Synthesis and spectrophotometry study of the acid-base properties of nitro-substituted 5-phenyl-β-octaalkylporphines

Article abstract of DOI:10.1134/S1070363217080187

10,15-Dinitro-5-phenyl-2,3,7,8,12,13,17,18-octamethylporphine, 10,15,20-trinitro-5-phenyl-2,3,7,8,12,13,17,18-octamethylporphine, and 10,15,20-trinitro-5-(4-nitrophenyl)-2,3,7,8,12,13,17,18-octamethylporphine were synthesized and identified by electronic absorption, IR, and ¹Н NMR spectroscopy. The acid–base properties of the synthesized compounds were studied by spectrophotometric titration in HClO₄–acetonitrile and 1,8-diazabicyclo[5.4.0]undec-7-ene–acetonitrile systems at 298 K. Parameters of the electronic absorption spectra and concentration ranges of existence of the mono- and diprotonated, as well as mono- and dideprotonated forms of the corresponding ligands and the acid and base dissociation constants of the latter were determined. Comparative analysis of the effect of nitro groups on the reactivity of the synthesized compounds was performed.

Full text of DOI:10.1134/S1070363217080187

ISSN 1070-3632, Russian Journal of General Chemistry, 2017, Vol. 87, No. 8, pp. 1742–1751. © Pleiades Publishing, Ltd., 2017.
Original Russian Text © Yu.B. Ivanova, A.O. Plotnikova, A.P. Semeikin, T.V. Lyubimova, N.Zh. Mamardashvili, 2017, published in Zhurnal Obshchei
Khimii, 2017, Vol. 87, No. 8, pp. 1331–1341.
Synthesis and Spectrophotometry Study of the Acid-Base
Properties of Nitro-Substituted 5-Phenyl-β-Octaalkylporphines
Yu. B. Ivanovaa*, A. O. Plotnikovab, A. P. Semeikinb,
T. V. Lyubimovaa,b, and N. Zh. Mamardashvilia
a Krestov Solution Chemistry, Russian Academy of Sciences, ul. Akademicheskaya 1, Ivanovo, 153045 Russia
*e-mail: jjiv@yandex.ru
b Research Institute of Macroheterocyclic Chemistry, Ivanovo State University of Chemical Technology, Ivanovo, Russia
Received March 23, 2017
Abstract—10,15-Dinitro-5-phenyl-2,3,7,8,12,13,17,18-octamethylporphine, 10,15,20-trinitro-5-phenyl-
2,3,7,8,12,13,17,18-octamethylporphine, and 10,15,20-trinitro-5-(4-nitrophenyl)-2,3,7,8,12,13,17,18-octa-
methylporphine were synthesized and identified by electronic absorption, IR, and 1Н NMR spectroscopy. The
acid–base properties of the synthesized compounds were studied by spectrophotometric titration in HClO4–
acetonitrile and 1,8-diazabicyclo[5.4.0]undec-7-ene–acetonitrile systems at 298 K. Parameters of the electronic
absorption spectra and concentration ranges of existence of the mono- and diprotonated, as well as mono- and
dideprotonated forms of the corresponding ligands and the acid and base dissociation constants of the latter
were determined. Comparative analysis of the effect of nitro groups on the reactivity of the synthesized
compounds was performed.
Keywords: porphyrins, acid–base properties, 5-aryl-meso-nitro-β-octamethylporphyrin, 1,8-diazabicyclo[5.4.0]-
undec-7-ene
DOI: 10.1134/S1070363217080187
Tetrapyrrole pigments : porphyrins : play an excep-
tionally important role in animal, plant, and bacteria
lives. These brightly colored compounds comprise a
macroring including four pyrrole units. Metal com-
plexes of pophyrins fulfil key functions in photosyn-
thesis and the maintenance of human and animal life,
which explains the enduring interest in the structure
and synthesis of known and novel, peripherally modi-
fied, porphyrin ligands with desired properties [1–20].
