Synthesis, characterization and electrical properties of peripherally tetra-aldazine substituted novel metal free phthalocyanine and its zinc(II) and nickel(II) complexes

Article abstract of DOI:10.1016/j.saa.2012.12.058

The novel phthalonitrile containing azine segment and its corresponding tetra aldazine substituted metal free- and metallo-phthalocyanines (Zn(II) and Ni(II)) were synthesized and characterized by IR, ¹H NMR, Mass, UV-Vis spectroscopy and elemental analysis and addition to these techniques for substituted phthalonitrile ¹³C NMR have been used. In addition, dc and ac electrical properties of the films of these novel phthalocyanines were investigated as a function of temperature (295-523 K) and frequency (40-10 ⁵ Hz). Activation energy values of the films of the phthalocyanines were calculated from straight portions of the Arrhenius plot (ln σ_dc-1/T curves) as 0.70 eV, 0.93 eV and 0.91 eV for the films of metal free, nickel- and zinc-phthalocyanines, respectively. From impedance spectroscopy measurements, it is observed that bulk resistance decreases with increasing temperature indicating semiconductor property.

Full text of DOI:10.1016/j.saa.2012.12.058

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 105 (2013) 550–556
Contents lists available at SciVerse ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Synthesis, characterization and electrical properties of peripherally
tetra-aldazine substituted novel metal free phthalocyanine and its zinc(II)
and nickel(II) complexes
b
a
a
Rıza Bayrak a, , Fatih Dumludag˘ , Hakkı Türker Akçay , Ismail Deg˘irmenciog˘lu
⇑
_
a Department of Chemistry, Faculty of Sciences, Karadeniz Technical University, 61080 Trabzon, Turkey
Department of Physics, Faculty of Arts and Science, Marmara University, 34722 Istanbul, Turkey
b
_
g r a p h i c a l a b s t r a c t
h i g h l i g h t s
2.E-11
1.E-11
0.E+00
-1.E-11
-2.E-11
3.E-07
2.E-07
1.E-07
0.E+00
-1.E-07
-2.E-07
-3.E-07
"
The preparation of the aldazine
substituted phthalonitrile 3.
Synthesis and characterization of
metal free 4 and
metallophthalocyanines 5, 6.
Dc and ac conductivity studies of the
novel phthalocyanines 4–6.
1.E-04
1.E-05
1.E-06
1.E-07
1.E-08
1.E-09
"
10
1000
100000
Frequency (Hz)
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
Voltage (V)
"
3.0E+06
2.5E+07
2.0E+07
1.5E+07
1.0E+07
5.0E+06
0.0E+00
458
478
498
523
K
K
K
K
2.5E+06
2.0E+06
1.5E+06
1.0E+06
5.0E+05
0.0E+00
295
348
363
378
398
418
438
K
K
K
K
K
K
K
10
100
1000
Frequency (Hz)
10000
100000
0.0E+00 5.0E+06 1.0E+07 1.5E+07 2.0E+07 2.5E+07
Z' (Ohm)
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 5 October 2012
Received in revised form 18 December 2012
Accepted 21 December 2012
Available online 2 January 2013
The novel phthalonitrile containing azine segment and its corresponding tetra aldazine substituted metal
free- and metallo-phthalocyanines (Zn(II) and Ni(II)) were synthesized and characterized by IR, 1H NMR,
Mass, UV–Vis spectroscopy and elemental analysis and addition to these techniques for substituted pht-
halonitrile 13C NMR have been used. In addition, dc and ac electrical properties of the films of these novel
phthalocyanines were investigated as a function of temperature (295–523 K) and frequency (40–105 Hz).
Activation energy values of the films of the phthalocyanines were calculated from straight portions of the
Keywords:
Arrhenius plot (lnrdc–1/T curves) as 0.70 eV, 0.93 eV and 0.91 eV for the films of metal free, nickel- and
Phthalocyanine
Electrical characterization
Impedance spectra
Hopping
zinc-phthalocyanines, respectively. From impedance spectroscopy measurements, it is observed that
bulk resistance decreases with increasing temperature indicating semiconductor property.
Ó 2012 Elsevier B.V. All rights reserved.
Semiconductor
Conductivity
Introduction
semiconductors [8], liquid crystals [9], optical storage devices [10],
laser dyes [11], catalyst [12] and photo dynamic therapy (PDT) [13].
Phthalocyanines (Pcs) are one of the most useful heterocyclic
materials. There are still many investigations on their technological
applications in different scientific areas such as chemical sensors
[1–3], electrochromic displaying systems [4], non-linear optics [5],
solar cells [6], photo-voltaic optics, molecular electronics [7],
Phthalocyanines and their metal complex derivatives have
strong delocalized 18 -electronic structure, good thermal stability
p
and interesting visible area optical properties. The central cavity of
Pc can complex with vary about 70 elements. Depending on spec-
ification of element; monomeric, axially ligated or dimeric phthal-
ocyanines can be obtained. While the cations fitting central cavity
of phthalocyanines form monomeric species [14], high valance and
larger cations form dimeric or axially ligated species [15–17].
⇑
Corresponding author. Tel.: +90 506 389 6589; fax: +90 462 325 3196.
E-mail address: bayrakriza@ktu.edu.tr (R. Bayrak).
