N- and O-acylated phthalocyanines with gallic acid moieties

Article abstract of DOI:10.1134/S1070363216060190

Phthalocyanines containing gallic acid moieties were synthesized and investigated by the method of electron absorption spectroscopy. It was shown that in organic solvents the prepared phthalocyanines exist predominantly in associated form.

Full text of DOI:10.1134/S1070363216060190

ISSN 1070-3632, Russian Journal of General Chemistry, 2016, Vol. 86, No. 6, pp. 1339–1344. © Pleiades Publishing, Ltd., 2016.
Original Russian Text © Т.V. Tikhomirova, V.Е. Maizlish, А.V. Borisov, G.P. Shaposhnikov, 2016, published in Zhurnal Obshchei Khimii, 2016, Vol. 86,
No. 6, pp. 1010–1015.
N- and O-Acylated Phthalocyanines with Gallic Acid Moieties
Т. V. Tikhomirova, V. Е. Maizlish, А. V. Borisov, and G. P. Shaposhnikov
Research Institute of Macroheterocyclic Compounds, Ivanovo State University of Chemistry and Technology,
Sheremetevskii pr. 7, Ivanovo, 153000 Russia
e-mail: tararjkina@mail.ru
Received November 16, 2015
Abstract—Phthalocyanines containing gallic acid moieties were synthesized and investigated by the method of
electron absorption spectroscopy. It was shown that in organic solvents the prepared phthalocyanines exist
predominantly in associated form.
Keywords: acylation, phthalocyanines, electronic absorption spectra, association
DOI: 10.1134/S1070363216060190
Metal complexes of phthalocyanines (MPc) possess
valuable practical properties allowing their use in
various fields of science and engineering [1, 2]. Of
specific interest are phthalocyanine-containing ester
and amide groups possessing enhanced solubility in
organic solvents. Earlier it was shown that copper
complexes of this type could be used as lipid-soluble
dyes [3, 4] and exhibited liquid crystalline properties
[5]. Liquid crystalline materials, which are capable of
hardening to solid without crystallization and with
retention of the mesophase texture, are promising as
materials for electrooptical devices, like electro-
luminescence cells, photogalvanic elements, organic
photoconductors [6]. The use of such compounds
improves the performance characteristics of the cell
material due to to the replacement of the two-
component system “glass forming material–dye” by an
individual compound. It is known that phthalocyanine
derivatives having the ability to glass formation
combine the transparency of the glass layer with the
ability to absorb light in strictly fixed region of
spectrum [6].
Acylation with acyl chlorides can be performed in
aqueous sodium alkali (the Schotten-Baumann
method) or in the presence of an organic base, pyridine
(the Einhorn reaction). We have used the latter method
since in this case pyridine plays the role of both the
solvent and the catalyst of the reaction forming
reactive species of the N-benzoylpyridinium type or
causing a partial ionization of the hydroxy compound
in the case of О-acylation. Besides, this allows to
exclude the hydrolysis of esters or amides, thus
increasing the yield of the target products. By the
aforementioned scheme, the acyloxy- (8) and acyl-
aminophthalonitriles (9) were obtained (Scheme 1).
Phthalonitriles 8, 9 are waxy compounds, insoluble
in water but soluble in organic solvents (acetone, chloro-
form, benzene). The structure of the products was
determined by the elemental analysis, MALDI TOF
mass spectrometry, IR and 1Н NMR spectroscopy.
In the IR spectra of phthalonitriles 8, 9 the band of
stretching vibrations of the nitrile group (2237–
2240 cm–1) is retained and appears the absorption band
of the ester or amide C=O group (1688–1742 cm–1),
C–H (2850–2920 cm–1), and С-O-С bands (1250–
1257 cm–1). In the spectrum of compound 9 the
absorption bands were observed at 3339 and 1614 cm–1
(stretching and bending vibrations of the secondary
amino group) and at 1387 cm–1 (C–N vibrations) [8].
In the present report, we report the data on the
synthesis and investigation of physicochemical pro-
perties of N- and О-acylated phthalocyanines con-
taining the substituted residues of gallic acid.
