Synthesis and characterization of novel 4-nitro-2-(octyloxy)phenoxy substituted symmetrical and unsymmetrical Zn(II), Co(II) and Lu(III) phthalocyanines

Article abstract of DOI:10.1016/j.poly.2007.08.015

Compounds 3 and 4 have been prepared by the reaction of 4-nitrocatechol 1 and 4-nitrophthalonitrile 2 by a common method, aromatic nucleophilic subtitution of the nitro group in 4-nitrophthalonitrile. Starting from 4 and 1-bromooctane, their alkylation reaction gave compound 5. Zn(II) 8, Co(II) 9 and Lu(III) 10 complexes were synthesized from the corresponding metal salts by the tetramerization of compound 5. Compound 7 was prepared by the statistical condensation of 5 and 4,5-bis(hexylthio)phthalonitrile 6 with CoCl₂ · 6H₂O in dry dimethylformamide. The new compounds were characterized by FT-IR, UV/Vis, NMR and mass spectra. The electrochemical properties of the complexes were also investigated by cyclic voltammetry in non-aqueous medium. The effect of temperature on the dc conductivity and the impedance spectra of spin coated film of the compounds was investigated at temperatures between 295 and 433 K and in the frequency range 40-10⁵ Hz. Thermally activated conductivity dependence on temperature was observed for all compounds.

Full text of DOI:10.1016/j.poly.2007.08.015

Available online at www.sciencedirect.com
Polyhedron 26 (2007) 5432–5440
www.elsevier.com/locate/poly
Synthesis and characterization of novel
4-nitro-2-(octyloxy)phenoxy substituted symmetrical
and unsymmetrical Zn(II), Co(II) and Lu(III) phthalocyanines
a
a
b
a
¨
Duygu Kulac¸ , Mustafa Bulut , Ahmet Altındal , Ali Rıza Ozkaya ,
c
d,
*
¨
Bekir Salih , Ozer Bekarog˘lu
a
Department of Chemistry, Marmara University, Go¨ztepe 34722, Istanbul, Turkey
Department of Physics, Marmara University, Go¨ztepe 34722, Istanbul, Turkey
b
c
Department of Chemistry, University of Hacettepe, 06532 Ankara, Turkey
Department of Chemistry, Technical University of Istanbul, 34469 Maslak, Istanbul, Turkey
d
Received 10 May 2007; accepted 8 August 2007
Available online 27 September 2007
Abstract
Compounds 3 and 4 have been prepared by the reaction of 4-nitrocatechol 1 and 4-nitrophthalonitrile 2 by a common method, aro-
matic nucleophilic subtitution of the nitro group in 4-nitrophthalonitrile. Starting from 4 and 1-bromooctane, their alkylation reaction
gave compound 5. Zn(II) 8, Co(II) 9 and Lu(III) 10 complexes were synthesized from the corresponding metal salts by the tetrameriza-
tion of compound 5. Compound 7 was prepared by the statistical condensation of 5 and 4,5-bis(hexylthio)phthalonitrile 6 with
CoCl2 Æ 6H2O in dry dimethylformamide. The new compounds were characterized by FT-IR, UV/Vis, NMR and mass spectra. The elec-
trochemical properties of the complexes were also investigated by cyclic voltammetry in non-aqueous medium. The effect of temperature
on the dc conductivity and the impedance spectra of spin coated film of the compounds was investigated at temperatures between 295
and 433 K and in the frequency range 40–105 Hz. Thermally activated conductivity dependence on temperature was observed for all
compounds.
ꢀ 2007 Elsevier Ltd. All rights reserved.
Keywords: Phthalocyanine; Electrochemistry; Impedance spectra
1. Introduction
occurring macrocycles [1]. MPcs and their derivatives
are semiconductive organic materials that have been used
in various applications including chemical sensors, photo-
conductive agents, liquid crystals, non-linear optics,
electrocatalysis and other photoelectronic devices [1].
Unsymmetrically substituted Pcs possess very interesting
non-linear optical properties [2,3] and are important for
Langmuir–Blodgett films [4–6] and photodynamic therapy
of cancer [7]. Many Pcs are practically insoluble in com-
mon organic solvents and water. This minimizes their
applications. However, the solubility of unsubstituted
Pcs can be improved by introducing different kinds of
substituents, such as crown ethers, alkyl, alkoxy and
alkylthio, at the periphery of the Pcs [8]. The synthesis
of soluble Pcs provides them with new optical, electronic,
Phthalocyanines (Pcs) are well known colorants;
besides their intense colour and efficient energy absorp-
tion, more remarkable properties have been discovered
due to their 18 p-electron conjugated system. The past
several years have seen an increasing interest in the chem-
istry of metallophthalocyanines (MPcs), since these com-
pounds have been used as commercial dyes, optical and
electrical materials, catalysts and models for naturally
*
Corresponding author. Present address: Bilim Sokak, Kardesler Apt.,
No. 6/9, Erenko¨y, Istanbul, Turkey. Tel.: +90 216 359 01 30; fax: +90 216
386 08 24.
¨
E-mail address: obekaroglu@gmail.com (O. Bekarog˘lu).
0277-5387/$ - see front matter ꢀ 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2007.08.015

D. Kulac¸ et al. / Polyhedron 26 (2007) 5432–5440
5433
redox and magnetic properties which could increase the
field of possible applications [9,10]. The growing use of
Pcs as advanced materials during the last decade has
encouraged the synthesis of new materials [11] which dif-
fer in terms of the central metal ion and peripheral sub-
stituents [12].
The present paper reports for the first time the synthesis
and characterisation of 4-nitro-2-octyloxyphenoxy substi-
tuted symmetrical and unsymmetrical MPcs. The electrical
and electrochemical properties of the complexes are also
presented.
arated filtrate was treated with hydrochloridic acid (10%)
and the crude solid was filtered, washed with distilled
water and ethanol. Column chromatography of this
crude product on silica gel gave 4. Products 3 and 4 were
soluble in CHCl3, dimethylformamide (DMF), DMSO
and tetrahydrofurane (THF). Yield of 3: 0.60 g (11%).
