Synthesis of new lanthanide naphthalocyanine complexes based on 6,7-bis(phenoxy)-2,3-naphthalodinitrile and their spectral and electrochemical investigation

Article abstract of DOI:10.1007/s11172-008-0258-6

A number of naphthalocyanine and dinaphthalocyanine complexes of the rare-earth elements based on 6,7-bis(phenoxy)-2,3-naphthalodinitrile obtained for the first time has been synthesized and their spectral properties have been investigated. Electrochemical behavior of lutetium [bis(octaphenoxy) naphthalocyanine] in the thin hydrophobic films has been studied.

Full text of DOI:10.1007/s11172-008-0258-6

Russian Chemical Bulletin, International Edition, Vol. 57, No. 9, pp. 1912—1919, September, 2008
1912
Synthesis of new lanthanide naphthalocyanine complexes
based on 6,7ꢀbis(phenoxy)ꢀ2,3ꢀnaphthalodinitrile and their spectral
and electrochemical investigation
T. V. Dubinina,a R. A. Piskovoi,a A. Yu. Tolbin,a,b V. E. Pushkarev,a,b M. Yu. Vagin,a
L. G. Tomilova,a,b and N. S. Zefirova
aM. V. Lomonosov Moscow State University, Department of Chemistry,
1 Leninskie Gory, 119992 Moscow, Russian Federation.
Fax: +7 (495) 939 0290. Eꢀmail: tom@org.chem.msu.ru
bInstitute of Physiologically Active Compounds, Russian Academy of Sciences,
1 Severnyi prꢀd, 142432 Chernogolovka, Moscow Region, Russian Federation
A number of naphthalocyanine and dinaphthalocyanine complexes of the rareꢀearth eleꢀ
ments based on 6,7ꢀbis(phenoxy)ꢀ2,3ꢀnaphthalodinitrile obtained for the first time has been
synthesized and their spectral properties have been investigated. Electrochemical behavior of
lutetium [bis(octaphenoxy)naphthalocyanine] in the thin hydrophobic films has been studied.
Key words: 6,7ꢀbis(phenoxy)ꢀ2,3ꢀnaphthalodinitrile, naphthalocyanines, dinaphthalocyaꢀ
nine complexes, electronic absorption spectra, cyclic voltammetry, hydrophobic mark, lanꢀ
thanides.
Phthalocyanine complexes are widely studied. Due to
thalodinitrile 1 and REE salt in a melt; as well as the
synthesis under microwave irradiation carried out for naphꢀ
thalocyanines for the first time.
The free ligand was obtained according to Scheme 1.
This approach allowed us increase the total yield of the
target compound 3 to more than 2 times in comparison
with the alternative oneꢀstep synthesis of unsubstituted
free naphthalocyanine from naphthalodinitrile.4
The synthesis of compound 1 was carried out starting
from 6,7ꢀdibromoꢀ2,3ꢀnaphthalodinitrile, obtained from
4,5ꢀdibromoꢀoꢀxylene in 84% yield according to the stanꢀ
dard procedure5, and phenol in the presence of K2CO3 in
anhydrous DMF under argon at 130 °C; the reaction mixꢀ
ture was kept at this temperature for 12 h. According to the
TLC data, the formation of the target product was obꢀ
served during 2 h. On elevation of the temperature above
130 °C, the yield of the target product decreases due to the
phenol destruction. 6,7ꢀDibromoꢀ2,3ꢀnaphthalodinitrile
was isolated in a pure form by column chromatography, its
composition and structure were confirmed by the elemenꢀ
tal analysis, 1H and 13C NMR spectroscopy, IR spectrosꢀ
copy, and mass spectrometry data. The yield of compound
1 was 65%. Due to the decrease in the reaction time, as
well as to the optimization of purification conditions, we
succeeded in considerable increase in the reaction product
yield relatively to its analog described in the procedure
from Ref. 6.
the presence of a long multicontour conjugation system in
molecules of these compounds, they are used in catalysis,1
nonlinear optics,2 and cancer diseases therapy.3 However,
the structural phthalocyanine analogs, 2,3ꢀnaphthalocyaꢀ
nines, are studied considerably less.
It is known that the widening of the conjugation sysꢀ
tem causes a considerable (up to 100 nm) bathochromic
shift of the Qꢀband in the electronic absorption spectra
of naphthalocyanines in comparison with the spectra of
phthalocyanines. An introduction of functional groups into
naphthalocyanine ligands, a possibility of a metal ion inꢀ
corporation into the center of a macrocycle, and an abiliꢀ
ty, similarly to phthalocyanines, to form twoꢀdeck comꢀ
plexes allows one to vary their properties within a wide
range. Therefore, a directed synthesis of new substituted
naphthalocyanines is an important problem, as well as
a study of their properties in order to establish the strucꢀ
ture—properties relationship and to broaden the scope
of their application.
