Erbium complexes of "sandwich" type containing fragments of meso-tetraphenyltetrabenzoporphyrin and phthalocyanines of different structures. Synthesis and spectral properties

Article abstract of DOI:10.1134/S1070428011050186

Reactions of erbium acetate meso-tetraphenyltetrabenzoporphyrinate with excess phthalonitrile, 4-nitroand 4-hydroxyphthalonitrile, and also with dilithium (octa-4,5-pentoxy)-phthalocyanine gave rise to unsymmetrical complexes of "sandwich" structure. The

Full text of DOI:10.1134/S1070428011050186

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2011, Vol. 47, No. 5, pp. 771−777. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © N.E. Galanin, L.A. Yakubov, G.L. Pakhomov, G.P. Shaposhnikov, 2011, published in Zhurnal Organicheskoi Khimii, 2011, Vol. 47,
No. 5, pp. 764−770.
Erbium Complexes of “Sandwich” Type Containing Fragments
of meso-Tetraphenyltetrabenzoporphyrin
and Phthalocyanines of Different Structures.
Synthesis and Spectral Properties
N. E. Galanina, L. A. Yakubova, G. L. Pakhomovb, and G. P. Shaposhnikova
a Ivanovo State University of Chemical Engineering, Ivanovo, 153000 Russia
e-mail: ttoc@isuct.ru
bInstitute of Microstructures Physics, Russian Academy of Sciences, Nizhnii Novgorod, 603950 Russia
e-mail: pakhomov@ipm.sci-nnov.ru
Received December 15, 2009
Abstract—Reactions of erbium acetate meso-tetraphenyltetrabenzoporphyrinate with excess phthalonitrile, 4-nitro-
and 4-hydroxyphthalonitrile, and also with dilithium (octa-4,5-pentoxy)-phthalocyanine gave rise to unsymmetrical
complexes of “sandwich” structure. The spectral properties of compounds synthesized were examined.
DOI: 10.1134/S1070428011050186
Compounds of the phthalocyanine series possess
unique spectral, electrochromic, magnetic, and semi-
conductor properties originating from the multicontour
conjugation system [1]. These compounds are capable
to form complexes with many elements of the Periodic
System. The phthalocyaninates of rare-earth elements
are especially interesting. Lanthanides possessing large
ionic radii and high coordination numbers are able to form
with phthalocyanines and their analogs compounds of the
“sandwich” structure. The latter are characterized by the
overlapping of the π-orbitals of ligands depending on the
size of the lanthanide ionic radius and on the geometric
structure of the macrocycles. This effect opens an op-
portunity to apply sandwich compounds in various fields
of science and technology [2–8]. Nowadays numerous
synthetic procedures are known for the preparation of
diphthalocyaninates both of symmetric and unsymmetri-
cal structure [9–12].Asignificant number of publications
describes also the synthesis and properties of sandwich
complexes containing molecules of phthalocyanine and
porphyrin [13–20]. However the information on such
complexes containing molecules of phthalocyanine
and tetrabenzoporphyrin is scanty [21, 22]. We did not
find any published information on dimeric structures
containing in their composition the molecules of meso-
tetraphenyltetrabenzoporphyrin and phthalocyanines.
We report here on the synthesis and examination of
the spectral properties of erbium complexes of sandwich
type containing fragments of meso-tetraphenyltetrabenzo-
porphyrin and phthalocyanine and also the tetra-4-nitro-,
tetra-4-hydroxy-, and octa-4,5-pentoxy-derivatives of
the latter.
As initial compounds for the synthesis of the sand-
wich complexes meso-tetraphenyltetrabenzoporphyrin
(I) was used prepared by the procedure [23] reacting
phthalimide with phenylacetic acid in the presence of
zinc oxide followed by the demetallation of the formed
zinc meso-tetraphenyltetrabenzoporphyrinate with hy-
drochloric acid. The boiling of the solution in DMF of
porphyrin I with excess erbium acetate in the presence
of 1,5-diazabicyclo[5.4.0]undec-5-ene (DBU) provided
erbium acetate meso-tetraphenyltetrabenzoporphyrinate
(II) (Scheme 1).
