Coordination properties of μ-carbidodimeric iron(IV) 2,3,7,8,12,13,17,18-octapropyltetraazaporphyrinate and 5,10,15,20-tetraphenylporphyrinate in reactions with nitrogen-containing bases

Article abstract of DOI:10.1134/S0036023617090194

The equilibria of μ-carbidodimeric iron(IV) 2,3,7,8,12,13,17,18-octapropyltetraazaporphyrinate and 5,10,15,20-tetraphenylporphyrinate in reactions with nitrogen-containing bases in an inert solvent were studied spectrophotometrically. The equilibrium constants of the studied processes and the compositions of molecular complexes were determined. The effect of the electronic and conformation factors of a macrocycle and the nature of the base on the equilibrium constant was pointed out. A comparative analysis of the substrate specificity of the studied compounds was performed.

Full text of DOI:10.1134/S0036023617090194

ISSN 0036-0236, Russian Journal of Inorganic Chemistry, 2017, Vol. 62, No. 9, pp. 1257–1266. © Pleiades Publishing, Ltd., 2017.
Original Russian Text © S.V. Zaitseva, S.A. Zdanovich, E.V. Kudrik, O.I. Koifman, 2017, published in Zhurnal Neorganicheskoi Khimii, 2017, Vol. 62, No. 9, pp. 1265–1273.
PHYSICAL CHEMISTRY
OF SOLUTIONS
Coordination Properties of μ-Carbidodimeric Iron(IV)
2,3,7,8,12,13,17,18-Octapropyltetraazaporphyrinate
and 5,10,15,20-Tetraphenylporphyrinate
in Reactions with Nitrogen-Containing Bases
S. V. Zaitsevaa, *, S. A. Zdanovicha, E. V. Kudrikb, and O. I. Koifmana, b
aKrestov Institute of Solution Chemistry, Russian Academy of Sciences, Ivanovo, 153045 Russia
bIvanovo State University of Chemical Technology, Ivanovo, 153000 Russia
*e-mail: svz@isc-ras.ru
Received June 24, 2016
Abstract⎯The equilibria of μ-carbidodimeric iron(IV) 2,3,7,8,12,13,17,18-octapropyltetraazaporphyrinate
and 5,10,15,20-tetraphenylporphyrinate in reactions with nitrogen-containing bases in an inert solvent were
studied spectrophotometrically. The equilibrium constants of the studied processes and the compositions of
molecular complexes were determined. The effect of the electronic and conformation factors of a macrocycle
and the nature of the base on the equilibrium constant was pointed out. A comparative analysis of the sub-
strate specificity of the studied compounds was performed.
DOI: 10.1134/S0036023617090194
The search and creation of systems that can model were proven to be μ-nitrido- and μ-carbidodimeric
biological processes and act as efficient catalysts for
redox reactions, are one of the most important direc-
tions in contemporary chemistry. Despite numerous
studies in this field [1], it remains topical to investigate
the effects of the structure and coordination ability of
an artificial system on its catalytic properties and pos-
sible conversion in the course of chemical reactions.
Tetrapyrrole complexes of transition metals can suc-
sessfully act as an active component of such a system
[1–8].
tetrapyrrole macrocyclic iron complexes.
The activity of an enzyme usually begins with its
bonding to a substrate, which must be converted by
this enzyme. For this reason, the study of the substrate
specificity of dimeric tetrapyrrole iron complexes is
necessary to create models of biosystems and under-
stand the mechanisms of enzymatic processes.
For this purpose, the reaction between μ-carbi-
dodimeric iron(IV) octapropyltetraazaporphyrinate
and tetraphenylporphyrinate (μ-С(FeIVOPrTAP)2 and
Until quite recently, dimeric complexes were con-
sidered to be catalytically inert in comparison to
monomeric complexes and were ignored as catalysts.
There currently are some works in which μ-oxodi-
meric complexes of iron phthalocyaninates are shown
to exhibit good catalytic properties in the oxidation of
aromatic compounds and alcohols. Binuclear iron
complexes, as well as mononuclear ones, activate
some oxidants (hydrogen peroxide, organic peroxides,
iodobenzene, compounds containing high-valent
iodine, etc.) with the formation of high-valence oxo
forms characterized by high catalytic activity [3–10].
