Effect of macrocycle deformation and electronic effects of substituents on the stability of zinc-5,15-di(o-nitrophenyl)octaalkylporphyrin molecular complexes

Article abstract of DOI:10.1134/S1070363209050259

The process of intermolecular interaction of zinc-5,15-di(o-nitrophenyl)- octaalkylporphyrin with nitrogen-containing bases of various sturctures was studied using the method of absorption spectroscopy. A dependence of stability of axial zinc-porphyrin complex on electronic effects of nitro groups and basic properties of extra ligand is revealed. By quantum-chemical PM3 method geometric structure and energetic characteristics of optimized molecules of zinc-porphyrin and its axial complexes was calculated. The influence of conformational effects of the porphyrin ligands on the strength of σ-bond of zinc with nitrogen atom of the nitrogen base (Zn-N_L) was revealed. It was established that the formation of the Zn-N_L bond proceeded with the change in the type and degree of deformation of the macrocycle in the molecular complex. Correlations between the calculated values of energy of Zn-N_L bond and stability of the axial complexes were found.

Full text of DOI:10.1134/S1070363209050259

ISSN 1070-3632, Russian Journal of General Chemistry, 2009, Vol. 79, No. 5, pp. 1010–1017. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © S.V. Zaitseva, S.A. Zdanovich, O.I. Koifman, 2009, published in Zhurnal Obshchei Khimii, 2009, Vol. 79, No. 5, pp. 838–845.
Effect of Macrocycle Deformation and Electronic Effects
of Substituents on the Stability
of Zinc-5,15-di(o-nitrophenyl)octaalkylporphyrin
Molecular Complexes
S. V. Zaitsevaa, S. A. Zdanovicha, and O. I. Koifmana,b
a Institute of Chemistry of Solutions, Russian Academy of Sciences,
ul. Akademicheskaya 1, Ivanovo, 153045 Russia
e-mail: svz@isc-ras.ru
b Ivanovo State Chemical Technological University, Ivanovo, Russia
Received October 20, 2008
Abstract―The process of intermolecular interaction of zinc-5,15-di(о-nitrophenyl)-octaalkylporphyrin with
nitrogen-containing bases of various sturctures was studied using the method of absorption spectroscopy. A
dependence of stability of axial zinc-porphyrin complex on electronic effects of nitro groups and basic
properties of extra ligand is revealed. By quantum-chemical РМ3 method geometric structure and energetic
characteristics of optimized molecules of zinc-porphyrin and its axial complexes was calculated. The influence
of conformational effects of the porphyrin ligands on the strength of σ-bond of zinc with nitrogen atom of the
nitrogen base (Zn–NL) was revealed. It was established that the formation of the Zn–NL bond proceeded with
the change in the type and degree of deformation of the macrocycle in the molecular complex. Correlations
between the calculated values of energy of Zn–NL bond and stability of the axial complexes were found.
DOI: 10.1134/S1070363209050259
Among the methods of controlling the properties of
porphyrins an important one is their modification by
introduction of substituents of certain type (electron-
releasing and withdrawing, hydrophilic, lipophilic,
etc.) to the structure of the macrocycle. Besides the
electronic factors, increased attention is paid now to
the effect of deformational factor on the properties of
metalloporphyrins, spectral and coordination
characteristics first of all.
carried out using the spectrophotometric titration [1]
and computer simulation [2–4] allowing prediction of
the process course and character, the estimation of the
structure, and state of reagents and reaction products.
Bu
NO2
Bu
m2
NO2
N1
m1
N2
N3
Zn
m3
N4
This work continues our systematic investigations
of coordination properties of sterically hindered
metalloporphyrins in reactions with organic bases (L).
