Effects of peripheral and nonperipheral substitution to the spectroscopic, electrochemical and spectroelectrochemical properties of metallophthalocyanines

Article abstract of DOI:10.1016/j.electacta.2013.04.166

The syntheses, spectroscopic and electrochemical properties of metallo-phthalocyanine complexes, tetra- and octa-substituted with 3,4-(dimethoxyphenylthio) moieties at non-peripheral and peripheral positions were studied. These complexes were characterized by FT-IR, mass spectroscopy, electronic spectroscopy and electrochemical methods. 3,4-(Dimethoxyphenylthio) moieties increase the solubility of the complexes in various polar and nonpolar organic solvents and prevent the aggregation (in the same solvents) within a wide concentration range. Electronic absorption spectroscopy revealed that the presence of electron donating sulphur on synthesized complexes shift the Q-band of the complexes to the higher wavelengths. Redox active metal centers, Co ^II, Fe^II and Mn^IIIOAc into the phthalocyanine core extend the redox worthy of the complexes due to the reversible metal-based reduction and oxidation couples of the metal centers. In situ electrocolorimetric measurements of the complexes allow quantification of color coordinates of each electrogenerated anionic and cationic redox species. Electrochemical and in situ spectroelectrochemical analysis indicate that cobalt and manganese phthalocyanines catalyze the molecular oxygen in aprotic media.

Full text of DOI:10.1016/j.electacta.2013.04.166

Electrochimica Acta 106 (2013) 541–555
Contents lists available at SciVerse ScienceDirect
Electrochimica Acta
journal homepage: www.elsevier.com/locate/electacta
Effects of peripheral and nonperipheral substitution to the
spectroscopic, electrochemical and spectroelectrochemical properties
of metallophthalocyanines
Duygu Arıcana, Mürsel Arıcıb, Ahmet Lütfi Ug˘urc, Ali Erdog˘mus¸ d,∗, Atıf Kocaa,∗
a Department of Chemical Engineering, Engineering Faculty, Marmara University, 34722 Göztepe, Istanbul, Turkey
b Department of Chemistry, Faculty of Arts and Sciences, Eskis¸ehir Osmangazi University, 26480 Eskis¸ehir, Turkey
c C¸ anakkale 18 March University, Yenice Vocational School, Yenice, C¸ anakkale, Turkey
d Department of Chemistry, Yıldız Technical University, 34210 Esenler, Istanbul, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 5 March 2013
Received in revised form 26 April 2013
Accepted 27 April 2013
Available online 21 May 2013
The syntheses, spectroscopic and electrochemical properties of metallo-phthalocyanine complexes,
tetra- and octa-substituted with 3,4-(dimethoxyphenylthio) moieties at non-peripheral and peripheral
positions were studied. These complexes were characterized by FT-IR, mass spectroscopy, electronic
spectroscopy and electrochemical methods. 3,4-(Dimethoxyphenylthio) moieties increase the solubility
of the complexes in various polar and nonpolar organic solvents and prevent the aggregation (in the
same solvents) within a wide concentration range. Electronic absorption spectroscopy revealed that the
presence of electron donating sulphur on synthesized complexes shift the Q-band of the complexes to
the higher wavelengths. Redox active metal centers, CoII, FeII and MnIIIOAc into the phthalocyanine core
extend the redox worthy of the complexes due to the reversible metal-based reduction and oxidation
couples of the metal centers. In situ electrocolorimetric measurements of the complexes allow quantifi-
cation of color coordinates of each electrogenerated anionic and cationic redox species. Electrochemical
and in situ spectroelectrochemical analysis indicate that cobalt and manganese phthalocyanines catalyze
the molecular oxygen in aprotic media.
Keywords:
Thiol-substituted metallophthalocyanines
Electrochemistry
Spectroelectrochemistry
Oxygen reduction reaction
Chronocolorimetry
© 2013 Elsevier Ltd. All rights reserved.
1. Introduction
containing electroactive metal center (manganese, iron, etc.) have
been also studied due to their electrocatalytic properties [23–25].
Metallophthalocyanines (MPcs) complexes have attracted
attention due to their various applications such as chemical sen-
sors [1,2], liquid crystals [3], semiconductors [4], non-linear optics
and photodynamic therapy (PDT) [5–8]. Their fundamental physi-
cochemical properties, coductivity, solubility, redox activity, etc.,
which can be tuned by changing the metal and/or substituents
on the Pc ring are important for their application areas [9–12].
Substitution at non-peripheral positions gives rise to red shifting
of the Q-band of MPcs and reduces to aggregation according to
the substitution at the peripheral positions [13,14] and the pres-
ence of electron donating sulphur groups on Pc leads to the red
shifting of the Q-band to more longer wavelengths [13,14]. Metal-
lophthalocyanines substituted at peripheral and non-peripheral
positions with various moieties have different physicochemi-
cal, electrochemical, and photochemical properties [15–22]. MPcs
Thus we have performed the synthesis, characterization and appli-
cations of MPc having different substituents [26–30]. In order
to analyze the position and the number of the substituents
to the spectroscopic and electrochemical features of the com-
plexes, we aimed to synthesize three series of the complexes. In
our previous study, we synthesized and characterized the first
series (S1), metallophthalocyanine (metal: Mn, Co, Fe, Cu) sub-
stituted with 3,4-(dimethoxyphenylthio) at peripheral positions
[31]. In this work, as a sequel to the S1 complexes, new metal-
lophthalocyanines (metal: Mn, Co, Fe, Cu) tetra substituted with
3,4-(dimethoxyphenylthio) at nonperipheral positions (S2) and
octa substituted with 3,4-(dimethoxyphenylthio) at peripheral
positions (S3) were synthesized. Then these complexes were char-
acterized spectroscopically and electrochemically to investigate
the effects of position and number of substituents to the spectro-
scopic and electrochemical behaviors of the complexes (Scheme 1).
We have also investigate interaction of MPcs with molecular
oxygen in aprotic media with voltammetric and in situ spectro-
electrochemical measurements. These studies will be a preliminary
stage for applications of these complexes due to their possible
∗
Corresponding authors. Tel.: +90 2163480292; fax: +90 2163480292.
E-mail addresses: erdogmusali@hotmail.com (A. Erdog˘mus¸ ),
akoca@marmara.edu.tr (A. Koca).
0013-4686/$ – see front matter © 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.electacta.2013.04.166

542
D. Arıcan et al. / Electrochimica Acta 106 (2013) 541–555
Scheme 1. Synthetic route of 3,4-(dimethoxyphenylthio)phthalonitrile (1) and 4,5-bis[3,4-(dimethoxyphenylthio)]phthalonitrile (2) and their metallophthalocyanines
(M = Mn(III)Ac, Fe(III)Ac, Co(II) Cu(II)) (i) manganese (II) acetate or anhydrous ferrous acetate or anhydrous cobalt (II) chloride or copper acetate, 1-pentanol, DBU, 24 h.
source. 1H NMR spectra were carried out on a 104 Varian 500 MHz
spectrometer in deuterated chloroform. Elemental analyses were
obtained with a Thermo Flash EA 105 1112 Series. GC–MS spectra
were acquired on an Agilent Technologies including 6890N net-
work GC system and 5973 inert Mass selective detector.
usages as electrochemical sensors, cathode active material in fuel
cell technology, as electrocatalysts in the non-aqueous metal–air
batteries and productions of superoxide from molecular oxygen in
the aprotic solvents [32–34].
2. Experimental
2.3. Synthesis
2.1. Materials
The following chemicals were purchased from Merck; N,Nꢀ-
dimethylformamide (DMF), chloroform (CHCl3), tetrahydrofuran
(THF), methanol (MeOH), dichloromethane (DCM), 1-pentanol,
n-hexane, 4-nitrophthalonitrile, 4,5-dichlorophthalonitrile and
3,4-dimethoxythiophenol were purchased from Sigma Aldrich.
1,8-Diazabicyclo[5.4.0] undec-7-ene (DBU), tetrabutyl ammonium
perclorate (TBAP), potassium carbonate, manganese (II) acetate and
cobalt (II) chloride, iron (II) acetate and copper acetate were pur-
chased from Aldrich. Column chromatography was performed on
silica gel 60 (0.04–0.063).
2.3.1. 3,4-(Dimethoxyphenylthio) phthalonitrile (1)
3-nitrophthalonitrile
(0.99 g,
5.90 mmol)
was
dis-
solved in 15.0 ml DMF under argon atmosphere and
3,4-dimethoxythiophenol (1.00 g, 5.90 mmol) was added at
room temperature. After stirring for 30 min at room temperature,
finely ground anhydrous potassium carbonate (3.94 g, 28.4 mmol)
was added portion wise for over 1 h and the reaction mixture
was stirred at room temperature for 24 h. Then the mixture was
poured into 100.0 ml ice water, and the precipitate was filtered
off, washed with water and methanol, and then dried. The crude
product was recrystallized from ethanol. Finally the pure product
was dried in vacuum. Yield: 3.12 g (90%). FT-IR (cm−1) (KBr): 3070,
3004 (Ar CH), 2960, 2934, 2840 (CH), 2230 (C N), 1583, 1567,
2.2. Equipment
1505 (C C), 1461, 1439, 1417, 1401, 1328, 1259 (C
O
C), 765
C). 1H NMR (CDCl3): ı = 7.65–7.06 (6H, m, Ar H), 3.92 (3H, s,
H), 3.82 (3H, s, C H). Calcd for C16H12N2O2S: C, 64.90; H, 4.10;
FT-IR spectra were recorded on a Perkin Elmer Spectrum One
Spectrometer using KBr disk. Absorption spectra were recorded
on a Shimadzu 2001 UV spectrophotometer. The mass spectra
were recorded on a Bruker Daltonics (Bremen, Germany) MicroTOF
mass spectrometer equipped with an electronspray ionization (ESI)
(C
C
S
N, 9.45; S, 10.80; Found: C, 64.85; H, 4.14; N, 9.52; S, 10.85. MS
(GC–MS) m/z: Calc.: 296.35, Found: 296 [M]+.

