Advances in Materials Physics and Chemistry, 2011, 1, 57-63
doi:10.4236/ampc.2011.13010 Published Online December 2011 (
Copyright © 2011 SciRes. AMPC
Intense Visible Photoluminescence from C46H22N8O4KM
(M = Co, Fe, Pb) Derivatives Thin Films
María Elena Sánchez1, Juan Carlos Alonso2, Jerry Nathan Reider1
1Faculty of Engineering, Anáhuac México Norte University, Huixquilucan, Estado de México, México
2Materials Research Institute, National Autonomous University of México (UNAM), Coyoacán, México
Received August 3, 2011; revised September 27, 2011; accepted October 7, 2011
Strong visible photoluminescence (PL) at room temperature is obtained from thermal-evaporated thin solid
films of Metallophthalocyanine (M = Co, Fe, Pb) and double potassium salt from 1,8-dihydroxyan-
thraquinone. The PL of all the investigated samples is observed with the naked eye in a bright background.
The deconvolution of the normalized PL spectra shows that each PL spectrum is composed of four emission
bands which peak at approximately the same energies of 2.1, 2.2 and 2.4 eV and whose intensities and
widths depend upon the structure of the complexes. FTIR and ellipsometry are employed to investigate the
structural differences among the films. The optical absorption of the films is also investigated to evaluate the
changes in the electronic structure of these metal organic compounds, with respect to other metalphtalocya-
nines thin films. Our results suggest that the visible PL comes from radiative transitions between energy lev-
els associated to the double potassium salt coordination to the metallic ion in the phthalocyanine.
Keywords: Thin Films, Optical Properties, Photoluminescence
1. Introduction
Since the report, more than two decades ago, of efficient
electroluminescence (EL) from organic thin films [1], the
use of small organic molecules and organic polymers in
the fabrication of organic light emitting diodes (OLED’s)
attracts considerable interest for solid state displays and
lighting applications [2]. A typical OLED comprises a
luminescent organic thin film sandwiched in-between an
electron transport layer and a hole transport layer bound
by two electrodes. One of the foremost class of planar
organic molecular semiconductors, used as electron or
hole transport layer, is that of the metallophthalocyanines
(MPcs). Optical properties of these materials, among
them the luminescence, are strongly related to the va-
lence band electronic configuration, as well as the exci-
tation and the de-excitation processes between highest
occupied molecular orbitals (HOMO) and lowest unoc-
cupied molecular orbitals (LUMO) [3]. The optical pro-
perties of MPcs are very important for understanding
their molecular structure and improving the performance
of devices made with phthalocyanines.
In thin films, MPcs usually present a given crystalline
form or may be amorphous depending mainly upon the
molecular self-stacking ability of the derivate, but also
upon the thin film fabrication procedure [4]. Moreover,
the control of film structure is of great importance in thin
film technology since the opto-electronic properties such
as the photogeneration of charge carriers, highly depends
on the degree of molecular organization [4]. In thin films,
molecules crystallize and their interaction is significant,
so that dramatic changes occur in their optical properties,
making them much more complicated [5]. Since these
organic materials in the solid film form are applied in the
production of the majority of modern optoelectronic de-
vices, the knowledge of their excited electronic states
and relaxation processes is particularly important [5].
Photoluminescence (PL) properties in the solid (or crys-
talline) phases have been investigated for only a few
MPcs materials such as H2Pc, ZnPc, AlClPc, VOPc,
TiOPc, MgPc and AlBrPc [6]. PL is a powerful probe for
assessing the excited states, because useful information
can be obtained by measuring its properties such as
quantum yields, spectra, time decay, and temperature
dependence [6]. For the electroluminescence (EL) appli-
cation, PL properties provide important reference data,
because the EL spectra and the EL emission efficiencies
of the materials can be estimated through the corre-
sponding PL spectra and the quantum yields. Therefore,
it is important to investigate PL phenomena of MPc
compounds in the solid phases, whereas the lumines-
cence of most of these organic compounds lies in the red
and near-infrared regions and with low efficiency at
room temperature [7-9]. Studies on the optical properties
of phthalocyanine-derived thin films show that the opti-
cal absorption and luminescence of these new organic
compounds with complex structures can be tailored
and/or modified to decrease or increase the near-IR lu-
minescence efficiency [10-13], and even produce polar-
ized red luminescence [14] or strong blue photolumines-
cence [15]. In this paper, we report intense photolumi-
nescence from MPcs-derived thin films prepared by
vacuum thermal evaporation of semiconductor powders
from iron, lead and cobalt phhalocyanines with a double
potassium salt derived from 1,8-dihydroxyanthraquinone
(K2C14H6O4). Vibrational spectra are obtained and the
refractive indices and absorption coefficients are deter-
mined for the studied samples.