The presence of electronwithdrawing substituents
(CN, COOH) in the molecules of substrates results in a
decrease in their reactivity in the electrophilic
substitution reaction, so the most suitable reagents for
acylation are substituted benzoyl chlorides [7].
In the second stage the synthesis of metal
complexes was performed using the “nitrile” method,
1339

1340
TIKHOMIROVA et al.
Scheme 1.
HO
HO
SOCl
2
H23C11O
COOH
H23C11O
C
O
Cl + HO
COOH
3
1
2
Py
H23C11O
C
O
H23C11O
C
O
O
O
SOCl
2
HХ
CN
+
COOH
H23C11O
C
O
C
O
Cl
H23C11O
C
O
O
CN
O
6, 7
O
C
O
C
H23C11O
O
H23C11O
O
5
4
Py
H23C11O
C
O
O
CN
1
4
6
5
C
O
Х
CN
H23C11O
C
O
4'
2
6'
5'
3
O
8
O
7
H23C11O
C
O
8'
7'
8, 9
X = O (6, 8), NH (7, 9).
by the reaction of the obtained precursors with metal
salts at 170–175°С (10, 11а, 11b) (Scheme 2).
MALDI TOF mass spectrometry, elemental analysis,
IR and 1Н NMR and electronic spectroscopy.
The physicochemical properties of the obtained
phthalocyanines are determined by the nature of the
functional substituents. Thus, tetra-4-hydroxyphthalo-
cyanines are soluble in aqueous alkali and, moderately,
in DMF, while their analogs with bulky substituents
having the fragments of gallic acid are insoluble in
these media but soluble in organic solvents (chloro-
form, benzene). The N-acylated phthalocyanines retain
the solubility in DMF, like tetra-4-aminophthalo-
cyanines, and they are also soluble in such organic
solvents as chloroform and benzene.
The IR spectra of compounds 10 and 11 have
absorption bands typical of phthalocyanines [9], and
retain the absorption bands of the acyl residues present
in the spectra of the corresponding phthalonitriles.
1
The H NMR spectra of all obtained complexes are
similar and contain the signals of aliphatic protons in
strong field and aromatic protons in weak field. The
signal of the secondary amino group was not observed,
apparently, because of the presence of four substituted
fragments of gallic acid, shielding the bridging groups.
The obtained compounds are dark-green powders.
The structure and composition of the synthesized
phthalocyanines was proved by the methods of
An effect of the nature of the bridging group on the
character and position of absorption bands in the elec-
tron absorption spectra was observed (see the table).
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1341
N- AND O-ACYLATED PHTHALOCYANINES WITH GALLIC ACID MOIETIES
Scheme 2.
O
Х
C
R
N
N
1
3
N
M
N
Х
C
O
R
M(OAc) хH O
2
2
N
N
R
C
O
Х
8, 9
2
N
N
R
C
O
Х
7
8
O
C
O
OC11H23
8'
7'
5
O
6
4
OC11H23
R =
O
C
6'
5'
4'
O
C
7
8
O
OC11H23
X = O (10), NH (11); M = Cu (x = 2) (a), Ni (x = 4) (b).
8'
7'
The electron absorption spectra of N-acylated
phthalocyanines 11а and 11b in chloroform are
characterized by the presence of an intense broadened
absorption band in the range 620–629 nm (see figure
and table). In going to the О-acylated complexes 10а
and 10b, two bands were detected in the longwave
region of the electronic spectrum (see table), their ratio
of intensities being dependent on concentration of the
examined phthalocyanines.
Electron absorption spectra of the synthesized complexes 10, 11
In going from chloroform as a solvent to DMF, the
character of the spectra of 11а and 11b is somewhat
changed. Irrespective of the nature of the complex-
forming metal, two absorption bands are observed in
the ranges 620–622 and 687–691 nm (see figure and
table). On dilution of the solvent, the intensity of the
longwave band decreases to a lesser extent than that of
the shortwave band.
