One-pot synthesis and characterization of new cuprous pyrazinoporphyrazines containing peripherally functionalized units

Article abstract of DOI:10.1016/j.molstruc.2012.06.021

The synthesis and characterization of some new peripherally substituted Cu-pyrazinoporphyrazines (Cu-Pzs) is described. The prepared α-dicyano compounds in the presence of cuprous chloride produced porphyrazine counterparts via one-pot cyclotetramerization reaction. The resulted porphyrazines are useful photosensitizers and good reagent for photodynamic therapy of cancer.

Full text of DOI:10.1016/j.molstruc.2012.06.021

Journal of Molecular Structure 1029 (2012) 92–97
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
One-pot synthesis and characterization of new cuprous pyrazinoporphyrazines
containing peripherally functionalized units
⇑
Ziba Khodaee, Asieh Yahyazadeh, Nosrat O. Mahmoodi , Mohammad Ali Zanjanchi, Vahid Azimi
Department of Organic Chemistry, University of Guilan, P.O. Box 1914, Rasht, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
The synthesis and characterization of some new peripherally substituted Cu-pyrazinoporphyrazines (Cu-
Pzs) is described. The prepared a-dicyano compounds in the presence of cuprous chloride produced por-
phyrazine counterparts via one-pot cyclotetramerization reaction. The resulted porphyrazines are useful
photosensitizers and good reagent for photodynamic therapy of cancer.
Ó 2012 Elsevier B.V. All rights reserved.
Received 13 March 2012
Received in revised form 9 June 2012
Accepted 11 June 2012
Available online 10 July 2012
Keywords:
Porphyrazine
Pyrazinoporphyrazine
Phthalocyanine
Photosensitizer
Photodynamic therapy (PDT)
1. Introduction
non-linear optics, photosensitizers, anticancer, anti AIDS, DNA
cleavers, photochromism, photocatalyst, optical filters, thermally
Recently, synthesis and application of phthalocyanines (Pcs),
porphyrazines (Pzs) and related macrocycles modified by periphe-
ral substituent attachments, have been reported as great interest-
ing subjects because of their vast applications in diverse areas.
For example photodynamic therapy (PDT) has been used as a po-
tential treatment source for many forms of cancers, curing early
or localized disease, improving the quality of life in advanced dis-
ease and increasing survival [1–3]. The photosensitizing compound
(Pz), visible light and molecular oxygen are three main compo-
nents of PDT wherein, photosensitizer absorbs the light and
efficiently transfers the energy to ground state triplet oxygen form-
ing highly reactive singlet oxygen that destroys the target tissues
selectively [1,2,4–8]. Photodegradation of chlorophenol pollutants
with singlet oxygen generated by irradiation of the supported
phthalocyanine derivatives has also been reported successfully
[9–11]. Therefore, improving the Pz as photocatalyst to be active
in the visible or near-infrared region of light has been a highly ac-
tive research topic in recent years. Some improved routes for
example; immobilization of metal complexes onto solid supports
[9,12], binuclear annulations of porphyrazines [13,14] and periph-
eral substitution of porphyrazines [4,15–18] have been quoted. The
application of porphyrazines in switches, information storage,
imaging devices, dyes, liquid crystals, semiconductor devices,
stable polymers, degradation of organic pollutants, redox proper-
ties, solar cells, electron transfer, magnetic interactions and iono-
phoric activity have been reported too [4–7,9,13–22].
The cyclic-tetramerization of a-dicyano compounds is the most
important synthetic route for producing porphyrazine derivatives.
The importance of dicyanopyrazine derivatives has been men-
tioned mainly in the chemical industry, food, agricultural and
medicinal chemistry [19]. The specific properties of 2,3-dicyano-
pyrazine derivatives are resulted from the two strong electron
withdrawing cyano groups on the pyrazine ring. In the present
work, we have carried out the premade 2,3-dicyanopyrazine deriv-
atives for the one-pot synthesis of some novel Cu(II)-pyrazinopor-
phyrazines by direct cyclic-tetramerization.
