Thermogravimetric and spectral studies of the reaction between benzotriazolyl derivatives of phthalodinitriles and copper(II) acetate

Article abstract of DOI:10.1134/S0036024408110101

The interaction of benzotriazolyl derivatives of phthalodinitriles with copper(II) acetate was studied thermogravimetrically and spectroscopically. Electron acceptor properties of peripheral substituents had a predominant influence on the enthalpy parameter of formation of copper(II)phthalocyanines.

Full text of DOI:10.1134/S0036024408110101

ISSN 0036-0244, Russian Journal of Physical Chemistry A, 2008, Vol. 82, No. 11, pp. 1847–1850. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © N.A. Pavlycheva, N.Sh. Lebedeva, A.I. V’yugin, V.E. Maizlish, G.P. Shaposhnikov, S.A. Znoiko, I.G. Abramov, M.B. Abramova, 2008, published in
Zhurnal Fizicheskoi Khimii, 2008, Vol. 82, No. 11, pp. 2058–2061.
PHYSICAL CHEMISTRY
OF SOLUTIONS
Thermogravimetric and Spectral Studies
of the Reaction between Benzotriazolyl Derivatives
of Phthalodinitriles and Copper(II) Acetate
N. A. Pavlychevaa, N. Sh. Lebedevaa, A. I. V’yugina, V. E. Maizlishb, G. P. Shaposhnikovb,
S. A. Znoikob, I. G. Abramovc, and M. B. Abramovac
a Institute of Solution Chemistry, Russian Academy of Sciences, Ivanovo, Russia
b Ivanovo State University of Chemical Technology, Ivanovo, Russia
c Yaroslavl State Technological University, Yaroslavl, Russia
e-mail: nap@isc-ras.ru
Received June 18, 2007
Abstract—The interaction of benzotriazolyl derivatives of phthalodinitriles with copper(II) acetate was studied
thermogravimetrically and spectroscopically. Electron acceptor properties of peripheral substituents had a pre-
dominant influence on the enthalpy parameter of formation of copper(II)phthalocyanines.
DOI: 10.1134/S0036024408110101
INTRODUCTION
Metal complexes with phthalocyanines offer prom-
ise for practical applications. Their high thermal stabil-
ity, kinetic stability, and chromophore properties are
caused by the presence of a multicircuit conjugated aro-
matic system. The introduction of new substituents
contributes to the appearance of new metallophthalocy-
anine properties and broadens their practical use. It can,
however, decrease their thermal stability. When macro-
cyclic compounds are synthesized from ligsons (ligand
sintons) under traditional conditions (in solution or the
solid state), the rate of the reactions is very low. For this
reason, temperature must be increased to obtain the
desired product in noticeable amounts. The synthesis of
metallophthalocyanines with a complex of desired
properties for the purpose of their use in practice, how-
ever, presupposes the introduction of peripheral substit-
uents of different natures. Thermal action on these sub-
stituents can cause undesirable consequences [1–3].
For this reason, information about the influence of tem-
perature on the template synthesis of metallophthalocy-
anines is necessary.
N
O
N
S
N
N
NC
NC
NC
NC
N
N
Cl
,
,
(I)
(II)
N
O
N
O
N
N
NC
NC
NC
NC
N
N
I
,
,
(III)
(IV)
EXPERIMENTAL
N
N
NC
NC
N
Phthalodinitriles (PhDNs) 4-(1-benzotriazolyl)-5-
(2-naphthoxy)phthalodinitrile (I), 4-(1-benzotriazolyl)-
5-(p-chlorothiaphenyl)phthalodinitrile (II), 4-(1-ben-
zotriazolyl)-5-(p-iodophenoxy)phthalodinitrile (III),
4-(1-benzotriazolyl)-5-(1-naphthoxy)phthalodinitrile
(IV), and 4-(1-benzotriazolyl)-5-(2,6-dichlorophe-
noxy)phthalodinitrile (V),
Cl
O
Cl
(V)
were synthesized and purified as described in [4].