λmax, nm (Drel)а
Comp.
no.
chloroform
DMFb
–
conc. H2SO4
838
10а
10b
11а
11b
619 (0.70),
673 (1.00)
633 (0.52),
665 (1.00)
629
–
722 (0.31),
808 (1.00)
642 (0.42),
764 (1.00)
690 (0.31),
770 (1.00)
623 (0.35),
691 (1.00)
635 (0.65),
687 (1.00)
It is known [10–12] that the association of the
phthalocyanine molecules may occur either by
hydrogen bond formation of peripheral substituents or
due to π–π interactions. In solution both types of
associates may exist.
625
а
Absorption bands intensities are given relative to the most
intense one. b Insoluble.
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1342
TIKHOMIROVA et al.
Different character of the spectra is apparently
D
connected with different propensity of phthalocyanines
to association depending on the polarity of the solvent.
Small dielectric constant of nonpolar and low polar
solvents results in weakening of the effect of shielding
of intermolecular Pc–Pc interaction by the solvent and,
as a result, favors the formation of associates and
increases their stability, as compared to polar solvents
(DMF) [10]. Therefore, the amount of associates
formed by π–π interactions in DMF substantially
decreases and, as a consequence, the intensity of the
short-wave band is lowered.
Going from organic solvents to conc. sulfuric acid
all synthesized phthalocyanines demonstrate
a
significant red shift of absorption bands caused by the
processes of protonation of the nitrogen meso-atoms
[13]. It is shown that in H2SO4 the absorption bands of
the N-acylated complexes suffer a blue shift with
respect to the corresponding О-derivatives (see the
table). The latter effect is explained by the fact that the
protonation first occurs on the nitrogen atoms of
aminogroups. Probably, this lowers the basicity of the
nitrogen meso-atoms and, as a result, decreases the
degree of their protonation.
λ, nm
Electron absorption spectra of complex 11b: (1) in
chloroform and (2) in DMF.
1Н NMR spectra were taken on a Bruker DRX-500
spectrometer from 5% solutions in CDCl3 with TMS as
an internal reference. Elemental analysis was per-
formed on an elemental analyzer CHNS-O FlashEA,
1112 series.
Depending on the nature of the complex-forming
metal, in going from nickel to copper, the red shift of
the absorption bands is observed in all solvents (see
the table).
Investigation of physicochemical characteristics of
the studied compounds was performed in the Center
for Joint Usage of Ivanovo State University of
Chemistry and Technology.
Therefore, using the reaction of acylation of 4-
hydroxy(amino)phthalonitriles with 4-[(3,4,5-tris{unde-
cyloxybenzoyloxy)benzoyl chloride, phthalonitriles
were synthesized. On their basis, the corresponding
metal complexes were obtained and their electron
absorption spectra were investigated. The propensity
of the phthalocyanines molecules to association in
solution was found to increase when replacing the ester
group in the substituent by the amide group, as well as
at going from DMF as a solvent to chloroform.
Synthesis of 4-[(3,4,5-tris{undecyloxybenzoyl-
oxy}benzoyl)oxy]-
and
4-[(3,4,5-tris{undecylo-
xybenzoyloxy}benzoyl)amino]phthalonitriles. Mix-
ture of 1.00 g (3.6 mmol) of 4-undecyloxybenzoic acid
and 0.5 mL (7 mmol) of thionyl chloride was stirred at
50°С for 2 h until evolution of gas bubbles (SO2 and
HCl) ceased, then the excess of thionyl chloride was
distilled off. To the obtained acid chloride, 0.18 g
(1.06 mmol) of gallic acid and 3.0 mL of pyridine were
added. The reaction mixture was kept for 10 h at 80°С,
then poured into water, the formed precipitate was
filtered off and dried. 4-[(3,4,5-Tris{undecyloxy-
benzoyloxy)benzoic acid was extracted with acetone,
the solvent removed, the target product dried. Yield
0.97 g (90 %). IR spectrum, ν, cm–1: 1747 br (C=O),
2918, 2850 (СH), 1700 (СООН). Found, %: C 73.2; H
9.0. C61H84O11. Calculated, %: С 73.8; H 8.5.
EXPERIMENTAL
Electron absorption spectra in DMF, chloroform,
and conc. sulfuric acid (325–900 nm) were recorded
on a HITACHI U-2001 spectrophotometer at room
temperature. IR spectra were recorded from KBr
pellets (400–4000 cm–1) on an Avatar 360 FT-IR ESP
spectrometer. MALDI-TOF mass spectra were ob-
tained on a Shimadzu Biotech Axima Confidence mass
spectrometer in positive and negative ion modes. 2-(4-
Hydroxybenzoazo)benzoic acid was used as a matrix.
