Phthalocyanines with peripheral azo chromophores

Article abstract of DOI:10.1134/S1070363215100205

Interaction of 4-halogenated phthalonitrile with arylazophenols provided 4-R-azophenoxyphthalonitriles that have been further transformed into tetra-4-(4′-arylazophenoxy)phthalocyanines and their metal complexes. Physicochemical properties of the prepared

Full text of DOI:10.1134/S1070363215100205

ISSN 1070-3632, Russian Journal of General Chemistry, 2015, Vol. 85, No. 10, pp. 2348–2353. © Pleiades Publishing, Ltd., 2015.
Original Russian Text © T.V. Tikhomirova, R.A. Badaukaite, G.P. Shaposhnikov, 2015, published in Zhurnal Obshchei Khimii, 2015, Vol. 85, No. 10,
pp. 1718–1723.
Phthalocyanines with Peripheral Azo Chromophores
T. V. Tikhomirova, R. A. Badaukaite, 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 March 19, 2015
Abstract—Interaction of 4-halogenated phthalonitrile with arylazophenols provided 4-R-azophenoxyphthalo-
nitriles that have been further transformed into tetra-4-(4'-arylazophenoxy)phthalocyanines and their metal
complexes. Physicochemical properties of the prepared compounds were studied.
Keywords: phthalonitrile, phthalocyanine, azo chromophore, electron absorption spectrum, mesomorphism,
thermooxidative decomposition
DOI: 10.1134/S1070363215100205
Phthalocyanine (Pc) and its numerous derivatives
have been intensively studied since 1930s. The interest
to these compounds is due to their unique structure and
the set of physicochemical properties [1, 2].
corresponding diazonium salts that were subjected to
the in situ azocoupling with p-hydroxybenzoic acid in
the alkaline medium. The nucleophilic substitution of
the halogen atom in the 4-halogenated phthalonitrile
with the azo dye fragment (Хр) via the known method
[9] gave the corresponding 4-arylazophenoxyphthalo-
nitriles 3a–3d [10–12]. The purity and the structure of
the products was confirmed by means of chromato–
Chromophore system of phthalocyanines is charac-
terized by a closed conjugation system including the
16-membered heterocycle of carbon and nitrogen
atoms, resulting in deep blue color of the compounds.
The narrow color spectrum of phthalocyanine is
among the disadvantages of these unique compounds.
In view of this, the studies aiming to extend the range
of light absorption by compounds of the phthalo-
cyanines family are of high importance. One of the
possible approaches is the introduction of the
substituents containing a proper chromophore system
to the phthalocyanine molecules. The resulting com-
pounds have been recognized as promising dyes,
materials for solar energetics, microelectronics, and
other related applications [3, 4].
1
mass spectrometry as well as by H NMR, IR, and
electron absorption spectroscopy.
The prepared phthalonitriles 3a–3d were yellow or
red-orange powders, readily soluble in organic
solvents (acetone, DMF, and ethanol); the presence of
sulfo group in the aryl fragment of compound 3d
imparted the solubility in water.
The nature of the substituent in the phthalonitrile
molecule affected the melting point of the substance.
In particular, 4-[4'-(4''-methylphenyl)azophenoxy]phthalo-
nitrile 3a started melting at 140°C; the introduction of
an additional methyl group at the p-toluidine fragment
significantly reduced the melting point of 4-[4'-(2'',4''-
dimethylphenyl)azophenoxy]phthalonitrile 3b to 43°C.
The substitution of the methyl group in the p-toluidine
fragment with acylamino group (3c) or naphthyl-
sulfonic acid moiety (3d) resulted to the less prominent
reduction of the melting point: to 108 and 120–125°C,
respectively (Scheme 1).
Here we report on the synthesis and the study of
hybrid phthalocyanines containing the chemically
linked phthalocyanine and azo chromophores; such
compounds have been poorly discussed in the
literature so far [5–7].
The nitrile route is among the efficient approaches
to the preparation of substituted phthalocyanines [8].
In this work we used substituted nitriles as precursors
of phthalocyanines. In particular, the diazotization of
aryl-substituted aromatic amines 1a–1d yielded the
Heating of the prepared phthalonitrile 3a–3d
following the procedure described in [13] resulted in
2348