However, despite their catalytic activity, the structures
containing oxygen bridges are readily prone to trans-
formation, which complicates their study. The most
μ-С(FeIVTPP)2, respectively) with nitrogen-contain-
ing substrates (L is diethylamine (Et2N), imidazole
(Im), 1-methylimidazole (1-MeIm), 2-methylimida-
zole (2-MeIm), and pyridine (Py)) acting as sources
of electrons was studied. The use of organic bases is
associated with their ability to incorporate into medi-
cines with bactericidal, antitumoral, antiischemic,
and antiallergic properties [11, 12]. These substrates
can readily form complexes with transition-metal ions
[13–17]. The presence of nitrogen-containing bases in
the inner coordination sphere of the complex may
have an appreciable effect on the biological and cata-
lytic activity of both these bases in particular and the
stable analogues of the active site of a natural enzyme compound as a whole.
1257

1258
ZAITSEVA et al.
Pr
Pr
N
N
Pr
N
N
I
N
Fe
C
Pr
Pr
N
N
N
I
Fe
N
N
N
Pr
Pr
N
N
Pr
Pr
Pr
C
Pr
Pr
N
Pr
N
N
N
II
N
Fe
N
II
Fe
N
N
N
N
N
Pr
Pr
Pr
μ -C(FeIVOPrTAP)2
μ -C(FeIVTPP)2
EXPERIMENTAL
thereupon the μ-carbidodimeric tetrapyrrole iron(IV)
complex precipitated. The wet product was filtered out
and washed with water. The complex was purified by
column liquid adsorption chromatography (aluminum
oxide; dichloromethane eluent). The yield was 60%
for μ-С(FeIVOPrTAP)2 and 40% for μ-С(FeIVTPP)2.
Electronic absorption spectra (EASs) in benzene
were recorded on a Cary 50 spectrophotometer at 295 K
in the region 400–700 nm.
The absorbances of working solutions at a constant
metal porphyrinate concentration and different
organic base concentrations were determined at work-
ing wavelengths of 411–595 nm in cells with a thick-
ness of 1 cm.
1H NMR spectra were recorded on a Bruker
Avance-500 spectrometer in CDCl3 (hexamethyldisi-
lane (HMDS) internal standard).
The composition of the reaction mixture was ana-
lyzed by mass spectra taken on a Bruker microTOF
electrospray ionization mass spectrometer.
IR spectra were recorded on a Bruker Vertex 80
FT-IR spectrometer using a Harrick MVP2 SeriesTM
attachment (the prism material was diamond) in the
region 4000–400 cm–1 (64 scans in each case on the
average) at a resolution of 2 cm–1 at room temperature
by the attenuated total reflection (ATR) method in
benzene and as KBr pellets.
μ-С(FeIVOPrTAP)2 EAS in benzene (λmax, nm
logε): 581 (4.82), 550 (4.63), 480 (4.43), 313 (5.02).
1H NMR (CDCl3, HMDS internal standard), δ,
(ppm): 4.15–3.59 m (32H, propyl substituent α-CH2),
2.31–2.17 m (32H, propyl substituent α-CH2), 1.34–
0.92 m (48H, propyl substituent CH3).
IR spectrum (ATR), benzene 969 cm–1:
ν(Fe=C=Fe); KBr 971 cm–1: ν(Fe=C=Fe).
ESI-MS: m/z = 1422.8.
μ-С(FeIVTPP)2 EAS in benzene (λmax, nm (logε)):
608.9 (4.62), 517.0 (4.73), 411 (5.01).
IR spectrum (ATR), benzene 954 cm–1:
ν(Fe=C=Fe).
ESI-MS: m/z = 1349.7.
The reaction between the dimeric complex and
nitrogen-containing bases was studied spectrophoto-
metrically [19]. The equilibrium constants (Keq) were
determined by Eq. (4) derived with consideration for
the mass-action law Keq = [(L)nMP]/[MP][L]n and
the Bouguer–Lambert–Beer law A = εcl (where A is
the solution absorbance, ε is the molar extinction
coefficient, с is the absorbing compound concentra-
tion, mol/L, and l is the solution layer thickness).
