Synthesis, spectroscopic, electrochemical and spectroelectrochemical properties of metal free, manganese, and cobalt phthalocyanines bearing peripherally octakis-[4-(thiophen-3-yl)-phenoxy] substituents

Article abstract of DOI:10.1016/j.poly.2010.09.008

Metal free (2), manganese (3), and cobalt (4) phthalocyanines, which are octa-substituted at the peripheral positions with [4-(thiophen-3-yl)-phenoxy] moieties, were synthesized and electrochemical properties were reported for the first time. The complexe

Full text of DOI:10.1016/j.poly.2010.09.008

Polyhedron 29 (2010) 3310–3317
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Synthesis, spectroscopic, electrochemical and spectroelectrochemical properties
of metal free, manganese, and cobalt phthalocyanines bearing peripherally
octakis-[4-(thiophen-3-yl)-phenoxy] substituents
b,
a
Ahmet Lütfi Ug˘ur a, Ali Erdog˘mußs a, , Atıf Koca , Ulvi Avcıata
⇑
⇑
a Department of Chemistry, Yildiz Technical University, 34210 Esenler, Istanbul, Turkey
b Department of Chemical Engineering, Engineering Faculty, Marmara University, Kadıköy, Istanbul, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
Metal free (2), manganese (3), and cobalt (4) phthalocyanines, which are octa-substituted at the periph-
eral positions with [4-(thiophen-3-yl)-phenoxy] moieties, were synthesized and electrochemical proper-
ties were reported for the first time. The complexes were characterized by elemental analysis, IR, 1H NMR,
mass spectroscopy, and electronic spectroscopies. Electrochemical and spectroelectrochemical measure-
ments exhibit that incorporation of the redox active metal ions, CoII and MnIIIOAc, into the phthalocya-
nine core extends the redox richness of the Pc ring with the reversible metal-based reduction and
oxidation couples in addition to the common Pc ring-based electron transfer processes. Presence of
Received 13 August 2010
Accepted 7 September 2010
Available online 17 September 2010
Keywords:
Phthalocyanines
Manganese
molecular oxygen in the electrolyte system causes to form p-oxo MnPc complexes, which alter the vol-
Cobalt
tammetric and spectroelectrochemical responses of the complex. An in situ electrocolorimetric method
has been applied to investigate the color of the electro-generated anionic and cationic forms of the com-
plexes for possible electrochromatic applications.
Electrochemistry
Spectroelectrochemistry
Electrocolorimetry
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
The solubility of phthalocyanines is the most important future
of the complexes for theirs possible applications and for investiga-
The extensive research interest to metallophthalocyanines
(MPcs) stems from their versatile technological applications, which
include their uses in electronic devices as gas sensors, as photosen-
sitizers, in non-linear optics, in electrochromic devices and in
Langmuir–Blodgett films [1–3]. MPcs are highly robust and func-
tional chemicals that are widely used as pigments and oxidation
catalyst [4]. Recently, they have become important materials in
electronic, optoelectronic, and molecular electronic applications
owing to their characteristic molecular structure [5–8]. MPcs com-
plexes that are peripherally substituted with alkylthiol and phen-
ylthiol derivatives show rich electrochemical and photochemical
properties [9–15], which give great promise for their potential
applications as electrocatalyst and photocatalyst [16]. Many of
these technological applications of MPcs are due to their high elec-
tron transfer abilities which are almost all based on their conju-
tion of their chemical and physical characteristics [18]. A common
mean for preparing soluble phthalocyanines is to attach functional
groups like tertiary butyl, amide, or carboxylic acid groups [19,20],
or bulky and crown ether groups [21–23], and azo groups [24], etc.
to the peripheral of phthalocyanine ring and/or axial positions of
the trivalent central metal ions (Mn (III), In (III) and Ga (III)). In
the case of soluble products in nonpolar organic solvents, these
substituents are generally long alkyl or alkoxy chains, bulky sub-
stituents, or macrocyclic groups such as crown ether [25]. In our
previous study, the bulky (thiophen-3-yl)-phenol ligand was cho-
sen to improve the solubility and prevent aggregation behavior
of the tetra substituted MPc complexes substituted peripherally
[26]. In this study, same group was preferred to synthesize octa-
substituted MPcs having good solubility in the common organic
solvents without aggregation. It is well known that moieties
substituted non-peripherally affect the electrochemical responses
of Pc ring and metal center more than peripheral substitution.