We studied effect of nitro groups and conformational
effects of porphyrin macrocycle on the properties of
zinc-5,15-di(о-nitrophenyl)-2,8,12,18-tetrabutyl-3,7,13,17-
tetramethylporphyrin [ZnP(I)] in the reaction of axial
binding with imidazole (Im), 2-methylimidazole (2-
MeIm), 2-methylbenzimidazole (2-MeBzI), pyridine
(Py), quinoline (Hi), 3, 5-dimethylpyrazole (DMP),
dimethylformamide (DMF), pyridazine (Prd),
pyrimidine (Prm), and pyrazine (Prz). The study was
m4
Bu
Bu
ZnP(I)
The axial binding of zinc-porphyrin with an organic
base in benzene at 298K leads to the formation of a
complex with composition (L)nZnP(I). The reaction
proceeds almost instantly and leads to the shift of
absorption bands (В, Q1 and Q2) in electron absorption
spectrum of the metalloporphyrin (EAS) and to the
change in their intensity (Fig. 1). Such variations in the
1010

EFFECT OF MACROCYCLE DEFORMATION
1011
A
(b)
(a)
425
416
0.7
A
0.6
0.5
0
0.5
1.0
1.5
CIm×10–4, mol l–1
557
545
580
592
X5
380
430
480
530
580
630
λ, nm
Fig. 1. (а) Changes in electron absorption spectra of ZnP(I) at the reaction with imidazole: (1) ZnP without imidazole (cZnP
=
3.9×10–6 mol l–1 ); (2–11) ZnP with imidazole at varied concentration (cZnP = 3.9×10-6 mol l–1; cIm =5.7×0–6–1.4×10–4 mol l–1);
(12) ZnP with imidazole excess (2.8×10-3 mol l–1) in benzene; ( b) The corresponding titration curve at Δλ = 413 nm.
spectrum of the complex allow the application of
spectral methods to the evaluation of the qualitative
and quantitative characteristics of the process of
intermolecular interaction.
The comparison of the obtained quantitative
characteristics of the reaction of zinc-porphyrin axial
binding with organic bases (Table 1) allows to reveal
the following sequence of stability of molecular
complexes: (Im)ZnP(I) > (2-MeIm)ZnP(I) > (Py)ZnP(I)
> (DMP)ZnP(I) > (DMF)ZnP(I). The trend obtained is
caused by the decrease in basic properties of axial
ligand in going from imidazole to dimethylformamide.
The basicity is indicated by the values of рKвн+ [5].
The decrease in stability (Kstab) of axial complexes (Hi)
ZnP(I) and (2-MeBzIm)ZnP(I) as compared with (Py)
ZnP(I), (DMP)ZnP(I) and the similarity of the values
of constants for (2-MeIm)ZnP(I) and (Py)ZnP(I)
(Table 1) results from the fact that the formation of
Zn–L bond leads to the appearance of steric hindrances
due to the bulky structure of 2-methylimidazole,
quinoline and 2-methylbenzimidazole.
The composition of the formed zinc complex was
estimated from the linear plot log [(Ap – A0)/(A∞ – Ap)]
on log cL [1] (Fig. 2). The slope (tan α) of these strait
lines for compounds (L)nZnP(I), where L = Im, 2-
MeIm, 2-MeBzIm, Py, DMP, Hi, Prd, Prm and DMF
falls in the range 0.9–1.1, that is, equals unity within
the experimental error (n = 1). For the complex with
pyrazine, tgα equals 1.45 (n = 1.5). Thus, the structure
of the molecular complexes corresponds to the types
(L)ZnP and (L)3(ZnP)2. The structure (Prz)3[ZnP(I)]2
becomes possible owing to the relatively low basicity
of the porphyrin ligand (due to the electronic effect of
nitro groups and a weak deformation of the
macrocycle) and to the presence of two reaction
centers in the nitrogen-containing base with an
appropriate orientation for the axial binding.
In the case of reactions with dibasic compounds the
stability of (Prm)ZnP(I) complex is higher than that of
(Prd)ZnP(I) (Table 1). We believe that in going from
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 79 No. 5 2009

1012
ZAITSEVA et al.
The orientation of the second nitrogen atom in
log [(Ap – A0)/(A∞ – Ap)]
(Prd)ZnP(I) complex also contributes to the decrease
in the complex stability. The closeness of the second
nitrogen atom (in the оrtho position) to the reaction
center leads to the effect of its repulsion and hence of
repulsion of the whole molecule of the base by the
nearest intracyclic nitrogen atoms of metalloporphyrin.
2
4.50
9
3.50
4
2.50
7
6
5
1.50
The absence of molecular complex with pyrazine in
the stability series is due to another type of structure of
(Prz)3(ZnP(I))2. It is important to note that to the
existence of this structure contributes energetically
also the profitable proton affinity of pyrazine at the
double protonaton (at the second nitrogen atom). The
corresponding value of Eprot is higher than in
pyridazine and pyrimidine by 22.63 and 3 kcal mol–1,
respectively.
