Efficient green procedures for the preparation of novel tetraalkynyl-substituted phthalocyanines

Article abstract of DOI:10.1016/j.poly.2010.02.034

This work provides a successful, easy and efficient process for the preparation of metal-free 2(3),9(10),16(17),23(24)-octamethoxyphthalocyanine, [(OMe)₈PcH₂] (2), and its metal complexes [(OMe)₈PcM] (3-11) (M = Zn, Cu, Ni, Mg, Co, Fe, Ru, TiCl and RhCl) by using green energy techniques such as exposure to UV-irradiation as well as microwave irradiation. Two different routes have been used, which involve modifications to that reported in the literature. The results suggest that these techniques drastically reduce the reaction time of metallophthalocyanine [(OMe)₈PcM] (3-11) formation from 5-96 h to 5-11 min. The prepared octamethoxyphthalocyanines [(OMe)₈PcM] (2-4) (M = H₂, Zn, Cu) are used as key materials to synthesize the corresponding novel tetraalkynyl-substituted phthalocyanines 15-17.

Full text of DOI:10.1016/j.poly.2010.02.034

Polyhedron 29 (2010) 1776–1783
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Efficient green procedures for the preparation of novel
tetraalkynyl-substituted phthalocyanines
Tamer Ezzat Youssef *
Applied Organic Chemistry Department, National Research Center, Dokki, Cairo 12311, Egypt
a r t i c l e i n f o
a b s t r a c t
Article history:
This work provides
a
successful, easy and efficient process for the preparation of metal-free
PcH (2), and its metal complexes
8
PcM] (3–11) (M = Zn, Cu, Ni, Mg, Co, Fe, Ru, TiCl and RhCl) by using green energy techniques such
Received 28 December 2009
Accepted 15 February 2010
Available online 3 March 2010
2(3),9(10),16(17),23(24)-octamethoxyphthalocyanine, [(OMe)
8
2
]
[(OMe)
as exposure to UV-irradiation as well as microwave irradiation. Two different routes have been used,
which involve modifications to that reported in the literature. The results suggest that these techniques
Keywords:
drastically reduce the reaction time of metallophthalocyanine [(OMe)
6 h to 5–11 min. The prepared octamethoxyphthalocyanines [(OMe)
used as key materials to synthesize the corresponding novel tetraalkynyl-substituted phthalocyanines
5–17.
8
PcM] (3–11) formation from 5–
Alkynyl phthalocyanines
Metal-free phthalocyanines
Metallophthalocyanines
UV-irradiation
9
8
PcM] (2–4) (M = H , Zn, Cu) are
2
1
Ó 2010 Elsevier Ltd. All rights reserved.
Microwave irradiation
1
. Introduction
direct, rapid, internal and controllable method, leading to shorter
reaction times, higher yields and easier work-up than classical
thermal processing [33–35]. Moreover, by reducing the reaction
time, the formation of side products is avoided and the reproduc-
ibility of the reaction is improved [36].
The high-speed synthesis of metal-free phthalocyanine and
metallophthalocyanines by using microwave irradiation had been
reported previously by Shaabani [37–42], Villemin [43] and Davis
[44] by using domestic oven and microwave assisted synthesis.
In another study, the synthesis of metal-free and metallophthalo-
cyanines bearing tetraaza macrocyclic moieties under microwave
irradiation was investigated [45,46].
Nowadays, phthalocyanines form an important group of aro-
matic macrocycles, dependant on a delocalized 18- electron sys-
p
tem that belongs to the most modern functional materials in
scientific research [1–3]. They play an important role in many ad-
vanced applications and modern technologies, mostly by virtue of
their characteristic optical absorption and high chemical stability.
In addition, they can find commercial applications as photoconduc-
tors in xerographic machines [4–6], electrochromic displays [7],
photovoltaic materials in solar cells [8–10], systems for fabrication
of light emitting diodes (LED) [11,12], optical limiters [13,14], dyes
for recording layers in recordable digital versatile discs (DVDs)
The author has prepared earlier novel symmetrical and asym-
metrical metal-free and metallophthalocyanines carrying long
chain alkoxy groups [47–49] or axial ligands [50] for potential
use in applications. They were prepared by high temperature
[
15], liquid crystalline materials [16], organic conductors [17,19],
sensitizers for photodynamic cancer therapy (PDT) [18,20–22]
and diverse catalytic systems [23,24]. Recently, metal-free phthal-
ocyanines have been obtained by high temperature cyclotetramer-
ization processes starting from diverse precursors, such as
phthalonitrile, o-cyanobenzamide, phthalimide and 1,3-diimino-
isoindoline, generally in high-boiling non-aqueous solvents at ele-
vated temperatures [25–28], or electrochemically from
phthalonitriles [29–31], or at low temperature by UV-irradiation
of the reaction system [32]. The use of microwave energy is one
of the more efficient methods for selective heating in many pro-
cesses. As well as being more environmentally friendly, requiring
less energy than conventional processes, it is also a selective,
cyclotetramerization
phthalonitriles.
processes
from
the
corresponding
In the present work, we describe for the first time the synthesis
and characterization of 2,3,9,10,16,17,23,24-octamethoxyphthalo-
cyanine [(OMe)
PcH ] (2) and its metallo-derivatives [(OMe) PcM]
8 2 8
(3–11), (M = Zn, Cu, Ni, Mg, Co, Fe, Ru, TiCl and RhCl) by applying
two different routes of preparation which are being developed in
our group: (1) UV-irradiation of the reaction system for the synthe-
sis of metal-free phthalocyanine 2 from phthalonitrile 1 [51] in
alcohols. (2) Microwave assisted irradiation of the reaction system
for the synthesis of metal-free and metallophthalocyanines in the
presence of solvent, controlled temperature and smart conditions,
either from phthalonitrile 1 (route A) or from the metal-free ana-
logue 2 as a precursor (route B).