D. Arıcan et al. / Electrochimica Acta 106 (2013) 541–555
543
2.3.2. 4,5-Bis[3,4-(dimethoxyphenylthio)]-phthalonitrile (2)
UV–vis (DMSO): ꢀmax nm (log ε) 326 (4.93), 631 (4.56), 695 (5.07).
4,5-Dichlorophthalonitrile (1.74 g, 8.85 mmol) was dis-
solved in 30.0 ml DMF under argon atmosphere and
3,4-dimethoxythiophenol (3.00 g, 17.7 mmol) was added at
room temperature. After stirring for 30 min at room temperature,
finely ground anhydrous potassium carbonate (3.45 g, 25.0 mmol)
was added in portions for over 1 h and the reaction mixture was
stirred at 40 ◦C for 48 h. Then the mixture was poured into 100.0 ml
ice water, and the precipitate was filtered off, washed with water
and methanol, and then dried. The crude product was recrystal-
lized from ethanol:chloroform (20:1, v/v). Finally the pure product
was dried in vacuum. Yield: 1.46 g (72%). FT-IR (cm−1) (KBr): 3079
(Ar CH), 2965, 2837 (CH), 2227 (C N), 1583, 1502 (C C), 1461,
FT-IR cm−1 (KBr): 3063 (Ar CH), 2932, 2833 (aliphatic CH), 1582
(C C), 1501, 1460, 1460, 1438, 1394, 1312, 1250 (C
O C), 877, 762,
742 (C C) Calcd for C64H48N8O8S4Co: C, 61.78; H, 3.89; N, 9.01;
S
S, 10.31%. Found: C, 61.96; H, 3.80; N, 9.12; S, 10.17%. MS (ESI-MS)
m/z: Calc.: 1244.31; Found: 1244.39 [M]+.
2.3.6. 2(3),9(10),16(17),23(24)-Tetrakis-[3,4
(dimethoxyphenylthio)]phthalocyaninato copper (II) (6)
The procedure for the synthesis of 6 was similar to that used
for 3, except anhydrous copper (II) acetate (0.060 g, 0.33 mmol)
was used instead of manganese (II) acetate. The crude product
was precipitated, collected by filtration and washed with hot
hexane and methanol. Compound 6 was purified with column
chromatography using a mixture of CHCl3:THF (10:1 by volume)
as eluent. Yield = 37 mg (17.8%). UV–vis (DMSO): ꢀmax nm (log ε)
331 (4.81), 435 (4.21), 644 (4.60), 718 (5.28). FT-IR cm−1 (KBr):
3058 (Ar CH), 2931, 2833 (aliphatic CH), 1582 (C C), 1498, 1459,
1397, 1347, 1321, 1253, 1175, 1133 (C
O C), 1.19, 869, 806, 762
(C
S
C). 1H NMR (CDCl3): ı = 7.59 (1H, m, Ar H), 7.33–7.27 (2H,
m, Ar H), 7.18–7.16 (1H, m, Ar H), 7.08–6.98 (2H, m, Ar H), 3.97
(3H, s, C H), 3.89 (3H, s, C H). Calc. for C24H20N2O4S: C, 62.05; H,
4.34; N, 6.03; S, 13.80% Found. C, 64.96; H, 4.12; N, 9.39; S, 10.83%.
MS (ESI-MS) m/z: Calc.: 464.56, Found:464.27 [M]+.
1437, 1389, 1311, 1250 (C
O C), 876, 759, 741 (C S C). Calcd for
2.3.3. 1(4),10(13),19(22),28(31)-Tetrakis-[3,4-
(dimethoxyphenylthio)]phthalocyaninato manganese (III) acetate
(3)
C64H48N8O8S4Cu: C, 61.55; H, 3.87; N, 8.97; S, 10.27%. Found: C,
61.69; H, 3.92; N, 8.89; S, 10.39%. MS (ESI-MS) m/z: Calc.: 1248.93;
Found: 1248.87 [M]+.
Compound
1
(0.20 g, 0.67 mmol), Mn(OAc)2 (0.058 g,
0.33 mmol) and 2.0 ml of dry pentanol were placed in a standard
Schlenk tube in the presence of 1,8-diazabicyclo[5.4.0] undec-7-
ene (DBU) (0.115 ml, 0.770 mmol) under argon atmosphere and
the mixture was refluxed for 16 h at 160 ◦C. After cooling to room
temperature, the reaction mixture was precipitated by adding it
drop-wise into n-hexane. The crude product was precipitated,
collected by filtration and washed with hot hexane. The crude
product was further purified by chromatography over a silica gel
column using a mixture of CHCl3:MetOH (20:1 by volume) as
eluents. Yield = 48 mg (22%). UV–vis (DMSO): ꢀmax nm (log ε) 359
(4.70), 517 (4.24), 703 (4.41), 787 (5.07). FT-IR cm−1 (KBr): 3066,
3003 (Ar CH), 2930, 2833 (aliphatic CH), 1706 (C O), 1583 (C C),
2.3.7. Manganese (III)acetate (7), iron (III)acetate (8), cobalt (9),
and copper (10)
octakis-[3,4-(dimethoxyphenylthio)]phthalocyanine
4,5-Bis[3,4-(dimethoxyphenylthio)]phthalonitrile (2) (0.20 g,
0.43 mmol) in 1-pentanol (2.0 ml) was refluxed under an argon
atmosphere and manganese (II) acetate (0.036 g, 0.21 mmol) or
anhydrous ferrous acetate (0.036 g, 0.21 mmol) or cobalt (II) chlo-
ride (0.027 g, 0.21 mmol) or copper (II) acetate (0.038 g, 0.21 mmol)
was added. After the addition of DBU (0.115 ml, 0.86 mmol), the
reaction was continued for 18 h. Thereafter, the reaction mixture
was allowed to cool to room temperature. The reaction mixture
was precipitated by adding it drop wise into n-hexane. The crude
product was precipitated, collected by filtration and washed with
hot hexane.
1501, 1439, 1367, 1319, 1252 (C
O C), 1022, 939 (Mn O), 876,
803, 764, 740 (C C). Calcd for C64H48N8O8S4MnOAc: C, 61.01;
S
H, 3.96; N, 8.62; S, 9.87%. Found: C, 61.52; H, 4.06; N, 8.90; S, 10.08.
MS (ESI-MS) m/z: Calc.: 1240.3; Found: 1243.56 [M−Ac+3H]+.
Yield of compound 7 = 43 mg (20.3%). UV–vis (DMSO): ꢀmax nm
(log ε) 375 (4.71), 498 (4.47), 682 (4.39), 762 (4.97). FT-IR cm−1
(KBr): 3062, 2996 (Ar CH), 2928.6, 2833 (aliphatic CH), 1732
(C O), 1582 (C C), 1499, 1460, 1437, 1408, 1370, 1323, 1250.7,
2.3.4. 1(4),10(13),19(22),28(31)-Tetrakis-[3,4-
(dimethoxyphenylthio)]phthalocyaninato iron (III)acetate
(4)
1227.7 (C
O C), 874, 849, 802, 779, 761.7, 744 (C S C), 10 219,
The procedure for the synthesis of 4 was similar to that used
for 3, except anhydrous ferrous acetate (0.057 g, 0.33 mmol) was
used instead of manganese (II) acetate. The crude product was pre-
cipitated, collected by filtration and washed with hot hexane and
methanol. Compound 4 was purified with column chromatography
using CHCl3 as eluent. Yield = 60 mg (28.6%). UV–vis (DMSO): ꢀmax
nm (log ε) 332 (4.83), 624 (4.48), 689 (4.77). FT-IR cm−1 (KBr): 3059
(Ar CH), 2930, 2834 (aliphatic CH), 1582 (C C), 1499, 1460, 1460,
953 (Mn O). Calcd for C98H83N8O18S8MnOAc: C, 59.68; H, 4.24;
N, 5.68; S, 13.01%. C, 60.45; H, 4.31; N, 5.88; S, 12.21% Found: MS
(ESI-MS) m/z: Calc.: 1913.16 Found: 1912.9 [M−Ac+H]+.
Yield of compound 8 = 102 mg (49.5%). UV–vis (DMSO): ꢀmax nm
(log ε) 337 (4.91), 659 (4.75). FT-IR cm−1 (KBr): 3072, 2999 (Ar CH),
2930, 2833 (aliphatic CH), 1582.5 (C C), 1499, 1461, 1437, 1405,
1370, 1321, 1252, 1227 (C
O C), 874, 840, 802, 777, 763, 745
(C C). Calcd for C98H83N8O18S8Fe: C, 59.65; H, 4.24; N, 5.68;
S
1437, 1390, 1312, 1249 (C
O
C), 877, 759, 738 (C
S
C). Calcd for
S, 13.00%. C, 60.25; H, 4.32; N, 5.98; S, 12.84%. Found:. MS (ESI-MS)
C64H48N8O8S4FeOAc: C, 60.96; H, 3.95; N, 8.62; S, 9.86%. Found: C,
m/z: Calc.: 1914.07; Found: 1915 [M]+.
61.23; H, 3.96; N, 8.95; S, 10.12%. MS (ESI-MS) m/z: Calc.:1241.22;
Yield of compound 9 = 42.2 mg (20.3%). UV–vis (DMSO): ꢀmax
nm (log ε) 336 (4.88), 620 (4.47), 697 (4.9). FT-IR cm−1 (KBr): 3070,
2996 (Ar CH), 2930, 2833 (aliphatic CH), 1582 (C C), 1499, 1461,
Found: 1241.77 [M−Ac]+.
2.3.5. 2(3),9(10),16(17),23(24)-Tetrakis-[3,4-
1437, 1406, 1369, 1320, 1250, 1227 (C
O C), 874, 840, 802, 777,
(dimethoxyphenylthio)]phthalocyaninato cobalt (II)
(5)
762, 745 (C C). Calcd for C96H80N8O16S8Co: C, 60.14; H, 4.21;
S
N, 5.84; S, 13.38%. C, 61.66; H, 4.11; N, 5.96; S, 13.62%. Found:. MS
The synthesis of 5 was as outlined for 3, except that cobalt
(II) chloride (0.043 g, 0.33 mmol) was employed instead of man-
ganese (II) acetate. The crude product was precipitated, collected
by filtration and washed with hot hexane and methanol. Com-
pound 5 was purified with column chromatography using a mixture
of CHCl3:THF (25:1 by volume) as eluent. Yield = 99 mg (47.6%).
(ESI-MS) m/z: Calc.: 1917.16; Found: 1917.8 [M]+.
Yield of compound 10 = 38.6 mg (20.3%). UV–vis (DMSO): ␭
max
nm (log ε) 332 (4.83), 624 (4.48), 689 (4.77). FT-IR cm−1 (KBr): 3069,
2996 (Ar CH), 2930, 2833 (aliphatic CH), 1582 (C C), 1499, 1461,
1437, 1405, 1370, 1319.5, 1250, 1227 (C
O C), 874, 840, 802, 777,
761, 745 (C C). Calcd for C96H80N8O16S8Cu: C, 60.00; H, 4.20;
S