3
8
1
0.50
–2
2
4
–log cL
–0.50
–1.50
–2.50
10
Fig. 2. Plot log [(Ap – A0)/(A∞ – Ap)] vs. log cL for the
intermolecular interaction between ZnP and (1) Im,
(2) 2-MeIm, (3) 2-MeBzI, (4) Py, (5) Hi, (6) DMP,
(7) DMF, (8) Prd, (9) Prm, and (10) Prz. А0, Ар, А∞ are
optical density of solutions at the operating wavelength of
metalloporphyrin, equilibrium mixture at certain ligand
concentration, and of ligand, respectively.
The proton affinity of basic nitrogen-containing
compounds suffers practically no change at the transfer
from water to gas phase. Bulky molecules form an
exclusion: their proton affinity is slightly higherin gas
than in water (Table 1). With accounting for the
calculated characteristics of the nitrogen-containing
bases the above sequence of stability is transformed
into the following sequence: (Im)ZnP(I) > (Py)ZnP(I)
> (DMP)ZnP(I) > (Prm)ZnP(I) > (Prd)ZnP(I) > (DMF)
ZnP(I).
the water phase into the organic solvent many
nitrogen-containing bases can change the basicity
index. As known, the regularities in the change of
рKвн+ in inert organic solvents are similar to those in
the gas phase [6]. Therefore we calculated using РМ3
method [7] the proton affinity (Eprot) in gas phase for
all the studied bases (Table 1). Finally we found that
Eprot of pyridazine is slightly below that of pyrimidine
and pyrazine.
Using the data of Table 1 we found the following
correlations between log Kstab. and рKвн+, and between
log Kstab and Еprot:log Kstab = 2.4376е(0.1023рKвн+
(correlation coefficient r = 0.98) and log Kstab
0.1054e(0.0227Еprot) (r = 0.99) (Figs. 3 and 4). Also,
)
=
Table 1. Thermodynamic characteristics of molecurar complexes ZnP(I)
Complex
Kstab(298 K)×10–3, mol–1
l
рKBH+ [5]
–Eprot of base, kcal mol–1
–Eb M–NL, kcal mol–1 Δλmax (Q1, Q2), nm
(Im)ZnP
109.00±11.70
1.57±0.25
18.60±8.14
13.60±1.16
3.66±0.55
5.89±0.80
0.50±0.08
1.31±0.22
4.15±0.36
2.41±0.45
6.65
6.19
5.89
5.29
4.94
4.27
0.92
2.33
1.3
169.36
175.21
173.06
162.79
168.72
157.60
142.92
148.49
155.54
151.77
23.56
12.09
18.61
18.25
12.42
15.97
4.18
12
10
11
10
9
(2-MeBzIm)ZnP
(2-MeIm)ZnP
(Py)ZnP
(Hi)ZnP
(DMP)ZnP
(DMF)ZnP
(Prd)ZnP
9
6
11.91
15.03
3.76
8
(Prm)ZnP
9
(Prz)3(ZnP)2
1 macrocycle
2 macrocycle
0.6
8
0.17
3.43
0.68
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 79 No. 5 2009

EFFECT OF MACROCYCLE DEFORMATION
1013
Im
5.5
5
4
3
Im
Py
4.5
DMP
4.5
2-Me-Im
DMP
Py
Prm
3.5
Prd
DMF
DMF
0.5
2.5
6.5
pKBH
+
2.5
140
150
160
170
–Eprot, kcal mol–1
Fig. 4. Plot of stability of (L)ZnP(I) complex vs. the Eprot of
organic bases calculated by РМ3 quantum-chemical
method.
Fig. 3. Plot of the complex (L)ZnP(I) stability vs Kвн+ of
organic base.
there is a dependence between the stability of the
molecular complex and the value of shift (Δλmax) of the
maxima of the main absorption bands (Q1 and Q2) in
the respective electronic spectrum (Fig. 5). This
dependence is also of symbatic character, and is
described by the equation log Kstab = 1.5032е(0.0994Δλ)
(r = 0.98). This dependence can be used for qualitative
estimation of stability of the complexes.