However, targeted application of novel tetrapyrrole
compounds and their metal complexes in practice is
complicated by insufficient knowledge of the interrela-
tionship between the structure of porphyrins and their
complexing power with respect to metals [21, 22]. On
the one hand, acceptor or donor substitution in the
porphyrin macroring not infrequently leads to its
deformation due to electronic effects of the sub-
stituents, and this affects the coordination and acid–
base properties of the porphyrins [21]. On the other
hand, the activity of the ligands in such systems is
primarily dependent on the structure of the acid–base
complexes that form in solutions, because the ionizing
ability of such complexes depends on the degree of
electron transfer from the acid to base (solvent).
Systematic research in this field would allow building
up the knowledge of the reactivity of systems contain-
ing porphyrins and their molecular fragments having a
high chemical affinity to ions and molecules.
In the present work we synthesized 10,15-dinitro-5-
phenyl-2,3,7,8,12,-13,17,18-octamethylporphine 1,
10,15,20-trinitro-5-phenyl-2,3,7,8,12,-13,17,18-octa-
methylporphine 2, and 10,15,20-trinitro-5-(4-nitro-
phenyl)-2,3,7,8,12,13,17,18-octamethylporphine 3 and
performed a spectrophotometric study of their acid–
base properties in acetonitrile.
Highly strained, electron-deficient 5-aryl-meso-nitro-
β-octamethylporphyrines 1–3 were synthesized by the
nitration of 5-aryl-β-octamethylporphyrins with sodium
nitrite in trifluoroacetic acid as described in [23, 24]. It
was found that the reaction involved a fast mono-
nitration stage and proceeds further to give a dinitro-
substituted product 1; therewith, the second stage
occurred in a nonselective fashion. Two hardly separable
10,15(20)-dinitro-substituted isomers formed in roughly
equal amounts. With a large excess of sodium nitrite
1742

SYNTHESIS AND SPECTROPHOTOMETRY STUDY
1743
Scheme 1.
Me
Me
Me
Me
Me
Me
NH
N
R
N
HN
Me
Me
4, 5
Me NO2
Me
Me
O2N
Me
Me
NH
N
N
R
Me
NO2
Me
HN
Me
Me
Me
Me
NH
N
Me
Me
Me
Me
NaNO2
NaNO2
O2N
Me
+
R
CF3CO2H
CF3CO2H
N
HN
NO2
Me
Me
Me
Me
Me
NO2 Me
NH
N
N
2, 3
R
HN
Me
NO2 Me
1
R = H (1, 2, 4), NO2 (3, 5).
and much longer reaction time, trinitroporphyrins 2
and 3 were obtained (Scheme 1).
pentane-2,4-dione with hydroxyiminomalonic ester as
described in [27] (Scheme 3). We used this procedure
bearing in mind that the synthesis involving nitro-
soacetoacetic ester (Knorr procedure [28] gives fairly
much by-product 3-acetyl-2-ethoxycarbonyl-3,4-di-
methylpyrrole which can only be removed by multiple
recrystallization.
The starting 5-aryl-β-octamethylporphyrins 4 and 5
were synthesized from 2-ethoxycarbonyl-3,4,5-trimethyl-
pyrrole 6 via intermediate dipyrrolylmethanes (8 and
9) and biladiene 10 by analogy with what is described
in [25]. 5,5'-Diethoxycarbonyl-3,3',4,4'-tetramethyldipyr-
rolylmethane 8 was prepared by the radical bromine-
tion of pyrrole 6 followed by the nucleophilic sub-
stitution of bromine by the acetoxy group. The result-
ing acetoxymethylpyrrole 7 was subjected to self-
coupling by the procedure in [26] (Scheme 2).
The resulting ligands 1–3 were purified by column
chromatography on alumina (Brockmann activity
grade III) with dichloromethane as eluent.
The acid–base properties of ligands 1–3 were
studied by spectrophotometry in the systems HClO4–
acetonitrile (1) and 1,8-diazabicyclo[5.4.0]undec-7-ene–
acetonitrile (2) at 298 K. Porphyrins (H2P) exhibit
In its turn, 2-ethoxycharbonyl-3,4,5-trimethylpyrrole
6 was prepared by the reductive coupling of 3-methyl-
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 87 No. 8 2017

1744
IVANOVA et al.
Scheme 2.
