Functional fluoro substituted tetrakis-metallophthalocyanines: Synthesis, spectroscopy, electrochemistry and spectroelectrochemistry

Article abstract of DOI:10.1016/j.jfluchem.2008.05.014

In this study, electron-withdrawing fluoro-functional ligand and its tetrakis 2,9,16,23-4-(2,3,5,6-tetrafluoro)-phenoxy-phthalocyaninatometal (II) complexes, (ZnPcOBzF₁₆, CuPcOBzF₁₆ and CoPcOBzF₁₆) (Bz: benzene) which are

Full text of DOI:10.1016/j.jfluchem.2008.05.014

Journal of Fluorine Chemistry 129 (2008) 662–668
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Functional fluoro substituted tetrakis-metallophthalocyanines: Synthesis,
spectroscopy, electrochemistry and spectroelectrochemistry
b
c
Armag˘an Gu¨nsel a, Mehmet Kandaz a, , Atıf Koca , Bekir Salih
*
a Department of Chemistry, Sakarya University, 54140 Esentepe, Sakarya, Turkey
b Chemical Engineering Department, Engineering Faculty, Marmara University, 34722 Go¨ztepe, Istanbul, Turkey
c Department of Chemistry, Faculty of Science, Hacettepe University, Beytepe Campus, Ankara 06532, Turkey
A R T I C L E I N F O
A B S T R A C T
Article history:
In this study, electron-withdrawing fluoro-functional ligand and its tetrakis 2,9,16,23-4-(2,3,5,6-
Received 29 February 2008
Received in revised form 21 May 2008
Accepted 21 May 2008
tetrafluoro)-phenoxy-phthalocyaninatometal (II) complexes, (ZnPcOBzF16, CuPcOBzF16 and CoPcOBzF16
)
(Bz: benzene) which are organo-soluble have been prepared. Their structures were confirmed by
elemental analysis, FT-IR, 1H NMR, UV/vis and MS (Maldi-TOF) spectral data. Electron-withdrawing
fluorine atoms on 2,3,5,6-position of benzene at the peripheral sites increases the solubility of the
tetrakis-metallophthalocyanines. The cyclic voltammetry and differential pulsed voltammetry of the
complexes show that while CuPcOBzF16 and ZnPcOBzF16 give ligand-based reduction and oxidation
processes, CoPcOBzF16 gives both ligand and metal-based redox processes, in harmony with the common
MPc complexes. Spectroelectrochemical measurements confirm the assignments of the complexes.
ß 2008 Elsevier B.V. All rights reserved.
Available online 29 May 2008
Keywords:
Phthalocyanines
Fluorine
Electron-withdrawing
Maldi-TOF
Aggregation
Spectroelectrochemistry
1. Introduction
on the Pc ring results in both the valence and conduction band
energies being further lowered. Thus, MPcFn (n: number of
Phthalocyanines derivatives show interesting chemical and
physical properties [1,2]. Therefore, excellent technologies
have been developed around these functional materials in the
last decade by facile substitution on the periphery (a, b, and g)
[3–6]. Due to their extended planar hydrophobic aromatic
surface, phthalocyanine molecules can interact with each other
fluorine atoms) exhibits n-type behavior, while unsubstituted
phthalocyanines possess p-type due to doping with electron-
accepting molecules [18]. These unusual properties of MPcFn have
led scientists to expose their chemistry to use in a number of
different industrial applications [19].
The goal of electrochemical study is to investigate the effect of
electron-withdrawing atoms on phthalocyanine which has the
potential to be an n-type Pc. It is known that the reduction and
oxidation processes of the phthalocyanines are shifted to more
positive potentials by the electron-withdrawing effect of these
types of substituents [1].
Here, we report the synthesis and characterization of 40-
(2,3,5,6-tetrafluorophenoxy)-1,2-dicyanobenzene and its metal-
lophthalocyanines (ZnPcOBzF16, CuPcOBzF16, and CoPcOBzF16). To
extend the application of the complexes we also investigate the
electrochemical properties of the designed complexes.
by attractive
p–p* stacking interactions. The interactions of
phthalocyanines affect aggregation and solubility tendencies
both in solution and in the solid state [7–10]. Nevertheless, it is
difficult to melt and dissolve for most of them, which limits their
applications in many fields [11]. The solubility of the phthalo-
cyanines (Pcs) can be improved significantly with increasing the
steric interactions in the Pc units having electron-withdrawing (–
F, –Cl, –Br, –NO2, etc.), and electron-donating (–NH2, Ar–S–, RO–,
etc.) bulky or long chain groups [11–16]. Metal phthalocyanines
bearing fluorine atoms are currently receiving a great deal of
attention due to their high thermal and chemical stability; they
also possess interesting electron-transporting characteristics
[17]. By placing stronger electron-withdrawing fluorine atoms
2. Experimental
2,3,5,6-Tetrafluorophenol, diethylether, tetrahydrofuran (THF)
tetrabutyl ammonium tetrafluoroborate (TBATBF4), (CuCl2,
Zn(O2CMe)2 or CoCl2) were purchased from Aldrich Chemical Co
and used as received. THF was distilled from anhydrous CaCl2 and
* Corresponding author. Fax: +90 264 295 59 50.