M.p.: 193–196 ꢃC. IR (cmax/cmꢀ1 KBr disc): 3083 (Ar–
H), 2235 (–CN), 1588–1485 (–C@C–), 1246–1279 (Ar–
O–C), 1569–1350 (–NO2). 1H NMR (dH ppm,
400 MHz, DMSO): 8.31 (d, J = 2.73, Ar–H), 8.26 (dd,
J = 2.73, Ar–H), 8.20 (d, J = 8.58, Ar–H), 8.10 (d,
J = 8.58, Ar–H), 8.06 (d, J = 8.97, Ar–H), 7.90 (d,
J = 2.34, Ar–H), 7.86 (d, J = 2.73, Ar–H), 7.68 (dd,
J = 2.34, Ar–H). Yield of 4: 3.2 g (88%). M.p.: 213–
215 ꢃC. IR (cmax/cmꢀ1 KBr disc): 3037–3082 (Ar–H),
2223 (–CN), 1490–1598 (–C@C–), 1265–1136 (Ar–O–C),
1332–1525 (–NO2), 3276 (Ar–OH). 1H NMR (dH ppm,
500 MHz, DMSO): 8.14 (dd, J = 2.44, Ar–H), 8.09 (d,
J = 2.44, Ar–H), 8.07 (d, J = 8.97, Ar–H), 7.79 (d,
J = 2.93, Ar–H), 7.40 (dd, J = 2.45, Ar–H), 7.20 (d,
J = 8.79, Ar–H ), 11.6 (s, br, Ar–O–H). D2O Exc-
NMR (dH ppm, 500 MHz, DMSO): 8.12 (dd, J = 2.44,
Ar–H), 8.09 (d, J = 2.93, Ar–H), 8.04 (d, J = 8.79, Ar–
H), 7.72 (d, J = 2.44, Ar–H), 7.38 (dd, J = 2.93, Ar–
H), 7.18 (d, J = 9.28, Ar–H).
2. Experimental
2.1. Synthesis and characterization
All chemicals used were of reagent grade. The solvents
were dried, purified and stored over molecular sieves
˚
(4 A). Compounds 2 and 6 were prepared by the literature
methods [13,14]. Compound 1 was obtained from commer-
cial suppliers. The progress of the reactions was monitored
by TLC. Column chromotography was used for purifica-
1
tion of the complexes. H NMR spectra were determined
with a Varian Unity Inova 500 MHz NMR spectrometer
and a Varian Mercury-Vx 400 MHz NMR spectrometer.
IR spectra were recorded as KBr discs in the range 400–
4000 cmꢀ1 on a Shimadzu FTIR-8300 infrared spectrome-
ter. The electronic absorption spectra were measured in
CHCl3 with a Shimadzu UV-1601 UV/Vis spectrometer.
Mass spectra were acquired on a Voyager-DEꢁ 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 an average of 50 and 100 shots for linear and
reflectron modes, respectively. A a-cyano-4-hydroxycin-
namic acid (CHCA) MALDI matrix was used and pre-
pared in chloroform at a concentration of 20 mg/mL for
symmetrical Pcs 8 and 9. A 3-indole acrylic acid (IAA)
MALDI matrix was used for the unsymmetrical Pc 7.
The positive ion and linear mode spectrum of complex 10
could be obtained only in dithranol matrix. MALDI sam-
ples were prepared by mixing sample solutions (4 mg/mL)
with the matrix solution (1:10 v/v) in a 0.5 mL eppendorfꢂ
microtube. Finally 1 ll of this mixture was deposited on the
sample plate, dried at room temperature and then
analyzed.
2.1.2. Preparation of 4-(4-nitro-2-
(octyloxy)phenoxy)phthalonitrile (5)
About 0.282 g (1 mmol) of 4, 0.193 g (1 mmol) of 1-bro-
mooctane, 0.278 g (2 mmol) of anhydrous K2CO3 and tet-
rabutylammonium bromide in dry acetonitrile (40 ml) were
stirred at 80–85 ꢃC for 48 h under an argon atmosphere.
The mixture was cooled and evaporated to dryness. The
product was treated with glacial-acetic acid and then
flushed several times with water until the filtrate was neu-
tral. After that it was extracted with CH2Cl2. Finally, pure
5 was obtained by chromatography with silica gel using
CHCl3. Product 5 was soluble in CHCl3, CH2Cl2, DMF,
DMSO and THF. Yield: 0.30 g (76%). M.p.: 88–92 ꢃC
(Scheme 1). IR (cmax/cmꢀ1 KBr disc): 3082 (Ar–H), 2234
(–CN), 1484–1606 (–C@C–), 1292–1246 (Ar–O–C), 1347
1
and 1512 (–NO2), 2847–2932 (–CH2–, –CH3). H NMR
(dH ppm, 400 MHz, CDCl3): 8.23 (dd, J = 2.73, Ar–H),
8.08 (d, J = 2.73, Ar–H), 7.73 (d, J = 8.68, Ar–H), 7.21
(dd, J = 2.73, Ar–H), 7.18 (d, J = 2.34, Ar–H), 7.10 (d,
J = 9.36, Ar–H), 4.05 (t, J = 6.24, –OCH2), 1.40 (m,
–CH2–), 0.90 (t, J = 7.02, –CH3).
2.1.1. 3,4-Bis(3,4-dicyanophenoxy)nitrobenzene (3) and 4-
(3,4-dicyanophenoxy)-3-hydroxynitrobenzene (4)
2.1.3. 2-[4-Nitro-2-(octyloxy)phenoxy]-9,10,16,17,23,24-
hexakis(hexylthio)phthalocyaninato cobalt(II) (7)
About 2 g (12.90 mmol) of 1, 4.47 g (25.80 mmol) of 2
and 5.48 g (39.70 mmol) of K2CO3 in dry dimethylsulfox-
ide (DMSO) (30 ml) were stirred at 78–80 ꢃC for 24 h
under an argon atmosphere. Then, the reaction mixture
was poured into water. The precipitate that formed
was filtered, washed with cold water and dried in air.
