Synthesis and characterization of new polyfluorinated dendrimeric phthalocyanines

Article abstract of DOI:10.1016/j.poly.2010.06.023

The synthesis of new polyfluorinated dendrimeric metallophthalocyanines (M = Zn, Ni, Co) bearing 3,5-bis(2′,3′,4′,5′,6′- pentafluorobenzyloxy)benzyloxy moieties (2-4) was achieved by cyclotetramerization of phthalonitrile derivative 1 in the presence of z

Full text of DOI:10.1016/j.poly.2010.06.023

Polyhedron 29 (2010) 2710–2715
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Synthesis and characterization of new polyfluorinated dendrimeric phthalocyanines
_
*
Mukaddes Özçesßmeci, Ibrahim Özçeßsmeci, Esin Hamuryudan
Department of Chemistry, Istanbul Technical University, Maslak TR34469, Istanbul, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
The synthesis of new polyfluorinated dendrimeric metallophthalocyanines (M = Zn, Ni, Co) bearing 3,5-
bis(20,30,40,50,60-pentafluorobenzyloxy)benzyloxy moieties (2–4) was achieved by cyclotetramerization
of phthalonitrile derivative 1 in the presence of zinc, nickel or cobalt salts in DMF. All the target phthal-
ocyanines were separated by column chromatography and their spectroscopic, fluorescence and energy
transfer properties, and aggregation behavior were investigated in different solvents and at different con-
centrations in chloroform. The compounds were characterized by Fourier transform-infrared, fluorine,
proton and carbon nuclear magnetic resonance, mass, ultraviolet–visible and fluorescence spectral data.
The phthalocyanines (2–4) were extremely soluble in various organic solvents, such as tetrahydrofuran,
acetone and dichloromethane.
Received 29 April 2010
Accepted 23 June 2010
Available online 1 July 2010
Keywords:
Fluorinated
Phthalocyanines
Benzyloxy groups
Aggregation
Ó 2010 Elsevier Ltd. All rights reserved.
Energy transfer
1. Introduction
Fluorinated metal phthalocyanines and porphyrins currently
receive a great deal of attention due to their interesting electron-
Phthalocyanines (Pcs) have a two-dimensional 18
p
-electron
transfer, photosensitizing properties, along with magnetic and
thermal characteristics [21–24]. The presence of pentafluorophe-
nyl groups on the macrocycle ring can increase the catalytic
activity and stability [25]. Fluoro-substituted phthalocyanines are
known for their high solubility, even in polar, aprotic solvents.
The increased solubility may be due to fluorine, which has the
highest electronegativity of all elements [26].
In our previous studies, we have reported the synthesis, electro-
chemical and spectroelectrochemical properties of symmetric and
asymmetric phthalocyanines [27–33]. In this step, our aim has
been to design new molecules with dendritic fluoro-substituents,
enhancing their solubility in common solvents and at the same
time prohibiting their aggregation. We report herein the synthesis,
characterization, fluorescence and energy transfer properties of
new readily soluble metal phthalocyanines with up to 40 fluo-
rine-containing substituents on the periphery for the first time,
and we also report on the effects of the substituents on the
spectroscopic and aggregation properties of the phthalocyanine
derivatives in different solvents and at different concentrations in
chloroform.
conjugated system thereby allowing the incorporation of more
than 70 different metal or non-metal ions into their inner core.
Modifications in the macrocycle can be made either by introduc-
tion of different central ions or by substitution of functional groups
at the peripheral sites of the ring. During recent decades, metal
phthalocyanines have found widespread application not only as
pigments and dyes but also as chemical sensors, liquid crystals,
Langmuir–Blodgett films, catalysts, non-linear optical materials,
optical data storage materials, carrier generation materials in
near-IR and also in medicine [1–5]. For such applications, good
solubility is preferred. A critical disadvantage of unsubstituted
Pcs is their low solubility in organic solvents or water. By
appropriate substitution with bulky or long-chain groups in the
peripheral positions of the macrocycle, these compounds can be
solubilized in common organic solvents, thus increasing the field
of possible applications [6–14].
