meso-phenyltetrabenzoazaporphyrins and their zinc complexes. Synthesis and spectral properties

Article abstract of DOI:10.1007/s11176-005-0289-8

Zinc complexes of meso-phenyltetrabenzoazaporphyrins were prepared by the reaction of iso-indoline-1,3-diimine with phenylacetic acid in the presence of zinc oxide. Treatment of the products with sulfuric acid gave metal-free compounds. 2005 Pleiades Publ

Full text of DOI:10.1007/s11176-005-0289-8

Russian Journal of General Chemistry, Vol. 75, No. 4, 2005, pp. 651 655. Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 4, 2005,
pp. 689 693.
Original Russian Text Copyright
2005 by Galanin, Kudrik, Shaposhnikov.
meso-Phenyltetrabenzoazaporphyrins
and Their Zinc Complexes. Synthesis and Spectral Properties
N. E. Galanin, E. V. Kudrik, and G. P. Shaposhnikov
Ivanovo State University of Chemical Technology, Ivanovo, Russia
Received November 12, 2003
Abstract Zinc complexes of meso-phenyltetrabenzoazaporphyrins were prepared by the reaction of iso-
indoline-1,3-diimine with phenylacetic acid in the presence of zinc oxide. Treatment of the products with
sulfuric acid gave metal-free compounds.
Tetrabenzoazaporphyrins occupy an intermediate
place between tetrabenzophorphyrin and phthalo-
cyanine. These compounds present a theoretical in-
terest and can be applied as, for example, phototrans-
ducers [1].
in the presence of magnesium oxide gives rise to
magnesium complexes of meso-phenyltetrabenzo-
azaporphyrins [2]. The present work is a continuation
of the research into synthesis and spectral properties
of meso-phenyltetrabenzoazaporphyrins and their zinc
complexes. Zinc meso-phenyltetrabenzoazaporphyrins
II V were synthesized by the reaction of compound I
with phenylacetic acid in the presence of zinc oxide
by the following scheme.
Previously we showed that template condensation
of isoindoline-1,3-diimine (I) with phenylacetic acid
Ph
Ph
Ph
Ph
N
N
N
NH
NH
NH
N
N
PhCH2CO2H,
ZnO
Zn
N
+
Zn
N
N
N
N
N
Ph
I
II
III
Ph
Ph
N
N
N
N
N
N
Zn
N
+
Zn
N
+
N
N
N
N
N
Ph
IV
V
1070-3632/05/7504-0651 2005 Pleiades Publishing, Inc.

652
GALANIN et al.
D
0.8
D
0.4
2
0.6
0.4
0.2
0.3
0.2
0.1
2
1
1
400
500
600
700
800
, nm
400
500
600
700
, nm
Fig. 2. Electronic absorption spectra of (1) zinc meso-
cis-diphenyltetrabenzodiazaporphyrin (III) and (2) zinc
meso-trans-diphenyltetrabenzodiazaporphyrin (IV) in
toluene.
Fig. 1. Electronic absorption spectra of (1) zinc meso-tri-
phenyltetrabenzoprophyrin (V) and (2) zinc meso-tetra-
benzotriazaporphyrin (V) in toluene.
The mixture of zinc complexes II V was separated
by column chromatography on alumina. The com-
plexes were then dissolved in concentrated sulfuric
acid, and the solutions were left to stand for 2 h ay
room temperature to obtain metal-free compounds
VI VIII. It was found that metal complex V under
the synthesis conditions undergoes no demetalation,
but is sulfurized at higher temperatures and longer
exposure times. Purification of compounds VI VIII
was performed by column chromatography.
stituted phthalocyanines of the AABB type [3, 4]. Such
spectral changes can, to a first approximation, be ex-
plained in terms of the popular Gouterman’s model
[5]. According to this model, long-wave bands in the
electronic absorption spectra of porphyrins relate to
transitions of the a1u orbital to two perperdicular eg*
orbitals that, in D4h porphyrins (for instance, in their
metal complexes), are degenerate. In lower symmetry
porphyrins, these orbitals are no longer degenerate,
and the Q bond is split into two components of close
intensity. The magnitude of the splitting is highly
sensitive to the nature of the macroring and, according
to theoretical predictions, should be maximal in un-
symmetrically substituted porphyrazines of the ABAB
type and minimal in compounds of the AABB type.