2. Experimental Details
The raw materials used in this work are obtained from
commercial sources with no purification prior to their use.
The powders of the three compounds; C46H22N8O4KFe,
C46H22N8O4KPb and C46H22N8O4KCo, are synthesized
from metallic phthalocyanines and double potassium salt
derived from 1,8-dihydroxianthraquinone, using the pro-
cedure reported previously [16]. Thin film deposition of
these compounds is carried out by vacuum thermal evapo-
ration onto Corning 7059 glass slices and (100) single-
crystalline silicon (c-Si), 200 ·cm wafers. The sub-
strate temperatures are kept at 298 K during deposition.
The Corning 7059 substrates are ultrasonically degreased
in warm ethanol and dried in a nitrogen atmosphere. The
silicon substrates are chemically etched with a p-etch
solution (10 ml HF, 15 ml HNO3, and 300 ml H2O) in
order to remove the native oxide from the c-Si surface.
The evaporation source is a molybdenum boat with two
grids. The temperature through the molybdenum boat is
slowly increased to 453 K, below the first significant
signal change observed in the thermo-gravimetric analysis
thermogram, in order to prevent thermal decomposition
of the compound and to identify the phase changes
(evaporation, sublimation). All samples are obtained
using the same deposition system, with the crucible and
substrates arranged in the same geometry. The base
pressure in the deposition chamber before thin film
deposition and the amount of mass inside the crucible are
the same in all cases. In spite of these similarities, sig-
nificant differences in the thickness of deposited films
are detected, which may be related to differences in the
sublimation processes for the compounds used. An
atomic force microscope (AFM) coupled to a potentio-
stat/galvanostat module from Digital Instruments is also
used to investigate the morphology of the thin films. A
Gaertner L117 Ellipsometer equipped with a He-Ne laser
(λ = 632.8 nm) is used to measure the thickness and re-
fractive index of the films. The thickness of the films is
also measured by means of a Sloan Dektak IIA pro-
filometer. The chemical bonding behavior is analysed by
means of a Fourier transform infrared (FTIR) spectro-
photometer (Nicolet-210). Photoluminescence (PL) meas-
urements are carried out in a dark room at room tem-
perature, using a beam (
= 325 nm, 25 mW) from a
Kimmon He-Cd laser as excitation source, with an inci-
dent angle of 45˚ relative to the normal of the sample.
The luminescence is collected at an angle normal to the
sample using a quartz optic fiber and measured in the
range from 350 nm to 800 nm with a Fluoromax-Spex
spectrofluorometer. Ultraviolet-visible (UV-Vis) trans-
mission measurements are carried out in the range from
300 to 1100 nm using a double-beam PerkinElmer Lambda
35 UV-Vis spectrophotometer. For PL, infrared and el-
lipsometric measurements the substrates used are (100)
oriented c-Si slices with 200 ·cm resistivity. For AFM
and optical transmission measurements, the substrates
are naked 7059 Corning glass slices. The electric con-
ductivity at 298 K of the films is studied by means of a
four-point probe; for these measurements, the sub-
strates are Corning 7059 glass slices coated with four
metallic strips acting as electrodes. The strips are depos-
ited by thermal evaporation. In order to get an ohmic
contact with the deposited films, the electrodes are made
from silver.