General method for the synthesis of μ-carbidodi-
meric
iron(IV)
2,3,7,8,12,13,17,18-octaprop-
yltetraazaporphyrinate and 5,10,15,20-tetraphenyl-
porphyrinate [18]. A monomeric iron(III) complex
(0.14 mmol) was dissolved in a flask filled with isopro-
panol (30 mL) and equipped with an air condenser. To
this solution, potassium hydroxide (1 g) was added.
The resulting mixture was boiled for 25 min under an
argon atmosphere. Afterwards, chloroform (10 mL)
was carefully poured to the boiling solution. The com-
pletion of the reaction was established by the change of
the solution in color (from brown–red to violet). After
cooling, water (100 mL) was added to the solution,
The concentration of dimeric complex [MP] was
determined with allowance for a change in the solution
absorbance as
0
сМР
=
(Аeq – А∞/А0 – А∞),
(1)
сМР
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COORDINATION PROPERTIES OF μ-CARBIDODIMERIC
is the initial concentration of a dimeric
1259
сМ0 Р
L
where
complex in solution, and A0, Aeq, and A∞ are, respec-
tively, the absorbances of a dimeric complex and an
equilibrium mixture at a certain concentration of the
base and the molecular complex.
The extracomplex [(L)nMP] concentration was
determined by the relationship for a mixture of two
colored compounds as
FeIV
FeIV
C
2L
C
FeIV
FeIV
L
А − А
А − А
0
0
MP
0
MP
eq
0
eq
0
(2)
c = c − c
⇒ c = c
.
MP
А − А
А − А
∞
0
∞
0
The concentration of the free extraligand [L]n in
solution with allowance for extracoordination was cal-
culated as
is accompanied by a change in intensity and the
bathochromic shift of the band at λ = 581 nm by 7–14 nm
for μ-С(FeIVOPrTAP)2 and the band at λ = 411 nm by
1–10 nm for μ-С(FeIVTPP)2 with retention of isosbes-
tic points in the electronic absorption spectra of the
complexes (Fig. 1). Similar changes in EASs indicate
the formation of a metal–substrate bond [17, 28–31].
In the considered case, the donor–acceptor com-
plexes μ-С(FeIVOPrTAP)2 and μ-С(FeIVTPP)2 with
N-bases are formed. Noteworthy, the spectral
response to a change in the composition of the com-
plex is different and depends on the nature of the mac-
rocyclic ligand and the substrate (Figs. 1 and 2). The
electronic absorption spectra of the studied com-
pounds feature a broadened Q-band due to the exciton
interaction between two neighboring μ-chromophores
[32]. The electronic absorption spectrum of
μ-С(FeIVOPrTAP)2 with N-bases features a series of
charge-transfer bands, which are less intense but strongly
pronounced, in contrast to initial μ-С(FeIVOPrTAP)2, in
the long-wave region between the Soret band at λ =
320–322 nm and the intense Q-band at λ = 587–595 nm
(Fig. 2). The intensities of these bands depend on the
electron density on the iron atom [32], which varies
due to the interaction between this atom and a sub-
strate molecule. The most intense charge-transfer
bands are observed for the 1-MeIm complex (Fig. 2).
А − А
0
cL = cL0 − c
,
eq
0
(3)
MP
А − А
∞
0
where 0 is the initial concentration of the base in ben-
сL
zene solution.
With account for Eqs. (1) and (2), the expression
for the equilibrium constant takes the form
А − А
(
(
)
)
1
eq
0
(4)
.
K
=
eq
сL0 − сM0 P А − А
(
)
А − А
)
А − А
(
∞
eq
eq
0
∞
0
The values of Keq and average deviations were opti-
mized using the Microsoft Excel software. The relative
error was ≈ 10–15%.
The quantum-chemical calculations of the geo-
metric parameters (bond lengths and bond angles) and
energy parameters (bond energies) of isolated mole-
cules were performed by the РМ3 method [20–22]
using the PC-version [23] of the Gamess software
suite [24]. The calculation completion condition was
the specified gradient of 0.0004 kJ/(mol Å). The input
of initial data and the processing of results were per-
formed by the ChemCraft software, version 1.3 [25].
