Novel 4-(2-(benzo[d]thiazol-2-yl)phenoxy) substituted phthalocyanine derivatives: Synthesis, electrochemical and in situ spectroelectrochemical characterization

Article abstract of DOI:10.1016/j.jorganchem.2014.01.012

In this study, the new tetra peripherally 4-(2-(benzo[d]thiazol-2-yl) phenoxy)-substituted metal-free (4), zinc(II) (5), lead(II) (6), cobalt(II) (7) and copper(II) (8) phthalocyanine derivatives, which are organo-soluble, have been synthesized for the fi

Full text of DOI:10.1016/j.jorganchem.2014.01.012

Accepted Manuscript
Novel 4-(2-(benzo[d]thiazol-2-yl)phenoxy) substituted phthalocyanine derivatives:
Synthesis, electrochemical and in situ spectroelectrochemical characterization
Asiye Nas, Halit Kantekin, Atıf Koca
PII:
S0022-328X(14)00027-8
10.1016/j.jorganchem.2014.01.012
JOM 18453
DOI:
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 25 July 2013
Revised Date: 10 January 2014
Accepted Date: 13 January 2014
Please cite this article as: A. Nas, H. Kantekin, A. Koca, Novel 4-(2-(benzo[d]thiazol-2-yl)phenoxy)
substituted phthalocyanine derivatives: Synthesis, electrochemical and in situ spectroelectrochemical
characterization, Journal of Organometallic Chemistry (2014), doi: 10.1016/j.jorganchem.2014.01.012.
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ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT
Novel 4-(2-(benzo[d]thiazol-2-yl)phenoxy) substituted phthalocyanine
derivatives: Synthesis, electrochemical and in situ
spectroelectrochemical characterization
a
a*
b
Asiye Nas , Halit Kantekin , Atıf Koca
a
b
Department of Chemistry, Karadeniz Technical University, 61080, Trabzon-Turkey
Department of Chemical Engineering, Engineering Faculty, Marmara University, 34722
Göztepe, İstanbul-Turkey
*Corresponding author. Tel.: +90 462 377 25 89 fax: +90 462 325 31 96
E-mail address: halit@ktu.edu.tr (H. Kantekin)

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Abstract
In this study, the new tetra peripherally 4-(2-(benzo[d]thiazol-2-yl)phenoxy)-
substituted metal-free (4), zinc(II) (5), lead(II) (6), cobalt(II) (7) and copper(II) (8)
phthalocyanine derivatives, which are organo-soluble, have been synthesized for the first time
and their structures characterized by using electronic absorption, infrared spectroscopy,
nuclear magnetic resonance spectroscopy, elemental analysis and mass spectra. Voltammetric
characterization of the phthalocyanine derivatives (4-7) was performed with cyclic
voltammetry and square wave voltammetry. Cobalt phthalocyanine (7) gave metal based
electron transfer reactions in addition to the phthalocyanine ring based reduction and
oxidation reactions. Although lead phthalocyanine (6) illustrated reversible reduction process
during the voltammetric measurements, it was de-metallized and thus it turned back to the
metal free phthalocyanine during the in situ spectroelectrochemical measurements under the
applied potentials. Spectroelectrochemical measurements were performed to assign the redox
processes and spectroscopic responses of the electrogenerated species.
Keywords:
Benzothiazole;
Metallophthalocyanine;
Metal-free
phthalocyanine;
Electrochemistry; Demetallation.

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1. Introduction
Metal complexes of N -ligands, such as porphyrins and phthalocyanines, are widely
4
studied due to their numerous physical-chemical properties and the great variety of their
applications in many fields [1]. Both series of phthalocyanines and porphyrins (tetrapyrrole
macrocyles) are able to form several complexes with almost all the metals in Periodic Table
[
2] and it is known that at least seventy metal phthalocyanines have been prepared [3] thanks
to their ability. Their favorable properties, such as extraordinary thermal and chemical
stability, make them suitable as industrial pigments for a couple of decades [4].
Phthalocyanines, which are an important class of compounds use in inks, dyestuff for
textiles and colorant for metals and plastics [5], have been used other applications such as
liquid crystal displays [6, 7], optical applications [8, 9], electrochromism [10, 11], chemical
sensors [12, 13], semiconductors for organic field-effect transistors (OFETs) [2, 14] and
photodynamic therapy [15-17].
Photodynamic therapy (PDT) is a new technique that uses a photosensitizing agent and
a particular type of light [18]. Metallophthalocyanines which can be used as photosensitizing
agent for photodynamic therapy have received increasing attention since 1985 [19]. This
therapy results in a sequence of photochemical and photobiological processes that cause
irreversible photo damage to tumor tissues [20].
For all applications mentioned, the solubility of phthalocyanine derivatives plays a
consequential role. Metallophthalocyanines are unsoluble in aqueous solvent in the absence of
hydrophilic peripheral substituents but dissolve in strongly coordinating solvents like pyridine
[
21]. The bulky peripheral substitution on phthalocyanine core is used for enhancing the
solubility of phthalocyanine derivatives in most common organic solvents; whereas sulfo or
quaternary ammonium groups enhance solubility in aqueous media [22].

