Porphyrazines of symmetric and unsymmetrical structure with fused fragments of 1,4-bis(2-phenoxyethoxy)benzene and 5,6-diphenylpyrazine. Synthesis and spectral characteristics

Article abstract of DOI:10.1134/S1070428009050066

By alkylation of 3,6-dihydroxyphthalonitrile with 1-bromo-2-phenoxyethane 3,6-bis(2-phenoxyethoxy) phthalonitrile was obtained. A random condensation of the nitrile with 2,3-dicyano-5,6-diphenylpyrazine in 1-butanol in the presence of lithium 1-butanolate porphyrazines were synthesized of symmetric and unsymmetrical structure, and their spectral characteristics were investigated.

Full text of DOI:10.1134/S1070428009050066

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2009, Vol. 45, No. 5, pp. 681−686. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © N.E. Galanin, G.P. Shaposhnikov, 2009, published in Zhurnal Organicheskoi Khimii, 2009, Vol. 45, No. 5, pp. 699−704.
Porphyrazines of Symmetric and Unsymmetrical Structure
with Fused Fragments of 1,4-Bis(2-phenoxyethoxy)benzene
and 5,6-Diphenylpyrazine. Synthesis and Spectral Characteristics
N. E. Galanin and G. P. Shaposhnikov
Ivanovo State University of Chemical Engineering, Ivanovo, 153000 Russia
e-mail: ttoc@isuct.ru
Received July 8, 2008
Abstract—By alkylation of 3,6-dihydroxyphthalonitrile with 1-bromo-2-phenoxyethane 3,6-bis(2-phenoxy-
ethoxy)phthalonitrile was obtained. Arandom condensation of the nitrile with 2,3-dicyano-5,6-diphenylpyrazine
in 1-butanol in the presence of lithium 1-butanolate porphyrazines were synthesized of symmetric and unsymmetrical
structure, and their spectral characteristics were investigated.
DOI: 10.1134/S1070428009050066
I was performed from 1-bromo-2-phenoxyethane (III),
obtained in its turn by the reaction of phenol (IV) with
excess 1,2-dibromoethane in DMF in the presence of
K2CO3.
One of the most promising groups of tetrapyrrole
macrocyclic compounds is the porphyrazines of unsym-
metrical structure. Due to the presence of pronounced
dipole moments these compounds are obviously interesting
for application to the nonlinear optics [1–3], and the
existing functional groups of various character make it
possible to use the unsymmetrical porphyrazines in the
medicine, in particular, for photodynamic therapy of the
cancer diseases [4–7]. The synthesis of such porphyr-
azines most often consists in the random condensation of
two different nitriles of aromatic ortho-dicarboxylic acids
in the presence of a template agent [8–10]. As a result a
mixture of all possible porphyrazines is obtained that
according to the common classification belong to the
following types: A4, A3B, AABB, ABAB, AB3, and B4,
where A and B are various peripheral fragments in
porphyrazine molecules. In contrast to symmetric
porphyrazines their analogs of unsymmetrical structure
are relatively poorly studied group because of the
difficulties arising in their preparation, isolation, and
purification.
1
2
OH
OCH2CH2Br
K2CO3, DMF
+ BrCH2CH2Br
IV
III
Compound III is a viscous light-yellow fluid well
soluble in organic solvents. Its composition and structure
were confirmed by elemental analysis, vibrational and
1H NMR spectra. In the IR spectrum of compound III
the following absorption bands were observed: at 1125
and 1186 cm–1 (νC–O–C), strong band at 2911 cm–1 (νC–H),
a band at 672 cm–1 (νC–Br). In the 1H NMR spectrum of
compound III a multiplet appeared in the region 7.11–
6.98 ppm corresponding to five protons of the benzene
ring; the multiplet at 4.32 ppm belonged to two protons
of the methylene group in the position 2, and the multiplet
at 3.68 ppm, to two protons of the methylene group in
the position 1.
We report here on the random condensation of 3,6-
bis(2-phenoxyethoxy)phthalonitrile (I) with 2,3-dicyano-
5,6-diphenylpyrazine (II) in 1-butanol in the presence of
lithium 1-butanolate affording porphyrazines of symmetric
and unsymmetrical structure (A4, A3B, AABB, ABAB,
AB3), and also on the investigation of the spectral
characteristics of compounds. The synthesis of compound
Nitrile I was obtained by the reaction of compounds
III with 3,6-dihydroxyphthalonitrile (V) in the presence
of K2CO3 in DMF.