2. Experimental section
2.1. General
The UV–Vis spectra were measured on a Shimadzu UV-2100
spectrometer. The 1H NMR (500 MHz) spectra were obtained with
a Bruker 500 DRX-Avance NMR and the others (400 MHz) were
registered with a Bruker 400 Avance 3 spectrometer. The IR spectra
were taken with a Shimadzu 470 spectrometer using KBr pellets.
Melting points of crystalline dicyano compounds were measured
with a Electrothermal melting point apparatus and have not been
corrected. Mass spectra were recorded on a GC–MS Agilent
⇑
Corresponding author. Tel./fax: +98 1313233262.
E-mail addresses:
mahmoodi@guilan.ac.ir,
nosmahmoodi@gmail.com
(N.O. Mahmoodi).
0022-2860/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molstruc.2012.06.021

Z. Khodaee et al. / Journal of Molecular Structure 1029 (2012) 92–97
93
Technologies QP-5973 N MSD instrument. Typical reaction proce-
dures and spectroscopic data for all products are described below.
2.3. Synthesis of tetrapyrazinoporphyrazines (7–10): a general
procedure
A mixture of
a
-dicyano precursor (1–4) (5.5 mmol), an equiva-
2.2. Synthesis of a-dicyano derivatives (1–5): a general procedure
lent amount of Cu(I)Cl in 10 ml of o-dichlorobenzene was heated at
160–180 °C for 18 h. The deep greenish suspension product was
cooled and allowed to stay for overnight in room temperature.
The solution was filtered and washed with 5% HCl aqueous solu-
tion and ammonia solution. The precipitate was washed with
EtOAc, (CH3)2CO and MeOH repeatedly. The crude products were
purified by column chromatography using the eluent solvents;
CH2Cl2/DMF for compounds 7,10 and CH2Cl2/EtOH for compounds
8,9 in that order (The silica gel is the stationary phase for the chro-
matographic column).
A solution of benzil (0.036 mol), DAMN (4.73 g, 0.044 mol) and
p-toluenesulfonic acid (0.02 g) in EtOH (50 ml) was refluxed for
5 h. In the end of reaction a dark cream colored suspension was
achieved. The crude mixture was filtered off and washed with
MeOH. The crude product was recrystallized from mixture solution
of CCl4/CHCl3; 1:1 to lead pure compound 1. The other dicyano
compounds 2–5 were synthesized via similar manner from
phenanthraquinone, dinitrobenzil, dinitro phenanthraquinone
and 1,4-benzodialdehyde respectively, the recrystallization solu-
tion for compound 2 was o-dichlorobenzene and for compounds
3–5 was 96% EtOH.
2.3.1. Copper tetra (2,3-diphenylpyrazino) porphyrazine (7)
Green needle crystals, yield 30.54%, 0.51 g; 1H NMR (dH
400 MHz, CDCl3-d6/ppm) 7.61–7.02 (m, ArH); IR (vmax KBr/cmÀ1
)
2.2.1. 5,6-Diphenylpyrazine-2,3-dicarbonitrile (1)
2938 (ArH), 1666 (C@N), 1445 (C@C); UV–Vis (kmax CH2Cl2/nm)
717 (log = 3.66), 495 (log
= 3.57); Exact mass (M+): calcd. for
72H40CuN16, 1191.2918 found 1191.2923.
Cream needle crystals, yield 83.72%, 8.5 g, mp 255 °C; 1H NMR
(dH 500 MHz, DMSO-d6/ppm) 7.48 (d, J = 7.85 Hz, 3H, 2 Â ArH),
7.41 (t, J = 7.81 Hz, 2H, 2 Â ArH); IR (vmax KBr/cmÀ1) 3058 (ArH),
2235 (CN), 1691 (C@N), 1512 (C@C); Exact mass (M+): calcd. for
e
e
C
C
18H10N4, 282.0905 found 282.0912.
