Microwave-assisted synthesis and characterization of a new metal-free and metallophthalocyanines

Article abstract of DOI:10.1080/00958971003645953

Dinitrile monomer (3) was synthesized by nucleophilic aromatic substitution of 4-phenoxyphenol (1) with 4-nitrophthalonitrile (2). The metal-free phthalocyanine (4) was prepared by the reaction of dinitrile monomer (3) with DMAE. Ni(II), Co(II), and Zn(II) metallophthalocyanines were prepared by the reaction of 3 with chlorides of Ni(II), Co(II), and Zn(II) in DMAE. The new compounds were characterized by IR, ¹H- and ¹³C-NMR, UV-Vis, elemental analysis, and MS specral data.

Full text of DOI:10.1080/00958971003645953

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Microwave-assisted synthesis and
characterization of a new metal-free
and metallophthalocyanines
Meltem B. Kılıçaslan a , Fatma Ağın a & Halit Kantekin a
a Department of Chemistry , Karadeniz Technical University ,
61080 Trabzon, Turkey
Published online: 23 Feb 2010.
To cite this article: Meltem B. Kılıçaslan , Fatma Ağın & Halit Kantekin (2010) Microwave-assisted
synthesis and characterization of a new metal-free and metallophthalocyanines, Journal of
Coordination Chemistry, 63:5, 861-867, DOI: 10.1080/00958971003645953
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Journal of Coordination Chemistry
Vol. 63, No. 5, 10 March 2010, 861–867
Microwave-assisted synthesis and characterization of a new
metal-free and metallophthalocyanines
_
˘
MELTEM B. KILIC¸ ASLAN, FATMA AGIN and HALIT KANTEKIN*
Department of Chemistry, Karadeniz Technical University, 61080 Trabzon, Turkey
(Received 31 July 2009; in final form 12 October 2009)
Dinitrile monomer (3) was synthesized by nucleophilic aromatic substitution
of 4-phenoxyphenol (1) with 4-nitrophthalonitrile (2). The metal-free phthalocyanine (4) was
prepared by the reaction of dinitrile monomer (3) with DMAE. Ni(II), Co(II), and Zn(II)
metallophthalocyanines were prepared by the reaction of 3 with chlorides of Ni(II), Co(II), and
Zn(II) in DMAE. The new compounds were characterized by IR, 1H- and 13C-NMR, UV-Vis,
elemental analysis, and MS specral data.
Keywords: Phthalocyanine; Microwave; Phthalonitrile
1. Introduction
Since their accidental synthesis in 1928, phthalocyanines (Pcs) have been used in dyes,
paints, color for metal surface, fabrics, and plastics. Pcs are found in liquid crystals,
catalysts, gas sensors, non-linear optics, photosensitizers for photodynamic therapy
(PDT) of cancer, thin films, fibrous assemblies, and laser service substances [1–4]. Pcs
are generally insoluble in common organic solvents, although their solubility can be
improved by incorporation of substituents such as phenoxy, alkyl, or alkoxy of different
chain lengths [5, 6] or branched system at peripheral positions [7–12]. The solubility
of Pcs is very important for new technological applications as advanced materials, apart
from their traditional use as industrial dyes and pigments.
Microwave-promoted organic reactions can accelerate chemical processes with reac-
tion time and energy input reduced in reactions that are run for a long time at high
temperatures [13]. Microwave-assisted synthesis of Pcs is rare [14–16].
We previously synthesized Pcs containing long-chain substituents [17] and new sol-
uble metal Pcs containing macrocycle units on the periphery [18]. In this article, we
prepare metal-free and metallophthalocyanines bearing phenoxy groups on periph-
eral positions by microwave irridation and describe the characterization of the
new compounds.
*Corresponding author. Email: halit@ktu.edu.tr
Journal of Coordination Chemistry
ISSN 0095-8972 print/ISSN 1029-0389 online ꢀ 2010 Taylor & Francis
DOI: 10.1080/00958971003645953