The initial approximation of bond lengths and angles
in a macrocycle was specified with consideration for
the data on the averaged structure of metal porphyri-
nates [26]. The geometric characteristics of alkyl sub-
stituents and organic substrates correspond to the lit-
erature data [27].
The coordination bonding is a very fast process.
For the studied compounds, the formed complex has
1 : 2 composition as determined by the restrictedly
logarithmic method [19] (the slope of the linear
log[(Aeq – A0)/(А∞ – Aeq)] versus logcL plot is 2) (Fig. 3).
It is noteworthy that μ-С(FeIVTPP)2 coordinates one
base molecule in the reaction with 2-methylimidazole
(the slope of the linear log[(Aeq – A0)/(А∞ – Aeq)] ver-
sus logcL plot is 1) (Fig. 3).
RESULTS AND DISCUSSION
The coordination bonding of organic bases by
μ-carbidodimeric iron(IV) octapropyltetraazapor-
phyrinate and tetraphenylporphyrinate was studied
spectrophotometrically within a broad range of substrate
The formation of a molecular complex is also con-
firmed by IR and mass spectra (Figs. 4 and 5). A char-
acteristic feature of the IR spectra of μ-carbidodimeric
complexes is the band of of the asymmetric stretching
vibrations of the bridged moiety: νas(МеCМе) [31]. In
concentrations (cEt NH = 1.6 × 10–3–4.8 × 10–1 mol/L,
2
c1-MeIm = 4.6 × 10–4–2.5 × 10–1 mol/L, c2-MeIm = 1.96 ×
10–4–2.9 × 10–2 mol/L, cIm = 4.5 × 10–4–2.5 ×
10‒2 mol/L, cPy = 6.5 × 10–3–5.2 × 10–1 mol/L). The
studied reaction
the IR spectrum of μ-С(FeIVOPrTAP)2, the band of
Fe=C=Fe vibrations appears at ν = 971 cm–1 (KBr)
(Fig. 4). The addition of imidazole or diethylamine to
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1260
ZAITSEVA et al.
411
1
2
A
11
12
μ-C(FeIVTPP)2
572
400
500
595
600
λ, nm
A
12
11
581
1
2
μ-C(FeIVOPrTAP)2
500
600
700
λ, nm
Fig. 1. Transformation of the electronic absorption spectrum of μ-carbidodimeric iron(IV) octapropyltetraazaporphyrinate and
iron(IV) μ-tetraphenylporphyrinate during the reaction with 1-methylimidazole in benzene: (1) complex (с
= 6.84 ×
complex
‒6
–3
–1
10 mol/L), (2)–(11) complex with intermediate 1-methylimidazole concentrations c
= 7.6 × 10 –2.0 × 10 mol/L
1-MeIm
IV
–4
–2
IV
(for μ-С(Fe ТРP) and c
= 4.65 × 10 –1.16 × 10 mol/L (for μ-С(Fe OPrTAP) ), and (12) complex with excess
2
1-MeIm
2
–1
1-methylimidazole (c
= 2.56 × 10 mol/L).
1-MeIm
In the IR spectrum of μ-С(FeIVТРP)2, the
a solution of the dimeric complex leads to the low-fre-
quency shift of this band by 34 and 2 cm–1, respectively
(Fig. 4). The presence of 2-methylimidazole in the
working solution of μ-С(FeIVOPrTAP)2 produces the
high-frequency shift of the Fe=C=Fe vibration band
by 24 cm–1. The observed shifts of the vibration band
ν(Fe=C=Fe) indicate that the iron atom has changed
its position with respect to the coordination plane due
to the formation of the iron–substrate bond.
Fe=C=Fe vibration band appears at ν = 954 cm–1
(benzene) (Fig. 4). The presence of 1-methylimidaz-
ole and imidazole in the reaction mixture leads to the
shift of ν(Fe=C=Fe) signals to the low-frequency
region by 18–49 cm–1, respectively. The Fe–NL vibra-
tion band appears at ν = 419 cm–1 for imidazole and
411 cm–1 for 1-methylimidazole. The ν(Fe–N) signals at
ν = 461 cm–1 also shift to the red by 26–37 cm–1 (Fig. 4).