681

GALANIN, SHAPOSHNIKOV
OCH2CH2Br
682
OH
OCH2CH2OPh
CN
CN
CN
K2CO3, DMF
+
CN
OH
OCH2CH2OPh
III
I
V
R = PhOCH2CH2
Compound I is a light-gray powder well soluble in
organic solvents. Its composition and structure were con-
firmed by elemental analysis, vibrational spectra, 1H NMR,
and mass spectra. In the IR spectrum of nitrile I
a multiplet in the region 7.09–6.98 ppm from the 40 protons
of the eight phenoxy groups, and a multiplet in the region
4.58–4.33 ppm belonging to the 32 protons of the methyl-
ene groups of the eight phenoxyethoxy substituents. The
signal from two protons of the endocyclic imino groups
was observed at 0.26 ppm.
absorption bands were observed at 2232 (νC N), 1127,
≡
and 1188 (νC–O–C), 2933 cm–1 (νC–H). The 1H NMR spec-
trum of compound I contained a singlet at 7.82 ppm
belonging to two protons in positions 4 and 5 of the
phthalonitrile fragment; the multiplet in the region 7.01–
6.82 ppm corresponded to the resonance of the 10 protons
of the phenoxy groups, and the multiplet in the region
4.95–4.36 ppm originated from eight protons of the four
methylene groups. In the mass spectrum of compound I
(ionization by electron impact) peak of molecular ion,
m/z 400 [M]+, was observed, and also peaks of its
fragmentation products: m/z 371 [M – HCN]+, 320 [M –
Ph + 3]+ and 152 [M – 2C2H4OPh + 6]+.
1
In the H NMR spectrum of compound VII (A3B)
multiplets were observed from 10 protons of the phenyl
substituents in the pyrazine fragments in the region 7.88–
7.73 ppm, from six protons of benzene rings of the
isoindole fragments in the region 7.28–7.21 ppm, from
30 protons of the six phenoxy groups in the region 7.10–
7.01 ppm, and from 24 protons of the 12 methylene groups
in the region 4.62–4.34 ppm. The signal from two protons
of the endocyclic imino groups was shifted upfield to
–0.3 ppm.
1H NMR spectra of compounds VIII–X by their
character and signals position resemble the spectrum of
porphyrazine VII and differ mainly in the increase in the
relative intensity of the proton signals of the phenyl
substituents from the pyrazine fragments and in the
decrease in the intensity of the methylene groups signals.
Besides, with the growing number of the acceptor
fragments of the diphenylpyrazine in the compounds
series VII > VIII, IX > X the proton signals from the
endocyclic imino groups shift upfield due to the growing
aromaticity of porphyrazines in this series.
The heating of a mixture of nitrile I and 5,6-diphenyl-
pyrazine-2,3-dicarbonitrile (II) prepared by procedure
[11] in boiling 1-butanol in the presence of lithium 1-butano-
late followed by the treatment with acetic acid resulted
in the formation of a mixture of tetra[1,4-bis(2-phenoxy-
ethoxy)benzo]porphyrazine (VI), tri[1,4-bis(2-phenoxy-
ethoxy)benzo](5,6-diphenylpyrazino)porphyrazine (VII),
cis-di[1,4-bis-(2-phenoxyethoxy)benzo]di(5,6-di-
phenylpyrazino)porphyrazine (VIII), trans-di[1,4-bis(2-
phenoxyethoxy)benzo]di(5,6-diphenylpyrazino)-
porphyrazine (IX), mono[1,4-bis(2-phenoxyethoxy)-
benzo]tri(5,6-diphenylpyrazino)porphyrazine (X), and
tetra-(5,6-diphenylpyrazino)porphyrazine (XI). From the
mixture compounds VI–X were isolated by column
chromatography.