The crude compound 3 was chromatographed on a silica
gel column with CHCl3 as the eluent. After that, the sep-
Compounds 5 (0.150 g, 0.382 mmol) and 6 (0.412 g,
1.145 mmol) were dissolved in dry DMF (2–3 ml) in
a tube. CoCl2 ꢁ 6H2O (90.44 mg, 0.382 mmol) was added
to this solution. The mixture was heated and stirred at
160–170 ꢃC for 24 h under nitrogen atmosphere to give
an unsymmetrical substituted Pc (Scheme 1). After
being cooled, the reaction mixture was poured into

5434
D. Kulac¸ et al. / Polyhedron 26 (2007) 5432–5440
O N
OH
OH
O N
CN
CN
+
K CO
(2)
(1)
DMSO
CN
O
O
CN
O N
O N
OH
+
O
CN
CN
CN
CN
(4)
(3)
K CO
1-bromooctane
CH CN
S
S
DMF
CoCl . H O
O
N
N
N
N
O N
O
O
2 6
2
S
S
N
Co
N
O N
O
N
N
CN
NC
SR
SR
(6)
CN
NC
(5)
S
S
R=C6H13
NO
CH
(7)
CH
O
O
O
N
N
N
N
O N
O
N
M
N
N
O
O
NO
N
O
O
H C
H C
NO
(8)
M= Zn
M= Co
(9)
(10)
M=Lu(OAc)
Scheme 1. Summary of the synthesis of compounds 3–10.
50 ml of ethanol and the dark green precipitate that
formed was separated by centrifugation. The crude Pc
mixture was washed with cold acetic acid, water, etha-
nol and methanol, and then dried in a vacuum. The
purification of that aimed Pc 7 was carried out on a
silica gel column with a CHCl3:hexane system, chang-
ing from 10/1 to 10/2 (v/v). Compound 7 is soluble
in chloroform, dichloromethane, ethyl acetate, hexane,
DMF, THF and DMSO. Yield of 7: 0.12 g (20.50%).
M.p.: >300 ꢃC. IR (cmax/cmꢀ1 KBr disc): 3050 (Ar–
H), 1411–1595 (–C@C–), 1222–1274 (Ar–O–C),
1377 and 1517 (–NO2), 2860–2929 (–CH2–, –CH3),
1072–1124 (C–S). UV–Vis kmax (CHCl3) (loge/
2.1.4. 2,10,16,24-Tetrakis-[4-nitro-2-(octyloxy)phenoxy]-
phthalocyaninatozinc(II) (8)
A mixture of compound 5 (0.168 g, 0.427 mmol), anhy-
drous zinc acetate (0.094 g, 0.427 mmol) and DMF (3–
4 ml) was heated and stirred at 180 ꢃC for 6 h under nitro-
gen atmosphere. After cooling to room temperature, meth-
anol (5 ml) was added in order to precipitate the product.
The blue product was filtered off and then washed several
times, first with methanol, then with acetonitrile and ace-
tone. The crude product was isolated by silica gel column
chromatography with chloroform as the eluent. This prod-
uct is soluble in CHCl3, DMSO, DMF and THF. Yield:
0.020 g (11.50%). M.p.: >300 ꢃC. IR (cmax/cmꢀ1 KBr disc):
3040 (Ar–H), 1514–1650 (–C@C–), 1222–1282 (Ar–O–C),
1340 and 1558 (–NO2), 2854–2921 (–CH2–, –CH3). UV–
Vis kmax (CHCl3) (loge/dmꢀ3 molꢀ1 cmꢀ1): 679 (4.16),
dmꢀ3 molꢀ1 cmꢀ1):
697(5.4739),
629(5.0012),
424
(4.7700), 327(5.4681). MS(MALDI-TOF): m/z 1533 Da
mass (M+H+) and (Mꢀ32)+.

D. Kulac¸ et al. / Polyhedron 26 (2007) 5432–5440
5435
611 (3.47), 342 (3.98). 1H NMR (dH ppm, 400 MHz,
CDCl3): 8.10 (dd, J = 2.73, Ar–H), 7.98 (d, J = 2.73, Ar–
H), 7.72 (d, J = 8.19, Ar–H), 7.60 (dd, J = 3.12, Ar–H),
7.12 (d, J = 2, Ar–H), 6.98 (d, J = 8.97, Ar–H), 4.12 (t,
J = 5.86, –OCH2), 3.95 (t, J = 6.44, –CH3), 1.25 (m,
(–CH2)6). MS (MALDI-TOF): m/z 1638.0019 (M+H+).
electrolyte at a concentration of 0.10 mol dmꢀ3. High pur-
ity N2 was used for deoxygenating the solution for at least
20 min prior to each run and to maintain a nitrogen blan-
ket during the measurements. For CPC studies, a Pt gauze
working electrode (10.5 cm2 surface area), a Pt wire coun-
ter electrode separated by a glass bridge, and an SCE as a
reference electrode were used.