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Thiazoles, which are a class of organic compounds, contain three carbon atoms, one
nitrogen atom, and one sulfur atom. Among the pentaatomic heterocyclic rings, thiazole is
one of the most intensively investigated. Thiazoles and their derivatives exhibit a wide variety
of biological activities [23]. The number of annual publications dealing with thiazoles is
continuously growing, but there are very few articles about thiazole substituted
phthalocyanines in literature [24-26]. Because of this reason, in this work, the thiazole
substituted metal-free (H Pc) and metallophthalocyanines (MPcs) were synthesized.
2
MPcs are used in many electrochemical technologies, especially electrosensing [27-
30], electrochromic [31-33], and electrocatalytic [34-37] application due to the excellent
redox properties. Changing the central metal and types, number and position of substituents
alter molecule’s the electrochemical responses as well as the usage fields of the MPc
complexes [38-40].
Here, we report the synthesis and characterization of novel 4-(2-(benzo[d]thiazol-2-
yl)phenoxy-substituted H Pc (4), ZnPc (5), PbPc (6), CoPc (7) and CuPc (8) compounds. In
2
this paper we aimed to investigate the electrochemical properties and possible application
fields of the newly synthesized MPc complexes. Voltammetric characterizations of the
phthalocyanines (4-7) were performed with cyclic voltammetry and square wave voltammetry
for the first time. These organo-soluble phthalocyanines (4-8) have also been characterized by
1
13
using electronic absorption, FT-IR, H NMR, C NMR, elemental analysis and mass spectra.

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2
2
. Experimental
.1. Materials
All reagents and solvents were dried and purified as described in Perrin and Armarego
40]. 2-(benzo[d]thiazol-2-yl)phenol (1) was obtained from commercial supplier. 4-nitro
[
phthalonitrile (2) [41] was prepared according to the reported procedure. All other reagents
and solvents were reagent grade quality and were obtained from commercial suppliers.
2.2. Equipments
Infrared spectra were recorded on a Perkin-Elmer FT-IR spectrometer Frontier.
Elemental analyses were obtained from Costech ECS 4010 Spectrometer Elemental Analyzer
1
13
(
C, H, N). H NMR and C NMR spectra were recorded in CDCl3 solvent on a Varian
Mercury 200 MHz spectrometer (at Karadeniz Technical University, Turkey) and Varian
Mercury 300 MHz spectrometer (at Sakarya University, Turkey) using TMS as an internal
reference. Mass spectra were performed on a Brucker Microflex LT MALDI-TOF MS
spectrometer (at Gebze Institute of Technology, Turkey). Optical spectra in the UV/Vis
region were recorded with a Perkin Elmer Lambda 25 UV-Vis Spectrometer operating in the
range 200-800 nm with quartz cells at the room temperature. Melting points were measured
on an electrothermal melting point apparatus and were uncorrected.
All electrochemical measurements were carried out with Gamry Reference 600
potentiostat/galvanostat (at Marmara University, Turkey). An electrochemical cell with a
three-electrode configuration was utilized with a Pt disc working electrode (surface area:
2
0
.071 cm ), a Pt wire counter electrode and saturated calomel reference electrode (SCE).