The formation of the complex in the reaction mixture
was monitored spectrophotometrically by the disap-
pearance in the electron absorption spectrum (EAS) of
the absorption bands at 698 and 634 nm characteristic
of ligand I and by the appearance at 652 nm the band
corresponding to the Q band of complex II. Due to the
large ionic radius of the metal the reaction proceeded
relatively slow and completed only within 12 h unlike the
771

GALANIN et al.
772
Scheme 1.
Scheme 2.
R = H (III, VI), OH (IV, VII), NO2 (V, VIII)
complexing with the bivalent metals whose complexes
formed in 0.5 h [24].
or 4-nitrophthalonitrile (V) at 280°C over 1 h resulted
in the formation of sandwich complexes meso-tetrap-
henyltetrabenzoporphyrin–erbium–phthalocyanine (VI),
meso-tetraphenyltetrabenzo-porphyrin–erbium–tetra-4-
hydroxyphthalocyanine (VII), and meso-tetraphenyltet-
rabenzoporphyrin–erbium–tetra-4-nitrophthalocyanine
(VIII) (Scheme 2).
The isolation of complex II was performed by di-
luting the reaction mixture with water, filtering off the
formed precipitate and its washing with hot water and
80% methanol. The attempts at chromatographic puri-
fication of complex II were unsuccessful since during
the chromatography both on alumina and on silica gel
using various eluents the compound suffered demetal-
lation. Therefore complex II was used further without
additional purification.
The attempt to synthesize complex meso-tetraphen-
yltetrabenzoporphyrin–erbium–octa-4,5-pentoxyphtha-
locyanine (IX) in the same way, namely, by heating
the mixture of compound II with excess 4,5-dipent-
oxyphthalonitrile (X) was unsuccessful apparently due
to the reduced reactivity of nitrile X caused by the effect
The heating of the mixture of compound II with ex-
cess phthalonitrile (III), 4-hydroxyphthalonitrile (IV),
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ERBIUM COMPLEXES OF “SANDWICH” TYPE
773
Scheme 3.
R = H11C5O.
of two electron-donor substituents. Therefore complex
IX was synthesized by the reaction of compound II with
dilithium (octa-4,5-pentoxy)pthalocyanine (XI) obtained
preliminary by the condensation of nitrile X in 1-pentanol
in the presence of lithium 1-pentanolate. The formation
of complex IX is presented in Scheme 3.
Compounds VI–IX were isolated and purified by
column chromatography. Their composition and structure
were confirmed by elemental analysis, mass spectra,
vibration, and electronic spectroscopy.
In the mass spectra of complexes VI–IX (secondary
ion mass spectrometry, SIMS) the signals of molecular
ions of low intensity were observed at m/z 1490, 1554,
1670, and 2179 respectively, and also the peaks of their
fragment ions: In all spectra signals of medium intensity
were present, m/z 813–815, corresponding to the fragment
of the meso-tetraphenyltetrabenzoporphyrin, and signals
of high abundance, m/z 167, corresponding to the Er+ ion.
Alongside these peaks the mass spectra of compounds
VI–IX contain signals m/z 512, 578, 695, and 1201 respec-
tively, belonging to the fragments of the phthalocyanines
involved in the composition of the complexes.
Fig. 1. IR spectrum of compound VIII.
in the octacoordinate complexes [25], the strong band
at 1352 cm–1 indicates the presence of the phthalocya-
nine fragment [26]. The bands in the region 1433 and
1464 cm–1 characterize vibrations of C–N and C–C in
tetrapyrrole chromophores, therewith the presence of two
bands shows their nonequivalence. In the IR spectrum of
compound VIII (Fig. 1) the vibration band of the N–Er
bond shifted to 888 cm–1, the band corresponding to the
phthalocyanine fragment, to 1346 cm–1, and the bands
In the IR spectrum of compound VI a band present
at 882 cm–1 is characteristic of vibrations of N–Er bond
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GALANIN et al.
774
Fig. 2. EAS of compound VI. (1) in CHCl3, (2) in DMF + 1%
NH2NH2·H2O.