E-mail address: mkandaz@sakarya.edu.tr (M. Kandaz).
0022-1139/$ – see front matter ß 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2008.05.014

A. Gu¨nsel et al. / Journal of Fluorine Chemistry 129 (2008) 662–668
663
acetophenone. 4-Nitrophthalonitrile was prepared according to
2.4. Synthesis
the procedure in literature [20]. Chromatography was performed
with silica gel from Aldrich. All reactions were carried out under
dry N2 atmosphere. Purity of the products was tested in each step
by TLC (Silica gel, CHCl3, Hexane, and MeOH). FT-IR (Thin Solution
Film) were recorded on ATI UNICOM-Mattson 1000 Spectro-
photometer. Elemental analysis (C, H and N) was performed at the
instrumental Analysis Laboratory of Marmara University. Routine
UV/vis spectra were recorded on an Agillent Model 8453 diode
array spectrophotometer. 1H NMR and 13C NMR spectra were
recorded on a Bruker 300 spectrometer instruments. Multiplities
are given as s (singlet), d doublet), t (triplet).
2.4.1. 4-(2,3,5,6-Tetrafluorophenoxy)-1,2-dicyanobenzene (1)
2,3,5,6-Tetrafluorophenol (1.04 g, excess 10%) and 4-nitroph-
tlaonitrile (1.0 g, 5.78 mmol) were dissolved in dry dimethyl-
formamide (DMF) and heated at 40 8C in N2 atmosphere for 1 h.
Then finely ground anhydrous K2CO3 (1.20 g; excess) was added
portionwise to this mixture over 0.5 h. After the reaction mixture
was stirred efficiently under N2 for 30 h, the mixture was cooled
to room temperature. Then it was poured in to ca. 200 cm3 ice-
water. The creamy precipitate thus formed was washed
with water until the filtrate was clear. The crude product was
dissolved in chloroform and washed with 5% NaHCO3 to remove
starting uncreated compounds. The creamy solution was then
dried with anhydrous Na2SO4, and filtered. It was chromato-
graphed over a silica gel column using a mixture of CHCl3:MeOH
(100/5) as eluent, giving a powder solid, 40-(2,3,5,6-tetrafluor-
ophenoxy)-phthalonitrile, 1, giving a powder solid. Finally, the
pure powder was dried in a vacuum. Yield: 1.28 g (75.84%);
mp = 141 8C; Anal. Calcd. For C14H4F4N2O (292 g/mol): C, 57.53;
H, 1.36; N, 9.59%. Found: C, 57.15; H, 1.29; N, 9.22%. FT-IR (Thin
film, disc) nmax (cmꢀ1): 3083, 3052 (Ar–CH), 2236 (CBB N), 1602
(C C), 1517 (st), 1483 (st), 1358 (C–F), 1230 (Ar–O–Ar), 935, 882,
2.1. Electrochemical method
The cyclic voltammetry (CV), differential pulse voltammetry
(DPV), and controlled potential coulometry (CPC) measurements
were carried out with Gamry Reference 600 potentiostat/
galvanostat controlled by an external PC and utilizing a three-
electrode configuration at 25 8C. The working electrode was a Pt
disc with a surface area of 0.071 cm2. The surface of the working
electrode was polished with a diamond suspension before each
run. A Pt wire served as the counter electrode. Saturated calomel
electrode (SCE) was employed as the reference electrode and
separated from the bulk of the solution by a double bridge.
Ferrocene was used as an internal reference. Electrochemical
grade tetrabutylammonium perchlorate (TBAP) in extra pure
dichloromethane (DMSO) was employed as the supporting
electrolyte at a concentration of 0.10 mol dmꢀ3. High purity
N2 was used to remove dissolved O2 at least 15 min prior to each
run and to maintain a nitrogen blanket during the measure-
ments. IR compensation was also applied to the CV scans to
further minimize the potential control error.
792, 713, 505. 1H NMR (DMSO-d6)
8.22 (dd, H, ortho to CN), 8.00 (dd, H, meta to CN), 6.90 (ortho to
Ar–C–F); 13C NMR ([d6]-DMSO):
= 163.2 (Ar–O–Ar), 149.3 (Ar–
d: 8.31 (s, H, ortho to Ar–C–S),
d
C–F), 148.8 (Ar–C–F), 147.3 (Ar–C–F), 147.3 (Ar–C–F), 140.7 (Ar–
C–O), 135.2 (Ar–C– ortho to Ar–C–CN), 134.2 (Ar–C, ortho to Ar–
C–CN), 131.3 (Ar–C– ortho to CN), 121.8 (Ar–C– ortho to CN),
120.0 (Ar–C– meta to CN) 116.1 (Ar–C– ortho to CN), 114.6 (Ar–
CN), 101.0 (Ar–C, ortho to Ar–C–F), 40.8 (DMSO). EI/MS: m/z (%):
292.3 (65) [M+].