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Electrochemical grade TBAP in extra pure DCM was employed as the supporting electrolyte
-3
at a concentration of 0.10 mol dm .
An Ocean Optics QE65000 diode array spectrophotometer was used for UV-Vis
absorption spectra and chromaticity diagram measurements (at Marmara University, Turkey).
In-situ spectroelectrochemical measurements were carried out by utilizing a three-electrode
configuration of thin-layer quartz spectroelectrochemical cell consisting a Pt tulle working
electrode, a Pt wire counter electrode, and a SCE reference electrode. The
spectroelectrochemical cell we used is a homemade cell. Three quartz necks were welded on a
quartz fluorescence cuvette which has 2 mm light path. Three quartz necks were used as
holder for the electrodes. 2 mm light path of the fluorescence cuvette supply a thin layer for
the electroactive species in it. In-situ electrocolorimetric measurements, under potentiostatic
control, were obtained using an Ocean Optics QE65000 diode array spectrophotometer at
color measurement mode by utilizing a three-electrode configuration of thin-layer quartz
spectroelectrochemical cell.
2
2
.3. Synthesis
.3.1. Preparation of 4-(2-(benzo[d]thiazol-2-yl)phenoxy)phthalonitrile (3)
A solution of 2-(benzo[d]thiazol-2-yl)phenol (1) (1 g, 4.4 mmol) and 4-nitro
o
phthalonitrile (0.76 g, 4.4 mmol) (2) in dry DMF (15 mL) was stirred at 50 C for 10 min
under a nitrogen atmosphere. And then, finely ground anhydrous K CO (2.43 g, 17.6 mmol)
2
3
was added portionwise over a period of 2 h with stirring at this temperature. After stirring for
o
1
20 h at 50 C, the reaction mixture was poured over crushed ice and the resulting white
precipitate was filtered off, washed with distilled water, and then dried in vacuo. Yield: 1.5 g

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o
(
97 %), m.p.: 177-179 C. Calc. for C H N OS: % C 71.37, % H 3.14, % N 11.89. Found: %
21 11 3
−
1
C 71.39, % H 3.19, % N 11.85. FT-IR νmax/cm : 3070 (Ar-H), 2234 (C≡N), 1601, 1561
1
(
C=N), 1485, 1251 (Ar-O-C), 1105, 955, 837, 759, 694 (C-S). H NMR (CDCl ) (
δ
: ppm):
3
8
7
1
.60 (ArH, 1H, d), 8.11 (Ar-H, 1H, d), 7.91 (ArH, 1H, d), 7.75 (ArH, 1H, d), 7.53-7.22 (ArH,
1
3
H, m). C NMR (CDCl ) (δ: ppm): 161.01, 152.68, 151.14, 135.79, 132.70, 131.30, 127.33,
3
26.79, 125.91, 123.65, 122.06, 121.87, 121.68, 121.43, 118.12, 115.44, 115.06, 109.92.
+
MALDI-TOF, m/z: Calc.: 353.40; Found: 353.12 [M] .
2.3.2. Preparation of metal-free phthalocyanine (4)
In dry n-pentanol (3 mL), compound 3 (0.3 g, 0.85 mmol) and three drops of 1,8-
o
diazabicyclo[5.4.0]undec-7-ene were stirred under reflux in a nitrogen atmosphere at 160 C
in a sealed glass tube for 24 h and degassed several times. Thereafter, the reaction mixture
was left to cool to the room temperature. With adding ethanol (10 mL), the green crude
product was precipitated and filtered off. After the refluxing with ethanol (40 mL) for 4 h, the
obtained green product was filtered off again and was successively washed several times with
hot ethanol, distilled water and diethyl ether in order to removing the unreacted organic
materials. After drying in vacuo, it was purified by column chromatography using
o
chloroform-methanol (93:7) solvent system as eluent. Yield: 110 mg (37 %), m.p.:>300 C
(
decomposition). Calc. for C H N O S : % C 71.27, % H 3.28, % N 11.87. Found: % C
84 46 12 4 4
−
1
7
1
8
1.33, % H 3.36, % N 11.89. FT-IR νmax/cm : 3287 (N-H), 3060 (Ar-H), 1610 (N-H, bend.),
1
577 (C=N), 1447, 1228 (Ar-O-C), 1089, 925, 752, 692 (C-S). H NMR (CDCl ) (
δ
: ppm):
3
.50 (ArH, 4H, m), 8.05 (ArH, 4H, m), 7.37-6.98 (ArH, 36H, m). UV/Vis (THF): λ, nm

