Synthesis, characterization, electrochemical and spectroelectrochemical properties of peripherally tetra-substituted metal-free and metallophthalocyanines

Article abstract of DOI:10.1016/j.dyepig.2013.06.033

In this study, the synthesis, electrochemical and spectroelectrochemical properties of peripherally 2-(2,2,4,7-tetramethyl-3,4-dihydroquinolin-1(2H)-yl) ethanol substituted novel metal-free 4, Zn(II) 5, Ni(II) 6, Co(II) 7 and Cu(II) 8 phthalocyanine deriv

Full text of DOI:10.1016/j.dyepig.2013.06.033

Dyes and Pigments 99 (2013) 613e619
Contents lists available at SciVerse ScienceDirect
Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
Synthesis, characterization, electrochemical and
spectroelectrochemical properties of peripherally tetra-substituted
metal-free and metallophthalocyanines
a
b
c
a
a,
_
*
ꢀ
Ays¸e Aktas¸ , Irfan Acar , Atıf Koca , Zekeriya Bıyıklıoglu , Halit Kantekin
a Department of Chemistry, Faculty of Science, Karadeniz Technical University, 61080 Trabzon, Turkey
b Department of Energy Systems Engineering, Faculty of Technology, Karadeniz Technical University, 61830 Trabzon, Turkey
c Department of Chemical Engineering, Engineering Faculty, 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:
In this study, the synthesis, electrochemical and spectroelectrochemical properties of peripherally
2-(2,2,4,7-tetramethyl-3,4-dihydroquinolin-1(2H)-yl)ethanol substituted novel metal-free 4, Zn(II) 5,
Ni(II) 6, Co(II) 7 and Cu(II) 8 phthalocyanine derivatives are reported. These new compounds have been
characterized by using UVeVis, IR, 1H NMR, 13C-NMR (just for phthalonitrile derivative) and MS spec-
troscopic data. Electrochemical and spectroelectrochemical measurements exhibit that while CoPc gives
a metal-based reduction process in addition to the ring-based reduction process, all the other complexes
give common ring reduction reaction of MPcs which have redox inactive metal center. 2-(2,2,4,7-
tetramethyl-3,4-dihydroquinolin-1(2H)-yl)ethanol groups which substituted on the periphery of the
complexes provides electropolymerization of the complexes during the anodic potential scans. Type of
the metal center of the complexes, which was used potential windows and the cycle numbers affect the
character of the polymerization processes during the cyclic voltammetry measurements.
Ó 2013 Elsevier Ltd. All rights reserved.
Received 7 May 2013
Received in revised form
26 June 2013
Accepted 29 June 2013
Available online 10 July 2013
Keywords:
Metallophthalocyanine
Synthesis
Microwave
Electrochemistry
Spectroelectrochemistry
Electropolymerization
1. Introduction
assisted synthesis have many advantages such as reducing chemical
reactions times and side reactions also increasing the yield
Phthalocyanines (Pcs) have remarkable physical and chemical
properties [1]. For many years, their wide application areas such as
in the construction of molecular devices have attracted increasing
unlike classic method does [13]. In this paper, we describe the syn-
thesis and characterization of metallophthalocyanines (MPc;
M ¼ Zn(II), Ni(II), Co(II)) and Cu(II) substituted with 2-(2,2,4,
7-tetramethyl-3,4-dihydroquinolin-1(2H)-yl)ethanol groups by mi-
crowave irradiation.
interest [2]. Because of their powerful delocalized 18-
p electron
aromatic molecules which show strong absorption in the visible
region, they are extensively used as dyestuffs for textiles and inks
[3]. Besides, phthalocyanines can be used electrochromic display
devices, oxidation catalysts, data storage, chemical sensors, liquid
crystals, LangmuireeBlodgett films, photovoltaic solar cells, non-
linear optics application, gas sensors, light emitting diodes and
photodynamic therapy (PDT) which is an alternative method in the
treatment of the cancer [4e11].
It is well known that, phthalocyanine complexes show excellent
electrochromic properties both in solution and as films [14e16]. In
addition, MPcs found area in high tech applications due to their
high chemical and thermal stability, designed flexibility, varied
coordination properties, diversed substitutional alternatives and
interesting electrochemical properties [17e19]. Their electro-
chemical properties can be arranged by incorporating desired
metal and/or substituents. Therefore electrochemical behavior of a
newly synthesized complexes should be analyzed in detail to
decide its possible application in various electrochemical technol-
ogies, thus we have investigated the electrochemical and spec-
troelectrochemical properties of these newly synthesized MPc
complexes.
Since 1980, microwave (MW) irradiation can be used for syn-
thesizing phthalocyanines as an alternative method [12]. Microwave
* Corresponding author. Tel.: þ90 462 377 25 89; fax: þ90 462 325 31 96.
E-mail address: halit@ktu.edu.tr (H. Kantekin).
