New anthracene-based-phtalocyanine semi-conducting materials: Synthesis and optoelectronic properties

Article abstract of DOI:10.1016/j.materresbull.2015.11.010

A new anthracene-based semi-conducting phtalocyanines AnPc and AnPc-Tr were synthesized in solvent-free conditions. The supramolecular structure of these compounds was confirmed by NMR and FT-IR spectroscopies. Their optical properties were investigated by UV-vis and photoluminescence spectroscopies. The optical gaps were estimated from the absorption-onsets films, and the obtained values were of 1.50 eV and 1.47 eV for AnPc-Tr and AnPc respectively. In solid state, a weaker π-π-interactions of conjugated systems were obtained in the case of AnPc-Tr in comparison with AnPc. This behavior was explained by steric hindrance of triazol groups, which decrease the planarity of macromolecular structure. The HOMO and LUMO levels were estimated using cyclic voltammetry analysis; two phtalocyanine derivatives show a comparable ionization potential. The phtalacyanine containing triazole groups (AnPc-Tr) reveals a higher electron affinity in comparison with AnPc. Single-layer diode devices were fabricated and showed relatively low turn-on voltages.

Full text of DOI:10.1016/j.materresbull.2015.11.010

Accepted Manuscript
Title: New anthracene-based-phtalocyanine semi-conducting
materials: Synthesis and optoelectronic properties
Author: M.S. Kahouech K. Hriz S. Touaiti J. Bassem
PII:
S0025-5408(15)30203-8
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.materresbull.2015.11.010
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Accepted date:
7-7-2015
4-11-2015
8-11-2015
Please cite this article as: M.S.Kahouech, K.Hriz, S.Touaiti, J.Bassem,
New anthracene-based-phtalocyanine semi-conducting materials:
Synthesis and optoelectronic properties, Materials Research Bulletin
http://dx.doi.org/10.1016/j.materresbull.2015.11.010
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New anthracene-based-phtalocyanine semi-conducting materials: Synthesis
and optoelectronic properties
1
2,
1
1
M.S. Kahouech , K. Hriz *, S. Touaiti , J. Bassem
1Laboratoire de Chimie Organique et Analytique, Institut Supérieur de l’Education et de la
Formation Continue, 2000 Bardo, Tunisia (Université de Monastir)
2Laboratoire des Interfaces et Matériaux Avancés (LIMA), Faculté des Sciences de Monastir
(Université de Monastir), Bd. de l’Environnement, 5019 Monastir, Tunisia
*
Correspondence to Khaled Hriz. Tel.: +216 73 500 280; Fax: +216 73 500 278. E-mail
address: khaledhriz@gmail.com
1
/32

Graphical abstract
2
/32

Highlights




Synthesis of tow phtalocyanines based on the anthracene and tetrazole.
Semi-conducting supramolecular material.
Good PL quantum yield.
The film morphology of the phtalocynine containing tetrazole group enhanced the
carrier mobility.
3
/32

Abstract
A new anthracene-based semi-conducting phtalocyanines AnPc and AnPc-Tr were
synthesized in solvent-free conditions. The supramolecular structure of these compounds was
confirmed by NMR and FT-IR spectroscopies. Their optical properties were investigated by
UV-visible and photoluminescence spectroscopies. The optical gaps were estimated from the
absorption-onsets films, and the obtained values were of 1.50 eV and 1.47 eV for AnPc-Tr
and AnPc; respectively. In solid state, a weaker --interactions of conjugated systems were
obtained in the case of AnPc-Tr in comparison with AnPc. This behavior was explained by
steric hindrance of triazol groups, which decrease the planarity of macromolecular structure.
The HOMO and LUMO levels were estimated using cyclic voltammetry analysis; two
phtalocyanine derivatives show a comparable ionization potential. The phtalacyanine
containing triazole groups (AnPc-Tr) reveals a higher electron affinity in comparison with
AnPc. Single-layer diode devices were fabricated and showed relatively low turn-on voltages.
Keywords: A. Semiconductors, A. Thin films, B. Chemical synthesis, B. optical properties,
C. electrochemical measurements.
4
/32