3. Results and Discussion
The purpose of IR spectroscopy on thin films is deter-
mining if there were significant chemical changes on the
MPcs-derived compounds during the thermal evapora-
tion used to prepare the films. However, chemical
charges or reactions are not expected to occur owing to
the thermal stability present in these compounds. Table 1
shows the characteristic bands for these compounds on
thin film. These results appear to indicate that the depos-
ited compound is not affected by the thermal evaporation
and deposition processes during film growth. The depos-
ited films are formed by the same macro-ions as those of
the original synthesized powder, as indicated by com-
parison between the location of the absorption bands in
the spectra of the synthesized powders, and those of the
deposited films [16]. When compounds have the film
form, the signs show slight changes in their location be-
cause, in all thin films deposited by any method, there
Copyright © 2011 SciRes. AMPC
Copyright © 2011 SciRes. AMPC
Table 1. Characteristic FT-IR bands for powders and thin films (cm–1).
COMPOUND (C-H) (cm–1) (C-C) (cm–1) (C-N) (cm–1) (C=O) (cm–1) (C-O) (cm–1)
C46H22N8O4KFe Thin Film 3049, 2851 1610, 630 1284, 1157, 1070 1606 1089
C46H22N8O4KFe KBr pellet 3048, 2855 1607, 632 1285, 1158, 1070 1604 1091
C46H22N8O4KPb Thin Film 3048, 2851 1603, 623 1277, 1156, 1077 1602 1087
C46H22N8O4KPb KBr pellet 3050, 2853 1608, 626 1274, 1159, 1079 1602 1088
C46H22N8O4KCo Thin Film 3045, 2852 1605, 625 1287, 1161, 1071 1609 1085
C46H22N8O4KCo KBr pellet 3044, 2849 1608, 628 1284, 1164, 1070 1610 1083
are inner stresses that affect the angles and energies of
intramolecular bonds. Table 1 shows the signs corre-
sponding to macrocycle [17,18]: two bands appearing at
about 3048 and 2854 cm–1 are assigned as CH (symmet-
ric stretching vibrations in the ring and asymmetric
stretching vibrations as alkyl). The band appearing at
1609 cm–1 is assigned to the C-C stretching vibration in
pyrrole. Additionally, the band appearing at 625 cm–1 is
assigned the C-C macrocycle ring deformation. The bands
appearing at 1284, 1161 and 1070 are assigned to the
C-N in isoindole in plane band in pyrrole stretching vi-
bration, respectively. The spectral pattern in this region
depends strongly upon the molecular structure of the
complexes and its chemical structure for the central metal
with D4h molecular symmetry [18]. It may be noticed
[16] that the materials from the MPc and double potas-
sium salt derived from 1,8-dihydroxyanthraquinone ex-
hibit C=O and C-O functional groups with wavelengths
1600 cm–1 and 1080 cm–1, respectively [16-19]. Due to
the bond of phtalocyanine to the potassium double salt
anion (C14H6O4)2–, a characteristic band around 1662
cm–1 assigned to the elongation vibration of carbonile
group C=O in the quinones is observed. In addition, the
band near 1083 cm–1 corresponding to the C-O elonga-
tion vibration is present, as well [16-19].
In order to obtain information about the quality of the
films we investigate the surface morphology by AFM.
The AFM analysis of the evaporated films displays a
homogeneous distribution of small spherical aggregates.
The RMS roughness values are shown in Table 2. The
refractive indices (n) of the films, obtained from ellip-
sometric measurements are shown in Table 2, as well as
the reflectance percentages at normal incidence, calcu-
lated using the equation:
100 11Rnn 
fraction indexes. It is noticed that at thin thicknesses all
the photoluminescence (PL) spec-
The refraction index, as well as the reflectance, de-
pend upon the thickness of the thin film: the lead-based
film is the one which shows the least thickness, associ-
ated with higher values for both the reflectance and re-
films become transparent and no light is scattered or ab-
sorbed. The electrical conductivity of each material is
evaluated at 25˚C. These results are shown in Table 2
with the C46H22N8O4KCo material presenting the highest
conductivity. Generally, the conductivity at room tem-
perature decreases when increasing the atomic number of
the central metal except Fe. This may be due to the
change of chemical structure of Fe and it takes place for
Fe2+ and Fe3+ [18]. Besides, electrical conductivity val-
ues at room temperature for all materials are in the elec-
trical conductivity range for semiconducting molecular
materials (10–6 to 101 S·cm–1) [16]. This is important
since a molecular semiconductor is generally defined in
terms of its conductivity at room temperature and its be-
havior with temperature. Conductivity is also related to
impurity types, location and concentration, structure,
stacking and overlaps between orbitals. The charge
transfer in these compounds, occurs via phthalocyanine
rings that stacks, generating a direct - interaction be-
tween adjacent molecules in the pile, but very weak in-
teractions between molecules in adjacent piles. The elec-
tric charges transport on them is due to the highly or-
dered structure that form; apparently there is a marked
anisotropy as a consequence of the stacking of phthalo-
cyanine columns in columnar piles, along which the
electric charges flow.