*
Present address: Institut für Organische Chemie, Universität Hannover, Schne-
iderberg 1B, D-30167, Hannover, Germany. Tel.: +49 15157291577.
E-mail address: tamezzat@yahoo.com
0
277-5387/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2010.02.034

T.E. Youssef / Polyhedron 29 (2010) 1776–1783
1777
When alkynyl groups are attached to the phthalocyanine skele-
ton, they realize excellent chemical–physical properties of the Pcs,
due to the coupling of the structural (i.e. rigidity and linearity) and
suspended solution that formed was centrifuged. The precipitated
solid was filtered off, washed with a methanol/water mixture (1/1,
v/v) and dried under vacuum. The crude product (2.10 g) was puri-
fied with a Soxhlet extractor by extracting for 1 day with dichloro-
methane to give compound 2 as a green powder, yield: 60%. Anal.
electronic (i.e. the presence of
p-electrons) features of the acety-
lene group. A variety of mono- [52,53] and octaalkynyl-substituted
phthalocyanines [54,55] have been reported during the last dec-
ade. Torres and co-workers [56,57] reported a series of tetraethy-
nyl-substituted phthalocyanines. Another series of peripherally
alkynylated phthalocynanines have been prepared by Faust [58].
We are trying to contribute to this area of research by providing
the prepared complexes 2–4 and using them as key materials to
synthesize the corresponding novel tetraalkynyl-substituted
phthalocyanines 15–17. The structures of the novel compounds
34 8 8
Calc. for C40H N O : C, 63.65; H, 4.54; N, 13.85. Found: C, 62.01;
1
6
H, 5.80; N, 13.90%. H NMR (DMSO-d ) d (ppm): À4.1 to À3.8 (br,
2H, NH), 3.94 (s, 24H, OMe), 7.25 (s, 8H, ArCH). IR (KBr)
(cm ): 3229–3222 (br), 2956, 2926, 2855, 1653, 1540 (s), 1466
m
À1
(s), 1434 (m), 1318 (m), 1228 (m), 1140 (s), 1126, 920 (s), 880
À5
(m), 750 (m). UV–vis (DMF),
k
max (nm) [(10
log
3
À1
À1
e
dm mol cm )]: 696(5.24), 661(5.17), 635(4.86), 602(4.78),
+
346(5.16). MS (FD): m/z 754.76 (M ).
1
5–17 were characterized by a combination of 1H NMR, IR, UV–
vis, elemental analysis and MS spectral data.
2.5.2. Microwave irradiation synthesis method
A standard Schlenk tube was charged with a mixture of 4,5-
2
. Experimental
dimethoxyphthalodinitrile 1 (3.5 g, 18.5 mmol), deoxygenated
N,N-dimethylaminoethanol (DMAE) (5 ml) and DBU (1 ml) under
a nitrogen atmosphere and degassed several times. The mixture
was well stirred, then irradiated in a microwave reactor at 350 W
for 8 min. After cooling to room temperature, a green solution
2.1. General
All manipulations were performed under nitrogen using stan-
dard Schlenk techniques unless otherwise specified.
2
was formed, which was then poured into MeOH/H O (3:1). The
suspended solution was centrifuged. The precipitated solid was fil-
tered off, washed with a methanol/water mixture (1/1, v/v) and
dried under vacuum. The crude product (2.34 g) was purified with
a Soxhlet extractor, by extracting for 1 day with dichloromethane
to give compound 2 as a green powder, yield: 68%.
2
.2. Materials
The precursor 4,5-dimethoxyphthalonitrile 1 was synthesized
as described in another report [51]. 3,4-Diflurophenylacetylene
Aldrich) was commercially available and used as purchased. All
(
other reagents, solvents and metal salts were of reagent-grade
quality, obtained from commercial suppliers and used as received.
2
2
.6. General procedures for the synthesis of the metallo-
,3,9,10,16,17,23,24-octamethoxyphthalocyanine complexes
[
(OMe)
8
PcM] (3–11)
2.3. Instruments
2
.6.1. (2,3,9,10,16,17,23,24-octamethoxyphthalocyaninato)zinc(II),
UV Reactor Laboratory System: mercury medium pressure
[(OMe) PcZn] (3) [58]
8
lamp, 150 W, combined immersion/cooling tube in quartz glass,
reaction vessel of around 250 ml with a rotor to circulate the solu-
tion, power supply.
Microwave oven utilized for heating: Discover Lab Mate single-
mode microwave cavity from CEM Corporation. The reactions were
conducted in a 25 ml Schlenk tube, with a maximum operating
temperature of 180 °C and a maximum operating pressure of 8 bar.