1847

1848
PAVLYCHEVA et al.
Table 1. Thermooxidative destruction of benzotriazolyl
The geometry of the structure of copper(II) phthalo-
cyanines formed in experiments was optimized as rec-
ommended in [7–10]. The geometric parameters were
calculated as relative values on the basis of the structure
of molecules. The structure of molecules was opti-
mized by the molecular mechanics (MM) method using
the HYPER CHEMISTRY program, version 5.02, and
the MM+ force field. The optimization was stopped
when the gradient (total energy change per calculation
step) decreased to 0.01 kcal/mol.
substituted phthalodinitriles
No.
c, wt %
t
t'
t''
I
68.32
20–122
122–196
215
296
II
84.60
80.00
85.00
95.00
22–182
20–193
20–194
20–145
178
250
213
227
264
285
283
274
III
IV
V
Notation: c is the content of PhDN in the solvate and t, t', and t'' are
the temperatures (°C) of desolvation, melting, and destruction,
respectively.
RESULTS AND DISCUSSION
Information about the thermochemical behavior of
the initial reagents, phthalodinitriles and copper(II)
acetate, is necessary for correctly assigning the thermo-
gravimetric (TG), differential thermogravimetric
Copper(II) acetate crystal hydrate of kh. ch. (chem-
ically pure) grade was recrystallized according to [5].
Copper(II) acetate is difficult to dehydrate and store. (DTG), and differential thermal analysis (DTA) ther-
In addition, difficulties can arise with the desolvation of mal effects recorded for mixtures of benzotriazolyl sub-
phthalodinitriles. For this reason, studies of the interac- stituted phthalodinitriles and copper(II) acetate. The
tion of benzotriazolyl substituted phthalodinitriles with pyrolysis of copper acetate was performed in air at a
copper(II) acetate were performed without drying the 5 K/min heating rate. No noticeable changes occurred
initial reagents. The initial molar ratio between the as the sample was heated to a temperature of about
reagents was phthalodinitrile : copper(II) acetate = 1 : 5. ~40°ë. The first stage of destruction (40–154°ë) was
accompanied by a 17% weight loss and endothermic
Thermogravimetric studies were performed on a
DTG and DTA effects. Suppose that water molecules
thermoanalytic unit consisting of a 1000D derivato-
were removed at this change. The recorded weight loss
graph, a program-apparatus complex, and a PC. A
then corresponds to the Cu(CH3COO)2 · 2H2O initial
scheme and principles of thermoanalytic unit opera-
composition. Interestingly, the removal of two water
tion, procedures for measurements and thermogravi-
molecules from zinc(II) acetate dihydrate under similar
metric data processing, and calculations of errors were
conditions occurs in a much narrower temperature
described in detail in [6]. The electronic absorption
interval (53–92°ë).
spectra of reaction products were recorded on a
The thermal oxidation of Cu(CH3COO)2 · 2H2O
begins with the dehydration stage, which ends at
154°ë. Subsequent pyrolysis of copper(II) acetate
occurs in two stages and ends at 400°ë with the forma-
tion of copper(II) oxide. We did not observe sublima-
tion of pyrolysis products containing metal ions. The
generalized data on thermal action on benzotriazolyl
substituted phthalodinitriles in air are listed in Table 1.
We found that phthalodinitriles were fairly stable sub-
stances, which decomposed above 264°ë.
Specord M40 spectrophotometer.
The procedure for calculating the heat effect of
formation of copper(II) phthalocyanines (CuPc) was
as follows. Since the formation of copper(II) phthalocy-
anines and melting of phthalodinitriles occurred at
close temperatures, the thermal effect recorded during
thermoanalytic studies of mixtures of phthalodinitriles
and copper(II) acetate consisted of the thermal exother-
mic effect of the formation of copper(II) phthalocya-
nine and thermal endothermic effect of melting of unre-
acted phthalodinitrile. To refine the contributions of
these processes to the total experimental thermal effect,
reaction products were dissolved in chloroform, and the
yield of copper(II) phthalocyanine was determined
from electronic absorption spectra.