0143-7208/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.dyepig.2013.06.033

614
A. Aktas¸ et al. / Dyes and Pigments 99 (2013) 613e619
2. Experimental
nm (log ): 678 (4.94), 612 (4.32), 349 (4.79), 308 (4.67). MALDI-
3
TOF-MS, (m/z): Calculated: 1501,37; Found: 1502.75 [M þ H]þ.
2.1. Synthesis
2.1.4. Synthesis of nickel(II) phthalocyanine (6)
2.1.1. Synthesis of 4-[2-(2,2,4,7-tetramethyl-3,4-dihydroquinolin-
1(2H)-yl)ethoxy] phthalonitrile (3)
Synthesized similarly from 5 to 3 by using anhydrous NiCl2.
Yield: 0.056 g (27%). mp: >300 ꢂC. IR (KBr tablet) nmax/cmꢁ1: 3042
(AreH), 2959e2850 (Aliph. CeH), 1728, 1610, 1504, 1464, 1418,
1383, 1343, 1271, 1241, 1169, 1125, 1097, 1088, 960, 796, 750, 595. 1H
NMR. (CDCl3), (d:ppm): 7.27 (12H, AreH), 6.89 (4H, AreH), 6.67
(4H, AreH), 4.64 (8H, CH2eO), 4.00 (8H, CH2eN), 3.05 (4H, -CH-),
2.51(12H, -CH3), 1.58-1.26 (48H, -CH3).UVeVis (THF): lmax, nm
4-Nitrophthalonitrile 2 (0.74 g, 4.3 ꢀ 10ꢁ3 mol) was dissolved in
10 ml of dry DMF under N2 atmosphere, and 2-(2,2,4,7-tetramethyl-
3,4-dihydroquinolin-1(2H)-yl)ethanol 1 (1 g, 4.3 ꢀ 10ꢁ3 mol) was
added to reaction mixture. After being stirred for 30 min at 60 ꢂC,
finely ground anhydrous K2CO3 (1.78 g, 10.5 ꢀ 10ꢁ3 mol) was added
portion wise within 2 h. The reaction mixture was stirred under N2 at
60 ꢂC for 4 days. Thereafter, the reaction mixture was poured into
ice-water and stirred at room temperature for 3 h to yield a crude
product. The mixture was filtered and dried in vacuum over P2O5 for
4 h and recrystallized from ethanol to give dark yellow crystalline
(log ): 673 (4.91), 607 (4.31), 382 (4.18), 328 (4.39). MALDI-TOF-
3
MS, (m/z): Calculated: 1494.7; Found: 1495.86 [M þ H]þ.
2.1.5. Synthesis of cobalt(II) phthalocyanine (7)
Synthesized similarly from 5 to 3 by using anhydrous CoCl2.
Yield: 0.085 g (40%). mp: >300 ꢂC. IR (KBr tablet) nmax/cmꢁ1: 3033
(AreH), 2961e2870 (Aliph. CeH), 1726, 1609, 1572, 1504, 1463,
1418, 1383, 1342, 1281, 1241, 1170, 1098, 1065, 960, 838, 752, 665.
powder. Yield: 0.9 g (56%). mp: 114e117 ꢂC. IR (KBr pellet), nmax
/
cmꢁ1: 3044 (AreH), 2966e2872 (Aliph. CeH), 2231 (C^N), 1600e
1564 (CeO), 1504, 1423,1364, 1321, 1253,1217, 1199, 1151, 1098,1089,
1017, 963, 800, 756, 596.1H NMR. (CDCl3), (
d:ppm): 7.69 (d, H, AreH),
UVeVis (THF): lmax, nm (log ): 665 (4.77), 605 (4.24), 306 (4.76).
3
7.27e7.08 (m, 3H, AreH), 6.59 (d, 1H, AreH), 6.40 (s, 1H, AreH), 4.19
(t, 4H, CH2eO), 3.88 (m, 2H, CH2eN), 2.83 (m, -CH-), 2.30 (s, 3H,
-CH3), 1.83e1.74 (m, 2H eCH2), 1.59e1.20 (m, 9H -CH3). 13C-NMR.
MALDI-TOF-MS, (m/z): Calculated: 1494.93; Found: 1495.09
[M þ H]þ.
(CDCl3), (d:ppm): 162.14, 144.32, 136.83, 135.49, 126.51, 126.31,
2.1.6. Synthesis of copper(II) phthalocyanine (8)
120.02, 119.48, 117.75, 117.67, 115.93(C^N), 115.44(C^N), 111.97,
107.58, 67.35, 54.86, 47.18, 43.75, 29.83, 27.32, 25.07, 22.05, 20.25. MS
(ESI), (m/z): 359 [M]þ.
Synthesized similarly from 5 to 3 by using anhydrous CuCl2.
Yield: 0.024 g (13%). mp: >300 ꢂC. IR (KBr tablet) nmax/cmꢁ1: 3035
(AreH), 2969e2854 (Aliph. CeH), 1728, 1607, 1504, 1486, 1460,
1364, 1340, 1284, 1242, 1195, 1123, 1017, 837, 797, 756, 665, 595.