The present work deals with the synthesis of both
the planar and the sandwich compounds on the basis of
6,7ꢀbis(phenoxy)ꢀ2,3ꢀnaphthalodinitrile (1) synthesized
for the first time. For obtaining of naphthalocyanine comꢀ
plexes, several methods were chosen: the synthesis with
the use of 3,4,12,13,21,22,30,31ꢀoctaphenoxynaphthaloꢀ
cyanine (preliminary obtained by demetallation of the corꢀ
responding magnesium complex 2) and the corresponding
rareꢀearth element (REE) acetate; the reaction of naphꢀ
To obtain magnesium complex 2 according to a modiꢀ
fied procedure,7 preꢀsynthesized naphthalodinitrile 1 and
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1879—1885, September, 2008.
1066ꢀ5285/08/5709ꢀ1912 © 2008 Springer Science+Business Media, Inc.

Lanthanide naphthalocyanine complexes
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 9, September, 2008
1913
Scheme 1
Scheme 2
Mg(OAc)2•2H2O (4 : 1) were used in nꢀoctanol in the
presence of DBU. The synthesis was conducted until comꢀ
plete disappearance of the starting naphthalodinitrile 1,
that was estimated from TLC. As a rule, the process time
was 3 h. Compound 2 was obtained in 68% yield. It was
found that compound 2 is extremely unstable in solution,
as it was observed earlier6 for structurally similar naphthaꢀ
locyanines.
Free ligand 3 was obtained by dissolution of magneꢀ
sium complex 2 in concentrated sulfuric acid with subseꢀ
quent pouring of the solution on ice. A precipitate formed
was filtered off, washed with methanol and the solid resiꢀ
due was dried in a vacuum drying oven. The yield of prodꢀ
uct 3 was 92%.
Mononaphthalocyanines 4—6 were synthesized acꢀ
cording to Scheme 2 starting from free ligand 3 and
Ln(OAc)3•nH2O by reflux in oꢀdichlorobenzene (oꢀDCB)
in the presence of DBU.8
According to the TLC and UV—Vis data, the target
compounds 4—6 were obtained already in 15 min after the
synthesis began. The reaction time was 1 h. It was found
that there is no formation of dinaphthalocyanine under
these conditions, even when the ligand : REE salt ratio was
2 : 1 and when the reaction time was increased to 1.5—2 h.
Apparently, this results not only from the temperature efꢀ
fect on the coordination of the second macrocycle in the
REE ion sphere, but also from the coordinating ability
Ln = Lu (4), Er (5), Eu (6)
of DBU, as well as from the strength of the metal—counꢀ
terion bond, that agrees with the literature data.9 The yields
of products 4—6 are given in Table 1.
Dinaphthalocyanine complexes 7—9 were synthesized
by the reaction of naphthalodinitrile and REE salt in a melt

1914
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 9, September, 2008
Dubinina et al.
Table 1. Characteristics of naphthalocyanine 3 and naphthaloꢀ
cyanine complexes 2 and 4—9
Scheme 3
Compꢀ Yield
λ
max/nm
MS*, m/z
lex
(%)
(THF)
2
68
359, 681,
727, 762
1473 [M]+,
1381 [M – OPh]+
1451 [M]+,
3
4
5
6
7
92
82
84
83
41
330, 717, 779
332, 703, 751, 786** 1358 [M – OPh]+
355, 682, 762
352, 679, 760
352, 681, 760
1685 [M]+, 1777
[MOAc + НY]+
1677 [M]+, 1771
[MOAc + НY]+.
1662 [M]+, 1756
[MOAc + НY]+
3073 [M]+, 2980
[M – OPh]+, 2888
[M – 2 OPh]+,
339, 590, 618,
677, 758
2796 [M – 3 OPh]+,
2703 [M – 4 OPh]+
3065 [M]+, 2973
[M – OPh]+, 2881
[M – 2 OPh]+
3050 [M]+, 2958
[M – OPh]+
8
9
47
55
336, 591, 615,
679, 762
339, 594, 623,
682, 769
* HY is a matrix molecule (3,5ꢀdihydroxybenzoic acid was used
as the matrix).
** oꢀDCB.
(Scheme 3). This method considerably differs from the
synthesis in solution since the starting nitrile serves simulꢀ
taneously as the reagent and the reaction medium.10,11
According to this method, the synthesis of dinaphthaꢀ
locyanines 7—9 was performed by melting of a mixture of
dinitrile 1 with the corresponding REE acetates by the
gradual increase of temperature from 220 to 310 °C and by
keeping at this temperature until the reaction mixture was
solidified (~2 h). The use of higher temperatures than it
was in the procedure described earlier10 allowed us to obꢀ
tain the target compounds in considerably higher yields.