Figure 1(a) shows
of the films, obtained at room temperature (300 K). It
is evident from Figure 1(a) that these films exhibit lu-
minescence in the visible region. These results are im-
portant since most of the reports and studies on the lu-
minescence of this type of metal organic compounds are
made in the IR region. The PL spectra of the three sam-
ples show two main central peaks and two side shoulders
located at similar wavelengths but with different intensi-
ties. The absorbance (A) spectra of the films (Figure
1(b)) show more complicated structure with optical ab-
sorption peaks and edges distributed in the wavelength
range from infrared to ultraviolet. It is well known that the
absorption spectrum for phthalocyanines originates from
molecular orbitals within the aromatic 18π electron system
kness, refraction index, reflectance and electrical conductivity
rical parameters C46H22N8O4KFe C46H22N8O4KPb C46H22N8O4KCo
Table 2. AFM evaluation of the thin film roughness, film thic
results for thin films.
Optical and Elect
RMS roughness (nm) 84.79 74.37 89.54
Film thickness (nm) 133 108 170
Refraction index 2.6 2.9 2.1
% Reflectance 19 24 12
Electrical conductivity(S/cm) 1.57E 1.36E–5 4.96E
at 298 K –5–5
nd from overlapping orbitals on the central metal atom
te the origin of the visible photo-
on band in the UV
in the visible region have been generally been interpreted a
[17]. The compounds C46H22N8O4KPb and C46H22N8O4KFe
exhibit a similar behavior in the visible region in compari-
son with C46H22N8O4KCo. This, in turn, can be explained
by the different electronic configuration of the central me-
tallic ion and the number of electrons in the outer level: 3d6
for C46H22N8O4KFe, 6S2 for C46H22N8O4KPb and 3d7 for
C46H22N8O4KCo [18].
In order to investiga
minescence and the relationship with the optical ab-
sorption and electronic structure of these thin films, the
PL and absorbance spectra of Figure 1 were plotted to-
gether in an overlapping scheme in terms of photon en-
ergy. These plots are presented in Figure 2. Since the
analyzed samples have different thicknesses (see Table 2)
and the PL intensity depends upon this parameter, the PL
spectra of Figure 2 are normalized relative to the maxi-
mum intensity in order to neglect this dependence. As
can be seen from these plots, there is strong absorbance
for the three samples at the energy of the excitation
source photons (marked with an arrow). This means that
the photons from the excitation source are efficiently
absorbed by the samples, which partly explains their ef-
ficient PL. It is interesting to note that the start and end
energies (also marked with arrows in the spectra) of the
main photoluminescence band correspond to energies
where optical absorption bands or edges lie. These ener-
gies are similar for the three samples.
A close examination of the absorpti
gion, which is known as the Soret band or the B-band
(3 - 4.5 eV) [20], reveals one peak around 3.8 eV for
C46H22N8O4KFe, C46H22N8O4KPb and C46H22N8O4KCo
(see Figure 2 and Table 3). This strongly indicates the
presence of a d-band associated with the central metal
atom. This is because PcM(L) has partially occupied d
bands. The absorption band near 4.0 eV may be due to
π-d transition. The other well-know band of the phthalo-
cyanine molecule, namely Q-band, appears in the region
between 1.4 and 2.6 eV. The Q-band is split into two
distinct peaks in the visible region due to molecule ag-
gregation or molecular distortion [20]. As observed from
Figure 2, the distinct characterized peaks for thin films
in terms of π-π* excitation between bounding and anti-
bounding molecular orbitals [20]. The Q-band consists of
a high-energy peak around 2.6 eV and a low energy
shoulder at 1.6 eV. The high-energy peak of the Q band
is assigned to the first π-π* transition on the phthalocya-
nine macrocycle. The low-energy peak of the Q band is
explained either, as a second π-π* transition, as an exci-
Figure 1. (a) Photoluminesced (b) absorbance spectra
of C46H22N8O4KCo, C46H22N8 4KPb, C46H22N8O4KFe, thin
nce an
Copyright © 2011 SciRes. AMPC
Figure 2. Normalized PL and absorbance versus photon
energy of (a) C46H22N8O4KCo, (b) C46H22N8O4KPb, (c)
CHN O KFe, thin films.