544
D. Arıcan et al. / Electrochimica Acta 106 (2013) 541–555
Fig. 1. UV–vis spectra of compound 3 (a) and 7 (b).
N, 5.83; S, 13.35%. C, 61.04; H, 4.32; N, 5.63; S, 12.96%. Found:. MS
consistent with the predicted structures as shown in Section 2. For
compounds 1 and 2, the characteristic vibrations corresponding
to C N were observed at 2231 cm−1 and 2227 cm−1 in the FT-IR
spectrum, respectively. Aromatic C H and aliphatic C H vibra-
tions occurred at 3078 cm−1 and between 2961 and 2834 cm−1
for 1 and at 3079 cm−1 and between 2965 and 2837 cm−1 for
(ESI-MS) m/z: Calc.: 1921.77; Found: 1922.68 [M]+.
2.4. Electrochemical and spectroelectrochemical studies
Cyclic voltammetry (CV) and square wave voltammetry (SWV)
measurements were carried out with Gamry Reference 600 poten-
tiostat/galvanostat. A three-electrode configuration was used with
a Pt disk working electrode (surface area: 0.071 cm2), a Pt wire
counter electrode and saturated calomel reference electrode (SCE).
Electrochemical grade TBAP in extra pure DCM and DMSO was
employed as the supporting electrolyte at a concentration of
0.10 mol dm−3. Oxygen interaction experiments were performed
according to the procedure given in the literature [34]. UV–vis
absorption spectra and chromaticity diagrams were measured
by an Ocean Optics QE65000 diode array spectrophotometer as
detailed in the paper published [26].
2, respectively. The ether (C
O C) and the thioether (C S C)
vibrations for compound 1 and 2 were observed at 1023 cm−1
and 729 cm−1, and at 1253 cm−1 and 762 cm−1, respectively. The
sharp peak for the C N vibration at 2231 cm−1 and 2227 cm−1
disappeared after conversion of the dinitrile derivatives 1 and 2
into metallophthalocyanines 3–10. In the IR spectra of the MPcs,
weak bands are observed above 3000 cm−1 due to aromatic C
H
stretching. The IR absorption bands of the complexes between
2950 and 2820 cm−1 are due to aliphatic C H stretching vibrations.
In all complexes, the characteristic vibrations corresponding to
thioether groups (C
S C) were observed at 740 (for 3), 739 (for
4), 742 (for 5), 741 (for 6), 744 (for 7), 745 (for 8), 745 (for 9), 745
(for 10). For manganese and iron complexes, the absorption picks
observed at between at 1729 and 1706 cm−1 are due asymmetric
carboxyl group of acetate and aliphatic C H group of acetate is
observed at 1834 and 2906 cm−1, which proof presence of axial
acetate aions on the metal center of manganese (3 and 7) and iron
3. Results and discussion
3.1. Synthesis and characterization
The procedure for the synthesis of compound 1 was simi-
lar to that used for Ref. [35], except 3-nitrophthalonitrile was
used instead of 4-nitrophthalonitrile. Compound 2 was prepared
from 4,5-dichloro-1,2-dicyanobenzene by displacement of the two
chloro groups with the SH function of the 3,4-dimethoxythiophenol
at 40 ◦C in dry DMF under argon atmosphere for 48 h. Scheme 1
shows the synthetic route involved in the formation of the
complexes 3–10. The MPc complexes were formed by cyclote-
tramerization of compound 1 and 2 in the presence of the desired
metal salt; Mn(CH3COO)2 (for 3 and 7), Fe(CH3COO)2 (for 4 and 8),
CoCl2 for (5 and 9) and Cu(CH3COO)2 for (6 and 10). Purification of
these complexes was achieved by column chromatography. Com-
pounds 3–9 were soluble in various organic solvents such as THF,
CHCl3, DMF, and DMSO while compound 10 was only soluble in
CHCl3 and DMSO.
(4 and 8) complexes (Fig. SM1). Moreover, elemental analyses
2
results show that theoretic calculations including acetate groups
are good agreement with experimental results.
The best indications for phthalocyanine complexes are given
by their UV–vis spectra in solution. The ground state electronic
absorption spectra of 3 and 7 are given in Fig. 1 as examples. The
UV–vis absorption spectra of the complexes 3–10 in DMSO illus-
trated the intense Q bands at 787, 689, 695, 718, 762, 659, 697, and
702 nm, respectively. The Q band absorptions of the complexes are
shifted to the longer wavelength as a result of the electron-donating
thioether substituents on the peripheral positions with respect
to similar complexes. Moreover, the absorption bands observed
at 505 nm for 3 and 506 nm for 7 are usually associated with
metal to ligand charge transfers in MnPcs [7,36]. In this study, the
aggregation behaviors of metallophthalocyanines (3–10) were also
investigated at different concentrations in DMSO. Aggregation is
The compounds were characterized by FTIR, UV/Vis and
Mass spectroscopies, as well as elemental analysis, which were