The reaction course was monitored using spectrophotometry.
When the syntheses were carried out at 310 °C, the formaꢀ
tion of mononaphthalocyanine was not detected, that, apꢀ
parently, is caused by its high reactivity under the reaction
conditions. The reaction mixture was quenched by dissoꢀ
lution in DMF and further precipitation with methanol.
The precipitate formed was filtered off, washed with methꢀ
anol and water, and dried. Compounds 7—9 were purified
using chromatography.
Ln = Lu (7), Er (8), Eu (9)
In addition to the melting method, the europium and
erbium dinaphthalocyanine complexes were synthesized
using microwave irradiation (MW). This method has been
suggested for the first time13 for the synthesis of unsubstiꢀ
tuted and octaꢀtertꢀbutylꢀsubstituted REE diphthaloꢀ
cyanines and so far has not been used for preparation of
naphthalocyanine complexes.
Naphthalodinitrile 1 and acetates of the corresponding
REE salts were used to obtain the dinaphthalocyanine
complexes. The synthesis was carried out by irradiation
of a mixture of reagents in a microwave oven (Samsung,
a 1714R model). The power of irradiation was varied
from 300 to 1000 W, the time, from 3 to 10 min. The
following conditions were found to be optimal for the synꢀ
thesis of dinaphthalocyanines with the use of the MW
energy: the power of 700 W and the reaction time of
5—7 min. The use of microwave irradiation of higher powꢀ
er led to resinification of 2,3ꢀnaphthalodinitrile 1. The use
of MW allowed us to considerably simplify the synthesis
(which can be carried out solventꢀfree), as well as to deꢀ
crease the synthesis time from several hours to several minꢀ
utes. The yields of dinaphthalocyanines given in Table 1
are comparable with the results obtained by the melting
method.
It was found that the yields of dinaphthalocyanine comꢀ
plexes gradually decrease on going from europium to luteꢀ
tium, that agrees with the literature data.12 It was noted12
that the change of the yield correlates with the size of
the central ion. Apparently, this is caused by a decrease in
the REE ionic radius from europium to lutetium and by
the corresponding increase in the sterical effect.

Lanthanide naphthalocyanine complexes
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 9, September, 2008
1915
Table 2. 1H NMR data for compound 1, magnesium naphꢀ
thalocyanine complex (2), and lutetium (7), erbium (8), and
europium (9) dinaphthalocyanine complexes
To confirm the structures of the REE naphthalocyaꢀ
nine complexes obtained, H NMR spectroscopy, MALꢀ
1
DIꢀTOF mass spectrometry, and the UV—Vis spectroscoꢀ
py were used. The presence of the [Nc•–Ln3+Nc2–]0 radiꢀ
cal fragment in the dinaphthalocyanine molecules hinders
obtaining satisfactory NMR data in common solvent.
Comꢀ
pound
δ* (J/Hz)
αꢀНAr
βꢀНAr
НOPh
1
Therefore, for recording the H NMR spectra, the sandꢀ
1
8.69
(s, 2 Н)
7.66
(s, 2 Н)
7.19 (d, 4 Нo, J = 7.8);
7.26 (t, 2 Нp, J = 7.3);
7.48 (t, 4 Нm, J = 7.3)
7.21—7.45 (м, 40 Н)
wichꢀlike complexes were converted to the forms containꢀ
ing no radical fragments using procedure described earliꢀ
er.12
2
7
9.57
(s, 8 Н)
9.09
8.04
(s, 8 Н)
8.06
Hydrazine hydrate (1—2 vol.%) was added to a soluꢀ
tion of REE dinaphthalocyanine in deuterated THF, that
7.21 (t, 16 Нp, J = 7.1);
7.29 (d, 32 Нo, J = 7.7);
7.50 (t, 32 Нm, J = 7.15)
9.96 (m, 16 Нp);
10.57 (m, 32 Нm)
12.06 (m, 32 Нo)
–
resulted in the reduction of the radical fragment Nc• to
(s, 16 Н) (s, 16 Н)
dianion Nc2– (Scheme 4).
8
9
36.71
(s, 16 Н) (s, 16 Н)
19.88
Scheme 4
11.07
8.98
7.05—7.75 (m, 80 Н)
(s, 16 Н) (s, 16 Н)
* The spectra of compound 1 were recorded in DMSOꢀd6,
of compounds 2 and 7—9, in THFꢀd8 with N2H4•H2O
(1—2 vol.%) as the additive.