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COORDINATION PROPERTIES OF μ-CARBIDODIMERIC
1261
587
584
A
A
543
524
μ-C(FeIVOPrTAP)2
μ-C(FeIVOPrTAP)2 + Py
593
593
546
548
423
μ-C(FeIVOPrTAP)2 + Im
μ-C(FeIVOPrTAP)2 + Et2N
595
584
561
548
528
494
μ-C(FeIVOPrTAP)2 + 2-MeIm
μ-C(FeIVOPrTAP)2 + 1-MeIm
400
600
800
400
600
800
λ, nm
λ, nm
IV
Fig. 2. Electronic absorption spectra of μ-С(Fe OPrTAP) donor–acceptor complexes with N-bases.
2
μ-C(FeIVOPrTAP)2
μ-C(FeIVTPP)2
(Aeq–A0)
(A∞–Aeq)
(Aeq–A0)
(A∞–Aeq)
log
log
1-MeIm
1-MeIm
Py
1.5
1.0
0.5
0
tan α = 2
Et2N
1
Et2N
2-MeIm
2
1
Im
2-MeIm
Im
0
0
2
3
3
–log cL
–log cL
–1
1
–0.5
–1.0
–1.5
–2.0
–1
–2
–3
tan α = 2
Fig. 3. Log[(A – A )/(А – A )] versus logc plots for the reactions of μ-carbidodimeric iron(IV) octapropyltetraazaporphy-
eq
0
∞
eq
L
rinate and iron(IV) μ-tetraphenylporphyrinate with nitrogen-containing substrates. А , А , and А are the absorbances of solu-
0
eq
∞
tions at the working wavelength for iron dimers, an equilibrium mixture, and a molecular complex, respectively.
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1262
ZAITSEVA et al.
μ-C(FeIVOPrTAP)2
μ-C(FeIVTPP)2
μ-C((Im)FeIVOPrTAP)2
μ-C((Im)FeIVTPP)2
μ-C((2-MeIm)FeIVOPrTAP)2
μ-C((1-MeIm)FeIVTPP)2
μ-C((Et2N)FeIVOPrTAP)2
1500
1000
500
ν, cm–1
1000
500
ν, cm–1
IV
IV
–6
Fig. 4. IR spectra of μ-С(Fe OPrTAP) (KBr) and μ-С(Fe ТРP) (benzene; с
= 6.84 × 10 mol/L, c
=
2
2
μ-С(FeIVТРP)2
1-MeIm
–2
–3
1.88 × 10 mol/L, c = 4.9 × 10 mol/L) and their complexes with nitrogen-containing bases.
Im
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COORDINATION PROPERTIES OF μ-CARBIDODIMERIC
1263
I, ×107
1558.324
I, ×107
μ-C((Et2N)FeIVOPrTAP)2
1568.088
μ-C((Im)FeIVOPrTAP)2
4
2
1.0
0.5
0
0
1567
m/z
m/z
m/z
m/z
1550
I, ×107
1485.064
1555
1560
1569
1571
I, ×107
μ-C((Im)FeIVTPP)2
μ-C((2-MeIm)FeIVTPP)2
1431.302
1.5
2
1
1.0
0.5
0
0
m/z
1440
1486
1488
1490
1430
1435
I, ×107
μ-C((Et2N)FeIVTPP)2
1495.089
4
2
0
1495
1500
IV
IV
–5
Fig. 5. Mass spectra of μ-С(Fe OPrTAP) and μ-С(Fe ТРP) (с
= 3.5 × 10 mol/L) in the presence of bases (с
=
2
2
complex
–2
Im
–3
–3
5.35 × 10 mol/L, c
= 6.74 × 10 mol/L, c
= 1.52 × 10 mol/L).