2349
PHTHALOCYANINES WITH PERIPHERAL AZO CHROMOPHORES
Scheme 1.
HO
COOH
NaOH
NaNO2, 2HCl
+
NCl−
R N
R
N
R
NH2
ONa
N
1а−1d
NC
X
, K2CO3, DMF
Xp
NC
NC
O
NC
HCl
R
N
OH
N
2а−2d
3а−3d
CH3 (b),
N R;
R =
X = Cl, Br; Xp =
N
O
CH3 (а),
H3C
NHCOCH3 (c),
SO3H (d).
Scheme 2.
XpO
OXp
N
M
N
N
N
N
N
NC
NC
OXp
N
N
3
XpO
OXp
MPc(OXp)4
Xp = O
R = 4-CH3C6H4 (а), 2,4-(CH3)2C6H3 (b), 4-NHCOCH3C6H4 (c), 5-SO3HNaph (d).
N R, M = 2H (4а−4d), Co (5а−5d), Cu (6а−6c), Ni (7а−7c);
N
the corresponding tetra-4-(4'-arylazophenoxy)phthalo-
cyanines 4a–4d [10–12].
sulfo-containing substrates as well [13]; however, it
has not been explained so far.
The metal complexes 5–7 were prepared via the
interaction of phthalonitriles 3a–3d with chlorides of
cobalt, copper, or nickel at 185–190°C (see Scheme 2).
In the case of the sulfo-containing phthalonitrile 3d,
only the cobalt complex 5d was prepared, the copper
and nickel complexes formed in trace amounts. A
similar trend has been earlier observed for the other
All prepared compounds 4–7 were soluble in DMF;
due to the presence of methyl groups, compounds 4–
7a, 7b were soluble in chloroform, whereas the
acylamino groups of compounds 4–7c enhanced their
solubility in acetone, and compounds 4–5d were
soluble in DMSO and aqueous alkali solutions due to
the presence of sulfo groups.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 85 No. 10 2015

2350
TIKHOMIROVA et al.
(b)
U, μV
(a)
100 200 300 400 500 600 700
100 200
300 400
500
600 700
T, °C
T, °C
Fig. 1. Derivatogram of nickel tetra-4-[4'-(4''-methylphenylazo)phenoxy]phthalicyaninate 7a. (a) TG and (b) DTG.
The prepared phthalocyanines were identified using
the data of elemental analysis as well as IR, H NMR,
multi-stage decomposition, as documented in the DTA
traces (see the representative example in Fig. 1).
1
and electron absorption spectroscopy.
In all cases, the heating at 350–590°C was
accompanies with the loss of 65–70% of the mass,
corresponding to the degradation of the phthalocyanine
macrocycle. The highest thermal stability was ob-
served in the case of cobalt tetra-4-[4'-(5''-sulfo-
naphthyl)azophenoxy]phthalocyaninate 5d (Table 1).
IR spectra of the synthesized phthalocyanines 4–7
contained the absorption bands characteristic of the
aryloxy, methoxy, sulfo, and azo groups. Spectra of the
sulfo-derivatives are less resolved as is typical of the
sulfonic derivatives of phthalocyanine [1]. On top of
that, IR spectra of the metal-free phthalocyanines 4a–
4c contained absorption band at 1008 cm–1, typical of
the metal-free phthalocyanines [14].
Depending on the nature of the complex forming
ion, the stability of the tetra-4-[4'-(4''-methylphenyl)-
azophenoxy]phthalocyanines 5–7a decreased in the
Cu > Ni > Co series (Table 1). It is known that the
metal–nitrogen covalent bonds in nickel and cobalt
phthalocyaninates are weaker than in the correspond-
ing copper complexes [15]. This is likely the reason of
the lower thermal stability of the nickel 7a and cobalt
5a complexes than that of the copper one 6a.
Basic parameters of thermooxidative decomposi-
tion of the studied compounds are summarized in
Table 1. The behavior of phthalocyanines 4a–7a, and
5d was similar. Their heating in air up to 200°C
resulted in slight (1–3%) mass loss corresponding to
elimination of residual solvent; that was confirmed by
the identity of IR spectra of the initial specimens and
those annealed at 200°C. Further heating resulted in a
Electron absorption spectra of solutions of the tetra-
4-(4'-arylazophenoxy)phthalocyanines 4–7 in organic
solvents contained a doublet in the long-wavelength
range, typical of the metal-free compounds and
corresponding to the D2h molecule symmetry [15].
Furthermore, all spectra contained a strong absorption
band at 325–367 nm assigned to electronic transitions
in the chromophore system of the azo dye linked to
benzene rings of the phthalocyanine ligand (Table 2).
Since the azo chromophore was not conjugated with
the Рс macrocycle, the green color of the compounds
was due to the combination of the absorptions from the
phthalocyanine (blue) and the azo (yellow) chromo-
phores separated by the oxygen spacer.
Table 1. Parameters of thermooxidative decomposition of
the prepared phthalocyanines 4–7
Comp. Temperature of the
Temperature of the
no.
fastest mass loss, °C highest exothermic effect, °C
4а
5а
5d
6а
7а
400–555
360–530
355–590
390–505
380–560
515
425
510
450
445
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 85 No. 10 2015