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(log ε): 700 (5.20), 665 (5.16), 638 (4.81), 605 (4.68), 383 (4.78). MALDI-TOF, m/z: Calc.:
+
1
415.63; Found: 1415.57 [M] .
2.3.3. General procedures for metallophthalocyanine derivatives (5–8)
The mixture of compound 3 (0.3 g, 0.85 mmol), the related anhydrous metal salt
[
Zn(CH COO) (38 mg, 0.21 mmol) for compound 5 , PbO (47 mg, 0.21 mmol) for
3 2
compound 6, CoCl (27 mg, 0.21 mmol) for compound 7, CuCl (28 mg, 0.21 mmol) for
2
2
o
compound 8] and three drops of 1,8-diazabicyclo[5.4.0]undec-7-ene was heated at 160 C
with dry n-pentanol (3 mL) in a sealed tube, and stirred for 24 h. Later on , the reaction
mixture was left to cool into the room temperature. With adding ethanol (10 mL), the green
crude product was precipitated and filtered off. After the refluxing with ethanol (40 mL) for 4
h, the obtained green product was filtered off again and was successively washed several
times with hot ethanol, distilled water and diethyl ether in order to removing the unreacted
organic materials. After drying in vacuo, it was purified by column chromatography using
chloroform-methanol ((93:7) for compound 5, (91:9) for compound 6, (92:8) for compound 7
and (95:5) for compound 8, respectively) solvent system as eluent.
2.3.3.1. Preparation of zinc(II) phthalocyanine (5)
o
Yield: 83 mg (26 %), m.p.: >300 C (decomposition). Calc. for C H N O S Zn: % C 68.22,
8
4
44 12
4 4
−
1
%
H 3.00, % N 11.36. Found: % C 68.30, % H 3.08, % N 11.32. FT-IR νmax/cm : 3059 (Ar-
1
H), 1717, 1610 (C=N), 1448, 1316, 1229 (Ar-O-C), 1042, 941, 833, 746, 692 (C-S). H NMR
(
CDCl ) (δ: ppm): 8.92 (ArH, 8H, m), 7.93 (ArH, 8H, m), 7.36 (ArH, 28H, m). UV/Vis
3

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(THF): λ, nm (log ε): 673 (5.30), 607 (4.63), 356 (4.96), 328 (5.02). MALDI-TOF, m/z: Calc.:
+
1
479.01; Found: 1479.40 [M+] .
2.3.3.2. Preparation of lead(II) phthalocyanine (6)
o
Yield: 132 mg (38 %), m.p.:>300 C (decomposition). Calc. for C H N O S Pb: % C
84
44 12
4 4
−
1
6
2.25, % H 2.74, % N 10.37. Found: % C 62.28, % H 2.81, % N 10.35. FT-IR νmax/cm :
1
3
058 (Ar-H), 1604 (C=N), 1447, 1317, 1229 (Ar-O-C), 1077, 939, 824, 754, 692 (C-S). H
NMR (CDCl ) (
δ
: ppm): 9.10 (ArH, 6H, m), 8.59 (ArH, 4H, m), 7.43 (ArH, 34H, m). UV/Vis
3
(THF): λ, nm (log ε): 707 (5.29), 638 (4.60), 363 (4.87). MALDI-TOF, m/z: Calc.: 1620.82;
+
Found: 1619.96 [M-H] .
2.3.3.3. Preparation of cobalt(II) phthalocyanine (7)
o
Yield: 68 mg (22 %), m.p.: >300 C (decomposition). Calc. for C H CoN O S : % C 68.52,
8
4
44
12
4 4
−
1
%
H 3.01, % N 11.41. Found: % C 68.49, % H 3.09, % N 11.35. FT-IR νmax/cm : 3059 (Ar-
H), 1610 (C=N), 1448, 1230 (Ar-O-C), 1091, 1055, 955, 825, 751, 692 (C-S). UV/Vis (THF):
λ, nm (log ε): 667 (5.26), 601 (4.64), 354 (4.91), 313 (5.21). MALDI-TOF, m/z: Calc.:
+
1
472.55; Found: 1473.67 [M+H] .
2.3.3.4. Preparation of copper(II) phthalocyanine (8)
o
Yield: 150 mg (48 %), m.p.: >300 C (decomposition). Calc. for C H CuN O S : % C
8
4
44
12
4 4
−
1
6
3
8.30, % H 3.00, % N 11.38. Found: % C 68.37, % H 3.06, % N 11.43. FT-IR νmax/cm :
060 (Ar-H), 1610 (C=N), 1447, 1317, 1229 (Ar-O-C), 1090, 947, 876, 753, 691 (Ar-O-C).

