with coumarin group
seems to decrease the kq values of the complexes. The kq value of
np-ZnPc was also lower than p-ZnPc in DMSO.
[5] G. de la Torre, C.G. Claessens, T. Torres, Phthalocyanines: old dyes, new mate-
rials. Putting color in nanotechnology, Chem. Commun. (2007) 2000–2015.
[6] J.W. Perry, K. Mansour, I.Y.S. Lee, X.L. Wu, P.V. Bedworth, C.T. Chen, D. Ng, S.R.
Marder, P. Miles, T. Wada, M. Tian, H. Sasabe, Organic optical limiter with a
strong nonlinear absorptive response, Science 273 (1996) 1533–1536.
[7] M. Hanack, T. Schneider, M. Barthel, J.S. Shirk, S.R. Flom, R.G.S. Pong, Indium
phthalocyanines and naphthalocyanines for optical limiting, Coord. Chem. Rev.
235 (2001) 219–221.
[8] Y. Chen, M. Hanack, Y. Araki, O. Ito, Axially modified gallium phthalocyanines
and naphthalocyanines for optical limiting, Chem. Soc. Rev. 34 (2005) 517–529.
[9] J. Simon, P. Bassoul, Design of Molecular Materials, Supramolecular Engineer-
ing, John Wiley Sons Ltd., West Sussex, 2000.
[10] S.R. Flom, Nonlinear optical properties of phthalocyanines, in: K. Kadish, K.M.
Smith, R. Guilard (Eds.), The Porphyrin Handbook, vol. 19, Academic Press,
Boston, 2003, pp. 179–189.
[11] N.B. McKeown, Out of the Blue, Chem. Ind. (1999) 92–98.
[12] M. Durmus¸ , S. Yes¸ ilot, V. Ahsen, Separation and mesogenic properties of
tetraalkoxy-substituted phthalocyanine isomers, New J. Chem. 30 (2006)
675–678.
[13] G. Guillaud, J. Simon, J.P. Germain, Metallophthalocyanines gas sensors, resis-
tors and field effect transistors, Coord, Chem. Rev. 180 (1998) 1433–1484.
[14] M. Bouvet, Radical phthalocyanines and intrinsic semiconduction, in: K. Kadish,
K.M. Smith, R. Guilard (Eds.), The Porphyrin Handbook, vol. 19, Academic Press,
Boston, 2003, pp. 37–104.
[15] M.A. Loi, H. Neugebauer, P. Denk, C.J. Brabec, N.S. Sariciftci, A. Gouloumis, P.
Vázquez, T. Torres, Long-lived photoinduced charge separation for solar cell
applications in phthalocyanine-fulleropyrrolidine dyad thin films, J. Mater.
Chem. 13 (2003) 700–704.
[16] D.M. Guldi, A. Gouloumis, P. Vázquez, T. Torres, Charge-transfer states in
strongly coupled phthalocyanine fullerene ensembles, Chem. Commun. (2002)
2056–2058.
[17] H. Ali, J.E. van Lier, Metal complexes as photo- and radiosensitizers, Chem. Rev.
99 (1999) 2379–2450.
[18] D. Phillips, The photochemistry of sensitisers for photodynamic therapy, Pure
Appl. Chem. 67 (1995) 117–126.
[19] R. Bonnett, Photosensitizers of the porphyrin and phthalocyanine series for
photodynamic therapy, Chem. Soc. Rev. 24 (1995) 19–33.
[20] A.C. Tedesco, J.C.G. Rotta, C.N. Lunardi, Synthesis, photophysical and photo-
chemical aspects of phthalocyanines for photodynamic therapy, Curr. Org.
Chem. 7 (2003) 187–196.
4. Conclusion
In the presented work, the syntheses of new non-peripherally
tetra-3-[(2-diethylamino)ethyl]-7-oxo-4-methylcoumarin substi-
tuted Zn(II) phthalocyanine (np-ZnPc) was described and char-
acterized by standard methods (elemental analysis, 1H NMR,
MALDI-TOF, IR and UV–vis and fluorescence spectral data).
The photophysical and photochemical properties of the non-
peripherally and peripherally tetra-substituted Zn(II) phthalocya-
nines (np-ZnPc and p-ZnPc) were also described for comparison.
All the peripherally and non-peripherally ZnPc compounds are
soluble in DMF and DMSO. In solution, the absorption spectrum
showed monomeric behaviour evidenced by a single (narrow) Q
band, typical of metallated phthalocyanine complex for np-ZnPc
in DMSO. The peripherally tetra-substituted compound (p-ZnPc)
showed broad band around 640 nm due to the aggregation in
DMSO. The coumarin groups as substituents on the phthalocya-
nine ring increased the wavelength of the Q band. Although, the
fluorescence quantum yield of non-peripherally tetra-substituted
compound (np-ZnPc) was typical for MPcs, the fluorescence quan-
tum yield of the peripherally substituted complex was lower than
[21] T. Komatsu, K. Ohta, T. Fujimoto, I. Yamamoto, Liquid crystalline behaviour and
electrochromism in bis(octakis-n-alkylphthalocyaninato)-lutetium(III) com-
plexes, J. Mater. Chem. 4 (1994) 533–536.