2351
PHTHALOCYANINES WITH PERIPHERAL AZO CHROMOPHORES
Table 2. Absorbance bands in electronic spectra of phthalocyanines 4–7
λmax, nm (Irel)
Comp.
no.
0.5 wt% NaOH
chloroform
DMF
conc. H2SO4
in water
а
4а 345 (1.00), 702 (0.71), 666 349 (1.00), 698 (0.67), 670 (0.60),
468 (1.00), 891 (0,55), 836
(0.54)
(0.63), 641 (0.31) 607
(0.21)
641 (0,40), 610 (0.29)
а
а
4b 350 (1.00), 700 (0.92), 665 359 (1.00), 697 (0.76), 669 (0.72),
475 (1.00), 901 (0.60), 841
(0.57),
(0.82), 640 (0.34), 605
637 (0.41), 605 (0.28)
(0.29)
а
4c
366 (1.00), 700 (0.62), 669 (0.60),
635 (0.41), 610 (0.29)
470 (1.00), 873 (0.76), 817
(0.66), 767 (0.48)
а
4d
672 (1.00), 698 (0.98), 325 (0.97),
645 sh (0.63)
622
524(1.00), 825(0.69)
472 (1.00), 818; (0.58)
479 (1.00), 824; (0.44)
а
5а 341 (1.00), 674 (0.66), 613 345 (1.00), 666 (0.59), 603 (0.22)
(0.35)
а
а
5b 345 (1.00), 675 (0.65), 610 345 (1.00), 670 (0.65), 605; (0.21)
(0.29)
а
5c
365 (1.00), 667 (0.79), 605; (0.24)
472(1.00), 802 (0.75), 710 (0.43)
а
5d
666 (1.00), 325 (0.98), 600 sh
(0.27)
628(1.00), 675 811(1.00), 524(0.52)
(0.88)
а
6а 345 (1.00), 680 (0.65), 605 345 (1.00), 675 (0.55), 610 (0.21)
470 (1.00), 839 (0.82), 740 (0.35)
(0.25)
а
6b 344 (1.00), 681 (0.80) 615 355 (1.00), 675.5 (0.71), 610
476 (1.00), 846 (0.88), 740 (0.39)
(0.31)
(0.52)
а
а
а
6c
365 (1.00), 675(0.71), 610 (0.26)
470 (1.00), 824 (0.72), 725 (0.20)
470 (1.00), 814 (0.78), 722 (0.26)
7а 351 (1.00), 672 (0.77), 616 344 (1.00), 673 (0.52), 622 (0.45)
(0.26)
а
а
7b 340 (1.00), 675 (0.78), 610 363 (1.00), 673 (0.40),622; (0.30)
480 (1.00), 821 (0.71), 727 (0.25)
470 (1.00), 800 (0.84), 705 (0.32)
(0.40)
а
7c
350 (1.00), 677 (0.70), 610 (0.31)
a Insoluble.
As compared to the metal-free phthalocyanines,
When chloroform was used as solvent instead of
DMF, the intensities of the major Q band and that in
the range of the vibrational satellite were changed, the
latter becoming stronger (Fig. 2, Table 2). The spectral
changes were likely due to the different tendency of Рс
to associate depending on the solvent polarity [16].
Association of the Со(II) complexes was weaker as
compared to the similar complexes of Cu(II) and
Ni(II), due to the stronger coordinating properties of
cobalt ions. The cobalt phthalocyanines 5a–5d formed
their metal complexes 5–7 exhibited the higher mole-
cular symmetry (D2h and D4h, respectively); therefore,
the two components of the Q band in the electron
absorption spectra were merged [15], the resulting
band being shifted to longer wavelength as compared
to the Q band of the corresponding unsubstituted metal
phthalocyaninate (Table 2). Noteworthily, the azo
chromophore nature had practically no effect on the
position of the long-wavelength absorption band.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 85 No. 10 2015