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UV/Vis (THF): λ, nm (log ε): 675 (5.29), 608 (4.75), 348 (4.94). MALDI-TOF, m/z: Calc.:
+
1
477.16; Found: 1478.36 [M+H] .
3. Results and discussion
The general synthetic route for the synthesis of new dinitrile compound and
phthalocyanines is given in Scheme 1. The precursor material chosen for the synthesis of
tetra-substituted phthalocyanine derivatives (4-8) on the peripherally is 4-(2-(benzo[d]thiazol-
2
-yl)phenoxy)phthalonitrile (3). Compound 3 has been prepared by K CO catalyzed
2 3
nucleophilic substitution of the nitro group in 4-nitro phthalonitrile (2) with 2-
benzo[d]thiazol-2-yl)phenol (1) according to reported procedure [42]. 4-(2-(benzo[d]thiazol-
-yl)phenoxy-substituted H Pc (4) is prepared by cyclotetramerization of 4-(2-
(
2
2
(benzo[d]thiazol-2-yl)phenoxy)phthalonitrile
(3)
in
the
presence
of
1,8-
o
diazabicyclo[5.4.0]undec-7-ene, in dry n-pentanol at 160 C for 24 h with the yield of 37 %.
Tetra-substituted ZnPc (5), PbPc (6), CoPc (7) and CuPc (8) compounds are also obtained
by cyclotetramerization of 4-(2-(benzo[d]thiazol-2-yl)phenoxy)phthalonitrile (3) in the
presence of related metal salts (Zn(CH COO) , (PbO), CoCl and CuCl ) and two drops of
3
2
2
2
o
1
,8-diazabicyclo[5.4.0]undec-7-ene in dry n-pentanol 160 C for 24 h with the yields of 26,
8, 22 and 48 % (for compounds 5-8), respectively. All novel phthalocyanines were purified
3
on silica gel by column chromatography using chloroform: methanol [(93:7), (91:9), (92:8)
and (95:5)] solvent system as eluent.
Although phthalocyanine complexes have low solubility in most organic solvents,
adding the some substituents on the phthalocyanine core increases the solubility. All
synthesized phthalocyanine derivatives (4-8) exhibit excellent solubility in most organic
solvents (e.g. chloroform, dichloromethane, THF, DMSO and DMF). These organo-soluble

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phthalocyanines (4-8) have been characterized by several spectral methods for supporting the
formation of the molecules.
In FT-IR spectrum of compound 3, the characteristic C≡N stretch was observed at
-1
∼
2234 cm . However, the cyclotetramerization of the dinitrile derivative (3) to the H Pc(4)
2
and MPcs (5-8) was confirmed by the disappearance of the intense C≡N vibration at ∼ 2234
-
1
cm .
1
In the H NMR spectrum of compound 3 in deuterated CDCl , aromatic protons were
3
observed at δ: 8.60 (d), 8.11 (d), 7.91 (d), 7.75 (d) and 7.53-7.22 (m) (Fig. S1). For the tetra-
substituted H Pc (4), the resonances belonging to the aromatic protons were observed at δ:
2
8
.50 (m), 8.05 (m), 7.37-6.98 (m). The typical shielding of inner core protons belonging to the
H Pc (4), which are generally shown at the negative ppm region [43], were not observed
2
1
because of strong aggregation [44]. In the H NMR spectra of ZnPc (5) and PbPc (6), the
aromatic protons were observed at between δ: 8.92-7.36 ppm for ZnPc (5) and δ: 9.10-7.43
1
ppm for PbPc (6), respectively. Because of their paramagnetic nature, H NMR of the CoPc
(7) and CuPc (8) derivatives was precluded.
1
3
In the C NMR spectrum of compound 3, the characteristic peaks belonging to
dicyano carbon atoms were observed at δ: 115.44 and 115.06 ppm, as expected (Fig. S2).
In the mass spectra of compounds 3, the presence of molecular ion peak at m/z: 353.12
+
[
M] confirmed the purposed structure (Fig. S3). The molecular ion peaks which were
+
+
+
observed at m/z: 1415.57 [M] for H Pc (4), 1479.40 [M] for ZnPc (5), 1619.96 [M-H] for
2
+
+
PbPc (6), 1473.67 [M+H] for CoPc (7) and 1478.36 [M+H] for CuPc (8), supported the
desired structures (Fig. S3 and Fig. S4). In addition to these data, the elemental analysis of
those compounds was also determined.