For example, non-peripheral substitutions prevent the interaction
of central metal with molecular oxygen due to the steric effect
and/or electron releasing ability of the substituents [27,28]. The
interest in MPcs having redox active metal centers those are easily
reduced is of importance since these complexes are well known
electrocatalysts for many reactions such as electrocatalytic reduc-
tion of molecular oxygen for fuel cell applications [16].
gated
p electron ring system and interaction of p electron system
with center metal ions and peripheral and nonperipheral substitu-
ents [16,17].
⇑
Corresponding authors. Tel./fax: +90 2163480292.
E-mail addresses: erdogmusali@hotmail.com (A. Erdog˘musß), akoca@marmara.
edu.tr (A. Koca).
0277-5387/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2010.09.008

A. Lütfi Ug˘ur et al. / Polyhedron 29 (2010) 3310–3317
3311
C112H66N8O8S8: C, 70.44; H, 3.45; N, 5.87; S, 13.40. Found: C,
2. Experimental
67.85; H, 3.17; N, 5.89; S, 13.16%. MS (ESI-MS) m/z: Calc.:
1908.3; Found: 1908.5 [M]+.
2.1. Materials and equipment
Dimethyl sulfoxide (DMSO), N,N0-dimethylformamide (DMF),
chloroform (CHCl3), tetrahydrofuran (THF), methanol (MeOH),
dichloromethane (DCM), 1-pentanol, n-hexane and toluene were
purchased from Merck; 4,5 dichlorophthalonitrile, 4-(thiophen-3-
yl)-phenol, 1,8-diazabicyclo [5.40] undec-7-ene (DBU), potassium
carbonate, manganese acetate and cobalt chloride were purchased
from Aldrich.
FT-IR spectra (KBr pellets) were recorded on a Perkin Elmer
Spectrum One Spectrometer. The mass spectra were acquired on
a Bruker Daltonics (Bremen, Germany) MicroTOF mass spectrome-
ter equipped with an electron spray ionization (ESI) source. The
instrument was operated in positive ion mode using a m/z range
of 50–3000. The capillary voltage of the ion source was set at
6000 V and the capillary exit at 190 V. The nebulizer gas flow
was 1 bar and drying gas flow 8 mL/min. 1H NMR spectra were re-
corded in CDCl3 solutions on a Varian 500 MHz spectrometer. Ele-
mental analyses were obtained with a Thermo flash EA 1112
Series. GC–MS spectra were acquired on a Agilent Technologies
including 6890N network GC system and 5973 inert Mass selective
detector. UV–Vis spectra were recorded on a Shimadzu UV-2450
spectrophotometer.
2.2.3. Manganes(III)acetate octakis-[4-(thiophen-3-yl)-
phenoxy]phthalocyanine (3)
Compound
1 (0.10 g, 0.21 mmol), manganese (II) acetate
(0.15 g, 0.11 mmol) and 2.0 cm3 of 1-pentanol were placed in a
standard Schlenk tube in the presence of 1,8-diazabicyclo[5.4.0]
undec-7-ene (DBU) (0.20 cm3, 0.132 mmol) under the argon atmo-
sphere and held at the reflux temperature for 10 h. After cooling to
the room temperature, the reaction mixture was precipitated by
adding it drop-wise into n-hexane. The crude product was precip-
itated, collected by filtration, and then washed with hot hexane.
The crude green product was further purified by chromatography
over a silica gel column using THF and a mixture of CHCl3:MeOH
(100/1 by volume) as eluents respectively. Yield = 30 mg (27%).
UV–Vis (DMC): kmax nm (log e) 349 (4.24), 631 (4.55), 731 (4.80).
IR spectrum (cmꢀ1): 3097 (Ar-CH), 2953 (aliphatic-CH), 1727
(C@O), 1598 (C@C), 1533, 1496, 1440, 1395, 1330, 1243, 1079
(C–O–C), 1001, 895 (Mn–O), 715 (C–S–C), 668 (Pc skeletal). Anal.
Calc. for C114H67N8O10S8MnAc: C, 67.77; H, 3.34; N, 5.55; S,
12.70. Found: C, 67.59; H, 3.24; N, 5.74; S, 13.01%. MS (ESI-MS)
m/z: Calc.: 2020; Found: 1961.2 [MꢀAc]+.
2.2.4. Cobalt octakis-[4-(thiophen-3-yl)-phenoxy]phthalocyanine (4)
The synthesis and purification of 4 was as outlined for 3, except
that metal salt (CoCl2) was employed instead of manganese (II)
acetate. The amounts of the other reagents were anhydrous cobalt
(II) chloride (0.014 g, 0.11 mmol) and 1,8-diazabicyclo[5.4.0] un-
dec-7-ene (DBU) (0.20 cm3, 0.132 mmol). Yield = 25 mg (24%).