862
M.B. K|l|c¸aslan et al.
2. Experimental
IR spectra were recorded on a Perkin-Elmer 1600 FT-IR spectrophotometer using
1
KBr pellets or NaCl discs. H- and 13C-NMR spectra were recorded on a Varian
Mercury 200 MHz spectrometer in CDCl3 and chemical shifts are reported relative to
Me4Si as internal standard. Mass spectra were measured on a Micromass Quattro
LC/ULTIMA LC–MS/MS spectrometer. Elemental analyses were determined using
a LECO Elemental Analyser (CHNS O932) and a Unicam 929 AA spectrophotometer.
Melting points were measured on an electrothermal apparatus and are uncorrected.
Optical spectra in the UV-Vis region were recorded with a Varian Cary 50 Conc
spectrophotometer using 1 cm path length cuvettes at room temperature.
4-Phenoxy-phenol (1) [19] and 4-nitrophthalonitrile (2) [20] were synthesized according
to reported procedures. Commercially available solvents were dried and purified by
conventional procedures [21].
2.1. Preparation of 4-(4-phenoxy-phenoxy)phthalonitrile (3)
4-Phenoxy-phenol (1) (0.75 g, 4.02 mM) was dissolved in dry DMF (15 mL) under N2 and
4-nitrophthalonitrile (2) (0.69 g, 3.90 mM) was added to the solution after stirring for
10 min; finely anhydrous K2CO3 (1.65 g, 12.06 mM) was added portionwise within 2 h
with efficient stirring. The reaction mixture was stirred under N2 at 50ꢀC for 3 days. Then
the solution was poured into ice water (165 mL) and stirred for 1 day. The precipitate
formed was filtered off and dried in vacuum over P2O5. The crude product was
crystallized from ethanol. Yield: 0.78 g (62%). m.p. 110–112ꢀC. Anal. Calcd for
C20H12N2O2 (%): C, 76.92; H, 3.84; N, 8.97. Found: C, 76.90; H, 3.87; N, 8.94. IR (KBr
tablet) Vmax (cmꢁ1): 3073 (Ar–H), 2923–2852 (Alip C–H), 2226 (CꢂN), 1595, 1497, 1283,
1238, 1191, 875, 754. 1H-NMR (CDCl3) (ꢀ : ppm) 7.75 (s, 1H, Ar–H), 7.40 (d, 1H, Ar–H),
7.26 (d, 1H, Ar–H), 7.08 (m, 6H, Ar–H), 6.95 (d, 3H, Ar–H). 13C-NMR (CDCl3),
(ꢀ : ppm): 154.43, 152.61, 133.85, 133.41, 128.99, 128.75, 127.87, 127.81, 126.03, 125.84,
124.75, 123.36, 122.25, 119.75, 118.30, 115.15. MS (FAB), (m/z): 313 [M þ 1]þ.
2.2. Preparation of metal-free Pcs (4)
A mixture of 3 (0.3 g, 0.97 mM), 0.45 mL n-penthanol, 0.05 mL 1,8-diazabicyclo
[5.4.0]undec-7-ene (DBU), and 0.03 mL dry pyridine was placed in a Schlenk tube
under N2 and degassed several times. The temperature was gradually increased to 160ꢀC
and stirred for 12 h. After cooling to room temperature, the reaction mixture was
refluxed with ethanol (15 mL) to precipitate the product which was washed with hot
ethanol and dried in vacuo. The green product was purified by preparative thin layer
chromatography using chloroform : methanol (100 : 4) as the solvent system. Yield:
0.045 g (15%) m.p. 4 300ꢀC. Anal. Calcd for C80H50N8O8 (%): C, 76.80; H, 4.00;
N, 8.96. Found: C, 76.82; H, 4.02; N, 8.99. IR (KBr tablet) Vmax(cmꢁ1): 3290 (N–H),
1
3043 (Ar–H), 2930–2859 (Alip C–H), 1219 (Ar–O–C), 1614, 1487, 1315. H-NMR
(CDCl3) (ꢀ : ppm) 8.02 (s, 4H, Ar–H), 7.75 (d, 4H, Ar–H), 7.56 (d, 4H, Ar–H), 7.24
(m, 24H, Ar–H), 7.18 (d, 12H, Ar–H). 13C-NMR (CDCl3), (ꢀ : ppm): 158.24, 154.60,
150.12, 130.17, 128.20, 124.52, 123.48, 121.46, 120.98, 118.87, 115.28, 113.43, 110.32,
108.72, 107.88, 105.00. UV-Vis (chloroform): ꢁmax (nm): [10ꢁ5 ꢂ (dm3 molꢁ1 cmꢁ1)]: 255