1386-1425/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2012.12.058

R. Bayrak et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 105 (2013) 550–556
551
Term of azine uses for description of six-membered ring system
such as pyrazines, pyrimidines in heterocyclic chemistry. In acyclic
chemistry, azines are synthesized that one molecule hydrazine hy-
drate reaction with two molecules of carbonyl compounds. Addi-
tionally this compound class is called ‘‘aldazines’’ when aldehyde
was used as carbonyl compound [18,19]. Azines are known biolog-
ical active compounds. Unsymmetrical aldazines have antitumor
[20], antioxidant [21], antibacterial and antifungal activity [22–24].
In our previous work, photochemical and photophysical proper-
ties of new azine-bridged binuclear metallophthalocyanines were
studied [25]. There is not any study on electrical properties of azine
functionalized phthalocyanines in literature. The aim of the pres-
ent work is synthesis of novel metal free-, Zn- and Ni-phthalocya-
nines and investigation the electrical transport properties of thin
films of synthesized compounds to determine some essential
parameters and predict the electronic conduction properties. In or-
der to investigate electrical properties of the films of phthalocya-
nines dc and ac conductivity measurements were performed as a
function of temperature (295–523 K) and frequency (40–105 Hz).
Impedance spectroscopy measurements were also performed in
the same temperature and frequency range.
dc voltages between ꢀ1 V and 1 V with 50 mV steps to the films
of compounds. The data for dc conductivity were acquired using
Keithley model 617 programmable electrometer. Ac conductivity
and impedance spectra (IS) measurements were performed using
Keithley model 3330 LCZ meter in the frequency range of
4 ꢁ 10ꢀ2–100 kHz. All the electrical measurements were
performed in the temperature range of 295–523 K in vacuum
(<10ꢀ3 mbar) in dark. The temperature was measured using Chro-
mel–Alumel thermocouple. Both dc and ac conductivity data were
recorded using an IEEE-488 data acquisition system.
Synthesis
4-(2-{(E)-[(2E)-(phenylmethylidene)hydrazono]methyl}phenoxy)
phthalonitrile (3)
To a solution of 4-nitrophthalonitrile (2) (2 g, 11.55 mmol) in
dry DMF (20 mL) compound (1) (2.59 g, 5.78 mmol) was added
and the temperature was increased up to 55 °C. Finely powdered
dry K2CO3 (1.60 g, 11.60 mmol) was added to the system in eight
equal portions at 15 min intervals with efficient stirring and the
reaction system was stirred at the same temperature for 5 days.
The reaction mixture was poured into ice-water and the precipitate
was filtered and dried in vacuum over P2O5. The raw product puri-
fied by crystallization from acetone/ethanol solvent system. Yield
2.8 g (69%). Anal. calc. for C22H14N4O: C, 75.42; H, 4.03; N, 15.99;
Experimental
All reactions were carried out under dry and oxygen free nitro-
gen atmosphere using Schlenk system. DMF was dried and purified
as described by Perrin and Armarego [26]. 2-{(E)-[(2E)-(phenylme-
thylidene)hydrazono]methyl}phenol (1) [27] and 4-nitrophthalo-
nitrile (2) [28] was prepared according to the literature. 1H
NMR/13C NMR spectra were recorded on a Varian XL-200 NMR
spectrometer in CDCl3, DMSO d6, and chemical shifts were re-
ported (d) relative to MeSi4 as internal standard. IR spectra were
recorded on a Perkin–Elmer Spectrum one FT-IR spectrometer in
ATR technique. The MS–MS spectrum were measured with a Ther-
mo Quantum Access Mass spectrometer with H-ESI probe. Metha-
nol, chloroform and acetonitrile were used as solvents in mass
spectrometer and all mass analysis were conducted in positive
ion mode. Elemental analysis were performed on a Costech ECS
4010 instrument, UV–Vis spectra were recorded by means of a Uni-
cam UV2-100 spectrometer, using 1 cm pathlength curettes at
room temperature. Melting points were measured on an electro-
thermal apparatus and are uncorrected.
Found: C, 75.01; H, 4.31; N, 15.75. IR (KBr tablet)
t
max/cmꢀ1
(alip-CH), 2229 (C„N), 1618–1600 (C@C),
(CH@N), 1275–1247 (CAOAC), 980 d(CH). 1H NMR
:
3047
1555
t(ArACH), 2984 t
t
t
(DMSO-d6), (d: ppm): 8.45 (s, 1H, CH@N), 8.35 (s, 1H, CH@N),
7.92–7.88 (d, 2H, ArH), 7.72–7.57 (m, 4H, ArH), 7.45–7.40 (d, 2H,
ArH), 7.15–7.01 (m, 4H, ArH). 13C NMR (DMSO-d6), (d: ppm):
165.45, 162.13, 160.51, 158.11, 141.12, 138.78, 136.62, 134.15,
133.42, 130.92, 128.18, 124.77, 122.19, 121.54, 120.35, 120.03,
118.85, 116.44, 115.78, 112.44, 108.12. MS (ESI), (m/z): Calculated:
350.12; Found: 351.25 [M+H]+.