Analysis of the results of calculation shows that the
molecule of ZnP(I) is not planar: it has deformation of
a saddle type (Table 2, Figs. 6, 7). Phenyl substituents
are tilted toward the XY plane containing N4
coordination center at the angle 86°–88°. The butyl
substituents in the macrocycle are oriented alter-
natively up and down relatively to the average plane of
the molecule (Fig. 6). The N4 plane has a rhombic
shape that is consistent with the data of X-ray struc-
tural analysis [11]. Its perimeter equals to 11.6536 Å.
Average deviation of the macrocyle skeleton atoms
from its average plane along Z axis (|ΔZav|) equals to
0.0934 Å. For ZnP(II) and ZnP(III) the values of |ΔZav|
are 0.1585 Å and 0.2837 Å respectively. The
deformation screwing grows in the series: ZnP(I) < ZnP
(II) < ZnP(III). By the comparison of stability of these
zinc-porphyrin molecular complexes the following
sequence is obtained: ZnP(III)< ZnP(II) < ZnP(I) [8–
10] (Tables 1 and 2). The absence of ZnP(IV) in these
series is due to the electronic activity of OCH3 groups
and to the steric factor originating from the inclination
of these groups toward N4 plane narrowing the cavity
of coor-dination interaction.
Note that unlike the earlier studied meso-diphenyl-
substituted zinc-porphyrins {Zn-5,15-di(p-butyl-
oxyphenyl)-2,8,12,18-tetramethyl-3,7,13,17-tetra-
butylporphyrin [ZnP(II)], “overlapped” Zn-5,15-[2,5-
bis(2'-phenyleneoxymethylene)-1,4-dimethoxy-
benzene]-2,8,12,18-tetramethyl-3,7,13,17-tetrabutyl-
porphyrin {ZnP(III))} [8–10] the shape of the plots
obtained for the molecular complexes ZnP(I) is close
to linear. In our opinion this is connected with a low
steric strain in the ZnP(I) macrocycle.
Comparing the values of Kstab. for compounds (L)
ZnP(II), (L)ZnP(III) and (L)Zn-5,15-di(о-methoxy-
phenyl)-2,8,12,18-tetramethyl-3,7,13,17-tetrabutyl-
porphyrin ((L)ZnP(IV)) studied in [8–10] and of the
molecular complexes ZnP(I) (Table 1) we can note a
significant higher stability of the latter. This is caused
by the presence of electron-acceptor substituents in о-
positions and a low degree of deformation of ZnP(I)
macrocycle leading to higher positive charge on the
zinc atom. Eventually this results in a higher ability of
the metalloporphyrin to coordinating a base with the
formation of stronger metal–axial ligand σ-bond (Zn–NL).
Im
5
Py
DMP
4
3
2-Me-Im
11.5
DMF
Proceeding from the calculated characteristics
obtained by quantum-chemical РМ3 method we noted
the effect of steric screwing of the ZnP(I) macrocycle
on its structure and its properties in the reaction of
axial binding with organic bases.
5.5
7.5
9.5
Δλ, nm
Fig. 5. Plot of log Kstab of complex (L)ZnP(I) vs. the values
of shift of basic absorption band in electronic spectra.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 79 No. 5 2009

1014
ZAITSEVA et al.