Metallophthalocyanines
863
(5.09), 350 (5.02), 610 (4.48), 645 (4.67), 671 (5.06), 708 (5.12). MS (FAB), (m/z): 1273
[M þ Na]þ.
2.3. Preparation of nickel(II) Pc (5)
Mixture of 3 (0.1 g, 0.320 mM), anhydrous NiCl2 (0.013 g, 0.1 mM) and 2-(dimethy-
lamino)ethanol (2 mL) were irradiated in a microwave oven at 175ꢀC, 350 W for 5 min.
After cooling to room temperature, the reaction mixture was refluxed with ethanol to
precipitate the product, which was filtered off and washed with hot ethanol and dried in
vacuum. The green solid was purified by preparative thin layer chromatography
using chloroform : methanol (100 : 4) as the solvent system. Yield: 0.238 g (57%)
m.p. 4300ꢀC. Anal. Calcd for C80H48N8O8Ni (%): C, 73.50; H, 3.67; N, 8.58. Found:
C, 73.58; H, 3.72; N, 8.63. IR (KBr tablet) Vmax(cmꢁ1): 3064 (Ar–H), 2925–2824 (Alip
1
C–H), 1488–1223 (Ar–O–C), 1093, 872, 691. H-NMR (CDCl3) (ꢀ : ppm): 7.39 (s, 4H,
Ar–H), 7.26 (d, 4H, Ar–H), 7.07 (d, 4H, Ar–H), 7.05 (m, 24H, Ar–H), 7.18 (d, 12H,
Ar–H). 13C-NMR (CDCl3), (ꢀ : ppm): 158.01, 157.88, 153.10, 135.66, 130.24, 130.05,
124.62, 124.21, 123.19, 123.27, 122.27, 121.34. 120.78, 120.59, 119.47, 118.63. UV-Vis
(chloroform): ꢁmax (nm): [10ꢁ5 " (dm3 molꢁ1 cmꢁ1)]: 242 (5.25), 302 (4.76), 623 (4.96),
677 (5.28). MS (FAB) (m/z): 1329 [M þ Na]þ.
2.4. Preparation of cobalt(II) Pc (6)
A mixture of 3 (0.1 g, 0.320 mM), anhydrous CoCl2 (0.013 g, 0.1 mM), and
2-(dimethylamino)ethanol (2 mL) was irradiated in a microwave oven at 175ꢀC,
350 W for 5 min. After cooling to room temperature, the reaction mixture was refluxed
with ethanol to precipitate product, which was filtered off, washed with hot ethanol and
dried in vacuum. The green product was purified by the preparative thin layer chro-
matography using chloroform : methanol (100 : 4) as the solvent system. Yield: 0.192 g
(46%) m.p. 4 300ꢀC. Anal. Calcd for C80H48N8O8Co (%): C, 73.45; H, 3.67; N, 8.57.
Found: C, 73.50; H, 3.70; N, 8.60. IR (KBr tablet) Vmax (cmꢁ1): 3060 (Ar–H), 2917–
2869 (Alip C–H), 1487, 1327, 1221 (Ar–O–C), 1094, 868, 751, 690. UV-Vis (chloro-
form): ꢁmax (nm): [10ꢁ5 " (dm3 molꢁ1 cmꢁ1)]: 245 (5.00), 326 (4.67), 608 (4.35), 677
(4.89). MS (FAB), (m/z): 1308 [M þ 2]þ.
2.5. Preparation of zinc(II) Pc (7)
A mixture of 3 (0.1 g, 0.320 mM), anhydrous ZnCl2 (0.013 g, 0.1 mM), and
2-(dimethylamino)ethanol (2 mL) was irradiated in a microwave oven at 175ꢀC,
350 W for 5 min. After cooling to room temperature, the reaction mixture was refluxed
with ethanol to precipitate product, which was filtered off, washed with hot ethanol
and dried in vacuum. Then the green product was purified by preparative thin layer
chromatography using chloroform : methanol (100 : 4) as the solvent system. Yield:
0.2815 g (67%) m.p. 4 300ꢀC. Anal. Calcd for C80H48N8O8Zn (%): C, 73.11; H, 3.65;
N, 8.53. Found: C, 73.20; H, 3.72; N, 8.58. IR (KBr tablet) Vmax (cmꢁ1): 3038 (Ar–H),
2924–2873 (Alip C–H), 1498, 1487, 1219 (Ar–O–C), 1091, 1043, 945, 744,
690. 1H-NMR (CDCl3) (ꢀ : ppm) 7.36 (s, 4H, Ar–H), 7.29 (d, 4H, Ar–H), 7.25