2.1.2. Synthesis of metal-free phthalocyanine (4)
UVeVis (THF): lmax, nm (log ): 678 (4.80), 611 (4.32), 337 (4.87).
3
A mixture of phthalonitrile 3 (0.2 g, 0.56 ꢀ 10ꢁ3 mol) and cat-
alytic amount of 1.8-diazabicyclo[5.4.0]undec-7-ene (DBU) in 2 ml
of dry n-pentanol was heated and stirred at 160 ꢂC in a sealed glass
tube for 16 h under N2. After being cooled to room temperature the
green crude product was precipitated with ethanol, filtered and
washed first with ethanol then diethyl ether and then dried in
vacuo. Finally, pure metal-free phthalocyanine was obtained
by column chromatography which is placed silica gel using
CHCl3:CH3OH (10:1) as solvent system. Yield: 0.098 g (49%). mp:
>300 ꢂC. IR (KBr tablet) nmax/cmꢁ1: 3292 (NeH), 3040 (AreH),
2963e2855 (Aliph. CeH), 1729, 1610, 1571, 1504, 1467, 1426, 1342,
1324, 1240, 1168, 1116, 1098, 1016, 797, 756, 596. 1H NMR. (CDCl3),
MALDI-TOF-MS, (m/z): Calculated: 1499.55; Found: 1500.42
[M þ H]þ.
3. Results and discussion
3.1. Syntheses and characterization
Starting
from
2-(2,2,4,7-tetramethyl-3,4-dihydroquinolin-
1(2H)-yl)ethanol 1 and 4-nitrophthalonitrile 2, the general syn-
thetic route for the synthesis of new metal-free and metal-
lophthalocyanines are given in Figs. 1 and 2. The synthesis of
compound 3 is based on the reaction of 2-(2,2,4,7-tetramethyl-3,4-
dihydroquinolin-1(2H)-yl)ethanol 1 with 4-nitrophthalonitrile 2
(in dry DMF and in the presence of dry K2CO3 as base, at 55 ꢂC in
96 h). Cyclotetramerization of the phthalonitrile derivative 3 to the
metal-free phthalocyanine 4 was accomplished in n-pentanol in
the presence of a few drops of 1,8-diazabicyclo[5.4.0]undec-7-ene
(DBU) as a strong base at 160 ꢂC in sealed tube. The metal-
lophthalocyanines 5e8 were obtained by the anhydrous metal salts
[Zn(CH3COO)2, NiCl2, CoCl2 and CuCl2] in 2-(dimethylamino)
ethanol by microwave irradiation. The structures of the target
compounds were confirmed using UVeVis, IR, 1H NMR, 13C NMR
(just for phthalonitrile derivative) and MS spectral data.
(d:ppm): 8.97 (4H, AreH), 8.33 (4H, AreH), 7.56 (4H, AreH), 7.28
(12H, AreH), 6. 91 (4H, AreH), 5.66 (4H, AreH), 4.63 (8H, CH2eO),
3.94 (8H, CH2eN), 3.04 (4H, -CH-), 2.49 (12H, -CH3), 1.60 (8H, -CH3),
1.44 (28H, -CH3). UVeVis (THF): lmax, nm (log ): 703 (4.90), 666
3
(4.85), 643 (4.45), 605 (4.24), 383 (4.37), 343 (4.67), 290 (4.5).
MALDI-TOF-MS, (m/z): Calculated: 1439.84; Found: 1439.24 [M]þ.
2.1.3. Synthesis of zinc(II) phthalocyanine (5)
A mixture of phthalonitrile 3 (0.15 g, 0.42 ꢀ 10ꢁ3 mol), anhy-
drous metal salts Zn(CH3COO)2 (0.038 g, 0.21 ꢀ 10ꢁ3 mol), and dry
DMAE (1 ml) was irradiated in a microwave oven at 175 ꢂC, 350 W
for 4 min. After being cooled to room temperature, the reaction
mixture was precipitated by the addition of ethanol and green
precipitate was filtered off. The obtained green product was filtered
off, washed with ethanol and diethyl ether and then dried in vacuo.
Purification of the solid products were accomplished by column
chromatography which is placed silica gel using CHCl3:CH3OH (5:1)
as solvent system. Yield: 0.058 g (36%). mp: >300 ꢂC. IR (KBr tablet)
nmax/cmꢁ1: 3040 (AreH), 2960-2856 (Aliph. CeH), 1727, 1664,1609,
1463, 1448, 1364, 1336, 1283, 1238, 1198, 1170, 1090, 1053, 962, 838,
In the IR spectra of compound 3 was clearly confirmed by the
disappearance of the OH and appearance of the new vibration C^N
band at 2231 cmꢁ1. In the 1H NMR spectrum of 3, OH group of
compound 1 disappeared as being expected. 1H NMR spectrum of 3
showed new signals at
aromatic protons. In the 13C NMR spectrum of 3 indicated the
presence of nitrile carbon atoms in 3 at
d
¼ 7.24e7.09 (m, 3H, AreH) belonging to
d
¼ 115. 93 and 115. 44 ppm.
