Meso-trans-Diphenyldi(2-quinolyl)tetrabenzoporphine and its zinc complex: Synthesis and spectra

Article abstract of DOI:10.1134/S1070363206010282

(3-Oxoisoindolenyl)(3-oxoisoindolinylidene)phenylmethane and (3-oxoisoindolenyl)(3-oxoisoindolinylidene)(2-quinolyl)methane were prepared by condensation of phthalimide with phenylacetic acid or 2-methylquinoline, respectively, in the presence of zinc oxide. From these products, the zinc complex of meso-trans-diphenyldi(2-quinolyl)tetrabenzoporphine was prepared by two alternative pathways. Demetallation of this complex yielded free meso-trans-diphenyldi(2-quinolyl)tetrabenzoporphine. The spectra of the compounds prepared were examined. Pleiades Publishing, Inc. 2006.

Full text of DOI:10.1134/S1070363206010282

ISSN 1070-3632, Russian Journal of General Chemistry, 2006, Vol. 76, No. 1, pp. 148 152.
Pleiades Publishing, Inc., 2006.
Original Russian Text N.E. Galanin, E.V. Kudrik, G.P. Shaposhnikov, 2006, published in Zhurnal Obshchei Khimii, 2006, Vol. 76, No. 1, pp. 151 155.
meso-trans-Diphenyldi(2-quinolyl)tetrabenzoporphine
and Its Zinc Complex: Synthesis and Spectra
N. E. Galanin, E. V. Kudrik, and G. P. Shaposhnikov
Ivanovo State University of Chemical Engineering, pr. F. Engelsa 7, Ivanovo, 153460 Russia
e-mail: ttoc@isuct.ru
Received December 6, 2004
Abstract (3-Oxoisoindolenyl)(3-oxoisoindolinylidene)phenylmethane and (3-oxoisoindolenyl)(3-oxoiso-
indolinylidene)(2-quinolyl)methane were prepared by condensation of phthalimide with phenylacetic acid or
2-methylquinoline, respectively, in the presence of zinc oxide. From these products, the zinc complex of
meso-trans-diphenyldi(2-quinolyl)tetrabenzoporphine was prepared by two alternative pathways. Demetalla-
tion of this complex yielded free meso-trans-diphenyldi(2-quinolyl)tetrabenzoporphine. The spectra of the
compounds prepared were examined.
DOI: 10.1134/S1070363206010282
meso-Substituted tetrabenzoporphyrins and their
metal complexes exhibit a set of valuable properties.
Some of this compounds, being readily soluble in
low-polarity organic solvents, can be used as fat-
soluble dyes [1]. The same compounds were tested as
photochromic filters [2] and showed better perform-
ance than the commercial samples. The possibility of
using metal complexes of meso-tetraphenyl-substi-
tuted tetrabenzoporphines as photosensitizers for the
generation of singlet oxygen was examined. It was
shown [3, 4] that these compounds substantially sur-
pass in their properties hematoporphyrin used for
photodynamic cancer therapy.
meso-tetraaryltetrabenzoporphines is stepwise conden-
sation of phthalimide with compounds that are sources
of meso-C atoms [7]. Not only arylacetic acids can
be used as such compounds, but also aromatic com-
pounds with the methyl group exhibiting increased
CH acidity, e.g., 2-methylquinoline (II) [8].
Heating of phthalimide (I) with phenylacetic acid
(III) in the presence of ZnO for 30 min at 240 C,
followed by treatment with HCl, yields (3-oxoisoindo-
lenyl)(3-oxoisoindolinylidene)phenylmethane IV.
Compound IV after chromatographic purification on
alumina is a red crystalline powder readily soluble in
various organic solvents. Its structure was determined
by elemental analysis and spectroscopy (electronic,
Thus, meso-substituted tetrabenzoporphines de-
serve more comprehensive studies, both basic and
applied. Such studies, however, are restricted by prob-
lems with the synthesis and purification of meso-
substituted tetrabenzoporphyrins.
1
IR, H and 13C NMR).
CH2COOH
O
O
Ph
(1) ZnO;
(2) HCl
The most frequently used method for preparing
metal complexes of meso-aryl-substituted tetrabenzo-
porphyrins is high-temperature template condensation
of phthalimide (I) with arylacetic acid in the presence
of a source of a complexing metal, suggested in [5].
This method is especially convenient for preparing
symmetrically substituted meso-tetraaryltetrabenzo-
porphines [6].
O
N
NH +
NH
I
III
O
IV
The electronic absorption spectrum of IV (Fig. 1)
in the visible range consists of three bands at 523,
489, and 458 nm. Comparison of this spectrum with
that of (3-oxoisoindolenyl)(3-oxoisoindolinylidene)-
methane [9] shows that introduction of the phenyl
substituent leads to a hypsochromic shift of the ab-
sorption bands by 25 nm, apparently caused by the
distortion of the planar structure of IV due to steric
However, it is not appropriate to use this method
for preparing unsymmetrically substituted meso-tetra-
aryltetrabenzoporphines, which are of doubtless inter-
est. Joint condensation of phthalimide with two aryl-
acetic acids yields a mixture of six porphyrins whose
preparative separation is very difficult. The best route
to metal complexes of unsymmetrically substituted
148