2.2. Synthesis
2.2.1. 4,5-[4-(Thiophen-3-yl)-phenoxy]-phthalonitrile (1)
4,5-Dichlorophthalonitrile (1.12 g, 5.70 mmol) was dissolved in
DMF (20.0 cm3) under argon and 4-(thiophen-3yl)-phenol (2.00 g,
11.40 mmol) was added. After stirring for 30 min at room temper-
ature, finely ground anhydrous potassium carbonate (3.94 g,
28.4 mmol) was added in portions during 2 h with efficient stir-
ring. The reaction mixture was stirred and monitored by thin layer
chromatography (TLC), using CHCl3 under argon atmosphere at
room temperature for 48 h. Then the mixture was poured into
250 cm3 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 = 2.15 g (80%). IR spectrum (cmꢀ1): 3103 (Ar-CH),
2231 (C„N), 1586 (C@C), 1486, 1383, 1275, 1203, 1075 (C–O–C),
1012, 852, 780, 733 (C–S–C). 1H NMR (CDCl3): d = 7.92 (1H, s, Ar-
H), 7.75–7.69 (4H, m, Ar-H), 7.52–7.42 (6H, m, Ar-H), 7.29–7.25
(1H, d, Ar-H), 7.17–7.14 (4H, d, Ar-H). Anal. Calc. for C28H16N2O2S2:
C, 70.57; H, 3.38; N, 5.88; S, 13.46. Found: C, 71.02; H, 3.45; N, 5.81,
S, 13.59 %. MS (ESI-MS) m/z: Calc.: 476; Found: 499 [M+Na]+.
UV–Vis (DCM): kmax nm (log e) 339 (4.31), 607 (4.61), 669 (4.87).
IR spectrum (cmꢀ1): 3098 (Ar-CH), 1599 (C@C), 1534, 1498,
1441, 1395, 1331, 1246, 1080 (C–O–C), 1001, 895, 863, 716 (C–
S–C), 671 (Pc skeletal). Anal. Calc. for C112H64N8O8S8Co: C, 68.45;
H, 3.28; N, 5.87; S, 13.44. Found: C, 68.23; H, 3.38; N, 5.96; S,
13.17%. MS (ESI-MS) m/z: Calc.: 1965.2; Found: 1965.4 [M]+.
2.3. Electrochemical measurements
The cyclic voltammetry (CV) and square wave voltammetry
(SWV) measurements were carried out with Gamry Reference
600 potentiostat/galvanostat controlled by an external PC and uti-
lizing a three-electrode configuration at 25 °C. The working elec-
trode was a Pt disc with a surface area of 0.071 cm2. A Pt wire
served as the counter electrode. Saturated calomel electrode
(SCE) was employed as the reference electrode and separated from
the bulk of the solution by a double bridge. Electrochemical grade
TBAP in extra pure DMSO was employed as the supporting electro-
2.2.2. Metal free octakis-[4-(thiophen-3-yl)-phenoxy]phthalocyanine
(2)
lyte at a concentration of 0.10 mol dmꢀ3
.
Compound 1 (0.10 g, 0.21 mmol) and 2.0 cm3 of dry 1-pentanol
were placed in a standard Schlenk tube in the presence of 1,8-
diazabicyclo[5.4.0] undec-7-ene (DBU) (0.20 cm3, 0.132 mmol) un-
der the argon atmosphere and held at the reflux temperature for
10 h. After cooling to the 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, ethanol, and methanol respectively. The crude green
product was further purified by chromatography over a silica gel
column using THF and a mixture of CHCl3:MeOH (100/5 by vol-
ume) as eluents respectively. Yield = 22 mg (23%). UV–Vis (DCM):
2.4. In situ spectroelectrochemical and in situ electrocolorimetric
measurements
UV–Vis absorption spectra and chromaticity diagrams were
measured by an Ocean Optics QE65000 diode array spectropho-
tometer. In situ spectroelectrochemical measurements were car-
ried out by utilizing a three-electrode configuration of thin-layer
quartz thin-layer spectroelectrochemical cell at 25 °C. The working
electrode was a Pt gauze semitransparent electrode. Pt wire coun-
ter electrode separated by a glass bridge and a SCE reference elec-
trode separated from the bulk of the solution by a double bridge
were used. In situ electrocolorimetric measurements, under poten-
tiostatic control, were obtained using an Ocean Optics QE65000
diode array spectrophotometer at color measurement mode by
kmax (nm) (log e) 343 (4.65), 610 (4.36), 668 (4.99), 703 (4.93). IR
spectrum (cmꢀ1): 3286 (N–H), 3100 (Ar-CH), 1600 (C@C), 1534,
1496, 1470, 1335, 1232, 1085 (C–O–C), 995, 946, 776, 713 (C–S–
C). 1H NMR (DMSO): d = 8.11–7.26 (64H, m, Ar-H). Anal. Calc. for
utilizing
a three-electrode configuration of thin-layer quartz

3312
A. Lütfi Ug˘ur et al. / Polyhedron 29 (2010) 3310–3317
spectroelectrochemical cell. The standard illuminant A with 2° ob-
server at constant temperature in a light booth designed to exclude
external light was used. Prior to each set of measurements, back-
ground color coordinates (x, y, and z values) were taken at open-
circuit, using the electrolyte solution without the complexes under
study. During the measurements, readings were taken as a function
of time under kinetic control, however only the color coordinates at
the beginning and final of each redox processes were reported.