2.3.2. Copper tetra (2,3-dihydrodibenzo[f,h]quinoxalino)porphyrazine
(8)
Green needle crystals, yield 35.57%, 0.59 g; 1H NMR (dH
500 MHz, CDCl3-d6/ppm) 8.60 (b, 1H, 8 Â ArH), 7.91–7.73 (b m,
3H, 8 Â ArH); IR (vmax KBr/cmÀ1) 2950 (ArH), 1677 (C@N), 1575
2.2.2. Dibenzo[f,h]quinoxaline-2,3-dicarbonitrile (2)
Greenish brown powder, yield 70.46%, 7.11 g, mp 310dec.°C; 1H
NMR (dH 500 MHz, DMSO-d6/ppm) 8.30 (d, J = 7.83 Hz, 1H,
2 Â ArH), 8.01 (d, J = 7.41 Hz, 1H, 2 Â ArH), 7.78 (t, J = 7.30 Hz, 1H,
(C@C); UV–Vis (kmax CH2Cl2/nm) 705 (loge = 2.06), 630
(log
e
= 1.55); Exact mass (M+): calcd. for C72H32CuN16, 1183.2448
2 Â ArH), 7.53 (t, J = 7.17 Hz, 1H, 2 Â ArH); IR (vmax KBr/cmÀ1
)
found 1183.2453.
3091 (ArH), 2228 (CN), 1604 (C@N), 1450 (C@C); Exact mass
(M+): calcd. for C18H8N4, 280.0749 found 280.0742.
2.3.3. Copper octanitrotetra (2,3-diphenylpyrazino) porphyrazine (9)
Green needle crystals, yield 27.16%, 0.58 g; 1H NMR (dH
400 MHz, DMSO-d6/ppm) 7.64–7.38 (m, 4H, 8 Â ArH); IR (vmax
KBr/cmÀ1) 3050 (ArH), 1590–1570 (C@N), 1540 (NO2), 1480
2.2.3. 5,6-Bis(3-nitrophenyl)pyrazine-2,3-dicarbonitrile (3)
Cream crystals, yield 76%, 9.6 g, mp 248 °C; 1H NMR (dH
500 MHz, DMSO-d6/ppm) 7.50–7.47 (m, 3H, 2 Â ArH), 7.42–7.39
(m, 1H, 2 Â ArH); IR (vmax KBr/cmÀ1) 3050 (ArH), 2240 (CN),
1690–1680 (C@N), 1585 (C@C), 1505 (NO2), 1370 (NO2); Exact
mass (M+): calcd. for C18H8N6O4, 372.0607 found 372.0615.
(C@C), 1345 (NO2); UV–Vis (kmax CH2Cl2/nm) 735 (log
e
= 3.75); Ex-
act mass (M+): calcd. for C72H32CuN24O16
1551.1736.
, 1551.1724 found
2.2.4. 6,9-Dinitrodibenzo[f,h]quinoxaline-2,3-dicarbonitrile (4)
Light green powder, yield 50.27%, 6.7 g, mp 300dec.°C; 1H NMR
(dH 500 MHz, DMSO-d6/ppm) 9.07 (d, J = 8.28, 1H, Hz, ArH), 8.94
(d, J = 8.23 Hz, 1H, ArH), 8.05 (t, J = 7.51 Hz, 2H, ArH), 7.92 (t,
J = 7.57 Hz, 1H, ArH); IR (vmax KBr/cmÀ1) 3050 (ArH), 2210 (CN),
1690 (C@N), 1500 (NO2), 1440 (C@C), 1370 (NO2); Exact mass
(M+): calcd. for C18H6N6O4, 370.0451 found 370.0446.
2.3.4. Copper octanitrotetra (2,3-dihydrodibenzo[f,h]quinoxalino)
porphyrazine (10)
Green needle crystals, yield 37.61%, 0.80 g; 1H NMR (dH
400 MHz, DMSO-d6/ppm) 9.24 (b m, 1H, 4 Â ArH), 8.94 (d,
J = 6.80 Hz, 1H, 4 Â ArH), 8.00–7.91 (m, 3H, 4 Â ArH); IR (vmax
KBr/cmÀ1) 3050 (ArH), 1690 (C@N), 1610 (C@C), 1551 (NO2),
1425 (C@C), 1371 (NO2); UV–Vis (kmax CH2Cl2/nm) 715
(log
72H24CuN24O16, 1543.1255 found 1543.1345.