The MS spectrum of compound 3, which shows a peak at m/z ¼ 359
[M]þ support the proposed formula for this compound.
796, 747. 1H NMR. (CDCl3), (
d:ppm): 8. 70 (4H, AreH), 8.11 (4H, Are
After transformation of the dinitrile 3 to the phthalocyanines,
the sharp C^N vibration around 2231 cm-1 disappeared. IR spectra
of phthalocyanines 4e8 are very similar, with the exception of the
metal-free 4 which shows an NH stretching band peak at 3292 cm-1
H), 7.73 (4H, AreH), 7.27 (12H, AreH), 6.83 (4H, AreH), 6.61 (4H,
AreH), 4.53 (8H, CH2eO), 3.83 (8H, CH2eN), 3.00 (4H, -CH-), 2.44
(12H, -CH3), 1.66 (8H, -CH3), 1.39 (28H, -CH3). UVeVis (THF): lmax
,

A. Aktas¸ et al. / Dyes and Pigments 99 (2013) 613e619
615
CH3
CH3
N
CN
CH3
CH3
dry K2CO3
N
O
CH3
CH3
H3C
dry DMF
50oC
H3C
O2N
CN
HO
NC
2
1
DBU
160 oC
NC
n-pentanol
3
H3C
CH3
CH3
H3C
CH3
N
N
H3C
O
CH3
O
CH3
N
HN
N
N
N
N
NH
H3C
H3C
CH3
N
H3C
N
CH3
O
O
N
H3C CH3
CH3
4
Fig. 1. The synthesis route of the metal-free phthalocyanine 4.
due to the inner core. The 1H NMR spectra of 4 indicated charac-
teristic protons between 8.97 and 1.44 ppm. But, the NH protons of
metal-free phthalocyanine 4 could not be observed owing to the
probable strong aggregation of the molecules [20,21]. In the mass
spectra of compound 4, the presence of the characteristic molecular
ion peak at m/z ¼ 1439.24 [M]þ confirmed the proposed structure.
In the IR spectra of the metallophthalocyanines 5e8 cyclo-
tetramerization of 3 was confirmed by the disappearance of the
sharp C^N stretching vibration at 2231 cmꢁ1. The IR spectra of
ZnPc, NiPc, CoPc and CuPc are also very similar to that of the pre-
cursor H2Pc. The 1H NMR spectra of compound 7 and 8 could not be
determined because of the paramagnetic nature. The 1H NMR
spectra of the compounds 5 and 6 were almost same to those of
H2Pc 4. In the MALDI-mass spectrum of Zn, Ni, Co, Cu phthalocy-
anines, the presence of molecular ion peaks at m/z ¼ 1502.75
[M þ H]þ for Zn(II), 1495.86 [M þ H]þ for Ni (II), 1495.09 [M þ H]þ
for Co(II) and 1500.43 [M þ H]þ for Cu(II) respectively, confirmed
the proposed structures.
and the other one is in the UV region at about 300e500 nm
(B band), both correlate to * transitions [22e24]. The ground
p
/ p
state electronic spectra of the compounds showed characteristic
absorptions in the Q band region at 703/666 nm for compound 4,
678 nm for compound 5, 673 for compound 6, 665 nm for com-
pound 7, 678 nm for compound 8 in THF. B band absorptions of
the metal-free and metallophthalocyanines 5e8 were observed
at (383, 290), (349, 308), (382, 328), 306 nm, 337 respectively
(Figs. 3 and 4).
3.2. Voltammetric measurements
The electrochemical analyses of the MPc complexes were per-
formed in DCM/TBAP electrolyte system on a Pt working electrode.
The results of these analyses are tabulated in Table 1. The assign-
ments of the redox couples and estimated electrochemical pa-
rameters including the half-wave peak potentials (E1/2), ratio of
anodic to cathodic peak currents (Ip,a/Ip,c), peak to peak potential
The UVeVis spectra of the phthalocyanine complexes which
exhibit typical electronic spectra with two strong absorption re-
gions, one of them is in the visible region at 600e700 nm (Q band)
separations (
reduction processes (
complexes. As shown in Table 1, H2Pc, NiPc, ZnPc and CuPc illustrate
D
Ep), and difference between the first oxidation and
DE1/2) are listed for the comparison of the

616
A. Aktas¸ et al. / Dyes and Pigments 99 (2013) 613e619
CH3
H3C
H3C
H3C
N
CH3
CH3
H3C
CH3
CH3
N
O
N
MW
175 oC 350 Watt
DMAE
O
CH3
H3C
O
CH3
N
N
NC
CN
N
N
N
N
N
N
H3C
H3C
CH3
H3C
N
CH3
O
O
N
H3C CH3
CH3
Compound 5
6 7 8
Cu
M
Zn Ni Co
Fig. 2. The synthesis route of metallophthalocyanines 5, 6, 7 and 8.