Synthesis of phthalocyanines (4–6)
In a glass sealed tube, the mixture of compound 3 (0.20 g,
0.571 mmol), dry N,N-dimethylaminoethanol (DMAE, 3 mL), 1,8-
diazabycyclo[5.4.0] undec-7-ene (DBU, 3 drops) and for metallo-
phthalocyanines (5, 6) stoichiometric amounts of related anhy-
drous metal salts (Zn(CH3COO)2; NiCl2) were heated to 150 °C for
24 h. Then the green products were precipitated by addition of
methanol and filtered.
Preparation of films for electrical measurements
Metal-free phthalocyanine (4). The dark green solid product was
purified by column chromatography with chloroform:methanol
(100:0.5) as eluent. Yield: 46 mg (22%), mp > 300 °C. Anal. calc. for
Interdigital transducer (IDT) was employed as transducer in or-
der to investigate dc and ac electrical properties of the compounds.
Inter digital transducers were fabricated onto glass substrate in our
laboratory. The method for the fabrication of IDTs was described
previously in the literature [29]. The transducer contains 21 of gold
C
88H58N16O4: C, 75.31; H, 4.17; N, 15.97; Found: C, 75.59; H, 4.48;
N, 15.52. IR (KBr tablet) (ArACH),
max/cmꢀ1: 3281 (ANH), 3045
2982 (alip-CH), 1615–1597 (C@C), 1550 (CH@N), 1270–1255
(CAOAC), 973 d(CH). 1H NMR (DMSO-d6), (d: ppm): 8.41 (bs, 8H,
CH@N), 7.82–7.60 (m, 24H, ArH), 7.35–7.28 (m, 12H, ArH), 7.11–
t
t
t
t
electrodes with 100
lm width. Space between the electrodes was
t
also kept at 100 m. In order to obtain thin film of synthesized
l
6.98 (m, 12H, ArH). UV–Vis (CHCl3) kmax/nm: [(10ꢀ5 , dm3 molꢀ1
e -
compounds on IDT, the molecules were dissolved in chloroform
using micro centrifuge tubes. The homogeny solutions were coated
onto IDT using smearing method in air ambient. The substrate tem-
perature was kept constant at 295 K during the deposition of solu-
tion onto IDT.
cmꢀ1)]. 699 (5.07), 660 (5.03), 640 (4.77) 604 (4.59), 338 (5.12).
MS (ESI), (m/z): Calculated: 1402.48, Found: 1403.95 [M+H]+.
Synthesis of zinc (II) phthalocyanine (5). Eluent for column chroma-
tography: chloroform:methanol (100:1). Yield: 80 mg (39.1%),
mp > 300 °C. Anal. calc. for C88H56N16O4Zn: C, 72.05; H, 3.85; N,
Electrical measurements
15.28; Found: C, 72.52; H, 4.11; N, 15.11. IR (KBr tablet) tmax
cmꢀ1: 3057
(ArACH), 2995 (alip-CH), 1620–1602 (C@C), 1561
(CH@N), 1272–1247 (CAOAC), 985 d(CH). 1H NMR (DMSO-d6),
/
To investigate the electrical properties of the compounds, IDTs
(coated with synthesized compounds) were placed into home-
made temperature controlled aluminum chamber. Electrical con-
tacts between electrodes and measurement chamber were done
using silver paste. Dc current values were recorded by applying
t
t
t
t
(d: ppm): 8.55–8.42 (bd, 8H, CH@N), 8.02–7.73 (m, 24H, ArH),
7.42–7.33 (m, 12H, ArH), 7.21–7.08 (m, 12H, ArH). UV–Vis (CHCl3)
kmax/nm: [(10ꢀ5 , dm3 molꢀ1 cmꢀ1)]. 682 (5.25), 620 (4.54), 341
e

552
R. Bayrak et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 105 (2013) 550–556
(5.07). MS (ESI), (m/z): Calculated: 1464.40, Found: 1465.93
ate yield. Spectral data coherent with the proposed structure were
obtained. According to the IR spectral results of the compound (3),
characteristic nitrile stretching vibration was observed at
2229 cmꢀ1. In 1H NMR spectrum of (3), the disappearance of the
OH peak of (1) and presence of additional aromatic protons indi-
cated that nucleophilic aromatic nitro displacement was accom-
plished. In 13C NMR of (3), the new peaks at 116.44 ppm and
115.78 ppm belonging to nitrile carbons indicated that the nuclo-
phylic aromatic substitution has occurred. Mass spectrum of com-
pound (3) indicated that target compound successfully prepared.
Stable molecular ion [M+H]+ peak is seen at 351.25 in mass
spectrum of the compound (3). Also elemental analysis data of com-
pound (3) was satisfactory.
[M+H]+.
Synthesis of nickel (II) phthalocyanine (6). Eluent for column chro-
matography: chloroform:methanol (100:1). Yield: 26 mg (28%),
mp > 300 °C. Anal. calc. for C88H56N16O4Ni: C, 72.38; H, 3.87; N,
15.35; Found: C, 72.25; H, 3.99; N, 15.51. IR (KBr tablet) tmax
cmꢀ1: 3053
(ArACH), 2991 (alip-CH), 1625–1604 (C@C), 1559
(CH@N), 1270–1248 (CAOAC), 981 d(CH). 1H NMR (DMSO-d6),
(d: ppm): 8.35 (bs, 8H, CH@N), 7.92–7.45 (bm, 36H, ArH), 7.25–
/
t
t
t
t
7.12 (m, 12H, ArH). UV–Vis (CHCl3) kmax/nm: [(10ꢀ5 , dm3 molꢀ1
e -
cmꢀ1)]. 673 (5.22), 613 (4.77), 334 (5.14). MS (ESI), (m/z): Calcu-
lated: 1458.40, Found: 1481.95 [M+Na]+.