1
. Introduction
Metallo-Phtalocyanines (MPcs) have a conjugated two-dimensional 18 π -electron system
which allows the incorporation of more than 70 different metal or non-metal ions into their
inner core they have had this specificity since their first synthesis at the beginning of the last
century [1]. the most important artificial structural analogous of porphyrins, has many
properties arising from their electronic delocalization and make these compounds applicable
to different fields of materials science; such as opto-electronic devices [2], liquid crystals [3],
as electrochromic substances [4], gas sensors [5], blood sterilization, sunlight activated
herbicides and insecticides [6-7], cancer therapy (photodynamic therapy) such as the second-
generation photosensitizer which is now at trial stage [8]. Despite the frequent and
considerable use of individual phtalocyanine (Pc) as chromophores, multichromophoric
systems where Pc are covalently linked to other electro or photoactive units such as organic
moieties that have fluorescent nature and which are of great interest [9]. These systems can
also serve as models for the study of energy and electron-transfer processes in artificial
photosynthetic systems.
Pcs derivatives that absorb at various wavelengths of visible light and fluorescence with high
efficiency and are good candidates for organic photoelectronic devices such as
photosensitizing solar cells [10] and organic light emitting diodes [11]. The purpose of the
Substitution of Pcs was to improve material properties and to facilitate the implementation
and application. Phtalocyanines exhibit excellent chemical and photochemical properties, but
have poor fluorescent properties [12]. The interaction of a fluorescence probe with a
phtalocyanine core may change the fluorescent characteristics of the aromatic structure. For
example, it may be the binding process where fluorescent probe bind chemically or physically
to the phtalocyanine molecules, thereby causing a shift in their fluorescence spectra or a
change in the fluorescence intensity [13-14]. In this paper we report the synthesis and
characterization of two Zn(II) phtalocyanine derivatives substituted by either four anthracene
AnPc or four triazol anthracene AnPc-Tr. This choice was made for the good opto-electronic
properties of anthracene. This is the first aromatic material employed in organic light emitting
diode (OLEDs). The first experiments were carried out by Pope in the early 1960s [15]. Soon
after, several reports on single-crystal anthracene-based OLEDs were published and good
quantum yields were obtained (up to 5 %). Nevertheless, such devices are thick therefore they
require very high operating voltage (over 100 V) and also semi-conductor layer in organic
5
/32

field effect transistor (OFET) [16]. The introduction of the triazol group aims to improve the
optical properties, triazol derivatives have attracted considerable interest in OLEDs because
of their electron transporting as well as hole blocking and/or exciton confining properties, to
improve the quantum efficiency and lower the operating voltage of OLEDs [17].
2
2
. Experimental
.1 Materials and measurements
Phtalic anhydride (99%, sigma aldrich), 9-(chloromethyl)anthracene (98%, Acros), sodium
azide (99.5%, sigma), propargyl alcohol (99%, Aldrich), sodium ascorbate (98%, sigma),
thionyl chloride (99%, sigma) copper(II) sulfate (99%, aldrich), were used as received. The
commercially available solvents were used without purification. H-NMR and 13C-NMR
spectral data were obtained on Bruker AV 300 spectrometer. FT-IR spectra were acquired on
a Perkin-Elmer BX FT-IR system spectrometer by dispersing samples in KBr pellets. UV-Vis
absorption spectra were recorded on a Cary 2300 spectrophotometer. DSC was performed on
1
-1
a Setaram instrumentation-regulation DSC 131 system with a heating rate of 10 °C min .
Photoluminesccence (PL) spectra were obtained on a Jobin-Yvon spectrometer HR460
coupled to a nitrogen cooled Si Charged-Coupled Device (CCD) detector. Samples were
excited with a 450 W Xenon lamp at 370 nm. For solid state measurements, the films were
-2
-1
spin-coating onto quartz substrate from 50 µL of DMF solution (2.10 M) and using tr.min
speed. The film thicknesses were measured by a Dektak profilmometer and were about 70
nm. Cyclic Voltametry (CV) was performed on a EG&G model 273 potentiostat/galvanostat
(Princeton Applied Research) in a three- electrode cell and using material films that were
drop-cast onto an indium tin oxide (ITO) a working electrode. The measurement were carried
-1
out at a scanning rate of 50 mVs against a satured calomel reference electrode (SCE) and
using 0.1 M tetrabutylammonium perchlorate ((n-Bu) ClO ) in acetonitrile as supporting
4
4
electrolyte. The electrochemical cell was externally calibrated by a ferrocene standard. The
measurements were performed at 25°C and the cell was deoxygenated with argon before each
reductive scan.
6
/32