very similar voltammetric responses, because all of these com-
plexes have redox inactive metal centers and gives only Pc ring-
based redox processes. All of these complexes give two reversible
reduction processes at the cathodic potentials and electro-
polymerized on the working electrode during the anodic potential
scans. The only differences are the small potential differences due
to the different effective nuclear charge of the metal center of these
complexes and the polymerization mechanism. Fig. 5 represents
the CV and SWV responses of NiPc as a representative of H2Pc,
NiPc, ZnPc and CuPc complexes. Within the potential window of
DCM/TBAP electrolyte system, NiPc illustrates two diffusion
controlled and quasi-reversible reductions processes. The couples,
are chemically reversible and diffusion controlled with respect to
[Ipan1/2] and Ip,a/Ip,c values [25]. These voltammetric analyses are
supported with the CV measurements with different vertex po-
tentials given in Fig. 5a. As shown in this figure, altering the vertex
potential does not affect the character of the redox processes.
Fig. 5b illustrates the repetitive CV responses of NiPc during the
anodic potential scans. As shown in this figure, during the first
anodic potential scan, a huge anodic peak is recorded at 1.16 V and
its cathodic couple is recorded at 0.31 V. During the repetitive CV
scan these waves increase in current intensity with potential shift.
While
1.50
D
Ep value is 0.85 V for the first scan this value increase to
for the 20 cycle. The peak current of the electro-
V
R1 at ꢁ0.94 V (
at ꢁ1.29 V( Ep ¼ 85 mV and Ip,a/Ip,c ¼ 0.93), are resolved well. The
reduction couples of NiPc are electrochemically quasi-reversible at
all scan rates with respect to Ep and Ip,a/Ip,c values. These processes
D
Ep ¼ 100 mV and Ip,a/Ip,c ¼ 0.96) and R2
polymerization waves increases continuously with the consecutive
CV cycles. Changing the potential window of the CV cycles alters
the polymerization process completely. While only an anodic
irreversible electropolymerization couple is recorded during the
D
D
Fig. 3. UVeVis absorption spectra changes of compounds
4
and
5
in THF at
Fig. 4. UVeVis absorption spectra changes of compounds 6, 7 and 8 in THF at
1 ꢀ 10ꢁ5 mol dmꢁ3
.
1 ꢀ 10ꢁ5 mol dmꢁ3
.

A. Aktas¸ et al. / Dyes and Pigments 99 (2013) 613e619
617
Table 1
Voltammetric data of the complexes with the related MPcs. All voltammetric data
were given versus SCE.
Complex
H2Pc
Electropolymerization peaks
MII/MI Ring reductions
aE1/2
bDEp (mV) 80d
0.73
0.63
100d
0.55
e
e
e
e
e
e
e
e
e
e
e
e
ꢁ0.81 ꢁ1.16
62 65
0.97 0.85
ꢁ0.94 ꢁ1.29
100 95
0.98 0.89
ꢁ0.95 ꢁ1.30
105 95
0.97 0.94
ꢁ0.85 ꢁ1.22
85 110
0.88 0.78
e
e
cIp,a/Ip,c
aE1/2
bDEp (mV)
cIp,a/Ip,c
aE1/2
bDEp (mV)
cIp,a/Ip,c
aE1/2
bDEp (mV)
cIp,a/Ip,c
aE1/2
e
e
e
e
e
e
e
e
e
e
e
e
e
e
NiPc
ZnPc
CuPc
CoPc
a
0.80
375d
0.56
140d
e
e
0.77
250d
0.54
110d
e
e
0.77
110d
0.62
88d
e
e
Fig. 6. Repetitive CVs of NiPc recorded with in the both anodic and cathodic potential
0.77
100e
0.63
60e
ꢁ0.37 ꢁ1.50
68 62
0.87 0.91
e
e
e
windows of DCM/TBAP at 0.100 V sꢁ1 scan rate on a Pt working electrode.
bDEp (mV)
cIp,a/Ip,c
e
e
from 1.50 to 0.0 V. In addition, a second cathodic wave, P2c, is
recorded at 0.50 V. During the consecutive potential scans, while
the R1 and R2 disappeared completely a new reduction peak, Pc , is
recorded at ꢁ1.41 V, which shifts to negative potentials with3de-
creases in current intensity and finally disappears. When P3cpeak is
recorded, a new wave P2a starts to increase at 0.61 V. However, when
the P3c wave disappears, the P2a wave decreases in intensity. After 6
CV cycle, all waves start to decrease in current intensity due to the
finalizing of the electropolymerization. In summary, when negative
potentials are scanned with positive potentials, more redox pro-
cesses are observed and the electropolymerization process is more
reversible. However, the electropolymerization process finishes
after the 6 CV cycle. Similar polymerization processes were also
recorded with H2Pc, ZnPc and CuPc complexes.
E1/2 values ((Epa þ Epc)/2) were given versus SCE and Fc/Fcþ (in parenthesis) at
0.100 V sꢁ1 scan rate.
b
D
Ep ¼ Epa ꢁ Epc
.
c
d
e
Ip,a/Ip,c for reduction, Ip,c/Ip,a for oxidation processes.
