Magnesium(II) and cadmium(II) octaphenyltetraazaporphyrinates in metal exchange reaction with MnCl2 in DMSO

Article abstract of DOI:10.1134/S0036023617040222

Reaction kinetics of metal exchange of Mg(II) and Cd(II) octaphenyltetraazaporphynates with MnCl₂ in DMSO has been studied by spectrophotometry. Kinetic parameters of the metal exchange reaction have been determined. Possible stoichiometric rea

Full text of DOI:10.1134/S0036023617040222

ISSN 0036-0236, Russian Journal of Inorganic Chemistry, 2017, Vol. 62, No. 4, pp. 517–522. © Pleiades Publishing, Ltd., 2017.
Original Russian Text © S.V. Zvezdina, N.V. Chizhova, N.Zh. Mamardashvili, 2017, published in Zhurnal Neorganicheskoi Khimii, 2017, Vol. 62, No. 4, pp. 519–524.
PHYSICAL CHEMISTRY
OF SOLUTIONS
Magnesium(II) and Cadmium(II) Octaphenyltetraazaporphyrinates
in Metal Exchange Reaction with MnCl in DMSO
2
S. V. Zvezdina*, N. V. Chizhova, and N. Zh. Mamardashvili
Krestov Institute of Solution Chemistry, Russian Academy of Sciences, Ivanovo, 153045 Russia
*e-mail: svvr@isc-ras.ru
Received December 16, 2015
Abstract―Reaction kinetics of metal exchange of Mg(II) and Cd(II) octaphenyltetraazaporphynates with
MnCl in DMSO has been studied by spectrophotometry. Kinetic parameters of the metal exchange reaction
2
have been determined. Possible stoichiometric reaction mechanism has been suggested. Effect of solvent and
salt solvate nature on the rate of metal exchange reaction has been revealed.
DOI: 10.1134/S0036023617040222
Manganese porphyrins are the subjects of numer-
ous studies, which represent the data of X-ray diffrac-
tion analysis [1, 2], NMR spectroscopy [3, 4], coordi-
nation [5–8], electrochemical [9], and catalytic prop-
erties [10, 11]. These works showed that modification
of the macrocycle within manganese porphyrins opens
a possibility to change their physicochemical proper-
ties, those of practical importance including. To real-
ize this possibility, one should accumulate new data in
porphyrin chemistry on the structure–property rela-
tionship for these compounds. Therefore, it is of large
interest to study the reactivity of manganese porphy-
rins in the chemical reactions of metal exchange.
R
R
N
R
R
R
R
N
N
N
N
M
N
N
R
R
MgTAPPh : М = Mg, R = –C H
5
CdTAPPh : М = Сd, R = –C H
8
6
8
6
5
EXPERIMENTAL
Electronic absorption spectra were recorded on a
Varian Cary-100 spectrophotometer, H NMR spec-
Metal exchange reactions in complexes with simple
and chelate ligands are widely used in isotope
exchange [12], design of metal clusters [13], in medi-
cine as antidote for cyanide compounds [14], etc.
1
tra were obtained on a Bruker AV III-500 spectrometer
using TMS as an internal reference, IR spectra were
recorded on an Avatar 360-FT-IR-ESP spectrometer
as KBr pellets. Elemental analysis was carried out on a
Flash EA 1112 analyzer.
Magnesium(II) octaphenyltetraazaporphyrinate
was prepared by the Linstead method [17].
Octaphenyltetraazaporphyn was obtained by the
treatment of Mg(II) octaphenyltetraazaporphynate
with trifluoroacetic acid.
It should be also noted that certain metal com-
plexes with porphyrins could not be obtained by the
complexation of porphyrin ligand with metal cation.
In this case, the reaction of metal exchange of labile
metal porphyrins with appropriate metal cation is used
[
15, 16].
With the aim to develop efficient methods of syn-
thesis of poorly available metal complexes of selec-
tively modified porphyrins, we have studied the metal
Synthesis of octaphenyltetraazaporphyrin. Complex
MgTAPPh (0.1 g) was dissolved in 50 mL of trifluo-
8
roacetic acid, the solution was kept at ambient tem-
perature for 2 h, 40 mL of DMF was added, and the
mixture was poured on ice prepared from distilled
water. The precipitate was separated by filtration,
exchange reactions of magnesium (MgTAPPh ) and
8
cadmium
(CdTAPPh8)
octaphenyltetraazapor-
phynates with manganese(II) chloride in DMSO.
517