Me
Me
CO2Et
Me
Me
Me
Me
Me
Me
Me
NH
NH
NH
NH
Br2
HCl
KOH
(CH2OH)2
CO2Et
CO2Et
AcOCH2
Me
NaOAc
AcOH
MeOH
N
N
H
H
Me
CO2Et
Me
Me
7
9
6
8
Me
Me
COH
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
HN+
NH
CHO
NH
N
NH
N
R
H
2Br_
R
HBr
BuOH
HBr
+
NH
HN
N
HN
NH
BuOH
Me
Me
Me
Me
Me
Me
10
9
4, 5
R = H (4), NO2 (5).
Scheme 3.
Me
Me
NaNO2
CH2(COOEt)2
CH2(COCH2)2
HON
C(CO2Et)2
AcOH
CH3I
Zn
CO2Et
Me
AcOH
N
CH3CH(COCH3)2
H
K2CO3
5
amphoteric properties in organic solvents, and in the
presence of acids and bases they can undergo protona-
tion or deprotonation involving endocyclic nitrogen atoms.
Figures 1–6 show the electronic absorption (EA)
spectra of ligands 1–3 in acetonitrile under titration
with 0.01 М acetonitrile solutions of HClO4 and 1,8-
diazabicyclo[5.4.0]undec-7-ene. As the HClO4 con-
centration in system (1) increased, two groups of
signals, each with its specific set of isosbestic points,
formed in the EA spectra. The spectrophotometric
titration curves constructed using the rexperimental
data (Figs. 1–3) provided further evidence for the step
nature of the reactions of porphyrins 1 and 2 with
HClO4, gives us grounds to suggest that the
pyrrolenine (=N–) nitrogen atoms in the porphyrin
macrorings are protonated following reactions (1) and
(2). The titration curve of compound 3 was smooth,
monotonic, and contained no step, even though the EA
spectrum showed two sets of isosbestic points (Fig. 3),
implying a step protonation process. Two-step and
kb1
H4P2+ ⇄ H3P+ + H+,
(1)
(2)
kb2
H3P+ ⇄ H2P + H+,
ka1
H2P ⇄ HP– + H+,
(3)
(4)
ka2
HP– ⇄ P2– + H+.
Here Н2Р, HР–, Р2–, H3P+, and H4P2+ are the molecular,
mono- and dideprotonated, as well as mono- and di-
protonated forms of the porphyrin ligand.
In systems (1) and (2), porphyrin ligands 1–3 are both
protonated and deprotonated [equilibria (1)–(4)].
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 87 No. 8 2017

SYNTHESIS AND SPECTROPHOTOMETRY STUDY
1745
А
(a)
(b)
А
λ, nm
λ, nm
А
А
(c)
(d)
log c(HClO)4, mol/L
log c(HClO)4, mol/L
Fig. 1. (а, b) Changes in the EA spectra and (c, d) spectrophotometric titration curves of 2,3,7,8,12,13,17,18-octamethyl-10,15-
dinitro-5-phenylporphine 1 at the (а, c) first and (b, d) second steps in system (1) at 298 K ([H2P] = 4.80×10–5 M, [HClO4] = 0–
8.23×10–4 M).
(a)
(b)
А
А
log c(HClO)4, mol/L
λ, nm
Fig. 2. (а) Changes in the EA spectrum and (b) spectrophotometric titration curve of 2,3,7,8,12,13,17,18-octamethyl-15,20-trinitro-
5-phenylporphine 2 in system (1) at 298 K ([H2P] = 1.08×10–5 M, [HClO4] = 0–1.95×10–3 M).
monotonic and smooth spectrophotometric titration
curves together with two sets of isosbestic points, too,
suggest a two-step protonation process with the very
difference that in the latter case the mono- and
deprotonation, as well as deprotonation rates are likely
to be close to each other [29]. In system (2), too,
porphyrin ligands 1–3 undergo deprotonation by both
reaction (3) and reaction (4). Figures 4–6 show the EA
spectra of compounds 1–3 in acetonitrile under
titration with a 0.01 M acetonitrile solution of 1,8-
diazabicyclo[5.4.0]undec-7-ene. In these spectra, as
the concentration of 1,8-diazabicyclo[5.4.0]undec-7-
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 87 No. 8 2017

1746
IVANOVA et al.