Fig. 4. EAS of compound VII. (1) in CHCl3, (2) in DMF +
1% NH2NH2·H2O.
1) contains in the longwave region a band at λmax 660 nm,
i.e., it is present in this solvent, same as in the solid state,
mainly in the neutral-radical “green” form [27]. This is
confirmed by the ESR spectrum of the solid sample of
compound VI (Fig. 3) measured at 77 K. The intensity
of the signal and the magnitude of the g-factor (2.000)
close to the g-factor of the free electron (2.00232) allow
the conclusion on the presence of an unpaired electron in
compound VI. The form of the ESR curve suggests that
the electron is located on the phthalocyanine fragment and
that the exchange processes of any significance involving
the f-electrons of the metal are absent.
Fig. 3. ESR spectrum of compound VI.
Less strong bands at λmax 695 and 628 nm indicate
the presence in the solution of an insignificant amount
of the anionic “blue” form of complex VI, and the band
at λmax 595 nm is the vibronic satellite of the Q band of
meso-tetraphenyltetrabenzoporphyrin.
related to the vibrations of C–N and C–C bonds of chro-
mophores were observed at 1452–1445 cm–1. The strong
band at 1536 cm–1 characterizes the vibrations of the N–O
bonds in nitro groups. In the spectrum of complex VII
a band is observed at 3565 cm–1 indicating the presence
of hydroxy groups, and in the spectrum of compound
In going from chloroform to DMF with added 1% of
hydrazine hydrate in the EAS of compound VI (Fig. 2, 2)
IX strong bands appear in the region 2960–2943 cm–1 the following changes are observed. The band at 660 nm
corresponding to the vibrations of the C–H bonds of disappears, and the intensities of the bands at λmax 695
the alkoxy substituents. All the spectra of synthesized
sandwich complexes contain absorption bands in the
region 719–725 cm–1 corresponding to the vibrations of
the meso-phenyl substituents.
and 623 nm considerably increase revealing the conver-
sion of complex VI in the presence of a reducer into the
“blue” form, therewith the spectrum in the longwave
region contains two bands.
Electronic spectra of complexes IV–IX are character-
ized by strong absorption in the region 600–700 nm (Q
band), and also by th absorption in the range 350 and
450 nm (Soret bands).
The solvent nature insignificantly affects the position
of Soret bands. The bands corresponding to the absorp-
tion of the porphyrin fragments are located in the region
λmax 464–463 nm, and those characterizing the absorption
in the phthalocyanine chromophores, in the range λmax
Thus the EAS of compound VI in chloroform (Fig. 2,
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ERBIUM COMPLEXES OF “SANDWICH” TYPE
775
Fig. 5. EAS of compound VIII. (1) in CHCl3, (2) in DMF +
1% NH2NH2·H2O.
Fig. 6. EAS of compound IX. (1) in CHCl3, (2) in DMF + 1%
NH2NH2·H2O.
328–333 nm. The presence of four hydroxy groups in of hydrazine hydrate (Fig. 5, 2) the absorption spectrum
in the Q-region is characterized by a single very broad
band with the maximum at λmax 689 nm that may be due to
association processes in this solvent. The lack of bands in
the region λmax 450–500 nm shows the absence of radical
fragments, namely, the existence of complex VIII in the
“blue” form. The bands in the region λmax 335–361 nm
correspond to the Soret bands of phthalocyanine.
the phthalocyanine fragment of compound VII resulted
in the following changes in its EAS. The spectrum of
complex VII in chloroform (Fig. 4, 1) is characterized
by weak bands at λmax 635 nm where the first and the last
bands appear in the same region as in the spectrum of
the metal-free porphyrin I, and the band at λmax 675 nm
corresponds to the Q band of the erbium complex
with tetra-4-hydroxyphthalocyanine. The band at λmax
496 nm shows that complex VII exists in chloroform
in the radical form, the strong band at λmax 465 nm cor-
responds to the Soret band of porphyrin, and the band
with a maximum at λmax 329 nm, to the Soret band of
phthalocyanine.