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3.1. Electronic absorption spectra
Fig. 1 shows typical UV/Vis absorption spectra of H Pc (4), ZnPc (5), PbPc (6),
2
CoPc (7) and CuPc (8) derivatives in THF. Generally, phthalocyanines and their derivatives
exhibit UV/Vis spectra with two intense absorption regions around approximately 300-400
nm (B-band) and around 600-700 nm (Q-band). The Q-band is due to the transition from the
ground state of A symmetry to the first excited state which is of E symmetry. The splitting
1
g
u
of Q-band is because of the lifting of degeneracy of LUMO to a varying extent [45].
The absorption spectrum of H Pc (4) includes a splitting intense Q-band near at λmax:
2
700 and 665 nm with shoulders at λmax: 638 and 605 nm and the B-band at λmax: 383 nm
(
Table 1). In the UV/Vis spectrum of H Pc (4), the Q band splitting has been interpreted due
2
to the diagonally occupying two protons on the pyrrolic nitrogens reducing the molecular
symmetry from D to D [46]. For compound 5-8, the Q-bands were observed at λmax: 673,
4
h
2h
7
07, 667 and 675 nm with shoulders λmax: 607, 638, 601 and 608 nm, respectively. The B-
bands were observed at (356, 328), 363, 313 and 348 nm for compounds 5-8, respectively
Table 1). In absorption spectra, PbPc (6) was redshifted compared to H Pc (4) and MPcs (5,
(
2
7, 8). The large redshift was attributed to highly deformed phthalocyanine skeleton due to the
central metals which was not fitting into the cavity of phthalocyanine molecule. Namely,
deformation of phthalocyanine ligand results in the redshifting of the Q-band [45].
3.2. Voltammetric Measurements
Redox behaviors of the complexes were performed in DCM/TBAP electrolyte system
on a Pt working electrode with cyclic voltammetry (CV) and square wave voltammetry
SWV) to support the proposed structure of the complexes and to decide possible
(

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applications. All redox processes were analyzed and derived voltammetric parameters were
tabulated on Table 2.
Fig. 2 shows CV responses of H Pc (4). It displays two reversible reduction reactions
2
labeled as R (E = -0.62 V;∆E = 59 mV; I /I = 0.98) and R (E = -0.91 V;∆E = 60 mV;
1
1/2
p
pa pc
2
1/2
p
I /I = 0.96) and two oxidation couples labeled as O (E = 0.92 V;∆E = 65 mV; I /I =
pa pc
1
1/2
p
pa pc
0
.93) and O (E = 1.12 V; ∆E = 72 mV; I /I = 0.91). All electron transfer processes are
2 1/2 p pa pc
both electrochemically and chemically reversible with respect to ∆E and I /I values. SVWs
p
pa pc
of the complex clearly support these reversible characters of the processes, since these
couples show symmetric anodic and cathodic peaks with the same peak currents (Fig. 2b).
H Pc (4) has 1.54 V ∆E (separation between first anodic and first cathodic peak), which
2
1/2
directly expresses the HOMO-LUMO gap of the complex. When compared with the similar
complexes in the literature, redox couples shift to positive potentials due to the electron
releasing 4-(2-(benzo[d]thiazol-2-yl)phenoxy) groups. HOMO-LUMO gap of the complex is
in a great harmony with the metal free phthalocyanines in the literature [47-49].
As shown in Fig. 3, ZnPc (5) gives a reversible oxidation (O at 0.75 V) during the
1
anodic scans. However cathodic peaks are complicated with the aggregation of the complex.
First reduction process splits into two waves, R’ for aggregated species at -0.87 V and R for
1
1
-1
monomeric species at -1.01 V at 0.100 Vs scan rate. This reduction process is followed with
the second quasi-reversible reduction process R at -1.30 V (∆E = 130 mV; I /I = 0.75).
2
p
pa pc
When compared with the redox responses of H Pc (4), electron transfer processes of ZnPc
2
(5) shifts to the negative potentials. These potential differences are resulted from the effective
nuclear charge differences between the 2H and Zn centers of the Pc rings [47-52].
The radius of divalent lead ions (1.75 Å) in the core of PbPc is greater than the radius
of the inner core, so the metal ion does not fit inside the central cavity but it lies out of the
phthalocyanine plane [53-55]. Therefore, the complex shows a demetallization tendency in