2.1.5. 2,10,16,24-Tetrakis-[4-nitro-2-(octyloxy)phenoxy]-
phthalocyaninatocobalt(II) (9)
2.3. Electrical measurements
A mixture of compound 5 (0.150 g, 0.382 mmol),
90.440 mg (0.3816 mmol) CoCl2 and absolute ethylene gly-
col (4–5 ml) was heated and stirred at 160 ꢃC for 22 h under
nitrogen atmosphere. After cooling to room temperature,
the reaction mixture was treated with ethanol to precipitate
the dark-blue product, which was then filtered. This prod-
uct is soluble in CHCl3 and THF, and partially in CH2Cl2
and DMF (Scheme 1). Yield 19.5 mg (12.53%). M.p.:
>300 ꢃC. IR (cmax/cmꢀ1 KBr disc): 3082 (Ar–H), 1467–
1600 (–C@C–), 1222–1282 (Ar–O–C), 1340–1508 (–NO2),
2854–2921 (–CH2–, –CH3). UV–Vis kmax (CHCl3) (loge/
dmꢀ3 molꢀ1 cmꢀ1): 671 (4.24), 605 (3.63), 327 (4.10); MS
(MALDI-TOF): m/z 1633.0136 (M+H+).
For the electrical and impedance measurements, an
interdigital comb structure with a 100 lm gap on glass sub-
strate was used. Thin films of compounds were obtained by
the spin-coating method. The substrate temperature was
kept constant at 290 K during deposition of the materials
over the electrodes. Dc conductivity and impedance spec-
tral measurements were performed between 295 and
433 K using a Keithley 617 electrometer. Ac conductivity
and impedance measurements were carried out with a
Keithley 3330 LCZ meter in the frequency range 40–105
Hz, in the temperature range 295–433 K.
3. Results and discussion
2.1.6. 2,10,16,24-Tetrakis-[4-nitro-2-(octyloxy)phenoxy]-
phthalocyaninato lutetium(III) acetate (10)
3.1. Synthesis and characterization
A mixture of LuðOAcÞ3 ꢁ nH2O (0.023 g, 0.065 mmol), 5
(0.400 g,
1.018 mmol)
and
DBU
(1.130 mg,
Starting from 1 and 2, a general synthetic route for the
synthesis of new symmetrical and unsymmetrical Pcs is
given in Scheme 1. Compounds 3 and 4 were obtained by
base-catalyzed nucleophilic aromatic nitro displacement,
in 10% and 88% yield, respectively. The reaction was car-
ried out in a single step synthesis by using K2CO3 as the
nitro-displacing base at 78–80 ꢃC in dry DMSO under an
argon atmosphere. Starting from 4 and 1-bromooctane,
the general alkylation reaction gave 5 in the presence of
K2CO3 at 80–85 ꢃC for 48 h under an argon atmosphere
in 75% yield. The symmetrical MPcs 8, 9 and 10 were
obtained from the dicyano derivative 5 and the correspond-
ing metal salts (Zn(OAc)2, CoCl2, LuðOAcÞ3 ꢁ nH2OÞ in
suitable anhydrous solvents under reflux in a sealed tube,
in 12%, 13% and 36.7% yields, respectively. The high boil-
ing solvents of choice for these reactions were DMF for
Zn(II)Pc 8, ethylene glycol for Co(II)Pc 9 and pentanol
for Lu(III)(OAc)Pc 10. These symmetrical MPcs were iso-
lated by column chromatography on silica gel using CHCl3
as the eluent. The unsymmetrical Co(II)Pc 7 was synthe-
sized by CoCl2-mediated statistical condensation of a 3:1
molar ratio of 5 and 6 in anhydrous DMF under reflux
for 24 h. Product 7 was separated by column chromatogra-
phy on silica gel using different CHCl3:hexane solvent sys-
tems, changing from 10/1 to 10/2 (v/v), as the eluent. All
the Pcs 7, 8, 9 and 10 show good solubility in common
organic solvents such as chloroform, dichloromethane
and tetrahydrofuran. The spectroscopic characterization
0.009128 mmol) in pentanol (2.5 ml) was refluxed under
nitrogen atmosphere at 175–180 ꢃC for 20 h. The dark
green mixture was cooled to room temperature and then
was washed with water, acetonitrile, ethanol, methanol
and acetone, and then dried in vacuum. Compound 10 is
soluble in acetic acid and THF, and partially in DMF
and DMSO. Yield 0.155 g (36.70%). M.p.: >300 ꢃC
(Scheme 1). IR(cmax/cmꢀ1 KBr disc); 3066 (Ar–H), 1469–
1666 (–C@C–), 1213–1276 (Ar–O–C), 1334 and 1506
(–NO2), 2858–2925 (–CH2–, –CH3). UV–Vis kmax (DMF)
(loge/dmꢀ3 molꢀ1 cmꢀ1): 685 (4.8140), 618 (4.3802), 334
(5.0307). MS (MALDI-TOF): m/z 1808 (M+H+).
2.2. Electrochemistry
The cyclic voltammetry, differential pulse voltammetry
and controlled potential chronocoulometry (CPC) mea-
surements were carried out with a Princeton Applied
Research Model Versostat II potentiostat/galvanostat con-
trolled by an external PC and utilizing a three-electrode
configuration at 25 ꢃC. The working electrode was a Pt
plate with a surface area of 0.10 cm2. The surface of the
working electrode was polished with a H2O suspension of
Al2O3 before each run. The last polishing was done with
a particle size of 50 nm. A Pt wire served as the counter
electrode. A saturated calomel electrode (SCE) was
employed as the reference electrode and was separated
from the bulk of the solution by a double bridge. Electro-
chemical grade tetrabutylammonium perchlorate (TBAP)
in extra pure DMSO was employed as the supporting
1
of the newly synthesized compounds included H NMR,
IR, UV/Vis and mass spectral investigations, and the
results are in accordance with the proposed structures.

5436
D. Kulac¸ et al. / Polyhedron 26 (2007) 5432–5440
The IR spectra of 3, 4 and 5 indicate the presence of
In the 1H NMR spectra of 3, 4 and 5, the aromatic pro-
tons of the compounds appear in the low field region
around 8.32–7.12 ppm. The octyl protons of 5 are observed
between 0.86 and 4.07 ppm. The hydroxy proton of 4
appears at a lower field around 11.6 ppm. In the D2O
exchanged NMR spectrum of 4 this assignment was con-
firmed by the disappearance of the sharp hydroxy proton
peak at 11.6 ppm. The 1H NMR spectra of Zn(II)Pc 8
are almost identical. The aromatic protons of 8 appear in
the low field region around 7.00–8.12 ppm. The octyl pro-
tons are observed in the range 0.70–4.14 ppm. The 1H
NMR spectra of the unsymmetrical Co(II)Pc, symmetrical
Co(II)Pc and Lu(III)(OAc)Pc could not be determined
because of the presence of paramagnetic cobalt and lute-
tium atoms.