It is this pattern that is observed in our case.
The purity of the products was confirmed by TLC,
and their composition and structures were established
1
by elemental analysis and H NMR and electronic
spectroscopy.
Compounds II VII were obtained as powders.
They are soluble in pyridine, DMF, DMSO, benzene,
chloroform, acetone, and concentrated sulfuric acid.
Comparison of the electronic absorption spectra of
zinc complexes II V with the spectra of known
magnesium meso-phenyltetrabenzoazaporphyrins [1]
shows that substitution of zinc for magnesium radi-
cally changes the spectral pattern. Thus, principal ab-
sorption bands of zinc complexes II, IV, and V are
shifted blue by 8 13 nm compared to respective bands
of magnesium complexes, except for cis isomer III.
In the latter case, considerable red shifts of absorption
bands compared to magnesium meso-trans-diphenyl-
tetrabenzodiazaporphyrin are observed (up to 26 nm
for the Soret band and 24 nm for the long-wave com-
ponent of the Q band). This observation is probably
explained by a stronger planarity disturbance in the
case of magnesium complexes because of the smaller
size of magnesium ion compared to zinc ion. As a
result, the HOMO energy increases, while the LUMO
energy changes only slightly, thereby shifting the ab-
sorption bands red. With compound III that has a
more planar structure, the opposite effect takes place.
Having two mutually perpendicular symmetry axes,
The electronic absorption spectra of metal com-
plexes II V (Figs. 1 and 2) characteristically display
both long-wave (703 644 nm, Q bands) and short-
wave bands (421 455 nm, B bands). The spectral
patterns, maxima positions, and relative intensity of
principal bands are much dependent of the number of
phenyl substituents. Thus in going from triphenyl-
substituted azaporphyrin II to monophenyl derivative
V, the relative intensity of the Q band increases, and
the spectral pattern gets closer to that of the metal
phthalocyanine. The band splitting is associated with
the lower symmetry of the macroring. In the case of
diphenyldiazaporphyrins, the spectra of the cis and
trans isomers are different from each other. Thus, the
Q band of trans isomer IV is split into two com-
ponents and strongly shifted red compared to that of
cis isomer III. The Q band of compound III is split
only slightly and has a shoulder at 664 nm. The same
pattern is also characteristic of unsymmetrically sub-
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meso-PHENYLTETRABENZOAZAPORPHYRINS
653
D
D
0.8
0.4
0.6
0.4
0.3
0.2
0.1
2
1
0.2
0
400
500
600
700
, nm
400
500
600
700
, nm
Fig. 4. Electronic absorption spectra of (1) meso-cis-
diphenyltetrobenzodiazaporphyrin (VII) and (2) meso-
trans-diphenyltetrobenzodiazaporphyrin (VIII) in toluene.
Fig. 3. Electronic absorption spectrum of meso-triphenyl-
tetrabenzoazaporphyrin (VI) in toluene.
this molecule is strongly polarized, which results in
splitting of the Q band into two components with their
maxima at 703 and 697 nm (Fig 2, spectrum 2). The
planarity disturbance of the molecule of magnesium
meso-trans-diphenyltetrabenzodiazaporphyrin renders
it less polarized, as a result of which the Q-band
maxima get closer together (679 and 652 nm).
spectrum of meso-cis-diphenyldiazaporphyrin (VII),
the signals of two endocyclic protons appear as two
singlets at 1.0 and 1.6 ppm. The appearance of two
proton signals in the latter case we relate to nonequi-
valence of the two endocyclic protons, associated with
the unsymmetrical structure of molecule VII. A
similar spectral pattern was previously observed with
an unsymmetrical porphyrazine of the AABB type,
containing 3,4-dicyano-1,2,5-thiadiazole and 2,3-di-
cyano-1,4-dipentoxyphthalodinitrile residues [3];
however, the spectrum of the latter compound, unlike
what is observed with compound VII, two endocyclic
proton signals appeared only on cooling of the CDCl3
solution to 58 C.