A.A. Esenpınar et al. / Journal of Photochemistry and Photobiology A: Chemistry 213 (2010) 171–179
179
[22] S. Abdurrahmanog˘lu, A.R. Özkaya, M. Bulut, Ö. Bekarog˘lu, Synthesis, charac-
terization, and electrochemical and electrochromic properties of sandwich
dilutetium tetraphthalocyanine, Dalton Trans. (2004) 4022–4029.
[23] I. Okura, Photosensitization of Porphyrins and Phthalocyanines, Gordon and
Breach Science Publishers, Amsterdam, 2000.
[24] K.P.C.R. Dennis, Dendritic phthalocyanines: synthesis, photophysical proper-
ties, and aggregation behavior, Chimie 6 (2003) 903–910.
[25] I. Rosental, Phthalocyanines as photodynamic sensitizers, Photochem. Photo-
biol. 53 (1991) 859–870.
[43] A. Ogunsipe, J.-Y. Chen, T. Nyokong, Photophysical and photochemical studies
of zinc(II) phthalocyanine derivatives-effects of substituents and solvents, New
J. Chem. 28 (2004) 822–827.
[44] H. Du, R.A. Fuh, J. Li, A. Corkan, J.S. Lindsey, PhotochemCAD: a computer-aided
design and research tool in photochemistry, Photochem. Photobiol. 68 (1998)
141–142.
[45] J.H. Brannon, D. Madge, Picosecond laser photophysics. Group 3A phthalocya-
nines, J. Am. Chem. Soc. 102 (1980) 62–65.
[46] A. Ogunsipe, T. Nyokong, Photophysical and photochemical studies of
sulphonated non-transition metal phthalocyanines in aqueous and non-
aqueous media, J. Photochem. Photobiol. A: Chem. 173 (2005) 211–220.
[47] I. Seotsanyana-Mokhosi, N. Kuznetsova, T. Nyokong, Photochemical studies of
tetra-2,3-pyridinoporphyrazines, J. Photochem. Photobiol. A: Chem. 140 (2001)
215–222.
[48] N. Kuznetsova, N. Gretsova, E. Kalmkova, E. Makarova, S. Dashkevich, V. Neg-
rimovskii, O. Kaliya, E. Luk’yanets, Relationship between the photochemical
properties and structure of pophyrins and related compounds, Russ. J. Gen.
Chem. 70 (2000) 133–140.
[49] W. Spiller, H. Kliesch, D. Wöhrle, S. Hackbarth, B. Roder, G. Schnurpfeil, Sin-
glet oxygen quantum yields of different photosensitizers in polar solvents and
micellar solutions, J. Porphyrins Phthalocyanines 2 (1998) 145–158.
[50] J. Rose, Advanced Physico-chemical Experiments, Sir Isaac Pitman & Sons Ltd.,
London, 1964.
[51] M.J. Stillman, T. Nyokong, in: C.C. Leznoff, A.B.P. Lever (Eds.), Phthalocyanines:
Properties and Applications, vol. 1, VCH Publishers, New York, 1989 (chapter
3).
[26] A. Kotali, I.S. Lafazanis, P.A. Haris,
A novel and facile synthesis of 7,8-
diacylcoumarins, Tetrahedron Lett. 48 (2007) 7181–7183.
[27] R.D.H. Murray, J. Mendez, S.A. Brown, The Natural Coumarins: Occurrence,
Chemistry and Biochemistry, Wiley & Sons, New York, 1982.
[28] J.H. Fentem, J.R. Fry, Species differences in the metabolism and hepatotoxicity
of coumarin, Comp. Biochem. Physiol. 104C (1) (1993) 1–8.
[29] D. Bogdal, Coumarins: fast synthesis by knoevenagel condensation under
microwave irradiation, J. Chem. Res. (S) (1998) 468–469.
[30] M.C. Laufer, H. Hausmann, W.F. Hölderich, Synthesis of 7-hydroxycoumarins
by Pechmann reaction using Nafion resin/silica nanocomposites as catalysts, J.
Catal. 218 (2003) 315–320.
[31] D.S. Bose, A.P. Rudradas, M.H. Babu, The indium(III) chloride-catalyzed von
Pechmann reaction: a simple and effective procedure for the synthesis of 4-
substituted coumarins, Tetrahedron Lett. 43 (2002) 9195–9197.
[32] G.P. Romanelli, D. Bennardi, D.M. Ruiz, G. Baronetti, H.J. Thomas, J.C. Autino, A
solvent-free synthesis of coumarins using a Wells–Dawson heteropolyacid as
catalyst, Tetrahedron Lett. 45 (2004) 8935–8939.