2
.2 Synthesis of 4-nitrophtalimide (1)
The mixture of nitric acid (0.27 mol) and sulfuric acid (1.62 mol) was stirred in an ice bath
maintained for 30 min to room temperature [1].The phtalimide (1) was added dropwise to
acidic solution and heated at 35°C while stirring until a colorless solution was achieved. After
stirring for 4 h, the white solid was precipitated from ice water, filtered and washed with
1
water. The resultant Crude was dried under ambient conditions. 83% yield; H-NMR (300
MHz, DMSO-d
6
; δ: ppm): 8.02 (d, J = 5.7 Hz, 1H, H-Ar); 8.35 (s, 1H, H-Ar); 8.55 (d, J = 6.9
, δ): 118.17; 124.93;
Hz, 1H, H-Ar); 11.75 (s, 1H, N-H). 13C-NMR (75 MHz, DMSO-d
6
1
29.87; 134.43; 137.66; 151.71; 167.61; 167.92.
2
.3 Synthesis of 4-nitrophtalamide (2)
Compound 1 was stirred in 32 % ammonia solution (70 mL) for 24 h. The resulting deep
yellow product was filtered and washed with cold water until disappearance of excess of
1
ammonia [1]. The title compound was dried at 110 °C. 90% yield. ; H-NMR (300 MHz,
DMSO- d
6
; δ: ppm): 7.63 (s, 2H); 7.71 (d, J = 8.1, 1H); 8.02 (s, 1H); 8.08 (s, 1H); 8.29 (dd, J
1
3
J = 2.4 Hz, J = 8.7 Hz, 1H); 8.32 (d, J = 2.1 Hz, 1H). C-NMR (75 MHz, DMSO-d
6
, δ):
1
22.34, 124.38; 129.12; 137.19; 142.65; 147.03; 167.67; 168.67.
2
.4 Synthesis of 4-nitrophthalonitrile (3)
The thionyl chloride (286 mol) was slowly added to 50 ml of N,N-dimethylformamide at a
temperature lower than 5 °C, was stirred in an argon atmosphere. 15 g of 4-nitrophthalamide
was added and the reaction was maintained for 18 h. The crude product was precipitated from
1
a mixture of water–ice [1]. Yield 89%; H-NMR (300 MHz, DMSO- d
6
; δ: ppm): 8.44 (d, J =
8
.7, 1H, H-Ar); 8.68 (dd, J = 2.1 Hz, J = 8.4 Hz, 1H, H-Ar); 9.04 (d, J = 2.1, 1H, H-Ar). 13C-
NMR (75 MHz, DMSO-d , δ): 114.55; 114.86; 116.60; 120.22; 128.53; 128.81; 135.27;
6
1
49.70. FTIR: 3090 (C–H aromatic); 2245 (CN); 1534 (asymmetric N-O band); 1351
(symmetric N-O band); 852 (C–N).
2
.5 Synthesis of 9-anthrylmethyl acetate (4)
Sodium acetate (1.98 mmol) and 9-(chloromethyl)anthracene (1.32 mmol) was stirred in
ethanol (20mL) at 50°C for 6h. The mixture was precipitated in water; the obtained product
1
was an orange powder. Yield 95%; H-NMR (300 MHz, DMSO- d
6
; δ: ppm) 2.00 (s, 3H,
3
CH3-C); 6.11 (s, 2H, CH2-O); 7.58 (m; 4H; H-Ar); 8.10 (d, 2H, J = 12.0 Hz, H-Ar); 8.36 (d,
7
/32

3
13
2
1
H J = 9.3 Hz, Ar-H); 8.7 (s, 1H, H-Ar). C-NMR (75 MHz, DMSO-d
6
, δ): 20; 60; 125.26;
25.92; 126.44; 126.76; 128.81; 128.92; 130.11; 130.86; 170.46. FTIR (cm-1): 3032 (w,
aromatic C-H stretching); 1745 (s, esters stretching); 1442(s, C=O stretching); 1379 (s, C=C
stretching); 707 (s, aromatic C-H out-of-plane bending).
2
.6 Synthesis of 9-anthrylmethanol (5)
9
-anthrylmethyl acetate (1.79 mmol) was dissolved in anhydrous DMF (20mL), sodium
hydroxide (2.69 mmol) was added. After stirring at 50°C for 8h, the crude reaction was
1
precipitated in water; the obtained product was an yellow powder. Yield 90%; H-NMR (300
MHz, DMSO-d
6
; δ: ppm): 5.31 (s, 1H, OH); 5.60 (s, 2H, CH
2
-O); 7.62 (m, 4H, H-Ar); 8.13
d, 2H, H-Ar); 8.36 (d, 2H, H-Ar); 8.70 (s, 1H, H-Ar). C-NMR (75 MHz, DMSO- d , δ):
5.30; 124.79; 125.02; 125.76; 127.02; 128.67; 129.76; 131.05; 132.90. FTIR (cm-1): 3442
-OH, stretching); 3003 (w, aromatic C-H stretching); 1490 (s, C=C stretching); 738 (s,
aromatic C-H out-of-plane bending).
1
3
(
6
5
(
CH
2
2
.7 Synthesis of anthracene-based phtalonitrile (6)
4
-Nitrophtalonitrile (3) and 9-anthrylmethanol (5) (1.442 mmol) was dissolved in DMSO (20
mL) under nitrogen, then anhydrous K
2
CO (7.78 mmol) was added over 2h. The mixture was
3
stirred for 24h at room temperature. Finally water (100 mL) was added, and the aqueous
1
phase was extracted with chloroform. H-NMR (300 MHz, DMSO- d
6
; δ: ppm): 6.30 (s, 2H,
CH2-O); 7.51 (m, 6H, Ar-H); 8.12 (m, 3H, Ar-H); 8.61 (d, 2H, J = 9.0, Ar-H); 8.80 (s, 1H,
1
3
Ar-H). C-NMR (75 MHz, DMSO-d
6
, δ): 63.55; 106.14; 115.30; 116.23; 120.54; 120.81;
23.99; 125.32; 125.67; 126.91; 128.98; 129.22; 130.63; 130.89; 135.69; 162.12. FTIR (cm-
): 3050 (w, aromatic C-H stretching); 2218 (C-N, stretching); 1490 (s, C=C stretching); 738
1
1
(s, aromatic C-H out-of-plane bending).
2
.8 Synthesis of 4-(Proyn-3-yloxy) phthalonitrile (8)
4
-nitrophtalonitrile (3) (2.89 mmol) was dissolved in anhydrous DMF (20mL) under nitrogen.
The propargyl alcohol (PrAl) (7) (8.67 mmol) was added to the mixture. Stirred for 10 min
anhydrous K CO (28.9 mmol) was added in portions over 2h. The reaction mixture was
2
3
heated at 50° C and stirred for 24 h under nitrogen. Then water (100mL) was added, and the
1
aqueous phase was extracted with chloroform [2]. Yield 90%: H-NMR (300 MHz, CDCl
3
, δ:
ppm): 2.62 (s, 1H, C≡CH); 4.80 (d, J = 2.4 Hz, 2H, -CH -O-); 7.26 (d, J = 6 Hz, 1H); 7.33 (d,
2
8
/32