Redox-active d-metal (e.g. Fe, Mn, Co) phthalocyanines exhibit
very high catalytic activity in the oxidation of thiols, hydrocarbons,
hydroquinones, arenes and amines [15–18]. The most promising
way to increase the first oxidation potential of phthalocyanine
complexes is the introduction of electron-withdrawing substitu-
ents. It has been shown that halogenated metallo tetrapyrrole
derivatives are very efficient catalysts for oxidation reactions
under very mild conditions [19,20].
2. Experimental
The IR spectra were recorded on a Perkin–Elmer Spectrum
One-IR spectrometer and the electronic spectra were recorded
on
a
Scinco Neosys-2000 double-beam ultraviolet–visible
(UV–Vis) spectrophotometer. Fluorescence excitation and emission
spectra were recorded on a Varian Cary eclipse fluorescence
* Corresponding author. Tel.: +90 2122856826; fax: +90 2122856386.
E-mail address: esin@itu.edu.tr (E. Hamuryudan).
0277-5387/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2010.06.023

M. Özçeßsmeci et al. / Polyhedron 29 (2010) 2710–2715
2711
spectrofluorimeter. Elemental analyses were performed by the
Instrumental Analysis Laboratory of the TÜBITAK Marmara
on silica gel using hexane/chloroform (100:1) to give phthalonitrile
derivative (1) (Scheme 1). Yield: 0.977 g (54%). Elemental analysis,
Anal. Calc. for C29H12F10N2O3: C, 55.60; H, 1.93; N, 4.47. Found:
_
Research Centre. 1H NMR spectra were recorded on a Bruker
250 MHz spectrometer using TMS as an internal reference. 19F
NMR and 13C NMR spectra were recorded on a Varian Unity Inova
500 MHz NMR. Mass spectra were performed on Varian 711 and
Bruker microflex LT MALDI-TOF MS mass spectrometers. All the
reagents and solvents were of reagent grade quality obtained from
commercial suppliers. All the solvents were dried and purified
according to Ref. [34]. The homogeneity of the products was tested
in each step by TLC (SiO2). 4-Nitrophthalonitrile and 3,5-bis(penta-
fluorobenzyloxy)benzyl alcohol were synthesized according to
published methods [35,36].
C, 55.83; H, 2.05; N, 4.62%. IR m
max/cmꢀ1: 2964–2855 (alkyl CH),
2227 (C„N), 1255 (C–O–C). 1H NMR (CDCl3), (d, ppm): 7.73 (d, H,
Ar-H), 7.26 (d, H, Ar-H), 7.22 (s, H, Ar-H), 6.65 (s, 2H, Ar-H), 6.56
(s, H, Ar-H), 5.11 (s, 6H, CH2). 19F NMR (CDCl3), (d, ppm): ꢀ144.8
(d(d), 4F, o-fluorine), ꢀ154.6 (t, 2F, p-fluorine), ꢀ163.8 (m, 4F,
m-fluorine). 13C NMR (CDCl3), (d, ppm): 161.69 (aromatic C–O),
159.84 (aromatic C–O), 147.03 (aromatic C–F), 146.03 (aromatic
C), 145.02 (aromatic C–F), 137.79 (aromatic C–F), 135.51 (aromatic
C–H), 120.15 (aromatic C–H), 119.89 (aromatic C–H), 117.86
(aromatic C), 115.69 (C„N), 115.34 (C„N), 109.92 (aromatic C–H),
108.20 (aromatic C), 107.17 (aromatic C–H), 102.39 (aromatic C–H),
70.75 (OCH2), 57.88 (OCH2). MS (ESI+), (m/z): 626.50 [M]+.
2.1. 4-[3,5-Bis(20,30,40,50,60-pentafluorobenzyloxy)-
benzyloxy]phthalonitrile (1)
2.2. {2,9(10),16(17),23(24)-Tetrakis-[3,5-bis(20,30,40,50,60-pentafluoro-
3,5-Bis(20,30,40,50,60-pentafluorobenzyloxy)benzyl alcohol (1.446 g,
2.890 mmol) and 4-nitrophthalonitrile (0.500 g, 2.890 mmol) were
dissolved in 15 mL of dry DMF. Anhydrous K2CO3 (0.800 g, 5.780
mmol) was added portion wise for over 2 h and the mixture was
stirred vigorously at room temperature under N2 for 24 h. Then
the solution was poured into ice-water (200 mL). The residue that
formed was filtered off, washed with water several times until
the filtrate was neutral, and then with cold methanol, and dried
in vacuo. A pale beige product was purified by chromatography
benzyloxy)benzyloxy]phthalocyaninato}metal derivatives (2–4)
A
mixture of compound 1 (0.300 g, 0.480 mmol)) and
0.125 mmol anhydrous metal salt (zinc acetate 0.023 g, cobalt
chloride 0.0163 g or nickel chloride 0.0163 g) and dry DMF
(1.5 mL) was placed under nitrogen atmosphere in a standard
sealed tube. The reaction mixture was heated and stirred at
150 °C under N2 for 48 h. After cooling to room temperature, the
green mixture that formed was poured into ice-water (100 mL).