The thermal effects of formation of benzotriazolyl
substituted copper(II) phthalocyanines, copper(II)
4-(1-benzotriazolyl)-5-(2-naphthoxy)phthalocyanine
(I'), copper(II) 4-(1-benzotriazolyl)-5-(p-chlorothi-
aphenyl)phthalocyanine (II'), copper(II) 4-(1-benzotri-
azolyl)-5-(p-iodophenoxy)phthalocyanine (III'), cop-
per(II) 4-(1-benzotriazolyl)-5-(1-naphthoxy)phthalo-
cyanine (IV'), and copper(II) 4-(1-benzotriazolyl)-5-
(2,6-dichlorophenoxy)phthalocyanine (V'), are listed in
Table 2.
The amount of reacted phthalodinitrile was calcu-
lated by the equation
4PhDN + Cu(CH3COO)2
CuPc + 2CH3COOH.
Next, the amount of reacted phthalodinitrile was sub-
Let us consider the interaction of 4-(1-benzotri-
tracted from the amount of phthalodinitrile loaded into azolyl)-5-(1-naphthoxy)phthalocyanine with copper(II)
the thermoanalytic unit. The calibration plot Qm
=
acetate. The differential thermal analysis curves of
f(mPhDN) constructed preliminarily was then used to 4-(1-benzotriazolyl)-5-(1-naphthoxy)phthalodinitrile
determine the contribution of unreacted phthalodini- with copper(II) acetate, copper acetate crystal hydrate,
trile melting to the overall thermal effect.
and 4-(1-benzotriazolyl)-5-(1-naphthoxy)phthalodini-
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THERMOGRAVIMETRIC AND SPECTRAL STUDIES
1849
Table 2. Thermochemical parameters characterizing the
formation of benzotriazolyl substituted copper(II)phthalocy-
anines under thermogravimetric experiment conditions
trile are shown in the figure. The curves have complex
shapes, at the first stage (up to ≈200°ë), the desolva-
tion/dehydration of the initial reagents occurs. Next, a
new peak (208–234°ë) absent in the curves of the ini-
tial reagents appears. Note that the temperature corre-
sponding to this peak coincides with that of melting of
the corresponding nitrile, but the sign of the effect is
opposite. These data lead us to suggest that precisely
this peak corresponds to the formation of copper(II)
4-(1-benzotriazolyl)-5-(1-naphthoxy)phthalocyanine.
To verify this suggestion, a thoroughly ground mixture
of phthalodinitrile with copper(II) acetate (molar ratio
1 : 5) was placed into the thermoanalytic unit and
heated to 234°ë. The product was dissolved in CHCl3.
No.
∆t, °C
–Q, kJ/mol
ϕ, %
I'
208–237
173–200
227–240
208–234
210–228
1.92 × 104
1.84 × 103
1.46 × 104
1.85 × 104
2.07 × 103
4.27
9.20
3.85
9.16
21.35
II'
III'
IV'
V'
Notation: ∆t is the temperature interval of the formation of CuPc,
Q is the heat effect, and ϕ is the yield.
The absorption maxima coincided with the experimen- formed. A thermochemical study of the formation of
tal data on copper(II) 4-(1-benzotriazolyl)-5-(1-naph- copper(II)
4-(1-benzotriazolyl)-5-(p-chlorothiaphe-
nyl)phthalocianine showed that the highest yield
(9.2%) was obtained when the mixture was heated
to 200°ë. The yield of CuPc decreased to 0.9% when
the mixture was heated to 167°ë, and no final product
was detected when the mixture was heated to 250°ë,
probably, because of the thermal oxidative destruction
of copper(II) 4-(1-benzotriazolyl)-5-(p-chlorothiaphe-
nyl)phthalocyanine.
thoxy)phthalocyanine (345 nm (0.969), 619 nm (0.389),
and 690 nm (1.604)) to within measurement errors. The
theoretical yield of the desired product calculated
according to the equation for the formation of CuPc
was 9.39 mg (9.16%) under the conditions used.