1
3
1
1
H); 7.73 (d, J = 9.0 Hz, 1H). C-NMR (75 MHz, , CDCl
3
, δ): 56.62; 76.19; 77.76; 108.23;
-1
15.50; 115.77; 117.44; 120.17; 121.107; 135.32; 160.46. FTIR (cm ): 3267 (s, C≡C,
stretching); 3111 (w, aromatic C-H stretching); 2227 (C≡N, stretching); 1317 (C-O,
asymmetric stretching); 1473 (s, C=C stretching); 816 (s, aromatic C-H out-of-plane
bending).
2
.9 Synthesis of 9-(azidomethyl)anthracene (9)
Sodium azide (3.96ꢀmmol) was added to a solution of 9-chlormethylanthracene (1.32ꢀmmol)
in DMF, and the resulting mixture was stirred for 6ꢀh at room temperature. The product
1
obtained after purification was a yellow powder [3]. Yield 95%; H-NMR (300 MHz, DMSO-
1
3
d
6
; δ: ppm) 5.50 (s, 2H, CH-N); 7.42-8.65 (m, 8H, Ar-H); 8.81 (s, 1H, Ar-H). C-NMR (75
MHz, DMSO-d , δ): 66.79; 124.85; 125.39; 126.34; 126.76; 128.55; 129.00; 130.23; 130.90.
6
-1
FTIR (cm ): 3030 (w, aromatic C-H stretching); 2109-2018 (R-N=N=N stretching); 1473 (s,
C=C stretching); 861 (s, aromatic C-H out-of-plane bending).
2
.10 Synthesis of anthracene-based phtalonitrile triazole (10)
Sodium ascorbate (0.658 mmol) and aqueous copper sulfate pentahydrate (0.329 mmol) were
added to 4-(Proyn-3-yloxy) phthalonitrile and corresponding azide (9) (0.823 mmol) in
THF/H O (1:1). The mixture was stirred for 24h at 60° C. Then water (100mL) was added,
2
and the aqueous phase was extracted with chloroform. The obtained product was a yellow
1
powder [4]. Yield 90%; H-NMR (300 MHz, DMSO-d
6
; δ: ppm): 5.22 (s, 2H, CH-O); 6.68
3
4
(
1s, 2H, CH-N); 7.45 (dd, J = 3.0, J = 9.0 ,1H, Ar-H); 7.63 (m, 5H, H-Ar); 7.79 (d, 1H, H-
3
3
Ar); 8.01 (d, J = 9.0, 1H, H-Ar); 8.11 (s, 1H, Ar-H); 8.17 (d, J = 9.0, 2H; Ar-H); 8.60 (d, J =
1
3
9
1
1
.0, 2H, Ar-H); 8.75 (s, 1H, Ar-H). C-NMR (75 MHz, DMSO-d
6
, δ): 55.12; 61.86; 106.14;
15.63; 116.10; 120.30; 120.40; 123.90; 124.88; 125.37; 125.56; 127.14; 129.11; 130.26;
-1
31.00; 135.66; 141.19; 161.20. FTIR (cm ): 3018(w, aromatic C-H stretching); 2202 (C≡N,
stretching); 1610-1590 (s, C=C stretching); (1532 aromatic N=N stretching); 1312 (ms, C-N,
stretching); 1263 (C-O, asymmetric stretching); 752 (s, aromatic C-H out-of-plane bending).
2
.11 General procedure for Phtalocyanine synthesis
AnPc and AnPc-Tr was prepared using compound (6 and 12) (0.60 mmol), urea (0.55mg,
mmol), zinc acetate (0.11 mg, mmol), and ammonium molybdate (catalytic quantities), heated
9
/32