Thus, both macrocycles in the dinaphthalocyanine
molecule become diamagnetic, that allows us to obtain
satisfactory signals in the 1H NMR spectrum. For europiꢀ
um and, especially, for erbium dinaphthalocyanines, the
upfield shift of all the signals was observed, that is exꢀ
plained by the paramagnetic nature of these metal ions.
Deshielding of the protons is the largest in the case of
[(PhO)8Nc]2Er, that was noted earlier9 for the symmetriꢀ
cally substituted phthalocyanine complexes, and for the
first time was demonstrated by us for the naphthalocyaꢀ
nine complexes. In the 1H NMR spectrum of magnesium
naphthalocyanine 2, the resonance signals characteristic
of nitrile 1 upfield shifted by 0.4—0.9 ppm were also obꢀ
served. The protons of the phenoxy substituents of erbium
8 and europium 9 dinaphthalocyanines, as well as of magꢀ
nesium naphthalocyanine 5 resonate as wide signals, for
which it is impossible to determine the spinꢀspin coupling
constants.
data in Table 1 suggest the higher stability of europium
dinaphthalocyanine 9 in comparison with erbium comꢀ
plex 8 and, especially, with lutetium complex 7. Similarly
to compound 9, the fragmentation with the loss of only
one phenoxy group takes place also in the case of free
ligand 3 and magnesium complex 2. The mass spectroꢀ
metric data are given in Table 1.
Spectrophotometry allows the complete solution of the
problem of identification of various forms of complexes
during the synthesis and purification of naphthalocyanines.
We have studied the UV—Vis spectra for all the comꢀ
pounds obtained.
The spectra of mononaphthalocyanines are characterꢀ
ized by an intensive Qꢀband in the region of 760 nm (which
is typical of Nc2– and corresponds15 to the electronic tranꢀ
sitions a1u → eg), as well as by a vibrational satellite of
lower intensity in the region of 680—720 nm. The Soret
band, responsible for the transition a2u → eg, has the maxꢀ
imum in the region of 340—350 nm. In contrast to the
nonmetallated phthalocyanines, of which the splitting of
the Qꢀband (Fig. 1) into two components in the region of
650—720 nm is characteristic,9 in the UV—Vis of naphꢀ
thalocyanine ligands, the splitting of the Qꢀband is not
observed. It was found15 by the MO calculations that this
phenomenon results from the degeneration of the free
naphthalocyanine b1gꢀ and b2gꢀorbitals.
The NMR data for compound 1, magnesium naphꢀ
thalocyanine 2, lutetium 7, erbium 8, and europium 9
dinaphthalocyanines are given in Table 2.
The structures of all the naphthalocyanine complexes
obtained were confirmed by MALDIꢀTOF mass specꢀ
tra. This method is used the most widely for analysis of
phthalocyanine compounds,12,14 due to the mild condiꢀ
tions of their ionization and relatively simple analysis of
the spectra obtained. In the spectra of compounds 7—9,
the peaks of the singleꢀcharged ions were observed with
the masses corresponding to the molecular ions of the tarꢀ
get substances. It was found that the fragmentation occurs
by elimination of phenoxy groups from the macromoleꢀ
cule. In the series of Lu, Er, and Eu dinaphthalocyanine
complexes the number of eliminating substituents decreasꢀ
es from four (in the case of lutetium complex) to one (in
the case of europium complex). This fact, as well as the
In the spectra of dinaphthalocyanines obtained, a Qꢀband
in the region of 755—770 nm and a characteristic band in
the region of 590 nm caused by the presence of an unpaired
electron in the molecule are observed. The Soret band
maximum is in the region of 335—340 nm (see Table 1).

1916
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 9, September, 2008
Dubinina et al.
A
tensity of absorption in the region of the Qꢀband, right up
to its complete disappearance, was observed. Simultaꢀ
neously, the appearance of two new absorption maxima
(at 816 and 634 nm for lutetium dinaphthalocyanine and
at 822 and 641 nm for erbium dinaphthalocyanine) was
observed, whereas the position of the Soret band was not
shifted. As an example, the UV—Vis spectra recorded durꢀ
ing oxidation of [(PhO)8Nc]2Lu in THF are given in Figꢀ
ure 2. On treatment with hydrazine hydrate, the starting
neutral form of dinaphthalocyanine is slowly recovered, and
further reduced to dianion in excess of hydrazine hydrate.