2231, 1075 and 733 cmꢀ1 were observed for 1 in the FTIR spectra,
respectively. Aromatic C–H peaks were also observed at 3103 cmꢀ1
for 1 in the FTIR spectra. The 1H NMR spectrum of 1 showed signals
with d ranging from 7.14 to 7.92, belonging to aromatic protons,
integrating for 16 protons for 1 as expected.
After conversion of 1 into the metal-free 2 and metallophthalo-
cyanines 3 and 4, the sharp peak for the CN vibration at 2231 cmꢀ1
disappeared. The IR spectra of metal-free 2 and metallophthalocy-
anines 3 and 4 are very similar. The significant difference is the
presence of N–H vibrations of the inner phthalocyanine core which
are assigned to a weak vibration at 3286 cmꢀ1 in the metal-free
compound. The characteristic vibrations corresponding to the
ether groups (C–O–C) were observed at 1085 (for 2), 1079 (for 3),
and 1080 cmꢀ1 (for 4). Aromatic C–H peaks were observed above
3050 cmꢀ1 for the all complexes. IR bands at 895 cmꢀ1 correspond
to MnIII–O vibration from the bond between MnIII and the axial
acetate ligand for complex 3. Complex 3 also showed the C@O
band and aliphatic C–H band of the acetate ion at 1727 and
2953 cmꢀ1 respectively.
3. Results and discussion
3.1. Synthesis and characterization
The synthetic procedure for phthalonitrile 1 and novel phthalo-
cyanines 2, 3 and 4 is as outlined in Scheme 1. Cyclotetrameriza-
tion of the phthalonitrile derivative
1 to the metal-free
phthalocyanine (2) and its metal complexes (3 and 4) were
accomplished in 1-pentanol in the presence of a few drops of
1,8-diazabicyclo[5.4.0]undec-7-ene(DBU) as a strong base at reflux
temperature in a sealed tube. The green cyclotetramerization
product, MPcs (M = 2H, Mn(III) acetate and Co(II)), which were
purified by column chromatography, were obtained in a moderate
yield (23% for 2, 27% for 3 and 24% for 4).
The 1H NMR spectrum of compound 2 indicates the aromatic
protons between 8.11 and 7.26 ppm. A common feature of this
spectrum is the broad absorptions caused by the aggregation of
the phthalocyanines [29]. The NH-protons of compound 2 could
not be observed in the 1H NMR spectrum owing to the probable
strong aggregation of the molecules [30]. 1H NMR measurement
of the cobalt (II) and manganese (III) phthalocyanine 3 and 4 was
precluded owing to its paramagnetic nature. In the mass spectra
Elemental analysis results and the spectral data (1H NMR, FTIR,
Mass, and UV–Vis) of new compounds are consistent with the as-
signed formulations. The characteristic vibrations corresponding
to CN, ethers groups (C–O–C) and thio ethers groups (C–S–C) at
Scheme 1. Synthetic route of 4,5-[4-(thiophen-3-yl)-phenoxy]-phthalonitrile (1) and its metallophthalocyanines (M = 2H, Co(II) and MnAc(III), (i) anhydrous CoCl2, or
Mn(II)acetate, 1-pentanol, DBU, 10 h.

A. Lütfi Ug˘ur et al. / Polyhedron 29 (2010) 3310–3317
3313
of phthalocyanines obtained by the relatively soft ESI-MS tech-
nique, the molecular ion peaks were observed at m/z 1908.5 for
2, 1965.4 for 4 and M-Ac ion peak was observed at m/z 1961.2
for 3, confirmed the proposed structures. Elemental analysis re-
sults were also consistent with the proposed structures of 1–4 as
expected. Since the synthesis used Mn (II) acetate, we would ex-
pect the MnIIPc to be formed, but the Q-band in the UV–Vis spec-
trum (discussed below) is red-shifted to be the MnIIPc species. This
observation is characteristic of manganese (III) phthalocyanine
complexes [28]. As purification takes place in aerobic conditions,
it can be expected that the MnIIIPc species is formed.
study, the aggregation behaviors of the Pcs derivatives (2–4) were
investigated in DCM and CHCl3 at different concentration.