Table 2. Selected geometric characteristics of ZnP(I) and its molecular complexes
Bond length, Å
Complex
Zn–N1
Zn–N3
2.0346
2.0340
2.1203
2.0913
2.1266
2.1080
2.0910
2.1157
2.1168
2.0935
2.0979
2.1079
2.1038
2.0989
2.1327
2.1059
2.1089
2.0913
2.1162
2.0874
2.0917
2.1161
2.0945
2.1127
Zn–N2
Zn–N4
2.0630
2.0868
2.1013
2.1335
2.1050
2.1302
2.1271
2.1109
2.1082
2.1316
2.1386
2.1533
2.1124
2.1234
2.0990
2.1409
2.0865
2.1172
2.1020
2.1320
2.0794
2.1001
2.0984
2.0782
N1–N3
N2–N4
4.0679
4.1714
4.1362
4.1443
4.1387
4.1142
4.1252
4.1539
4.1347
4.1557
4.1051
4.1851
4.1254
4.1519
4.1389
4.1300
4.1399
4.1348
4.1337
4.1446
4.1992
4.1645
4.2000
4.1624
Сm1–Cm3
Сm2–Cm4
7.1245
6.8150
7.1199
6.7831
7.1214
6.7368
7.1225
6.7798
7.1208
6.7991
7.1557
6.7771
7.1119
6.7965
7.1213
6.7902
7.1190
6.7874
7.1224
6.7919
7.1267
6.7988
7.1392
6.7799
b
Zn–NL
Zn–Ct
0.0355
Ра
lN–N
ZnP(I)
11.6536
10.2797
10.2847
10.7581
10.1917
10.5115
10.3859
10.9310
10.7277
10.2102
10.5648
10.3691
10.3003
(Im)ZnP
2.0829
2.1516
2.1071
2.1075
2.1471
2.1203
2.2179
2.1590
2.1290
0.3982
0.4480
0.4121
0.3972
0.4573
0.4011
0.4795
0.3903
0.3817
0.1774
0.1721
11.7043
11.6394
11.7012
11.7048
11.7169
11.6993
11.6872
11.6956
11.7021
11.8226
11.8199
(2-MeBzIm)ZnP
(MeIm)ZnP
(Py)ZnP
(Hi)ZnP
(DMP)ZnP
(DMF)ZnP
(Prd)ZnP
(Prm)ZnP
(Prz)3(ZnP)2
1 macrocycle
2.2246
2.5093
2.5024
2.2300
2 macrocycle
а Perimeter of N4 coordination plane; b distance between nitrogen atoms of NO2 groups.
Proceeding from the calculated characteristics we
conclude that the type of the molecular complex
formed at the axial binding of metalloporphyrin and
organic base is respectively (L)ZnP(I) and (Prz)3·
[ZnP(I)]2, in good agreement with the experimental
data.
of base with the metalloporphyrin leads also to
extension of coordination plane N4 by weakening of
the bond between zinc atom and intracyclic nitrogen
atoms of the macrocycle. Also a change occurs in the
distance between nitrogen atoms of NO2 groups (Table 2)
and in the values of the angle of inclination of phenyl
fragments to XY plane by 2°–20°.
Appearance of Zn–NL bond leads to a change in the
structural mode of the coordination node from planar
to tetragonal bipyramid with rhombic N4 base. Notable
steric screwing of the zinc-porphyrin macrocycle
(Figs. 6 and 7, Table 2) is observed. The deformation
mode is changed from saddle to a mixed: dome
(dominates) with a small fractions of saddle and riffle
(Fig. 7). It should be noted that while deformations of
different (L)ZnP(I) complexes are of the same type the
bond angles in their methylene bridges and angles of
inclination of pyrrole fragments toward average
macrocycle plane are different (Fig. 7). Axial binding
For the complex (Prz)3[ZnP(I)]2 a presence is
characteristic of two nonplanar macrocycles with
dominating dome type deformation (Figs. 6 and 7).
The angle of inclination of phenyl fragments to XY
plane is 84°–85° in both the zinc-porphyrin molecules.
Analysis of the experimental and calculated data
allows to note that the value of Kstab correlates with the
Zn–NL bond length. Increase in the strength of Zn–NL
σ-bond in the coordination center favors increase in the
stability of the molecular complexes (Tables 1 and 2).
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 79 No. 5 2009

EFFECT OF MACROCYCLE DEFORMATION
1015
However, there is no dependence between deviation of
zinc atom from N4 plane (Ct–Zn) and Zn–NL bond
length (Table 2). In the molecular complex a cis effect
is noted. The increase in the Zn–NL bond strength
leads to the weakening of the bond between the zinc
and porphyrin nitrogen atom (Zn–Np) (Table 2).
The energies of formation of Zn–NL bond (Еbond) in
the composition of the molecular complex calculated
by quantum-chemical method vary in parallel with its
stability (Table 1). In the series of the complexes:
(DMF)ZnP(I) < (Prd)ZnP(I) < (Prm)ZnP(I) < (DMP)
ZnP(I) < (Py)ZnP(I) < (2-MeIm)ZnP(I) < (Im)ZnP(I)
the Еbond grows. This points to the increase in the
stability of compounds in going from dimethylform-
amide to imidazole.
ZnP(I)
On the basis of the above said it can be concluded
that both electronic and deformational factors con-
tribute considerably to the coordination properties of
the studied zinc-porphyrins in their reactions with
organic bases.
