Synthesis and spectral properties of unsymmetrical phthalocyanines from 3,6-dioctyloxyphthalonitrile and 3,4,5,6-Tetrachlorophthalonitrile

Article abstract of DOI:10.1134/S1070363212100179

The random condensation of 3,6-dioctyloxyphthalonitrile (component A) with 3,4,5,6-tetrachlorophthalonitrile (component B) results in unsymmetrical phthalocyanines of A₃B, ABAB, and AABB types. Their spectral properties were studied. Pleiades Publishing, Ltd., 2012.

Full text of DOI:10.1134/S1070363212100179

ISSN 1070-3632, Russian Journal of General Chemistry, 2012, Vol. 82, No. 10, pp. 1734–1739. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © N.E. Galanin, G.P. Shaposhnikov, 2012, published in Zhurnal Obshchei Khimii, 2012, Vol. 82, No. 10, pp. 1736–1741.
Synthesis and Spectral Properties of Unsymmetrical
Phthalocyanines from 3,6-Dioctyloxyphthalonitrile
and 3,4,5,6-Tetrachlorophthalonitrile
N. E. Galanin and G. P. Shaposhnikov
Ivanovo State Chemical-Technological University, pr. F. Engel’sa 7, Ivanovo, 153000 Russia
e-mail: nik-galanin@yandex.ru
Received July 28, 2011
Abstract—The random condensation of 3,6-dioctyloxyphthalonitrile (component А) with 3,4,5,6-tetrachloro-
phthalonitrile (component В) results in unsymmetrical phthalocyanines of А3В, АВАВ, and ААВВ types.
Their spectral properties were studied.
DOI: 10.1134/S1070363212100179
Scheme 1.
The unsymmetrically substituted phthalocyanines
and porphyrazines are very interesting compounds.
When the molecule contains both electron-releasing
and electron-withdrawing substituents, they have a
polarized electronic structure [1] and are promising for
the use in optics [2, 3]. Moreover, the phthalocyanines
containing bulky alkyl or alkoxy substituents often
exhibit the liquid crystal properties [4–6]. The features
of the molecular and electronic structures of the
unsymmetrically substituted phthalocyanines provide a
possibility of their use in the nanotechnology. [7]
This work reports the data on the synthesis of
unsymmetrical phthalocyanines containing both strong
electron-releasing and electron-withdrawing substi-
tuents, and on their spectral properties.
The random condensation of two differently
substituted phthalonitriles A and B [8, 9] is the most
frequent method of the synthesis of similar com-
pounds. In this work, 3,6-dioctyloxyphthalonitrile I
and 3,4,5,6-tetrachlorophthalonitrile II were used as
components A and B, respectively.
OC8H17
CN
OH
CN
CN
K2CO3
+ C8H17Br
CN
OC8H17
OH
III
I
and acetone. Its composition and structure were
1
confirmed by the elemental analysis data, IR and H
NMR spectroscopy, and mass spectrometry.
In the IR spectrum of I there are absorption bands
at 3087 and 2919 cm–1 originating from the C–H bonds
vibrations in the aryl and alkyl substituents, respec-
tively. The absorption band at 2224 cm–1 belongs to
the cyano groups vibrations. The absorption bands at
1198 and 1078 cm–1 indicate the presence of the C–O–C
fragment. The 1H NMR spectrum of nitrile I contains a
singlet at 7.17 ppm corresponding to the resonance of
two aromatic protons. A triplet at 4.08–4.04 ppm
belongs to four α-protons of the alkyl groups; four β-
protons, and four γ-protons resonate as two triplets at
1.86–1.82 and 1.50–1.46 ppm, respectively. A multi-
plet at 1.32–1.25 ppm corresponds to the proton
resonance of sixteen terminal methylene groups. Six
methyl protons resonate as a triplet at 0.90–0.87 ppm.
The EI mass spectrum of nitrile I contains the
following signals, m/z: 384 [M]+, 357 [M – HCN]+,
255 [M – OC8H17]+, 126 [M – 2OC8H17]+.
We have chosen compound I due to the presence of
two bulky alkoxy substituents in its molecule resulting
in significant steric hindrances for the symmetrical
octaoctyloxyphthalocyanine formation that increases
the reaction selectivity. Nitrile I was obtained by the
alkylation of 3,6-dihydroxyphthalonitrile III with 1-
bromooctane in DMF in the presence of K2CO3
(Scheme 1).