To carry out the reduction, a small amount of hydraꢀ
zine hydrate (which did not considerably change the soluꢀ
tion volume) was added to a solution of the starting diꢀ
naphthalocyanine in THF. During this, a decrease in inꢀ
tensity of the absorption in the region of the Qꢀband was
observed with the simultaneous appearance of two new
absorption maxima: the intensive one (at 698 nm) and the
less intensive (at 820 nm) for lutetium dinaphthalocyaꢀ
nine, and at 701 and 808 nm, respectively, for erbium
dinaphthalocyanine. A bathochromic shift of the Soret
band (by 6—7 nm) also takes place. The change of
UV—Vis spectra, recorded during the reduction of erbium
dinaphthalocyanine complex, is given in Figure 3.
The redoxꢀtransformations in all the cases under study
are characterized by the presence of the isobestic points.
This suggests an ability of naphthalocyanines obtained
to be reversibly oxidized and reduced under action of
the corresponding chemical agents and the presence of
electrochromic properties. Therefore, it was of interest to
carry out more detailed study of electrochemical behavior
of the complexes synthesized. As the example, the results
of electrochemical study of complex 7 by cyclic voltamꢀ
metry method are given in Figure 4.
2.0
1.5
1.0
0.5
400
500
600
700
800 λ/nm
Fig. 1. The UV—Vis spectra of free phthalocyanine EtPcH2
(the dotted line) and naphthalocyanine [(PhO)8Nc]H2 (solid
line) in oꢀDCB.
Analysis of the UV—Vis spectra of dinaphthalocyanine
complexes obtained allowed us to reveal a number of feaꢀ
tures characteristic of these compounds. Thus, on going
from [(PhO)8Nc]2Lu to [(PhO)8Nc]2Eu a bathochromic
shift of the Qꢀband by 11 nm is observed caused by an
increase in the ionic radius. In this case, the position of the
Soret band changes inconsiderably.
The absorption spectra of the dinaphthalocyanine comꢀ
plexes in solution change on prolonged exposure to the
light, in particular, a decrease in the Qꢀband intensity acꢀ
companied by appearance of the absorption bands in the
regions of 600 and 800 nm is observed. It was found that
addition of N2H4•H2O to the solution leads to the quantiꢀ
tative recovery of the starting compound, which is conꢀ
firmed by the UV—Vis data. This allowed us to suggest
a reversible character of the oxidation process of dinaphthꢀ
alocyanines in air.
To confirm such a suggestion, a behavior of symmetriꢀ
cal lutetium and erbium dinaphthalocyanine complexes
obtained has been investigated in the processes of chemiꢀ
cal oxidation and reduction.
For oxidation, a solution of dinaphthalocyanine in
THF was treated with bromine vapors. A decrease in inꢀ
A working disk electrode made of the side section of the
highly oriented pyrolytic graphite was entirely covered with
a thin film of the lutetium naphthalocyanine solution in
nitrophenyl octyl ether. Since the latter does not mix with
A
A
2.0
1
2.0
1
1.5
1.5
1.0
1.0
2
2
0.5
0.5
400
500
600
700
800
λ/nm
400
500
600
700
800
λ/nm
Fig. 2. The UV—Vis spectra of the neutral (1) and the oxidized
with bromine (2) forms of [(PhO)8Nc]2Lu in THF, the dotted
lines correspond to the intermediate forms.
Fig. 3. The UV—Vis spectra of the neutral (1) and the reduced
with hydrazine hydrate (2) forms of [(PhO)8Nc]2Er in THF,
the dotted lines correspond to the intermediate forms.

Lanthanide naphthalocyanine complexes
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 9, September, 2008
1917
caused by the increase in hydrophobic properties of
the aqueous phase anion (ClO4–). A similar shift of the
redoxꢀactivity potential of a hydrophobic substance toꢀ
ward the cathodic region was observed earlier for decameꢀ
thylferrocene,18—20 metalloporphirines,21,22 redoxꢀactive
oils,23—26 and redoxꢀactive polymers.27
I/μA
A
II
1.0
0.5
B
In conclusion, lutetium naphthalocyanine can be used for
the evaluation of hydrophobic properties of anions during
their transfer through the interface of two unmixable liquids.
I
0
I
–0.5
II
Experimental
–1.0
Electronic absorption spectra in the visible region were obꢀ
tained with Heliosꢀα spectrophotometer in 0.5ꢀ and 1ꢀcm thick
quartz cuvettes using C6H6, THF, and oꢀDCB as the solvents.