Scheme 1. The synthesis of phthalonitrile derivative 1 and phthalocyanine complexes 2–4.

2712
M. Özçeßsmeci et al. / Polyhedron 29 (2010) 2710–2715
The crude product was precipitated and filtered off, washed with
hot water and then with cold methanol, and dried in vacuo. Finally,
purification of the product was accomplished by column chroma-
tography on silica gel, first with chloroform/ethyl acetate (1:4)
and then with acetone/toluene (1:2) as the eluent.
eluent. As expected for monosubstituted phthalonitriles, the Pcs
2–4 are a mixture of four structural isomers and our attempts to
isolate each of them have been unsuccessful [37]. All the new com-
pounds were identified through various spectroscopic techniques,
such as 1H NMR, 13C NMR, 19F NMR, FT-IR, UV–Vis, ESI-MS and
elemental analysis. Spectroscopic data of the compounds 1–4 are
in full agreement with the proposed structures.
2.2.1. Compound 2
IR spectrum of 1 indicated C„N groups by the presence of an
intense band at 2227 cmꢀ1, and also benzylic groups at 2964–
2855 cmꢀ1 and etheric (C–O–C) units at 1255 cmꢀ1. Phthalocya-
nines 2–4 also have very similar IR absorptions for the peripheral
substituents; the clear difference is the disappearance of the sharp
C„N band at 2227 cmꢀ1, which signifies the cyclotetramerization
of the dinitrile.
Yield: 0.086 g (28%). M.p. >200 °C. Elemental analysis, Anal.
Calc. for C116H48F40N8O12Zn: C, 54.19; H, 1.88; N, 4.36. Found: C,
54.31; H, 1.92; N, 4.48%. IR
m
max/cmꢀ1: 2925–2854 (alkyl CH),
1287 (C–O–C). 1H NMR (CDCl3), (d, ppm): 7.74 (m, 4H, Ar-H),
7.50 (d, 4H, Ar-H), 7.35 (s, 4H, Ar-H), 6.67 (s, 8H, Ar-H), 6.56 (s,
4H, Ar-H), 5.10 (d, 24H, CH2). 19F NMR (CDCl3), (d, ppm): ꢀ142.6
(d(d), 16F, o-fluorine), ꢀ152.4 (t, 8F, p-fluorine), ꢀ161.8 (m, 16F,
In the 1H NMR spectrum of 1, the aromatic protons appear at d
7.73, 7.26, 7.22, 6.65 and 6.56 ppm as a doublet, doublet, singlet,
singlet and singlet, respectively. Also the CH2 protons of the penta-
fluorobenzyl and benzyl moieties were observed at 5.11 ppm. The
1H NMR spectra of 2 and 3 were almost identical to those of the
m-fluorine). UV–Vis (CHCl3): kmax/nm (log
(4.99). MS (MALDI TOF) m/z: 2571.48 [M]+.
e): 343 (5.00), 678
2.2.2. Compound 3
Yield: 0.070 g (23%). M.p. >200 °C. Elemental analysis, Anal. Calc.
starting compound
broadening.
1 except for small shifts and a slight
for C116H48F40N8O12Ni: C, 54.33; H, 1.89; N, 4.37. Found: C, 54.47;
H, 1.95; N, 4.21%. IR m
max/cmꢀ1: 2924–2854 (alkyl CH), 1287 (C–O–
The 13C NMR spectrum of 1 showed aromatic carbon atoms at d
161.69–102.39 ppm and aliphatic carbon atoms appeared at d 70.75
and 57.88 ppm. Also the nitrile carbons were observed at d 115.69
and 115.34 ppm. The 13C NMR spectrum of the NiPc (3) was fully
consistent with the proposed structure.