Compound I is a light-gray powder soluble in
benzene and chloroform and sparingly soluble in DMF
1734

SYNTHESIS AND SPECTRAL PROPERTIES OF UNSYMMETRICAL PHTHALOCYANINES
1735
Scheme 2.
H17C8O
OC8H
OC8H17
17 N
N
Cl
Cl
(1) H13C6OLi, H13C6OH
(2) MeCO2H
N
N
Cl
Cl
CN
CN
Cl
Cl
I +
NH
HN
N
N
Cl
II
OC8H17
Cl
H17C8O
OC8H17
IV
Cl
Cl
Cl
Cl
H17C8O
OC8H17
Cl
OC8H
OC8H
17N
NH
N
17 N
NH
N
OC8H17
N
N
N
N
Cl
Cl
HN
+
+
HN
N
N
N
N
OC8H17
OC8H17
OC8H17
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
V
VI
Cl
Cl
H17C8O
Cl
OC8H17
Cl
Cl
Cl
Cl
Cl
Cl
N
N
N
N
N
N
N
N
Cl
Cl Cl
+
Cl Cl
Cl
Cl
NH
NH
+
HN
HN
Cl
N
N
N
N
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
VIII
VII
The heating of a mixture of nitriles I and II in a
molar ratio of 3:1 in the boiling 1-hexanol in the
presence of lithium 1-hexanolate followed by the treat-
ment with acetic acid results in a mixture of phthalo-
cyanines IV–VIII. 1,4,8,11,15,18-Hexaoctyloxy-22,23,-
24,25-tetrachlorpphthalocyanine IV (A3B), 1,4,15,18-
tetraoctyloxy-8,9,10,11,22,23,24,25-octachlorophthalo-
cyanine V (ABAB) and 1,4,8,11-tetraoctyloxy-15,16,17,-
18,22,23,24,25-octachlorophthalocyanine VI (AABB)
were isolated by the column chromatography (Scheme 2).
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 82 No. 10 2012

1736
GALANIN, SHAPOSHNIKOV
plet at 1.30–1.27 ppm. A triplet at 0.89–0.87 ppm
D
belongs to 18 methyl protons. Two protons of the
intracyclic imino groups are registered as a broad
singlet at 1.06 ppm.
In the 1H NMR spectra of compounds V and VI the
signal of the intramolecular imino groups is shifted
upfield to 0.10 and 0.41 ppm, respectively. This fact
indicates a somewhat more planar molecular structure
of compounds V and VI. The cis-isomer VI is slightly
more distorted than the trans-isomer V.
In the 1H NMR spectra of compounds V and VI the
signals are broadened at the sample solutions
concentrations of 1×10–3 M. When the solutions were
diluted 10 times, the signals become more pronounced.
These spectral changes are known [10] to appear in the
case of compounds, which tend to associate in a
solution. We believe that compounds V and VI have
the significantly greater dipole moments than IV.
Therefore, the main reason of their association in
organic solvents is the dipole-dipole interaction.
λ, nm
Fig. 1. Electronic spectra of compound IV in (1) CHCl3
and (2) [CHCl3 + 10% NHEt2].
As expected, octyloxyphthalocyanine (A4) did not
form under these experimental conditions. The phthalo-
cyanines VII and VIII cannot be chromatographically
isolated owing to a poor solubility in organic solvents.
The electron absorption spectra of phthalocyanines
IV–VI are characterized by an intense absorption
corresponding to the π–π*-transitions in the visible (Q-
band) and UV range (B-band).
The composition and structure of compounds IV–
VI were confirmed by the elemental analysis data, IR,
1 H NMR, and electronic spectroscopy.
In the electron absorption spectrum of phthalo-
cyanine IV (A3B) (Fig. 1, curve 1) the long-wave band
is split in two components with the maxima at 733 and
669 nm. The short-wave part of this band contains an
inflection at 706 nm. This character of the spectrum in
the long-wave region is one of the characteristic
features of the A3B type phthalocyanines free of metal.
The most long-wave component of the Q-band is the
band of a charge-transfer from the donor to the
acceptor part of the molecule [11]. In this case the
tetrachlorobenzene fragment plays the acceptor role.
