Synthesis, electrochemical, in situ spectroelectrochemical and in situ electrocolorimetric characterization of new metal-free and metallophthalocyanines substituted with 4-{2-[2-(1-naphthyloxy)ethoxy]ethoxy} groups

Article abstract of DOI:10.1016/j.poly.2010.01.032

The synthesis of novel metal-free and metallophthalocyanines [Ni(II), Zn(II), Co(II), Cu(II)] were prepared by cyclotetramerization of a novel 4-{2-[2-(1-naphthyloxy)ethoxy]ethoxy}phthalonitrile and the corresponding metal salts (NiCl₂, Zn(CH

Full text of DOI:10.1016/j.poly.2010.01.032

Polyhedron 29 (2010) 1475–1484
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Synthesis, electrochemical, in situ spectroelectrochemical
and in situ electrocolorimetric characterization of new metal-free
and metallophthalocyanines substituted
with 4-{2-[2-(1-naphthyloxy)ethoxy]ethoxy} groups
Irfan Acar a, Zekeriya Bıyıklıog˘lu b, Atıf Koca c, Halit Kantekin a,
*
a Department of Chemistry, Faculty of Arts & Sciences, Karadeniz Technical University, 61080 Trabzon, Turkey
b Macka Vocational School, Karadeniz Technical University, 61750 Macka, Trabzon, Turkey
c
_
Department of Chemical Engineering, Faculty of Engineering, Marmara University, Göztepe 34722, 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 novel metal-free and metallophthalocyanines [Ni(II), Zn(II), Co(II), Cu(II)] were prepared
by cyclotetramerization of a novel 4-{2-[2-(1-naphthyloxy)ethoxy]ethoxy}phthalonitrile and the corre-
sponding metal salts (NiCl2, Zn(CH3COO)2, CoCl2 and CuCl2). The structures of the target compounds were
confirmed using elemental analysis, IR, 1H NMR, 13C NMR, UV–Vis and MS spectral data. Voltammetric
and in situ spectroelectrochemical measurements show that while cobalt phthalocyanine complex gives
both metal-based and ring-based redox processes, metal-free, and zinc phthalocyanines show only ring-
based reduction and oxidation processes. All complexes decomposed and coated on the electrode as non-
conductive film at positive potential window of the electrolyte. An in situ electrocolorimetric method has
been applied to investigate color of the electro-generated anionic and cationic forms of the complexes.
Ó 2010 Elsevier Ltd. All rights reserved.
Received 23 December 2009
Accepted 26 January 2010
Available online 1 February 2010
Keywords:
Phthalocyanine
Phthalonitrile
Cyclic voltammetry
Synthesis
Spectroelectrochemistry
Chromaticity diagram
1. Introduction
Condensed multicyclic aromatic compounds (e.g., naphthalene
derivatives) are functional groups effective in photoemission stud-
Phthalocyanine (Pc) and its derivatives have been under sys-
tematic study more than 70 years; however, researchers are still
interested in this class of compounds [1]. Owing to their fascinat-
ing properties, Pc-based materials find applications in nonlinear
optics [2], optical data storage [3], photodynamic cancer therapy
[4], sensors [5], catalysis [6], and solar energy conversion [7].
Due to intermolecular interactions between the macrocycles,
peripherally unsubstituted phthalocyanines are insoluble in com-
mon organic solvents and aqueous media, in this way minimizing
their applications [8]. Adding functional groups on the periphery
ies [14]. As bulky electron rich units, the presence of naphthalenyl
groups on the periphery phthalocyanines is also expected to
change the ordering of molecules in the solid state. However, in
the case of naphthalocyanines, the physical and chemical identity
of naphthalene units is no longer distinct [15].
Microwaves have been previously used for the synthesis of
phthalocyanines and include a wider range of references on the
topic [16–19]. In this paper, we describe the synthesis and charac-
terization of metal-free 4 and metallophthalocyanines 5, 6, 7 and
8 substituted with 4-{2-[2-(1-naphthyloxy)ethoxy]ethoxy} groups
by microwave irradiation. Also, we have investigated the voltam-
metric, in situ spectroelectrochemical and in situ electrocolori-
metric responses of the metallophthalocyanines in solution to
open a way to their possible electrochromic application depending
on the spectroelectrochemical and chromaticity data. It is well
known that many phthalocyanine complexes show excellent elec-
trochromic properties [20,21] both in solution and as films. There-
fore, we report here in situ electrocolorimetric analysis of the
phthalocyanines to determine possible electrochromic application
of the complexes. Because electrocolorimetry technique provides a
more precise way to define color of the electro-generated species
[22].
that increase the distance between the 18-
p electron-conjugated
systems of phthalocyanines enhances the solubility of these com-
pounds [9–11]. The solubility can also be increased by introducing
alkyl or alkoxy groups in the peripheral position of phthalocya-
nines framework [12]. The major advantage of phthalocyanines
over porphyrins is that their Q-bands are at longer wavelengths
and have much higher intensity than the Q-bands of porphyrins.
Some complexes of phthalocyanines show photobiological activity
against tumors [13].
* Corresponding author. Tel.: +90 462 377 2589; fax: +90 462 325 3196.
E-mail address: halit@ktu.edu.tr (H. Kantekin).
0277-5387/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2010.01.032

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I. Acar et al. / Polyhedron 29 (2010) 1475–1484
points were measured on an electrothermal apparatus and are
uncorrected.
2. Experimental
2.1. Materials
The electrochemical and spectroelectrochemical measurements
were carried out with Gamry Reference 600 potentiostat/galvano-
stat controlled by an external PC and utilizing a three-electrode
configuration at 25 °C. For CV, and SWV measurements, the work-
ing electrode was a Pt disc with a surface area of 0.071 cm2. The
surface of the working electrode was polished with a diamond sus-
pension before each run. A Pt wire served as the counter electrode.