EAS of compound IX in chloroform (Fig. 6, 1) con-
tains in the longwave region bands with the maxima at
λ
max 700, 660, 645, and 633 nm characteristic of phtha-
locyanine as well as porphyrin chromophores, and the
phthalocyanine absorption prevails. In the region of λmax
463 nm a less strong diffuse band appears corresponding
In going from chloroform to DMF with added 1% of to the Soret band of porphyrin, and the Soret band of the
hydrazine hydrate in the EAS of compound VII the bands
at λmax 675 and 496 nm disappear, and the spectrun (Fig. 4,
2) in it character resembles the spectrum of compound I.
This spectral pattern may indicate the localization of the
unpaired electron on the more electron-deficient in this
case fragment of meso-tetraphenyltetrabenzoporphyrin.
phthalocyanine fragment is observed at λmax 346 nm.
In going from chloroform to DMF with added 1%
of hydrazine hydrate the EAS considerably changes
(Fig. 6, 2). In the longwave region a single broad band
is observed, the Soret band of porphyrin ligand is bet-
ter resolved, whereas the position of the Soret band of
phthalocyanine is materially unchanged. All these data
may indicate the strong association processes of com-
pound IX in DMF.
The introduction of electron-acceptor nitro groups
into the composition of the phthalocyanine fragment also
significantly affects the EAS of complex VIII compared
with the spectra of compound VI. The electronic spectrum
in chloroform (Fig. 5, 1) in the Q-region is characterized
by a band with a maximum at λmax 702 nm and a less
strong band at λmax 635 nm. In the region λmax 494 nm a
weak band is observed indicating the presence of a radical
fragment of the phthalocyanine. In DMF with added 1%
Thus the analysis of the obtained spectral data allows
the following conclusions. The synthesized complexes
of the sandwich structure in air and chloroform solution
exist predominantly in the stable neutral radical “green”
form. At the addition of a reducer the radical form of the
complexes is reduced to the anionic “blue” form. Spectral
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GALANIN et al.
776
properties of the complexes of unsymmetrical structure
depend considerably on the character of the substituents
in the phthalocyanine fragment since their electron-donor
or electron-acceptor nature governs the place of the pre-
vailing localization of the unpaired electron.
tetra-4-hydroxyphthalocyanine (VII) was obtained
with the use of 4-hydroxyphthalonitrile (IV). Yield
15 mg (20%), dark-green powder, well soluble in toluene,
chloroforme, acetone, DMF. EAS, λmax, nm (D/Dmax), in
CHCl3: 696 (0.06), 675 (0.07), 635 (0.17), 496 (0.21),
465 (1.00), 329 (0.38); in DMF + 1% N2H4·H2O: 697
(0.05), 636 (0.14), 464 (1.00), 327 (0.31). IR spectrum,
ν, cm–1: 3565, 3067, 1608, 1488, 1445, 1346, 875, 719,
700, 621. Mass spectrum: m/z 1554 [M]+. Found, %:
C 71.33; H 3.56; N 10.13. C92H52ErN12O4. Calculated,
%: C 70.98; H 3.37; N 10.80.
EXPERIMENTAL
Electron absorption spectra of compounds obtained
were measured on a spectrophotometer Hitachi UV-2001,
mass spectra were obtained on an instrument TOF.SIMS
5-100, IR spectra were recorded on a spectrophotometer
Avatar 360 FT-IR in the region 400–4000 cm–1 from films
on the TlI glass, ESR spectrum was taken on a spectrom-
eter Bruker 380 EMX. Elemental analysis was carried out
on FlashEA 1112 CHNS–O Analyzer.
meso-Tetraphenyltetrabenzoporphyrin–erbium–
tetra-4-nitrophthalocyanine (VIII) was obtained with
the use of 4-nitrophthalonitrile (V). Yield 52 mg (65%),
dark-green powder, poorly soluble in toluene, well soluble
in chloroforme, acetone, DMF. EAS, λmax, nm (D/Dmax),
in CHCl3: 702 (0.28), 635 (0.14), 494 (0.10), 335 (1.00);
in DMF + 1% N2H4·H2O: 681 (0.06), 427 (0.43), 361
(1.00). IR spectrum, ν, cm–1: 3066, 1724, 1604, 1536,
1493, 1445, 1346, 1254, 872, 719, 704, 613. Mass spec-
trum: m/z 1670 [M]+. Found, %: C 67.01; H 3.05; N 13.54.