D. Arıcan et al. / Electrochimica Acta 106 (2013) 541–555
545
Table 1
Voltammetric data of the complexes. All voltammetric data were given versus SCE.
d
Complex
Ring oxidations
MIII/MII
MII/MI
Ring reductions
ꢁE1/2
a
CuPc (6)
E1/2
1.21e
80
0.75
0.83 (0.53)
67
0.72
–
–
–
–
–
–
−0.86
58
0.99
−1.22
61
0.94
1.36
1.39
1.07
0.99
1.08
0.95
0.80
0.84
0.75
b
ꢁEp (mV)
c
(in DCM)
Ip,a/Ip,c
a
CuPc (6)
E1/2
0.77 (0.50)
68
0.89
–
–
–
–
–
–
−0.89
58
0.95
−1.24
59
0.92
b
ꢁEp (mV)
c
(in DMSO)
Ip,a/Ip,c
a
MnPc (3)
E1/2
1.38
–
–
0.83
60
1.0
−0.24
62
0.97
−1.03 (−1.11) −1.49
92 110
0.85 0.61
–
–
–
b
ꢁEp (mV)
c
(in DCM)
Ip,a/Ip,c
a
MnPc (3)
E1/2
–
–
–
0.70e
–
–
−0.29
59
0.95
−0.88
61
0.98
−1.58
80
0.82
–
–
–
b
ꢁEp (mV)
c
(in DMSO)
Ip,a/Ip,c
a
MnPc (7)
E1/2
1.37e
–
–
1.09
67
0.87
0.01
120
0.90
−0.80
130
0.82
−1.20
180
0.74
–
–
–
b
ꢁEp (mV)
c
(in DCM)
Ip,a/Ip,c
a
CoPc (4)
E1/2
–
–
–
0.63
75
0.78
0.93
79
0.89
−0.32
72
0.95
−1.49
100
0.78
–
–
–
b
ꢁEp (mV)
c
(in DCM)
Ip,a/Ip,c
a
CoPc (4)
E1/2
–
–
–
1.00e
–
–
0.28
65
0.96
−0.52
100
0.94
−1.48
72
0.86
–
–
–
b
ꢁEp (mV)
c
(in DMSO)
Ip,a/Ip,c
a
FePc (5)
E1/2
1.04
95
0.92
0.54
140
0.95
−0.30
62
0.25
−0.63
136
0.92
−1.20
92
0.65
−1.61
b
ꢁEp (mV)
–
–
c
(in DCM)
Ip,a/Ip,c
a
FePc (5)
E1/2
0.80
–
–
0.32
62
0.91
−0.43
61
0.35
−0.85
62
0.96
−1.28
70
0.92
−1.61
223
0.71
b
ꢁEp (mV)
c
(in DMSO)
Ip,a/Ip,c
a
E1/2 values ((Epa + Epc)/2 were given versus SCE) at 0.100 V s−1 scan rate.
b
c
ꢁEp = Epa − Epc
.
Ip,a/Ip,c for reduction, Ip,c/Ip,a for oxidation processes.
ꢁE1/2 = E1/2 (first oxidation) − E1/2 (first reduction).
Recorded with SWV.
d
e
usually depicted as a coplanar association of rings progressing from
monomer to dimer and higher order complexes [13]. As the concen-
tration is increased, the intensity of absorption of the Q band also
increases and there are no new bands (normally blue shifted) due
to the aggregated species (Fig. 1). Lambert–Beer law was obeyed
for the complexes in DMSO in the concentrations ranging from
2 × 10−6 to 12 × 10−6 mol dm−3 [13].
literature. Presence of [3,4-dimetoxyphenylthio] groups at nonpe-
ripheral position (3–6; S2) increases the effect of electron releasing
ability of the substituents on the Pc rings, thus redox processes of
the S2 complexes shift to the negative potentials when compared
with the S1 complexes [31]. Differently, the redox potentials of the
S3 complexes (7–10) shift to the positive potentials with respect to
those of the S2 (3–6) and S1 complexes (Table 1) [31].
The mass spectra of 3–10 are in agreement with the proposed
structures (Fig. SM2 for 6(a) and 10(b) as examples). The molecular
ion peaks were observed at m/z 1243.56 M−Ac+3H for 3, 1241.77 for
4, 1244.39 for 5, 1248.87 for 6, 1912.9 for 7, 1915 for 8, 1917.8 for 9
and 1922.68 for 10 ion peak, respectively. Elemental analysis results
were also consistent with the proposed structures of all synthesized
phthalonitrile and phthalocyanine compounds 1–5.
Only CuPcs (6 in S2 series and 10 in S3 series) among the com-
plexes studied here have redox inactive metal centers. Thus redox
analysis of CuPc (6) was firstly represented to distinguish general
properties of the Pc based redox processes. Fig. 2 illustrates the CV
and SWV responses of CuPc (6) in DCM/TBAP electrolyte system.
CuPc (6) gives two reversible and diffusion controlled reduction
(Red1 at −0.22 V and Red2 at −1.00 V) and two oxidation cou-
ples (Oxd1 at 0.83 V and Oxd2 at 1.23 V). SWVs clearly show the
chemical and electrochemical reversibility of the redox processes
(Fig. 2b). In our system, ꢁEp’s were changed from 60 to 110 mV for
ferrocene with increasing scan rates from 0.010 to 1.00 V s−1. When
compared with the responses of ferrocene (ꢁEp’s are between 60
and 110 mV with increasing scan rates from 0.010 to 1.00 V s−1),
ꢁEp of the reduction reactions of CuPc (6) are in electrochemical
reversibility range. Both of the reduction processes are purely diffu-
sion controlled, since Ip,a/Ip,c ratio of the electron transfer reactions
are unity at all scan rates. However, oxidation processes are not
chemically reversible with respect to the Ip,a/Ip,c ratios. As shown
in the figure, the first reduction process split into two waves (Oxd1
and Oxda1gg). Analysis of these waves as a function of scan rate
3.2. Voltammetric analyses
To decide suitable usage of the complexes in various elec-
trochemical technologies, redox behaviors of the complexes
were examined with CV and SWV measurements in DCM and
DMSO/TBAP electrolyte system on a Pt working electrode. Table 1
lists the fundamental redox parameters of the complexes, which
are assignments of the redox couples, half-wave peak potentials
(E1/2), ratio of anodic to cathodic peak currents (Ip,a/Ip,c), peak to
peak potential separations (ꢁEp), and difference between the first
oxidation and reduction processes (ꢁE1/2). When compared with
the similar complexes in the literature, redox processes of the
complexes studied here generally shift to the negative potentials
due to the electron releasing ability of [3,4-dimetoxyphenylthio]
groups [12,31,37–41]with respect to the similar complexes in the
and concentration indicate that the first wave (Oxda1gg) is due to
the aggregation of the complex. These data indicate that there
is equilibrium between aggregated and monomeric CuPc species.