The spectroelectrochemical measurements were carried out
with an Ocean-optics QE65000 diode array spectrophotometer
equipped with the potentiostat/galvanostat utilizing a three-
electrode configuration of thin-layer quartz spectroelectrochem-
ical cell at 25 8C. The working electrode was transparent Pt gauze.
Pt wire counter electrode separated by a glass bridge and a SCE
reference electrode separated from the bulk of the solution by a
double bridge were used.
2.4.2. 2,9,16,23-Tetrakis-4-(2,3,5,6-tetrafluoro)phenoxy-
phthalocyaninatozinc(II) (ZnPcOBzF16) (2)
A mixture of compound 1 (0.15 g; 0.51 mmol), anhydrous
Zn(O2CMe)2 (0.04 g; 0.24 mmol), dry quinoline (ꢁ1 cm3), and DBU
(0.05 cm3) in a sealed tube was heated with stirring at 170–180 8C
for 8 h under N2 atmosphere. The deep green-blue product was
cooled to room temperature and then the waxy solid was washed
successively with MeCN and MeOH to remove any inorganic and
organic impurities until the filtrate was clear. Finally the blue
product was isolated by silica gel column chromatography with
CHCl3 and then with THF/CHCl3 (1:2, v/v) as eluent and then dried
in vacuo. This product is soluble in CH2Cl2, CHCl3, DMF, DMSO and
more soluble in acetone and THF.
2.2. Maldi mass spectrometry
Mass spectra were acquired on a Voyager-DETM PRO Maldi-TOF
mass spectrometer (Applied Biosystems, USA) equipped with a
nitrogen UV-laser operating at 337 nm. Spectra were recorded
both in linear and reflectron modes with average of 50 and 100
shots for linear and reflectron modes.
Yield: 0.025 g (15.90%); mp > 200 8C; Anal. Calcd. For
C
56H16F16N8O4Zn (1233 g/mol): C, 54.50; H, 1.30; N, 9.08. Found:
C, 54.09; H, 1.31; N, 8.78%. FT-IR (KBr thin film)
n
(cmꢀ1): 3080 (w,
broad, Ar–H), 1718 (vw), 1639, 1608 (C C), 1521, 1487 (st, C–F),
1396, 1338, 1271, 1209 (Ar–S–Ar), 1122, 1019, 1068, 943 (st), 833.
2.3. Maldi sample preparation
UV/vis (CHCl3,
lmax/nm (log e): 672 (4.16), 637 (1.42, agg), 608
a
-Cyano-4-hydroxycinnamic acid (CHCA) and dithranol (1,8-
(1.25), 346 (2.96); MS (Maldi-TOF, ditranol as matrix): m/z (100%):
1232.34 [M+H]+.
dihydroxy-10H-anthracen-9-one) Maldi matrix were used and
prepared in chloroform at a concentration of 20 mg/mL for 2, 3 and
4. Maldi samples were prepared by mixing sample solutions (4 mg/
mL) with the matrix solution (1:10, v/v) in a 0.5 mL eppendorf1
2.4.3. 2,9,16,23-Tetrakis-4-(2,3,5,6-tetrafluoro)phenoxy)
phthalocyaninatocopper(II) (CuPcOBzF16) (3)
micro tube. Finally 1
sample plate, dried at room temperature and then analyzed.
Cyano-4-hydroxycinnamic acid (CHCA) (20 mg/mL in acetonitrile)
matrix for 4 was prepared. Maldi samples were prepared by mixing
complex (2 mg/mL in acetonitrile) with the matrix solution (1:10,
v/v) in a 0.5 mL eppendorf1 micro tube. Finally 1
m
L of this mixture was deposited on the
A similar preparation method used for the complex 2 was used
to obtain blue-powder of 3 starting with a mixture of 1 (0.15 g;
0.50 mmol), anhydrous CuCl2 (ꢁ0.04 g; 0.24 mmol) and DBU
(0.05 cm3) in dry quinoline (ꢁ1 cm3). Further purification was
carried out by column chromatography with silica gel (eluent:
CHCl3, and then THF/CHCl3 (1:2, v/v)) and dried in vacuo. Complex
3 is soluble excellent in acetone, THF, soluble moderately in CH2Cl2
and CHCl3, and slightly soluble in DMF and DMSO.
a
-
mL of this mixture
was deposited on the sample plate, dried at room temperature and
then analyzed like literatures [21,22].