C). 1H NMR (CDCl3), (d, ppm): 7.73 (m, 4H, Ar-H), 7.54 (m, 4H,
Ar-H), 7.35 (s, 4H, Ar-H), 6.83 (s, 8H, Ar-H), 6.51 (s, 4H, Ar-H), 5.05
(s, 24H, CH2). 13C NMR (CDCl3), (d, ppm): 170.73 (aromatic C), 158.63
(aromatic C–O), 158.32 (aromatic C–O), 155.16 (aromatic C–O),
145.72 (aromatic C–F), 143.72 (aromatic C), 141.64 (aromatic
C–F), 141.64 (aromatic C–F), 137.55 (aromatic C–F), 135.55 (aromatic
C–H), 131.21 (aromatic C–H), 129.84 (aromatic C–H), 127.80
(aromatic C), 116.68 (aromatic C–H), 109.01 (aromatic C), 105.76
(aromatic C–H), 100.53 (aromatic C–H), 70.10 (OCH2), 56.47
The 19F NMR spectra are much simpler to interpret as they usu-
ally contain only a limited number of signals. Therefore, 19F NMR
spectroscopy could become a simple and efficient way to identify
fluorine atoms of phenyl substituents. The 19F NMR spectra of 1
(Fig. 1) and 2 showed the expected signals of the five fluorine
atoms attached to the aromatic ring. Integration of the peaks gave
a 2:1:2 ratio as expected. These compounds displayed signals due
to F2,6 (o-fluorine), F4 (p-fluorine) and F3,5 (m-fluorine) at d ꢀ144.8,
ꢀ154.6 and ꢀ163.8 ppm for compound 1 and ꢀ142.6, ꢀ152.4 and
ꢀ161.8 ppm for compound 2, respectively. The F4 signals appeared
as a triplet due to F3,5 coupling, the F2,6 signals appeared as a dou-
blet of doublets and the F3,5 signals as a multiplet in both
compounds.
In addition to these supportive results for the structures, the
mass spectra of compounds 1–3 gave the characteristic molecular
ion peaks at m/z: 626.50 [M]+, 2571.48 [M]+, 2564.78 [M]+ and 4
gave a monoprotonated molecular ion peak at m/z: 2565.85
[M+H]+, confirming the proposed structures.
The UV–Vis spectra of the phthalocyanine complexes (2–4)
exhibited characteristic absorptions in the Q-band region at
around 678, 668 and 669 nm for MPcs (2–4) in chloroform, attrib-
(OCH2). UV–Vis (CHCl3): kmax/nm (log
e): 323 (5.06), 668 (5.07). MS
(ESI+), (m/z): 2564.78 [M]+.
2.2.3. Compound 4
Yield: 0.104 g (34%). M.p. >200 °C. Elemental analysis, Anal.
Calc. for C116H48F40N8O12Co: C, 54.33; H, 1.87; N, 4.37. Found: C,
54.52; H, 1.97; N, 4.49%. IR:
m
max/cmꢀ1: 2925–2854 (alkyl CH),
1284 (C–O–C). UV–Vis (CHCl3): kmax/nm (log
e): 317 (5.04), 669
(4.94). MS (ESI+), (m/z): 2565.85 [M+H]+.
3. Results and discussion
Zinc(II), nickel(II) and cobalt(II) phthalocyanines carrying four
branched groups at peripheral positions were prepared according
to the route shown in Scheme 1. The first step in the synthetic pro-
cedure was to obtain the phthalonitrile derivative (1) containing
3,5-bis(20,30,40,50,60-pentafluorobenzyloxy)benzyloxy groups. This
was accomplished by a base-catalyzed nucleophilic aromatic nitro
displacement of 4-nitrophthalonitrile [34] with 3,5-bis(20,30,40,
50,60-pentafluorobenzyloxy)benzyl alcohol [35]. This reaction has
been used effectively in the preparation of a variety of ether- or
thioether-substituted phthalonitriles. The nucleophilic substitu-
tion of 3,5-bis(20,30,40,50,60-pentafluorobenzyloxy) benzyl alcohol
with 4-nitrophthalonitrile in N,N-dimethylformamide using potas-
sium carbonate as the base at room temperature for 24 h under N2
atmosphere gave compound 1 in about 54% yield. The product was
purified by column chromatography.