546
D. Arıcan et al. / Electrochimica Acta 106 (2013) 541–555
Fig. 3. (a) CVs of MnPc (3) at various scan rates on
in DCM/TBAP and (b) SWV of MnPc (3) recorded with SWV parameters: step
size = 5 mV; pulse size = 100 mV; frequency = 25 Hz.
a Pt working electrode
Fig. 2. (a) CVs of CuPc (6) at various scan rates on a Pt working electrode in
DCM/TBAPand (b) SWV of CuPc(6) recordedwith SWV parameters:step size = 5 mV;
pulse size = 100 mV; frequency = 25 Hz.
Increasing the scan rate and concentration of CuPc (6) shift the
equilibrium to the aggregated species side. Effects of the vertex
potential to the peak characters and to support the aggregation
process are also analyzed (supplementary materials: Fig. SM3).
As shown in this figure, reversibility of Red1 and Red2 processes
does not change when the cathodic vertex potential of CV changes.
However, in the anodic side, when the vertex potential passes the
Oxd2 process, chemical reversibility of Oxd1 and Oxdagg processes
decreases. These data indicate presence of a chemical 1reaction suc-
ceeding the Oxd1 process. Both anodic and cathodic potential scan
was also performed to analyze effect of this chemical reaction. As
shown in Fig. SM3b, cathodic potentials were scanned just after the
anodic potential scan without stopping. During this process, while
this chemical reaction affected the oxidation processes, oxidation
reactions and the chemical reaction succeeding the oxidation reac-
tions did not affect the CV responses of the reduction reactions.
Electrochemical responses of CuPc (6) recorded in DMSO/TBAP
were given in Fig. SM4 for comparison with those in DCM discussed
above. CuPc (6) generally illustrate similar reduction reaction in
both solvents with small potential shifts.
Among the complexes, it is well documented in the literature
that Mn(III), Fe(III), and Co(II) metal centers of MPc complexes are
redox active and can give electron transfer reactions in addition to
the Pc based electron transfer processes. Thus, presence of these
redox active metals in the core of Pc increases possible techno-
logical application areas of the complexes due to the increasing
redox richness of Pc ring. Thus detailed electrochemical analyses
of these complexes are important to decide possible application
fields of the complexes. In this respect, electrochemical responses
of MnPc, FePc and CoPc complexes were performed in solution and
the analysis results are tabulated in Table 1. Fig. 3 illustrates the CV
and SWV responses of MnPc (3) in DCM/TBAP electrolyte system.
MnPc (3) displays three reduction and two oxidation processes
(Fig. 3a). SWVs clearly show the chemical and electrochemical
reversibility of the redox processes (Fig. 3b). When compared
with the responses of ferrocene, ꢁEp values of all processes of
MnPc (3) recorded with CV measurements 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. The first reduction and first
oxidation processes are purely diffusion controlled and chemically
reversible. Moreover, reversibility of these couples can be con-
cluded with respect to symmetry and peak current ratios of the
waves recorded during the forward and reverse SWV scans (Fig. 3b)
[42]. However, Red2 process split into two waves. Concentration
and scan rate changes indicate that this splitting is not due to the
aggregation of the complex. It could be due to the releasing of
the axial ligand as a result of the reduction of the central metal.
It is well documented that when oxidation state of the central
metal decreases, its coordination number also decreases. Mn−P1c
gives a metal based reduction, [AcO–MnIIIPc−2]/[AcO–MnIIPc−2
]
−1
at −0.24 V. [AcO–MnIIPc−2
]
species release AcO− group and
form [MnIIPc−2] species. An equilibrium is established between
[AcO–MnIIPc−2
]
and [MnIIPc−2] sp−e1cies. [MnIIPc−2] reduces ꢀat
−1
−1.03 V (Red2) while [AcO–MnIIPc−2
]
reduces at −1.13 V (Red2).
After the second reduction process, a chemically irreversible
reduction process Red3 is recorded with SWV. Due to the suc-
ceeding chemical reaction, the anodic wave of Red3 couple has
smaller peak current than the cathodic wave. Moreover a new
anodic wave (Red(CP)) is recorded at −0.62 V due to the products
of the proposed chemical reaction. When the SWV is started before
Red3 process, the wave (Red(CP)) at −0.62 V disappears, which
illustrate a possible chemical reaction following the Red3 process.
Reversibility of Red1 and Red2 processes decreases when vertex
potential of CV exceeds Red3 process. Similarly, when the vertex
potential passes Oxd2 potential, Oxd1 process gets chemically
irreversible (supplementary materials: Fig. SM5). Spectroelectro-
chemical studies were employed (discussed below) to understand
the origin of the electron transfer reactions of MnPc (3).
It is well documented that redox behaviors of MPc complexes
having redox active metal center can be affected from the elec-
trolyte type. Since some ligands presenting in the electrolyte
system may coordinate to the metal center of Pc, which affects
the stability of the different oxidation states of the metal center.
For instance, coordination of DMSO th the cobalt center of CoPc
favor Co(III) oxidation state [31,43]. Thus CV and SWVs of MnPc (3)

D. Arıcan et al. / Electrochimica Acta 106 (2013) 541–555
547
Fig. 5. (a) CVs of CoPc (4) at various scan rates on a Pt working electrode in
DCM/TBAP and (b) SWV of CoPc (4) recorded with SWV parameters: step size = 5 mV;
pulse size = 100 mV; frequency = 25 Hz.
Fig. 4. (a) CVs of MnPc (3) at various scan rates on
in DMSO/TBAP and (b) SWV of MnPc (3) recorded with SWV parameters: step
a Pt working electrode
size = 5 mV; pulse size = 100 mV; frequency = 25 Hz.
FePc (5) complex gives very similar redox responses in both
DCM/TBAP (Fig. 7) and DMSO/TBAP (Fig. 8). As shown in these fig-
ure, FePc gives four reduction and two oxidation processes due to
the possible chemical reactions or the instability of the reduced
FeIIPc species, the first reduction processes Red1 recorded at
−0.37 V in DCM and at −0.44 V in DMSO are chemically irreversible
while the following reduction processes are in electrochemical
quasi-reversible range. All redox processes are recorded at more
negative potential in DMSO with respect to those in DCM. All redox
couples are also well clearly recorded with SWVs (Figs. 7b and 8b).
Spectroelectrochemical studies were employed to confirm the
assignments of the redox processes recorded with CVs and SWV.
Octa substitution of MPc complexes instead of tetra substitut-
ing does not alter the general character of the redox responses
of the complexes considerably as shown in Table 1. Redox pro-
cesses of octa substitution of MPcs just shift toward the positive
potentials with respect to the redox processes of tetra substituted
complexes. As a representative of the octa substituted MPcs, CV and
SWV responses of MnPc (7) in DCM/TBAP are given in Fig. 9. Like
MnPc (3), MnPc (7) gives also three reduction and two oxidation
processes. When compared with the redox properties of MnPc (3),
were also recorded in DMSO, a coordinating polar solvent (Fig. 4)
to investigate the solvent effect to the electrochemical behavior.
MnPc (3) gives three well-resolved reversible and diffusion con-
trolled reduction (Red1 at −0.26 V, Red2 at −0.86 V and Red3 at
−1.46 V). Polarizing ability of DMSO causes to the reduction of
the complex harder in DMSO solvent than that in DCM, thus the
reduction reactions are recorded at more negative potentials. How-
ever, Red2 process is recorded at more negative potential in DMSO.
Extending the coordination of metal center of MnPc (3) could be
possible in DMSO due to the stabilization of different oxidation
state of to the metal center of MnPc (3) with DMSO coordina-
tion, thus second metal based reduction of MnPc (3) complex is
recorded at less negative potential in DMSO. All redox processes
are chemically and electrochemically reversible in DMSO, while a
chemical reaction is coupled to the third reduction process in DCM.
An irreversible oxidation process could be recorded at 0.69 V with
SVW in DMSO/TBAP electrolyte system.
Fig. 5 illustrates the CV and SWV of CoPc (4) in DCM/TBAP. CoPc
(4) undergoes two reduction and two oxidation processes. ꢁEp‘s
of R1 and R2 couples of CoPc changed from 58 to 130 mV with
increasing scan rates from 10 to 500 mV s−1, which exhibit elec-
trochemical reversibility of the electron transfer reactions. Unity of
the Ipa/Ipc ratio of the first reduction couple with the scan rate and
linear variation of the Ipc with square root of the scan rates indicated
the purely diffusion controlled electron transfer mechanism of the
process. Fig. 6 represents the CV and SWV of CoPc (4) in DMSO/TBAP
to investigate the solvent effects to the electrochemical responses
of the complex. CoPc (4) gives very similar voltammetric responses
in DCM and DMSO. But, the redox couples of CoPc (4) in DMSO are
more reversible and the redox processes shift to the negative poten-
tials due to the electron donor property of the DMSO. Due to the
coordination of the CoIII center of the complex with DMSO, CoIIPc−2
oxidizes to CoIIIPc−2 easily at less positive potentials in DMSO. All
redox couples are electrochemically and chemically reversibility
with respect to ꢁEp, unity of the Ipa/Ipc ratio of the redox couples
at all scan rates and linear variation of the Ipc with the square root
of the scan rates.
Fig. 6. CV and SWV of CoPc (4) at 0.100 V s−1 scan rate on a Pt working electrode in
DMSO/TBAP.