Saturated calomel electrode (SCE) was employed as the reference
electrode and separated from the bulk of the solution by a double
bridge. Ferrocene was used as an internal reference. TBAP in DCM
was employed as the supporting electrolyte at a concentration of
0.10 mol dmꢀ3. High purity N2 was used to remove dissolved O2
at least 15 min prior to each run and to maintain a nitrogen blanket
during the measurements. IR compensation was applied to the CV
and SWV scans to minimize the potential control error. UV/Vis
absorption spectra and chromaticity diagrams were measured by
an OceanOptics QE65000 diode array spectrophotometer. In situ
2-[2-(1-Naphthyloxy)ethoxy]ethanol (1) [23] and 4-nitropht-
halonitrile (2) [24] were prepared according to the literature. All
reagents and solvents were of reagent grade quality and were ob-
tained from commercial suppliers. All solvents were dried and
purified as described by Perrin and Armarego [25].
2.2. Equipment
The IR spectra were recorded on a Perkin–Elmer 1600 FT-IR
Spectrophotometer, using KBr pellets. 1H and 13C NMR spectra
were recorded on a Varian Mercury 200 MHz spectrometer in
CDCl3, and chemical shifts were reported (d) relative to Me4Si as
internal standard. Mass spectra were measured on a Micromass
Quatro LC/ULTIMA LC–MS/MS spectrometer. The elemental analy-
ses were performed on a Costech ECS 4010 instrument. Melting
CN
OH
O
NO2
CN
O
2
1
dry KCO
dry DMF
2
3
CN
CN
O
O
O
3
DBU
n-pentanol
160 oC
O
O
O
O
O
O
N
HN
N
N
N
N
NH
N
O
O
O
O
4
O
O
Fig. 1. The synthesis of the metal-free phthalocyanine.

I. Acar et al. / Polyhedron 29 (2010) 1475–1484
1477
spectroelectrochemical measurements were carried out by utiliz-
ing a three-electrode configuration of thin-layer quartz spectro-
electrochemical cell at 25 °C. The working electrode was Pt tulle.
Pt wire counter electrode separated by a glass bridge and a SCE ref-
erence electrode separated from the bulk of the solution by a dou-
ble bridge were used.
O
O
O
O
O
O
N
N
N
CN
DMAE
N
M
N
175 ºC,
350 W
N
O
CN
N
O
O
N
3
O
O
O
O
O
O
Compound
M
8
7
5
6
Cu
Ni Zn Co
Fig. 2. The synthesis of the metallophthalocyanines.
Fig. 3. 1H NMR spectra of complex 6 in CDCl3.

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I. Acar et al. / Polyhedron 29 (2010) 1475–1484
In situ electrocolorimetric measurements, under potentiostatic
(Ar–H), 2925–2868 (Aliph. C–H), 2230 (C„N), 1598, 1580, 1563,
1489, 1462, 1397, 1321, 1269, 1255, 1137, 1101, 1050, 967, 837,
794, 773. 1H NMR. (CDCl3), (d:ppm): 8.22 (d, 1H, Ar–H), 7.82 (d,
1H, Ar–H), 7.57-7.36 (m, 5H, Ar–H), 7.19–7.09 (m, 2H, Ar–H),
6.82 (d, 1H, Ar–H), 4.35 (t, 2H, CH2–O), 4.24 (t, 2H, CH2–O), 4.05
(t, 4H, CH2–O). 13C NMR. (CDCl3), (d:ppm): 161.75, 154.24,
134.95, 134.40, 127.49, 126.45, 125.77, 125.42, 125.13, 121.79,
120.56, 119.70, 119.23, 117.02, 115.68, 115.23, 107.08, 104.78,
70.02, 69.42, 68.57, 67.76. MS (ES+), (m/z): 358 [M]+. Anal Calc.
for C22H18N2O3: C, 73.73; H, 5.06; N, 7.82. Found: C, 73.76; H,
5.04; N, 7.97%.
control, were obtained using an OceanOptics QE65000 diode array
spectrophotometer at color measurement mode by utilizing a
three-electrode configuration of thin-layer quartz spectroelectro-
chemical cell. The standard illuminant A with 2 degree observer
at constant temperature in a light booth designed to exclude exter-
nal light was used. Prior to each set of measurements, background
color coordinates (x,y, and z values) were taken at open-circuit,
using the electrolyte solution without MPc under study. During
the measurements, readings were taken as a function of time un-
der kinetic control, however only the color coordinates at the
beginning and final of each redox processes were reported.
2.3.2. Synthesis of metal-free phthalocyanine (4)
2.3. Synthesis
Compound 3 (0.3 g, 0.84 mmol), 1.8-diazabicyclo[5.4.0]undec-
7-ene (DBU) (3 drop) and dry n-pentanol (4 ml) was added in a
Schlenk tube and then was heated and stirred at 160 °C for 24 h
under N2. After cooling to room temperature the reaction mixture
refluxed with ethanol (50 ml) to precipitate the product which was
filtered off. The green solid product was washed with hot ethanol,
diethyl ether and dried in vacuo. The green solid product was chro-
matographed on preparative silicagel plate with chloroform:meth-
anol (100:3) as eluents. Yield: 0.105 g (35%), mp > 300 °C. IR (KBr
2.3.1. Synthesis of 4-{2-[2-(1-
naphthyloxy)ethoxy]ethoxy}phthalonitrile (3)
2-[2-(1-Naphthyloxy)ethoxy] ethanol 1 (2 g, 8.62 mmol) was
dissolved in dry DMF (20 ml) under N2 atmosphere and 4-nitropht-
halonitrile 2 (1.5 g, 8.62 mmol) was added to the solution. After
stirring 10 min, finely ground anhydrous K2CO3 (3.6 g, 25.86
mmol) was added portionwise within 2 h with efficient stirring.