(a)
(b)
А
А
λ, nm
log c(HClO)4, mol/L
Fig. 3. (а) Changes in the EA spectrum and (b) spectrophotometric titration curve of 2,3,7,8,12,13,17,18-octamethyl-10,15,20-
trinitro-5-(4-nitrophenyl)porphine 3 in system (1) at 298 K ([H2P] = 6.70×10–5 M, [HClO4] = 0–7.24×10–3 M).
(a)
(b)
А
А
λ, nm
log cDBU, mol/L
Fig. 4. (а) Changes in the EA spectrum and (b) spectrophotometric titration curve of 2,3,7,8,12,13,17,18-octamethyl-10,15-dinitro-
5-phenylporphine 1 in system (2) at 298 K ([H2P] = 8.68×10–5 M, [DBU] = 0–2.21×10–3 M).
ene was increased, we also observed the formation of
two groups of signals, each containing its specific set
of isosbestic points.
The table lists the parameters of the EA spectra for
equilibria (1)–(4) in systems (1) and (2), as well as the
corresponding protonation and deprotonation constants.
The basicity and acidity constants for processes (1)–(4)
were calculated by Eq. (5).
In the case of compound 1, the spectrophotometric
titration curve constructed with the experimental data
(Fig. 4) had a step, thereby providing evidence
showing that the reaction of the porphyrins with 1,8-
diazabicyclo[5.4.0]undec-7-ene occurred in two steps
[reactions (3) and (4)]. The titration curves for com-
pounds 2 and 3 in system (2), like that for the
protonation of compound 3 in system (1), contained no
steps, which, too, suggested close step deprotonation
constants.
log K = log (Ind) + nlog сan.
(5)
Here K is the equilibrium constants for the first and
second steps; Ind, indicator [H2P]/[H3P+] ratio for the
first step and [H3P+]/[H4P2+] ratio for the second step
(or [НP–]/[H2P] and [P2–]/[HP–]); сan, analytical
concentration of the titrant in the solution; n, number
of protons involved in the process (pK = –log K). The
The constants were measured accurate to within 3–5%.
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SYNTHESIS AND SPECTROPHOTOMETRY STUDY
1747
А
А
(a)
(b)
λ, nm
log cDBU, mol/L
Fig. 5. (а) Changes in the EA spectrum and (b) spectrophotometric titration curve of 2,3,7,8,12,13,17,18-octamethyl-10,15,20-
trinitro-5-phenylporphine 2 in system (2) at 298 K ([H2P] = 1.13×10–5 M, [DBU] = 0–2.01×10–4 M).
А
(a)
(b)
А
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
–4.8 –4.6 –4.4 –4.2 –4.0 –3.8
λ, nm
Fig. 6. (а) Changes in the EA spectrum and (b) spectrophotometric titration curve of 2,3,7,8,12,13,17,18-octamethyl-10,15,20-
trinitro-5-(4-nitrophenyl)porphine 3 in system (2) at 298 K ([H2P] = 1.42×10–5 M, [DBU] = 0–1.58×10–4 M).
log cDBU, mol/L
As known, the electronic effects of substituents in
the macroring are among factors that allow spectral
observation of monocationic forms. As a rule, the step
protonation and deprotonation equilibria are easily
observed for porphyrins, in which the nitrogen atoms
have much different electron densities. Apparently,
strong polarization of the molecule will, too, favor
differentiation of the cationic and anionic forms of
porphyrins as acids and bases. It should be noted that
the presence of isosbestic points and the character of
spectral changes suggest that the changes in the
concentrations of the two absorbing centers of the
porphyrin molecule do not change the relative
fractions of the ionized forms on deprotonation and
protonation. The apparent absorbances of all the
porphyrin forms involved in equilibria (1)–(4) in
systems (1) and (2) were calculated using the EA
spectral data and the total concentrations of each
porphyrin species (see table). Having determined the
number of protons that take part in the equilibrium, we
could determine the character of ionization of por-
phyrin and calculate the step deprotonation and proto-
nation constants. Analysis of the data in the table, in
particular, the protonation and deprotonation constants
of substituted porphyrins 1–3, showed that our present
results are in a good agreement both with the classical
view on the effects of substituents, not only those
introduced directly in the macroring, but also those in
the phenyl “buffer,” and with published data in this
field. According to [21], the so-called buffer effect of
the meso-phenyl substituents in the porphyrin macro-
ring favors delocalization of the excess charge (both
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 87 No. 8 2017

1748
IVANOVA et al.