2.6.1.1. Method A. A standard Schlenk tube was charged with a
mixture of 4,5-dimethoxyphthalodinitrile 1 (3.5 g, 18.5 mmol),
anhydrous zinc acetate (0.14 g, 0.77 mmol), deoxygenated DMAE
(5 ml) and DBU (1 ml) under a nitrogen atmosphere, and degassed
several times. The mixture was well stirred, then irradiated in a
microwave reactor at 370 W for 10 min. After cooling to room tem-
perature, a green solution was formed which was then poured into
2
MeOH/H O (3:1). The suspended solution was centrifuged. The
2
.4. Physical measurements
precipitated solid was filtered off, washed with a methanol/water
mixture (1/1, v/v) and dried under vacuum. The crude product
(2.6 g) was purified with a Soxhlet extractor by extracting for 2–
3 days with acetone and dichloromethane to give compound 3 as
1H NMR spectra were measured on a Bruker ARX 250
(
250.133 MHz) NMR spectrometer. FT-IR spectra were recorded
on a Bruker IFS 48 spectrometer using KBr pellets. The UV–vis
spectra were taken in N,N-dimethylformamide (DMF) using a Per-
kin–Elmer Lambda 2 spectrometer. FD mass spectra measurements
were carried out with a Varian MAT 711 A spectrometer and re-
ported as mass/charge (m/z). Elementary analyses were performed
on a Carlo Erba Elemental Analyzer 1104, 1106.
32 8 8
a green powder, yield: 72%. Anal. Calc. for C40H N O Zn: C,
1
58.72; H, 3.94; N, 13.70. Found: C, 59.01; H, 3.80; N, 13.94%. H
6
NMR (DMSO-d ) d (ppm): 3.89 (s, 24H, OMe), 7.30 (s, 8H, ArCH).
À1
IR (KBr)
m
(cm ): 2959, 2865, 1657, 1548 (s), 1465 (s), 1444 (m),
1322 (m), 1221 (m), 1138 (s), 1125, 923 (s), 883 (m), 755 (m).
À5
3
À1
+
À1
UV–vis (DMF),
6
k
max (nm) [(10
log e dm mol cm )]:
88(5.22), 622(4.85), 360(5.16). MS (FD): m/z 818.12 (M ).
2.5. Procedures for the synthesis of metal-free 2,3,9,10,16,17,23,24-
octamethoxyphthalocyanine [(OMe) PcH ] (2)
8
2
2.6.1.2. Method B. A standard Schlenk tube was charged with a
mixture of metal-free 2,3,9,10,16,17,23,24-octamethoxyphthalocy-
anine 2 (1.5 g, 2 mmol), anhydrous zinc acetate (0.07 g, 0.3 mmol),
deoxygenated DMAE (3 ml) and DBU (1 ml) under a nitrogen atmo-
sphere and degassed several times. The mixture was well stirred,
then irradiated in a microwave oven at 300 W for 8 min. After cool-
ing to room temperature, a green suspension was formed, which
2
.5.1. UV-irradiation synthesis method
mixture of 4,5-dimethoxyphthalodinitrile
8.5 mmol) and diazabicyclo[5.4.0]undec-7-ene (DBU, 0.5 ml) in
A
1
(3.5 g,
1
deoxygenated 2-ethoxyethanol (50 ml) was placed in a quartz
tube. The mixture was well stirred, then irradiated for 3.5 h in a
photochemical reactor (mercury lamp of 150 W) at 70–75 °C under
dry nitrogen. A green coloured solution was formed, cooled to
2
was then poured into MeOH/H O (3:1). The suspended solution
was centrifuged. The precipitated solid was filtered off, washed
with a methanol/water mixture (1/1, v/v) and dried under vacuum.
The crude product (1.3 g) was purified with a Soxhlet extractor by
2
room temperature then poured into MeOH/H O (3:1). The

1
778
T.E. Youssef / Polyhedron 29 (2010) 1776–1783
extracting for 2–3 days with acetone and dichloromethane to yield
78%, 1.2 g) of compound 3 as a green powder.
2.6.8. (2,3,9,10,16,17,23,24-octamethoxyphthalocyaninato)titanium
chloride(III), [(OMe) PcTiCl] (10)
This product was obtained as a green solid from TiCl
P = 360 W, t = 10 min, method A]; yield: 40%. Anal. Calc. for
(
8
3
[
2
[
.6.2. (2,3,9,10,16,17,23,24-octamethoxyphthalocyaninato)copper(II),
(OMe) PcCu] (4) [58]
This product was obtained as a blue powder from CuCl
P = 350 W, t = 8 min, method A]; yield: 62%, or [P = 330 W,
Cu: C,
8.72; H, 3.94; N, 13.70. Found: C, 59.01; H, 3.80; N, 13.94%. UV–
C
4
7
1
9
e
40 32 8 8
H N O TiCl: C, 57.46; H, 3.96; N, 13.40. Found: C, 56.01; H,
8
1
6
.30; N, 12.94%. H NMR (DMSO-d ) d (ppm): 3.85 (s, 24H, OMe),
2
À1
.29 (s, 8H, ArCH). IR (KBr)
m
(cm ): 2949, 2921, 2850, 1651,
[
544 (s), 1462 (s), 1438 (m), 1313 (m), 1222 (m), 1139 (s), 1124,
t = 7 min, method B]; yield: 60%. Anal. Calc. for C40
5
vis (DMF), kmax (nm) [(10
H
32
N
8
O
8
À5
22 (s), 881 (m), 754 (m). UV–vis (DMF), kmax (nm) [(10 log
3
À1
À1
dm mol cm )]: 689(5.22), 622(4.83), 442(5.21), 420(5.19).
À5
3
À1
À1
log
e
dm mol cm )]: 674(5.20),
+
MS (FD): m/z 836.08 (M ).