and is associated to the dou-
Thin films of iron, lead and cobalt phthalocyanines and
salt derived from 1,8-dihydroxian-
thraquinone are deposited by vacuum thermal evapora-
46 228 4
tation peak, as a vibrational internal interval and as a
urface state [20]. The Q-bs
ble potassium salt coordination to the metallic ion in the
phthalocyanine. The presence of this absorption band
may be interpreted as an overlapping of π orbitals
through the bidentate ligand. The conjugated double
bonds within the structure of the films create electron
orbitals overlapping between the molecules (π orbitals).
Electrons are therefore able to transfer energy throughout
the structure and become responsible for the absorption
spectra [20]. The normalized PL spectra are deconvo-
luted with four Gaussian functions, as shown in Figure 3.
As can be seen, the four Gaussian functions peak at ap-
proximately the same energies of 2.1 eV (orange), 2.2 eV
(yellow) and 2.3 eV (green), whose intensities and
widths depend upon the specific metal in the complexes
organic structure. Table 3 summarizes the energy posi-
tions of all the absorption peaks and luminescent peaks
of the samples. Although the curves are maximum emis-
sion peaks, close together in their energy value, it shows
greater luminescence for the lead-based compound. This
was due to the location of the electrons in the final en-
ergy level of Pb2+ in the macrocycle. The compounds of
Fe2+and Co2+ have similar values for the area beneath the
curve, taking into account the available 3d electrons.
According to our data, the PL in phthalocyanine thin
films is substantially affected by the intramolecular
structure. The different metallic ions in the phthalocya-
ne produce differences in the PL peak in the visible
range [21]. The incorporation of metallic ions in the
phthalocyanine molecule (Fe2+, Co2+, Pb2+) may affect
the intensity and width of the peak, but it does not sig-
nificantly change the general structure of the molecule.
In this case, the divalent cation Pb2+ exhibits the largest
absorption peaks energy, probably due to the fact that the
outermost orbital in this cation is completed and reflects
the electrostatic nature of the coordination process in
these films. Nevertheless, the PL peaks obtained in these
materials are higher than the pure analog metallic com-
plexes [13,14], suggesting that the addition of the double
potassium salt from 1,8-dihydroxyanthraquinone im-
proves the photoluminescence (PL) at room temperature.
It is possible that the ligand increase in the anisotropy
arises from a columnar disposition of the phthalocya-
4. Conclusions
double potassium
tion. According to the IR spectra, they are formed by the
same chemical units as those of the corresponding syn-
thesized powders. The conductivity results for materials
C46H22N8O4KFe, C46H22N8O4KPb and C46H22N8O4Kco
are 1.57 × 10–5 S·cm–1, 1.36 × 10–5 S·cm–1 and 4.96 ×
10–5 S·cm–1. All the investigated thin films exhibit strong
emission in the visible region. Our results suggest that
the visible PL in these complex molecules is originated
Copyright © 2011 SciRes. AMPC
Figure 3. Gaussian fitting of the normalized PL spectra o
(a) C46H22N8O4KCo, (b) C46H O4KPb, (c) C 46H22N8O4KFe
thin films.
cyanines, which generate energy levels where
diative transitions can occur. The PL and absorption
by the split and broadening of the Q and Soret bands of
the phthalo
Table 3. Absorption and emission energies of the thin films.
peaks energy
peaks energy
PL intensity.