Parameters of the EA spectra of the molecular, mono- and diprotonated, and mono- and dideprotonated forms of compounds
1–3 and corresponding acid and base dissociation constants in acetonitrile at 298 K
pKb2 (рKb1)
рKa1 (pKa2)
[pKa1,2]
Porphyrin (form) λ1, nm (log ε)
λ2, nm (log ε)
λ3, nm (log ε)
λ4, nm (log ε)
[рKb1,2
]
1 (H2P)
1 (HP–)
1 (P2–)
389 (4.09)
411 (4.42)
421 (4.46)
415 (4.38)
448 (4.55)
421 (5.02)
377 (4.87)
464 (5.12)
473 (5.08)
428 (4.95)
357 (4.77)
474 (5.05)
514 (3.47)
512 sh (3.57)
512 sh (3.57)
514 (4.34)
–
588 (3.34)
552 (3.59)
558 (3.67)
588 (3.60)
589 (3.56)
–
646 (3.26)
586 sh (3.53)
589 sh (3.57)
646 (3.59)
644 (3.41)
602 (3.90)
700 sh (4.37)
661 (4.28)
665 (4.29)
613 (4.16)
664 sh (4.39)
667 (4.01)
6.62
4.37
(3.64)
(5.47)
[9.84]
[10.26]
1 (H3P+)
1 (H4P2+)
2 (H2P)
2 (P2–)
529 (4.17)
–
6.06
(4.78)
[10.84]
–
–
511 (4.86)
606 (4.30)
612 (4.35)
–
2 (H3P+)
2 (H4P2+)
3 (H2P)
3 (P2–)
[8.32]
530 (4.31)
510 (4.90)
610 (4.08)
–
–
–
–
–
3 (H4P2+)
–
[11.23]
[8.06]
positive and negative) and can enhance both acidic and
basic properties of tetraphenylporphine derivatives
compared to the unsubstituted porphine. Quite an
important parameter of spectrophotometric titration is
the difference between the protonation and deprotona-
tion constants, which reflects not only changes in the
symmetry and geometry of the molecule, but also
charge redistribution that affects the electron density
on the endocyclic nitrogen atoms. In the present work,
the difference between the protonation and deprotona-
tion constants for processes (1) and (2) in system (1)
decreases from about 3 orders of magnitude (com-
pound 1) to 1.28 (compound 2) and, finally, to near
zero (compound 3). For processes (3) and (4) in system
(2) this difference was slightly higher than an order of
magnitude for compound 1, which implied syn-
chronous ionization processes. The respective dif-
ference for compounds 2 and 3 was near zero. The
quantum-chemical calculations in [30] showed that
meso-phenyl substituents, which are weak electron
acceptors, withdraw the electron density from the
macroring. Phenyl substitution in porphine decreases
the effective electron charge on the meso-carbon atoms
by ≈0.03 ē, whereas the effective charge on the
nitrogen atoms of the reaction center remains almost
unchanged. However, the macroring is therewith
deformed due to certain isolation of the π-electron
systems of the pyrrole and pyrrolenine fragments.
Analyzing the aforesaid we can conclude that the
changes in the acid–base properties of the nitro deri-
vatives of 5-phenyl-β-octaalkylporphine are associated
both with the acceptor effect of the NO2 groups, but
also with the deformation of the planar macroring
geometry. Thus, chemical modification of the macro-
ring can be used to vary the acid–base properties of the
macroheterocyclic ligands, and variation of the com-
position of the medium, along with the structural and
electronic effects of substituents, can serve as an efficient
tool for controlling the reactivity of porphyrins.