Pcs 7, 8, 9 and 10 show typical electronic spectra with
two strong absorption regions, one of them in the UV
region at about 300–400 nm (B band) arising from the dee-
per p-levels ! LUMO transition and the other in the visi-
ble part of the spectrum around 600–700 nm (Q band)
attributed to the p ! p* transition from the highest occu-
pied molecular orbital (HOMO) to the lowest unoccupied
molecular orbital (LUMO) of the Pc2ꢀring. Spectra of
the symmetrical Zn(II) and Co(II) phthalocyanines 8 and
9 in chloroform are very similar, with intense Q bands at
679 and 671 nm due to a single p ! p* transition with
shoulders at 611 and 605 nm and B bands at 342 and
327 nm, respectively. The splitting of the Q band of both
compounds shows aggregation. The spectrum of 7 in chlo-
roform shows a characteristic Q band absorption around
697 nm (with a shoulder at 629 nm) and B band absorp-
tions around 424 and 327 nm. The spectrum of 10 in
DMF indicates a Q band absorption around 685 nm and
a B band absorption around 334 nm (Fig. 1). In the spectra
of both compounds, besides the splitting of the Q band, a
very strong of soret band indicates strong aggregation of
both compounds [15].
–C„N groups by the intense stretching bands at 2235,
2223 and 2234 cmꢀ1, respectively. The IR spectra of 3, 4
and 5 exhibit characteristic frequencies at 3037–3083 (Ar–
H), 1485–1598 (–C@C–), 1136–1292 (Ar–O–C), 1332 and
1569 (–NO2) cmꢀ1. The IR spectra of 3, 4 and 5 are very
similar, except those of 4 (Ar–OH) with vibrations at
3276 cmꢀ1 and of 5 (–CH2–, –CH3) with vibrations at
2847–2932 cmꢀ1. Cyclotetramerization of dinitriles 5 to
Pcs 7, 8, 9 and 10 was confirmed by the disappearance of
the sharp –C„N vibration at 2234 cmꢀ1. The IR spectra
of the symmetrical Pcs 8, 9 and 10 and the unsymmetrical
Pc 7 are very similar, except for the C–S vibrations at 1072–
1124 cmꢀ1. The IR spectra of 8, 9 and 10 exhibit character-
istic frequencies at 3230–3066 (Ar–H), 1467–1650 (–C@C–),
1213–1282 (Ar–O–C), 1334–1558 (–NO2) and 2854–2925
(–CH2–, –CH3) cmꢀ1
.
Positive ion MALDI-MS spectra of 7, 8, 9 and 10 are
given in Figs. 2–5, respectively. Many different MALDI
matrices were tried to find an intense molecular ion peak
Fig. 1. UV–Vis spectra of 7, 8, 9 and 10 (–-– 7, . . . 8, — 9, --- 10) (7, 8, 9
in CHCl3, 10 in DMF).
V
o
a
e
S
p
c
#
1
B
P
=
1
5
0
.
1
7
3
7
]
1
5
0
.
1
6
7
100
1
5
0
1
.
8
0
0
1
100
90
80
70
60
50
40
30
20
10
100
90
80
70
60
50
40
30
90
80
70
60
V
y
g
r
S
e
c
#
1
B
[
P
=
1
5
0
7
1
,
.
1
7
2
]
50
20
10
40
1450
1470
1490
1510
1530
1550
30
20
10
Mass (m/z)
1400
1520
1640
1760
1880
2000
600
980
1360
1740
2120
2500
Mass (m/z)
Mass (m/z)
Fig. 2. MALDI-MS spectrum of the unsymmetrical Co(II)Pc 7 (left: linear mode; right: reflectron mode).

D. Kulac¸ et al. / Polyhedron 26 (2007) 5432–5440
5437
MALDI-MS spectrum for this complex was accumulated
using 10 laser shots so as not to give high fragmentation.
In this case, however, the resolution was observed at very
low values of about 2500. When the number of laser shots
was chosen to be between 1 and 5, more intense spectra
could be obtained but the resolution was really diminished
this time. Because of all these reasons, the resolution and
the intensity of the protonated molecular ion peak were
optimized accumulating an average of 10 laser shots for
this complex. On the protonated molecular ion peak, there
is an isotopic distribution resulting from 13C and the iso-
topes of cobalt. In the positive ion MALDI-MS spectrum
of 7, beside the protonated molecular ion peak, two peaks
were observed, one at high and the other at low intensity.
The intense peak is because of the fragmentation of the
complex. At the end of this fragmentation, the leaving
group was observed as O2, having 32 Da mass. The O2
leaving group results from NO2 functional groups. The sec-
ond fragment peak is due to side chain elimination
(C8H17O leaving). This pointed out that the complex was
not more stable under the MALDI matrix conditions than
under the laser energy, but the positive ion MALDI-MS
spectra could be carried out by MALDI-MS.
a-Cyano-4-hydroxycinnamic acid MALDI matrix
yielded the best MALDI-MS spectra for 8 and 9. The peak
group representing the protonated molecular ion of 8 was
observed, starting with 1637 Da mass and finishing with
1644 Da, following each other by 1 Da mass differences.
This type of mass distribution resulted from the isotopic
mass distribution of carbon (mainly 13C) and the isotopes
of zinc and cobalt in the metal complexes. The experimen-
tally obtained isotopic mass distribution of 9 overlapped
with the theoretical isotopic mass distribution calculated
using isotopes of carbon and cobalt. In the MALDI-MS
spectrum of 8, besides the protonated molecular ion peak,
two peaks were observed with very low intensities. These
peaks are due to side chain elimination (mainly C8H17O)
and also the other whole side chain elimination. This
pointed out that the complex was very stable under the
MALDI matrix conditions and also under the laser energy.