Recorded by SWV.
DEp values derived from the first CV cycle.
anodic potential scans. The number of peaks, their reversibility and
peak currents change completely, when both of the anodic and
cathodic potentials are scanned. Fig. 6 represents the repetitive CV
responses of NiPc between ꢁ2.00 and þ1.50 V. During the first scan
from 0.00 V to ꢁ2.0 V, NiPc gives two reduction peaks, R1 at ꢁ1.03 V
and R2 at ꢁ1.37 V. During the reverse scan from ꢁ2.0 to 1.50 V,
anodic couples of R1 and R2 are recorded at ꢁ0.86 V at ꢁ1.24 V
respectively at the cathodic side of the voltammograms. On the
anodic side, a huge anodic wave P1a, is recorded at 1.00 V and its
cathodic couple, P1c , is recorded at 0.62 V during the potential scan
Fig. 7 shows the CV and SWV responses of CoPc in DCM/TBAP
electrolyte system. CoPc displays two well-resolved reversible and
diffusion controlled reduction processes. SWVs clearly show the
chemical and electrochemical reversibility of the redox processes
Fig. 5. (a) CVs of NiPc at various scan rates during the cathodic potential scan (b)
Repetitive CVs of NiPc during the anodic potential scan at 0.100 V sꢁ1 scan rate on a Pt
working electrode in DCM/TBAP.
Fig. 7. (a) CVs of CoPc at various scan rates during the cathodic potential scan. (b)
SWVs of CoPc at various scan rates during the cathodic potential scan.

618
A. Aktas¸ et al. / Dyes and Pigments 99 (2013) 613e619
(Fig. 7b). In practical applications, DEp of a couple is compared with
that of universal indicator ferrocene/ferrocenium couple to decide
the reversibility of a couple. In our system, Eps were changed from
60 to 110 mV for ferrocene with increasing scan rates from 0.010 to
1.00 V sꢁ1. When compared with the responses of ferrocene,
Ep
D
D
values of both reduction processes of CoPc are in electrochemical
reversibility range. The effect of coupled chemical reactions to the
electron transfer reactions is illustrated with Ip,a/Ip,c ratio change as
a function of the scan rate. Both reduction processes that are
recorded with CoPc are purely diffusion that are controlled with
respect to unit Ip,a/Ip,c ratio at all scan rates. Moreover reversibility
of these couples can be concluded with respect to symmetry and
peak current ratios of the waves that are recorded during the for-
ward and reverse SWV scans (Fig. 7b) [25].
Fig. 8 illustrates the repetitive CV responses of CoPc in DCM/
TBAP. Within the electrochemical window of DCM/TBAP in CV
measurements between 1.60 and ꢁ1.80 V, CoPc undergoes two
reversible one-electron reduction processes during the first
cathodic cycle (Fig. 8). However CoPc gives two huge redox couples
at 0.63 V ðP1a=P1c Þ and 0.77 V ðP2a=P2c Þ due to the polymerization of
the complex on the working electrode. In addition to the anodic
polymerization couples, a new small reduction peak increases
at ꢁ1.36 V. All peaks due to the polymerization increases in current
intensity as a function of repetitive CV scan until 10. CV cycle. When
they are compared with NiPc, wave of the polymers of CoPc are
more reversible and increases continuously in current intensity as a
function of CV scan until 10. CV cycle.
3.3. Spectroelectrochemical measurements
Spectroelectrochemical studies were employed to confirm the
assignments of the redox couples that were recorded in the CVs and
SWVs of the complexes. H2Pc, NiPc, ZnPc and CuPc complexes have
redox inactive metal center, thus UVeVis spectral changes which
were characteristic ring-based reduction reactions were recorded
during the in-situ spectroelectrochemical measurements. CoPc has
redox active metal center, thus in-situ spectroelectrochemical
measurements were performed for the assignments of the redox
couples.
Fig. 9 represents in situ UVeVis spectral changes and in situ
recorded chromaticity diagram of CoPc in DCM/TBAP during the
electron transfer processes. During the first reduction process,
while the Q band shifts from 677 nm to 708 nm, a new band en-
hances at 475 nm. These spectral changes characterize the forma-
tion of [CoIPcꢁ2 1ꢁ
(Fig. 9a) [26e32]. This process did not give clear isosbestic points.
]
species under the applied potential at ꢁ0.50 V
Fig. 9. In-situ UVeVis spectral changes of CoPc in DCM. a) Eapp
¼
ꢁ0.6
V b)
Eapp ¼ ꢁ1.70 V c) Chromaticity diagram (each symbol represents the color of electro-
ꢁ1
ꢁ2
.
generated species;⃞: [CoIIPcꢁ2],⃝: [CoIPcꢁ2
]
D
: [CoIPcꢁ3
]
The isosbestic points at around 390, 550 and 690 nm in the spectra
isolate during the reduction which indicates presence of more than
one reduced species. These species may be aggregated CoPc spe-
cies. It is documented well in the literature that MPc complexes can
aggregate especially in the non-coordinating solvent media, e.g.