Although the complexes 2 and 4 did not show aggregation in these
solvents, the complex 3 indicates slight aggregation tendency as
shown in Fig. 1b. Lambert–Beer law was obeyed for these com-
pounds in the concentrations ranging from 4.0 ꢁ 10ꢀ6 to
2.0 ꢁ 10ꢀ5 mol dmꢀ3 as given an example for 3 in CHCl3 in
Fig. 1b [32].
3.2. Voltammetric and spectroelectrochemical characterization
The best indications for phthalocyanine systems are given by
their UV–Vis spectra in solution. The synthesized phthalocyanines
(2–4) showed electronic spectra typical of MPc complexes with Q
and B bands. The ground state electronic absorption spectra of 2–
4 in DCM are shown in Fig. 1a. A typical spectrum of the metal-free
phthalocyanine 2 in dichloromethane shows a doublet in the Q
band region at 703 and 668 nm, and the B band is recorded at
343 nm; while MPcs 3 and 4 give intense single Q bands at 731
and 669 nm, and B bands at 349 and 339 nm respectively. The con-
sequence of the substitution with eight [4-(thiophen-3-yl)-phen-
oxy] has been clearly observed by the high solubility of the Pcs 2
to 4 in organic solvents such as DCM, CHCl3, THF, DMF, DMSO,
and toluene. Aggregation behavior of Pc is depicted as a coplanar
association of rings progressing from monomer to dimer and high-
er order complexes and it is dependent on concentration, nature of
solvent, substituents, metal ions, and temperature [31]. In this
The CVs and SWVs of MnPc (3) and CoPc (4) were obtained in
deaerated DCM/TBAP electrolyte system on a Pt working electrode
and voltammetric analysis results are listed in Table 1 with the re-
lated MPc complexes. As shown in Fig. 2, MnPc (3) displays three
well-resolved reduction processes (R1 at 0.010 V, R2 at ꢀ0.86 V
and R3 at ꢀ1.34 V) with CV and SWV measurements. These pro-
cesses are quasi-reversible and diffusion controlled with respect
to peak separation (DEp) and peak current ratio (Ip,a/Ip,c) analyses.
A reversible oxidation couple (O1) is also recorded at 1.05 V with
both CV and SWV measurements. Although the first reduction cou-
ple (R1) has anodic to cathodic peak separation (DEp = 75 mV at
0.100 mV sꢀ1 scan rate) within the reversible electron transfer
character, its peak to peak current ratio (Ip,a/Ip,c) is smaller than
unity (0.70 at 0.050 V sꢀ1 scan rate) at slow scan rates but get big-
ger with increasing scan rates (1.10 at 1.000 V sꢀ1 scan rate). These
voltammetric behaviors indicate the presence of a chemical reac-
tion accompanied with the electron transfer reaction. Recording
of a succeeding wave (R01) at ꢀ0.22 V support the existence of this
mechanism and this wave is easily assigned to the chemical reac-
tion product. Other possible assignments for this wave might be
the aggregation or l-oxo formation of the MnPc species. To clarify
the origin of this wave, interaction of MnPc with the molecular
oxygen is analyzed with CV and SWV measurements (Fig. 3a). It
is well documented that MnIIPc-2 species reacts with O2 and form
l
-oxo MnPc species, [PcMnIII–O–MnIIIPc] [33–36]. As shown in
Fig. 3a, while MnPc gives a quasi-reversible reduction process at
0.01 V followed with R0 at ꢀ0.22 V without O2, purging of the elec-
1
trolyte system gradually with O2 affect the redox behavior of R1
couple. During this purging process, while the anodic couple of
the peak shifts to the positive potentials with decreasing in the
current intensity and disappears finally; a new cathodic wave is re-
corded at ꢀ0.49 V, which shifts to the positive potentials with
increasing in the current intensity. These voltammetric data indi-
cate that MnIIIPcꢀ2 species reduce to MnIIPcꢀ2 at 0.01 V and
MnIIPcꢀ2 reacts immediately with O2 and form [PcMnIII–O–MnIIIPc]
which reduces at around ꢀ0.49 V. Due to the reaction between
MnIIPcꢀ2 and O2, concentration of MnIIPcꢀ2 decreases with increas-
ing oxygen concentration, which causes disappearance of the ano-
dic peak of R1 couple assigned to MnIIPcꢀ2/MnIIIPcꢀ2 process. It is
clear that the reduction peak of
l-oxo MnPc is completely different
than R01; in consequence, R01 could not be due to the reduction of
l
-
oxo MnPc species. The only possibility for this wave is the reduc-
tion of the aggregated species. As shown in Fig. 2a, peak current
of R01 increases more than the peak current of the other processes
with increasing scan rates and decreased more than the peak cur-
rent of the other processes with diluting the solution. These data
assign R01 wave to the reduction of the aggregated species.