The reaction mixture was stirred under N2 at 50 °C for four days.
Then the solution was poured into ice-water (100 g). The precipi-
tate formed was filtered off, washed first with water until the fil-
trate was neutral and then diethyl ether and dried in vacuo over
P2O5. The crude product was crystallized from ethanol. Yield:
tablet) m
max/cmꢀ1: 3291 (N–H), 3049 (Ar–H), 2925–2854 (Aliph.
C–H), 1613, 1577, 1463, 1393, 1378, 1270, 1240, 1122, 1073,
952, 771, 744. 1H NMR. (CDCl3), (d:ppm): 8.27 (bs, 8H, Ar–H),
7.76 (m, 8H, Ar–H), 7.45–7.28 (m, 16H, Ar–H), 7.16 (m, 4H, Ar–
H), 6.82 (m, 4H, Ar–H), 4.33 (m, 16H, CH2–O), 4.08 (m, 16H, CH2–
O). 13C NMR. (CDCl3), (d:ppm): 161.62, 154.34, 136.92, 134.41,
1.64 g (53%), mp: 184–186 °C. IR (KBr tablet)
m
max/cmꢀ1: 3053
Fig. 4. 13C NMR spectra of complex 6 in CDCl3.

I. Acar et al. / Polyhedron 29 (2010) 1475–1484
1479
127.40, 126.39, 125.76, 125.54, 125.19, 125.10, 121.92, 120.50,
120.43, 118.82, 117.16, 116.14, 104.84, 103.91, 70.03, 69.62,
2.3.4. Synthesis of zinc (II) phthalocyanine (6)
Compound 3 (0.3 g, 0.84 mmol) and anhydrous Zn(CH3COO)2
(39 mg, 0.21 mmol) were added in 2-(dimethylamino)ethanol
(DMAE) (3 ml). Then the mixture was irradiated by microwave
oven at 175 °C, 350 W for 8 min. After cooling to room temperature
the reaction mixture refluxed with ethanol (40 ml) to precipitate
the product which was filtered off. The green solid product was
washed with hot ethanol, diethyl ether and dried in vacuo. The
green solid product was chromatographed on preparative silica
gel plate with chloroform:methanol (100:4) as eluents. Yield:
68.20,
e
67.82.
UV–Vis
(chloroform):
kmax/nm:
[(10ꢀ5
dm3 molꢀ1 cmꢀ1)]: 287 (5.17), 611 (4.71), 645 (4.86), 669
(5.08), 707 (5.12). MS (ES+), (m/z): 1436 [M + H]+. Anal Calc. for
C88H74N8O12: C, 73.63; H, 5.20; N, 7.81. Found: C, 73.56; H, 5.33;
N, 7.77%.
2.3.3. Synthesis of nickel(II) phthalocyanine (5)
Compound 3 (0.3 g, 0.84 mmol) and anhydrous NiCl2 (27 mg,
0.21 mmol) were added in 2-(dimethylamino)ethanol (DMAE)
(3 ml). Then the mixture was irradiated by microwave oven at
175 °C, 350 W for 8 min. After cooling to room temperature the
reaction mixture refluxed with ethanol (40 ml) to precipitate the
product which was filtered off. The green solid product was
washed with hot ethanol, diethyl ether and dried in vacuo. The
green solid product was chromatographed on preparative silicagel
plate with chloroform:methanol (100:3) as eluents. Yield: 0.175 g
0.208 g (66%), mp > 300 °C. IR (KBr tablet) m
max/cmꢀ1: 3049 (Ar–
H), 2925–2854 (Aliph. C–H), 1596, 1580, 1463, 1395, 1359, 1269,
1240, 1100, 1056, 953, 771, 774. 1H NMR. (CDCl3), (d:ppm): 8.18
(d, 4H, Ar–H), 7.71–7.60 (m, 8H, Ar–H), 7.41–7.32 (m, 20H, Ar–
H), 7.25 (m, 4H, Ar–H), 6.76 (d, 4H, Ar–H), 4.24 (m, 16H, CH2–O),
4.04 (m, 16H, CH2–O). 13C NMR. (CDCl3), (d:ppm): 167.65, 158.00,
135.04, 134.47, 128.80, 127.85, 127.47, 126.43, 125.79, 125.62,
125.55, 125.23, 125.19, 121.94, 120.88, 120.59, 108.60, 104.82,
70.09, 69.67, 68.42, 67.88. UV–Vis (chloroform): kmax/nm:
(56%), mp > 300 °C. IR (KBr tablet) m
max/cmꢀ1: 3054 (Ar–H), 2925–
[(10ꢀ5 dm3 molꢀ1 cmꢀ1)]: 289 (5.19), 357 (5.00), 619 (4.65), 687
e
2855 (Alif. C–H), 1610, 1580, 1463, 1394, 1270, 1241, 1123, 1098,
1072, 963, 790, 771. 1H NMR. (CDCl3), (d:ppm): 8.15 (d, 4H, Ar–H),
7.69–7.61 (m, 8H, Ar–H), 7.33–7.28 (m, 24H, Ar–H), 6.76 (d, 4H,
Ar–H), 4.28 (m, 16H, CH2–O), 4.04 (m, 16H, CH2–O). 13C NMR.