The B-band has a maximum at 353 nm.
Their IR spectra contain some common absorption
bands. Thus, the bands at 3280–3269 cm–1 are assigned
to the N–H bond vibrations of the intracyclic imino
group; a strong absorption band at 2955–2855 cm–1
corresponds to the vibrations of the C–H bonds of
alkyl moieties; the absorption bands at 1498–1465 and
1274–1272 cm–1 belong to the vibrations of the C=C
and C=N bonds in the macrocycle. In the IR spectra
there are also the absorption bands at 1135–1130 (CAr–O),
1060–1056 (CAlk–O), and 757–753 cm–1 (C–Cl).
1
The presence of the electron-withdrawing sub-
stituents in the phthalocyanine molecules leads to an
increase in their acidity [12]. So, the addition of a base
to a solution of compounds IV–VI should result in
changing their electron absorption spectra due to the
dianions formation. Indeed, the addition of 10% of
diethylamine to a solution of IV in chloroform causes
the dianion formation, which is confirmed by the blue
shift of the long-wavelength and short-wavelength
components of a Q-band by 2 and 7 nm and by an
increase in the relative intensity of the band at 697 nm
(Fig. 1, curve 2). The reason for this should be
The H NMR spectra of phthalocyanines IV–VI
contain three groups of signals corresponding to the
resonance of the protons of the benzene rings, alkoxy
substituents and the intracyclic N–H groups. When
going from compound IV to VI the position of the
signals varies slightly. Thus, in the case of the phthalo-
cyanine IV a multiplet at 7.19–7.16 ppm belongs to six
aromatic protons of the isoindole fragment. A multiplet
at 4.17–4.11 ppm corresponds to the resonance of 12
methylene α-protons of six alkoxy substituents; 12 β-
protons resonate as a multiplet at 1.88–1.84 ppm. The
remaining 60 methylene protons give rise to a multi-
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SYNTHESIS AND SPECTRAL PROPERTIES OF UNSYMMETRICAL PHTHALOCYANINES
regarded as an increase in the molecular orbitals
1737
H17C8O
OC8H17
symmetry. The position of a B-band is not changed at
the formation of dianion.
OC8H17
Cl
N
N
In the electronic spectrum of compound V (ABAB)
(Fig. 2, curve 1) the Q-band is split into three
components with maxima at 847, 734, and 667 nm. An
increase in the splitting degree of the Q-band is
characteristic of the trans-isomers of the unsym-
metrical phthalocyanines. According to the four-orbital
Gouterman model [13] this is caused by the removal of
the degeneracy of two lowest π*-molecular orbitals. In
the spectrum of the dianion of V (Fig. 2, curve 2) the
Q-band suffers a red shift. Its short-wave component is
shifted to 692 nm. The band at 734 nm is shifted to
758 nm with a simultaneous decrease in its relative
intensity. The long-wave component is shifted to 853 nm.
As in the case of phthalocyanine IV, the formation of
the dianion of V does not significantly change the
position of the B-band.
As would be expected, the electronic spectrum of
phthalocyanine VI (AABB) (Fig. 3, curve 1) contains
only two components of the Q-band with maxima at
737 and 667 nm. These bands are in the same areas as
in the spectrum of compound V. However, if the
spectrum of the latter contains the strongest band at
667 nm, in the spectrum of phthalocyanine VI the band
with a maximum at 737 nm is the strongest. In the
spectrum of the dianion of compound VI (Fig. 3, curve 2)
the long-wavelength component of the Q-band under-
goes a blue shifting to 691 nm, i.e., by 45 nm. Its long-
wave part contains an inflection at 759 nm.
N
Cl
Cl
Cu
N
N
N
N
N
OC8H17
Cl
Cl
Cl
Cl
Cl
X
The electron absorption spectrum of the metal
complex IX (Fig. 4, curve 1) contains two components
of the Q-band with the maxima at 740 and 662 nm. In
the case of compound X (Fig. 4, curve 2), there is no
splitting of the Q-band with a maximum at 658 nm.
This change in the spectrum is due to an increase in the
symmetry of the occupied molecular orbitals as a result
of replacing two intracycle hydrogen atoms with the
copper cations.
In the electron absorption spectra of phthalocya-
nines V and VI and their complexes IX and X there is
a noticeable bands broadening, which confirms the
assumption made earlier on the association of the
synthesized phthalocyanines in a solution owing to the
dipole–dipole interaction.