in nitrobenzene at180°C for 8h. After cooling, the reaction mixture was treated with water.
The green dark product that precipitated was filtred off, successively washed with water and
hot methanol.
Zinc anthracene-based phthalocyanine AnPc (11)
1
Yield 68%; λmax (nm): 332; 700 (DMF): A and Q bands specifics of Pc material [18], H-
-1
NMR (300 MHz, DMSO-d
6
; δ: ppm): 5.45 (s, 8H, CH2-O); 7.1–9.02 (m, 52H). FTIR (cm ):
077 (w, aromatic C-H stretching); 1038-1700 (s, Ar-O-C asymmetric stretching); 1682 and
821 (ms, C-N, stretching); 1490 (s, C=C stretching); 759 (s, aromatic C-H out-of-plane
3
2
bending); 424 (Zn-N, stretching).
Zinc triazole-anthracene-based phthalocyanine AnPc-Tr (12)
1
Yield 60%.λmax (nm): 330; 686 (DMF): A and Q bands specifics of Pc material, H-NMR
300 MHz, DMSO-d ; δ: ppm): 5.22 (s, 8H, CH2-O); 6.59 (s, 8H, CH-N); 7.1–9.23 (m, 52H).
(
6
-1
FTIR (cm ): 3198(w, aromatic C-H stretching); 1610-1590 (s, C=C stretching); 1360-1461 (s,
Ar-O-C asymmetric stretching); 1708 and 2812 (ms, C-N, stretching); 1488 (aromatic N=N
stretching); 1240 (C-O, asymmetric stretching); 780 (s, aromatic C-H out-of-plane bending);
3
94 (Zn-N, stretching).
2
.12 Fabrication and characterization of diode
The single-layer device was fabricated as a sandwich structure between aluminium (Al)
-1
cathode and indium tin oxide (ITO) anode. Pc solution (10 mg mL in DMSO) was spin-cast
2000 rpm) onto ITO glass to obtain a film with a thickness of about 60 nm after annealing at
(
4
0 °C for 1 h. The thin aluminium layer (150 nm) was deposited as the cathode by thermal
6
evaporation under 3 x 10- Torr. The current–voltage (I–V) characteristic of the device was
recorded with a digital oscilloscope Tektronix 5034.
3
3
. Result and discussion
.1 Synthesis and characterization
The phtalocyanine containing anthracene (AnPc) and triazole anthracene (AnPc-Tr) were
prepared according to synthetic route shown scheme 3, respectively. The 4-nitrophthalonitrile
1
0/32

(3) was synthesized in three steps presented in scheme 1. This compound was prepared by
nitration of phthalimide [1]. Then, the obtained product (1) was reacted with ammonia and
followed dehydration with the thionyl chloride. The phtalocyanine derivatives were
synthesized by cyclo-tetramerization of anthracene-based dinitrile for AnPc and dinitrile
containing anthracene-triazol for AnPc-Tr (scheme 3). The synthesis of dinitriles derivatives
(6 and 10) was described in scheme 2. The obtained phtalocyanine materials derivatives
(AnPc and AnPc-Tr) were found to have good solubility in DMSO and DMF. The Molecular
structure of AnPc and AnPc-Tr was confirmed by NMR, FTIR and UV-visible absorption
1
spectroscopic analysis. H-NMR spectra showed a broad peak between 7.11 to 9.03 ppm
assigned to phenylene protons and the CH
2
O groups appear at 5.22 ppm. We also note the
-triazol groups in the case of AnPc-Tr.
presence of a signal at 6.59 ppm corresponding CH
2
The FTIR spectra showed the aromatic and aliphatic C–H stretchings between 3015 and 2815
cm-1. The asymmetric and symmetric stretchings of the C–O–Ar ether group give rise to two
bands at 1250 and 1038 cm-1. The Zn-N stretching appeared at 424 and 394 cm-1 for AnPc
and AnPc-Tr respectively. The AnPc-Tr showed an N=N stretching in 1488cm-1 for triazole
groups. The structure of AnPc and AnPc-Tr were also confirmed by UV-visible absorption.
The typical features of phtalocyanines and a broad absorption band at around 686-700 nm
characteristic of Q-absorption band were observed. The thermal behavior of AnPc and AnPc-
Tr were investigated by differential scanning calorimetry (DSC) under ambient atmospheric
conditions (Figure 1). The DSC thermograms show a good thermal stability for both
materials; upper to 250 ° C. No melting peak was observed, which indicates a totally
amorphous morphology for the phtalocyanine derivatives (AnPc and AnPc-Tr).
3
.2 Optical properties in dilute solution
The UV-visible absorption and fluorescence spectra of (AnPc) and (AnPc-Tr) were recorded
at room temperature, in DMF diluted solutions (5.10-5 for absorption and 2.10-7 for
fluorescence) and in thin films; the Table 1 summarizes the obtained optical data.
In dilute solution, the materials (AnPc) and (AnPc-Tr) exhibit similar feature absorption
spectra. The spectra show three maxima (353, 372 and 396 nm) and one shoulder (474 nm)
characteristic of π-π* electronic transition of the anthracene moiety [7]. A and Q bands
specifics of Pc were observed for both phtalocyanine derivatives (AnPc, AnPc-Tr) at (391,
7
00 nm) and (389, 683 nm) respectively [10]. However, the anthracene based phtalocyanine
1/32
1