+
6
06(4.76), 344(5.15). MS (FD): m/z 816.29 (M ).
2
.6.9. (2,3,9,10,16,17,23,24-octamethoxyphthalocyaninato)rhodium
chloride(III), [(OMe) PcRhCl] (11)
This product was obtained as
RhCl O [P = 360 W, t = 11 min, method A]; yield: 52%. Anal.
Á3H
Calc. for C40 RhCl: C, 54.92; H, 3.92; N, 12.57. Found: C,
8
2
[
.6.3. (2,3,9,10,16,17,23,24-octamethoxyphthalocyaninato)nickel(II),
(OMe) PcNi] (5) [58]
This product was obtained as a green powder from NiCl
P = 350 W, t = 8 min, method A]; yield: 83%, or [P = 300 W,
Ni: C,
a
blue-green solid from
8
3
2
2
32 8 8
H N O
[
1
6
5
6.01; H, 4.30; N, 12.94%. H NMR (DMSO-d ) d (ppm): 3.88 (s,
t = 5 min, method B]; yield: 80%. Anal. Calc. for C40
5
NMR (DMSO-d ) d (ppm): 3.77 (s, 24H, OMe), 7.33 (s, 8H, ArCH).
IR (KBr)
32 8 8
H N O
À1
1
24H, OMe), 7.34 (s, 8H, ArCH). IR (KBr) m (cm ): 2952, 2924,
9.21; H, 3.97; N, 13.81. Found: C, 60.71; H, 3.80; N, 14.94%.
H
6
2850, 1658, 1542 (s), 1468 (s), 1437 (m), 1318 (m), 1227 (m),
1142 (s), 1126, 920 (s), 880 (m), 750 (m). UV–vis (DMF), kmax
À1
m
(cm ): 2950, 2924, 2850, 1651, 1548 (s), 1462 (s),
À5
3
À1
À1
(
nm) [(10
log e dm mol cm )]: 658(5.13), 597(4.86),
1
7
6
438 (m), 1322 (m), 1227 (m), 1142 (s), 1125, 921 (s), 887 (m),
+
À5
3
À1
À1
366(5.14). MS (FD): m/z 891.10 (M ).
51 (m). UV–vis (DMF), kmax (nm) [(10 log
e dm mol cm )]:
97(5.19), 671(4.88), 370(5.23), 315(5.17). MS (FD): m/z 811.43
+
2.7. General procedure for the synthesis of 2,3,9,10,16,17,23,24
octahydroxyphthalocyanines [(OH) PcM] (12–14) [58], M = H , Zn, Cu
8 2
(
M ).
2
(
.6.4. (2,3,9,10,16,17,23,24-octamethoxyphthalocyaninato)magnesium
II), (OMe) PcMg] (6)
This product was obtained as a green powder from MgCl
P = 350 W, t = 7 min, method A]; yield: 89%, or [P = 350 W,
Mg: C,
The Pcs 2–4 were suspended in dichloromethane (100 mL) and
BBr (24 mL, 254 mmol) was added under N . The mixtures were
8
3
2
2
stirred for 3 days at room temperature, then methanol was added
slowly and dark green suspensions were formed. The suspended
solutions were centrifuged. The precipitated solids were filtered
off, washed with methanol and dried under vacuum, to yield 78–
85% of Pcs 12–14, respectively, as black green powders.
[
t = 5 min, method B]; yield: 85%. Anal Calc. for C40
6
NMR (DMSO-d ) d (ppm): 3.65 (s, 24H, OMe), 7.23 (s, 8H, ArCH).
IR (KBr)
32 8 8
H N O
1
1.83; H, 4.15; N, 14.42. Found: C, 60.71; H, 3.80; N, 14.94%. H
6
À1
m
(cm ): 2950, 2929, 2848, 1651, 1543 (s), 1469 (s),
1
7
6
439 (m), 1317 (m), 1225 (m), 1141 (s), 1127, 922 (s), 879 (m),
2.7.1. [(OH)
8
PcH
2
] (12)
À5
3
À1
À1
À1
56 (m). UV–vis (DMF), kmax (nm) [(10 log
80(5.22), 610(4.90), 353(5.19). MS (FD): m/z 777.05 (M ).
e
dm mol cm )]:
IR (KBr)
m
(cm ): 3228–3220 (br), 3310 (br), 2953, 2926, 2853,
+
1650, 1542 (s), 1468 (s), 1439 (m), 1320 (m), 1270 (m), 1145 (s),
À5
1
log
128, 921 (s), 880 (m), 753 (m). UV–vis (DMF), kmax (nm) [(10
3
À1
À1
e dm mol cm )]: 697(5.22), 662(5.18), 633(4.19),
2
[
.6.5. (2,3,9,10,16,17,23,24-octamethoxyphthalocyaninato)cobalt(II),
(OMe) PcCo] (7) [50]
This product was obtained as a violet powder from CoCl
P = 360 W, t = 10 min, method A]; yield: 58%. UV–vis (DMF), kmax
+
6
01(4.85), 345(5.24). MS (FD): m/z 642.54 (M ).
8
2 2
Á6H O
2
.7.2. [(OH)
8
PcZn] (13)
[
(
3
À1
IR (KBr)
m
(cm ): 3310 (br), 2955, 2923, 2850, 1658, 1541 (s),
À5
3
À1
À1
nm) [(10
46(5.20). MS (FD): m/z 811.68 (M ).
log e dm mol cm )]: 668(5.26), 602(4.83),
1
8
e
467 (s), 1439 (m), 1320 (m), 1270 (m), 1141 (s), 1129, 922 (s),
+
À5
81 (m), 751 (m). UV–vis (DMF),
k
max (nm) [(10
log
3
À1
À1
dm mol cm )]: 687(5.19), 620(4.88), 357(5.16). MS (FD):
+
m/z 705.91 (M ).