2352
TIKHOMIROVA et al.
[11]. Lyotropic properties were observed in all
D
organosoluble compounds in the binary systems with a
series of solvents (chloroform, toluene, and DMF),
whereas compounds 4b and 6b were amphotropic
discotics [11].
To conclude, the prepared phthalocyanines can be
applicable as organosoluble dyes for waxes, hydro-
carbons, and polymers; the sulfo-containing com-
pounds can be used for green or green-blue coloring of
protein and cellulose fibers [17–20].
EXPERIMENTAL
λ, nm
4-Arylazophenoxyphthalonitriles 3a–3d and the
corresponding substituted phthalocyanines 4–7 were
prepared and purified as described elsewhere [10–12,
17–20].
Fig. 2. Electronic absorption spectra of the complex 6b in
(1) chloroform and (2) in DMF.
Thermogravimetry studies were performed at the
heating rate of 5 deg/min using a setup with a 1000D
derivatograph as measuring unit. The scheme and the
principle of the setup operation as well as the details of
the data processing have been described earlier [21].
the extraligand complexes with the solvent molecules,
hindering the intermolecular interactions [16].
The same change of the solvent from DMF to
chloroform resulted in the shift of the long-wavelength
absorption band towards longer wavelength in all
phthalocyanines excluding the nickel complexes
(Table 2).
Electron absorption spectra of solutions of the
studied compounds (10–4–10–6 mol/L) were recorded
using a Hitachi U-2001 spectrophotometer (250–900 nm,
room temperature). IR spectra (KBr pellets) were
recorded using an Avatar 360 FT–IR ESP spectrometer
Sulfo groups present in the phthalocyanines 4–5d
provided for their solubility in aqueous alkaline media.
When the 0.5 wt % NaOH aqueous solution was used
as solvent instead of the organic ones, the long-
wavelength absorption bands of the complexes were
shifted towards shorter wavelength, due to the
enhanced molecules association.
1
at 400–4000 nm–1. Н NMR spectra (CDCl3) were
registered using a Bruker DRX-500 instrument.
Elemental analysis was performed using a FlashEA
1112 CHNS–O Analyzer instrument.
ACKNOWLEDGMENTS
All the absorption bands in the spectra of the studied
phthalocyanines dissolved in concentrated sulfuric acid
exhibited the red shift as compared to the spectra in
other solvents, due to protonation of the meso nitrogen
atom in the macrocycle [15]. The shifts observed in
this work were smaller as compared to the cases of
unsubstituted phthalocyanines [1]. That was likely due
to the participation of nitrogen atom of the acylamino
and azo groups accompanied by the reduced degree of
protonation of the meso nitrogen atoms.
This work was carried out in the frame of the
governmental contract of the Ministry of Education
and Science of Russian Federation (“Synthesis and
Study of Physicochemical Properties of 4-Arylazo-
phenoxyphthalonitriles”) and with financial support
from the Russian Scientific Foundation [contract no.
14-23-00204 “Synthesis and Study of Physicochemical
Properties of Tetra-4-(4'-arylazophenoxy)phthalonitriles”].
The study of the synthesized tetraarylazophenoxy-
phthalocyanines 4 and their copper complexes 6 by
means of polarization microscopy revealed the
thermotropic mesomorphism only in the cases of tetra-
4-[4'-(2'',4''-dimethylphenyl)azophenoxy]phthalocyanine
4b and its copper complex 6b, the metal-free com-
pound forming the mesophase at lower temperature
REFERENCES
1. Shaposhnikov, G.P., Kulinich, V.P., and Maizlish, V.E.
Modifitsirovannye ftalotsianiny
analogi (Modified Phthalocyanines and Their Structural
Analogues), Moscow: URSS, 2012.
i
ikh strukturnye
2. The Porphyrin Handbook, Kadish, K.M., Smith, K.M.,
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 85 No. 10 2015