spectrum was the narrowest, more structured and slightly shifted to the higher energies (18
nm) in comparison with here analogue containing triazol group (AnPc-Tr). This behavior can
be attributed to the rigidity of triazol group, which limited the conformational change,
consequently reducing the available vibrational and rotational freedom [19]. The
characteristics bands of phtalocyanine (A and Q bands) in AnPc, AnPc-Tr absorption spectra
were shifted in higher wavelength, in comparison to sample phtalocyanine [20]. In return, the
presence of triazole group of the anthracene-based phtalocyanine do not appear to
considerably alter its emission but AnPc-Tr PL spectrum was relatively structured with two
maxima at 431 nm and 452 nm and one shoulder at 483 nm in blue region and one maximum
at 836 nm in red region (Fig. 4). However, AnPc-Tr shows a PL quantum yield of 0.03,
which is lower than that of AnPc ( = 0.67). Such behavior is probably due to the important
flexibility created with the presence of methylene group, which increases the available vibro-
rotational freedom degrees and therefore improve the PL loss via non-radiative processes
[
21].
3
.3 Thin-film optical properties
The optical properties of phatlocyanine derivatives thin films were investigated by UV-visible
absorption and photoluminescence spectroscopies (fig. 5); the Table 1 summarizes the
obtained results. The AnPc and AnPc-Tr layers show qualitatively the same absorption
spectra of the solutions (Fig. 3). Nevertheless, broader and non-structured spectra were
observed in solid state. This behavior can be attributed to the - interaction of conjugated
systems and aggregate formation in solid state [20]. However, AnPc-Tr absorption spectrum
is narrow in comparison with AnPc; explained by steric hindrance of triazole group, which
decrease the planarity of macromolecular structure and prevent --interactions of conjugated
systems. The optical bandgaps calculated from the onset films absorptions were 1.47 eV and
1
.50 eV for AnPc, AnPc-Tr; respectively. These values can be classified the phtalocyanine
derivatives (AnPc, AnPc-Tr) among the organic semiconductors materials. In fluorescence, a
broader AnPc and AnPc-Tr spectra were observed, in comparison with its analogue in dilute
solution (Fig. 2). This difference can be attributed to - interaction of conjugated moieties
and excimer formation, in solid state [23].
1
2/32