2
[
.6.6. (2,3,9,10,16,17,23,24-octamethoxyphthalocyaninato)iron(II),
(OMe) PcFe] (8) [50]
This product was obtained as a black blue powder from
NH Fe(SO [P = 360 W, t = 12 min, method A]; yield: 52%.
8
2
.7.3. [(OH)
8
PcCu] (14)
À1
IR (KBr)
m
(cm ): 3310 (br), 2955, 2923, 2850, 1658, 1541 (s),
(
)
4 2
4 2
)
À5
3
À1
+
À1
1467 (s), 1439 (m), 1320 (m), 1270 (m), 1141 (s), 1129, 922 (s),
UV–vis (DMF),
k
max (nm) [(10
log e dm mol cm )]:
À5
881 (m), 751 (m). UV–vis (DMF),
k
max (nm) [(10
log
6
52(5.24), 594(4.81), 383(5.21). MS (FD): m/z 808.59 (M ).
3
À1
À1
e
dm mol cm )]: 679(5.22), 610(4.87), 353(5.19). MS (FD):
+
m/z 704.07 (M ).
2
.6.7. (2,3,9,10,16,17,23,24-octamethoxyphthalocyaninato)ruthenium
II), [(OMe) PcRu] (9)
This product was obtained as
RuCl O [P = 370 W, t = 11 min, method A]; yield: 45%. Anal.
Á3H
Calc. for C40 Ru: C, 56.27; H, 3.88; N, 13.72. Found: C,
(
8
2.8. General procedure for the synthesis of tetraethynyl-substituted
phthalocyanines
a
blue-green solid from
3
2
H
32
N
8
O
8
Pcs 12–14, 3,4-diflurophenylacetylene (0.6 g, 4 mmol) and a
small quantity of potassium carbonate (0.12 g, 0.855 mmol) were
heated at 60 °C in DMF (70 mL) for 24 h under N . The mixtures
2
were cooled, then methanol was added slowly and green suspen-
sions were formed. The suspended solutions were centrifuged.
The precipitated solids were filtered off, washed with methanol
and dried under vacuum. The crude products were purified by a
1
6
5
2
2
1
5.27; H, 4.10; N, 13.98%. H NMR (DMSO-d ) d (ppm): 3.95 (s,
À1
4H, OMe), 7.39 (s, 8H, ArCH). IR (KBr)
m
(cm ): 2952, 2923,
845, 1658, 1542 (s), 1465 (s), 1433 (m), 1313 (m), 1222 (m),
145 (s), 1128, 919 (s), 879 (m), 745 (m). UV–vis (DMF), kmax
À5
3
À1
À1
(
nm) [(10
log
e dm mol cm )]: 624(5.15), 568(4.79),
+
3
82(5.20). MS (FD): m/z 853.81 (M ).

T.E. Youssef / Polyhedron 29 (2010) 1776–1783
1779
Soxhlet extractor, extracting for 2 days with acetone and dichloro-
methane to yield 70–77% of the corresponding tetraethynyl-substi-
tuted phthalocyanines 15–17 as green powders.
2.8.3. Tetraethynyl-substituted phthalocyanine (17)
Anal. Calc. for C64 Cu: C, 69.91; H, 2.44; N, 9.70. Found:
C, 70.11; H, 2.21; N, 10.22%. H NMR (DMSO-d ) d (ppm): 3.4 (s, 1H,
24 8 8
H N O
1
6
4
x CH„CH), 7.3 (s, 8H, ArCH), 8.4 (s, 4H, ArCH), 8.6 (d, 8H, ArCH).
À1
IR (KBr)
m
(cm ): 3392(CH„CH), 2957, 2930, 2857, 1655, 1542 (s),
2
.8.1. Tetraethynyl-substituted phthalocyanine (15)
1466 (s), 1436 (m), 1319 (m), 1228 (m), 1138 (s), 1123, 918 (s), 883
À5
Anal. Calc. for C64 : C, 73.27; H, 3.53; N, 10.83. Found: C,
H
26
N
8
O
8
(m), 749 (m). UV–vis (DMF), kmax (nm) [(10
log
1
6
3
À1
À1
7
3.01; H, 3.80; N, 9.94%. H NMR (DMSO-d ) d (ppm): À3.9 to À3.7
e dm mol cm )]: 675(5.19), 605(4.80), 345(5.16). MS (FD):
+
(
br, 2H, NH), 3.6 (s, 1H, 4x CH„CH), 7.54 (s, 8H, ArCH), 8.2 (s, 4H,
m/z 1096.49 (M ).
À1
ArCH), 8.7 (d, 8H, ArCH). IR (KBr)
m
(cm ): 3415 (CH„CH), 3239–
3
1
248 (br), 2955, 2922, 2850, 1650, 1543 (s), 1468 (s), 1435 (m),
318 (m), 1230 (m), 1141 (s), 1125, 922 (s), 880 (m), 751 (m).