1H and 13C NMR spectra were recorded with a Bruker AMꢀ300
(300.14 and 75.47 MHz, respectively) and Bruker WMꢀ250 specꢀ
trometers (250.13 and 62.90 MHz, respectively) in CDCl3,
DMSOꢀd6, or THFꢀd8. Chemical shifts are given in δ scale relaꢀ
tively to Me4Si. Preparative TLC was performed on Merck Silica
Gel 60 F254 and Merck Aluminum Oxide F254 neutral
plates, column chromatography, on Lancaster Silica Gel 60
(0.060—0.200 mm), Merck Silica Gel 40 (0.063—0.200 mm),
and Merck Aluminum Oxide 90 sorbents. Mass spectra were
recorded with a Finnigan MAT INSOCꢀ50 (EI, 70 eV) and
VISIONꢀ2000 instruments (MALDIꢀTOF). IR spectra were reꢀ
corded with a Specord Mꢀ70 and Specord URꢀ20 spectrophoꢀ
tometers in Nujol. All solvents were purified according to the
standard procedures just before use. Salts Lu(OAc)3•4H2O,
Er(OAc)3•2H2O, Eu(OAc)3•3H2O, and Mg(OAc)2•2H2O were
kept before synthesis for 5 h in a vacuum drying oven at 100 °C.
The synthesis of naphthalocyanines under microwave irradiation
was performed using a Samsung 1714R device.
6,7ꢀBis(phenoxy)ꢀ2,3ꢀnaphthalodinitrile (1). 6,7ꢀDibromoꢀ
2,3ꢀnaphthalodinitrile (5.23 g, 0.016 mol), phenol (4.30 g,
0.046 mol), freshly calcined potash (26.86 g, 0.195 mol), and
anhydrous DMF (100 mL) were placed into a 250ꢀmL threeꢀ
neck flask equipped with a reflux condenser, thermometer, and
a drying tube packed with CaCl2. The mixture was heated to
130 °C and kept for 12 h under argon. Monitoring of the reaction
course was performed by TLC (SiO2 F254, eluent: C6H6). After
the reaction was complete, the cooled reaction mixture was
poured into water (400 mL). A precipitate formed was filtered
off, washed with water until neutral pH, and dried at 60 °C. The
mass obtained was subjected to column chromatography (SiO2,
eluent: C6H6), the target product isolated was dried at 60 °C to
obtain compound 1 (3.71 g, 64%) as white needleꢀlike crystals,
m.p. 219—220 °C, Rf = 0.33 (SiO2 F254, eluent: C6H6). Found (%):
C, 79.36; H, 4.08; N, 7.61. C24H14N2O2. Calculated (%):
C, 79.56; H, 3.87; N, 7.73. 1H NMR ((CD3)2SO), δ: 7.19 (d, 4 H,
oꢀHPhO, J = 7.8 Hz); 7.26 (t, 2 H, pꢀHPhO, J = 7.4 Hz); 7.48
(t, 4 H, mꢀHPhO, J = 7.3 Hz); 7.66 (s, 2 H, βꢀHAr(5), βꢀHAr(8));
8.70 (s, 2 H, αꢀHAr(1), αꢀHAr(4)). 13C NMR ((CD3)2SO), the
atoms numeration is given according to the IUPAC rules, δ:
107.2 (CAr(2), CAr(3)); 115.3 (CN); 116.0 (CAr(5), CAr(8)); 118.6
(COPh(2), COPh(6)); 124.3 (CAr(9), CAr(10)); 127.8 (COPh(4));
129.9 (CAr(1), CAr(4)); 134.5 (COPh(3), COPh(5)); 150.4 (CAr(6),
CAr(7)); 154.7 (COPh(1)). IR, ν/cm–1: 2245 (νC≡N), 1592 (νC=C),
1496 (νC=C), 1465 (νC=C), 1385 (νC—O). MS (EI, 70 eV), m/z:
362 [M]+.
–0.2
Fig. 4. Cyclic voltammograms of the liquid film of lutetium
dinaphthalocyanine, 0.2 μL in nitrophenyl octyl ether (1 mg mL–1
on the highly oriented pyrolytic graphite (~3 mm in diameter);
0.1 M KCl (A) or KClO4 (B), the potential scan rate was 20 mV s–1
0
0.2
E/V (Ag/AgCl)
)
.
water, the working electrode turned out to be modified
with a thin liquid film of solution of the hydrophobic reꢀ
doxꢀactive lutetium naphthalocyanine when an aqueous
solution of the supporting electrolyte was used.
To maintain the electroneutrality of the organic phase
of the film, the oxidation of lutetium naphthalocyanine
should be accompanied by a simultaneous crossing the inꢀ
terface between two phases (nitrophenyl octyl ether—waꢀ
ter) by ions. In another words, the electrode process incluꢀ
des a simultaneous crossing the interface electrode—film
by an electron and the interface film—water by ions.