(CDCl3), (d:ppm): 172.76, 154.49, 135.04, 134.47, 127.47, 126.50,
125.79, 125.57, 125.20, 122.26, 121.81, 120.88, 120.71, 120.44,
119.76, 119.33, 108.61, 104.85, 70.11, 69.55, 68.44, 67.85. UV–Vis
(5.24). MS (ES+), (m/z): 1499 [M + H]+. Anal Calc. for
C88H72N8O12Zn: C, 70.51; H, 4.84; N, 7.48. Found: C, 70.24; H,
4.89; N, 7.43%.
2.3.5. Synthesis of cobalt (II) phthalocyanine (7)
Compound 3 (0.3 g, 0.84 mmol) and anhydrous CoCl2 (27 mg,
0.21 mmol) were added in 2-(dimethylamino)ethanol (DMAE)
(chloroform): kmax/nm: [(10ꢀ5
e
dm3 molꢀ1 cm-1)]: 295 (5.17),
625 (4.89), 677 (5.17). MS (ES+), (m/z): 1491 [M–H]+. Anal Calc.
for C88H72N8O12Ni: C, 70.83; H, 4.86; N, 7.51. Found: C,70.66; H,
4.93; N, 7.45%.
Fig. 5. (A) CVs of H2Pc recorded with different switching potentials at 0.100 mV sꢀ1
scan rate on Pt in DCM/TBAP. (CVs of H2Pc recorded at different scan rates) (B)
SWVs of H2Pc. SWV parameters: pulse size = 100 mV; frequency:25 Hz).
Fig. 6. (A) CVs of ZnPc recorded at at 0.100 mV sꢀ1 scan rate on Pt in DCM/TBAP. (B)
CVs of ZnPc recorded with different switching potentials at 0.100 mV sꢀ1 scan rate.
(C) SWVs of ZnPc. SWV parameters: pulse size = 100 mV; frequency:25 Hz).

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I. Acar et al. / Polyhedron 29 (2010) 1475–1484
(3 ml). Then the mixture was irradiated by microwave oven at
175 °C, 350 W for 8 min. After cooling to room temperature the
reaction mixture refluxed with ethanol (40 ml) to precipitate the
product which was filtered off. The green solid product was
washed with hot ethanol, diethyl ether and dried in vacuo. The
green solid product was chromatographed on preparative silicagel
plate with chloroform:methanol (100:5) as eluents. Yield: 0.195 g
m/z = 1436 [M + H]+ and is in good accord with the suggested
structure.
In the IR spectra of the metallophthalocyanines (5–8) cyclotet-
ramerization of 3 was confirmed by the disappearance of the
sharp C„N stretching vibration at 2230 cmꢀ1. The IR spectra of
NiPc, ZnPc, CoPc and CuPc are also very similar to that of the pre-
cursor H2Pc except for the disappearance of the N–H vibration of
the phthalocyanine core. The 1H NMR spectra of these compound
were almost identical to those of H2Pc 4. 1H NMR spectra of com-
pounds 5, 6 were the broad signals encountered in the case of
compound 5, 6 as a result of the aggregation of phthlocyanine
cores at the considerable high concentration used for the NMR
measurements [27]. In the 1H NMR spectrum of 6 exhibited sig-
nals at d = 8.18 (d, 4H, Ar–H), 7.71–7.60 (m, 8H, Ar–H), 7.41–
7.32 (m, 20H, Ar–H), 7.25 (m, 4H, Ar–H), 6.76 (d, 4H, Ar–H),
4.24 (m, 16H, CH2–O), 4.04 (m, 16H, CH2–O) belonging to aromatic
and aliphatic protons (Fig. 3). In the 13C NMR spectrum of 6 indi-
cated carbon atoms at d = 167.65, 158.00, 135.04, 134.47, 128.80,
127.85, 127.47, 126.43, 125.79, 125.62, 125.55, 125.23, 125.19,
121.94, 120.88, 120.59, 108.60, 104.82, 70.09, 69.67, 68.42, 67.88
(Fig. 4). 1H NMR measurements of the cobalt(II) and copper(II)
phthalocyanine 7, 8 were precluded due to its paramagnetic nat-
ure. In the mass spectrum of compounds 5, 6, 7 and 8 the presence
of molecular ion peaks at m/z = 1491 [M–H]+, 1499 [M + H]+, 1492
[M]+ and 1498 [M + H]+, respectively, confirmed the proposed
structures.
(62%), mp > 300 °C. IR (KBr tablet)
2927–2862 (Aliph. C–H), 1596, 1572, 1506, 1463, 1397, 1269,
m : 3049 (Ar–H),
max/cmꢀ1
1240, 1122, 1099, 1067, 962, 752. UV–Vis (chloroform): kmax/nm:
[(10ꢀ5
e
dm3 molꢀ1 cmꢀ1)]: 295 (5.09), 613 (4.74), 679 (5.06). MS
(ES+), (m/z): 1492 [M]+. Anal Calc. for C88H72N8O12Co: C, 70.82; H,
4.86; N, 7.51. Found: C, 70.65; H, 4.66; N, 7.43%.
2.3.6. Synthesis of copper (II) phthalocyanine (8)
Compound 3 (0.3 g, 0.84 mmol) and anhydrous CuCl2 (28 mg,
0.21 mmol) were added in 2-(dimethylamino)ethanol (DMAE)
(3 ml). Then the mixture was irradiated by microwave oven at
175 °C, 350 W for 8 min. After cooling to room temperature the
reaction mixture refluxed with ethanol (40 ml) to precipitate the
product which was filtered off. The green solid product was
washed with hot ethanol, diethyl ether and dried in vacuo. The
green solid product was chromatographed on preparative silicagel
plate with chloroform:methanol (100:4) as eluents. Yield: 0.154 g
(49%), mp > 300 °C. IR (KBr tablet)
m : 3054 (Ar–H),
max/cmꢀ1
2927–2868 (Aliph. C–H), 1646, 1595, 1577, 1508, 1452, 1396,
1269, 1240, 1132, 1100, 953, 793, 749. UV–Vis (chloroform):
kmax/nm: [(10ꢀ5
e
dm3 molꢀ1 cmꢀ1)]: 283 (5.06), 621 (4.66), 685
(5.01). MS (ES+), (m/z): 1498 [M + H]+. Anal Calc. for C88H72N8O12-
Cu: C, 70.60; H, 4.85; N, 7.48. Found: C, 70.52; H, 4.91; N, 7.46%.