Although there are a variety of methods in the literature for the
preparation of phthalocyanines [30–33], cyclotetramerization of
substituted phthalonitrile or 1,3-diimino-1H-isoindoles are most
preferred methods for the preparation of phthalocyanine com-
pounds [14,34]. Substituted peripherally or non-peripherally
phthalocyanines are prepared from 4-substitued or 3-substituted
phthalonitriles by means of cyclotetramerization. This reaction re-
Results and discussion
Synthesis and spectroscopic characterization via complementary
techniques
The synthesis route of the novel phthalonitrile (3) and phthalo-
cyanine compounds (4–6) was shown in Fig. 1. Synthesis of pht-
halonitrile derivatives can be performed by nucleophylic aromatic
substitution reaction based on the reaction of 4-nitrophthalonitrile
and a nucleophylic compound in the presence of potassium carbon-
ate. Dipolar aprotic solvents such as DMF, DMSO are used in the
reactions. Synthesis of the initial pthalonitrile derivative (3) was
performed according to literature [25] by the reaction of 4-
nitrophthalonitrile and 2-{(E)-[(2E)-(phenylmethylidene)hydraz-
ono]methyl}phenol in DMF and at 55 °C. Potassium carbonate
was used as basic catalyst at slightly more than the stoichiometric
amount. The compound (3) was recrystallized in acetone/ethanol
solvent system and pale yellow product was obtained with moder-
sults in the formation of four different isomers products (C4h, C2v
Cs and D2h).
,
In the present work, 4-substituted phthalonitrile (3) was used
as initial compound for synthesis of the metal free- and metallo-
phthalocyanines (Zn, Ni) and did not make an effort to separate
the isomeric mixture. Characterization of new phthalocyanines
were performed by IR, 1H NMR, mass spectrometry, UV–Vis spec-
troscopy and elemental analysis. Spectral results of prepared struc-
tures supported the proposed structures. In IR spectra of the
phthalocyanines, absence of the nitrile stretching vibration at
2229 cmꢀ1 indicate that proposed structure of the phthalocyanines
were correct. The most important difference between metal free
Fig. 1. Synthetic route of novel phthalocyanine compounds.

R. Bayrak et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 105 (2013) 550–556
553
and metallo phthalocyanines is the inner core ANH vibration ob-
served at 3281 cmꢀ1 in the IR spectrum of metal free phthalocya-
nine (4). Other spectral results similar to initial phthalonitrile
derivative (3).
In the 1H NMR spectra of the metal free, Zn and Ni Pcs (4–6)
were obtained in DMSO at room temperature. All protons were ob-
served at aromatic region and the spectra were very similar. The
strong aggregation between the metal free phthalocyanine mole-
cules at NMR measurement concentration prevented the observa-
tion of inner core protons in 1H NMR spectrum [35]. In addition,
mass spectral results and elemental analysis data of the com-
pounds (4–6) were good correlation with proposed structure.
UV–Vis absorption spectra
Fig. 3. Absorption spectra of the Zn(II)Pc
1 ꢁ 10ꢀ5 M concentration.
5
and Ni(II)Pc
6
in chloroform at
All phthalocyanine compounds were soluble in organic solvents
such as chloroform, THF, dichloromethane, DMF, DMSO and pyri-
dine. All UV–Vis measurements were made in chloroform and at
1 ꢁ 10ꢀ5 M concentrations. For metal free phthalocyanine (4) the
curves). Dc conductivity of the deposited films on IDT was deter-
mined using Eq. (1) and the slope of the I–V curves.
Q band caused by the transitions from
p
to pꢂ was observed as dou-
blet at 695 and 660 nm, evidence of non-degenerate D2h symmetry
(Fig. 2). Differently from metal free phthalocyanine (4), the Q bands
of the metallo phthalocyanines (5, 6) were observed at 682 and
673 nm respectively (Fig. 3) and observed as singlet due to D4h sym-
metry of the metallophthalocyanines. These shift between the Q-
bands of Zn(II)Pc (5) and Ni(II)Pc (6) is in accordance with previous
literatures [36,37]. The shoulders of the metal free phthalocyanine
(4), Zn(II)Pc (5) and Ni(II)Pc (6) were obseved at 640, 620 and
613 nm, respectively. For Q band regions of phthalocyanines, the
longer wavelength absorptions are due to the monomeric species
and shorter wavelength absorptions (shoulders) are due to the
aggregated species [38]. So, in chloroform at 1 ꢁ 10ꢀ5 M concentra-
tion, monomeric behavior of phthalocyanines (4–6) were proved by
the dominance and the sharpness of the longer wavelength absorp-
ꢀ ꢁꢀ
ꢁ
I
V
d
rdc
¼
ð1Þ
ð2n ꢀ 1Þlh
where (I/V) is slope of the I–V graph, d is distance between the fin-
ger pair, n is number of the finger pair, l is overlap length and h is
thickness of the electrodes.