EXPERIMENTAL
The electron absorption spectra were measured on a
Hitachi UV-2001 spectrophotometer. The IR spectra
To study the effect of the complexation on the
spectral properties of phthalocyanines V and VI, we
synthesized their complexes IX and X, respectively, by
the reaction with copper acetate in a DMF solution.
D
Cl
Cl
Cl
OC8H17
Cl
OC8H17
OC8H17
N
N
N
Cu
N
N
N
N
N
OC8H17
Cl
Cl
λ, nm
Fig. 2. Electronic spectra of compound V in (1) CHCl3 and
(2) [CHCl3 + 10% NHEt2].
Cl
Cl
IX
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 82 No. 10 2012

1738
GALANIN, SHAPOSHNIKOV
D
D
λ, nm
λ, nm
Fig. 3. Electronic spectra of compound VI in (1) CHCl3
and (2) [CHCl3 + 10% NHEt2].
Fig. 4. Electronic spectra of compounds (1) IX and (2) X in
CHCl3.
were recorded on an Avatar 360 FT-IR spectrophoto-
meter in the range of 400–4000 cm–1 from thin films
on a TlI glass. The 1H NMR spectra were registered on
a Bruker Avance- 500 instrument using CDCl3 as a
solvent. The mass spectra were taken on a Varian
Saturn 2000R GC-mass spectrometer. The elemental
analysis was performed on a Flash EA 1112 CHNS-O
analyzer.
by dissolving 0.1 g of lithium in 20 ml of anhydrous
1-hexanol, were added 0.8 g (2.1 mmol) of compound
I and 0.18 g (0.7 mmol) of compound II. After 4 h, the
reaction mixture was cooled and mixed with 50 ml of
acetone and 5 ml of acetic acid. The precipitate was
filtered off, washed with 50 ml of acetone, and dried.
The residue was dissolved in chloroform and
chromatographed on a column filled with aluminum
oxide of II grade activity eluting with a chloroform–
acetone mixture (100:1). The phthalocyanines IV–V
were isolated.
3,4,5,6-Tetrachlorphthalonitrile II (98%) and 3,6-
dihydroxyphthalonitrile III (98%) were purchased
from Aldrich and used without further purification.
1,4,8,11,15,18-Hexaoctyloxy-22,23,24,25-tetra-
chlorophthalocyanine (IV) (A3B). Yield 0.12 g
(12%), green waxy substance, well soluble in benzene
and chloroform, poorly soluble in acetone. Electron
absorption spectrum, λmax, nm (D/Dmax): in CHCl3, 733
(1.00), 706 pl, 669 (0.58), 353 (0.52); in [CHCl3 +
10% NHEt2], 731 (0.93), 697 (1.00), 662 (0.74), 355
(0.61). IR spectrum, ν, cm–1: 3275, 2954, 2922, 2860,
3,6-Dioctyloxyphthtalonitrile (I). A mixture of 2.0 g
(12.5 mmol) of 3,6-dihydroxyphthtalodinitrile III,
5.3 g (27.5 mmol) of 1-bromooctane, 6.9 g (50 mmol)
of K2CO3, and 30 ml of DMF was stirred at 130°C for
10 h, then cooled, and diluted with 100 ml of water.
The precipitate was filtered off, washed with 20 ml of
10% HCl solution, 50 ml of water, 20 ml of acetone,
and dried. Yield 4.5 g (94%), pale gray powder,
soluble in benzene, chloroform, slightly soluble in
acetone. IR spectrum, ν, cm–1: 3087, 2919, 2851, 2224,
1
1470, 1273, 1134, 1059, 795, 757. Н spectrum, δ,
ppm: 7.19–7.16 m (6Н), 4.17–4.11 m (12Н), 1.88–1.84
m (12Н), 1.30–1.27 m (60Н), 1.06 s (2Н), 0.89–0.87 t
(18Н). Found, %: С 67.81; Н 7.99; N 9.27.
С80H110Cl4N8О6. Calculated, %: С 67.59; Н 7.80; N
9.98.