2-MeIm
Et2NH
The composition of studied reaction products was processes were determined as described in [33, 34] by
proven by mass spectra using the reaction between spectrophotometric titration using Eq. (1) (see Exper-
imidazole, 2-methylimidazole, and diethylamine as imental) (Table 1).
an example. The signals of molecular peaks m/z =
Based on the obtained data (Table 1), it has been
1485 and 1558 in the mass spectra correspond to the
established that the stability of molecular complexes
ions of μ-С((Im)FeIVTPP)2 and [μ-С((Im)FeIVOPr-
μ-С(FeIVOPrTAP)2 grows in the series of bases as Py <
TAP)2], the signals m/z = 1495 and 1568 correspond to
2-MeIm < Im < 1-MeIm. The more stable is the sub-
the
ions
of
μ-С((Et2NH)FeIVTPP)2
and
strate, the higher Keq is. The stability of the
μ-С((Et2NH)FeIVOPrTAP)2, and the signal m/z =
1431 belongs to the ion of μ-С(FeIVTPP)2(2-MeIm)
(Fig. 5).
μ-С(FeIVТРP)2 complexes with N-bases grows as Py <
Im < 1-MeIm (Table 1). 2-Methylimidazole falls out
thistrend, as μ-С(FeIVTPP)2(2-MeIm) differs from
the other complexes in its structure. Diethylamine
does not fit into the series due to the steric hindrances
produced by the bulky structure of the base molecule.
The degree of the substrate specificity of complexes
is caused by the stability of the receptor–substrate sys-
tem. The equilibrium constants (Keq) of the studied
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1264
ZAITSEVA et al.
Table 1. Equilibrium constants for reactions between iron tetrapyrrole complexes with nitrogen-containing bases and the
basicity factors of nitrogen-containing substrates
298 × 10–3, L2/mol2
pKa**
logKeq
lFe=С, Å
–Еb***, kcal/mol
Complex
Keq
μ-С((Et2NH)FeIVTPP)2
10.93
0.313 0.059
8.56 0.81
2.50
1.57
1.91
1.55
1.96
1.68
1.69
1.54
1.95
1.54
1.56
1.57
1.88
1.57
1.89
1.58
1.86
64.28
68.17
86.23
69.74
71.72
72.65
82.50
μ-С((1-MeIm)FeIVTPP)2
μ-С((Im)FeIVTPP)2
7.30
6.65
5.89
5.29
10.93
7.30
6.65
5.89
5.29
3.93
3.31
2.33
0.69
3.15
5.35
4.88
4.00
2.88
2.06 0.53
0.213 0.021*
0.0049 0.0004
1.41 0.16
μ-С(FeIVTPP)2(2-MeIm)
μ-С((Py)FeIVTPP)2
62.54
61.23
71.55
73.16
79.64
95.39
76.85
85.37
73.79
77.64
69.52
70.07
μ-С((Et2NH)FeIVOPrTAP)2
μ-С((1-MeIm)FeIVOPrTAP)2
μ-С((Im)FeIVOPrTAP)2
μ-С((2-MeIm)FeIVOPrTAP)]
224 81
75.9 9.21
9.76 0.87
0.768 0.072
1.57
1.88
1.69
1.67
μ-С((Py)FeIVOPrTAP)2
298
* Dimension for
is L/mol.
Keq
** pK are given for Et NH, 1-MeIm, Im, 2-MeIm, and Py [35].
a
2
*** –Е is the bonding energy between the iron cation and the nitrogen atom of the substrate.
b
When comparing the substrate specificities of the and corrugation (macrocycle II), and has greater steric
distortions in comparison with μ-С(FeIVOPrTAP)2, in
which the structure of one macrocycle (I) is nearly pla-
nar, while the structure of the second macrocycle (II) has
a slight corrugation deformation (Fig. 6). The average
deviation of the macrocycle atoms from the average
plane of the molecule is 0.68 Å (I), 0.39 Å (II) and
0.07 Å(I), 0.20 Å (II) for μ-С(FeIVТРP)2 and
studied μ-carbidodimeric iron complexes with respect
to the nitrogen-containing bases used in this work, we
should mention that μ-С(FeIVOPrTAP)2 forms stron-
ger donor–acceptor bonds with organic substrates
than μ-С(FeIVТРP)2 (Table 1). This is caused by the
effect of the basicity of the macrocyclic ligand on the
effective positive charge of the iron atom, whose value
promotes the formation of more or less stable molecu-
lar complexes. The order of decreasing basicities of
macrocyclic ligands (H2TPP > H2TAP > H2tr-BuPc >
H2Pc [10]) explains our results.