meso-trans-DIPHENYLDI(2-QUINOLYL)TETRABENZOPORPHINE
149
effect of the phenyl substituent. The IR spectrum of
IV contains absorption bands at 1766 and 1726 cm ,
The m-H atoms of the phenyl substituent give rise to
a triplet at 7.59 7.52 ppm. Eight H atoms of the iso-
indole fragments give rise to a multiplet at 7.50
7.13 ppm.
1
characteristic of C=O groups. The bands at 1363 and
1
1288 cm are due to C=N stretching vibrations, and
1
the band at 3181 cm , to N H stretching vibrations.
We found that heating of phthalimide (I) with ex-
cess 2-methylquinoline (II) in the presence of ZnO
yields (3-oxoisoindolenyl)(3-oxoisoindolinylidene)(2-
quinolyl)methane (V) via intermediate formation of
3-(2-quinolylmethylidene)phthalimidine (VI):
1
In the H NMR spectrum of IV, the lowest field sig-
nal is a broadened singlet of the imide ring proton at
8.69 ppm. A multiplet of three o- and p-H atoms of
the phenyl substituent is observed at 7.81 7.62 ppm.
N
HC
O
N
I
N
I +
H2O
H2O
CH3
NH
NH
II
O
O
VI
V
Compound V was isolated from the reaction mix-
ture by column chromatography. A small amount of
VI was also isolated. The structures of these com-
pounds were determined by elemental analysis and by
1H, 13C NMR and electronic spectroscopy.
ing substituent and by distortion of the planarity of
the molecule.
1
The H NMR spectrum of V, measured in CDCl3,
contains a multiplet at 8.32 8.07 ppm corresponding
to three protons in positions 4, 6, and 8 of the 2-qui-
nolyl substituent. The multiplet at 8.06 7.77 ppm cor-
responds to the resonance of three protons in positions
3, 5, and 7 of the meso substituent. The signals of
eight protons of the isoindole fragments are observed
at 7.70 7.40 ppm. The singlet at 10.21 ppm belongs
to the N H proton.
Compound VI is a light yellow crystalline sub-
1
stance readily soluble in organic solvents. In its H
NMR spectrum recorded in DMSO-d6, the lowest
field signal is the broadened singlet of the NH proton
at 11.36 ppm, and the highest field signal is the sin-
glet of the exocyclic CH group at 6.95 ppm. The
doublet at 8.40 8.35 ppm belongs to the p-CH proton
(relative to the N atom) of the quinolyl substituent,
and the doublet at 7.66 7.62 ppm, to the m-CH pro-
ton. The multiplet at 8.20 7.70 ppm corresponds to
four protons of the benzene ring of the quinolyl sub-
stituent and four protons of the isoindole moiety.
Broadening of the NH proton signal suggests hydro-
gen bonding of this proton with the quinoline nitrogen
atom.
The zinc complex of meso-trans-diphenyldi(2-qui-
nolyl)tetrabenzoporphine (VII) was prepared by two
0.4
D
0.3
0.2
0.1
Compound V is a red substance, also soluble in
polar and nonpolar organic solvents. The electronic
absorption spectrum of V resembles that of IV and in
the visible range consists of three bands at 427, 454,
and 485 nm. Replacement of the phenyl substituent
in (3-oxoisoindolenyl)(3-oxoisoindolinylidene)phenyl-
methane (IV) by the 2-quinolyl substituent leads to a
hypsochromic shift of the bands by 31 38 nm, which
is caused both by the effect of the electron-withdraw-
450
500
550
600
, nm
Fig. 1. Electronic absorption spectrum of IV in chloro-
form.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 76 No. 1 2006