EXPERIMENTAL
The EA spectra were obtained on SPEK SSP-715,
Cary 100, Shimadzu UV-1800 , and Hitachi UV-2000
scanning spectrophotometers. The IR spectra were
measured on Thermo Nicolet AVATAR 360 FTIR
spectrometer in KBr pellets. The MALDI–TOF mass
spectra were run on a Shimadzu Axima Confidence
1
instrument. The Н NMR spectra were obtained on a
Bruker 500 spectrometer in CDCl3. Thin-layer chro-
matography was performed on Silufol plates. Com-
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SYNTHESIS AND SPECTROPHOTOMETRY STUDY
1749
pounds 1–3 were purified and identified as described
in [31]. The solvent was high-purity acetonitrile (water
content >0.03%), where the starting porphyrins were
present in the molecular form, as evidenced by their
spectra. Spectrophotometric titration with acetonitrile
solutions of perchloric acid and 1,8-diazabicyclo[5.4.0]-
undec-7-ene was performed on a Cary 100 Varian
spectrophotometer.
(0.11 mol), was gradually added to a suspension of
20.0 g (0.11 mol) 2-(ethoxycarbonyl)-3,4,5-trimethyl-
pyrrole and 19.0 g (0.23 mol) of anhydrous sodium
acetate in 150 mL of acetic acid under stirring and
cooling with cold water, and the mixture was stirred
for 0.5 h and poured into 1 L of water. The precipitate
was filtered off and washed with water. The resulting
acetoxymethylpyrrole 7 was dissolved in a mixture of
200 mL of methanol and 5 mL of HCl and refluxed
under constant stirring for 3 h. The mixture was then
cooled down, the precipitate was filtered off, washed
with methanol, and dried in air at 70°С. Yield 10.0 g
The experimental and data processing procedure
are described in detail in [8, 18].
Nitrosomalonic ester. A solution of 216.0 mL
(0.75 mol) of malonic ester in 45 mL of acetic acid and
a solution of 105 g (1.52 mol) of sodium nitrite in
200 mL of water were added in succession for over 2 h
at <15°С to a solution of 14.5 g (0.49 mol) of sodium
hydroxide in 150 mL of acetic acid. The mixture was
allowed to stand for 3 days at room temperature and
then extracted with 2 equal portions of diethyl ether.
The extract was washed with water to neutral
washings, dried with sodium sulfate, and evaporated to
obtain ~0.71 mol of nitrosomalonic ester which was
then used without further purification.
1
(52.5%), mp 128–129°C (methanol). H NMR spec-
trum, δ, ppm: 9.03 br.s (2H, NH), 4.25 q (4H, OCH2Et,
J = 7.1 Hz), 3.84 s (2H, ms-CH2), 2.24 s (6H, 3,3'-
СН3), 2.31 s (6H, 4,4'-CH3), 1.30 t (6H, CH3Et, J = 7.1 Hz).
2,2'-(3,3',4,4'-Tetramethyl)dipyrrolylmethane
(9). A solution of 1.0 g (2.89 mmol) of dipyrrolyl-
methane 8 and 1.0 g (17.8 mmol) of KOH in 15 mL of
ethylene glycol was refluxed for 1 h, cooled down, and
poured into 150 mL of water containing 5 g of sodium-
acetate trihydrate. The precipitate was filtered off,
washed with water, and dried in air at room tem-
perature. Yield 0.5 g (85.5%).
3-Methylpentane-2,4-dione. A mixture of 315 mL
(3.1 mol) of acetylacetone and 200 mL (3.21 mol) of
methyl iodide was gradually added to a stirred mixture
of 360 g (2.6 mol) of potash and 500 mL of acetone.
The mixture was refluxed for 8 h. After cooling, the
precipitate was filtered off and washed with acetone.
The solvent was removed by distillation, and the
residue was distilled to collect the fraction with bp 160–
175°C. Yield 287 g (78%).