EXPERIMENTAL
Reaction ZnP + Ln = Zn(L)nP was carried out at
298 K using benzene as an inert solvent. The
experimental and calculation procedures are described
in detail in [1, 12–14]. Optical density of series of
solutions with constant concentration of
metalloporphyrin and varied concentration of extra
ligand was measured at the operating wavelengths
413–417 and 421–426 nm. The measurements were
carried out at 298K using cells of 1 cm thickness.
Errors in the temperature control are 1 K or less.
Electronic absorption spectra were registered on a
Cary-50 spectrophotometer in the range 380 to 700 nm.
The spectra were registered as diagrams and tables for
further mathematic treatment.
(Im)ZnP(I)
The treatment of dependences was carried out by
the least square method. Relative error in determina-
tion of Kstab. value is not higher than 8–10%.
The quantum-chemical calculations were carried
out by РМ3 method [2–4, 7] with PC version [15] of
Gamess program package [16]. The condition of
cancellation of the calculation was the value of
gradient 0.002 kJ mol–1 Å–1. Initial data were prepared
and results of calculation were treated using
ChemCraft version 1.3 program (author G.A. Zhurko).
As initial approximation, the bond and angles of
porphyrin macrocycle were taken those of an average
(Prz)3ZnP(I)2
Fig. 6. Structures of ZnP(I) and of its molecular complexes
with imidazole and pyrazine (quantum-chemical PM3
calculation).
metalloporphyrin structure [11], those of phenyl rings
and alkyl substituents at porphyrin and nitrogen bases
were taken from [17]. The butyl substituents were
designated in the initial approximation in the form of
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 79 No. 5 2009

1016
ZAITSEVA et al.
ZnP(I)
(Im)ZnP(I)
ΔZ, Å
○ – 1
● – 2
ΔZ, Å
0.20
0.20
0.00
0.00
0
10
20
0
10
20
–0.20
–0.20
Atom no.
(Py)ZnP(I)
Atom no.
(2-Me-Im)ZnP(I)
ΔZ, Å
ΔZ, Å
0.20
0.20
0.00
0.00
0
10
20
0
10
20
–0.20
–0.20
Atom no.
Atom no.
(DMP)ZnP(I)
(Prd)ZnP(I)
ΔZ, Å
ΔZ, Å
0.20
0.20
0.00
0.00
0
10
20
0
10
20
–0.20
–0.20
Atom no.
Atom no.
(Hi)ZnP(I)
(DMF)ZnP(I)
ΔZ, Å
ΔZ, Å
0.20
0.20
0.00
0.00
0
10
20
0
10
20
–0.20
ΔZ, Å
0.35
–0.20
Atom no.
Atom no.
(Prm)ZnP(I)
(2-Me-BzIm)ZnP(I)
ΔZ, Å
0.20
0.15
0.00
–0.05
0
10
20
0
10
20
–0.20
ΔZ, Å
0.20
Atom no.
–0.25
Atom no.
(Prz)ZnP(I) macrocycle 2
(Prz)ZnP(I) macrocycle 1
ΔZ, Å
0.40
0.00
0.20
0.00
0
10
20
–0.20
–0.40
0
10
Atom no.
20
–0.20
Atom no.
Fig. 7. Deviation of the skeleton atoms from the average plane of porphyrin macrocycle (ΔZ) for the complexes ZnP(I) and (L)nZnP(I)
(quantum-chemical PM3 calculation): (1) nitrogen atoms and (2) carbon atoms.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 79 No. 5 2009

EFFECT OF MACROCYCLE DEFORMATION
1017
frozen trans isomers. The average plane of phenyl
REFERENCES
rings was oriented at the right angle to the average
macrocycle plane. Orientation of the nitrogen bases
was assigned to provide orthogonal orientation of the
average plane of axial ligand and average plane of the
porphyrin macrocycle (for dimethylformamide parallel
orientation) and the orientation of nitrogen atom with
its lone electron pair toward central metal atom.
1 Bulatov, M.I. and Kalinkin, I.P., Prakticheskoe
rukovodstvo po fotokolometricheskim and spektro-
fotometricheskim metodam analiza (Practical Guide on
the Photocolorimetric and Spectrophotometric Methods
of Analysis), Leningrad: Khimiya, 1968.
2. Stewart, J. J. P., J. Comput. Chem., 1989, vol. 10, no. 2,
p. 209.