The presence of electron-donating substituents in
μ-С(FeIVOPrTAP)2 makes its own contribution to the
decrease in the effective positive charge on the iron
atom and, in the long run, has an effect on the strength
of the metal–substrate bond. In the absence of propyl
substituents, the formation of more stable molecular
complexes can be expected.
μ-С(FeIVOPrTAP)2, respectively. The formation of a
donor–acceptor complex is accompanied by a
decrease in torsional distortions and an ambiguous
change in the FeIV=С bond length (lFe=C) (1.54 (I),
1.79 (II), and 1.63 Å (I, II)) in initial μ-С(FeIVТРP)2
and μ-С(FeIVOPrTAP)2 and, in the case of
μ-С(FeIVТРP)2, also by an increase in the torsion of
pyrrole moieties (Table 1, Fig. 6). The calculated ener-
gies (Еb) of the bonds between the iron cation and the
nitrogen atom of the substrate correlate with the sta-
bility constants (Table 1).
We should also mention that the distortion of the
Hence, the comparative analysis of the coordina-
complex has an effect on the increase in basicity of the
macrocycle and steric hindrances upon coordination. tion abilities of μ-С(FeIVТРP)2 and μ-С(FeIVOPr-
The quantum-chemical calculations [20–24] of iso-
TAP)2 draw us to the following conclusion: the fast
attainment of equilibrium in the coordination bonding
lated molecules show that μ-С(FeIVТРP)2 has a mixed
type of distortion, namely, “saddle” (macrocycle I) of N-containing substrates by the complex; an appre-
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COORDINATION PROPERTIES OF μ-CARBIDODIMERIC
1265
μ-C(FeIVOPrTAP)2
μ-C(FeIVOPrTAP)2
μ-C((1-MeIm)
FeIVOPrTAP)2
mc I
ΔZ, Å
ΔZ, Å
ΔZ, Å
mc I
mc II
0.8
0.8
0.8
–0.2
–0.2
–0.2
0
10
20
0
10
20
0
10
20
–1.2
–1.2
–1.2
Atom no.
Atom no.
Atom no.
μ-C(FeIVTPP)2
μ-C(FeIVTPP)2
μ-C((2-MeIm)-
FeIVOPrTAP)2
mc II
ΔZ, Å
ΔZ, Å
ΔZ, Å
mc I
mc II
0.8
0.8
0.8
–0.2
–0.2
–0.2
0
10
20
0
10
20
0
10
20
–1.2
–1.2
–1.2
Atom no.
Atom no.
Atom no.
IV
μ-C(2-MeIm)(FeIVTPP)2
ΔZ, Å
ΔZ, Å
μ-C(2-MeIm)(Fe TPP)2
mc I
mc II
0.8
0.8
–0.2
–0.2
0
10
20
0
10
20
–1.2
–1.2
Atom no.
Atom no.
Fig. 6. Deviation of the framework atoms of the macrocycle along axis z from its average plane for the studied dimeric compounds
and their donor–acceptor complexes with 1-MeIm and 2-MeIm according to quantum-chemical calculation by the PM3
method: (s) nitrogen atoms, (d) carbon atoms, mc I is the first macrocycle, mc II is the second macrocycle.
4. Q.-Z. Ren, Y. Yao, X.-J. Ding, et al., Chem. Commun.,
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ciable spectral response, which dependson the basicity
of the substrate, to the formation of the receptor–sub-
strate bond; and moderately high Keq for the substrate
specificity of the complex, determine the priority use-
fulness of μ-carbidodimeric iron(IV) octaprop-
yltetraazaporphyrinate as a receptor for nitrogen-con-
taining bases.
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ACKNOWLEDGMENTS
This work was supported by the Russian Founda-
tion for Basic Research (project no. 15-03-04327-a).
The IR spectra were studied on the equipment of the
Shared Facilities Center “Upper Volga Regional Cen-
ter of Physicochemical Studies”.
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Translated by E. Glushachenkova
10.1002/jcc.540141112
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