3. Results and discussion
À5
3
À1
À1
UV–vis (DMF),
kmax (nm) [(10
log e dm mol cm )]:
6
97(5.26), 662(5.16), 634(4.23), 600(4.88), 342(5.19). MS (FD):
Our synthetic routes start from the commercially obtained
1,2-dimethoxybenzene, which was brominated to 1,2-dibromo-
+
m/z 1034.96 (M ).
4
,5-dimethoxybenzene using molecular bromine according to a
procedure reported earlier [51]. Replacing the bromine atom
with a cyano group was carried out by the Rosenmund–Von
Braun reaction, yielding the corresponding 4,5-dimethoxypht-
halonitrile 1.
2
.8.2. Tetraethynyl-substituted phthalocyanine (16)
Anal. Calc. for C64 Zn: C, 69.99; H, 3.20; N, 10.20. Found:
C, 69.01; H, 3.70; N, 9.94%. H NMR (DMSO-d ) d (ppm): 3.4 (s, 1H,
24 8 8
H N O
1
6
4
x CH„CH), 7.3 (s, 8H, ArCH), 8.4 (s, 4H, ArCH), 8.6 (d, 8H, ArCH).
The author has chosen 4,5-dimethoxyphthalonitrile 1 as a pre-
cursor to prepare the metal-free octamethoxyphthalocyanine 2 or
À1
IR (KBr)
m
(cm ): 3390 (CH„CH), 2956, 2929, 2856, 1653, 1541
(
(
e
s), 1466 (s), 1433 (m), 1320 (m), 1229 (m), 1140 (s), 1126, 920
metallo-octamethoxyphthalocyanines
[(OMe)
8
PcM]
(3–11),
À5
s), 881 (m), 750 (m). UV–vis (DMF), kmax (nm) [(10
dm mol cm )]: 687(5.23), 620(4.83), 357(5.21). MS (FD): m/
log
(M = Zn, Cu, Ni, Mg, Co, Fe, Ru, TiCl and RhCl) because of their lower
yields in preparation by conventional thermal treatment under
strictly similar sets of conditions as described in the literature
3
À1
À1
+
z 1098.32 (M ).
O
O
O
O
N
N
i
5
0 %
NH
N
N
(
Reported)
O
O
N
N
N
N
ii
6
0 %
(
This work)
HN
iii
6
8 %
1
(This work)
O
O
2
O
O
Complex
M
H2
2
O
O
3
2+
Zn
Cu
Ni
2
2+
2+
+
4
O
O
5
N
6
Mg
Co
7
2+
N
N
N
N
8
2+
3+
Method B
Fe
Method A
iv
N
M
N
9
Ru
v
10
TiCl
1
1
RhCl
N
O
O
O
O
3-11
i: DMF, DBU, 150 °C [58]
ii: hv, 150 W, 3.5 hrs, 2-ethoxyethanol, 75 °C
iii: Microwave, 350 W, 8 min, DMAE
iv: Microwave, 300-370 W, 5-11 min, DMAE
v: Microwave, 350-370 W, 7-10 min, DMAE
Scheme 1. The synthesis of metal-free and metallo-octamethoxyphthalocyanines 2–11.

1
780
T.E. Youssef / Polyhedron 29 (2010) 1776–1783
previously [51,59,60], for example the yields in case of M = Co and
Fe were 41.1% and 37%, respectively [51]. The general aspects of
the synthetic route are shown in Scheme 1.
For ultraviolet and microwave irradiation of phthalonitriles to
MPcs, various conditions have been examined in a trial to study
the parameters that influence the formation and yields of metal-
free and metallophthalocyanines, such as starting materials, reac-
tion temperature, solvent, additives and use of the conventional
chemicals.
w
During the M -assisted transformation of 1, when the reaction
time or the temperature was increased, coloration of the mixture
and formation of some Pcs were detected by TLC in several cases.
Obviously, the excess of DBU acted as a sufficiently strong base
to promote the tetramerization, whilst without DBU no Pcs were
formed under these conditions.
It was found that the molar ratios of the reagents (i.e., phthalo-
nitrile (1) to the inorganic salt) influenced the conversion as well as
3.1. UV irradiation effect on Pc formation
1
.2
The author suggested very mild conditions for preparing
2
3
4
6
phthalocyanines at room temperature with the use of a series of
primary alcohols, DBU as a base and metals that had different nat-
ural activity but were not chemically activated.
1.0
We started our UV-irradiation experiments for the preparation
of metal-free octamethoxyphthalocyanine 2 by using ethanol and
methanol as solvents in the presence of DBU as a catalyst. 4,5-Dim-
ethoxyphthalodinitrile 1 was put in a quartz tube. The mixture was
well stirred, and then irradiated for 3.5 h in a photochemical reac-
tor (mercury lamp of 150 W) at 70–75 °C under dry nitrogen, and
low quantitative yields were obtained of 40% and 44%. In a parallel
experiment, octamethoxyphthalocyanine 2 was formed in 52%
yield by using DMAE as the solvent. We observed that by using
0
0
.8
.6
0.4
0
0
.2
.0
2
-ethoxyethanol as the solvent and in the presence of DBU as a cat-
alyst at 70 °C, the yield increased to 60%, which indicated that 2-
ethoxyethanol appeared to be a good solvent for Pc formation by
UV-irradiation.
300
400
500
600
700
800
Wavelength (nm)
In a trial to prepare the corresponding metallophthalocyanines
3
–11 with UV-irradiation under the same conditions as above, all
Fig. 1. UV–vis spectra of Pcs 2–6 in DMF.
attempts were failed. Unfortunately, as was mentioned in earlier
work describing the synthesis of metallophthalocyanines with
UV-irradiation [61], our results indicate that it is difficult to pre-
pare and separate them.