Fig. 4a and b shows I–V curves of the films of the compounds 4
and 6, during negative to positive and positive to negative voltage
sweeps. As seen from Fig. 4, during negative to positive sweep, cur-
rent values at zero voltage are greater than the values during posi-
tive to negative sweep. Additionally, hysteresis increased as
temperature increased. This behavior probably arises from deep
tions. The B bands of the compounds (4–6) arising from deeper
p
levels to LUMO were observed at 338, 341 and 334 nm, respectively
(Figs. 2 and 3).
Electrical properties
Dc properties
Dc conductivity measurements of the films of the compounds 4,
5, and 6 were done in home-made aluminum chamber at different
temperatures in the temperatures range of 295–523 K in vacuum
(<10ꢀ3 mbar) in dark. Current values passing through the films
were recorded versus applied voltages (between ꢀ1 and 1 voltage
sweep with 50 mV increments) during heating process (I–V
Fig. 2. Absorption spectrum of the metal-free Pc 4 in chloroform at 1 ꢁ 10ꢀ5
M
Fig. 4. I–V curves at the temperatures 298 K and 498 K for the (a) film of the
compound 4 and (b) film of the compound 6.
concentration.

554
R. Bayrak et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 105 (2013) 550–556
traps. The processes require greater time constant for charging and
discharging process. Similar hysteresis was reported earlier [39].
Some parameters such as voltage sweep speed, deep trap level af-
fects hysteresis. The hysteresis at high temperatures suggests that
is due to the formation of space charge polarization in the film.
Hysteresis effect was also observed for the film of the compound 5.
Conductivity of the films of the compounds 4, 5 and 6 was found
as 1.0 ꢁ 10ꢀ9 S/cm, 1.5 ꢁ 10ꢀ10 S/cm and 1.7 ꢁ 10ꢀ10 S/cm at 295 K,
respectively. The conductivity values increased to 8.5 ꢁ 10ꢀ6 S/cm,
9.5 ꢁ 10ꢀ6 S/cm, 1.3 ꢁ 10ꢀ5 S/cm at 523 K, respectively. Experimen-
tal results showed that temperature dependence of the conductivity
data of the films obeys Eq. (2) indicating that the compounds 4, 5 and
6 are semiconductors. The linear relation also shows that the com-
pounds behave as an intrinsic semiconductor in the temperature
range of 295–498 K. After 498 K, a small decrease was observed in
conductivity of the films. It is well known that, structural/composi-
tional lattice defects increases the localized states and that affects dc
conductivity. The change in conductivity behavior with inverse of
temperature after 498 K for the films may attributed to the occur-
rence of a phase transition or presence of different crystallographic
phases [40,41]. Calculated dc conductivity values of the films of the
compounds 4, 5 and 6 exhibited same order of conductivity values
with other reports in different phthalocyanine films [42]. The tem-
perature dependence of the dc conductivity can be expressed by
well-known Arrhenius equation (Eq. (2))
conductivity (rac) of the film increases with increasing tempera-
ture. However, temperature dependence of ac conductivity of the
film can be analyzed in two parts as low temperature region
(T < ꢃ438 K) and high temperature region (T > ꢃ438 K). In low
temperature region (T < ꢃ438 K), conductivity of the film strongly
depends on frequency and increases with increasing frequency.
In high temperature region (T > ꢃ438 K), frequency dependence
of ac conductivity of the film decreases in the measured frequency
range. At all temperatures frequency dependence of the measured
ac conductivity of the films obeys the universal power law. The
universal power law is given by the Eq. (3) [45].
rac ¼ Axs
ð3Þ
where
x
is the angular frequency, A and s are material depended
constants. To gain more information on the charge transport mech-
anism taking place in the films, the variation of the exponent s with
temperature were examined. s values were calculated from slope of
straight portions of the rac versus
x plot.
Calculated values of s for the films of the compound 4, 5 and 6
are around 1.0 at 295 K and decreases to 0.2 at 523 K in the fre-
quency range of
x > 10 kHz. The variation of the s values of the film
the compound 6 with temperature in high frequency region
(>10 kHz) and in low frequency region (610 kHz) was given in
Fig. 6a and of the films the compounds 4, 5 and 6 in high frequency
region in Fig. 6b. As seen from Fig. 6, s values decrease with
increasing temperature.
In the band theory, the ac conductivity does not depend on fre-
quency and drops at sufficiently high frequency. In the hopping
model the electrons in charged defect states hop over the coulomb
barrier. Ac conductivity increases with frequency in this model un-
der the condition that, the frequency exponent s 6 1 [46]. In Corre-
lated Barrier Hopping (CBH) model [46] ac conductivity (first order
approximation) is given by following equation:
ꢀ
ꢁ
ꢀEA
rdc
¼
r0 exp
ð2Þ
kT
where EA is activation energy, T is temperature, k is Boltzmann’s
constant and 0 is a pre-exponent factor of dc conductivity. Activa-
tion energy values of the films were calculated form slope of the
straight portions of the Arrhenius plot (ln dc–1/T curves). The val-
r
r
ues were found as 0.70 eV, 0.91 eV and 0.93 eV for the films of
the compounds 4, 5 and 6, respectively. Our activation energy val-
ues were also exhibited nearly same order of activation energy val-
ues with other reports in different phthalocyanine films such as
0.6–0.9 eV [43,44].