2,3,7,8,12,13,17,18-Octamethyl-5-phenylpor-
phine (4). Concentrated hydrobromic acid, 2 mL, was
added at room temperature to a stirred solution of 0.5 g
(2.47 mmol) of dipyrrolylmethane 9 and 0.61 g
(4.95 mmol) of 2-formyl-3,4-dimethylpyrrole in
100 mL of butanol (biladiene 10 precipitated). The
mixture was stirred for 1 h and, after addition of
2.0 mL (19.8 mmol) of benzaldehyde, for an additional
4 h under reflux. Benzoquinone, 0.6 g (5.55 mmol),
was then added, and the resulting mixture was refluxed
for 15 min. The precipitate (240 mg) that formed after
removal of butanol was filtered off, washed with
water, dried in air at 70°C, and dissolved in a me-
thylene chloride containing trifluoroacetic acid (1 mL
of trifluoroacetic acid in 50 mL of methylene chlo-
ride). The solution was filtered, and the filtrate was
neutralized with diethylamine (~2 mL) until its color
changed from green to red. The precipitate that formed
was filtered off, washed with methylene chloride, and
dried in air at room temperature. Yield 240 mg. The
filtrate was subjected to chromatography on alumina
(Brockmann activity grade II) in methylene chloride.
The eluate was evaporated, and the porphyrin was
precipitated with methanol, filtered off, washed with
methanol, and dried in air at room temperature. Total
yield 430 mg (34.9%), Rf 0.39 (benzene). IR spectrum,
2-Ethoxycarbonyl-3,4,5-trimethylpyrrole (6). A
solution of nitrosomalonic ester (~0.71 mol) in 150 mL
of acetic acid and 60 mL of water and 186 g (2.82 mol)
of zinc dust were simultaneously added to a stirred
solution of 81.0 g (0.71 mol) of 3-methylpentane-2,4-
dione in 260 mL of acetic acid (temperature <95°С).
The resulting mixture was stirred for an additional 1 h
on a boiling water bath and then poured into 5 L of
water. The precipitate was filtered off, washed with
water, dissolved in benzene, excel zinc dust was filtered
off, benzene was distilled off, and the residue was
recrystallized from methanol. Yield 55.7 g (43.3%),
1
mp 127–128°С. H NMR spectrum, δ, ppm: 8.86 br.s
(1H, NH), 4.31 q (2H, CH2Et, JНН = 7.2 Hz), 2.28 s
(3H, CH3), 2.21 s (3H, CH3), 1.94 s (3H, CH3), 1.37 t
(2H, CH3Et, JНН = 7.2 Hz).
2,2'-[5,5'-Bis(ethoxycarbonyl)-3,3',4,4'-tetra-
methyl]dipyrrolylmethane (8). Bromine, 5.7 mL
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 87 No. 8 2017

1750
IVANOVA et al.
ν, cm–1: 2958, 2920, 2857, 1631, 1443, 1387, 1229,
1116, 1058, 1017, 944, 831, 741, 692. EA spectrum,
2,3,7,8,12,13,17,18-Octamethyl-10,15,20-trinitro-
5-phenylporphine (2) was prepared in a similar way.
Yield 80 mg (63.1%), Rf 0.63 (benzene). IR spectrum,
ν, cm–1: 3322, 2932, 2853, 1644, 1536 [δas(NO2)],
1446, 1360 [δs(NO2)], 1156, 1137, 873, 808, 707, 662.
EA spectrum, λmax, nm (log ε): 669 (3.46), 607 (3.76),
λ
max, nm (log ε): 624 (3.55), 571 (3.86), 537 (3.90),
1
503 (4.19), 404 (5.27). H NMR spectrum, δ, ppm:
10.49 s (2H, 10,20-H), 10.35 s (1H, 15-H), 8.30 d (2H,
2,6-HPh, J = 6.8 Hz), 7.97–8.06 m (3H, 3,4,5-НPh), 3.60
s (12H, 12,13,17,18-CH3), 3.33 s (6H, 2,8-CH3), 2.28 s
(6H, 3,7-CH3), –2.83 br.s and –4.04 br.s (4H, NH).
Mass spectrum (MALDI-TOF), m/z: 499.152 [M + H]+.