In the cyclic voltammogram recorded at the modified
electrode in aqueous solution of potassium chloride (curve A),
two pairs of peaks, I and II, are observed corresponding to
the redoxꢀactivity of lutetium naphthalocyanine. It is
known16,17 that the redoxꢀtransition I (oneꢀelectron reꢀ
duction) is accompanied by the transfer of K+ ions from
water into the organic phase and back, whereas the redoxꢀ
transition II (oneꢀelectron oxidation), by the transfer of
Cl– ions into the organic phase. The difference in intensiꢀ
ties of peaks I and II is caused by the difference in the
interface crossing rates for anions and cations. In curve B
recorded in aqueous solution of potassium perchlorate,
only one pair of peaks of redoxꢀactivity II is observed,
which is related to the transfer of ClO4–. The potential of
this redoxꢀtransition is shifted to cathode potentials region
with respect to the position of the redoxꢀactivity peaks
observed in the solution containing Cl– ion (curve A). The
difference in positions of the peaks of redoxꢀactivity II
resulted from the difference in hydrophobic properties of
the crossing anion: on its increase, the potential of redoxꢀ
activity is shifted toward the cathode region. The peaks of
redoxꢀactivity I accompanied by the transfer of cations
through the interface was not observed in curve B due to
the strong cathodic shift of the peaks of redoxꢀactivity II

1918
Russ.Chem.Bull., Int.Ed., Vol. 57, No. 9, September, 2008
Dubinina et al.
Magnesium (3,4,12,13,21,22,30,31ꢀoctaphenoxy)ꢀ2,3ꢀnaphꢀ
thalocyanine (2). Compound 1 (500 mg, 1.38 mmol), nꢀoctanol
(4 mL), and magnesium acetate (240 mg, 1.35 mmol) were placed
in a 20ꢀmL twoꢀneck flask equipped with a distilling column, and
a drying tube packed with CaCl2. The mixture was heated until
complete dissolution of the nitrile followed by addition of DBU
(70 mg, 0.46 mmol) and then refluxed for 3 h under Ar. Monitorꢀ
ing of the reaction course was performed by TLC (SiO2, eluent:
C6H6). After the reaction was complete, methanol (80 mL) was
added to the cooled reaction mixture. A precipitate formed was
filtered off, washed with water, aq. methanol, and dried in air.
The mass obtained was dissolved in THF and precipitated with
methanol. A bright green precipitate formed was filtered off,
washed with hot methanol (4×10 mL), and dried in a vacuum
drying oven at 60 °C to obtain compound 2 (345 mg, 68%) as a
darkꢀgreen powder. 1H NMR (THFꢀd8), δ: 7.18—7.42 (m, 20 H,
HOPh); 8.03 (s, 8 H, βꢀHAr); 9.54 (s, 8 H, αꢀHAr). MS (MALDIꢀ
TOF), m/z: 1473 [M]+, 1381 [M – OPh]+. UV—Vis (THF),
vation of temperature from 220 to 310 °C, then, the reaction
mixture was kept at this temperature for 2 h until the reaction
mass solidified. After the synthesis was complete, the reaction
mixture was dissolved in DMF and dinaphthalocyanine was preꢀ
cipitated with methanol. The precipitate was filtered off and
dried at 70 °C, dissolved in benzene, and subjected to chromaꢀ
tography on a column with Al2O3 with THF—C6H6 (1 : 10) as
the eluent.
Lutetium bis[(3,4,12,13,21,22,30,31ꢀoctaphenoxy)ꢀ2,3ꢀ
naphthalocyanine] (7). The yield was 130 mg (41%). UV—Vis
(THF), λmax/nm: 339, 590, 618, 677, 758. MS (MALDIꢀTOF),
m/z: 3073 [M]+, 2980 [M – OPh]+, 2888 [M – 2 OPh]+, 2796
[M – 3 OPh]+, 2703[M – 4 OPh]+. 1H NMR (THFꢀd8), δ: 7.21
(t, 16 H, pꢀHOPh, J = 7.1 Hz); 7.29 (d, 32 H, oꢀHOPh, J = 7.7 Hz);
7.50 (t, 32 H, mꢀHOPh, J = 7.2 Hz); 8.04 (s, 16 H, βꢀHAr); 9.07
(s, 16 H, αꢀHAr).
Erbium bis[(3,4,12,13,21,22,30,31ꢀoctaphenoxy)ꢀ2,3ꢀnaphꢀ
thalocyanine] (8). The yield was 150 mg (47%). UV—Vis (THF),
λ
max/nm: 359, 681, 727, 762.