2353
PHTHALOCYANINES WITH PERIPHERAL AZO CHROMOPHORES
and Guilard, R., Eds., New York: Academic Press,
2003, vol. 15.
3. Simon, J. and André, J.-J., Molecular Semicon-
ductors: Photoelectrical Properties and Solar Cells,
Springer, 1985.
ikh Prakticheskoe Ispol’zovanie, 2011, no. 3 (37), p. 15.
12. Tikhomirova, T.V., Badaukaite, R.A., Kulinich, V.P.,
and Shaposhnikov, G.P., Russ. J. Gen. Chem., 2013,
vol. 83, no. 1, p. 116. DOI: 10.1134/S1070363213010209.
13. Kulinich, V.P., Shaposhnikov, G.P., and Badaukaite, R.A.,
4. Liu, Y., Lin, H., Li, X., Li, J., and Nan, H., Inorg.
Chem. Commun., 2010, vol. 13, no. 1, p. 187. DOI:
10.1016/j.inoche.2009. 11.012.
5. Stepanov, B.I., Vvedenie v khimiyu i tekhnologiyu
organicheskikh krasitelei (Introduction to the Chemistry
and Technology of Organic Dyes), Moscow: Khimiya,
1984.
6. Atsay, A., Ozceşmeci, I., Okur, A.I., and Gul, A.,
J. Porphyrins Phthalocyanines, 2008, vol. 12, nos. 3–6,
p. 451. DOI: 10.1142/S1088424608000194.
Makrogeterotsikly, 2010, vol. 3, no. 1, p. 23.
14. Sidorov, A.N. and Kotlyar, I.P., Optika i Spektr., 1961,
vol. 11, no. 2, p. 175.
15. Berezin, B.D., Koordinatsionnye soedineniya porfirinov
i ftalotsianinov (Coordination Compounds of Por-
phyrins and Phthalocyanines), Moscow: Nauka, 1978.
16. Terenin, A.R., Fotonika molekul krasitelei i rodstven-
nykh soedinenii (Photonics of Dye Molecules and
Related Compounds), Leningrad: Nauka, 1967.
17. Tihomirova, T.V., Badaukaite, R.A., Kulinich, V.P., and
Shaposhnikov, G.P., RF Patent 2459846, 2012, Byull.
Izobret., 2012, no. 24.
7. Selivanova, G.A., Amosov, E.V., Vasil’ev, V.G.,
Luk’yanets, E.A., and Shteingarts, V.D., RF Patent
2479573, 2013, Byull. Izobret., 2013, no. 11.
18. Tihomirova, T.V., Badaukaite, R.A., Kulinich, V.P., and
Shaposhnikov, G.P., RF Patent 2454418, 2013, Byull.
Izobret., 2012, no. 18.
8. Shaposhnikov, G.P., Maiyzlish, V.E., and Kulinich, V.P.,
Russ. J. Gen. Chem., 2005, vol. 75, no. 11, p. 1830.
DOI: 10.1007/s11176-005-0519-0.
19. Tihomirova, T.V., Badaukaite, R.A., Kulinich, V.P., and
Shaposhnikov, G.P., RF Patent 2440353, 2012, Byull.
Izobret., 2012, no. 2.
9. Shaposhnikov, G.P. and Maiyzlish, V.E., Izv. Vuzov,
Ser. Khim. i Khim. Tekhnol., 2004, vol. 47, no. 5, p. 26.
10. Tikhomirova, T.V., Badaukaite, R.A., Kulinich, V.P.,
and Shaposhnikov, G.P., Russ. J. Gen. Chem., 2011,
vol. 81, no. 11, p. 2355. DOI: 10.1134/
S1070363211110235.
20. Tihomirova, T.V., Badaukaite, R.A., Kulinich, V.P., and
Shaposhnikov, G.P., RF Patent 2440335, 2012, Byull.
Izobret., 2012, no. 2.
11. Tikhomirova, T.V., Badaukaite, R.A., Kulinich, V.P.,
Shaposhnikov, G.P., Zharnikova, N.V., Anan’eva, G.A.,
Bykova, V.V., and Usol’tseva, N.V., Zhidkie Kristally i
21. Lebedeva, N.Sh., Yakubov, S.P., Kinchin, A.N., and
Vyugin, A.I., Russ. J. Phys. Chem. (A), 2005, vol. 79,
no. 5, p. 827.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 85 No. 10 2015