e = 3.52), 660 (loge
= 3.50); Exact mass (M+): calcd. for
C
2.2.5. 2,3-Bis((Z)-(4-formylbenzylidene)amino)but-2-enedinitrile (5)
Yellow powder, yield 68.56%, 8.4 g, mp 200dec.°C; 1H NMR (dH
500 MHz, DMSO-d6/ppm) 10.05 (s, 1H, COH), 8.32–8.28 (m, 2H,
2.4. Synthesis of porphyrazine complexes (11, 12): a general procedure
ArH), 8.24 (d, J = 8.23 Hz, 4H, ArH), 8.11 (s, 3H,
a-CH), 7.97 (d,
J = 8.21 Hz, 2H, ArH); IR (vmax KBr/cmÀ1) 3193 (ArH), 2831–2742
(CH, aldehyde), 2233–2198 (CN), 1687 (C@N), 1610 (C@O), 1558
(C@C); Exact mass (M+): calcd. for C20H12N4O2, 340.0960 found
340.0968.
A mixture of 5,6-diphenylpyrazine-2,3-dicarbonitrile 1 (0.08 g,
0.29 mmol) and phthalonitrile (0.04 g, 0.29 mmol) for 1:1 mol ratio
was dissolved in o-dichlorobenzene (7 cm3) and anhydrous cop-
per(I)chloride (0.04 g, 0.38 mmol) was added. The mixture was
heated at 130 °C for 4 h. After cooling and remaining a nightlong
in room temperature, a deep greenish suspension was achieved.
The mixture was dissolved in toluene (20 cm3) and filtered. The so-
lid was dried, purified by TLC (eluent: toluene/ CH2Cl2) and re-
sulted porphyrazine 11. The compound 12 was synthesized from
dibenzo[f,h]quinoxaline-2,3-dicarbonitrile 2 as starting material,
via similar manner.
2.2.6. 5,7-Dimethyl-6H-1,4-diazepine-2,3-dicarbonitrile (6)
Colorless cubic crystals, yield 60%, 1.95 g, mp 199 °C; 1H NMR
(dH 500 MHz, DMSO-d6/ppm) 4.47 (s, 1H, CH2), 2.29 (s, 6H, CH3),
2.08–2.23 (m, 1H, CH2); IR (vmax KBr/cmÀ1) 3008 (Homo-arom,
CH2), 2956 (AliH), 2227 (CN), 1691 (C@N), 1512 (C@C); Exact mass
(M+): calcd. for C9H8N4, 172.0749 found 172.0757.

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Z. Khodaee et al. / Journal of Molecular Structure 1029 (2012) 92–97
2.4.1. Copper bis(2,3-diphenylpyrazino)-bis(3,4-benzo)porphyrazine
(11)
[2,4,9,13,19]. Some annulated binuclear complexes or coplanar
connected porphyrazines, extending -electrons system, have
p
Green solid, yield 65.46%, 0.22 g; 1H NMR (dH 500 MHz, CDCl3-
d6/ppm) 7.57–7.15 (m, 7H, 4 Â ArH); IR (vmax KBr/cmÀ1) 2911
(ArH), 1730 (C@N), 1469 (C@C); UV–Vis (kmax CH2Cl2/nm) 699
showed strong Q band absorptions greatly red-shifted [2,25,27].
Moreover investigations around porphyrazines in other aspects
revealed that peripheral substitution of porphyrazines with bulky
groups has enhanced the solubility and reduced the degree of aggre-
gation phenomenon of these compounds as well [2,4,5,17,29].
Following the mentioned explanations, in this work, the design
and synthesis of some pyrazinoporphyrazines such as; cupreous
octaphenyltetrapyrazinoporphyrazine 7, tetraphenanthrenetetra-
pyrazinoporphyrazine8, octanitrooctaphenyltetrapyrazino porphyr-
azine 9, octanitrotetraphenanthrenetetrapyrazinoporphyrazine 10,
(loge = 3.36), 641(loge = 3.21), 436(loge
= 3.50); Exact mass (M+):
calcd. for C52H28CuN12, 883.1856 found 883.1849.