3. Results and discussion
3.1. Synthesis and characterization
The synthesis of substituted phthalocyanines starts generally
with the preparation of the corresponding phthalonitrile precur-
sors. The synthesis of the target metal-free 4 and metallophthalo-
cyanines 5–8 undertaken in this work are shown in Figs. 1 and 2. 4-
{2-[2-(1-naphthyloxy)ethoxy]ethoxy}phthalonitrile
pared from 2-[2-(1-naphthyloxy)ethoxy]ethanol
3
1
was pre-
with 4-
nitrophthalonitrile 2 in dry dimethylformamide containing potas-
sium carbonate as the base. The reaction was carried out in dry
dimethylformamide at 50 °C and gave moderate yields (53%). Com-
parison of the IR spectral data clearly indicated the formation of
compound 3 by the disappearance of the OH band of compound
1 at 3449 cmꢀ1, and the appearance of a new vibration at
2230 cmꢀ1 (C„N). The spectrum of 3 also indicates the presence
of alkyl and CN groups by the intense stretching bands at 2925–
2868 (C–H) and 2230 (C„N) cmꢀ1 1H NMR spectrum of 3, OH
.
group of compound 1 disappeared as expected. 1H NMR spectrum
of 3 exihibited signals at d = 8.22 (d, 1H, Ar–H), 7.82 (d, 1H, Ar–H),
7.57–7.36 (m, 5H, Ar–H), 7.19–7.09 (m, 2H, Ar–H), 6.82 (d, 1H, Ar–
H) belonging to aromatic protons. The proton-decoupled 13C NMR
spectrum indicated the presence of the nitrile carbon atoms in 3 at
d = 115.68 ppm. The MS mass spectrum of compound 3, which
shows a peak at m/z = 358 [M]+, support the proposed formula
for this compound.
According to the IR spectrum of compound 4, the signals for the
C„N groups at 2230 cmꢀ1 for compound 3 disappeared and new
peaks appeared at 3291 and 1613 cmꢀ1 that are dedicated to the
N–H group in the phthalocyanine core of 4. In the 1H NMR spec-
trum of 4, the typical shielding of inner core protons could not
be observed due to the probable strong aggregation of the mole-
cules [26]. The mass spectrum of compound 4 was measured as
Fig. 7. (A) CVs of CoPc recorded with different switching potentials at 0.100 mV sꢀ1
scan rate on Pt in DCM/TBAP. (B) CVs of CoPc recorded at different scan rates. (C)
SWVs of CoPc. SWV parameters: pulse size = 100 mV; frequency:25 Hz).

I. Acar et al. / Polyhedron 29 (2010) 1475–1484
1481
3.2. Electrochemical measurements
signed to the aggregated species (R01 and O01) more than that of
the monomeric ones (R1 and O1) that supports the existence of the
aggregation–disaggregation equilibrium. When the potential is
switched from more positive potentials, an intense peak at 1.550V
is recorded, which shifts to positive potentials during repetitive
scans. During repetitive scans, all couples of zinc(II) phthalocyanine
6 disappear, which indicates the formation of a nonconductive film
of the decomposition product on the electrode surface.
Fig. 7 shows the CV and SWV of cobalt(II) phthalocyanine 7.
Within the electrochemical window of TBAP/DCM in CV measure-
ments, cobalt(II) phthalocyanine 7 undergoes one reversible one
electron oxidation and three reversible one electron reduction pro-
cesses at ꢀ0.37, ꢀ1.45, ꢀ1.77 and 0.59 V respectively. CV and SWV
analysis show that cobalt(II) phthalocyanine 7 also has aggrega-
tion–disaggregation equilibria in solution during positive potential
scans thus the oxidation couple splits into two wave due to elec-
tron transfer of aggregated (O01 at 0.39 V) and monomeric species
(O1 at 0.59 V). Assignments of the redox couple are confirmed by
spectroelectrochemical measurements which are given below. As
the cases in metal-free phthalocyanine 4 and zinc(II) phthalocya-
nine 6, cobalt(II) phthalocyanine 7 also decomposes at more posi-
tive potentials (the wave at 1.38 V).
Fig. 5 shows CV and SWV responses of metal-free phthalocya-
nine 4 recorded with different switching potentials and at various
scan rates. Upon cathodic potential scans, metal-free phthalocya-
nine 4 gives two reversible reduction couples at ꢀ0.79 and
ꢀ1.12 V versus SCE, when the potential is switched before
ꢀ1.30 V (Fig. 5A inset), which are agreement with the reported me-
tal-free phthalocyanine 4 studies in the literature [28–31]. How-
ever, when the potential is switched from more negative
potentials, a very intense couple (R3) at ꢀ1.39 V is recorded
(Fig. 5A). After R3 couple, reverse waves of R1 and R2 couples de-
crease in current intensity. These voltammetric behaviors may
due to the decomposition of the complex at more negative poten-
tials which product reduces at ꢀ1.39 V. Decomposition of metal-
free phthalocyanine 4 is also recorded during positive potential
scans. Metal-free phthalocyanine 4 give a very intense wave at
1.55 V which shifts to positive potentials during repetitive scans.
During repetitive scans, a new wave is recorded at 0.85 V assigned
to the product of decomposition reaction. During repetitive scans,
all couples of metal-free phthalocyanine 4 disappear, which indi-
cates the formation of a nonconductive film of the decomposition
product on the electrode surface.