864
M.B. K|l|c¸aslan et al.
(m, 24H, Ar–H), 7.01 (d, 12H, Ar–H). 13C-NMR (CDCl3), (ꢀ : ppm): 158.00, 157.61,
157.55, 157.49, 152.88, 151.85, 149.76, 137.10, 129.76, 124.42, 123.05, 122.98, 120.81,
120.40, 118.34, 118.28. UV-Vis (chloroform): ꢁmax (nm): [10ꢁ5 " (dm3 molꢁ1 cmꢁ1)]: 245
(4.98), 284 (4.73), 371 (4.66), 617 (4.90), 692 (5.10). MS (FAB), (m/z): 1314 [M þ 1]þ.
3. Results and discussion
The mode of preparation of the metal-free Pc (4) and metallophthalocyanines (5–7)
are shown in scheme 1. Compound 3 was prepared by a base-catalyzed nucleophilic
aromatic nitro displacement of 4-nitrophthalonitrile (2) with 4-phenoxy-phenol (1) [22].
O
1
OH
CN
CN
dry DMF
dry K2CO3
+
O
O
CN
CN
3
N2O
2
DMAE
MW
O
O
O
O
N
N
N
N
N
N
M
N
N
O
O
O
O
4
5
6
7
Compound
M
2H Ni Zn Co
Scheme 1. The synthesis of the metal-free Pc and metallophthalocyanines.