150
GALANIN et al.
alternative pathways: heating of IV with excess
2-methylquinoline and ZnO or heating of V with ex-
cess phenylacetic acid and ZnO at 280 C for 30 min.
In both cases, we obtained the desired porphyrin VII:
N
ZnO
ZnO
N
II + IV
III + V
N
Zn
N
N
N
VII
[meso-trans-Diphenyldi(2-quinolyl)tetrabenzopor-
phinato]zinc VII in both cases was isolated from the
reaction mixture and purified by column chromatog-
raphy on alumina. Treatment of its solution in chloro-
form with HCl yielded meso-trans-diphenyldi(2-qui-
nolyl)tetrabenzoporphine (VIII). Porphyrins VII and
VIII are dark green powders readily soluble in polar
and nonpolar organic solvents and insoluble in water
and aqueous acids and alkalis.
electronic absorption spectrum of VII (Fig. 2, curve 1)
exhibits the Soret band at 465 nm and the Q band at
655 nm. Comparison of this spectrum with that of
(meso-tetraphenyltetrabenzoporphinato)zinc [6] shows
that replacement of two phenyl substituents by 2-qui-
nolyl substituents causes a bathochromic shift of the
Soret band by 7 nm and of the Q band by 4 nm. This
shift may be caused by stronger steric distortion of the
molecule of VII due to the larger volume of the quino-
lyl substituents, and also by polarization of this mole-
cule due to the presence of donor and acceptor substit-
uents.
The structures of VII and VIII were determined by
elemental analysis, electronic and vibrational spectros-
copy, and mass spectrometry (field desorption). The
IR spectra of VII and VIII are largely similar and con-
tain bands at 2980 2921 (C H), 1388 1370 (C=N),
As for metal-free porphyrin VIII (Fig. 2, curve 2),
the Soret band in its spectrum is observed at 449 nm,
and the Q band is split (635 and 680 nm).
1
and 1048 1037 cm (C=C). Also, the spectrum of
VIII contains a broadened band in the range 3333
3345 cm characterizing the N H vibrations. The
As compared to the spectrum of meso-tetraphenyl-
tetrabenzoporphine, in the spectrum of VIII the Soret
band and the long-wave component of the Q band are
shifted hypsochromically by 16 and 18 nm, respec-
tively, whereas the position of the short-wave compo-
nent of the Q band remains unchanged (635 nm). We
believe that this trend is due to major distortion of
the molecule of VIII, with a certain decrease in the
aromaticity of the macrocycle, caused by additional
asymmetry of the molecule and increase in the size
of substituents in going from meso-phenyl to meso-
quinolyl groups without stabilizing effect of the com-
plexing metal.
1
D
0.8
2
1
0.6
0.4
0.2
0
2
1
EXPERIMENTAL
400
500
600
700
, nm
The electronic absorption spectra were recorded on
a Hitachi UV-2000 spectrophotometer, and the IR
spectra, on an Avatar-360-FT-IR spectrophotometer in
Fig. 2. Electronic absorption spectra of (1) VII and
(2) VIII in chloroform.
1
1
the range 400 4000 cm in KBr. The H (300 MHz,
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 76 No. 1 2006