1
530 (4.05), 429 (4.94). Н NMR spectrum, δ, ppm:
8.08–8.12 m (2H, 2,6-HPh), 7.79–7.88 m (3H, 3,4,5-
HAr), 3.01 br.s (12H, 12,13,17,18-CH3), 2.86 br.s (6H,
2,8-CH3), 2.03 br.s (6H, 3,7-CH3), –2.77 br.s (1H,
NH), –2.97 br.s (1H, NH). Mass spectrum (MALDI-
TOF), m/z: 634.262 [M + H]+.
2,3,7,8,12,13,17,18-Octamethyl-5-(4-nitrophenyl)-
porphine (5) was prepared in a similar way from
0.52 g (2.57 mmol) of 3,3',4,4'-tetramethyldipyrrolyl-
methane 9, 0.63 g (5.14 mmol) of 2-formyl-3,4-
dimethylpyrrole, and 2.0 g (13.23 mmol) of 4-nitro-
benzaldehyde. Yield 470 mg (33.6%), Rf 0.30
(benzene). IR spectrum, ν, cm–1: 2977, 2921, 2857,
1644, 1590, 1519 [δas(NO2)], 1444, 1342 [δs(NO2)],
1289, 1162, 1141, 1048, 953, 853, 754, 696. EA
spectrum, λmax, nm (log ε): 625 (3.55), 572 (3.82), 538
2,3,7,8,12,13,17,18-Octamethyl-10,15,20-trinitro-
5-(4-nitrophenyl)porphine (3) was prepared in a
similar way. Yield 40 mg (32.7%), Rf 0.55 (benzene).
IR spectrum, ν, cm–1: 3328, 2929, 1644, 1596, 1540
[δas(NO2)], 1448, 1345 [δs(NO2)], 1137, 1093, 1010,
1
873, 840, 735, 688, 599. Н NMR spectrum, δ, ppm:
8.70 d (2H, 2,6-HAr, J = 8.5 Hz), 8.34 d (2H, 2,6-HAr,
J = 8.5 Hz), 3.02 br.s (12H, 12,13,17,18-CH3), 2.87
br.s (6H, 2,8-CH3), 2.03 br.s (6H, 3,7-CH3), –2.78 br.s
(1H, NH), –3.00 br.s (1H, NH). Mass spectrum
(MALDI-TOF), m/z: 679.295 [M + H]+.
1
(3.88), 504 (4.15), 403 (5.16). H NMR spectrum, δ,
ppm: 10.54 s (2H, 10,20-H), 10.42 s (1H, 15-H), 8.87
d (2H, 2,6-HAr, J = 8.5 Hz), 8.58 d (2H, 3,5-HAr, J =
8.5 Hz), 3.61 s (12H, 12,13,17,18-CH3), 3.35 s (6H,
2,8-CH3), 2.30 s (6H, 3,7-CH3), –2.72 br.s (2H, NH),
–3.90 br.s (2H, NH). Mass spectrum (MALDI-TOF),
m/z: 544.197 [M + H]+.
ACKNOWLEDGMENTS
The work was financially supported by the Russian
Science Fund (project no. 23-00204-P) using
equipment of the Center for Collective Use, Ivanovo
State University of Chemical Technology.
2,3,7,8,12,13,17,18-Octamethyl-10,20-dinitro-5-
phenylporphine (1). A solution of раствор 50.0 mg
(0.72 mmol) of solium nitrite in 0.5 mL of water was
added to a stirred solution of 100 mg (0.20 mmol)
2,3,7,8,12,13,17,18-octamethyl-5-phenylporphine in
5.0 mL of trifluoroacetic acid. The mixture was stirred
for 2 h at room temperature and then poured into
50 mL of water and neutralized with ammonium
solution until a change of color. The precipitate was
filtered off, washed with water, dried in air, dissolved
in benzene, ad chromatographed on silica in benzene.
The eluate was evaporated, and the product was
precipitated with methanol. The precipitate was
filtered off, washed with methanol, and dried in air at
room temperature. Yield 90 mg (76.4%), Rf 0.70
(benzene). IR spectrum, ν, cm–1: 2964, 2927, 2869,
1636, 1533 [δas(NO2)], 1447, 1361 [δаs(NO2)], 1162,
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