664
A. Gu¨nsel et al. / Journal of Fluorine Chemistry 129 (2008) 662–668
Yield: 0.020 g (12.74%); mp > 200 8C; Anal. Calcd. For
56H16F16N8O4Cu (1231.5 g/mol): C, 54.56; H, 1.30; N, 9.09%.
C
Found: C, 53.95; H, 1.33; N, 8.77%. FT-IR (KBr thin film) n :
max/cmꢀ1
3033 cmꢀ1 (w, Ar–H, broad), 1627 (w), 1602 (C C), 1483 (st), 1434,
1380, 1309, 1234 (st, –C–F), 1141, 1097, 964 (st), 916, 823; UV/vis
(in THF),
lmax/nm: 670 (4.65), 636 (1.40, agg), 605 (1.25), 345
(2.72); MS (Maldi-TOF, ditranol as matrix): m/z (100%): 1231.23
[M+H]+.
2.4.4. 2,9,16,23-Tetrakis-4-(2,3,5,6-tetrafluoro)phenoxy)
phthalocyaninatocobalt(II) (CoPcOBzF16) (4)
A similar preparation method to that used for compounds 2 and
3 was used to obtain blue-powder of 4 starting from a mixture of 1
(0.15 g; 0.5 mmol) anhydrous CoCl2 (0.04 g; 0.24 mmol) and DBU
(0.05 cm3) in dry quinoline (1 cm3). Compound 4 is soluble in
CH2Cl2, CHCl3, acetone and THF, and less soluble in DMF and
DMSO. Further purification was carried out by column chromato-
graphy with silica gel (eluent: CHCl3/MeOH; 10/1, and then THF)
and dried in vacuo.
Yield: 0.29 g (46%); mp > 200 8C; Anal. Calcd. For C56H16F16N8O4
Co (1227 g/mol): C, 54,77; H, 1.30; N, 9.12%. Found: C, 52.75; H, 1.31;
N, 8.04%. FT-IR (KBr thin film) n
/cmꢀ1: 3074 cmꢀ1 (w, Ar–H, broad),
1635 (w), 1614 (C C), 1517 (st), 1483 (st), 1409 (st, –C–F), 1332,
1269, 1217 (Ar–S–Ar), 1173, 1093 (st), 945, 827, 748, 711; UV/vis
Scheme 1. Synthetic route of 4-(2,3,5,6-tetrafluorophenoxy)-1,2-dicyanobenzene
and its metallo phthalocyanine (M = Zn(II) and Cu(II)). (i) 2,3,5,6-Tetrafluorophenol
and 4-nitrophthalonitrile and K2CO3 in DMF at 40 8C for 24 h. (ii) Anhydrous
Zn(acac)2, and CuCl2, DBU, quinoline.
(THF), lmax/nm:660 (4.48), 601, 339 (4.13);MS(Maldi-TOF, ACCAas
matrix): m/z (100%): 1227.40 [M+H]+.
3. Results and discussion
aromatic carbon atoms between 110 and 160 ppm in the spectrum
are the most instinctive indicator signals for 1. It is likely that the
rather broad bands in the case of especially 2 were probably due to
both chemical exchange associated with the aggregation–disag-
gregation equilibria that occurs at high concentrations used in the
NMR measurements. Another reason is that the product obtained in
these reactions is a mixture of four positional isomers, which are
expected to show chemical shifts only slightly differing from each
other [4,7–9,15,21].
3.1. Synthesis and characterization
Novel copper, zinc and cobalt phthalocyanines (2, 3 and 4) were
prepared by the templated cyclization reaction from 4-(2,3,5,6-
tetrafluorophenoxy)-1,2-dicyanobenzene and anhydrous CuCl2,
Zn(O2CMe)2 or CoCl2 in the presence of high boiling quinoline
solvent at 180–185 8C under N2 atmosphere in the presence of 1,8-
diazabicyclo [5.4.0] undec-7-ene (DBU) as a strong base and as
shown in Scheme 1. The blue cyclotetramerization products, MPc’s
(M = Zn, Cu and Co) were purified by column chromatography in
moderate yield (15.90% for 2, 12.74% for 3 and 15.23 for 4),
respectively. The most obvious feature of newly synthesized
phthalocyanines is their solubility in various solvents such as,
benzene, chloroform, acetone and THF.