In going from zinc complexes II V to metal-free
compounds VI VIII, the spectral pattern becomes
more intricate (Figs. 3 and 4). Since the symmetry of
MOs is lowered, the Soret band is split into two com-
ponents, which is also characteristic of meso-substi-
tuted tetrabenzoporphyrins [6, 7]. With meso-triphe-
nyltetrobenzoazaporphyrin (VI), a red shift of absorp-
tion bands compared to diphenyl-substituted ligands
VII and VIII is observed. Like with metal complexes
III and IV, in the spectra of compounds VII and VIII,
the degree of band splitting decreases in going from
the trans to cis isomers. The general spectral patterns
of the ligands, unlike metal complexes, are similar to
those of meso-substituted tetrabenzoporphyrines. A
possible explanation for this fact is that metal com-
plexes of meso-phenyl-substituted tetrobenzoazapor-
phyrins are only slightly nonplanar, whereas metal-
free compounds, in the absence of the stabilizing
effect of the complexing metal, are much more dis-
torted. The ligands are close in geometry to meso-
substituted tetrabenzoporphyrins, which predetermines
the similarity of their electronic absorption spectra.
The gradual upfield shifting of endocyclic proton
signals with increasing number of aza groups can be
explained by enhancing rigidity and, consequently,
planarization of the azaporphyrin molecules.
EXPERIMENTAL
The electronic absorption spectra were measured
on a Hitachi UV-2000 spectrophotometer in toluene.
The 1H NMR spectra were obtained on a Bruker
AMD-300X spectrometer (300 MHz, TMS).
Isoindoline-1,3-diimine (I) was synthesized and
purified as described in [8].
Zinc complexes of meso-phenyl-substituted
tetrabenzoazaporphyrins II V. A mixture of 1.47 g
of isoindoline-1,3-diimine (I), 1.4 g of phenylacetic
acid, and 0.4 g of zinc oxide was placed into a quartz
tube and heated at 280 C for 1 h. The resulting melt
was cooled, ground, refluxed for 10 min in 100 ml of
20% KOH, filtered off, washed with water to neutral
washings, and dried. The residue was dissolved in
acetone and subjected to chromatography on a column
of alumina (activity grade II), eluent toluene acetone,
The 1H NMR spectra of the synthesized com-
pounds in DMSO-d6 contain two downfield multi-
plets at 8.6 7.5 and 8.0 7.0 ppm, assignable to
16 isoindole protons and phenyl protons, respectively.
In the spectra of metal-free compounds VI and
VIII, the signals of endocyclic protons (Fig. 5) appear
as singlets at 0.9 (VI) and 1.5 ppm (VIII). In the
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 75 No. 4 2005

654
GALANIN et al.
10.8. C46H26N6Zn. Calculated, %: C 75.9; H 3.6;
N 11.6.
Zinc meso-phenyltetrabenzotriazaporphyrin
(V). Yield 0.07 g (5%), Rf 0.26 (Silufol, chloroform).
Electronic absorption spectrum (toluene), max, nm
(D/Dmax): 669 (1.00), 645 (0.69), 597 (0.02), 440
1
(0.34), 425 (0.41). H NMR spectrum (DMSO-d6),
3
, ppm: 8.3 7.8 m (16H), 7.5 7.1 m (5H). Found, %:
C 72.3; H 4.5; N 14.8. C39H21N7Zn. Calculated, %:
C 71.8; H 3.2; N 15.1.
2
meso-Phenyl-substituted tetrabenzoazapor-
phyrins VI VIII. Zinc complex II V, 0.1 g, was dis-
solved in 50 ml of conc. H2SO4, and the solution was
left to stand at 20 C for 2 h, after which it was poured
into 100 ml of water. The precipitate that formed was
filtered off, washed with 100 ml of water and 50 ml of
10% ammonia, dried at 100 C, dissolved in acetone,
and subjected to column chromatography on alumina
(activity grade II) using as eluent toluene acetone,
10:1 (v/v), to isolate compounds VI VIII.
1
0.3
0.7
1.1
1.5
, ppm
meso-Triphenyltetrabenzoazaporphyrin (VI).