1
1496, 1463, 1287, 1199, 1078, 832, 469. H NMR
spectrum, δ, ppm: 7.17 s (2Н), 4.08–4.04 t (4Н), 1.86–
1.82 t (4Н), 1.50–1.46 t (4Н), 1.29 m (16Н), 0.90–0.87
t (6Н). Mass spectrum, m/z (Irel, %): 384 (55) [М]+, 357
(69) [M – HCN]+, 255 (100) [M – OC8H17]+, 126 (72)
[M – 2OC8H17]+. Found, %: С 74.71; H 9.47; N 7.12.
C24H36N2O2. Calculated, %: C 74.96; H 9.44; N 7.28.
1,4,15,18-Tetraoctyloxy-8-,9,10,11,22,23,24,25-
octachlorophthalocyanine (V) (ABAB). Yield 0.13 g
(29%), green waxy substance, well soluble in benzene
and chloroform, poorly soluble in acetone. Electron
absorption spectrum, λmax, nm (D/Dmax): in CHCl3, 847
(0.23) 734 (0.85) 667 (1.00) 351 (0.67); in [CHCl3 +
Condensation of 3,6-dioctyloxyphthalonitrile (I)
with 3,4,5,6-tetrachlorophthalonitrile (II). To a boiling
solution of lithium 1-hexanolate in 1-hexanol, prepared
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 82 No. 10 2012

SYNTHESIS AND SPECTRAL PROPERTIES OF UNSYMMETRICAL PHTHALOCYANINES
1739
10% NHEt2], 853 (0.14), 758 (0.51), 692 (1.00) 350
H 5.48; N 8.19. С64H72Cl8CuN8О4. Calculated, %: C
(0.71). IR spectrum, ν, cm–1: 3269, 2955, 2925, 2855,
56.34, H 5.32; N 8.21.
1
1616, 1498, 1466, 1274, 1130, 1058, 753. Н spec-
1,4,8,11-Tetraoctyloxy-15,16,17,18,22,23,24,25-
octachlorophthalocyaninate (X). Yield 7 mg (66%),
dark violet waxy substance, well soluble in benzene
and chloroform, poorly soluble in acetone. Electron
absorption spectrum, λmax, nm (D/Dmax): 658 (0.77)
360 (1.00). Found, %: C 56.87, H 5.71; N 8.03.
С64H72Cl8CuN8О4. Calculated, %: C 56.34, H 5.32; N
8.21.
trum, δ, ppm: 6.95–6.89 m (4Н), 4.15–4.08 m (8Н),
1.85–1.82 m (8Н), 1.35–1.32 m (40Н), 0.87 m (12Н),
0.10 s (2Н). Found, %: С 59.34; Н 5.84; N 8.39.
С64H74Cl8N8О4. Calculated, %: С 59.00; Н 5.72; N 8.60.
1,4,8,11-Tetraoctylooxy-15,16,17,18,22,23,24,25-
octachlorophthalocyanine (VI) (AABB). Yield 0.11 g
(25%), green waxy substance, well soluble in benzene
and chloroform, poorly soluble in acetone. Electron
absorption spectrum, λmax, nm (D/Dmax): in CHCl3, 737
(1.00) 667 (0.86) 352 (0.71); in [CHCl3 + 10% NHEt2]
759 pl, 691 (1.00) 664 (0.97), 354 (0.79). IR spectrum,
ν, cm–1: 3280, 2956, 2926, 2855, 1465, 1378, 1273,
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cyanines (IX, X). A mixture of 10 mg (0.008 mmol)
of compound V or VI, 25 mg (0.10 mmol) of cop-
per(II) acetate tetrahydrate, and 20 ml of DMF was
heated for 1 h. After cooling, to the reaction mixture
was added 100 ml of water and 20 ml of chloroform.
The organic layer was separated, washed with 20 ml of
water, and dried. The residue was dissolved in benzene
and chromatographed on a column filled with alu-
minum oxide II grade activity eluting with a benzene–
acetone mixture (10:1) and collecting the main violet
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Copper 1,4,15,18-Tetraoctyloxy-8,9,10,11,22,23,-
24,25-octachlorophthalocyaninate (IX). Yield 8 mg
(75%), dark violet waxy substance, well soluble in
benzene and chloroform, poorly soluble in acetone.
The electronic spectrum (CHCl3), λmax, nm (D/Dmax):
740 (0.54) 662 (0.72) 352 (1.00). Found, %: C 56.03,
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