meso-trans-DIPHENYLDI(2-QUINOLYL)TETRABENZOPORPHINE
151
TMS) and 13C (75 MHz) NMR spectra were taken
on a Bruker AMD-300X spectrometer, and the mass
spectra, on a JEOL JMS-700 mass spectrometer.
NMR spectrum (DMSO-d6), , ppm: 11.36 s (1H),
8.40 8.35 d (1H), 8.20 7.70 m (8H), 7.66 7.62 d
(1H), 6.95 s (1H). 13C NMR spectrum (DMSO-d6),
C, ppm: 169.25, 167.87, 155.79, 147.32, 138.60,
137.67, 134.30, 132.61, 130.31, 128.58, 127.75,
126.38, 123.26, 121.03, 102.41. The compound is
readily soluble in benzene, acetone, chloroform, and
DMF and insoluble in water. Found, %: C 79.55; H
4.60; N 10.42. C18H12N2O. Calculated, %: C 79.40;
H 4.44; N 10.29.
(3-Oxoisoindolenyl)(3-oxoisoindolinylidene)phen-
ylmethane (IV). A mixture of 6 g of phthalimide I,
2.5 g of phenylacetic acid (III), and 1.6 g of zinc oxide
was kept for 30 min at 240 C, after which the melt
was cooled, ground, and boiled in 100 ml of 10% HCl
for 5 min. The precipitate was filtered off and washed
on the filter with 200 ml of hot water. The dried pre-
cipitate was dissolved in chloroform and chromato-
graphed on a column packed with alumina (Brock-
mann grade II, eluent chloroform). The main bright
red band was collected; the solvent was removed.
A dark red powder of IV was obtained; yield 1.6 g
(25%). Electronic absorption spectrum (chloroform),
max, nm (D): 523 (0.134), 489 (0.158), 458 (0.156).
[meso-trans-Diphenyldi(2-quinolyl)tetrabenzo-
porphinato]zinc VII. a. A mixture of 1 g of IV, 5 ml
of 2-methylquinoline, and 0.2 ml of ZnO was heated
to 280 C and kept at this temperature for 30 min. The
melt was cooled, ground, and chromatographed on a
column packed with alumina (eluent chloroform); the
green band was collected. After removing the solvent,
the residue was chromatographed again with chloro-
form hexane (1 : 1 by volume) as eluent. The main
green band was collected, the solvent was removed,
and compound VII (0.25 g, 18%) was obtained as a
dark green powder readily soluble in benzene, chlo-
roform, acetone, and DMF and insoluble in water.
Electronic absorption spectrum (CHCl3), max, nm
(D/Dmax): 655 (0.49), 609 (0.38), 465 (1.00). IR spec-
1
IR spectrum, , cm (KBr): 3181 (NH), 2920 (CH),
1766, 1726 (C=O), 1363, 1288 (C=N), 778, 616, 582.
1H NMR spectrum (CD2Cl2), , ppm: 8.69 s (1H),
7.81 7.62 m (3H), 7.59 7.52 t (2H), 7.50 7.13 m
(8H). 13C NMR spectrum (CD2Cl2), C, ppm: 138.99,
136.15, 135.68, 135.60, 134.73, 133.63, 130.71,
129.86, 129.67, 128.13, 123.88, 120.16, 112.30,
106.46. The product is readily soluble in DMF, chlo-
roform, benzene, and acetone and insoluble in water
and in dilute acids and alkalis. Found, %: C 79.25; H
4.10; N 7.85. C23H14N2O2. Calculated, %: C 78.84;
H 4.03; N 8.00.
1
trum (KBr), , cm : 2955 (CH), 1376 (C=N), 1041
(C=C). Mass spectrum, m/z: 979 [M + H]+. Found,
%: C 81.15; H 4.22; N 8.45. C66H38N6Zn. Calculated,
%: C 80.96; H 3.91; N 8.59.
(3-Oxoisoindolenyl)(3-oxoisoindolinylidene)-
(2-quinolyl)methane (V). A mixture of 1 g of phthal-
imide I, 0.3 g of ZnO, and 10 ml of 2-methylquinoline
II was kept at the boiling point for 4 h. Then the mix-
ture was cooled and chromatographed on a column
packed with alumina (Brockmann grade II). Excess
2-methylquinoline was eluted with benzene hexane
(1 : 10 by volume), and the dark red band, with chlo-
roform hexane (1 : 2 by volume). After removing the
solvent, the residue was boiled for 5 min in 50 ml of
5% HCl. The solution was cooled, and the precipitate
was filtered off, dried, dissolved in chloroform, and
chromatographed on alumina (Brockmann grade II,
eluent chloroform). The main (second) red band was
collected. Compound VI (0.6 g) was obtained as a red
powder readily soluble in benzene, chloroform, ace-
tone, and DMF and insoluble in water. Electronic
absorption spectrum (CHCl3), max, nm (D): 485
b. A mixture of 0.5 g of V, 1 g of phenylacetic
acid (III), and 0.2 g of ZnO was heated to 280 C and
kept at this temperature for 30 min. The melt was
cooled, ground, and worked up as in method a. Yield
of VII 0.1 g (17%); the product is identical in proper-
ties to that obtained by method a.
meso-Diphenyldi(2-quinolyl)tetrabenzoporphine
VIII. A 0.1-g portion of VII was dissolved in 10 ml
of chloroform, 5 ml of concentrated HCl was added,
and the mixture was stirred for 1 h, after which 30 ml
of 25% ammonia was added. The organic layer was
separated and washed with water; the solvent was re-
moved. The residue was chromatographed on alumina
(Brockmann grade II, eluent chloroform). The solvent
was removed, and compound VIII (0.08 g, 82%) was
obtained as a dark green powder readily soluble in
benzene, chloroform, acetone, and DMF and insoluble
in water. Electronic absorption spectrum (CHCl3),
max, nm (D/Dmax): 680 (0.08), 635 (0.21), 449
(1.00), 404 (0.29), 384 (0.27). IR spectrum (KBr), ,
1
(0.40), 454 (0.27), 427 (0.22). H NMR spectrum
(CDCl3), , ppm: 10.21 s (1H), 8.32 8.07 m (3H),
8.06 7.77 m (3H), 7.70 7.40 m (8H). Found, %: C
78.01; H 4.01; N 10.03. C26H15N3O2. Calculated, %:
C 77.79; H 3.77; N 10.47.
1
cm : 3340 (NH), 2933 (CH), 1379 (C=N), 1038
(C=C). Mass spectrum, m/z: 917 [M + H]+. Found,
%: C 87.12; H 4.55; N 8.95. C66H40N6. Calculated,
%: C 86.43; H 4.40; N 9.17.
From the first pale yellow band, we isolated 0.05 g
1
of 3-(2-quinolylmethylidene)phthalimidine (VI). H
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GALANIN et al.
5. Kopranenkov, V.N., Dashkevich, S.N., and Luk’ya-
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