The substituted phthalonitrile derivative 1 was used to prepare
zinc(II), nickel(II) and cobalt(II) phthalocyanine complexes (2–4)
by its reaction with zinc(II) acetate, nickel(II) chloride or cobalt(II)
chloride in DMF at 140 °C in a sealed tube. The green products
were extremely soluble in various solvents, such as chloroform,
dichloromethane, tetrahydrofuran, and acetone, and they were
purified by column chromatography on silica gel, first with chloro-
form/ethyl acetate (1:4) and then with acetone/toluene (1:2) as the
uted to the
p–p* transition from the HOMO (highest occupied
molecular orbital) to the LUMO (lowest unoccupied molecular
orbital) of the Pcꢀ2 ring, and in the B band region (UV region) at
around 317–343 nm in chloroform, arising from the deeper
transitions (Fig. 2).
p–p*
The aggregation behavior of phthalocyanines in solution, which
can be followed effectively by absorption studies, is a good indica-
tion of the interactions between the aromatic macrocycles of the
phthalocyanines. Aggregation, which is usually depicted as a copla-
nar association, is dependent on the concentration, nature of the
solvent, nature of the substituents, complexed metal ions and tem-
perature [38–40].
In this study, the aggregation behavior of 2 was investigated at
different concentrations in chloroform (Fig. 3). In chloroform, as
the concentration was increased, the intensity of the Q-band
absorption increased in parallel, and there were no new bands
due to the aggregated species [41]. It is seen that the Beer–Lambert
law was obeyed for compound 2 for concentrations ranging from
1 ꢁ 10ꢀ5 to 1 ꢁ 10ꢀ6 mol dmꢀ3 (insert in Fig. 3).

M. Özçeßsmeci et al. / Polyhedron 29 (2010) 2710–2715
2713
Fig. 1. 19F NMR spectrum of compound 1.
Fig. 2. UV spectra of ZnPc (2), NiPc (3) and CoPc (4) (5 ꢁ 10ꢀ6 M in CHCl3).
Fig. 4. UV spectra of ZnPc (2) in different solvents.
Fig. 3. UV spectra of ZnPc (2) in CHCl3 at different concentrations: 1 ꢁ 10ꢀ5 (A),
Fig. 5. Plot of the Q band frequency of ZnPc (2) against (n2 ꢀ 1)/(2n2 + 1), where n is
8 ꢁ 10ꢀ6 (B), 6 ꢁ 10ꢀ6 (C), 4 ꢁ 10ꢀ6 (D), 2 ꢁ 10ꢀ6 (E), and 1 ꢁ 10ꢀ6 (F) mol dmꢀ3
.
the refractive index of the solvent.
The electronic spectra of compound 2 in different organic
solvents, such as acetone, tetrahydrofuran, chloroform, dimethyl
sulfoxide and toluene, were also analyzed (Fig. 4). It is obvious that
the Q band position changes with respect to the solvent. In general,

2714
M. Özçeßsmeci et al. / Polyhedron 29 (2010) 2710–2715
the red shift of the Q band increases with the ascending refractive
index of the solvent. In our study, the red shift of the Q band due
to the solvent for compound 2 increased in the following order:
acetone < tetrahydrofuran < chloroform < dimethyl sulfoxide ꢂ
toluene. The electronic absorption spectra of 2 in these solvents
were analyzed by using the method described originally by Bayliss
[42,43]. Fig. 5 displays a plot of the Q band frequency versus the
function (n2 ꢀ 1)/(2n2 + 1), where n is the refractive index of the
solvent. The positions of the Q bands in these solvents show almost
a linear dependence on this function. This linearity suggests that
the shifts are caused mainly by solvation and not by a ligation
effect [42].