DCM. While mono anionic CoPc species generally give blue color
[26e29], color of the CoPc studies here form green (point ⃝:
x ¼ 0.3227 and y ¼ 0.3829) monoanionic form after the first
reduction process (Fig. 9c). Spectral changes during the second
reduction of CoPc studied here are very different than the CoPc
complexes in the literature. In the literature it is documented that
the Q band of the CoPc decreased in intensity while a broad band
was recorded at around 550 nm. However here, while the Q band
at 708 nm stays stable, the band at 675 nm increases in intensity.
Fig. 8. Repetitive CVs of CoPc recorded with in the both anodic and cathodic potential
windows of DCM/TBAP at 0.100 V sꢁ1 scan rate on a Pt working electrode.

A. Aktas¸ et al. / Dyes and Pigments 99 (2013) 613e619
619
The band that is characterizing the CoI center at 475 nm stays as
unchanged (Fig. 9b). The band at 475 nm indicates that after the
second reduction process, the oxidation state of the cobalt center is
one, thus the second reduction process should be a ring-based
reduction process. All band decreases are in intensity under the
applied potential at 1.00 V. Because under 1.00 V CoPc electro-
polymerized on the working electrode, which caused to decrease of
the CoPc concentration. Decreasing the concentration of CoPc
causes to decreasing of the absorption bands. Color changes during
the redox processes are represented in Fig. 9c.
[8] Leznoff CC, Lever ABP. Phthalocyanines: properties and applications, vol. 4.
New York: VCH Publisher; 1996.
[9] Pan Y, Chen W, Lu S, Zhang Y. Novel aqueous soluble cobalt phthalocyanine:
synthesis and catalytic activity on oxidation of 2-mercaptoethanol. Dyes Pigm
2005;66:115e21.
[10] McKeown NB. Phthalocyanine materials. Cambridge: Cambridge University
Press; 1998.
[11] Jori G. Tumour photosensitizers: approaches to enhance the selectivity and
efficiency of photodynamic therapy. J Photochem Photobiol B Biol 1996;36:
87e93.
[12] Kingston HM, Haswell SJ. Microwave-enhanced chemistry: fundamentals,
sample preparation and applications. Washington D.C: American Chemical
Society; 1997. p. 3.
_
ꢀ
[13] Acar I, Kantekin H, Bıyıklıoglu Z. The synthesis, using microwave irradiation
and characterization of novel metal free and metallophthalocyanines.
J Organomet Chem 2010;695:151e5.
4. Conclusion
[14] Mortimer RJ. Organic electrochromic materials. Electrochim Acta 1999;44:
2971e81.
In this study, the synthesis of new soluble metal-free 4 and
metallophthalocyanine (Zn, Ni, Co and Cu) 5e8 complexes
were described and these new complexes were characterized by IR,
1H NMR, 13C NMR (just for phthalonitrile derivative), UVeVis
(for phthalocyanine complexes) and MALDI-MS spectra. Electro-
chemical and spectroelectrochemical measurement revealed that
incorporation redox active metal centers, CoII into the phthalocy-
anine core extend the redox richness of the Pc ring with the
reversible metal-based reduction and oxidation couples in addition
to the common Pc ring-based electron transfer processes. This
expanded redox behavior of the complexes are the desired prop-
erties of the electrochemical applications, especially, electro-
catalytic, electrochromic and electrosensing applications. All
complexes 4e9 electro polymerized on the Pt working electrode.
Type of the metal center of the complexes, potential window of the
technique, and the cycle numbers of CV affect the character of the
polymerization processes. In-situ electrocolorimetric measure-
ments of the new complexes allow quantification of color co-
ordinates of the each electrogenerated anionic and cationic redox
species. Different color of the electrogenerated species indicates
their possible application in the display technologies, e.g. electro-
chromic and data storage application.
ꢀ
[15] Koca A, Ceyhan T, Erbil MK, Özkaya AR, Bekaroglu Ö. Electrochemistry and
spectroelectrochemistry of tert-butylcalix[4]arene bridged bis double-decker
lutetium(III) phthalocyanine, Lu2Pc4 and dimeric lutetium(III) phthalocya-
nine, Lu2Pc2(OAc)2. Chem Phys 2007;340:283e92.
ꢀ
[16] Kulaç D, Bulut M, Altındal A, Özkaya AR, Salih B, Bekaroglu Ö. Synthesis and
characterization of novel 4-nitro-2-(octyloxy)phenoxy substituted symmet-
rical and unsymmetrical Zn(II), Co(II) and Lu(III) phthalocyanines. Polyhedron
2007;26:5432e40.
[17] Leznoff CC, Lever ABP, editors. Phthalocyanines properties and applications,
vol. 3. Wiley-VCH; 1993.
[18] Lukyanets EA, Nemykin VN. The key role of peripheral substituents in the
chemistry of phthalocyanines and their analogs. J Porph Pthalocyan 2010;14:
1e40.