The peak group representing the protonated molecular ion
of 9 was observed starting with 1631 Da mass and finishing
with 1636 Da, following each other by 1 Da mass differ-
ences. In the MALDI-MS spectrum of 9, besides the pro-
tonated molecular ion peak, no fragment ion was
observed. This suggests that no leaving group was available
for this complex and the complex is very stable under the
MALDI matrix conditions and also under the laser energy.
The positive ion and linear mode spectra of 10 could be
obtained only in dithranol matrix compared to the other
novel MALDI matrices. The protonated molecular ion
peak of the complex was observed at 1808 Da. Beside the
protonated molecular ion peak, only one another peak
was observed, representing the AcO (acetate) and
C14H20NO4 groups leaving from the protonated ion peak.
Limited fragmentations showed that this complex has high
stability under the laser firing and MALDI-MS conditions.
V
o
a
e
S
p
e
c
1
B
=
1
6
9
1
,
6
2
7
8
]
100
90
80
70
60
50
40
30
20
100
90
80
70
60
50
40
30
20
1625
1631
1637
1643
1649
1655
Mass (m/z)
800
1140
1480
1820
2160
2500
Mass (m/z)
Fig. 3. MALDI-MS spectrum of the symmetrical Zn(II)Pc 8.
100
V
o
y
a
g
e
S
p
c
#
1
B
P
=
1
6
9
1
.
,
6
5
2
8
0
]
100
90
80
70
60
50
40
30
20
10
90
80
70
60
50
40
30
20
10
1625
1629
1633
1637
1641
1645
Mass (m/z)
600
980
1360
1740
2120
2500
Mass (m/z)
Fig. 4. MALDI-MS spectrum of the symmetrical Co(II)Pc 9.
1974.73
100
1974.40
90
1575.94
80
70
60
1579.27
50
2199.93
40
2337.8
2462.26
3577.10
30
1000
1600
2200
2800
3400
4000
Mass (m/z)
Fig. 5. MALDI-MS spectrum of the symmetrical Lu(III)(AcO)Pc 10.
and low fragmentation under the MALDI-MS conditions
for the complexes.
For complex 7, 3-indole acrylic acid MALDI matrix
yielded the best MALDI-MS spectrum. The peak group
representing the protonated molecular ion of the complex
was observed, starting with 1533 Da mass and finishing
with 1537 Da, following each other by 1 Da mass differ-
ences. The intensity of the protonated molecular ion peak
was really low when the MALDI-MS spectrum was moni-
tored by the laser shots higher than 20. Therefore, the

5438
D. Kulac¸ et al. / Polyhedron 26 (2007) 5432–5440
The protonated molecular ion peak mass showed that a
lutetium complex containing a single ligand and acetate
ion was synthesized instead of the sandwich type lutetium
complex. From the clean spectrum, it could be noticed that
the purity of the synthesized lutetium complex was very
high.
20
10
a
R2
R1
O1
0
25 mVs-1
50 mVs-1
100 mVs-1
250 mVs-1
500 mVs-1
-10
-20
3.2. Electrochemistry
The solution redox properties of the Pc complexes (7–
10) were studied using cyclic voltammetry, differential pulse
voltammetry and controlled potential chronocoulometry in
DMSO with a platinum electrode. Complete electrolysis of
each Pc solution at the working electrode at a suitable con-
stant potential for each redox process was achieved, and
the time integration of the electrolysis current was recorded
with the controlled potential coulometry studies. The
charge, Q, at the end of the electrolysis was calculated
using the current–time response of the solution and Fara-
day’s law was used to estimate the number of electrons
transferred. The number of electrons was found to be one
for all the redox processes observed in this study. Voltam-
metric data and the assignment of the redox couples
recorded for the complexes are listed in Table 1. Fig. 6
shows typical cyclic and differential pulse voltammograms
of 9 in DMSO containing TBAP.
1.0
0.5
0.0
-0.5 -1.0 -1.5 -2.0
E / V versus SCE
1.0
0.5
b
R1
O1
R2
-0.5
-1.0
1.0
0.5
0.0
-0.5
-1.0
-1.5
-2.0
E / V versus SCE
Fig. 6. Cyclic (a) and differential pulse (b) voltammograms of 9 in TBAP/
DMSO.
Complex 8 gives three one-electron reduction processes
labelled as R1 at ꢀ0.67 V, R2 at ꢀ0.98 V and R3 at
ꢀ1.76 V, and a one-electron oxidation process labelled as
O1 at 0.85 V vs. SCE at 0.100 V sꢀ1 scan rate (Table 1).
Voltammetric studies revealed that the redox behaviours
of 8 and 10 are very similar to each other and to the
metal-free Pcs [16] (Table 1). This similarity suggests that
all the one-electron redox processes of these complexes
are Pc ring based. However, the redox potentials of 10
occur at potentials slightly more negative as compared to
8. The shift in the potentials can be attributed to the differ-
ence in the polarizing effect of the metal ions. Reduction of
the Pc ligand is associated with the position of the LUMO,
whereas oxidation of the ligand is associated with the posi-
tion of the HOMO. Thus the difference between the poten-
tials of the first oxidation and the first reduction processes
(DE1/2) reflects the HOMO–LUMO gap for metal free Pcs
and it is closely related to the HOMO–LUMO gap in MPc
species involving a redox inactive metal center. The DE1/2
values recorded for 8 and 10 in this study are in agreement
with the values reported previously for the relevant Pcs
involving a redox-inactive metal center [16]. The ratio of
the anodic to the cathodic peak currents for the couples
of 8 and 10 is close to unity, suggesting reversible redox
processes. The anodic to cathodic peak separations (DEp)
changed from 0.070 to 0.140 V within the scan rates from
0.010 to 0.500 V sꢀ1(DEp changed from 0.060 to 0.140 V
for ferrocene), providing additional support for the revers-
ible electron transfer. The peak currents increased linearly
with the square root of the scan rates for scan rates ranging
from 0.010 to 0.500 V sꢀ1, indicating purely diffusion-con-
trolled behavior [17].