2.4.2. Copper bis(2,3-dihydrodibenzo[f,h]quinoxalino)-bis(3,4-
benzo)porphyrazine (12)
Green–blue solid, yield 74.72%, 0.25 g; 1H NMR (dH 400 MHz,
DMSO-d6/ppm) 9.52 (d, J = 9.2 Hz, 1H, ArH), 9.26 (d, J = 8.8 Hz,
1H, ArH), 9.11–8/85 (m, 3H, ArH), 8.33 (s, 1H, ArH), 8.09–7.84
(m, 10H, ArH); IR (vmax KBr/cmÀ1) 3036–2889 (ArH), 1740 (C@N),
enanthrenedipyrazinodibenzoporphyrazine
enanthrenedipyrazinodibenzo-porphyrazine 12 are reported as
large -conjugated systems. The 2,3-dicyanopyrazines 1–4 were
11
and
diph-
p
1597 (C@C); UV–Vis (kmax CH2Cl2/nm) 724 (log
e = 3.69), 645
= 3.65); Exact mass (M+): calcd. for C52H24CuN12, 879.1543
synthesized by one-pot condensation reaction of diaminomaleonit-
rile (DAMN) with benzil, phenanthrene-9,10-dione, dinitrobenzil
and dinitrophenanthrene-9,10-dione in EtOH respectively. The nitro
substituted precursors were synthesized via similar manner cited in
our previous works [30]. The reaction route is summarized in
Scheme 1.
(log
e
found 879.1552.
3. Results and discussion
Versatile properties like electrical conductivity, thermal stabil-
ity, catalytic properties, photoconductivity and chemical resistance
of porphyrazine complexes are mainly influenced by the nature of
the central metal ions and the substituents presented on the
periphery of porphyrazine ring [5,6,14,17–28]. porphyrazine deriv-
In looking for useful a-dicyano derivatives precursors, the new
compound 5 was derived from terephthalaldehyde via similar
manner. The experimental results show that this precursor due
to some conformational restrictions cannot respond to direct cyc-
lic-tetramerization reaction (Fig. 1).
5,7-dimethyl-6H-1,4-diazepine-2,3-dicarbonitrile 6 was previ-
ously prepared in our laboratory in excellent yield [31]. However,
atives have an extended network of
p-electrons and possess an
intensive absorption in the blue-green region of solar spectrum
and this get capable them to be efficient photocatalysts
Scheme 1. One-pot synthetic route toward preparation of 2,3-dicyanopyrazines 1–4.
Fig. 1. Structure of a-dicyano compound 5.

Z. Khodaee et al. / Journal of Molecular Structure 1029 (2012) 92–97
95
The structural assignments of resulted products were per-
formed on the basis of TLC, FT-IR, UV–Vis, MS and 1H NMR spectra.
The TLC was used for controlling the reactions progress and purifi-
cation of final products. At the end of every tetramerization reac-
tion a dark green colored mixture was obtained that after further
work up and purification, only a green–blue fraction was observed
and scraped from the TLC plate. The yields of porphyrazine deriv-
atives due to strong silica binding properties were moderately
CH3
CH2
N
NC
N
NC
CH3
6
low. The FT-IR spectra of a-dicyano compounds 1–6 in comparison
with parent dicarbonitriles exhibited the stretching vibrations of
the typical CN bands sharply within 2220–2235 cmÀ1 while the
C@O bands were disappeared thorough. Finally, the CN bands
Fig. 2. Structure of a-dicyano compound 6.
of
a-dicyano compounds were totally disappeared due to the
attempt toward macrocyclization of 6 to provide the correspond-
ing Cu-porphyrazine was failed. This failure to tetramerization
could be attributed to (a) the acidic protons adjacent to the imines
groups and (b) the steric hindrance of the molecular shape (Fig. 2)
[6].
The target porphyrazines (7–12) were successfully synthesized
via some modification of direct cyclic-tetramerization procedure
mentioned in the literature [5,19,32]. The prepared 2,3-dicyano-
pyrazines 1–4 in reaction with excess amount of Cu(I)Cl in
o-dichlorobenzene at refluxing condition produced desired tetra-
pyrazinoporphyrazines 7–10 in one-pot route, respectively
(Scheme 2).