Similar thermochemical and spectral studies were
performed for mixtures of copper(II) acetate with all
benzotriazolyl substituted phthalodinitriles. Note that
heating of a mixture of 4-(1-benzotriazolyl)-5-(p-
iodophenoxy)phthalodinitrile with copper(II) acetate to
250°ë gave a powder insoluble in CHCl3 and dimethyl-
formamide (DMFA). It is likely that the thermooxida-
tive destruction of copper(II)4-(1-benzotriazolyl)-5-(p-
iodophenoxy)phthalocianine obtained in the template
synthesis began at 250°ë. In subsequent studies, mix-
tures were heated to 240°ë, which corresponded to
monotonic changes in the shape of DTA curves.
A theoretical analysis allows us to suggest that the
heat effect of formation of CuPc depends on the elec-
tron donor ability of the corresponding phthalodini-
triles. In addition, the geometric parameters of metal-
lophthalocyanines can play an important role, because
a planar structure of molecules contributes to effective
π-dative interactions between the central copper(II) ion
and the aromatic conjugated system of the phthalocya-
nine macroring. The introduction of complex periph-
It was found experimentally that the yield of the eral substituents (benzotriazole, naphthoxy, dichlo-
desired product (ϕ) substantially depended on the tem- rophenoxy, etc. groups) into the macroring results in
perature at which the template synthesis was per- macroring distortions. The degree of distortion of cop-
t, °C
900
100
300
500
700
20
60
2
1
3
100
–U, µV
Differential thermal analysis curves of (1) 4-(1-benzotriazolyl)-5-(1-naphthoxy)phthalodinitrile with copper (II) acetate, (2) copper
acetate crystal hydrate, and (3) 4-(1-benzotriazolyl)-5-(1-naphthoxy)phthalodinitrile.
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A Vol. 82 No. 11 2008

1850
PAVLYCHEVA et al.
per(II) phthalocyanines was qualitatively estimated by azolyl)-5-(p-chlorothiaphenyl)phthalocyanine which is
the minimization of their geometric structures. The caused by weaker electron acceptor properties of the
degree of distortion was characterized by the sum of the sulfur atom in PhDN III compared with the oxygen
root-mean-square deviations of atoms from a plane. atom in PhDN II and also of the Cl para substituent
The planarity of molecules was found to increase in the (σ = 0.17 [11]–0.23 [12]) in III compared with I (σ =
CuPc series
0.26 [11]–0.28 [12]) in PhDN II.
II' < V' < III' < IV' < I'.
(1)
ACKNOWLEDGMENTS
It follows that the π-dative component of Cu2+–phthalo-
cyanine interactions also increases in this series. The
series constructed on the basis of the heat effects of for-
mation of CuPc is
This work was financially supported by the Russian
Academy of Sciences (Program of Basic Research
“Synthesis of Substances with the Desired Properties
and Creation of Functional Materials on Their Base”
no. 8P) and the Foundation for Promotion of Science in
Our Country.
I' > IV' > III' > V' > II'.
(2)
Series (1) and (2) do not coincide, which shows that
the geometric requirements are not predominant. It fol-
lows that the electron acceptor properties of peripheral
substituents have the strongest influence on the
enthalpy parameter of CuPc formation. Electron accep-
tor substituents decrease the σ-electron density of
nitrile group nitrogen atoms and thereby decrease the
ability of this group to interact with the Cu2+ ion. Elec-
tron donor substituents, conversely, increase the elec-
tron density on CN group nitrogen atoms. The phthalo-
dinitriles studied only differ in the nature of the substit-
uent in the fifth position.
For instance, in I and II, the electron effects of the
1-naphthoxy and 2-naphthoxy substituents differ not
very substantially, which results in comparatively close
∆H complex formation values. Nevertheless, note that
the positive induction effect of the hydrocarbon substit-
uent (C10H8) decreases the electron acceptor ability of
the bridge oxygen atom, which shifts electron density
from the nitrile group nitrogen atom to a much lesser
degree.
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