Zinc(II) phthalocyanine 6 give very similar voltammetric re-
sponses with metal-free phthalocyanine 4 (Fig. 6). It gives three
reduction and an oxidation couples at ꢀ1.17, ꢀ1.42, ꢀ1.79 and
0.56 V respectively, when the potential is scans from 1.0 to
ꢀ2.0 V. Differently, first reduction and oxidation couples of the
complex split into two waves due to aggregation of the complexes.
Diluting the solution decreased the peak current of the waves as-
3.3. Spectroelectrochemical studies
Spectroelectrochemical studies were employed to confirm the
assignments in the CVs of the complexes. UV–Vis spectral changes
of metal-free phthalocyanine 4 are given in Fig. 8. For mononuclear
metal-free phthalocyanine (H2Pc), the symmetry is D2h and there
are two Q-bands at 667 and 698 nm, accompanied by a vibrational
Fig. 8. In situ UV–Vis spectral changes of H2Pc. (A) Eapp = ꢀ1.00 V. (B) Eapp = ꢀ1.35 V. (C) Eapp = 1.00 V (inset: Eapp = 1.60 V). (D) Chromaticity diagram of H2Pc (each symbol
represents the color of electro-generated species; Ã: neutral H2Pc, H2Pcꢀ2, ꢁ: H2Pcꢀ3, 4: H2Pcꢀ4, I: H2Pcꢀ).

1482
I. Acar et al. / Polyhedron 29 (2010) 1475–1484
component to higher energy of the main absorption at 614 nm, re-
sulted from the aggregation of the monomers. When the working
electrode is polarized at ꢀ1.00 V, H2Pc(ꢀ2) is one electron reduced
to form the [H2Pc(ꢀ3)]ꢀ anion (Fig. 8A). When [H2Pc(ꢀ2)] is re-
duced, the bands at 667 and 669 nm decrease and new bands at
580 and 620 nm are recorded. Two new bands at 830 and
931 nm at NIR region are observed. During electrochemical reduc-
tion at ꢀ1.00 V, well-defined isosbestic points are observed at 636
and 740 nm, which demonstrates that the reduction proceeds
cleanly in deoxygenated DCM to give a single, reduced species.
During the second reduction of H2Pc at ꢀ1.35 V, intensities of the
bands at 580 and 620 nm decreases without shift, while new bands
at 502, and 750 nm are recorded (Fig. 8B). At the same time, the
band at 385 nm decreases in intensity. During the reduction of
[H2Pc(ꢀ3)]ꢀ anion, well-defined isosbestic points are observed at
415, 548, 666, and 900 nm, which demonstrates that the reduction
proceeds cleanly to give a single, reduced [H2Pc(ꢀ4)]ꢀ2 species.
During the oxidation of H2Pc at 1.0 V (Fig. 8C), absorption of the
Q-bands decreases in intensity without shift, while the absorption
of the region between 450 and 550 nm and at around 790 nm in-
crease in intensity. Clear isosbestic points are recorded at 405,
573, and 771 nm in the spectra. These changes are typical of the
oxidation of [H2Pc(ꢀ2)] to [H2Pc(ꢀ1)]+ [26–28]. Under potential
application at 1.60 V, decreasing of all bands in intensity indicate
the decomposition of [H2Pc(ꢀ1)]+ monocations.
simultaneously during the spectroelectrochemical measurements.
Without any potential application, solution of H2Pc is bluish green
(x = 0.294 and y = 0.356). As potential is stepped from 0 to ꢀ1.00 V
color of the neutral H2Pc starts to changes and light blue color
(x = 0.2789 and y = 0.3128) of monoanionic form of [H2Pcꢀ3 ꢀ1
]
was obtained at the end of the first reduction. Similarly color of
the dianionic species, [H2Pcꢀ4 ꢀ2
was recorded as light orange
(x = 0.3624 and y = 0.3458). Monocationic species, [H2Pcꢀ1 +
has
light green color (x = 0.3392 and y = 0.3659). Decomposition of
[H2Pcꢀ1 +
do not change the color of the solution significantly
]
]
]
(point I: x = 0.3481 and y = 0.3642). Measurement of the xyz coor-
dinates allows quantification of each color of the redox species that
is very important to decide their possible electrochromic
application.
Zinc(II) phthalocyanine 6 has redox inactive metal centers, thus
indicate ring-based characters for all redox couples during in situ
spectroelectrochemical measurements (Fig. 9). During the poten-
tial application at ꢀ1.20 V, First of all, two bands at 500 and
760 nm and the Q-band at 680 nm increase first and decrease again
in intensity while intensity of the Q-band shoulder at 635 nm de-
creases due to the reduction of aggregated species. Then the Q-
band at 680 nm decreases in intensity without shift, while new
bands in the MLCT region at 443, 580, 872, and 956 nm are ob-
served. These characteristic changes indicate a ring-based redox
process and assign the couple R1 to [ZnIIPcꢀ2]/[ZnIIPcꢀ3 ꢀ1
process
]
The color change of the complexes during the redox processes
were recorded using in situ colorimetric measurements. Fig. 8D
gives the chromaticity diagrams of the complex H2Pc recorded
(Fig. 9A). At the ꢀ1.60 V potential application, while the Q-band at
680 nm and the band at 580 nm decrease in intensity without shift,
new bands are recorded at 510, 793 and 876 nm (Fig. 9B). These
Fig. 9. In situ UV–Vis spectral changes of ZnPc. (A) final part of the spectral changes (inset: initial part of the spectral changes) at Eapp = ꢀ1.20 V. (B) Eapp = ꢀ1.60 V. (C)
Eapp = 0.80 V. (inset: Eapp = 1.60 V). (D) Chromaticity diagram of 6 (each symbol represents the color of electro-generated species; Ã: neutral 6, ZnIIPcꢀ2, ꢁ: ZnIIPcꢀ3, 4:
ZnIIPcꢀ4, I: ZnIIPcꢀ).