[33] F.F. Ye, J.R. Gao, W.J. Sheng, J.H. Jia, One-pot synthesis of coumarin derivatives,
Dyes Pigments 77 (2008) 556–558.
[34] N. Mala, J. Ruchi, E. George, S. Xueqing, K. Ashok, Triorganotin(IV)
derivatives of umbelliferone (7-hydroxycoumarin) and their adducts with 1,10-
phenanthroline: synthesis, structural and biological studies, J. Organomet.
Chem. 690 (2005) 134–144.
[35] N. Mala, J. Ruchi, E. George, S. Xueqing, K. Ashok, New diorganotin(IV)
derivatives of 7-hydroxycoumarin (umbelliferone) and their adducts with 1,10-
phenanthroline, Spectrochim. Acta Part A 61 (2005) 3155–3161.
[36] D. Yu, M. Suzuki, L. Xie, S.L. Morris-Natschke, K.H. Lee, Recent progress in the
development of coumarin derivatives as potent anti-HIV agents, Med. Res. Rev.
23 (2003) 322–345.
[37] P.T. Kaye, M.A. Musa, A.T. Nichinda, X.W. Nocanda, Novel Heterocyclic Ana-
logues of the HIV-1 Protease Inhibitor, Ritonavir, Synthetic Commun. 34 (2004)
2575–2589.
[52] A.B. Anderson, T.L. Gorden, M.E. Kenney, Electronic and redox properties of
stacked-ring silicon pthalocyanines from molecular orbital theory, J. Am. Chem.
Soc. 107 (1985) 192–195.
[53] M. Konami, M. Hatano, A. Tajiri, Inter-ring overlap integrals in dimer complexes
of phthalocyanines and porphyrins, Chem. Phys. Lett. 166 (1990) 605–608.
[54] J. Simon, P. Bassoul, in: C.C. Leznoff, A.B.P. Lever (Eds.), Phthalocyanines: Prop-
erties and Applications, vol. 2, VCH Publishers, New York, 1993.
[55] D.D. Dominquez, A.W. Snow, J.S. Shirk, R.G.S. Pong, Polyethyleneoxide-capped
phthalocyanines: limiting phthalocyanine aggregation to dimer formation, J.
Porphyrins Phthalocyanines 5 (2001) 582–592.
[56] H.S. Nalwa, J.S. Shirk, in: C.C. Leznoff, A.B.P. Lever (Eds.), Phthalocyanines: Prop-
erties and Applications, vol. 4, VCH Publishers, New York, 1996.
[57] T. Nyokong, Effects of substituents on the photochemical and photophysical
properties of main group metal phthalocyanines, Coord. Chem. Rev. 251 (2007)
1707–1722.
[38] R.D. George, A.W. Snow, Synthesis of 3-nitrophthalonitrile and tetra-
alpha-substituted phthalocyanines, J. Heterocyclic Chem. 32 (1995) 495–
498.
[39] J.G. Young, W. Onyebuagu, Synthesis and characterization of di-disubstituted
phthalocyanines, J. Org. Chem. 55 (1990) 2155–2159.
[58] M.J. Stillman, in: C.C. Leznoff, A.B.P. Lever (Eds.), Phthalocyanines: Properties
and Applications, Vol. 3, VCH Publishers, New York, 1994 (chapter 5).
[59] M. Durmus¸ , T. Nyokong, Synthesis, photophysical and photochemical prop-
erties of aryloxy tetra-substituted gallium and indium phthalocyanine
derivatives, Tetrahedron 63 (2007) 1385–1394.
[40] H. C¸ akıcı, A.A. Esenpınar, M. Bulut, Synthesis and characterization of novel
phthalocyanines bearing quaternizable coumarin, Polyhedron 27 (2008)
3625–3630.
[60] D. Atilla, M. Durmus¸ , A.G. Gürek, V. Ahsen, T. Nyokong, Synthesis, photophysical
and photochemical properties of poly(oxyethylene) substituted zinc phthalo-
cyanines, Dalton Trans. (2007) 1235–1243.
[41] S. Fery-Forgues, D. Lavabre, Are fluorescence quantum yields so tricky to mea-
sure? A demonstration using familiar stationery products, J. Chem. Educ. 76
(1999) 1260–1264.
[42] D. Maree, T. Nyokong, K. Suhling, D. Phillips, Effects of axial ligands on the
photophysical properties of silicon octaphenoxyphthalocyanine, J. Porphyrins
Phthalocyanines 6 (2002) 373–376.
[61] M. Durmus¸ , Z. Bıyıklıog˘lu, H. Kantekin, Synthesis, photophysical and photo-
chemical properties of crown ether substituted zinc phthalocyanines, Synth.
Met. 159 (2009) 1563–1571.
˙
[62] I. Gürol, M. Durmus¸ , V. Ahsen, T. Nyokong, Synthesis, photophysical and photo-
chemical properties of substituted zinc phthalocyanines, Dalton Trans. (2007)
3782–3791.