7
8
9
10
3.2. Microwave irradiation effect on Pc formation
1.0
11
The preparation of the metal-free octamethoxyphthalocyanine
2
by microwave-assisted cyclization of 4,5-octamethoxyphthalo-
nitrile 1 under various conditions has been examined. The most
frequently used base is DBU in DMAE, and using 350 W irradiation
power the reaction went to completion in 8 min.
In the case of MPcs 3–11, we started the preparation with a
lower power of 200–300 W for 15–20 min in the presence of
DBU in DMAE, but no Pcs were formed. To solve this problem,
0
0
.5
.0
we controlled the temperature during the syntheses under M
conditions. Thus, 300–370 W power of M -irradiation was ap-
w
w
plied to precursor 1 in DMAE and DBU as a base, in the presence
of anhydrous metal chlorides as metal sources, for 5–12 min.
MPcs 3–11 were formed and isolated in 40–89% yields after
purification.
4
00
500
600
700
800
Wavelenght(nm)
Fig. 2. UV–vis spectra of Pcs 7–11 in DMF.
Table 1
Comparison between method A and method B in yields and times.
Complex
Metal
Microwave method
Power (Watt)
Time (min)
Yield (%)
3
4
5
6
7
8
9
Zn
Cu
Ni
Mg
Co
A/B
A/B
A/B
A/B
A
300/370
330/350
300/350
350
360
360
8/10
7/8
5/8
5/7
10
72/78
60/62
80/83
85/89
58
Fe
Ru
A
A
12
11
52
45
370
1
1
0
1
TiCl
RhCl
A
A
360
360
10
11
40
52

T.E. Youssef / Polyhedron 29 (2010) 1776–1783
1781
the yields, and the best results were obtained when 1 was used in
an excess in comparison to the metal salts.
The electronic spectra are especially fruitful in establishing the
structure of the phthalocyanines. The phthalocyanines exhibit typ-
ical electronic spectra with two strong absorption regions, one of
them is in the UV region at about 300–350 nm (B-band) and the
other one is in the visible region at 600–700 nm (Q-band). The
UV–vis spectrum of the metal-free octamethoxyphthalocyanine 2
in DMF showed a doublet Q-band at kmax 696 and 661 nm as a re-
Table 1 shows the difference in the yields of the formation of
Pcs 3–11 under microwave irradiation with method A or with
method B, in which the best results were obtained in both cases.
The yields of products under conventional conditions were much
lower and the purity of the products were unacceptable.
sult of its D
346 nm (Fig. 1). The UV–vis absorption spectra of the octa-
methoxyphthalocyanine complexes [(OMe) PcM] (3–11) in DMF
2
h symmetry, while the B-band remained at kmax
3.3. Characterization of octasubstituted phthalocyanines 2–14
8
The IR spectra of metal-free 2 and metallophthalocyanines 3–11
are given in Figs. 1 and 2. These compounds show the expected
absorptions in the main peaks of the Q and B bands (see Section
2). The UV–vis spectra of 12–14 are quite similar in shape in com-
parison with the starting materials, the octamethoxyphthalocya-
are very similar. The only difference is the presence of a NH
À1
stretching band at 3229–3222 cm due to the inner core. This
band was absent in the spectra of the metallophthalocyanines 3–
1
1. In the IR spectra of octahydroxyphthalocyanines [(OH)
8
PcM]
8 2
nine complexes [(OMe) PcM] (2–4), (M = H , Zn, Cu). Only a
small red shift of the Q-bands of between 1 and 5 nm was observed
for 12–14 in comparison with 2–4.
À1
(12–14) the appearance of OH stretches at
m
= 3228–3210 cm
were observed.
All the spectral investigations of the newly synthesized phthal-
ocyanines were in accordance with the proposed structures. The
H NMR spectra of 2 and 12 in DMSO-d showed the inner core –
In the mass spectrum of all the prepared compounds 2–14, the
observed molecular ion peaks confirmed the proposed structure.
1
6
NH protons of the metal-free phthalocyanines at d = À4.1 to
À3.8 ppm. The signals related to aromatic and aliphatic protons in
the macrocyclic moieties and the phthalocyanine skeleton gave sig-
nificant absorbances characteristic of the proposed structure. The
aromatic protons appeared as a multiplet at d = 7.30–7.39 ppm
3.4. Synthesis and characterization of tetraalkynyl-substituted
phthalocyanines 15–17
According to the literature [54–58], alkynyl-containing Pc-
systems have been synthesized mainly by following two different
synthetic strategies: (i) the cyclotetramerization of alkynyl-substi-
3
and aliphatic CH protons as a singlet at d = 3.80–3.95 ppm.
O
O
HO
OH
O
O
HO
OH
N
M
N
N
M
N
N
N
N
N
N
N
N
N
BBr , 20 °C
3
N
N
N
N
3
days
O
O
OH
HO
O
O
HO
12-14
78-85%)
OH
2
-4
(
CH
K CO3
2
4 h
2
DMF
0 °C
6
F
F
CH
HC
O
O
O
O
N
Complex
M
N
N
N
N
1
5
6
H2
Zn2+
Cu 2+
N
M
N
1
1
7
N
O
O
O
O
CH
CH
1
5-17
(
70-77 %)
Scheme 2. The synthesis of tetraalkynyl-substituted phthalocyanines 15–17.