I. Acar et al. / Polyhedron 29 (2010) 1475–1484
1483
spectroscopic changes are easily assigned to the reduction of the
monoanionic species, [ZnIIPcꢀ3 ꢀ1 to [ZnIIPcꢀ4 ꢀ2
dianionic species.
Spectroscopic changes given in Fig. 9C are characteristic for the
oxidation of [ZnIIPcꢀ2] to monocationic [ZnIIPcꢀ1 +1
species [32].
center reduction of cobalt(II) phthalocyanine at ꢀ0.50 V potential
application (Fig. 10A). This process resulted in clear isobestic
points at 347, 552, 678, and 756 nm in the spectra. Color change
]
]
]
blue (point Ã: x = 0.2632 and y = 0.3137) to light green (point
ꢁ
:
While the Q-band decreases in intensity, new bands at 500 and
730 nm are recorded during the oxidation process. Well-defined
isosbestic points are observed during each redox processes, which
demonstrates that the redox reactions proceed cleanly to give a
single, reduced/oxidized species. During the potential application
at 1.60 V, spectroscopic changes indicate the decomposition of
the monocationic species. The color changes of the solution during
the redox processes were recorded using in situ colorimetric mea-
surements (Fig. 9D). Without any potential application, the solu-
tion of zinc(II) phthalocyanine is bluish green (point: Ã;
x = 0.2522 and y = 0.3539). As the potential is stepped from 0 to
ꢀ1.70 V, the color of the neutral [ZnIIPcꢀ2] start to changes and
x = 0.3552 and y = 0.406) was recorded as shown in the chromatic-
ity diagram (Fig. 10D). These spectroscopic data assign the first
reduction couple to [CoIIPcꢀ2]/[CoIPcꢀ2 1ꢀ
] . Further reduction of
[CoIPcꢀ2 1ꢀ
]
at ꢀ1.60 V indicate a ligand-based redox process. Be-
cause the Q-band at 704 nm decreases without shift while a new
broad band is recorded at 536 nm. (Fig. 10B). Clear isosbestic
points were observed at 404, 474, 600, and 754 nm in the spectra.
Color changes from green to yellow (point 4: x = 0.3747and y
= 0.3674) was recorded (Fig. 10D). These changes assign the second
reduction couple to [CoIPcꢀ2 1ꢀ/[CoIPcꢀ3 2ꢀ
] ] . Fig. 10C (inset) repre-
sents initial part of the spectral changes during the oxidation pro-
cess at 0.80 V. Decreasing of the shoulder of the Q-band and
increasing the intensity of the Q-band indicate the oxidation of
the aggregated CoPc species. Then the Q-band at 668 nm decreases
without shift and two new bands are recorded at 527 and 727 nm.
These spectroscopic changes indicate ligand-based process and as-
greenish blue color (point:
tained for the monoanionic form of [ZnIIPcꢀ3 ꢀ1
first reduction. Similarly the color of the dianionic species,
[ZnIIPcꢀ4 ꢀ2
ꢁ
; x = 0.2332 and y = 0.3195) was ob-
]
at the end of the
]
was recorded as bluish purple (point: 4; x = 0.2898
and y = 0.314). During the oxidation process, the color of the solu-
tion is changed from bluish green to light yellow (point:I;
x = 0.3434 and y = 0.356).
signed to [CoIIPcꢀ2]/[CoIIPcꢀ1 1+
] [33–37]. Greenish blue color of the
solution changes to first bluish green (point }: x = 0.281 and
y = 0.3473) and then to light green (point I: x = 0.281 and
y = 0.3473) at the end of the oxidation process.
Fig. 10 represents in situ UV–Vis spectral changes and in situ re-
corded chromaticity diagram of cobalt(II) phthalocyanine 7 in
DCM/TBAP during potential application at potentials of the redox
processes. Before potential application, observation of the band
at 625 nm as a sholder of the Q-band at 668 nm indicates the exis-
tence of the aggregated species. Shifting of the Q-band from 668 to
704 nm and observation of new bands at 462 nm indicate metal
4. Conclusion
In this work, we describe the synthetic procedure and charac-
terization of new metal-free and metallophthalocyanines substi-
Fig. 10. In situ UV–Vis spectral changes of 7. (A) Eapp = ꢀ0.50 V. (B) Eapp = ꢀ1.60 V. (C) Eapp = 0.75 V. (D) Chromaticity diagram of 7 (each symbol represents the color of
electro-generated species; Ã: neutral 7, CoIIPcꢀ2, ꢁ: CoIPcꢀ2, 4: CoIPcꢀ3, I: CoIIPcꢀ).

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I. Acar et al. / Polyhedron 29 (2010) 1475–1484
[10] Y. Arslanog˘lu, E. Hamuryudan, Dyes Pigm. 75 (2007) 150.
[11] Z.A. Bayır, Dyes Pigm. 65 (2005) 235.
[12] A. Beck, K.M. Mangold, M. Hanack, Chem. Br. 124 (1991) 2315.