To 1.0 g (1 mmol) of 4-[(3,4,5-tris{undecyloxy-
benzoyloxy)benzoic acid 0.28 mL (4 mmol) of thionyl
chloride was added and the reaction mixture was
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 86 No. 6 2016

1343
N- AND O-ACYLATED PHTHALOCYANINES WITH GALLIC ACID MOIETIES
heated to 50°С with stirring, kept for 2 h until
evolution of gas bubbles (SO2 and HCl) ceased, the
excess of thionyl chloride was distilled off. To the
obtained 4-[(3,4,5-tris{undecyloxybenzoyloxy)benzoyl
chloride 0.17 g (1.2 mmol) of 4-hydroxyphthalonitrile
or 0.17 g (1.2 mmol) of 4-aminophthalonitrile and
2.5 mL of pyridine was added. The reaction mixture
was kept at 85°С for 17 h, then poured into water. The
formed viscous mass was filtered and dried. The target
products were isolated by extraction with chloroform.
After removal of the solvent, the nitriles were washed
with the mixture methanol–acetone (4 : 1).
2920, 2850 (СH). Found, %: C 73.2; H 8.0; N 2.3.
C276H344CuN8O44. Calculated, %: С 73.00; H 7.64; N 2.47.
Nickel tetra-4-(4-[(3,4,5-tris{undecyloxybenzoyl-
oxy}benzoyl)oxy])phthalocyanine (10b). Yield 0.90 g
(19.2 %). IR spectrum, ν, cm–1: 1743, 1688 br (C=O),
1
2920, 2850 (СH). Н NMR spectrum, δ, ppm: 8.16 d
(24Н, Н5,5',7,7', J = 8.0 Hz), 7.95 d (8Н, Н4,4', J = 8.4 Hz),
7.49 s (4Н, Н1), 7.38 d (8Н, Н2,3, J = 8.2 Hz), 7.08 d
(24Н, Н6,6',8,8', J = 8.6 Hz), 5.32 t (24Н, ОСН2, J =
7.3 Hz), 1.58–1.62 m (24Н, ОССН2), 1.26–1.30 m
(192Н, other СН2 in С11Н23), 0.84-0.91 m (36Н, СН3).
Mass spectrum, m/z: 4539.66 [M + 3H]+, calculated
М 4536.48. Found, %: C 73.21; H 8.00; N 2.40.
C276H344N8O44Ni. Calculated, %: С 73.07; H 7.64; N 2.47.
4-[(3,4,5-Tris{undecyloxybenzoyloxy}benzoyl)oxy]-
phthalonitrile (8). Yield 0.78 g (70 %). mp 59°С. IR
spectrum, ν, cm–1: 2237 (C≡N), 1743, 1688 br (C=O),
Copper tetra-4-(4-[(3,4,5-tris{undecyloxybenzoyl-
oxy}benzoyl)amino])phthalocyanine (11а). Yield
1.13 g (25.2 %). IR spectrum, ν, cm–1: 2240 (C≡N),
1742 br (C=O), 1671, 3339 (NH), 2920. 2850 (CH),
1256 (C–O–C). Found, %: C 73.40; H 8.01; N 3.52.
1
2920, 2850 (СH). Н NMR spectrum, δ, ppm: 8.02 d
(6Н, Н5,5',7,7', J = 6.4 Hz), 7.67 d (2Н, Н4,4', J = 8.9 Hz),
7.49 s (1Н, Н1), 7.37 d (2Н, Н2,3, J = 8.5 Hz) 7.08 d
(6Н, Н6,6',8,8', J = 8.2 Hz), 3.75 t (6Н, ОСН2, J = 6.9 Hz),
1.66–1.70 m (6Н, ОССН2), 1.26-1.29 m (48Н, other
СН2 in С11Н23), 0.84–0.90 m (9Н, СН3). Mass
spectrum, m/z: 1118.19 [M]-, calculated М 1118.46.