1
782
T.E. Youssef / Polyhedron 29 (2010) 1776–1783
tuted phthalonitriles and (ii) the incorporation of alkynyl-contain-
ing moieties onto a preformed Pc macrocycle via some metal cata-
lyzed coupling reactions.
1
17
4
1
.2
.0
1
In our work, the preparation was carried through the demethyl-
ation of octamethoxyphthalocyanines [(OMe)
Zn, Cu), by stirring in BBr for 3 days, affording the octa-
hydroxyphthalocyanines [(OH) PcM] (12–14) [59] (M = H , Zn, Cu).
The addition of 3,4-diflurophenylacetylene to Pcs 12–14 in the
presence of a small quantity of potassium carbonate converted
them into the tetraalkynyl-substituted phthalocyanines 15–17 as
shown in Scheme 2. The green tetraethynyl-substituted phthalocy-
anines 15–17 were obtained as a mixture of isomers, as expected.
This presence of isomers could be verified by the slight broadening
8 2
PcM] (2–4) (M = H ,
0.8
0.6
0.4
3
8
2
0
.2
.0
encountered in the UV–vis absorption bands and broadening in the
0
1
H NMR spectra as compared with the spectra of
a-tetra-substi-
tuted Pcs composed of a single isomer [56]. The structures and
purities of Pcs 15–17 were confirmed by 1H NMR spectroscopy,
elemental analysis and UV–vis absorption spectroscopy.
3
00
400
500
600
700
800
Wavelength (nm)
1
6
The H NMR spectrum of 15 in DMSO-d showed the inner core
NH protons of the metal-free phthalocyanine at d = À3.9 to
Fig. 4. UV–vis spectra of Pc 14 in DMF (- - -) and 17 (—).
–
À3.7 ppm. The signals related to aromatic and aliphatic protons
in the macrocyclic moieties and phthalocyanine skeleton gave sig-
nificant absorbance characteristics of the proposed structure for
the Pcs 15–17. The aromatic protons appeared as a singlet at
d = 7.3–8.40 ppm. The confirmation of the presence of CH„CH
groups in the derived Pcs 15–17 has been clearly shown by the
the UV–vis spectra of the starting materials octamethoxyphthalo-
cyanine complexes [(OH) PcM] (12–14) (M = H , Zn, Cu, respec-
8
2
tively), as is shown in the UV–vis spectra of 15–17 (see Figs. 3
and 4). The tetraalkynyl zinc(II) Pc derivative 16 exhibits an in-
tense Q-band around kmax = 687 nm and the Q-band of the tetra-
alkynyl copper(II) Pc derivative 17 appears at kmax = 675 nm.
In the mass spectra of all the prepared compounds 15–17, the
observed molecular ion peaks confirmed the proposed structures.
The solubilities of the alkynyl substituents can be easily fine-
tuned to comply with the requirements of a given medium for a
specific application.
1
H NMR spectra with a peak at d = 3.2–3.4 ppm, appearing as a sin-
glet. The IR spectra of the metal-free 15 and metallophthalocya-
nines 16 and 17 are very similar. The only difference is the
À1
presence of the NH stretching band at 3239–3248 cm in the me-
tal-free Pc 15 due to the inner core. This band was absent in the
spectra of the metal complexes 16 and 17. The IR spectra of 15–
1
7 showed the disappearance of OH stretches, along with the
À1
appearance of new band at
m
3390–3425 cm
arising from
4. Conclusions
CH„CH groups. The NH proton of the metal-free tetraalkynyl-
1
substituted phthalocyanine 15 was also identified in the H NMR
8 2
Here, we were able to prepare metal-free [(OMe) PcH ] (2), un-
spectrum with a broad peak at d À3.9 to À3.7 ppm, which becomes
der UV or microwave irradiation methods. Both methods enable us
to greatly shorten the reaction time and avoid laboratory pollution
by using an oil bath as in the case of the conventional thermal
method. Therefore it is very attractive from the viewpoint of green
absent on deuterium exchange.
The UV–vis spectrum of the metal-free tetraalkynyl-substi-
tuted phthalocyanine 15 showed a doublet Q-band at kmax = 697
and 662 nm, as a result of the D
2
h symmetry, while the B-band
8
chemistry. Also, the metallophthalocyanines [(OMe) PcM] (3–11)
remained at kmax = 342 nm. The attachment of alkynyl groups at
the periphery of the given Pcs 15–17 cannot change the absorp-
tions bathochromically or hyperchromically in comparison with
(M = Zn, Cu, Ni, Mg, Co, Fe, Ru, TiCl and RhCl) have been prepared
under microwave irradiation.
The efficient microwave syntheses were performed easily with-
in a reduced timescale using phthalonitrile 1, leading by far to the
best results to date, i.e. higher yield, clean reaction product and to
easy-to-perform procedures with considerable improvements over
classical methods.
1
1
0
0
0
0
0
.2
.0
.8
.6
.4
.2
.0
The demethylation of the octamethoxyphthalocyanines
1
1
3
6
[(OMe)
hydroxyphthalocyanines [(OH)
,4-diflurophenylacetylene to the ring oxygens of [(OH)
12–14) has been used to prepare the functionalized tetraethy-
PcM] (2–4) has been used to prepare the precursors octa-
PcM] (12–14). The addition of
PcM]
8
8
3
8
(
nyl-substituted phthalocyanines 15–17.
It was thought that our work is a further example of the com-
mercial application of microwaves for organic synthesis.
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