Table 1
The electrochemical data of the Pc complexes
Complex
Redox
processes
Ea1/2
DEbp
(V)
Ipa/
Icpc
DEd1/2
(V)
(V vs. SCE)
8
R1
R2
R3
O1
ꢀ0.67
ꢀ0.98
ꢀ1.76
0.85
0.070
0.080
0.160
0.060
0.96
0.98
e
1.52
e
9
R1
R2
O1
ꢀ0.37
ꢀ1.28
0.45
0.100
0.080
0.100
1.00
0.96
0.95
0.82
0.88
1.48
7
R1
R2
O1
ꢀ0.40
ꢀ1.32
0.48
0.080
0.090
0.090
0.97
0.96
0.98
10
R1
R2
R3
O1
ꢀ0.73
ꢀ1.03
ꢀ1.82
0.75
0.080
0.090
0.120
0.140
0.94
1.00
e
0.98
a
E1/2 = (Epa + Epc)/2 at 0.100 V sꢀ1
.
b
c
DEp = Epa ꢀ Epc at 0.100 V sꢀ1
.
Ipa/Ipc for reduction, Ipc/Ipa for oxidation processes at 0.100 V sꢀ1
.
The redox potentials of 7 and 9 are considerably similar
to each other, but highly different as compared to those of
8 and 10 (Table 1). Within the electrochemical window of
TBAP/DMSO, compounds 7 and 9 undergo a reversible
d
DE1/2 = E1/2(first oxidation) ꢀ E1/2(first reduction). This value reflects
the HOMO–LUMO gap for 8 and 10, but not 7 and 9.
e
DEp could not be determined due to an ill-defined redox wave.

D. Kulac¸ et al. / Polyhedron 26 (2007) 5432–5440
5439
one-electron oxidation and two reversible one-electron
1.0E-05
1.0E-06
1.0E-07
1.0E-08
1.0E-09
7
9
8
10
reductions with anodic to cathodic peak separations
(DEp) changing from 0.080 to 0.100 V within scan rates
from 0.010 to 0.500 V sꢀ1. The peak currents increased lin-
early with the square root of the scan rates for scan rates
ranging from 0.010 to 0.500 V sꢀ1, indicating purely diffu-
sion-controlled behavior [17]. The difference in the voltam-
metric behaviour of these complexes as compared to those
of 8 and 10 is due to the fact that metallo phthalocyanines,
such as MnPc, CoPc and FePc, having a metal that pos-
sesses energy levels lying between the HOMO and the
LUMO of the Pc ligand, in general exhibit redox processes
centered on the metal [16,18–21]. Moreover, the electro-
chemistry of CoPc is dependent on the coordinating nature
of the solvents. For CoPc complexes, the first oxidation
and the first reduction processes occur on the metal center
in polar coordinating solvents such as DMF and DMSO,
whilst the first oxidation process occurs on the Pc ring in
non-polar solvents such as DCM and THF. Therefore,
the first reduction and the first oxidation processes of 7
and 9 could be assigned easily to the [Co(II)Pc(ꢀ2)]/
[Co(I)Pc(ꢀ2)]ꢀ and [Co(II)Pc(ꢀ2)]/[Co(III)Pc(ꢀ2)]+ redox
couples and the second reduction process to the Pc ring as
[Co(I)Pc(ꢀ2)]ꢀ/[Co(I)Pc(ꢀ3)]2ꢀ. The separation between
the first oxidation and the first reduction potentials of the
metal center for these Co(II) complexes (0.88 for 7 and
0.82 V for 9) is comparable with the relevant values in
the literature [15,17–20], and does not reflect the
HOMO–LUMO gap. The small differences between the
redox potentials of 7 and 9 can be attributed to the differ-
ence in peripheral substituents attached to the Pc core.
10
100
1000
Frequency / Hz.
10000
100000 1000000
Fig. 7. The variation of the ac conductivity with frequency at 373 K.
form rac(x) = A(T)xs, where A(T) and s are temperature
dependent parameters. To explain this type of frequency
dependence of the ac conduction, two models have been
used. According to the first model, which is known as the
quantum mechanical tunnelling model (QMT), the conduc-
tion occurs by means of thermally assisted Quantum
Mechanical Tunnelling. The other model, which is known
as the Correlated Barrier Hopping (CBH) model, is based
on the concept of charged defects and in this bipolarons
hop between two charged defect states D+ and Dꢀ over
the barrier separating them. In these two models, the fre-
quency exponent s is found to have two different trends
with temperature and frequency [22]. The values of the fre-
quency exponent s were calculated from the slope of the
measured lnrac versus lnx graphs. Our results showed that
s is definitely a function of temperature for all the com-
pounds and shows a general tendency to decrease with
increasing temperature. This is in agreement with the pre-
diction of the CBH model.
3.3. Electrical measurements
Arrhenius-type behavior is clearly observed from the
temperature dependent conductivity measurements for all
the compounds. A linear fit to rdc = r0 exp(ꢀEA/kT) is
shown with different correlation coefficients. The electrical
parameters corresponding to the studied compounds are
shown in Table 2.