5
18
ZVEZDINA et al.
A
A
1.5
1
0
0
0
0
.8
.6
.4
.2
0
2
1
1
.0
2
0
.5
400
500
600
700
800
λ, nm
0
4
00
500
600
700 λ, nm
Fig. 1. Change in electronic absorption spectra in the
course of the metal exchange reaction of CdTAPPh with
8
Fig. 2. Change in electronic absorption spectra in the
course of the metal exchange reaction of MgTAPPh with
MnCl2 in DMSO at cMgTAPPh8 = 2.5 × 10 mol/L,
cMnCl2 = 2.5 × 10–3 mol/L at initial time (1) and after
MnCl2 in DMSO at cCdTAPPh8 = 2.5 × 10–5 mol/L,
8
cMnCl2 = 2.5 × 10–3 mol/L at initial time (1) and after
–5
45 min (2); T = 323 K.
225 min (2); T = 363 K.
washed with NaHCO solution, water, and dried.
3
Yield 0.07 g (0.0760 mmol) (70%).
where A , A , and A are the optical density of solution
0
τ
∞
at the initial point, at time τ, and after reaction com-
Electronic absorption spectrum (chloroform), λ,
nm (logε): 369 (4.63), 600 (4.32), 666 (4.52).
pletion; c and c are initial and current concentration,
0
respectively, of the Mg and Cd complexes.
Synthesis of Cd(II) octaphenyltetraazaporphyri-
nate. Octaphenyltetraazaporphyrin (0.05 g) and 0.12 g
Efficient rate constants (keff) were calculated by the
of Cd(OAc) in molar ratio 1 : 10 were dissolved in 20 equation
2
mL of DMF, 0.1 g of sodium acetate was added, and
the mixture was kept at ambient temperature for 24 h.
keff = (1/τ)ln((A – A )/(A – A )).
(2)
0
∞
τ
∞
The reaction mixture was poured into water, the pre-
Activation energy (E ) in kJ/mol was calculated by
a
cipitate was separated by filtration, washed with water, the Arrhenius equation
and dried. Yield 0.047 g (84%).
T1T
2
k 2
v
Electronic absorption spectrum (pyridine), λ, nm
E = 19.1
lg
,
(3)
=
a
(
logε): 382 (4.74), 583 (4.34), 636 (4.82).
T −T kv1
2
1
1
H NMR (DMSO-d , δ, ppm): 7.66 (d, 16H,
6
where k and kv2 are true rate constants, kv
v1
ortho-C H ), 7.44 (m, 24H, meta-C H and para-
C H ).
6
5
6
5
n
sa lt
k /c ; n is reaction order toward salt determined as
the slope of dependence logk = f(logc ).
eff
6
5
eff
salt
Manganese(II) chloride was purified according to
18]. DMSO (Merck) was used in the experiment.
≠
[
Change of activation entropy (ΔS ) in J/(mol K)
Kinetic measurement procedure was as follows: a was calculated by the equation of theory of absolute
solution of Mg and Cd pophyrazine complexes and reaction rates:
salt of known concentration were placed in a thermo-
≠
298
v
Ea
statted cell of spectrophotometer. Optical density of
solution was measured at preset time intervals at wave-
length λ = 655 nm for the metal exchange of
ΔS = 8.314 ln k
+
− 253.22.
(4)
298
Figures 1 and 2 exhibit changes in electronic
absorption spectra in the course of metal exchange
reaction of CdTAPPh and MgTAPPh with MnCl in
CdTAPPh with Mn(II) chloride and at λ = 636 nm
8