Electronic spectra of porphyrazines VI–X are
characterized by a strong absorption in the (Q bands)
and near UV region (B bands) (π–π* transitions). In
the electron absorption spectrum of compound VI (A4)
(Fig. 1, 1) the Q band has a maximum at 737 nm;
Porphyrazines VI–X are green crystalline substances
well soluble in benzene, chloroform, and acetone. Their
composition and structure were confirmed by elemental
therewith
like
in
the
case
of
3,6-
octaalkoxyphthalocyanines [12, 13] the band is virtually
nonsplit, only a small inflection is observed in the region
664 nm. As should be expected, the presence of eight
phenoxyalkoxy substituents in the molecule of compound
VI led to a significant (~40 nm) red shift of the longwave
Q band as compared to its position in the spectrum of the
1
analysis, 1H NMR , and electronic spectra. The H NMR
spectrum of compound VI (A4) in the region 7.22–7.13
ppm contained a multiplet corresponding to the eight
protons of the benzene rings of the isoindole fragments,
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PORPHYRAZINES OF SYMMETRIC AND UNSYMMETRICAL STRUCTURE
683
this band in the spectrum of compound VI is a weak
broadened band
unsubstituted phthalo-cyanine. This shift is caused by a
strong enhancement of the HOMO energy due to a
significant contribution of the atomic orbitals of the carbon
atoms in the positions 3 and 6 of isoindole fragments
[14]. The B band has a maximum at 340 nm, and alongside
In the electronic spectrum of porphyrazine VII (A3Β)
(Fig. 1, 2) the Q band is split in two components with the
maxima at 713 and 693 nm, besides a shoulder is observed
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GALANIN, SHAPOSHNIKOV
684
Fig. 3. Electron absorption spectra of compound IX. (1) in
Fig. 1. Electron absorption spectra in CHCl3 solution: (1) of
CHCl3, (2) in a mixture CHCl3–NHEt2
compound VI, (2) of compound VII.
the semiempirical method AM1 their dipole moments
grew in the series 1.69, 4.64, and 5.03 D respectively
supporting the above assumption.
The acidity of alkyl-substituted tetrapyrazinoporphyr-
azines is known to be considerably higher than that of
phthalocyanine [16]. The increase in the number of
electron-acceptor fragments in the molecules of porphyr-
azines VII–X also enhances their acidity, therefore on
the addition of bases their electronic spectra should
change because of the dianions formation. The addition
of 10% of diethylamine to the solutions of compounds VI
and VII in chloroform did not change the pattern of their
electron absorption spectra due to their insufficient acidity.
However the addition of 10% of diethylamine to the
solution of compound VIII in chloroform resulted in the
formation of its dianion, and in the electronic spectrum
(Fig. 2, 2) a decreased splitting of the Q band was
observed due to the increased symmetry of the molecular
orbitals, but the position of the maxima of the main
absorption bands remained virtually unchanged.
Fig. 2. Electron absorption spectra of compound VIII. (1) in
CHCl3, (2) in a mixture CHCl3–NHEt2.
in the region 657 nm. The three-band spectral character
in the longwave region is one of the characteristic
features of the metal-free porphyrazines A3Β; therewith
the most longwave component of the Q-band as well as
the band in the region 426 nm correspond to the charge
transfer from the donor part of the molecule to the
acceptor one [15].
The electron absorption spectrum of porphyrazine IX
(AΒAΒ) (Fig. 3, 1) in its character and the maxima
positions of the main absorption is analogous to the
spectrum of bands compound VIII, but the intensity of
the shortwave component of the Q band is enhanced in a
good agreement with the four-orbital Gouterman model
[17]. In the electron absorption spectrum of the dianion
of compound IX (Fig. 3, 2) two components of the Q
band with the maxima at 669 and 639 nm merge into one
band with a maximum at 660 nm, and the charge transfer
band that in the spectrum of porphyrazine IX is observed
in the region 718 nm suffers a red shift to 733 nm.
In the electronic spectrum of compound VIII (AAΒΒ)
(Fig. 2, 1) the Q band is split in two components with the
maxima at 669 and 638 nm, besides on its longwave wing
an inflection is observed at 688 nm (charge transfer band).
The B band suffers a red shift compared with its positions
in the spectra of compounds VI and VII by 20 and 9 nm
respectively due apparently to the increased dipole
moment of compound VIII. Actually, according to the
quantum-chemical calculations of molecules VI–VIII by
As to the electron absorption spectrum of porphyrazine
X (AΒ3) (Fig. 4, 1), its Q band is split into two
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PORPHYRAZINES OF SYMMETRIC AND UNSYMMETRICAL STRUCTURE
685
components of equal intensity with the maxima at 667
and 640 nm. Note the considerable growth of the relative
intensity of the B band. Whereas in the spectrum of
porphyrazine VII (A3Β) the intensity ratio of Q and B
bands is 1:1.01, in the spectrum of compound X (AΒ3) it
changes to 1:2.58. The reason of it is evidently the
significant decrease in the energy of the vacant orbitals
B3u and B2u under the effect of the electron-acceptor
fragments of diphenylpyrazine. The electron absorption
spectrum of the dianion of compound X (Fig. 4, 2) contains
a Q band with a maximum at 657 nm.