The frequency dependence of the ac conductivity,
rac(x), for different values of temperatures between 295
and 433 K was investigated for all samples. The frequency
dependence of the ac conductivity is shown in Fig. 7 for all
compounds as a plot of lnrac versus lnx at 373 K. The
general observed frequency dependence of the ac conduc-
tivity in disordered systems, such as phthalocyanine, is that
the ac conductivity obeys an empirical power law of the
To get more detailed information about the electrical
properties of the compounds, impedance spectral measure-
ments in the frequency range 40–105 Hz were also carried
out on a spin coated film of the compounds. The measured
impedance spectra, when plotted in a complex plane plot,
8.0E+06
8
7.0E+06
10
7
9
6.0E+06
5.0E+06
4.0E+06
3.0E+06
2.0E+06
1.0E+06
0.0E+00
Table 2
The electrical parameters of the Pc complexes
Samples
r290 K (Xꢀ1 cmꢀ1
)
EA (eV)
r433 K (Xꢀ1 cmꢀ1
)
7
8.76 · 10ꢀ9
1.82 · 10ꢀ9
2.959 · 10ꢀ8
3.16 · 10ꢀ7
0.81
0.79
0.70
0.72
1.41 · 10ꢀ4
1.07 · 10ꢀ4
1.84 · 10ꢀ4
2.1 · 10ꢀ4
0.0E+00
5.0E+06
1.0E+07
R / Ohm
1.5E+07
2.0E+07
8
9
10
Fig. 8. Impedance spectra of the Pc films at 400 K.

5440
D. Kulac¸ et al. / Polyhedron 26 (2007) 5432–5440
[3] N.B. McKeown, Phthalocyanine Materials, Cambridge University
Press, Cambridge, 1998.
[4] M.J. Cook, M.F. Daniel, K.J. Harrison, N.B. McKeown, A.J.
Thomson, J. Chem. Soc., Chem. Commun. (1987) 1148.
appear in the form of a succession of semi-circles represent-
ing the contributions to the electrical properties due to bulk
material, grain boundary effect and interfacial polarization
phenomena. So, the impedance spectra technique enables
us to separate the effects due to each component. At low
temperatures, the impedance spectra consist of a quasi-ver-
tical line. The existence of semicircular shaped curves in the
Nyquist plot means that the impedance becomes capacitive
even at relatively high frequencies. The effect of tempera-
ture on the impedance spectra of the films becomes clearly
visible with a rise in the temperature. On the complex plane
plot at high temperatures, only depressed semicircles with
different radii were observed at higher temperatures, indi-
cating deviation from the Debye dispersion relation
(Fig. 8). In the case of a depressed semi-circle in the imped-
ance spectra, the relaxation time is considered as a distribu-
tion of values, rather than a single relaxation time.
´
´
[5] M.A. Diaz-Garcia, J.M. Cabrera, F. Agullo-Lopez, Appl. Phys. Lett.
3 (1996) 69.
[6] H. Schultz, H. Lehmann, M. Rein, M. Hanack, Struct. Bond. 74
(1991) 41.
[7] I. Rosenthal, Photochem. Photobiol. 53 (1991) 859.
¨
¨
[8] R. Zhou, F. Josse, W. Go¨pel, Z.Z. Ozturk, O. Bekaroglu, Appl.
Organomet. Chem. 10 (1996).
[9] M.J. Cook, J. Mater. Chem. 6 (1996) 677.
[10] J.C. Swarts, E.H.G. Langner, N. Kroeide-Hove, M.J. Cook, J. Mater.
Chem. 11 (2001) 434.
¨
[11] S. Abdurrahmanoglu, A. Altindal, A.R. Ozkaya, M. Bulut, O.
Bekaroglu, Chem. Commun. (2004) 2096.
¨
[12] T. Ceyhan, A. Altindal, A.R. Ozkaya, M.K. Erbil, B. Salih, O.
Bekaroglu, Chem. Commun. (2006) 320.
[13] J.G. Young, W.J. Onyebuagu, Org. Chem. 55 (1990) 2155.
¨
[14] A.G. Gurek, O. Bekarog˘lu, J. Chem. Soc., Dalton Trans. (1994)
¨
1419.
[15] N. Kobayashi, Y. Niskiyama, T. Ohya, M. Sato, J. Chem. Soc.,
Chem. Commun. (1987) 390.
Acknowledgements
[16] A.B.P. Lever, E.R. Milaeva, G. Speier, in: C.C. Leznoff, A.B.P. Lever
(Eds.), Phthalocyanines: Properties and Applications, vol. 3, VCH
Publishers, New York, 1993, pp. 1–63.
This work was supported in part by The Turkish Acad-
_
¨
emy of Sciences (TUBA), TUBITAK (Project No.
106T326), The Research Fund of Marmara University
(SCIENCE-YLS-290506-0124) and The State Planning
Organization (DPT-2003K120810).
[17] A.J. Bard, L.R. Faulkner, Electrochemical Methods: Fundamentals
and Applications, 2nd ed., Wiley, New York, 2001.
¨
¨
¨
[18] M. Ozer, A. Altindal, A.R. Ozkaya, M. Bulut, O. Bekaroglu,
Polyhedron 25 (2006) 3593.
¨
¨
[19] A.R. Ozkaya, E. Hamuryudan, Z.A. Bayır, O. Bekaroglu, J. Porphyr.
Phthalocya. 4 (2000) 689.
References
¨
¨
[20] M. Kandaz, A.R. Ozkaya, O. Bekarog˘lu, Monatsh. Chem. 132 (2001)
1013.
[1] C.C. Leznoff, A.B.P. Lever (Eds.), Phthalocyanines, Properties and
Applications, vols. 1–4, VCH, New York, 1989, 1992, 1993, 1996.
[2] G. De la Torre, P. Vazquez, F. Agullo-Lopez, T. Torres, J. Mater.
Chem. 8 (1998) 1671.
[21] A. Koca, H.A. Dinc¸er, H. C¸ erlek, A. Gul, M.B. Koc¸ak, Electrochim.
¨
Acta 52 (2006) 1199.
[22] S.R. Elliot, Adv. Phys. 36 (1987) 135.