548
D. Arıcan et al. / Electrochimica Acta 106 (2013) 541–555
Fig. 9. (a) CVs of MnPc (7) at various scan rates on
a Pt working electrode
in DCM/TBAP and (b) SWV of MnPc (7) recorded with SWV parameters: step
size = 5 mV; pulse size = 100 mV; frequency = 25 Hz.
Fig. 7. (a) CVs of FePc (5) recorded with different switching potential at 0.10 V s−1
scan rate on a Pt working electrode in DCM/TBAP and (b) SWV of FePc (5) recorded
with SWV parameters: step size = 5 mV; pulse size = 100 mV; frequency = 25 Hz.
3.3. Spectroelectrochemistry
To perform the assignments for the redox processes recorded
with the CVs and SWVs of the complexes and to investigate effect
of the solvent to the peak assignments, spectroelectrochemical
studies were employed. CuPcs have redox inactive centers, thus
spectral changes which are characteristics for Pc ring based redox
processes were recorded during spectroelectrochemical measure-
ments in both of DCM/TBAP (Fig. SM6) and DMSO/TBAP electrolyte
systems (Fig. SM7). MnPc, CoPc and FePc complexes have redox
active metal centers. It is well documented that electron transfer
reactions occurred on the metal centers of MPcs in addition to the
Pc based electron transfer reactions diversifies the spectral changes
of complexes during redox reactions. Thus detailed spectroelectro-
chemical analysis of these type complexes are required to decide
their potential technological applications. Here we illustrated spec-
tral changes of MnPc, CoPc and FePc complexes and discussed
effects of the substituents and solvents to the spectroelectrochemi-
cal responses of the complexes. Fig. 10 shows in situ UV–vis spectral
changes observed during the electro transfer reactions of MnPc (3)
in DCM/TBAP electrolyte system. During the first reduction reaction
at −0.50 V (Fig. 10a), the Q band at 785 nm shifts to 715 nm with the
increase in intensity. At the same time the band at 530 nm which
characterize Mn(III) form of the metal center decreases in intensity.
During this reduction reaction the B band at 358 nm shifts to 315 nm
with the increase in intensity. These spectral changes clearly indi-
reversibility of the redox couples of MnPc (7) decreases and redox
couples are shifted about 0.20 V to the positive potentials. When
we compared these data with the tetra substituted MPcs published,
we can propose the following order for the easier reduction of the
complexes.
MPc (octa) (S3) > MPc (peripherally tetra) (S1) > MPc (nonperiph-
erally tetra) (S2)
cated reduction of [AcO–MnIIIPc2−] to [AcO–MnIIPc2−
]
1−. Shifting
of the Q band to the shorter wavelengths and disappearance of the
band at 530 nm characterize this assignment of the reduction pro-
cess [31,40,41,43–47]. Well-defined isosbestic points are observed
at 415, 723, and 845 nm and 575 nm, which demonstrate that the
reduction proceeds cleanly in deoxygenated DCM to give a single
type reduced species. Fig. 10b illustrates the spectral changes dur-
1−
ing the second reduction process (reduction of [AcO–MnIIPc2−
]
species). As shown in this figure, two distinct spectral changes are
recorded. First of all, while the Q band at 715 nm decreases in inten-
sity, new bands at 513 and 850 nm are observed (changes from red
to purple spectrum). After a while isosbestic points start to changes.
The band at 850 nm shifts to 830 nm and small new bands are
Fig. 8. (a) CVs of FePc (5) recorded with different switching potential at 0.10 V s−1
scan rate on a Pt working electrode in DMSO/TBAP and (b) SWV of FePc (5) recorded
with SWV parameters: step size = 5 mV; pulse size = 100 mV; frequency = 25 Hz.

D. Arıcan et al. / Electrochimica Acta 106 (2013) 541–555
549
Fig. 10. In situ UV–vis spectral changes of MnPc (3) in DCM/TBAP electrolyte system. (a) Eapp = −0.50 V. (b) Eapp = −1.20 V (inset: Eapp = −1.70 V). (c) Eapp = 1.20 V (Inset:
Eapp = 1.20 V). (d) Chromaticity diagram. Each symbol represents the color of electro-generated species; ꢀ: MnIIIPc−2, ꢁ: MnIIPc−2, ꢂ: MnIPc−2, ꢁ: MnIPc−3, ଝ: MnIIIPc−1. (For
interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
recorded at around 600 nm. However, general trend of the spectral
changes is similar with the previous changes (changes from pur-
ple to blue spectrum). These spectral changes (formation of a band
reaction and formation of more than one type of reduced species.
This chemical reaction is more probably removing of axial acetate
group due to decreasing of the oxidation state of the manganese
center of the complex. It is well documented that coordination
number of the MPc complexes decrease when oxidation state
of the metal center decrease. Presence of this chemical reac-
tion is also recorded with the splitting of the reduction peak
to Red2 and Redꢀ2 during the CV measurement (Fig. 3). These
at 516 nm and decreasing of the band at 697 nm) can characterize
2−
a metal-based reduction of [AcO–MnIIPc2−
species, since [AcO–MnIPc2−
] ]
1− to [AcO–MnIPc2−
]
2− species gives a characteristic MLCT
band between 500 and 550 nm [31,40,41,43–47]. Changing the isos-
bestic points during the reduction indicate existence of a chemical
Scheme 2. Electron transfer mechanism of MnPc (3).

550
D. Arıcan et al. / Electrochimica Acta 106 (2013) 541–555
Fig. 11. In situ UV–vis spectral changes of MnPc (3) in DMSO/TBAP electrolyte system. (a) Eapp = −0.50 V. (b) Eapp = −1.00 V. (c) Eapp = −1.70 V. (d) Chromaticity diagram. Each
symbol represents the color of electro-generated species; ꢀ: MnIIIPc−2, ꢁ: MnIIPc−2, ꢂ: MnIPc−2, ꢁ: MnIPc−3. (For interpretation of the references to color in this figure
legend, the reader is referred to the web version of this article.)
spectral changes and CV responses of MnPc (3) indicate that
measurements. Fig. 10d represents the chromaticity diagram of
MnPc (3) recorded during the electron transfer reactions. Without
any potential application, the solution of MnPc (3) is red (x = 0.3731
and y = 0.3393) (point ꢀ in Fig. 10d). When −0.50 V was applied,
MnPc (3) starts to reduce and thus its color changes to green color
(x = 0.3287 and y = 0.3549) (point ꢁ in Fig. 10d) at the end of the first
reduction process. Purple color (x = 0.3364 and y = 0.2676) (point ꢂ
in Fig. 10d) at the end of second reduction and bluish purple color
(x = 0.3254 and y = 0.2596) (point ꢁ in Fig. 10d) at the end of the third
reduction reaction are recorded. Although distinct color changes
are recorded during the reduction processes, slight color changes
are recorded during the oxidation reactions. During the oxidation
reactions, color of the solution shifts from red to yellow color as
shown in the chromaticity diagram of the complex.
Spectroelectrochemical studies of MnPc (3) were also employed
in DMSO/TBAP electrolyte system (Fig. 11) and the responses in
DMSO were compared with those in DCM. When the spectral
changes in Fig. 10 are compared with Fig. 11, it is clear that spec-
tral changes during the first reduction at −0.50 V are completely
different in these solvents. As shown in Fig. 11a, the Q band at
785 nm decreases in intensity and a couple of bands are recorded at
676 and 720 nm in DMSO. Moreover, two new bands are recorded
in the LMCT regions at 585 and 920 nm. There is only one band
at 715 nm in DCM (Fig. 10). The couple bands 676 and 720 nm
could not belongs to different reduced species, because well-
defined and accurate isosbestic points in the spectra indicate the
1−
2−
[AcO–MnIIPc2−
]
reduced to [AcO–MnIPc2−
]
species and then
2−
[AcO–MnIPc2−
]
remove the acetate group. Two reduction waves
(Red2 and Redꢀ2) were recorded with CV and two distinct spec-
tral changes were observed during the second reduction reaction
of MnPc (3) at −0.90 V due to the equilibrium between these
species. Under the applied potential of the third reduction process,
while the band at 513 nm decreases, a band at 571 nm increases.
At the same time, the band at 715 nm and 830 nm disappears.
These spectral changes are characteristic changes for the ring-
2−
3−
based reduction process of [AcO–MnIPc2−
]
to [AcO–MnIPc3−
]
species. Fig. 10c illustrates the spectral changes recorded during
the oxidations of MnPc (3). During the first oxidation process,
the Q band decreases in intensity, while a new band increases at
893 nm. These spectral changes are characteristics of a ring-based
oxidation process in MnPc complexes, thus the couple Oxd1 is eas-
1+
ily assigned to [AcO–MnIIIPc2−]/[AcO–MnIIIPc1−
]
redox process
[31,40,41,43–47]. Under the applied potential of the second oxi-
dation process, the Q band shifts 758 nm with decreasing, which
characterize a metal-based oxidation process and thus the couple
2+
Oxd2 is easily assigned to [AcO–MnIIIPc1−
] ]
1+/[AcO–MnIVPc1−
redox process. As a result of electrochemical and in situ spec-
troelectrochemical analysis, we proposed the mechanism given
in Scheme 2. Color changes of the complex during the electron
transfer reactions were recorded with in situ electrocolorimetric