Also, in this study we examined the fluorescence and energy
transfer properties of the zero (6) [28] and first (2) generation of
zinc(II) phthalocyanines (Scheme 2). This avenue, studying excita-
tion energy transfer through dendritic architectures, has been of
much current interest because of its relevance to biological light-
harvesting antennas [44,45]. Excitation and emission spectra of
the phthalocyanine derivatives substituted with fluorinated aryl
dendron groups were obtained in THF solution. Fig. 6 shows the
excitation spectra of the starting phthalonitriles 4-(20,30,40,50,60-
pentafluorobenzyloxy)phthalonitrile (5) [28] and 1, and the related
phthalocyanines tetrakis(20,30,40,50,60-pentafluorobenzyloxy)phtha-
locyaninato zinc(II) (6) (G0) [28] and 2 (G1). It can be seen that as
the number of aryl groups increases, more photons are collected
and transmitted to the phthalocyanine core [46]. As shown in
Fig. 6, the aryl dendrons 1 and 5 exhibit two absorption bands
peaking at 270 and 308 nm and an emission at 340 nm for 5 and
at 410 nm for 1 upon excitation at 310 nm, Fig. 7. As this emission
band overlaps with the B-band of phthalocyanines, energy transfer
Fig. 7. Emission spectra of 4-(20,30,40,50,60-pentafluorobenzyloxy)phthalonitrile (5,
2 ꢁ 10ꢀ5 M), 1 (2 ꢁ 10ꢀ5 M), 2 (n = 1, 5 ꢁ 10ꢀ6 M) and tetrakis(20,30,40,50,60-penta-
fluorobenzyloxy)phthalocyaninato zinc(II) (6, 5 ꢁ 10ꢀ6 M) and tetrakis(acetoxy-
ethylthio)phthalocyaninato zinc(II) (7, 5 ꢁ 10ꢀ6 M) in THF, emission excited at
310 nm.
from the excited fluorinated aryl dendrons to the central phthalo-
cyanine may occur in this series of compounds [47].
This series of dendritic phthalocyanines also exhibit an interest-
ing photoinduced intramolecular energy transfer. Upon excitation
at 310 nm, where the fluorinated aryl dendrons absorb and the
absorption of phthalocyanine is weak, the dendritic phthalocya-
nines compounds emit weakly at about 350 nm for 6 (G0) and at
about 400 nm for 2 (G1) due to the fluorinated aryl dendrons, to-
gether with an emission at 690 nm for tetrakis(20,30,40,50,60-penta-
fluorobenzyloxy)phthalocyaninato zinc(II) (6) (G0) and at 695 nm
for 2 (G1) due to a singlet–singlet energy transfer from the excited
dendrons to the central phthalocyanine core (Fig. 7). The fluores-
cence of the aryl dendron parts was quenched and emission inten-
sities of the phthalocyanine part around 690–695 nm were
increased because of the radiative energy transfer resulting from
the inner filter effect of the Pc core [46,48].
For comparison, the soluble model compound tetrakis(acetoxy-
ethylthio)phthalocyaninato zinc(II) (7), which does not contain
aromatic dendrons or fluorescence groups, was prepared [13]. This
compound exhibited only a very weak emission at 690 nm, which
may arise from the weak absorption at 310 nm (Fig. 7). The latter
emissions of dendritic phthalocyanines are clearly due to
a
singlet–singlet energy transfer from the excited fluorinated aryl
dendrons to the central phthalocyanine core which acts as an
energy trap. The energy transfer efficiency estimated from the
fluorescence quenching is not naturally 100%, probably due to
Scheme 2. The zero (6) and first (2) generation of the zinc(II) phthalocyanines.
Fig. 6. Excitation spectra of 4-(20,30,40,50,60-pentafluorobenzyloxy)phthalonitrile (5,
2 ꢁ 10ꢀ5 M), 1 (2 ꢁ 10ꢀ5 M), 2 (5 ꢁ 10ꢀ6 M) and tetrakis(20,30,40,50,60-pentafluorob-
enzyloxy)phthalocyaninato zinc(II) (6, 5 ꢁ 10ꢀ6 M) in THF, monitored at 720 nm.
Fig. 8. Emission spectra of 2 (5 ꢁ 10ꢀ6 M) and tetrakis(20,30,40,50,60-pentafluorob-
enzyloxy)phthalocyaninato zinc(II) (6, 5 ꢁ 10ꢀ6 M) in THF, emission excited at
610 nm.

M. Özçeßsmeci et al. / Polyhedron 29 (2010) 2710–2715
2715
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À
Á
UF
¼
UFðStdÞ FAStdg2=FStd
A
g2Std
;
ð1Þ
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for photon-harvesting to central phthalocyanine cores. The
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This work was supported by the Research Fund of the Technical
University of Istanbul and TUBITAK (Project Number: 108T448).
_
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