Ac properties
AC conductivity measurements. Ac conductivity measurements of
the films the compounds 4, 5 and 6 were done in home-made alu-
minum chamber at different temperatures in the temperatures
range of 295–523 K in vacuum ambient (<10ꢀ3 mbar) in dark. Ac
conductivity measurements were performed in the frequency
range of 4 ꢁ 10ꢀ2–100 kHz. Frequency dependence of ac conduc-
tivity for the film the compound 6 at different temperatures
(295–523 K) was presented in Fig. 5. It is clearly seen that ac
Fig. 6. Temperature dependence of exponents: (a) for the film of the compound 6 in
high frequency and low frequency region and (b) for the films of the compounds 4, 5
and 6 in high frequency region.
Fig. 5. Frequency dependence of ac conductivity of the film of the compound 6
between the temperatures of 295–523 K.

R. Bayrak et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 105 (2013) 550–556
555
1
24
rac
¼
np
3N2eeoxR6x
ð4Þ
where N is the spatial density of defect states, e and eo are dielectric
constants of the materials and free space, respectively, n = 1 for a
single electron n = 2 for hopping of two electrons and R is the hop-
x
ping distance.
The model developed by Elliot (The CBH model), [46,47], sug-
gests a temperature-dependent s value which is given by following
equation:
6kBT
Wm
s ¼ 1 ꢀ b ¼ 1 ꢀ
ð5Þ
where kB is Boltzmann’s constant and Wm is the binding energy and
T is temperature. In this model s values decreases with increasing
temperature. Our results showed that s is a function of temperature
for all the films and shows a general tendency to decrease with
increasing temperature over the measured frequency and tempera-
ture range. The variation of s with temperature and the variation of
ac conductivity with frequency (Figs. 5 and 6) are in agreement with
the prediction of the hopping model. The same type of temperature
dependence for s was observed in other reports in different phtha-
locyanine films [29]. The quantum-mechanical tunneling (QMT)
model [48], predicts an increase in s with temperature or indepen-
dent of temperature or almost equal to 0.8. In the overlapping-large
polaron tunneling (QLPT) model [47], s values depends on fre-
quency and decreases with increasing temperature to a minimum
value at a certain temperature, then it increases with increasing
temperature. Because of this the models QMT and QLPT are not
applicable to our results. The small polaron quantum mechanical
tunneling (SP) model predicts an increase in s with increasing tem-
perature. [46,47]. According to these models, we can conclude that
charge transport mechanism of the films the compounds 4, 5 and 6
can be modeled by hopping all over the measured frequency and
temperature range.
Fig. 7. The Cole–Cole plot for the film of the compound 4 at temperatures: (a)
T < 458 K and (b) T P 458 K.
the relaxation time is considered as a distribution of values, rather
than a single relaxation time [50]. The depressed semicircles with
different radius indicate deviation from Debye dispersion relation.
Therefore, the equivalent circuit is modified to include a constant
phase element (CPE). The series resistance in the equivalent circuit
represents the ohmic losses in the experimental set-up and sheet
resistance of the electrode. The parallel resistance is the bulk resis-
tance of the coating material. The intercepts of the semicircular
arcs with real axis give us information of the bulk resistance of
the compounds. From Fig. 7, it is observed that bulk resistance de-
creases with increasing temperature indicating semiconductor
property. A monotonic decrease in this resistance suggests that
the increase of temperature lower the barrier for charge transport.
At the temperatures 478 K and 498 K, a straight line was also ob-
served in low frequency region (Fig. 7b). The straight line in the
low frequency region indicates the presence of Warburg compo-
nent [51]. The complex impedance spectrum of the films the com-
pounds 5 and 6 at the temperatures T P 458 K was similar to those
in Fig. 7b.
Impedance measurements. The ac electrical behavior of the films
was also characterized by complex impedance spectroscopy tech-
nique. In this technique a sinusoidal signal at some frequency are
applied to the material and response of the material (impedance
data) are measured. A number of such measurements depending
on frequency and temperature form the response of the material
known as impedance data. The impedance data were represented
by –Z00(
Cole–Cole plot (Nyquist plot), where Z0(
impedance and Z00(
) imaginary component of impedance. Nyquist
x
)–Z0(
x
) curves in complex plane commonly called the
) is real component of
x
x
plot for the film the compound 4 was presented in Fig. 7 at indi-
cated temperatures (in Fig. 7b, x-axis and y-axis was not drawn
in the same scale to show behavior of the curves).
By examining Fig. 7a the impedance spectra can be character-
ized by the semicircular shaped arcs suggesting pure capacitive
behavior. The curves can be modeled by a resistor parallel with a
capacitor in series with another resistor [49]. The films the com-
pounds 5 and 6 also showed same behavior at the temperatures
T < 458 K.
Fig. 7b shows impedance spectra for film the compound 4 at the
temperatures T P 458 K. By examining Fig. 7a and b, we can say
that the curves (in semicircular shaped arc form) in Fig. 7a trans-
forms into full semicircles as in the Fig. 7b with increasing temper-
ature for the film of the compound 4. With the examination of the
Fig. 7b the effect of the temperature on impedance spectra can be
seen clearly. Impedance spectra consist of depressed semicircles
with different radius, additionally, the radius of the semicircle de-
creases with increasing temperature. Peak frequency of the com-
The variation of imaginary parts of impedance with frequency
(
x
) for the films of the compounds 4, 5 and 6 was also investigated.