3
.4 Electrochemical and electrical characterization
Cyclic voltammetry (CV) was employed to investigate the redox behaviour of the Pc
materials and to estimate their HOMO (Highest Occupied Molecular Orbital) and LUMO
(
Lowest Unoccupied Molecular Orbital) energy levels. Knowledge of these energy levels is of
crucial importance to the selection of cathode and anode materials for OLED devices [24].
The use of CV analysis is reliable, as the electrochemical processes are similar to those
involved in charge injection and transport processes in OLEDs [22]. The organic films were
drop-coated onto an ITO glass substrate and scanned both positively and negatively in (n-
Bu)
4
NClO /acetonitrile. The cyclic voltammograms obtained are shown in (Fig. 1). According
4
to an empirical method [25] and by assuming that the energy level of the
ferrocene/ferrocenium couple is 4.8 V below the vacuum level, the HOMO energy level
(EHOMO), LUMO energy level (ELUMO) and the electrochemical gap (Eg-el) can be calculated as
follows:
EHOMO (IP, ionization potential) = - (Vonset-ox - VFOC + 4.8) eV
ELUMO (EA, electron affinity) = - (Vonset-red - VFOC + 4.8) eV
Eg-el= (ELUMO- EHOMO) eV
Where VFOC is the ferrocene half-wave potential (0.95 V), Vonset-ox the phtalocyanine
derivatives oxidation onset and Vonset-red the phtalocyanine derivatives reduction onset, all
measured versus Ag/AgCl (the reference electrode used in this work). All processes are ring
based since the central Zn metal is electroinactive [26]. The HOMO and LUMO energy levels
were estimated to be 4.90-4.87 eV and 2.63-2.93 eV, respectively (Table. 1). The analysis of
the energy levels of the two phtalocyanine derivatives shows comparable ionization potential.
However, the electron affinity increases with the introduction of triazol group in molecular
structure of AnPc-Tr. A single-layer device with the ITO/phtalocyanine/Al configuration
was fabricated to investigate the current-voltage (I-V) characteristic of the phtalocyanine
derivatives (AnPc and AnPc-Tr). As shown in Fig. 7, the I-V curve of indicate typical diode
behavior with relatively low turn-on voltages of 3.4 V and 2.9 V for AnPc and AnPc-Tr;
respectively.
4
. Conclusion
New soluble phtalocyanine derivatives (AnPc and AnPc-Tr) were synthesized and
characterized. These semiconducting materials have a good solubility in organic polar
1
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solvents and showed a good thermal stability going up to 250 °C. The phatalocyanine
derivatives were investigated by UV-vis absorption and photoluminescence spectroscopies. In
dilute solution, the absorption spectra for AnPc and AnPc-Tr exhibit the A and Q bands
characteristic of Pc. The introducing of the triazole moieties in the molecular structure of
phtalocyanine improved PL quantum yield in dilute solution and a value of 0.67 was obtained
for AnPc. Going from solution to thin film, - interaction of conjugated systems was
observed in absorption and fluorescence. However, the introducing of triazole moieties
decreased the planarity of macromolecular structure and prevented --interactions in AnPc-
Tr. The optical bandgaps determined from the onset films absorptions were 1.47 eV and 1.5
eV for AnPc, AnPc-Tr; respectively. The HOMO and LUMO levels were estimated using
cyclic voltammetry analysis and the effect of triazole group was observed in the electronic
affinity. The I-V characteristics of the devices with an ITO/phtalocyanine/Al configuration
demonstrate typical diode behavior with relatively low turn-on voltages of 3.4 V for AnPc
and 2.9 V for AnPc-Tr.
ACKNOWLEDGMENTS
This work was financially supported by the “Ministry of Higher Education and Scientific
Research-Tunisia”. Special thanks go to Mawaheb Kahouech and John Lomas for their help
in improving the quality of the English of this article.
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REFERENCES
1] N. B. McKeown, Phthalocyanine Materials: Synthesis, Structure and Function, An
[
introduction to the phtalocyanine, Cambridge University Press, Chemistry of solid state
materials. (1998) 21-197.
[
2] A. K. Ghosh, D. L. Morel, T. Feng, R. F. Shaw, C. A. Rowe, Photovoltaic and
rectification properties of Al/Mg phthalocyanine∕Ag Schottkybarrier cells, J. Appl. Phys.
1974) 45 230-236
3] J. F. van der Pol, E. Neeleman, J. W. Zwikker, R. J. M. Nolte, W. Drenth, J. Aerts, R.
(
[
Visser, S. J. Picken, The rare earth substitution effect on the electrochemistry of
diphthalocyanine films in contact with an acidic aqueous medium, Journal of
Electroanalytical Chemistry and Interfacial Electrochemistry, Liq. Cryst. (1989) 5 577-592.
[
4] M. Riou, C. Clarisse, The rare earth substitution effect on the electrochemistry of
diphthalocyanine films in contact with an acidic aqueous medium, J. electroanal. chem.
interfacial electrochem. (1988) 249 181-190.
[
5] R. A. Collins, K. A. Mohammed, Gas sensitivity of some metal phthalocyanines, Journal
of Physics D: Applied Physics, J. Phys. D: Appl. Phys. (1988) 21 154-161.
6] M. C. DeRosa, J .Robert. Crutchley, Photosensitized Singlet Oxygen and its Applications,
Coord. Chem. Rev. (2002), 233-234, 351-371.
7] M. Ochsner, Photophysical and photobiological processes in the photodynamic therapy of
tumours, J. Photochem. Photobiol. (1997) 39 1-18.
8] W. M. Sharman, C. M.Allen, J. E. van Lier, Photodynamic therapeutics: basic principles
and clinical applications, Drug Discov. Today (1999) 4 507-517.
9] I. Özcesmeci, A. Gelir, A. Gül, Synthesis and photophysical properties phthalocyanine-
pyrene dyads, Dyes Pigm. (2012) 92 954-960.
10] C. A. Barker, K. S. Findlay, S. Bettington, A. S. Batsanov, I. F. Perepichka, M. R. Bryce,
[
[
[
[
[
A. Beedy, Synthesis of new axially-disubstituted silicon-phthalocyanine derivatives: optical
and structural characterization, Tetrahedron. (2006) 62 9433-9439.
[
[
11] A. Hagfeldt, M. Grätze, Molecular photovoltaics, Acc. Chem. Res. (2000) 33 269-77.
12] M. O. Liu, C. Tai, A. Teh Hu, The fluorescent and photoelectric conversion properties of
phthalocyanineeperylene tetracarboxylic complexes, J. Photochem. Photobiol. A. (2004)
65 193-200.
1
1
5/32