Yield 0.07 g (73%), Rf 0.78 (Silufol, chloroform).
Electronic absorption spectrum (toluene), max, nm
(D/Dmax): 674 (0.20), 626 (0.27), 611 (0.24), 577
1
Fig. 5. H NMR spectra of compounds (1) VI, (2) VII,
and (3) VIII in DMSO-d .
6
1
10:1. Therewith, four bands formed, that contained
zinc meso-triphenyltetrabenzoazaporphyrin (II), zinc
meso-cis-diphenyltetrabenzodiazaporphyrin (III), zinc
(0.13), 447 (1.00), 436 (0.86). H NMR spectrum
(DMSO-d6), , ppm: 8.6 8.2 m (16H), 8.0 7.2 m
(15H), 0.9 s (2H). Found, %: C 85.2; H 4.40; N 9.2.
C53H33N5. Calculated, %: C 86.1; H 4.5; N 9.5.
meso-trans-diphenyltetrabenzodiazaporphyrin
(IV),
and zinc meso-phenyltetrabenzotriazaporphyrin (V).
meso-cis-Diphenyltetrabenzobenzodiazapor-
phyrin (VII). Yield 0.06 g (62%), Rf 0.59 (Silufol,
chloroform). Electronic absorption spectrum (toluene),
max, nm (D/Dmax): 664 (0.40), 645 (0.50), 631 (0.49),
Zinc meso-triphenyltetrabenzoazaporphyrin
(II). Yield 0.14 g (11%), Rf 0.76 (Silufol, chloroform).
Electronic absorption spectrum (toluene), max, nm
1
437 (1.00), 423 (0.77), 389 (0.58). H NMR spectrum
(D/Dmax): 672 (0.24), 648 (0.90), 600 (0.02), 427
1
(DMSO-d6), , ppm: 8.2 7.6 m (16H), 7.5 7.1 m
(10H), 1.0 s (1H), 1.6 s (1H). Found, %: C 82.2; H
4.8; N 13.1. C46H28N6. Calculated, %: C 83.1; H 4.2;
N 12.7.
(1.00). H NMR spectrum (DMSO-d6), , ppm: 8.5
8.3 m (16H), 8.2 7.4 m (15H). Found, %: C 80.2; H
4.4; N 8.4. C53H31N5Zn. Calculated, %: C 79.3; H
3.9; N 8.7.
meso-trans-Diphenyltetrabenzodiazaporphyrin
(VIII). Yield 0.05 g (54%), Rf 0.54 (Silufol, chloro-
Zinc meso-cis-diphenyltetrabenzodiazapor-
phyrin (III). Yield 0.03 g (2.5%), Rf 0.55 (Silufol,
chloroform). Electronic absorption spectrum (toluene),
max, nm (D/Dmax): 664 (0.34), 644 (1.00), 587 (0.02),
form). Electronic absorption spectrum (toluene),
,
max
nm (D/Dmax): 666 (0.27), 619 (0.28), 611 (0.28), 603
(0.23), 569 (0.14), 436 (1.00), 422 (0.85), 394 (0.36).
1H NMR spectrum (DMSO-d6), , ppm: 8.1 7.7 m
(16H), 7.6 7.2 m (10H), 1.5 s (2H). Found, %: C
84.8; H 4.5; N 12.3. C46H28N6. Calculated, %: C
83.1; H 4.2; N 12.7.
1
421 (0.78). H NMR spectrum (DMSO-d6), , ppm:
8.3 7.6 m (16H), 7.5 7.2 m (10H). Found, %: C
76.4; H 4.1; N 11.2. C46H26N6Zn. Calculated, %: C
75.9; H 3.6; N 11.6.
Zinc meso-trans-diphenyltetrabenzodiazapor-
phyrin (IV). Yield 0.07 g (4.5%), Rf 0.53 (Silufol,
chloroform). Electronic absorption spectrum (toluene),
max, nm (D/Dmax): 703 (0.73), 667 (0.82), 455 (1.00).
1H NMR spectrum (DMSO-d6), , ppm: 8.1 7.8 m
(16H), 7.7 7.2 m (10H). Found, %: C 74.2; H 3.8; N
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