C92H48ErN16O8. Calculated, %: C 66.06; H 2.98; N 13.40.
4-Hydroxyphthalonitrile (IV) and 4-nitrophthaloni-
trile (V) were obtained by the procedure [28], 4,5-dipent-
oxyphthalonitrile (X), by the method [29].
Erbium acetate meso-tetraphenyltetrabenzopor-
phyrinate (II). To a solution of 0.2 mmol of compound
I in 10 ml of DMF was added 4 mmol of erbium acetate
hexahydrate and 2 ml of DBU, the mixture was boiled
for 12 h, then if was diluted with 30 ml of water, the
separated precipitate was filtered off, washed with 50 ml
of hot water, 20 ml of 80% methanol, and dried.
meso-Tetraphenyltetrabenzoporphyrin–er-
bium–octa-4,5-pentoxyphthalocyanine (IX). Into a
solution of lithium 1-pentanolate obtained by dissolv-
ing 0.1 g of lithium in 30 ml of 1-pentanol was added
0.2 g (0.7 mmol) of 4,5-dipentoxyphthalonitrile (X),
the solution was brought to boiling and boiled for 3 h.
To the formed solution of dilithium (4,5-octapentoxy)
phthalocyanine (XI) was added 0.1 g of complex II,
and the mixture was boiled for 2 h more. The reaction
mixture was cooled, diluted with 50 ml of water, and
extracted with 20 ml of chloroform. The extract was
washed with water, the organic layer was separated
and dried. The residue was dissolved in toluene and
chromatographed on a column packed with aluminum
oxide of the II degree of activity. At the elution the
second green zone was collected. Yield 0.12 g (57%),
green wax-like substance, well soluble in toluene,
chloroform, sparingly soluble in acetone, DMF. EAS,
Complexes of sandwich type VI–VIII. General
procedure. A mixture of 0.05 g of complex II and 0.5 g
of phthalodinitrile or its substituted derivative was heated
at 280°C over 1 h, then the mixture was cooled, ground,
washed with hot 80% methanol, the residue was dissolved
in chloroform and chromatographed on a column packed
with aluminum oxide of the II degree of activity. At the
elution with chloroform the main (second) green zone
was collected.
meso-Tetraphenyltetrabenzoporphyrin–erbium–
phthalocyanine (VI) was obtained using phthalonitrile
(III). Yield 36 mg (52 %), dark-green powder, well
soluble in toluene, chloroform, acetone, DMF. EAS,
λ
max, nm (D/Dmax), in CHCl3: 695 (0.08), 660 (0.36),
λ
max, nm (D/Dmax), in CHCl3: 700 (1.00), 660 (0.79),
628 (0.22), 592 (0.14), 464 (1.00), 328 (0.53); in DMF
+ 1% N2H4·H2O: 695 (0.20), 623 (0.41), 463 (1.00), 333
(0.67). IR spectrum, ν, cm–1: 3066, 1664, 1464, 1433,
1352, 1335, 1269, 719, 703, 882, 616. Mass spectrum:
m/z 1490 [M]+. Found, %: C 74.28; H 3.66; N 11.01.
C92H52ErN12. Calculated, %: C 74.02; H 3.51; N 11.26.
645 (0.45), 633 sh, 598 (0.24), 463 (0.24), 422 (0.36),
398 (0.38), 346 (0.79); in DMF + 1% N2H4·H2O: 664
(0.26), 465 (0.40), 340 (1.00). IR spectrum, ν, cm–1:
3067, 2964, 2875, 1712, 1608, 1478, 1472, 1385, 1286,
1210, 1059, 875, 702. Mass spectrum: m/z 2179 [M]+.
Found, %: C 73.07; H 6.80; N 7.32. C132H132ErN12O4.
Calculated, %: C 72.67; H 6.10; N 7.70.
meso-Tetraphenyltetrabenzoporphyrin–erbium–
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