[19] Nemykin VN, Lukyanets EA. Synthesis of substituted phthalocyanines. Arkivoc
2010:136e208.
_
[20] Acar I, Bayrak R, Saka ET, Biyiklioglu Z, Kantekin H. Peripherally tetra-
substituted metal-free, metallophthalocyanines and their quaternized de-
rivatives: synthesis, spectroscopic characterization and catalytic activity of
cobalt phthalocyanine in 4-nitrophenol oxidation. Polyhedron 2013;50:
345e53.
[21] Biyiklioglu Z, Koca A, Kantekin H. Synthesis, electrochemical, in situ spec-
troelectrochemical and in situ electrocolorimetric characterization of new
phthalocyanines peripherally fused to four flexible crown ether moieties.
Polyhedron 2009;28:2171e8.
[22] Gök Y, Kantekin H, Kılıçaslan MB, Alp H. The synthesis and characterization of
new metal-free and nickel(II) phthalocyanines containing tetraazatrioxa
macrotricyclic moieties. Dyes Pigm 2007;74:692e8.
[23] S¸ ener MK, Koca A, Gül A, Koçak MB. Synthesis and electrochemical charac-
terization of biphenyl-malonic ester substituted cobalt, copper, and palladium
phthalocyanines. Polyhedron 2007;26:1070e6.
ꢀ
[24] Arslanoglu Y, Hamuryudan E. Synthesis and derivatization of near IR
Appendix A. Supplementary data
absorbing titanylphthalocyanines with dimethylaminoethylsulfanyl sub-
stituents. Dyes Pigm 2007;75:150e5.
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.dyepig.2013.06.033.
[25] Kissinger PT, Heineman WR. Laboratory techniques in electroanalytical
chemistry. 2nd ed. New York: Marcel Dekker; 1996. p. 51e163.
ꢀ
ꢀ
[26] Erdogmus¸ A, Koca A, Ugur AL, Erden I. Synthesis, electrochemical and spec-
troelectrochemical properties of highly soluble tetra substituted phthalocya-
nines with [4-(thiophen-3-yl)-phenoxy]. Synth Met 2011;161:1319e29.
[27] Lever ABP, Minor PC, Wilshire JP. The electrochemistry of manganese
phthalocyanines in non aqueous media. Inorg Chem 1981;20:2550e3.
[28] Yarasir MN, Kandaz M, Koca A, Salih B. Polytopic cation receptor functional
phthalocyanines: synthesis, characterization, electrochemistry and metal ion
binding. Polyhedron 2007;26:1139e47.
References
[1] Durmus¸ M, Yaman H, Göl C, Ahsen V, Nyokong T. Water-Soluble quaternized
Mercaptopyridine-substituted zinc-phthalocyanines: synthesis photophysical,
photochemical and bovine serum albümin binding properties. Dyes Pigm
2011;91:153e63.
[29] Koca A, Bayar S¸ , Dinçer HA, Gonca E. Voltammetric, in-situ spectroelec-
trochemical and in-situ electrocolorimetric characterization of phthalocya-
nines. Electrochim Acta 2009;54:2684e92.
[2] Karaca H, Sezer S, Tanyeli C. Synthesis of L-prolinol substitued novel optically
active phthalocyanines. Dyes Pigm 2011;90:100e5.
_
[3] Özçes¸ meci M, Sorar I, Hamuryudan E. Synthesis, optical and structural studies
of tetrakis[4-(20,30,40,50,60-pentafluorobenzyloxy)benzyloxy]-substitued met-
allo-phthalocyanines. Synth Met 2012;162:154e61.
[30] Alemdar A, Özkaya AR, Bulut M. Preparation, characterization, electrochem-
istry and in situ spectroelectrochemistry of novel a-tetra[7-oxo-3-(2-chloro-
4-fluorophenyl)coumarin]-substituted metal-free, cobalt and zinc phthalo-
cyanines. Synth Met 2010;160:1556e65.
[4] Mortimer RJ. Electrochromic materials. Chem Soc Rev 1997;26:147e56.
[5] Zhong A, Zhang Y, Biaz Y. Structures and spectroscopic properties of non-
peripherally and peripherally substituted metal free phthalocyanines: a sub-
stitution effect study based on density functional theory calculations. J Mol
Grap Model 2010;29:470e80.
[6] Leznoff CC, Lever ABP. Phthalocyanines: properties and applications, vol. 1.
New York: VCH Publisher; 1989.
[7] Moser FH, Thomas LR. Phthalocyanine compound. New York: Reinhold; 1963.
123e45D.
[31] Agboola B, Ozoemena KI, Nyokong T. Synthesis and electrochemical char-
acterisation of benzyl mercapto and dodecylmercapto tetra substituted
cobalt, iron and zinc phthalocyanines complexes. Electrochim Acta 2006;51:
4379e87.
[32] Nombona N, Nyokong T. The synthesis, cyclic voltammetry and spectroelec-
trochemical studies of Co(II) phthalocyanines tetra-substituted at the
a and b
positions with phenylthio groups. Dyes Pigm 2009;80:130e5.