D. Arıcan et al. / Electrochimica Acta 106 (2013) 541–555
551
Fig. 12. In situ UV–vis spectral changes of CoPc (4) in DMSO/TBAP electrolyte system. (a) Eapp = −0.50 V. (b) Eapp = −1.50 V. (c) Eapp = = 0.80 V. (d) Chromaticity diagram. Each
−1
symbol represents the color of electro-generated species; ꢀ: [CoIIPc−2], ꢁ: [CoIPc−2
]
ꢂ: [CoIPc−3
] ]
−2, ଝ: [CoIIIPc−2 +1. (For interpretation of the references to color in this
figure legend, the reader is referred to the web version of this article.)
presence of one type of reduced species. Although different spec-
tral changes are recorded in different solvents, general trends of the
changes (shifting of the Q band to the shorter wavelength) char-
decrease in intensity which indicates decomposition of the com-
plex during the oxidation reaction (Fig. 11a inset). Color of the
electrogenerated species are given in Fig. 11d. MnPc (3) gives
similar colors for the electrogenerated reduced species. As it is illus-
trated, MnPc (3) behaves as electrochromic material due to the
different colors in its different oxidation states in solution, which
is an opportunity for the application in display and data storage
technologies.
acterize the metal-based reduction of MnPc (3) ([AcO–MnIIIPc2−
]
to [AcO–MnIIPc2−
]
1−) in DMSO like in DCM under applied poten-
tial at −0.50 V. It is well known that ␮-oxoMnPc species give an
absorption band at around 630 nm. To diminish the formation of
␮-oxoMnPc species the solution is purged gently with N2 before
the process and the solution is kept under N2 atmosphere during
the process. There is not a band at around 630 nm thus the complex
could not give ␮-oxoMnPc species. Fig. 11b illustrates the spec-
tral changes under the applied potential of −1.0 V. Formation of an
intense band at 533 nm and decreasing the Q band of the complex
assign the electron transfer reaction to a metal based reduction pro-
Fig. 12 represents in situ UV–vis spectral changes and in situ
recorded chromaticity diagram of CoPc (4) in DMSO/TBAP during
the electron transfer processes. Before any potential application,
CoPc (4) gives the Q band at 696 nm and the B band at 327 nm. When
−0.50 V was applied to the working electrode, the Q band shifts to
730 nm with decreasing in intensity and a new band is recorded
at 477 nm. At the same time, the B band shift to 311 nm with
decreasing in intensity. Clear isosbestic points are recorded at 310,
370, 575, 718, and 778 nm, which indicate reduction of CoPc (4) to
single type reduced species (Fig. 12a). Color of the solution changes
from greenish blue (x = 0.2756 and y = 0.346) (point ꢀ in Fig. 12d) to
light green (x = 0.3733 and y = 0.4005) (point ꢁ in Fig. 12d) during
the first reduction process. These spectral changes are characteris-
tic changes of a metal-based reduction process, thus it is easily to
cess ([AcO–MnIIPc2−
] ]
1− to [AcO–MnIPc2− 2−). Although the second
reduction reaction is complicated with a chemical reaction and thus
the second reduction process is split into Red2 and Redꢀ waves in
2
DCM (Fig. 10b), this process gives a single type reduced species
in DMSO. Because, well-defined isosbestic points are recorded in
DMSO (Fig. 11b) during the second reduction reaction and only one
peak Red2 is recorded with CV measurements. The spectral changes
given in Fig. 11c recorded during the third reduction reaction char-
attribute Red1 process of CoPc (4) to [CoIPc2−
] ]
1−/[CoIPc3− 2− pro-
cess [31,38–41,48,49]. Fig. 12b represents in situ spectral changes
during the second reduction reaction. While the Q band decreases
2−
acterize the ring-based reduction process of ([AcO–MnIPc2−
]
to
[AcO–MnIPc3−
]
3−) species. During the oxidation reaction all bands

552
D. Arıcan et al. / Electrochimica Acta 106 (2013) 541–555
Fig. 13. In situ UV–vis spectral changes of FePc (5) in DCM/TBAP electrolyte system. (a) Eapp = −0.40 V. (b) Eapp = −0.80 V (inset: Eapp = −1.10 V). (c) Eapp = −1.60 V. (d) Chro-
+1
maticity diagram. Each symbol represents the color of electro-generated species; ꢀ: [FeIIIPc−2], ꢁ: [FeIIPc−2
]
−1, ꢂ: [FeIPc−2
]
−2, ꢁ: [FeIPc−3
]
−3; ♦: [FeIPc−4
]
−3, ଝ: [FeIIIPc−1
]
.
(For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
in intensity, a broad band is recorded at around 560 nm. More-
spectral changes, isosbestic points changes continuously during
the reduction process. These spectral changes indicate formation
over the band at 477 nm remains as unchanged. These spectral
2−
changes assign the Red2 couple to [CoIPc2−
]
1−/[CoIPc3−
]
pro-
of more than one reduced species as a reduction product. These
1−
cess. The process gives isosbestic points at 296, 335, 380, 470, 645,
and 774 nm and yellow color (x = 0.3877 and y = 0.403) (point ꢂ
in Fig. 12d) at the end of the second reduction reaction. Fig. 12c
illustrates spectral changes during the oxidation reactions. Spec-
tral changes given in this figure indicate the metal based character
of the first oxidation reaction Oxd1 and ligand based nature of the
second one Oxd2. Decreasing of all band (except small increase in
the region at around 550 nm) indicate decomposition of the com-
plex after the second oxidation process under the applied potential.
In situ UV–vis spectral changes and in situ recorded chromaticity
diagram of CoPc (4) in DCM/TBAP electrolyte system was given in
in Fig. SM8 for comparison.
In situ UV–vis spectral changes and chromaticity diagram of
FePc (4) in DCM are given in Fig. 13. Upon first reduction, two
different spectral changes are recorded. First of all, the Q band at
752 nm shift to 698 nm and two new bands start to increase at 560
and 837 nm. The band at 860 nm decreases in intensity when the
potential, −0.5 V, was applied to the working electrode (from red
to purple spectra in Fig. 13a). Then the Q band at 698 nm starts to
decrease in intensity while the bands at 560 and 837 nm continue
to increase under the same potential application (from purple to
products are most probably reduced [AcO–FeIIPc2−
]
and axial
acetate removed [FeIIPc2−] species. Due to the decreasing the oxi-
dation state of central iron (III) ion coordination number of the
iron decreases and thus complex prefers to remove axial acetate
ion. Without any potential application, the solution of 4 is light
greenish blue (x = 0.323 and y = 0.344) (point ꢀ in Fig. 13d). As the
potential is stepped from 0 to −0.40 V, color of FeIIIPc−2 starts
to changes and yellow color (x = 0.37 and y = 0.366) (point ꢁ in
Fig. 13d) of monoanionic form, FeIIPc−2, was obtained at the end
of the first reduction. Second reductions of the [FeIIPc−2 1−indicate
]
the further metal-based redox processes (Fig. 13b). Under −0.80 V
potential application, the Q band at 707 nm shift to 682 nm without
decreasing while a new band is recorded at 560 nm. Shifting of the
2−
Q band indicate [FeIPc−2
]
formation [40,43,50]. Clear isosbestic
points were observed at 385, 478, 691, and 802 nm in the spectra.
Color changes from yellow to light orange (point:ꢁx = 0.364 and
y = 0.342) was recorded (Fig. 13d). These changes assign the process
Red2to [FeIIPc−2 1−/[FeIPc−3 2−. Fig. 13b inset and Fig. 13c repre-
] ]
sents the spectral changes during the further reduction processes.
These spectral changes indicate ring-based reduction processes for
both Red3 and Red4 processes. Spectral changes during the oxida-
tion processes of the complex indicated the ring-based oxidation of
the complex. Color changes during the electron transfer reactions
blue spectra in Fig. 13a). These spectral changes are assigned to
1−
[AcO–FeIIIPc2−]/[AcO–FeIIPc2−
]
process. Due to these different