(3,4,12,13,21,22,30,31ꢀOctaphenoxy)ꢀ2,3ꢀnaphthalocyanine
λmax/nm: 336, 591, 615, 679, 762. MS (MALDIꢀTOF), m/z:
3065 [M]+, 2973 [M – OPh]+, 2880 [M – 2 OPh]+. 1H NMR
(THFꢀd8), δ: 9.95—12.04 (m, 40 H, HOPh); 19.87 (s, 16 H,
βꢀHAr); 36.72 (s, 16 H, αꢀHAr).
(3). Concentrated H2SO4 (17 mL, ρ = 1.84 g mL–1) was added to
a solution of compound 2 (100 mg, 0.07 mmol) in THF (15 mL).
The mixture was vigorously stirred for 2—3 min under cooling in
an iceꢀwater bath until complete dissolution. The reaction mixꢀ
ture obtained was poured on ice. A precipitate formed was filꢀ
tered off, sequentially washed with deionized water until neutral
pH, aq. methanol, and hot methanol, and dried in a vacuum
drying oven at 60 °C to obtain compound 3 (92 mg, 92%) as
a darkꢀgreen powder. MS (MALDIꢀTOF), m/z: 1451 [M]+, 1358
[M – OPh]+. UV—Vis (THF), λmax/nm: 330, 717, 779.
Synthesis of lanthanide (3,4,12,13,21,22,30,31ꢀoctaphenꢀ
oxy)ꢀ2,3ꢀnaphthalocyanines (general procedure). Compound 3
(110 mg, 0.076 mmol), Ln(OAc)3•nH2O (0.380 mmol), and
oꢀDCB (3 mL) were placed in a 20ꢀmL twoꢀneck flask equipped
with a distilling column and a drying tube packed with CaCl2.
The mixture was heated until complete dissolution of the starting
substances followed by addition of catalytic amount of DBU and
reflux for 1 h under Ar. Monitoring of the reaction course was
performed by TLC (Al2O3, eluent: chloroform) and UV—Vis
spectra. After the reaction was complete, the mass was treated
similarly to the procedure for compound 2.
Europium bis[(3,4,12,13,21,22,30,31ꢀoctaphenoxy)ꢀ2,3ꢀ
naphthalocyanine] (9). The yield was 174 mg (55%). UV—Vis
(THF), λmax/nm: 339, 594, 623, 682, 769. MS (MALDIꢀTOF),
m/z: 3050 [M]+, 2958 [M – OPh]+. 1H NMR (THFꢀd8),
δ: 7.07—7.70 (m, 40 H, HOPh); 8.96 (s, 16 H, βꢀHAr); 11.06
(s, 16 H, αꢀHAr).
Synthesis of lanthanide bis[(3,4,12,13,21,22,30,31ꢀoctaphenꢀ
oxy)ꢀ2,3ꢀnaphthalocyanines] (8, 9) using microwave irradiation
(general procedure). Compound 1 (0.3 g, 0.83 mmol) and
Ln(OAc)3•nH2O (0.17 mmol) (Ln = Er, Eu) were placed into
a roundꢀbottom flask and the mixture was placed into a microꢀ
wave oven with the power of irradiation of 700 W. The reaction
time was 5—7 min. After the synthesis was complete, the reacꢀ
tion mixture was dissolved in DMF, and dinaphthalocyanine was
precipitated with methanol. The precipitate was filtered off and
dried at 70 °C, dissolved in benzene, and subjected to chromaꢀ
tography on a column with Al2O3 and THF—C6H6 (1 : 10) as the
eluent. The yields of compounds 8 and 9 were 105 (33%) and
123 mg (39%), respectively.
Lutetium (3,4,12,13,21,22,30,31ꢀoctaphenoxy)ꢀ2,3ꢀnaphꢀ
thalocyanine acetate (4). The yield was 105 mg (82%). UV—Vis
(THF), λmax/nm: 355, 682, 762. MS (MALDIꢀTOF), m/z: 1685
[M]+, 1777 [M – OAc + HY*]+.
References
Erbium (3,4,12,13,21,22,30,31ꢀoctaphenoxy)ꢀ2,3ꢀnaphꢀ
thalocyanine acetate (5). The yield was 107 mg (84%). UV—Vis
(THF), λmax/nm: 352, 679, 760. MS (MALDIꢀTOF), m/z: 1677
[M]+, 1771 [M – OAc + HY]+.
Europium (3,4,12,13,21,22,30,31ꢀoctaphenoxy)ꢀ2,3ꢀnaphꢀ
thalocyanine acetate (6). The yield was 105 mg (83%). UV—Vis
(THF), λmax/nm: 352, 681, 760. MS (MALDIꢀTOF), m/z: 1662
[M]+, 1756 [M – OAc + HY]+.
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Received March 5, 2008;
in revised form August 5, 2008