As shown in Fig. 3a as inset, redox behavior of the complex 3 is
not affected with different cathodic switching potentials. But ano-
dic switching potential affects the redox behavior of the complex
considerably. When CV scan is switched before the oxidation pro-
cess (from 1.0 V), the complex gives the common reduction cou-
ples during the cathodic scan. However, when the switching
potential passes the oxidation process (from 1.3 V), the first reduc-
tion peak shifts to the negative potentials during the cathodic scan.
Fig. 1. (a) UV–Vis spectra of compounds 2, 3, and 4 in dichloromethane. (b)
Aggregation behavior of
3
in CHCl3 at different concentrations: (4 ꢁ 10ꢀ6
–
20 ꢁ 10ꢀ6 mol dmꢀ3) (inset: Plot of absorbance vs. concentration).

3314
A. Lütfi Ug˘ur et al. / Polyhedron 29 (2010) 3310–3317
Table 1
Voltammetric data of the complexes with the related metallophthalocyanines for comparison.
Complex
Ring oxidation
1.05
65
MIII/MII
MII/MI
Ring reductions
dDE1/2
Reference
tw
MnPc (3)
E1/2 (V vs. SCE) in DMSOa
0.010
67
0.70
ꢀ0.86
57
0.75
ꢀ1.34
127
0.70
1.06
D
Ep (mV)b
a
Ip,a/Ip,c
0.92
CoPc (4)
E1/2 (V vs. SCE) in DMSOa
1.40e
0.69
90
1.05
ꢀ0.25
155
0.90
ꢀ1.41
164
0.77
0.94
D
Ep (mV)b
tw
c
Ip,a/Ip,c
MnPc
MnPc
MnPc
CoPc
E1/2 (V vs. SCE) in DMSO
E1/2 (V vs. SCE) in DMSO/Cl
E1/2 (V vs. SCE) in DMF
E1/2 (in DMSO)
ꢀ0.08
ꢀ0.12
ꢀ0.14
0.46
ꢀ0.76
ꢀ0.77
ꢀ0.69
ꢀ0.36
ꢀ0.15
[48]
[48]
[48]
[49]
[50]
0.87
0.87
1.23
ꢀ1.46
ꢀ1.27
ꢀ1.24
CoPc
E1/2 (in DMSO)
0.775
ꢀ1.95
a
b
c
E1/2 = (Epa + Epc)/2 at 0.100 V sꢀ1
.
D
Ep = Epa ꢀ Epc at 0.100 V sꢀ1
.
Ip,a/Ip,c for reduction, Ip,c/Ip,a for oxidation processes at 0.100 V sꢀ1 scan rate.
d
e
D
E1/2
=
D
E1/2 (first oxidation) ꢀ
DE1/2 (first reduction).
Recorded by SWV. tw: this work.
Fig. 2. (a) CVs of MnPc (3) (5.0 ꢁ 10ꢀ4 mol dmꢀ3) at various scan rates on a Pt
working electrode in DMSO/TBAP. (b) SWV of 3 recorded with SWV parameters:
step size = 5 mV; pulse size = 100 mV; frequency = 25 Hz.
Fig. 3. (a) CVs of 3 (5.0 ꢁ 10ꢀ4 mol dmꢀ3) recorded at 0.100 V sꢀ1 scan rate with
various O2 concentration which purged into DMSO/TBAP electrolyte system (inset:
CVs of MnPc (5.0 ꢁ 10ꢀ4 mol dmꢀ3) recorded at 0.100 V sꢀ1 scan rate with different
cathodic switching potentials). (b) CVs of 3 (5.0 ꢁ 10ꢀ4 mol dmꢀ3) recorded at
0.100 V sꢀ1 scan rate with different anodic switching potentials.
Moreover when the switching potential goes to more positive
potentials all common redox processes disappear and new waves
are recorded at around 0.63 V and ꢀ0.60 V. These voltammetric
data indicate decomposition of the complex after the oxidation
process and the products of the decomposition reaction coated
on the working electrode, which form a barrier for the electron
transfer reaction of the MnPc species in the bulk solution (Fig. 3b).