[13] T. Kudo, M. Kimura, K. Hanabusa, H. Shirai, T. Sakaguchi, J. Porphyrins
Phthalocyanines 3 (1999) 65.
tuted with 4-{2-[2-(1-naphthyloxy)ethoxy]ethoxy} groups. The
target symmetrical phthalocyanines were separated by preparative
thin-layer chromatograph and characterized by a combination of
IR, 1H NMR, 13C NMR, elemental analysis and MS spectral data. Vol-
tammetric and spectroelectrochemical studies show that while
metal-free and zinc phthalocyanine complexes give ligand-based,
redox processes, cobalt phthalocyanine complex give both metal
and ligand-based redox processes. All of the complexes decom-
posed at more positive potentials than 1.30 V versus SCE. Definite
determination of the colors of the electro-generated anionic and
cationic form of the complexes is important to decide possible
electrochromic application of the complexes. Electrochromic appli-
cations of the complexes are under investigation.
[14] V.V. Rozhkov, M. Khajehpour, S.A. Inogradov, Inorg. Chem. 42 (2003) 4253.
_
_
[15] H.Y. Yenilmez, I. Özçesßmeci, A.I. Okur, A. Gül, Polyhedron 23 (2004) 787.
[16] H. Kantekin, G. Dilber, Z. Bıyıklıog˘lu, J. Organomet. Chem. 693 (2008) 1038.
[17] Z. Bıyıklıog
˘lu, H. Kantekin, Polyhedron 27 (2008) 1650.
_
[18] Z. Bıyıklıog˘lu, I. Acar, H. Kantekin, Inorg. Chem. Commun. 11 (2008) 630.
[19] H. Kantekin, Z. Bıyıklıog˘lu, E. Çelenk, Inorg. Chem. Commun. 11 (2008) 633.
[20] R.J. Mortimer, Electrochim. Acta 44 (1999) 2971.
[21] A. Koca, T. Ceyhan, M.K. Erbil, A.R. Özkaya, Ö. Bekarog˘lu, Chem. Phys. 340
(2007) 283.
[22] Y.A. Udum, A. Durmußs, G.E. Gunbas, L. Toppare, Org. Electron. 9 (2008) 501.
[23] C. Bolchi, P. Catalano, L. Fumagalli, M. Gobbi, M. Pallavicini, A. Pedretti, A. Villa,
G. Vistoli, E. Valoti, Bioorg. Med. Chem. 12 (2004) 4937.
[24] G.J. Young, W. Onyebuagu, J. Org. Chem. 55 (1990) 2155.
[25] D.D. Perin, W.L.F. Armarego, D.R. Perin, Purification of Laboratory Chemicals,
2nd ed., Pergamon Press, New York, 1985.
Acknowledgment
[26] C.F. van Nostrum, S.J. Picken, A.J. Schouten, R.J.M. Nolte, J. Am. Chem. Soc. 117
(1995) 9957.
[27] M. Brewis, G.J. Clarkson, M. Helliwell, A.M. Holder, N.B. McKeown, Chem. Eur. J.
6 (2000) 4630.
This study was supported by the Research Fund of Karadeniz
Technical University.
[28] L.D. Rollmann, R.T. Iwamoto, J. Am. Chem. Soc. 90 (1968) 1455.
[29] A. Koca, A.R. Özkaya, M. Selcukoglu, E. Hamuryudan, Electrochim. Acta 52
(2007) 2683.
References
[30] A.B.P. Lever, E.R. Milaeva, G. Speier, in: CC. Leznoff, ABP. Lever (Eds.), The
Redox Chemistry of Metallophthalocyanines in Solution in Phthalocyanines:
Properties and Applications, vol. 3, VCH, New York, 1993, pp. 5–27.
[31] R. Li, X. Zhang, I.P. Zhu, D.K.P. Ng, N. Kobayashi, J. Jiang, Inorg. Chem. 45 (2006)
2327.
[1] C.C. Leznoff, A.B.P. Lever, Phthalocyanines: Properties and Applications, vol. 1–
4, VCH, New York, 1989.
[2] G. De La Torre, P. Vazquez, F. Agullo-Lopez, T. Torres, J. Mater. Chem. 8 (1998)
1671.
[3] M. Emmelius, G. Pawlowski, H.W. Vollmann, Angew. Chem., Int. Ed. 28 (1989)
1445.
[4] I. Rosenthal, Photochem. Photobiol. 53 (1991) 859.
[5] G. Guillaud, J. Simon, J.P. Germain, Coord. Chem. Rev. 178 (1998) 1433.
[6] B. Meunier, A. Sorokin, Acc. Chem. Res. 30 (1997) 470.
[7] M.K. Nazeeruddin, R. Humphry-Baker, M. Gratzel, B.A. Murrer, Chem.
Commun. 6 (1998) 719.
[32] D. Kulaç, M. Bulut, A. Altındal, A.R. Özkaya, B. Salih, Ö. Bekarog˘lu, Polyhedron
26 (2007) 5432.
[33] J. Obirai, T. Nyokong, Electrochim. Acta 50 (2005) 3296.
[34] K. Hesse, D. Schlettwein, J. Electroanal. Chem. 476 (1999) 148.
_
_
[35] Ö.A. Osmanbasß, A. Koca, I. Özçesßmeci, A.I. Okur, A. Gül, Electrochim. Acta 53
(2008) 4969.
[36] A. Koca, Electrochem. Commun. 11 (2009) 838.
[37] A. Koca, Sß. Bayar, H.A. Dinçer, E. Gonca, Electrochim. Acta 54 (2009) 2684.
[8] N.B. McKeown, Phthalocyanine Materials: Synthesis, Structure and Function,
Cambridge University Pres, Cambridge, 1998.
[9] Y. Gök, H. Kantekin, M.B. Kılıçaslan, H. Alp, Dyes Pigm. 74 (2007) 692.