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the redox reactions. Therefore, these compounds show anomalous redox behaviors together
with tuning the physicochemical properties of MPc [56, 57]. Fig. 4 shows the voltammetric
responses of PbPc (6). PbPc (6) gives very similar redox responses with those of H Pc (4). It
2
displays two reversible reduction reactions labeled as R (E = -0.61 V;∆E = 80 mV; I /I =
1
1/2
p
pa pc
0
.95) and R (E = -0.94 V;∆E = 90 mV; I /I = 0.90) and two oxidation couples labeled as
2 1/2 p pa pc
O (E = 0.83 V;∆E = 110 mV; I /I = 0.83) and O (E = 1.33 V;∆E = 85 mV; I /I =
1
1/2
p
pa pc
2
1/2
p
pa pc
0
.55). Although H Pc (4) gives completely reversible couples, redox reactions of PbPc (6)
2
have quasi-reversible peak characters. Especially O couple of PbPc (6) is chemically
2
irreversible. The reversibility of the complex was also checked with the SWV given in Fig.
4b. Peak current ratios and symmetry of the peaks of a redox couple were used to characterize
reversibility or irreversibility of a redox process. In our previous papers, we illustrated the
redox responses of PbPc complexes [58-61]. Although demetallation of the PbPc complexes
during the cathodic potential scans were observed, PbPc (6) studied here gives a stable redox
responses without a chemical reaction, which illustrate stabilization of the Pb center with the
effect of 4-(2-(benzo[d]thiazol-2-yl)phenoxy) substituents.
CoPc (7) has different voltammetric responses than those of H Pc (4), ZnPc (5) and
2
PbPc (6). Since while H Pc (4), ZnPc (5) and PbPc (6) represent only Pc based electron
2
transfer reactions, CoPc (7) gives a metal based reduction process in addition to the Pc based
electron transfer reactions. As shown in Fig. 5, an irreversible R at -0.05 V assigned to the
1
II -2
I
-2
reduction of monomeric CoPc (Co Pc /Co Pc ) and an irreversible R’ at -0.55 V assigned to
1
II -2
I
-2
the reduction of aggregated CoPc ([Co Pc ] / [Co Pc ] ). Redox responses of the complex
agg
agg
recorded at different concentration and at different scan rates indicate the aggregation of the
complex. At higher concentrations, the current of the peak assigned to the aggregated CoPc
II -2
I
-2
II
-
(
[Co Pc ] / [Co Pc ] increased more than those assigned to the monomeric CoPc (Co Pc
agg agg
2
I
-2
/
Co Pc ) species. These voltammetric behavior indicate presence of an equilibrium between

ACCEPTED MANUSCRIPT
II -2
[
Co Pc ] and monomeric CoPc. At faster scan rates the aggregation peak R’ at -0.55 V
agg 1
observed more clearly and this peak disappeared at the slow scan rates as shown in Fig. 5.
These behaviors support the aggregation phenomena of the complex. This metal based
reduction processes are followed with a quasi-reversible Pc ring based reduction process, R2
at -1.31 V. A Pc based oxidation reaction having reversible peak character is also recorded at
0.78 V during the anodic potential scans. Peak assignments and aggregation properties of the
complex were supported with the in situ spectroelectrochemical measurements given below.
Electrochemical behaviors of CoPc is in a good agreement with the similar CoPc complexes
reported in the literature [62-65], which support the proposed structure of the complex
synthesized here. CoPc complexes generally give a metal based reduction process at around 0
II
V due to the electron gaining to the empty d orbitals of Co center located between the
HOMO and LUMO orbitals of Pc ring in noncoordinating solvents like DCM. Separation of
around 1 V between the metal based and ring based reduction process is a characteristic
response of CoPc complexes.
3.3. Spectroelectrochemistry
Spectroelectrochemical studies were employed to confirm the assignments of the
redox couple recorded in the CVs and SWVs of the complexes. Fig. 6 represents in situ
recorded UV-Vis spectral changes and in situ recorded chromaticity diagram of H Pc (4)
2
under applied potentials of the electron transfer reactions. H Pc (4) gives a split Q band at
2
673 and 710 nm with the shoulders at 611 and 642 nm at 0.0 V applied potential. When -0.85
V was applied to the working electrode, the split Q band turn to a single band at 675 nm as a
result of increasing a sharp band. These spectral changes are characteristic changes for the
first reduction reaction of metal free phthalocyanines (Fig. 6a) [47-49, 66, 67]. During the

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second reduction reaction, while the Q band at 675 nm decreases, the region at around 500 nm
increases in intensity, which characterizes the reduction of the monoanionic form of H Pc
2
species (Fig. 6b). Fig. 6c illustrates the spectral changes of H Pc (4) during the first oxidation
2
reaction. The split Q bands decrease in intensity and the region at around 500 nm starts to
increases first of all. But then all bands decrease in intensity due to the decomposition of the
oxidized form of the complex. Color of the electrogenerated forms of the complex was
recorded with in situ chronocolorimetry, however a distinctive color change was not recorded
between the electrogenerated forms of the complex.
Spectroelectrochemical results of ZnPc (5) were consistent with the Pc ring based
reduction of the MPcs having redox inactive metal centers. However spectroelectrochemical
studies of PbPc (6) indicate different spectroscopic changes than the common ring based
redox processes due to the demetallization of the complexes. Fig. 7 and 8 illustrate the in situ
spectroelectrochemical and in situ electrocolorimetric results of PbPc (6) under the applied
potential of the redox processes. Under –0.75 V potential application, first of all, while the Q
band at 717 nm starts to decreases, a new band increases at 677 nm and a split Q band is
formed (Fig. 7a). The final spectrum in the Fig. 7a (blue spectrum) is a characteristic
spectrum for the metal-free phthalocyanine. Thus these spectral changes are easily assigned to
the demetallation of PbPc (6) and formation of H Pc (4). At the same potential application,
2
the band at 717 nm disappears, while the band at 677 nm increases in intensity. These spectral
changes are similar changes with the reduction of metal free phthalocyanine (Fig. 7b). Fig. 7c
illustrates the spectral changes under -1.30 V. These spectral changes are characteristic
changes for the ring based reduction of MPc complexes. While the Q band at 677 nm
decreases in intensity, a new band is recorded at 540 nm. Decreasing of the Q band without
shifting and observation of a new band between 500 and 600 nm characterize a Pc based
reduction process [52, 58-61, 68]. In our previous studies [58-61], we also indicated the