Spectroelectrochemical studies were also employed to confirm
the assignments in the CVs of MnPc (3). In comparison with the
MnPc complexes in the literature [34–41], the first two reduction
processes are assigned to the metal based processes, [AcO-
MnIIIPcꢀ2]/[AcO-MnIIPcꢀ2] and [AcO-MnIIPcꢀ2]/[AcO-MnIPcꢀ2] and
the third one is assigned to the ligand-based process, [AcO-
MnIPcꢀ2]/[AcO-MnIPcꢀ3]. Oxidation process of the complex is a
ring-based process, [AcO-MnIIIPcꢀ2]/[AcO-MnIIIPcꢀ1]. In situ UV–
Vis spectral changes and chromaticity diagram of MnPc are given
in Fig 4. Fig. 4a shows in situ UV–Vis spectral changes observed
upon controlled potential reduction of 3 at ꢀ0.30 V corresponding
to couple R1. Before any potential application, observation of a
band at 523 nm and the red shifted Q band at 731 nm are charac-
teristic of MnIIIPcꢀ2 species. Upon reduction, the Q band at 731 nm
shifts to 683 nm, while the B band at 377 shifts to 358 nm with
increasing. These spectral changes are assigned to [AcO-MnIIIPc-
2]/[AcO-MnIIPc-2] process. Formation of [AcO-MnIIPc-2] is charac-
terized by shifting of the Q band to shorter wavelength values
[34–41]. To diminish formation of
l-oxo MnPc species, solution

A. Lütfi Ug˘ur et al. / Polyhedron 29 (2010) 3310–3317
3315
Fig. 4. In situ UV–Vis spectral changes of 3. (a) Eapp = ꢀ0.30 V. (b) initial part of the spectral changes at Eapp = ꢀ1.00 V (inset i: final part of the spectral changes at
Eapp = ꢀ1.00 V; inset ii: Eapp = ꢀ1.50 V. (c) Eapp = 1.20 V. (d) Chromaticity diagram (each symbol represents the color of electro-generated species; h: AcO-MnIIIPcꢀ2 , s: AcO-
MnIIPcꢀ2, 4: AcO-MnIPcꢀ2
,
5: AcO-MnIPcꢀ3, }: MnIPcꢀ3; q: AcO-MnIIIPcꢀ1
.
is purged gently with N2 before the process and solution is kept un-
der N2 atmosphere during the process. It is well known that -oxo
lishing an equilibrium between axially coordinated [AcO-
MnIIPcꢀ2 ꢀ1 and non coordinated [MnIIPcꢀ2] species. Further reduc-
l
]
MnPc species give an absorption band at around 630 nm
[34,41,42]. There is no band at this wavelength during the reduc-
tion processes. Thus, all redox processes are easily assigned to
the formation of electrogenerated MnPc (3) species. Color changes
of the complex in solution during the redox processes were re-
corded with in situ electrocolorimetric measurements. Without
tion of the complex at ꢀ1.50 V potential application indicate a Pc
ring-based reduction process (Fig. 4b inset: ii). During this process,
while the Q band decreases without shifting, the absorption of the
region at around 570 nm increases. Moreover, the band at 524 nm
remains as unchanged and the band at 848 nm shifts to 800 nm.
These spectral changes are characteristics of the reduction of
[AcO-MnIPcꢀ2] to [AcO-MnIPcꢀ3]. Colors of the anionic species
are given in Fig. 4d. To confirm the origin of the oxidation process,
O1, in situ UV–Vis changes were recorded under the controlled po-
tential application at 1.20 V (Fig. 4c). During this process, the Q
band decreases in intensity, while a new band at 830 nm is re-
corded. These spectral changes are characteristics of a ring-based
oxidation process in MnPc complexes, thus the couple O1 is easily
any potential application, solution of
3 is yellowish green
(x = 0.388 and y = 0.389) (point h in Fig. 4d). As the potential is
stepped from 0 to ꢀ0.40 V color of the neutral AcO-MnIIIPcꢀ2 starts
to change and bluish green (x = 0.315 and y = 0.359) (point s in
Fig. 4d) of monoanionic form of AcO-MnIIPcꢀ2 was obtained at
the end of the first reduction.