[
13] D. Kaya, O. Pekcan, Y. Yılmaz, Direct test of the critical exponents at the sol-gel
transition, Phys. Rev. E. (2004) 69 1-8.
14] M. S. Frahn, R. D. Abellon, W. F. Jager, L. H. Luthjens, J. M. Warman, Synthesis and
[
characterization of a new fluorogenic probe molecule N-(1-pyrene)methacrylamide for
monitoring radiation-induced polymerization, Nucl. Instr. And Meth. in Phys. Res. B. (2001)
1
85 241-247.
15] M. Pope, H. S. Kallmann, P. Magnante, Electroluminescence in Organic Crystals, J.
Chem. Phys. (1963) 38 2041-2043.
16] Y. Zhan, K. Cao, P. Xue, R. Lu, Synthesis of monodisperse oligocarbazoles-
functionalized anthracenes with intense blue-emitting , Tetrahedron Lett. (2013) 54 594-599.
[
[
[
17] A. Mahajan , R. K. Bedi, P. Singh, V. Kumar, Synthesis and characterization of 1-
phenyl-3-(4-phenyl-[1,2,3]triazol-1-yl)-4-styryl-azetidin-2-one films for light-emitting
applications , Thin Solid Films, (2010) 519 1501–1505.
[
18] K. Hriz, N. Jaballah, J.L. Fave, M. Majdoub, Synthesis and characterization of new
anthracene-based semi-conducting materials, J. Mater. Sci. (2012) 47 8067–8075.
19] D. P. Craig, S. H. Walmsley, Excitons in Molecular Crystals; Benjamin: New York,
968.
20] K. Bayo, J. C. Mossoyan, G.V. Ouedraogo, Preparation and analysis by UV-Vis of zinc
phthalocyanine complexes, Spectroc. Acta A. (2004) 60 653–657
21] N. Jaballah, K. Hriz, M. Majdoub, M. Jouini, J. L. Fave, New Blue- Photoluminescent
Semi-Conducting Polymer Derived from Fluorinated Bisphenol A, High. Perform. Polym.
2010) 22 483-497.
22] M. Cheng, Y. Xiao, W. L. Yu, Z. K. Chen, Y. H. Lai, W. Huang, Synthesis and
[
1
[
[
(
[
characterization of a cyano-substituted electroluminescent polymer with well-defined
conjugation length , Thin Solid Films. (2000) 363 110-113.
[
23] Y. F. Huang, Y. J. Shiu, J. H. Hsu, S. H. Lin, A. C. Su, K. Y. Peng, S. A. Chen, W. S.
Fann, Aggregate versus Excimer Emissions from Poly(2,5-di-n-octyloxy-1,4-
henylenevinylene) , J. Phys. Chem. C. (2007) 111 5533-5540.
[
24] B. Fan, Q. Sun, N. Song, H. Wang, H. Fan, Li. Yongfang, Electroluminescent properties
of a partially-conjugated hyperbranched poly(p-phenylene vinylene), Polym. Adv. Technol.
2006) 17 145-149.
(
1
6/32

[
25] J. L. Bredas, R. Silbey, D. S. Bordeaux, R. R. Chance, Chain-Length Dependence of
Electronic and Electrochemical Properties of Conjugated Systems:Polyacetylene,
Polyphenylene, Polythiophene, and Polypyrrole, J. Am. Chem. Soc. (1983) 105 6555-6559.
26] Y. Arslanoglua, A. Koca, E. Hamuryudan, Synthesis of novel unsymmetrical
phthalocyanines substituted with crown ether and nitro groups, Polyhedron. (2007) 26 891-
96.
[
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Figure captions
Fig. 1 DSC thermograms of AnPc and AnPc-Tr.
-5
-1
Fig. 2 UV-vis absorption spectra of AnPc and AnPc-Tr in dilute solution (510 mol.L )
Fig. 3 UV-vis absorption spectra of AnPc and AnPc-Tr in thin film (60 nm)
-7
-1
Fig. 4 PL spectra of AnPc and AnPc-Tr in dilute solution (210 mol.L )
Fig. 5 PL spectra of AnPc and AnPc-Tr in thin film (60 nm)
Fig. 6 Cyclic voltammograms for AnPc-Tr and AnPc films coated onto ITO electrodes in
0
.1M (n-Bu)
4
NClO /acetonitrile (scan rate = 50 mV/s).
4
Fig. 7 Current–voltage curve for [ITO/phtalocyanine/Al] devices
Scheme 1. Synthetic route to 4-nitrophtalonitrile
Scheme 2. Synthetic routes to anthracene-based phtalonitrile (6) and (10).
Scheme 2. Synthetic route to AnPc and AnPc-Tr
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Fig.1
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Fig.2
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Fig.3
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Fig.4
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Fig.5
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Fig.6
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Fig.7
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Fig.8
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Fig.9
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Scheme 1
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Scheme 2
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