ACCEPTED MANUSCRIPT
demetallization of the PbPcs before or after the first reduction processes and during the
positive potential scans depending on the substituents. Fig. 8a represents the spectral changes
during the first oxidation reaction. While the Q band at 717 nm decreases in intensity, two
new bands are recorded at MLCT (Metal to Ligand Charge Transfer) regions (at 536 and 884
nm). These spectral changes are characteristic changes for the ring based oxidation of MPc
complexes. All bands decrease in intensity due to the decomposition as shown in Fig. 8b
during the second oxidation reaction. This decomposition reaction is recorded with the CV
and SWV measurements as shown in Fig. 4. The green color of the solution (point
x=0.3068, y=0.3605) changes to greenish yellow (point
x=0.352, y=0.3553) during the
x=0.3151, y=0.3164) after the
first oxidation process (Fig. 7d) and to the blue (point
second reduction reaction.
CoPc (7) has different voltammetric responses then the others, which also differs the
spectral changes recorded during the in situ spectroelectrochemical measurements. While
H Pc (4), ZnPc (5) and PbPc (6) complexes give spectral changes assigned to the Pc ring
2
based electron transfer processes, CoPc (7) illustrates spectral changes assigned to the metal
based reduction reaction during the first reduction reaction (Fig. 9). When -0.75 V was
applied, the Q band at 674 nm decreases in intensity and a small band is observed at 643 nm,
which assigned to the aggregation of the CoPc (7). And then while the Q band decreases and
a new Q band is recorded at 706 nm. At the same time a sharp band is recorded at 474 nm.
Totally while the Q band shifts from 674 nm to 706 nm, a new band is recorded at 474 nm
(Fig. 9a). Shifting of the Q band and observation of a new band between 450 and 500 nm
II -2
I
-2
characterizes the reduction of Co Pc to Co Pc species [69-74]. Fig. 9b illustrates the
spectral changes during the oxidation reaction. Decreasing of the Q band at 674 nm, and
observation of a new band at 505 nm characterize the Pc based oxidation of the complex.

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Chromaticity diagram in Fig. 9c represents the color of the electrogenerated species of the
complex.
4. Conclusions
In this study, the synthesis of novel peripherally tetra-4-(2-(benzo[d]thiazol-2-
yl)phenoxy)substituted H Pc (4), ZnPc (5), PbPc (6), CoPc (7) and CuPc (8) compounds
2
1
were described and characterized by using different spectroscopic techniques (e.g. FT-IR, H
1
3
NMR, C NMR, elemental analysis, mass spectroscopy, UV/Vis spectral data) for the first
time. In the UV-Vis spectra, while the H Pc (4) shows splitting Q band, the
2
metallophthalocyanines (5-8) exhibit single narrow Q bands as expected and support the
formation of phthalocyanine complexes in THF.
Electrochemical and spectroelectrochemical measurement support the proposed
structure of the complexes. H Pc (4) and ZnPc (5) illustrate the common Pc based electron
2
transfer reactions. Redox responses ZnPc (5) and CoPc (7) complicated generally with the
aggregation of the complexes. Although PbPc (6) gives clear well defined reversible
reduction and oxidation reactions during the CV and SWV measurements, it demetallized
during the in situ spectroelectrochemical reaction. CoPc (7) represents a metal based
reduction reaction, while the others give ring based reduction reactions. Redox richness of the
complexes illustrates their possible usage in different electrochemical technologies, such as
electrocatalytic, electrosensing and electrochromic fields. Especially different color of the
electrochemically generated redox species recorded during the in situ spectroelectrochemical
measurements indicates their suitability in the displaying technologies.

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Acknowledgement
This study was supported by the Research Fund of Karadeniz Technical University,
Project no: 2010.111.002.1 (Trabzon-Turkey). We thank to The Turkish Academy of
Sciences (TUBA) for their financial support.
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