The reduction of MnIIPcꢀ2 species has been a subject of some
controversy, with some reports proposing ring reduction to the
MnIIPcꢀ3 species and others suggesting metal reduction to the
MnIPcꢀ2 species. During the second reduction process of 3, two dis-
tinct spectral changes were recorded. First of all, while two new
bands are recorded at 524 and 848 nm, the Q band and the band
at 731 nm decrease. Then the band at 731 nm increases slightly
again while the other bands continuous their previous trend. In
both of these two different spectral changes, increasing of the band
assigned to [AcO-MnIIIPcꢀ2]/[AcO-MnIIIPcꢀ1 +1
[34,41–43].
]
redox process
Fig. 5 shows the CV and DPV of CoPc (4). Within the electro-
chemical window of DMSO/TBAP in CV measurements, the com-
plex 4 illustrates two one-electron oxidation processes, and two
quasi-reversible one-electron reductions. For the first oxidation
couple, anodic to cathodic peak separations (DEp) changed from
67 to 130 mV with the scan rates from 10 to 500 mV sꢀ1 support
quasi-reversible electron transfer. Reversibility is illustrated by
the similarity in the forward and reverse SWVs (Fig. 5) [44]. Unity
of the Ipa/Ipc ratio with the scan rate and linear variation of the Ipc
with square root of the scan rates indicated the purely diffusion
at 524 nm can characterize
a
metal-based reduction of
[AcO-MnIIPcꢀ2] to [AcO-MnIPcꢀ2] species (Fig. 4b and inset = i)
[34,41–43]. These two different changes may be due to removing
of the axial acetate ion after the first reduction process and estab-

3316
A. Lütfi Ug˘ur et al. / Polyhedron 29 (2010) 3310–3317
These spectral changes characterize the formation of [CoIPcꢀ2 1ꢀ
]
species under the applied potential at ꢀ0.40 V (Fig. 6a) [37,45–
47]. This process gives well-defined isosbestic points at 566 and
750 nm in the spectra and a color change from bluish green
(x = 0.279 and y = 0.342) to yellowish green (x = 0.367 and
y = 0.418) as shown in the chromaticity diagram (Fig. 6d). As
shown in Fig. 6b, the Q band at 707 nm decreases without shift
while a new broad band is recorded at 542 nm under the con-
trolled potential application at ꢀ1.60 V. These spectral changes
are characteristic of the ring-based reduction of [CoIPcꢀ2 1ꢀ
]
to
[CoIPcꢀ3 2ꢀ
]
species. Fig. 6c represents the spectral changes during
the first oxidation process of the complex. During 0.80 V potential
application, decreasing of the Q band without shifting and increas-
ing absorption of the regions at around 520 and 780 nm indicate
the Pc ring-based process and assigned to [CoIIPcꢀ2]/[CoIIPcꢀ1 1+
[37,45–47][37,45-47]. Color changes during the reduction and oxi-
dation processes are represented in Fig. 6d.
]
Fig. 5. CV (at 0.100 mVsꢀ1) and SWVs of 4 (CoPc) recorded with SVW parameters:
step size = 5 mV; pulse size = 100 mV; frequency = 25 Hz.
4. Conclusion
controlled electron transfer mechanism of the process. Other redox
processes have also quasi-reversible electron transfer characters.
Assignments of the redox couples are performed with spectroelect-
rochemical measurements. Fig. 6 represents in situ UV–Vis spectral
changes and in situ recorded chromaticity diagram of 4 in DCM/
TBAP during the potential application at the potentials of the redox
processes. During the first reduction process, while the Q band
shifts from 670 to 707 nm with increasing, a new band enhances
at 468 nm. Moreover the B band at 308 nm increases in intensity.
This work has described the synthesis, spectral (metal free
phthalocyanine, 2), electrochemical, spectroelectrochemical and
electrocolorimetric properties of 4-(tetra[4-(thiophen-3-yl)-phen-
oxy]phthalocyaninato) manganese (III) (3) and 4-(tetra[4-
(thiophen-3-yl)-phenoxy]phthalocyaninato) cobalt (II) (4). Both
complexes have good solubility and are monomeric in solutions.
The Pcs reported in this study can be applied as efficient candidates
for solution studies requiring monomeric form of these materials.
Fig. 6. In situ UV–Vis spectral changes of 4. (a) Eapp = ꢀ0.40 V. (b) Eapp = ꢀ1.60 V. (c) Eapp = 0.80 V. (d) Chromaticity diagram (each symbol represents the color of electro-
generated species; h: CoIIPcꢀ2, s: CoIPcꢀ2, 4: CoIPcꢀ3, q: CoIIPcꢀ1
.

A. Lütfi Ug˘ur et al. / Polyhedron 29 (2010) 3310–3317
3317
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Acknowledgment
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