Elemental analysis results and the spectral data (1H NMR, FT-IR
and Maldi-TOF-MS) of the new products are consisted with the
assigned formulations. The blue phthalocyanine products (M = Zn,
Cu and Co) were isolated as a mixture of isomers as expected
[5,21,22]. The presence of isomers could be verified with slight
broadening encountered in the UV–vis absorption bands and
broadening in the 1H NMR when compared with those of octa-
Two principle
p
–
p
* transitions are seen for Pcs: a lower energy
* transition from highest occupied
Q band (ꢁ550–700 nm,
p–p
molecular orbital (HOMO) to lowest unoccupied molecular orbital
(LUMO) of the complexes) and a higher energy B band (ꢁ300–
350 nm, deeper
p–p* transition from the highest occupied MO’s
(a1u and a2u) to the LUMO (eg)) [6]. It is known that the effect of O-
substitution on the periphery when compared with those of S-
substituted derivatives for all phthalocyanines was a more-shift in
these intense Q bands to shorter wavelengths [5–7,11,14]. The Q
band absorptions in the UV/vis absorption spectra of the
phthalocyanines (2, 3 and 4) were observed as single Q bands
with high intensity due to a single
p–p* transition at 672, 670 and
660 nm respectively with shoulders at slightly higher energy side
of the Q band for each complexes as seen in Fig. 1. The absorption
positions of the synthesized compounds are dependent on the
ionic radius of the metal center.
substituted phthalocyanines composed of
a single isomer
[5,13,15,21,22]. All the analytical and spectral data are consistent
with the predicted structures. The six peripheral fluoro atoms
increase the solubility of the complexes in halogenated solvents
and in acetone and THF.
3.2. Maldi-TOF mass spectra
The FT-IR spectra were used to identify strong –C–F stretching
band at 1480–1485 cmꢀ1 on the periphery band with small shift
compared to the compound 1 and strong disappearance of –CN
band at 2236 cmꢀ1 in 1 after phthalocyanine formation. Aliphatic,
aromatic –C–H, C–H peaks at above and below 3000 cmꢀ1 and the
rest of the spectra is closely similar to that of compound 1 and
diagnosed easily.
The 1H NMR spectra of 2 was almost identical with starting
compound 1 except broadening and small shifts. The aromatic
protons in the lower field region of the 1H NMR of 1 and 14 different
Positive ion Maldi-MS spectrum of 2 and 3 is given in Figs. 2 and
3. Many different Maldi matrices were tried to find intense
molecular ion peak and low fragmentation under the Maldi-MS.
conditions for this complex. a-Cyano-4-hydroxycinnamic acid and
dithranol (1,8-dihydroxy-10H-anthracen-9-one) Maldi matrix
yielded best Maldi-MS spectrum as seen in Figs. 2 and 3. The
peak group representing the protonated molecular ion of the 2 was
observed starting with 1232 Da mass and finishing 1237 Da
following each other by 1 Da mass differences. This type of mass
distribution results from the isotopic mass distribution of carbon

A. Gu¨nsel et al. / Journal of Fluorine Chemistry 129 (2008) 662–668
665
Fig. 3. Positive ion and reflectron mode Maldi-MS spectrum of 3 was obtained in
dithranol (1,8-dihydroxy-10H-anthracen-9-one) Maldi matrix using nitrogen laser
accumulating 50 laser shots. Inset spectrum shows expanded molecular mass
region of the complex.
Fig. 1. UV–vis spectra of metallo phthalocyanine 2, 3 and 4 in THF.
complexes, Maldi-MS spectra were obtained most efficiently using
only dithranol Maldi matrix compared to the other novel Maldi
matrices. Mainly protonated molecular ion peaks and the dithranol
peak at around 227 Da were characterized for all copper and zinc
complexes with really low intensity of the other peaks in some
cases. Experimental isotopic peaks of protonated molecular ion
peaks shown as inset in Maldi mass spectrum of each complex
were compared the theoretical calculated isotopic peak distribu-
tions of protonated molecular ion peaks. It was concluded that all
experimental isotopic peak distributions of protonated molecular
ions were overlapped completely with their theoretical calculated
isotopic peak distributions. These results showed that complexes
were characterized precisely by Maldi-MS. All Maldi-MS results
showed that dithranol was a suitable matrix for these types of
metal complexes to get clearer Maldi-MS spectrum and also it
could be concluded that metal complexes of these ligands were
more stable in dithranol matrix. Beyond the protonated molecular
ion peak of the 4, Maldi spectrum of the 4 showed very clear and no
fragmentations in Maldi-MS. In the case of 4, protonated molecular
ion peak was observed at 1227 with the other three peaks
following the each other by 1 Da mass difference. This peak group
is because of the isotopic distribution of cobalt and carbon in the
complex structure [22]. The best Maldi-MS spectrum of this
(mainly 13C) and the isotopes of 2. In the Maldi-MS spectrum of the
2, beside the protonated molecular ion peak, no fragment ion was
observed. This was pointed out that no leaving group was available
from this complex and the complex was very stable under the
Maldi matrix conditions and also under the laser energy. For the
same complex very clear Maldi-MS spectrum was obtained in
dithranol matrix with only protonated molecular ion peak and
dithranol matrix peak. This result showed that the complex was
more stable in dithranol matrix compared to the other novel Maldi
matrices. Also clear Maldi spectrum showed that complex was
synthesized successfully and separated efficiently. Experimental
isotopic peak distributions of protonated molecular ion peak of this
complex were overlapped exactly with its theoretical calculated
isotopic peak distributions. Protonated molecular ion peak was
observed at 1231 Da with the other isotopic peaks mainly resulted
from the isotopic distribution of 3 and carbon which were exactly
overlapped with the mass of the 3 calculated theoretically from the
elemental composition of 3. Beside the protonated molecular ion
peak of the complex, no peak was observed between 500 and
1500 Da mass range representing the any other impurity and the
fragment ions under the laser shots. Beyond the protonated
molecular ion peak of the 3, Maldi spectrum of the 3 showed very
clear and no fragmentations in Maldi-MS. In the case of 3,
protonated molecular ion peak was observed at 1231 with the
other three peaks following the each other by 1 Da mass difference
[21,22]. For all high resolved Maldi-MS spectra of copper and zinc
complex was obtained using
a-cyano-4-hydroxycinnamic acid
(ACCA) with only one fragment peak at low intensity around
1227 Da mass. If 3-indole acrylic acid (IAA) and the other
conventional matrices (except ACCA) were used, more fragmenta-
tion and broad peaks could be obtained and interfering the quality
of mass spectra.