EXPERIMENTAL
Electron absorption spectra of compounds obtained
were measured on a spectrophotometer Hitachi UV-2001,
1H NMR spectra in CDCl3 solution, on a spectrometer
Bruker AMD-200 (200 MHz, internal reference TMS),
IR spectra, on a spectrophotometer Avatar 360 FT-IR in
the region 400–4000 cm–1 from thin films. Mass spectra
were registered on a GC-MS instrument Varian Saturn
2000R. Elemental analysis was performed on a FlashEA
1112 CHNS–O Analyzer.
Fig. 4. Electron absorption spectra of compound X. (1) in
CHCl3, (2) in a mixture CHCl3–NHEt2
(electron impact, 70 eV), m/z (Irel, %): 400 [M]+ (12),
371 [M – HCN]+ (10), 320 [M – Ph + 3]+ (54), 152 [M –
2C2H4OPh + 6]+ (100). Found, %: C 72.22; H 5.11;
N 6.63.C24H20N2O4. Calculated, %: C 71.99; H 5.03;
N 7.00.
Condensation of 3,6-bis(2-phenoxyethoxy)-
phthalonitrile (I) with 5,6-diphenylpyrazine-2,3-di-
carbonitrile (II). Into a solution of lithium butanolate
prepared by dissolving 0.2 g of lithium in 30 ml of
anhydrous 1-butanol was charged 0.4 g (1.0 mmol) of
compound I, 0.3 g (1.0 mmol) of compound II, and the
mixture was refluxed for 3 h. The reaction mixture was
cooled, 10 ml of acetic acid and 20 ml of water was
added, the separated precipitate was filtered off, washed
on the filter with 10 ml of methanol, and dried. The product
was dissolved in benzene and was subjected to chromato-
graphy on a column packed with silica gel 60 (eluent
benzene−chloroform–acetone, 50:20:1 by volume). The
product divided into 5 zones. On removing the solvent
compounds VI–X were obtained.
1-Bromo-2-phenoxyethane (III). A mixture of
3.1 g (0.03 mol) phenol (IV), 18.6 g (0.1 mol) of 1,2-di-
bromoethane, 7.0 g of K2CO3, and 40 ml of DMF was
stirred at reflux for 8 h, then it was poured into 200 ml of
water. The organic layer was separated, washed with
10% solution of HCl and water, then excess 1,2-di-
bromoethane was distilled off in a vacuum. The residue
was subjected to column chromatography of alumina of
the II grade of activity (eluent chloroform) collecting
the light-yellow zone. Yield 4.5 g (67%), light-yellow
viscous fluid, soluble in benzene, chloroform, acetone.
IR spectrum, ν, cm–1: 2911, 1524, 1401, 1186, 1125, 813,
1
672. H NMR spectrum, δ, ppm: 7.11–6.98 m (5H), 4.32
m (2H), 3.68 m (2H). Found, %: C 47.79; H 4.51.
C8H9BrO. Calculated, %: C 48.01; H 4.95.
Tetra[1,4-bis(2-phenoxyethoxy)benzo]porphyr-
azine (VI) (A4). Yield 0.04 g (10%), green powder, well
soluble in benzene, chloroform, insoluble in water.
Electron absorption spectrum (CHCl3), λmax, nm (D/
3,6-Bis(2-phenoxyethoxy)phthalonitrile (I).