The –Z00–
x
curves for the film of the compound 5 in the temperature
range of 295–523 K and at high temperatures were presented in
Fig. 8. At low temperatures, ꢀZ00 decreases with increasing fre-
quency, and as frequency approaches to 100 kHz frequency depen-
dence of the impedance quite decreases (Fig. 8a). This behavior
indicates that there is no current dissipation at these temperatures.
At high temperatures, three different remarkable behaviors were
observed. (i) The peaks of the imaginary part of the films were ob-
served. As the temperature increases the curves exhibit peaks at dif-
ferent frequencies. This behavior may be an evidence for the
occurrence of different electrical relaxation times in the film. (ii)
Broadening of the curves was observed with increasing
plete semicircle,
xp, satisfies xpsD = 1. Where sD is time constant
[49]. An ideal semicircle in complex plane only appears in Debye
dispersion relations for single-relaxation time process. In this case,

556
R. Bayrak et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 105 (2013) 550–556
References
[1] C.C. Leznoff, A.B.P. Lever (Eds.), Phthalocyanines Properties and Applications,
vol. 1, VCH Publisher, New York, 1989.
[2] V. Parra, M. Bouvet, J. Brunet, M.L. Rodríguez-Méndez, J.A. Saja, Thin Solid Films
516 (2008) 9012–9019.
[3] M. Bouvet, Anal. Bioanal. Chem. 384 (2006) 366–373.
[4] C.C. Leznoff, A.B.P. Lever (Eds.), Phthalocyanines Properties and Applications,
Vol. 3, VCH Publishers, New York, 1993.
[5] G. De La Torre, P. Vazquez, F. Agullo-Lopez, T. Torres, J. Mater. Chem. 8 (1998)
1671–1683.
[6] F. Yang, S.R. Forrest, Am. Chem. Soc. Nano 2 (2008) 1022–1032.
[7] S.R. Forrest, Chem. Rev. 97 (1997) 1793–1896.
[8] A. Bilgin, B. Ertem, Y. Gök, Polyhedron 24 (2005) 1117–1124.
[9] C.C. Leznoff, A.B.P. Lever (Eds.), Phthalocyanines Properties and Applications,
vol. 2, VCH Publisher, New York, 1993.
[10] M. Emmelius, G. Pawlowski, H.W. Vollmann, Angew. Chem. Int. Ed. 28 (1989)
1445–1471.
[11] C.C. Leznoff, A.B.P. Lever (Eds.), Phthalocyanines, Properties and Applications,
vol. 4, VCH, New York, 1996.
[12] F. Yılmaz, M. Özer, I. Kani, Ö. Bekaroglu, Catal. Lett. 130 (2009) 642–647.
[13] I. Rosenthal, Photochem. Photobiol. 53 (1991) 859–870.
_
[14] I. Degirmencioglu, R. Bayrak, M. Er, K. Serbest, Dyes Pigm. 83 (2009) 51–58.
[15] M. Kandaz, A.T. Bilgiçli, A. Altındal, Synth. Met. 160 (2010) 52–60.
[16] I.N. Tretyakova, V.Ya. Chernii, L.A. Tomachynski, S.V. Volkov, Dyes Pigm. 75
(2007) 67–72.
[17] G. Gümrükçü, M.Ü. Özgür, A. Altındal, A.R. Özkaya, B. Salih, Ö. Bekarog˘lu,
Synth. Met. 161 (2011) 112–123.
[18] J.H. Kiefer, Q. Zhang, R.D. Kern, J. Yao, B. Jursic, J. Phys. Chem. 101 (1997) 7061–
7073.
[19] I. Alkorta, F. Blanco, J. Elguero, Arkivoc 7 (2008) 48–56.
[20] I. Picon-Ferrer, F. Hueso-Urena, N.A. Illan-Cabeza, S.B. Jimenez-Pulido, J.M.
Martinez-Martos, M.J. Ramirez-Exposito, M.N. Moreno-Carretero, J. Inorg.
Biochem. 103 (2009) 94–100.
[21] G. Gürkök, T. Coban, S. Suzen, J. Enzym Inhib. Med. Chem. 24 (2009) 506–515.
[22] G. Gürkök, N. Altanlar, S. Suzen, Chemotherapy 55 (2009) 15–19.
[23] V.B. Kurteva, S.P. Simeonov, M. Stoilova-Disheva, Pharmacol. Pharm. 2 (2011)
1–9.
[24] J. Jayabharathi, V. Thanikachalam, A. Thangamani, M. Padmavathy, Med. Chem.
Res. 16 (2007) 266–279.
Fig. 8. Variation of imaginary part of impedance with frequency for the film of the
compound 5: (a) 295 K 6 T 6 523 K and (b) T P 458 K.
_
[25] R. Bayrak, H.T. Akçay, M. Pisßkin, M. Durmußs, I. Deg˘irmenciog˘lu, Dyes Pigm. 95
(2012) 330–337.
[26] D.D. Perrin, W.L.F. Armarego, Purification of Laboratory Chemicals, Pergamon,
Oxford, 1989.