Area under curve
(eV) (eV) (A.U.)2
C46H NOKPb 1
22 84.4, 1.7, 1.91,
2.6, 3.5, 3.8 2.2, 2.1 6.04 × 105
C46H22N8O4KCo 1.6,.0, 2. 2. 5
C46H22N8O4KFe 2.3, 2.1 3.9 × 10
1.8, 2
2.6, 3.4, 3.8
1.7, 1.9, 2.2,
3, 2.1 7 × 10
2.6, 3.8 5
spect t inoms stroflu-
enced by oures ahe ne-
llic ion has smaller influence on the transition energies
The authors wish to acknowledge Juan Manuel Garcia
or his technical assistance.
[1] C. W. Tang and S. A. VanSlyke, “Organic Electrolumi-
,” Applied Physics Letters, Vol. 51, No. 12,
Lighting in Luminescent Materials
al Properties of Magnesium Phtha-
ra inhe
their m
vestigated c
lecular struct
pounds i
nd t
ngly in
ature of m
of the Q and Soret bands. These organic thin films can be
used as electroluminescent materials in OLEDs and this
application is subject for further studies.
5. Acknowledgements
León and Arturo Rodriguez f
6. References
nescent Diodes
1987, pp. 913-9
[2] T. K. Hatwar and J. Spindler, “Development of White
OLED Technology for Application in Full-Color Dis-
plays and Solid-State
and Applications,” In: A. Kitai, Ed., Luminescent Materi-
als and Applications, John Wiley & Sons Ltd., West
Sussex, pp. 111-159.
[3] N. Peltekis, B. N. Holland, S. Krishnamurthy, I. T.
McGovern, N. R. J. Poolton, S. Patel and C. McGuinness,
“Electronic and Optic
locyanine (MgPc) Solid Films Studied by Soft X-Ray
Excited Optical Luminescence and X-Ray Absorption
Spectroscopies,” Journal of the American Chemical Soci-
ety, Vol. 130, No. 39, 2008, pp. 13008-13012.
[4] T. Del Caño, V. Parra, M. L. Rodríguez Méndez, R. F.
Aroca and J. A. De Saja, “Characterization of Ev
trivalent and Tetravalen
t Phthalocyanines Thin Films:
Different Degree of Organization,” Applied Surface Sci-
ence, Vol. 246, No. 4, 2005, pp. 327-333.
[5] M. Wojdyla, W. Bala, B. Derkowska, M. Rebarz and A.
Korcala, “The Temperatura Dependence
nescence and Absorption Spectra of Vacuum-Sublimed
of Photolumi-
Magnesium Phthalocyanine Thin Films,” Optical Materi-
als, Vol. 30, No. 5, 2008, pp. 734-739.
[6] Y. Sakakibara, R. N. Bera, T. Mizutani, K. Ishida, M.
Copyright © 2011 SciRes. AMPC
Copyright © 2011 SciRes. AMPC
ence Properties of
oaluminum, and Metal-
Tokumoto and T. Tani, “Photoluminesc
Magnesium, Chloroaluminum, Brom
Free Phthalocyanine Solid Films,” Journal of Physical
Chemistry B, Vol. 105, No. 8, 2001, pp. 1547-1553.
[7] J. H. Sharpand and M. Lardon, “Spectroscopic Charac-
terization of a New Polymorph of Metal-Free Phth
cyanine,” Journal of Phy
sical Chemistry, Vol. 72, No. 9,
, Vol. 34, No. 2, 1973, pp. 441-445.
pp. 3230-3235.
[8] K. Yoshino, M. Hikida and K. Tatsuno, “Emission Spec-
tra of Phthalocyanine Crystals,” Journal of the Physical
Society of Japan
[9] M. S. Liao and S. Scheiner, “Electronic Structure and
Bonding in Metal Phthalocyanines, Metal = Fe, Co
Cu, Zn, Mg,” The Journal
, Ni,
of Chemical Physics, Vol. 114,
No. 22, 2001, pp. 9780-9791.
[10] B. Blanzat, C. Barthou and N. Tercier, “Energy Transfer
in Solid Phases of Octasubst
rivatives,” Journal of t
ituted Phthalocyanine De-
he American Chemical Society,
Vol. 109, No. 24, 1987, pp. 6193-6194.