A mixture of 2.0 g (10 mmol) of compound III, 0.8 g
(5 mmol) of 3,6-dihydroxyphthalonitrile (V), 5.0 g of
K2CO3, and 20 ml of DMF was stirred for 12 h at 120°C,
then it was poured into 100 ml of water. The separated
precipitate was filtered off, washed with water, with
methanol, and dried. Yield 1.3 g (65%), light-gray powder,
soluble in benzene, chloroform, acetone, sparingly soluble
in methanol. IR spectrum, ν, cm–1: 2933, 2232, 1529, 1403,
D
max): 737 (1.00), 664 sh, 431 sh, 340 (0.67). 1H NMR
spectrum, δ, ppm: 7.22–7.13 m (8H), 7.09–6.98 m (40H),
4.58–4.33 m (32H), 0.26 s (2H). Found, %: C 72.02;
H 5.61; N 6.13. C96H82N8O16. Calculated, %: C 71.90;
H 5.15; N 6.99.
1
1188, 1127, 847. H NMR spectrum, δ, ppm: 7.82 s (2H),
Tri[1,4-bis(2-phenoxyethoxy)benzo](5,6-di-
phenylpyrazino)porphyrazine (VII) (A3B). Yield
7.01–6.82 m (10H), 4.95–4.36 m (8H). Mass spectrum
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 45 No. 5 2009

GALANIN, SHAPOSHNIKOV
686
0.06 g (12%), green powder, well soluble in benzene,
chloroform, insoluble in water. Electron absorption spec-
trum (CHCl3), λmax, nm (D/Dmax): 713 (0.94), 693 (0.91),
7.23 m (2H), 7.14–7.11 m (10H), 4.55–4.48 m (8H),
–1.88 s (2H). Found, %: C 75.04; H 4.33; N 15.44.
C78H52N14O4. Calculated, %: C 74.99; H 4.20; N 15.70.
1
657 sh, 426 (0.45), 349 (1.00). H NMR spectrum,
δ, ppm: 7.88–7.73 m (10H), 7.28–7.21 m (6H), 7.10–
7.01 m (30H), 4.62–4.34 m (24H), –0.31 s (2H). Found,
%: C 72.88; H 5.01; N 9.16. C90H72N10O12. Calculated,
%: C 72.76; H 4.88; N 9.43.
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cis-Di[1,4-bis(2-phenoxyethoxy)benzo]di(5,6-
diphenylpyrazino)porphyrazine (VIII) (AAΒB).Yield
0.09 g (13%), green powder, well soluble in benzene,
chloroform, insoluble in water. Electron absorption
spectrum, λmax, nm (D/Dmax) in CHCl3: 687 (0.72), 669
(1.00), 638 (0.65), 428 (0.49), 359 (0.95); in CHCl3 +
NHEt2: 685 (0.85), 668 (0.98), 356 (1.00). 1H NMR
spectrum, δ, ppm: 7.89–7.75 m (20H), 7.27–7.21 m (4H),
7.12–7.07 m (20H), 4.58–4.36 m (16H), –0.73 s (2H).
Found, %: C 74.13; H 4.88; N 11.99. C86H62N12O8.
Calculated, %: C 73.78; H 4.57; N 12.29.
trans-Di[1,4-bis(2-phenoxyethoxy)benzo]di-
(5,6-diphenylpyrazino)porphyrazine (IX) (AΒAB).
Yield 0.07 g (10%), green powder, well soluble in benzene,
chloroform, insoluble in water. Electron absorption
spectrum, λmax, nm (D/Dmax) in CHCl3: 718 (0.53), 669
(1.00), 638 (0.82), 609 (0.42), 590 (0.34), 427 (0.50), 358
(0.96); in CHCl3 + NHEt2: 741 (0.35), 659 (0.71), 625 sh,
345 (1.00). 1H NMR spectrum, δ, ppm: 7.88–7.73 m
(20H), 7.29–7.22 m (4H), 7.12–7.10 m (20H), 4.58–
4.48 m (16H), –0.75 s (2H). Found, %: C 74.33; H 4.49;
N 11.71. C86H62N12O8. Calculated, %: C 73.78; H 4.57;
N 12.29.
Mono[1,4-bis(2-phenoxyethoxy)benzo]tri(5,6-di-
phenylpyrazino)porphyrazine (X) (AΒ3). Yield 0.14 g
(11%), green powder, well soluble in benzene, chloro-
form, insoluble in water. Electron absorption spectrum,
λ
max, nm (D/Dmax) in CHCl3: 667 (0.39), 641 (0.39), 347
(1.00); in CHCl3 + NHEt2: 657 (0.48), 631 sh, 331 (1.00).
1H NMR spectrum, δ, ppm: 7.92–7.82 m (30H), 7.29–
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 45 No. 5 2009