3.3. Electrochemical measurements
The solution redox properties of the complexes (2–4) were
studied using CV, DPV and DPSC techniques in DCM on a platinum
electrode. Table 1 lists the assignments of the couples recorded and
the estimated electrochemical parameters, which included the
half-wave peak potentials (E1/2), and HOMO–LUMO gaps (DE1/2).
CV and DPV studies reveal that 2 (ZnPc) and 3 (CuPc) give only
three reduction and two oxidation ring-based redox couples with
in the potential windows of the DMSO/TBAP electrolyte and Pt
electrode system. The complexes 2 and 3 give very similar
voltammetric behavior accompanied by the slight potential shifts
corresponding to the different metal center of the complexes
(Table 1). Fig. 4 shows the CV and DPV of 2 as a representative of
the complexes. For the couples II–IV, anodic to cathodic peak
Fig. 2. Positive ion and reflectron mode Maldi-MS spectrum of 2 was obtained in
dithranol (1,8-dihydroxy-10H-anthracen-9-one) Maldi matrix using nitrogen laser
accumulating 50 laser shots. Inset spectrum shows expanded molecular mass
region of the complex.
separations (
D
Ep) changed from ca. 60 to 150 mV with the scan
Ep changing from 60 to 110 mV was
rates from 10 to 500 mV sꢀ1
(
D

666
A. Gu¨nsel et al. / Journal of Fluorine Chemistry 129 (2008) 662–668
Table 1
Voltammetric data of the complexes with the related MPcs for comparison
Complex
Redox processes
a
I
II
III
IV
V
IV
D
E1/2
Ref.
0.68c
0.70
ꢀ0.80
ꢀ1.17
ꢀ1.05
ꢀ1.27
ꢀ1.03
ꢀ1.06
ꢀ1.27
ꢀ1.16
ꢀ0.84
ꢀ2.00c
ꢀ1.85c
ꢀ1.65c
ꢀ1.25
ꢀ1.90
1.58
1.53
0.86
0.53
1.10
1.47
1.60
0.82
1.47
tw
b
2
E1/2 (V vs. SCE)
1.08
3
E1/2 (V vs. SCE)
1.05c
ꢀ0.75
tw
4
E1/2 (V vs. SCE)
0.44 (0.35)d
0.32
ꢀ0.42 (ꢀ0.39)d
ꢀ0.21
ꢀ1.95c
tw
b
CoPce
CuPcf
CuPcg
ZnPch
CoPci
ZnPcj
E1/2 (SCE) in THF
0.76
[28]
[22]
[29]
[30]
[31]
[32]
E1/2 (SCE) in DCM
E1/2 (Fc+/Fc) in DCM
E1/2 (SCE) in DCM
E1/2 (Ag/AgCl) in DCM
E1/2 (SCE) in DMF
0.15
ꢀ0.95
0.56
ꢀ0.91
0.85
ꢀ0.75
0.89
1.16
0.42
ꢀ0.40
0.48
ꢀ0.99
tw: this work.
a
D
E1/2 = E1/2 (first oxidation) ꢀ E1/2 (first reduction) = HOMO–LUMO gap for metal-free and metallophthalocyanines having electro-inactive metal center (metal to ligand
(MLCT) or ligand to metal (LMCT)) charge transfer transition gap for MPc having redox active metal center.
b
E1/2 = (Epa + Epc)/2 at 100 mV sꢀ1 (Epc for reduction, Epa for oxidation for irreversible processes).