Metallophthalocyanines
865
The reaction was carried out at 50ꢀC in DMF with K2CO3 as the base, and the
yield was 62%. Metal-free Pc (4) was synthesized in n-pentanol in the presence of a few
drops of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as a strong base at reflux under
argon. The metallophthalocyanines (5–7) were obtained from anhydrous metal salts
[NiCl2, CoCl2, and ZnCl2] in 2-(dimethylamino)ethanol by microwave irradiation. We
used a domestic oven synthesis of 5–7 including 350 W, 175ꢀC.
The IR spectrum of 3 confirmed the disappearance of the NO2 band of
4-nitropꢁh1thalonitrile at 1538 cmꢁ1 and appearance of new absorptions at 1090–
1020 cmꢁ1 belonging to ether. In addition, the disappearance of the OH band at
3338 cm gave support for the proposed structure and appearance of CꢂN band at
1
2226 cmꢁ1. H-NMR spectrum of 3 showed new signals at 7.75 (s, 1H, Ar–H), 7.40
(d, 1H, Ar–H), 7.26 (d, 1H, Ar–H), 7.08 (m, 6H, Ar–H), 6.95 (d, 3H, Ar–H) and OH
group of 1 disappeared. The proton-decoupled 13C-NMR spectrum of 3 indicated the
presence of nitrile carbons in 3 at ꢀ ¼ 115 ppm. The mass spectrum of 3, which shows a
peak at m/z ¼ 313 [M þ 1]þ, supports the proposed formula. Elemental analysis
confirmed the proposed structure of 3.
We synthesized metal-free Pc (4) by a classical method, not by microwave irradiation.
Template effect of metal ions plays an important role in formation of some Pcs [23]; 4
shows characteristic peaks for Pcs: 3290 cmꢁ1 is characteristic N–H stretching,
2226 cmꢁ1 (CꢂN) and 1219 cmꢁ1 (Ar–O–C) disappeared in the spectrum of 4.
1
The H-NMR spectrum of 4 [24] indicates aromatic protons at 8.02, 7.75, 7.56, 7.24,
and 7.18 ppm. The MS spectrum of 4 displayed the [M þ Na]þ parent ion peak at
m/z ¼ 1273, confirming the structure. The elemental analysis was satisfactory.
In IR spectra of metallophthalocyanines (5–7) the disappearance of strong CꢂN
stretching vibration of 3 is the evidence for the formation of 5–7. The rest of the IR
spectra of metallophthalocyanines are very similar to those of 4. 1H-NMR spectrum of
2.5
2
1.5
1
0.5
0
200
300
400
500
600
700
800
900
l
Figure 1. UV-Vis spectra of 4 (. . .), 5 (-ꢃ-ꢃ), 6 (- - -), and 7 (—) in chloroform.

866
M.B. K|l|c¸aslan et al.
5–7 are almost identical to those of 4, except for broad signals in 5 and 7,
from aggregation of planar Pcs at the high concentration used for NMR measurements.
1H-NMR measurement of the cobalt(II) Pc (6) was precluded owing to its paramagnetic
nature. The mass spectra of Ni(II), Co(II) and Zn(II) Pcs show molecular ion peaks at
m/z ¼ 1329 [M þ Na]þ, 1308 [M þ 2]þ and 1314 [M þ 1]þ, respectively, confirming the
proposed structures.
In general, Pcs show electronic spectra with two strong absorption regions, one in
the UV region at 300–500 nm related to the B band and the other in the visible region at
600–700 nm related to the Q band [25]. Split Q bands in 4 were observed at 671–708 nm
(figure 1). These Q-band absorptions show monomeric species with D2h symmetry, due
to the Pc ring being fully conjugated 18 ꢃ electron system [26, 27]. The UV-Vis
absorption spectra of 5–7 (figure 1) show intense Q absorption at ꢁmax ¼ 677, 677, and
692 nm, with weaker absorptions at 623, 608, and 617 nm, respectively. Single Q bands
in 5–7 are characteristic for D4h metallophthalocyanines [28]. Soret region B
absorptions of 5–7 were observed at ꢁmax ¼ (242 and 302), (245 and 326), (245, 284,
and 371), respectively.
4. Conclusion
We have prepared metal-free Pc (4) and metallophthalocyanines (5–7) containing
phenoxy groups on peripheral positions. The new dinitrile 3 was obtained from
4-(4-phenoxy-phenoxy) reaction with 4-nitrophthalonitrile in dry DMF under N2.
The metal-free Pc (4) was obtained from the reaction of 3 with n-penthanol and
1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). The new Ni(II), Co(II), and Zn(II)
metallophthalocyanines were prepared by the reaction of 3 with chlorides of Ni(II),
1
Co(II), and Zn(II). The compounds were characterized by elemental analysis and H-,
13C-NMR, IR, UV-Vis, and mass spectroscopies.
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