Found, %: C 73.8; H 8.0; N 2.3. C69O11N2H86.
Calculated, %: С 74.0; H 7.7; N 2.5.
C
276H348N12CuO40. Calculated, %: С 73.06; H 7.73; N
3.70.
Nickel tetra-4-(4-[(3,4,5-tris{undecyloxybenzoyl-
oxy}benzoyl)amino])phthalocyanine (11b). Yield
0.99 g (22.0 %). IR spectrum, ν, cm–1: 2240 (C≡N),
1742 br (C=O), 1671, 3339 (NH), 2920, 2850 (CH),
4-[(3,4,5-Tris{undecyloxybenzoyloxy}benzoyl)-
amino]phthalonitrile (9). Yield 0.77 g (69 %). mp
75°С. IR spectrum, ν, cm–1: 2240 (C≡N), 1742 br
(C=O), 1671, 3339 (NH), 2920. 2850 (CH), 1256
1
1256 (C–O–C). Н NMR spectrum, δ, ppm: 8.04 d
(24Н, Н5,5'7,7', J = 8.2 Hz), 7.86 m (4Н, NH), 7.79 d
(8Н, Н4,4', J = 8.5 Hz), 7.49 s (4Н, Н1), 7.38 d (8Н,
Н2,3, J = 7.2 Hz), 6.95 d (24Н, Н6,6',8,8', J = 9.0 Hz),
4.02 t (24Н, ОСН2, J = 7.0 Hz), 1.56-1.62 m (24Н,
ОССН2), 1.26–1.32 m (192Н, other СН2 in С11Н23),
0.84–0.90 m (36Н, СН3). Mass spectrum, m/z: 4554.68
[M + Na]+, calculated М 4532.55. Found, %: C 73.10;
H 8.01; N 3.54. C276H348N12NiO40. Calculated, %: С
73.14; H 7.74; N 3.71.
1
(C–O–C). Н NMR spectrum, δ, ppm: 9.36 s (1Н,
NH), 8.24 d (6Н, Н5,5',7,7', J = 8.2 Hz), 8.06 d (2Н, Н4,4',
J = 8.6 Hz), 7.85 d (2Н, Н2,3, J = 8.3 Hz), 7.49 s (1Н,
Н1), 6.97 d (6Н, Н6,6',8,8', J = 8.0 Hz), 4.04 t (6Н,
ОСН2, J = 7.3 Hz), 1.82–1.86 m (6Н, ОССН2), 1.25-
1.31 m (48Н, other СН2 in С11Н23), 0.84–0.90 m (9Н,
СН3). Mass spectrum, m/z: 1141.46 [M+Na]+, cal-
culated М 1119.45. Found, %: C 73.9; H 8.1; N 3.6.
C69O10N3H87. Calculated, %: С 74.1; H 7.8; N 3.8.
ACKNOWLEDGMENTS
This work was performed within the framework of
the State contract of the Ministry of Education and
Science of Russian Federation “Synthesis and
investigation of physicochemical properties of 4-
[(3,4,5-tris{undecyloxybenziyloxy}benzoyl)oxy-4-
[(3,4,5-tris{undecyloxybenzoyloxy}benzoyl)amino]
phthalonitriles” and with the support from the Russian
Scientific Foundation (project 14-23-00204).
Synthesis of tetra-4-(4’-benzoyl-substituted)hyd-
roxy(amino)phthalocyanines. The mixture of 1 mol
of substituted phthalonitrile 8 or 9 and 0.3 mmol of
copper or nickel acetate salt was thoroughly ground
and kept in quartz ampule at 170–175°С for 2 h. The
melt was thoroughly ground, the target product was
extracted with chloroform and purified by column
chromatography on alumina of the II activity level
(eluent chloroform–methanol, 4 : 1).
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(19.0 %). IR spectrum, ν, cm–1: 1743, 1688 br (C=O),
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