5,15-Di(o-nitrophenyl)-2,8,12,18-tetrabutyl-3,7,13,17-
tetramethylporphyrin was synthesized [18] and pro-
vided by Professor Semeikin (Ivanovo Chemical
Technological University).
3. Stewart, J. J. P., J. Comput. Chem., 1989, vol. 10, no. 2,
p. 221.
4. Stewart, J. J. P., J. Computer-Aided Molecular Desing,
1990, vol. 4, p. 1.
5. Tablitsy konstant skorostei and ravnovesii
gomoliticheskikh organicheskikh reaktsii (Tables of the
Homolytic Chemical Reactions Rates and Equilibrium
Constants), vol. 2, Moscow: VINITI, 1976.
6. Reichardt, C., Solvents and Solvent Effects in Organic
Chemistry, Moscow: Mir, 1991.
7. Fletcher, R., Methods of Optimization, New York:
Wiley, 1980, p. 45.
8. Zaitseva, S.V., Zdanovich, S.A., Ageeva, T.A.,
Golubchikov, O.A., and Semeikin, A.S., Koord. Khim.,
2001, vol. 27, no. 3, p. 168.
Zinc complex of 5,15-di(о-nitrophenyl)-2,8,12,18-
tetrabutyl-3,7,13,17-tetramethylporphyrin [ZnP(I)]
was synthesized by th reaction of porphyrin with 10-
fold excess of zinc acetate in benzene at 40–50 min of
reflux. The reaction was monitored by registration of
electron absorption spectra of the reaction mixture.
Disappearance of porphyrin absorption bands and
appearance of those of its zinc complex allowed
monitoring of the reaction progress. After the reaction
completion the reaction mixture was cooled and excess
of salts was removed by extraction with water. The
obtained solution of zinc complex in benzene was
evaporated. The zinc complex was purified by chro-
matography on silica gel (eluent benzene) followed by
recrystallization from chloroform. Electronic
absorption spectrum, λmax, nm (log ε): 580.0 (4.16),
545.0 (4.24) 416.0 (5.28) (benzene). Rf (Silufol): 0.85
(benzene). 1H NMR spectrum (CDCl3, internal
HMDS), δ, ppm: 10.16 s (meso-H), 8.41 m, 8.16 m,
7.99 m (PhH), 3.99 t, 2.11 m, 1.65 m, 1.14 m (С4Н9)
2.43 s (СН3).
9. Zaitseva, S.V., Zdanovich, S.A., and Koifman, O.I.,
Russ. J. Phys. Chem., 2005, vol. 79, no. 1, p. S45.
10. Zaitseva, S.V., Zdanovich, S.A., and Koifman, O.I.,
Abstract of Papers, 4th Int. Conf. of Porphyrins and
Phthalocyanines, Rome, 2006, p. 717.
11. Porfiriny: struktura, svoistva, sintez (Porphyrins:
Structure, Properties, and Synthesis), Enikolopyan, N.S.,
Ed., Moscow: Nauka, 1985.
12. Karmanova, T.V., Koifman, O.I., and Berezin, B.D.,
Koord. Khim., 1983, vol. 9, no. 6, p. 772.
13. Koroleva, T.A., Koifman, O.I., and Berezin, B.D.,
Koord. Khim., 1983, vol. 7, no. 8, p. 2007.
14. Tipugina, M.Yu., Lomova, T.N., and Ageeva, T.A., Zh.
Obshch. Khim., 1999, vol. 69, no. 3, p. 459.
15. Granovsky, A., http://classic.chem.msu.su/gran/gamess/
index.html.
16. Schmidt, M.W., Baldridge, K.K., Boatz J.A., et al.,
J. Comput. Chem., 1993, vol. 14, p. 1347.
17. Comprehensive Organic Chemistry, Barton, D.H.R. and
Ollis, Q.D., Eds., Oxford: Pergamon, 1979.
ACKNOWLEDGMENTS
This work was financially supported by the
Program of Fundamental Research, Russian Academy
of Sciences “Theoretical and experimental investiga-
tions of the nature of chemical bond and mechanisms
of the most important chemical reactions and
processes,” and by Russian Foundation for Basic
Research (grant no. 06-03-32537-a).
18. Mamardashvili, N.Zh., Semeikin, A.S., and
Golubchikov, O.A., Zh. Org. Khim., 1993, vol. 29, no. 6,
p. 1213.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 79 No. 5 2009