[27] M. Godara, R. Maheshwari, S. Varshney, A.K. Varshney, J. Serb. Chem. Soc. 72
(2007) 367–374.
[28] G.J. Young, W. Onyebuagu, J. Org. Chem. 55 (1990) 2155–2159.
[29] E. Yabaßs, M. Sülü, S. Saydam, F. Dumludag˘, B. Salih, Ö. Bekarog˘lu, Inorg. Chim.
Acta 365 (2011) 340–348.
[30] H. Uchida, P.Y. Reddy, S. Nakamura, T. Toru, J. Org. Chem. 68 (2003) 8736–
8738.
[31] C.S. Marvel, J.H. Rssweiler, J. Am. Chem. Soc. 80 (1958) 1197–1199.
[32] N. Safari, P.R. Jamaat, S.A. Shirvan, S. Shoghpour, A. Ebadi, M. Darvishi, A.
Shaabani, J. Porphyrins Phthalocyanines 9 (2005) 256–261.
[33] N.P. Farrell, A.J. Murray, J.R. Thornback, D.H. Dolphin, B.R. James, Inorg. Chim.
Acta 28 (1978) 144–146.
temperature. This behavior also suggests the presence of an electri-
cal process with a spread of relaxation times, depending on the tem-
perature. (iii) The peak frequencies shifted towards high frequencies
for the film of the compound 5.
x curves for the films the compounds 4 and 6 were
similar to that of film the compound 5 in the temperature range
The ꢀZ00–
of 295–523 K.
Conclusion
[34] O.E. Sielcken, L.A. Van de Kuil, W. Drenth, J. Schoonman, R.J.M. Nolte, J. Am.
Chem. Soc. 112 (1990) 3086–3093.
_
In the presented work, the syntheses of new aldazine substi-
tuted metal free, zinc(II) and nickel(II) phthalocyanines were de-
scribed and these new complexes were characterized by
elemental analysis, FT-IR, 1H NMR, electronic spectroscopy and
mass spectra and addition to these techniques for substituted pht-
halonitrile 13C NMR have been used. Temperature dependence of
the conductivity data of the films indicates that the compound of
4, 5 and 6 are semiconductors. The calculated activation energy
values were found as 0.70 eV, 0.91 eV and 0.93 eV for the films of
4, 5 and 6, respectively. By examining ac measurement results,
charge transport mechanism of the films can be modeled by hop-
ping all over the measured frequency and temperature range. From
impedance spectra results, it is observed that bulk resistance of all
the compounds decreases with increasing temperature indicating
semiconductor property. The result also supports the dc measure-
ment results.
[35] I. Deg˘irmenciog˘lu, E. Atalay, M. Er, Y. Köysal, Sß. Ißsık, K. Serbest, Dyes Pigm. 84
(2010) 69–78.
[36] Ü. Demirbaßs, R. Bayrak, M. Pißskin, H.T. Akçay, M. Durmußs, H. Kantekin, J.
Organomet. Chem. 724 (2013) 225–234.
_
[37] H.T. Akçay, R. Bayrak, Ü. Demirbasß, A. Koca, H. Kantekin, I. Deg˘irmenciog˘lu,
Dyes Pigm. 96 (2013) 483–494.
[38] R.C. George, M. Durmusß, G.O. Egharevba, T. Nyokong, Polyhedron 28 (2009)
3621–3627.
[39] P.D. Hooper, M.I. Newton, G. McHale, M.R. Willis, Semicond. Sci. Technol. 12
(1997) 455–459.
[40] M.S. Masoud, S.A. El-Enein, E. El-Shereafy, J. Therm. Anal. Calorim. 37 (1991)
365–373.
[41] H. Hassib, A.A. Razik, Solid State Commun. 147 (2008) 345–349.
[42] Z. Odabasß, E.B. Orman, M. Durmusß, F. Dumludag˘, A.R. Özkaya, M. Bulut, Dyes
Pigm. 95 (2012) 540–552.
[43] R.C. Cherian, C.S. Menon, J. Phys. Chem. Solids 69 (2008) 2858–2863.
[44] Z. Odabasß, F. Dumludag˘, A.R. Özkaya, S. Yamauchi, N. Kobayashi, Ö. Bekarog˘lu,
Dalton Trans. 39 (2010) 8143–8152.
[45] M. Pollak, T.H. Geballe, Phys. Rev. 122 (1961) 1742–1754.
[46] S.R. Elliot, Adv. Phys. 36 (1987) 135–218.
[47] A.R. Long, Adv. Phys. 31 (1982) 553–637.
[48] A. Ghosh, Phys. Rev. B 41 (1990) 1479–1488.
[49] E. Barsoukov, J.R. Macdonald, Impedance Spectroscopy Theory, Experiment
and Applications, second ed., John Wiley & Sons Inc., 2005.
[50] Y.J. Chen, X.Y. Zhang, T.Y. Cai, Z.Y. Li, J. Alloys Compd. 379 (2004) 240–246.
[51] F. Josse, R. Lukas, R. Zhou, S. Schneider, D. Everhart, Sens. Actuators B – Chem.
36 (1996) 363–369.
Acknowledgement
The authors thank to The Research Fund of Karadeniz Technical
University, Projects No: 2010.111.002.8 (Trabzon/Turkey).