[11] W. H. Flora, H. K. Hall and N. R. Armstrong, “Guest
Emission Processes in Doped Organic Ligh
Diodes: Use of Phthaloc
yanine and Naphthalocyanine
Near-IR Dopants,” Journal of Physical Chemistry B, Vol.
107, No. 5, 2003, pp. 1142-1150. doi:10.1021/jp021368g
[12] T. Del Caño, J. A. Sajab and R. Aroca, “Emission En-
hancement in Chlorogallium Phthalocyanine-N,N9-Bis
(Neopentyl)-3,4,9,10-Perylenebis(Dicarboximide) Mixed
Films,” Thin Solid Films, Vol. 425, No. 1-2, 2003, pp.
292-296. doi:10.1016/S0040-6090(02)01107-0
[13] W. Freyer, C. Neacsu and M. Raschke, “Absorption,
Luminescence, and Raman Spectroscopic Properties of
Thin Films of Benzo-Annelated Metal-Free Porphyrazi-
nes,” Journal of Luminescence, Vol. 128, No. 4, 2008, pp.
661-672. doi:10.1016/j.jlumin.2007.11.070
[14] D. Yan, S. Qin, L. Chen, J. Lu, J. Ma, M. Wei, D. G.
Evans and X. Duan, “Thin Film of Sulfonated Zinc
Phthalocyanine/Layered Double Hydroxide for Achiev-
ing Multiple Quantum Well Structure and Polarized Lu-
minescence,” Chemical Communications, Vol. 46, No. 45,
2010, pp. 8654-8656. doi:10.1039/c0cc02129f
[15] Y. Zhang, X. Sun, Y. Niu, R. Xu, G. Wang and Z. Jian,
“Synthesis and Characterization of Novel Poly(Aryl
Ether ketone)s with Metallophthalocyanine Pendant Unit
from a New Bisphenol Containing Dicyanophenyl Side
Group,” Polymer, Vol. 47, No. 5, 2006, pp. 1569-1574.
[16] M. E. Sánchez-Vergara, M. A. Ruiz Farfán, J. R. Álvarez,
A. Ponce Pedraza, A. Ortiz and C. Álvarez-Toledano,
“Electrical and Optical Properties of C46H22N8O4KM (M
= Co, Fe, Pb) Molecular-Material Thin Films Prepared by
the Vacuum Thermal Evaporation Technique,” Spectro-
chimica Acta Part A: Molecular and Biomolecular Spec-
troscopy, Vol. 66, No. 3, 2007, pp. 561-567.
[17] G. Socrates, “Infrared and Raman Characteristic Group
and Z. A. El Sayed, “FTIR,
Frequencies: Tables and Charts,” 3rd Edition, John Wiley
and Sons, Hokoben, 2001.
[18] R. Seoudi, G. S. El-Bahy
TGA and DC Electrical Conductivity Studies of Phthalo-
cyanine and Its Complexes,” Journal of Molecular Struc-
ture, Vol. 753, No. 1-3, 2005, pp. 119-126.
[19] M. E. Sánchez Vergara, A. Ortiz Rebollo, J. R. Alvarez
and M. Rivera, “Molecular Materials Derived from MPc
(M = Fe, Pb, Co) and 1,8-Dihydroxiantraquinone Thin
Films: Formation, Electrical and Optical Properties,”
Journal of Physics and Chemistry of Solids, Vol. 69, No.
1, 2008, pp. 1-7. doi:10.1016/j.jpcs.2007.07.084
[20] M. M. El-Nahass, A. M. Farag, K. F. Abd El-Rahman
and A. A. A. Darwish, “Dispersion Studies and Elec-
tronic Transitions in Nickel Phthalocyanine Thin Films,”
Optics & Laser Technology, Vol. 37, No. 7, 2005, pp.
513-523. doi:10.1016/j.optlastec.2004.08.016
[21] G. A. Kumar, J. Thomas, N. George, B. A. Kumar, P. Rad-
hakrishnan, V. P. N. Nampoori and C. P. G. Vallabhan, “Op-
tical Absorption Studies of Free (H2Pc) and Rare Earth
(RePc) Phthalocyanine Doped Borate Glasses,” Physics and
Chemistry of Glasses, Vol. 41, No. 2, 2000, pp. 89-93.