Unexpectedly, the copper bis(2,3-diphenylpyrazino)-bis(3,4-
benzo)porphyrazine 11 and bis(2,3-dihydrodibenzo[f,h]quinoxali-
no)-bis(3,4-benzo)porphyrazine 12 were synthesized in high yields
by simultaneous cross cyclotetramerization of 1 or 2 with phthalo-
nitrile (1 or 2: phthalonitrile for mol ratio 1:1) in the presence of
Cu(I)Cl respectively (Scheme 3). The major products 11 and 12
with D2h symmetry appeared as deep-colored fractions and were
scraped from the preparative TLC. The other possible regioisomer
was very negligible appeared as pale fraction and was not possible
to isolate. The comparable phorphyrazine with different compo-
nents has been also reported [5].
cyclotetramerization reaction and converted to C@N bands of
porphyrazine counterparts (1604–1691 cmÀ1) (e.g. see Fig. 3,
compound 7).
In the UV–Vis spectra, the strongest peaks around 700 nm are
assigned as the Q band, which could be attributed to the allowed
p–
pà transition of porphyrazine ring. In this work, the majority
of synthesized porphyrazines showed sharp and unsplit Q bands
demonstrating the monomeric form and D4h symmetry of these
compounds, as expected for macrocycles with central metal ions.
In the cases that symmetry reduces to D2h, the LUMO orbital loses
its alignment therefore; the Q band splits into two Qx and Qy bands
of the highest isomer symmetry [5,25]. In the resulted compounds
7–12, the Q bands (kmax) were recorded at 717 nm (log
705 nm (log
699 nm (log
e
e
= 3.66),
= 3.52),
e
e
= 2.06), 735 nm (log
e
= 3.75), 715 nm (log
= 3.36) and 724 nm (log
e
= 3.69) in CH2Cl2 solvent
respectively. For example, the Q bands absorption of 7 showed; a
bathochromic shift (red shift) at 18 nm and a hypsochromic shift
(blue shift) at 18 nm, in comparison with 11 and 9 respectively.
These sequences may be assigned to the extended p-electrons net-
work in porphyrazine 7 and the presence of peripherally with-
drawing substituents in porphyrazine 9. Consequently the
maximum absorptions move to visible or near-infrared region of
Scheme 2. Synthetic route toward complexes 7–10.

96
Z. Khodaee et al. / Journal of Molecular Structure 1029 (2012) 92–97
Scheme 3. Synthetic route toward complexes 11 and 12.
Fig. 3. Comparative FT-IR spectra of (a) benzil, (b) 2, 3-dicyanopyrazine 1 and (c) porphyrazine 7.
substituents on the periphery of the fused benzene rings or in our
cases pyrazine rings causes the peak to be broadened to some ex-
tent. For example in the phthalocyanine derivatives with no
peripheral substituent or fused rings, due to structural symmetry
and steady energy levels, the peaks are so sharp and unbroaden
[6,25,28].
1H NMR spectra of
a-dicyano intermediates 1–6 revealed exact
desired bands in detail. However, the 1H NMR spectra of 7–12 re-
lated to the aromatic protons of the porphyrazine were displayed
as broad signals. This peaks broadness arises from the paramagne-
ticity of Cu(II), together with some aggregation issues. The synthe-
sized porphyrazines (7,8,10,12) in spite of heating under vacuum
due to some hydrophilic properties, retain residual moisture, as
indicated in their FT-IR spectra (3200–3500 cmÀ1).
4. Conclusion
Some
analogouses. The
a
-dicyano derivatives were synthesized from dicarbonyl
-dicyano compounds by using a cyclotetramer-
a
Fig. 4. Comparative UV–Vis spectra of 7,9 and 11 in CH2Cl2.
ization reaction in the presence of copper chloride produced new
cupreous pyrazinoporphyrazines. Two prepared dinitriles 5 and 6
did not respond to the process probably due to some steric hin-
drances or structural effects on tetramerization mechanism.
light (Fig. 4). Although, the sharp and unsplit Q band is character-
istic of D4h symmetry for porphyrazines 7–12, however addition of

Z. Khodaee et al. / Journal of Molecular Structure 1029 (2012) 92–97
97
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Acknowledgment
The partial support of this research by the Research Committee
of University of Guilan is gratefully acknowledged.
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