c
Recorded by differential pulse voltammetry.
d
Ep of the wave of aggregated species.
e
Substituted with tetrakisdiethoxymalonyl groups.
f
Substituted with propane 1,2-diolsulfanyl groups.
g
Substituted with tetra(dihexoxymalonyl) groups.
h
Substituted with tetrapentafluorobenzyloxy groups.
i
Substituted with tetrakis (benzylmercapto) groups.
j
Substituted with tetra-{2-(2-thienyl)}ethoxy groups.
obtained for the ferrocene reference), indicate the changing the
electron transfer reactions from reversible to quasi reversible
character with increasing scan rates. Reversibility is also illustrated
by the similarity in the forward and reverse DPV scans (Fig. 4(dot
lines)). The value of Ipa/Ipc for the couples II–IV are unity at all scan
rates and the peak currents increases linearly with the square root
of scan rates for scan rates ranging from 10 to 500 mV sꢀ1
,
suggesting purely diffusion controlled mass transfer for all couples
in Fig. 4 [23–27].
The complexes 2 and 3 have both redox inactive metal centers.
Therefore, in situ UV/vis spectral changes of 2 are given as a
representative of the spectral chances of MPc having redox inactive
metal center. As shown in Fig. 5A, there are two distinct
spectroscopic changes are recorded during the potential applica-
tion at the first reduction process of the complex 2. First of all,
while the intensity of Q band at 680 nm do not change, the band at
630 nm assigned to the aggregated species decrease in intensity
(inset in Fig. 5A). These changes support the aggregation–
disaggregation equilibrium of 2. Then as shown in Fig. 5A, while
the intensity of Q band at 680 nm decreases without shift, two new
bands in the MLCT regions at 450, and 576 nm are recorded.
Change in the intensity of the Q band without shift and observation
Fig. 4. CVs (solid lines) and DPVs (dot lines) of 2 (5.0 ꢂ 10ꢀ4 mol dmꢀ3). For CV, scan
rate: 0.100 mV sꢀ1. For DPV, pulse width: 50 ms; pulse height: 100 mV; step height:
Fig. 5. In situ UV/vis spectral changes of 2. (A) Eapp = ꢀ0.90 V. (B) Eapp = ꢀ1.20 V. (C)
Eapp = 0.75 V.
5 mV; step time: 100 mV; scan rate: 50 mV sꢀ1
.

A. Gu¨nsel et al. / Journal of Fluorine Chemistry 129 (2008) 662–668
667
of the new bands in the MLCT regions are characteristics of ring-
based processes [23,27–35]. Color change from green to blue
support the generation of monoanionic [Zn (II) Pc (ꢀ3)]ꢀ1 species
during the process. The process has isosbestic points at 321,
411, 641, and 714 nm in the spectra. Further reduction of the
monoanionic [Zn(II)Pc(ꢀ3)]ꢀ1 species causes to decrease in the
intensity of the Q band and increase in the intensity of the band at
576 nm (Fig. 5B). B band shift from 342 to 330 nm by decreasing
at the same time during this process. The process has isosbestic
points at 320, 452, and 640 nm in the spectra. These spectro-
equilibria of the complex. While the solution is diluted, peak
current of the wave III0 assigned to the aggregated species gets
smaller much more than that of III, however it is present even in
very diluted solution [1,24,25].
Spectroelectrochemical measurements (SE) were used to
confirm some of the assignments of the complex 4 in the CVs.
The experiments were performed using optically transparent thin-
layer quartz electrochemical cell. Fig. 7A shows the in situ UV–vis
spectral changes during the controlled potential reduction of 4 at
ꢀ0.50 V vs. SCE corresponding to the redox process labeled III and
III0 in the CV (Fig. 6). While the intensity of the absorption of the Q
band corresponding to the neutral [Co(II)Pc(ꢀ2)] species decreases
at 659 nm, a new Q band corresponding to the electro-generated
reduced [Co(I)Pc(ꢀ2)]ꢀ1 species at 704 nm appears. At the same
time a split bands at 434 and 470 nm grows, while the B band
increases slightly in intensity with a blue shift from 330 to 317 nm
during this process. Moreover, broadness of the Q band due to
the aggregation decreases during this potential application by
decrease of the adsorption at around 630 nm. The spectral changes
scopic changes are assigned to the process, [Zn(II)Pc(ꢀ3)]ꢀ1
/
[Zn(II)Pc(ꢀ4)]ꢀ2. Color change from blue to light purple support
the generation of dianionic [Zn(II)Pc(ꢀ4)]ꢀ2 species during the
process. Fig. 5C shows the ligand-based oxidation processes of the
complex under 0.75 V potential application. Surprisingly all bands
decrease in intensity during this process, while the intensity of the
region at around 480 nm increase slightly. The process has
isosbestic points at 278, 433 and 534 nm in the spectra. These
spectroscopic changes indicate the formation of the [Zn(II)Pc(ꢀ1)]+
species, and then decomposition of the [Zn(II)Pc(ꢀ1)]+ species
during the 0.75 V potential application [23,30–35].