D. Arıcan et al. / Electrochimica Acta 106 (2013) 541–555
553
Fig. 15. In situ UV–vis spectral changes of CoPc (4) in DMSO/TBAP electrolyte system
saturated with molecular oxygen (spectral changes from red to blue were recorded
under Eapp = −0.50 V and spectral changes from blue to purple were recorded under
Eapp = −1.50 V).
In situ spectroelectrochemical analyses were performed in oxy-
gen saturated DMSO/TBAP electrolyte system during the potential
application at the potentials of the redox processes to support
the interaction between CoPc (4) and O2 (Fig. 15). These analy-
ses indicate that interaction of the complex with molecular oxygen
just affects the second reduction reaction of the complex and
the reversibility of the redox processes. Under the open circuit
potential, spectra of CoPc (4) did not change with time when the
solution was saturated with oxygen. This behavior indicates that
[CoIIPc−2] does not interact with O2. During the first reduction
process at −0.50 V, spectral changes (from red to blue spectrum)
Fig. 14. (a) CVs and (b) SWVs of CoPc (4) recorded at 0.100 V s−1 scan rate on a Pt
working electrode in DMSO/TBAP during gradual bubbling with oxygen.
are represented in the chromaticity diagram in Fig. 13d. In situ
UV–vis spectral changes and in situ recorded chromaticity diagram
of FePc (5) in DMSO/TBAP electrolyte system was given in Fig. SM9
for comparison.
3.4. Interaction of complexes with molecular oxygen
1−
assigned to [CoIIPc−2]/[CoIPc−2
]
process are observed in both
oxygen removed and oxygen saturated electrolyte. However, while
a ring based reduction reaction was observed in oxygen removed
electrolyte (Fig. 12a), spectral changes start to return back in the
oxygen saturated solution, even more negative potentials up to
−2.0 V was applied. Consequently we can easily proposed the
following mechanism with respect to electrochemical and spec-
troelectrochemical measurements. [CoIIPc−2] did not interact with
molecular oxygen at its neutral state. [CoIIPc−2] reduced to CoIPc−2
at −0.54 V and reduced CoIPc−2 species interacts with O2 and form
[Pc−2CoII–O–CoIIPc−2] intermediate. Due to the formation of Co(II)
oxidation state, spectrum of the complex starts to return back.
MPc complexes have potential application as cathode active
material in fuel cell applications due to their catalytic activity
for O2 reduction reaction (ORR), thus, we have investigated the
interaction of the MPc complexes studied here with molecular
oxygen with electrochemical and in situ spectroelectrochemical
techniques. While CuPc complexes did not interact with O2, and
gave similar complex-based redox processes, MnPc (Fig. SM10),
CoPc (Fig. 14) and FePc complexes catalyze ORR. Fig. 14 represents
the CV and SWV responses of the interaction of CoPc (4) with the
molecular oxygen in DMSO/TBAP electrolyte system as a represen-
tative example for these complexes. As shown in the CVs (Fig. 14a)
and SWVs (Fig. 14b), CoPc (4) gives two reversible reduction pro-
cesses, Red1 at −0.54 V and Red2 at −1.49 V without O2. When
the electrolyte system was purged gradually with O2, the redox
behavior of Red1 and Red2 couples are affected considerably. The
anodic wave of the Red1 couple shifts to positive potentials and
a new wave is recorded at −0.27 V. However, the cathodic wave
of this couple remains unchanged during this process. Moreover,
Red2 couple shifts to the more negative potential gradually with
increasing current. These voltammetric data indicate that CoIIPc−2
species reduce to CoIPc−2 at −0.54 V and CoIPc−2 interacts immedi-
ately with O2 and form [Pc−2CoII–O–CoIIPc−2]. Observation of new
waves at −0.27 V and shifting of the anodic wave of the Red1 cou-
ple indicate formation of species different than CoIPc−2 due to the
reaction with oxygen. However, at the end of the one CV cycle,
original CoIIPc−2 species are formed. Because unchanging of the
peak current of the cathodic wave of the Red1 indicates regenera-
tion of CoIIPc−2 after each CV cycle. These data indicate that during
this catalytic mechanism, CoIIPc−2 species reduce to CoIPc−2 which
interact with molecular oxygen and catalyze the ORR and at the end
of the reaction; the electrocatalyst CoIIPc−2 species are regenerated.
The intermediate, [Pc−2CoII–O–CoIIPc−2], forms original [CoIIPc−2
and superoxide ions during the reverse potential scans of CV and
SWV measurements (Fig. 14), oxidation of [Pc−2CoII–O–CoIIPc−2
]
]
intermediate illustrates different redox responses than those of
[CoIIPc−2], thus the anodic peak of Red1 couple characterizing the
oxidation of CoI to CoII for [CoIIPc−2] species at −0.50 V shifts to less
negative potentials in oxygen saturated solution.
4. Conclusions
New metallophthalocyanine complexes tetra-substituted with
3,4-(dimethoxyphenylthio) moieties at nonperipheral positions
and octa substituted at peripheral positions were synthesized. All
complexes were characterized by FT-IR, mass spectroscopy, and
electronic spectroscopy as well as elemental analysis. The com-
plexes have good solubility in various polar and nonpolar organic
solvents and not aggregated (in the same solvents) within a wide
concentration range. Presence of redox active metal centers, CoII,
FeIIIAc, and MnIIIAc into the phthalocyanine core extends the redox
richness of the Pc ring with the reversible metal-based reduction

554
D. Arıcan et al. / Electrochimica Acta 106 (2013) 541–555
and oxidation couples. This expanded redox behavior of the com-
plexes are the desired properties of the electrochemical applica-
tions, especially, electrocatalytic, electrochromic and electrosens-
ing applications. Number and the position of the substituents affect
the redox behavior of the complexes. Comparison of the redox
behavior of S1, S2 and S3 series complexes indicates that it is pos-
sible to synthesize desired complexes by changing the number,
type, and position of the substituents in order to adjust the desired
electrochemical responses needed for the aiming electrochemical
applications. Distinctive colors for electrogenerated anionic and
cationic redox species were recorded with in situ electrocolorimet-
ric measurements. Different color of the electrogenerated species
indicates their possible application in the display technologies,
e.g. electrochromic and data storage application. Presence of O2
in the electrolyte system influences the redox couples of the com-
plexes due to the interaction between O2 and MPcs having redox
active metal center, which indicates electrocatalytic activities of
these complexes for the ORR. Catalytic reduction of oxygen with
redox active MPcs are the desired factor of a material for the pos-
sible usages in fuel cell applications as cathode active material.
Multi-electrons and reversible electron transfer couples recorded
at low potentials exhibit the possible application of the complexes
in different electrochemical technologies, such as electrochromic,
electrocatalytic and electrosensor applications. Thus in our forth-
coming studies, we aim to investigate the relevant application
studies.
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Acknowledgements
This study was supported by Yıldız Technical University (Project
No.: 2012-01-02-KAP03), Marmara University (Project No.: FEN-C-
YLP-110411-0099), and TUBITAK (Project No.: 111T179).
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Appendix A. Supplementary data
Supplementary data associated with this article can be
found, in the online version, at http://dx.doi.org/10.1016/
j.electacta.2013.04.166.
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