The complex 4 give four one-electron reduction processes
labelled as III at ꢀ0.42 V (III0 at ꢀ0.39 V), IV at ꢀ1.27 V, at ꢀ1.65 V
and ꢀ1.95 V and a one-electron oxidation processes labelled as II at
0.85 V (II0 at 1.25 V) vs. SCE at 0.100 V sꢀ1 scan rate (Fig. 6). The
assignments of the redox couples are confirmed below using
spectroelectrochemistry measurements. As shown in Fig. 6, the
first reduction and oxidation couples are split into two peaks. This
behavior is due to the aggregation of the complex in solution.
Dilution of the solution changes the aggregation–disaggregation
Fig. 6. CVs and DPVs of 4 (5.0 ꢂ 10ꢀ4 mol dmꢀ3) at various scan rates (for DPV, pulse
width: 50 ms; pulse height: 100 mV; step height: 5 mV; step time: 100 mV; scan
rate: 50 mV sꢀ1).
Fig. 7. In situ UV–vis spectral changes of 4. (A) Eapp = ꢀ0.50 V. (B) Eapp = ꢀ1.35 V. (C)
Eapp = 0.60 V.

668
A. Gu¨nsel et al. / Journal of Fluorine Chemistry 129 (2008) 662–668
in Fig. 7A are typical of metal-based reduction in phthalocyanine
complexes. The shift of the Q band from 659 to 704 nm and
observation of new bands at 434 and 370 nm (MLCT) are
characteristic of metal-based processes [23,31–35]. Observation
of a split band between 400–500 nm and decrease of the Q band
broadness shows the aggregation desegregation equilibria present
in solution. As shown in Fig. 7A, the process at ꢀ0.50 V potential
applications occurred with clear isosbestic points at 290, 380, 556
and 686 nm in the spectra. The color of the solution is changed
from blue to green during the process. Change to the original
spectrum and color after the potential application at 0.00 V
indicates the reversibility of the process. During the controlled
potential reduction of 4 at ꢀ1.35 V vs. SCE corresponding to the
redox process labeled IV (Fig. 7B), the absorptions of the Q bands at
704 nm decreases in intensity without shift, while one of the split
bands at 495 nm increase in intensity. At the same time a broad
band increases at around 550 nm while the B band at 317 nm
decreases in intensity. The color of the solution is changed from
green to red during the process. Change to the original spectrum
and color after the potential application at ꢀ0.50 V indicates the
reversibility of the process. The process at ꢀ1.35 V vs. SCE potential
application has isosbestic points at 336, 393, 476 and 625 nm in
the spectra. The spectral changes in Fig. 7B are typical of ligand-
based reduction assigned to [Co(I)Pc(ꢀ2)]ꢀ1/[Co(I)Pc(ꢀ3)]ꢀ2 redox
process [23,31–35]. On potential application at 0.60 V, the
intensities of the Q bands increases with a red shift from 658 to
674 nm, while the broadness of the Q band gets sharper by
decrease of the absorption at around 600 nm (Fig. 7C). At the same
time while the B band shifts from 330 to 344 with decreasing, a
new band appears at 284 nm. The spectral changes in Fig. 7C,
especially shifting of the Q band with increasing are typical of
metal-based oxidation in phthalocyanine complexes and the
process is easily assigned to [Co(II)Pc(ꢀ2)]/[Co(III)Pc(ꢀ2)]+1 redox
process [23,31–35]. The process has isosbestic points at 293, 347,
484, and 662 nm in the spectra and blue to green color changes
upon the potential application at 0.60 V. Obtaining the original
color and spectrum after the potential application at 0.0 V shows
the reversibility of the process. During CPC studies, complete
electrolysis of the solution of the complexes at the end of the
solvent windows was achieved, and the time integration of the
electrolysis current was recorded. The CPC studies indicated that
the number of electrons transferred for each of the couples was
found to be approximately one.
central metal ions and by the peripheral substituents. The blue
shift of the complexes compared to the parent phthalocyanine was
due to fluorine group at the peripheral substituents. However,
stronger electron-withdrawing fluorine atoms on the Pc ring also
affect the electrochemical behavior of the complexes. The
approach described here may be useful for fabrication of the
highly soluble semiconductor phthalocyanine devices whose
conducting properties will be the subject of our future interest.
Acknowledgements
We thank the Research Funds of Sakarya University, State
Planning Organization (DPT-2004 P.No.: 2003K120970) and
¨
˙
TUBITAK (P.No.: TBAG 108T094; MAG-106M286).
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