for the metal exchange reaction of MgTAPPh with the
8
8
8
2
same salt in DMSO. The initial concentration of
DMSO. Obtained experimental data are given in
Tables 1 and 2.
–5
MgTAPPh and CdTAPPh was 2.5 × 10 mol/L.
8
8
Concentration of MnCl in metal exchange reactions
2
–2
with CdTAPPh and MgTAPPh was 1.25 × 10 –
8
8
RESULTS AND DISCUSSION
–2
0
.75 × 10 mol/L. Current concentration of Mg and
Cd complexes of pophyrazine was calculated by the
equation
Metal exchange reaction can be written in general
view as follows:
с = с (A – A )/(A – A ),
(1)
MТАР + M'X (Solv)
→M'ТАР + MX (Solv)m – n, (5)
m – n n
0
τ
∞
0
∞
n
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MAGNESIUM(II) AND CADMIUM(II)
519
Table 1. Kinetic parameters of the metal exchange reaction of CdTAPPh with MnCl in DMSO (c
= 2.5 × 10–5 mol/L)
CdTAPPh8
8
2
cMnCl2 × 102,
2
k × 10 ,
4
–1
v
≠
T, K
keff × 10 , s
Ea, kJ/mol
ΔS , J/(mol K)
mol/L
L/(mol s)
1
.25
298
313
0.66*
0.53
1.47
54 ± 6
58 ± 7
57 ± 5
–152 ± 20
–140 ± 24
–146 ± 17
1.84 ± 0.02
3.76 ± 0.15
6.44 ± 0.17
3
23
33
3.01
5.15
3
1.00
298
13
0.47*
1.43 ± 0.02
0.47
1.43
3
3
23
33
3.13 ± 0.03
5.56 ± 0.23
3.13
5.56
3
0.75
298
13
0.39*
1.18 ± 0.01
0.52
1.57
3
3
23
33
2.48 ± 0.04
4.45 ± 0.13
3.31
5.93
3
*
Calculated by the Arrhenius equation.
Table 2. Kinetic parameters of the metal exchange reaction of MgTAPPh with MnCl in DMSO (c
= 2.5 ×
8
2
MgTAPPh8
–
5
10
mol/L)
cMnCl2 × 102,
2
≠
k × 10 ,
ΔS ,
4
–1
v
T, K
keff × 10 , s
Ea, kJ/mol
mol/L
L/(mol s)
J/(mol K)
1
.25
298
0.05*
1.03 ± 0.02
1.28 ± 0.03
1.57 ± 0.01
2.17 ± 0.06
0.04*
0.85 ± 0.03
1.03 ± 0.04
1.30 ± 0.04
1.78 ± 0.07
0.04
0.82
1.02
1.26
1.74
0.04
0.85
1.03
1.30
1.78
0.04
0.84
52 ± 9
–166 ± 45
–177 ± 48
–162 ± 41
3
48
353
3
3
58
63
1.00
298
52 ± 3
55 ± 9
3
48
353
3
3
58
63
0.75
298
0.03*
0.63 ± 0.03
3
48
353
0.80 ± 0.03
1.07
3
3
58
63
1.00 ± 0.05
1.39 ± 0.04
1.33
1.85
*Calculated by the Arrhenius equation.
0
where MTAP and M'TAP are metal pophyrazines;
denced from the linear dependence of log(c /сMP
)
MP
MX (Solv)
and M'X (Solv)
are metal solvato
m – n
n
m – n
n
on reaction time τ. The character of this dependence is
complexes.
represented in Fig. 3.
Experimental data show that the rate of metal
exchange reaction of CdTAPPh and MgTAPPh with
Our study of metal exchange reaction of
8
8
MnCl in DMSO obeys first-order rate law toward MgTAPPh and CdTAPPh with MnCl in DMSO
2
8 8 2
magnesium and cadmium complexes. This is evi- revealed that reaction order toward the salt deter-
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 62 No. 4 2017

5
20
ZVEZDINA et al.
log(c0
/cCdTAPPh8)
–
logkeff 1
CdTAPPh
8
4.3
0.50
0.45
0.40
0.35
0.30
0.25
0.20
3
4.2
1
2
3
2
4.1
1
4.0
3.9
4
3
.8
.7
0
0
.15
.10
3
0
.05
3.6
2
.55
2.60
2.65
2.70
2.75
2.80
2.85
0
500 1000 1500 2000 2500 3000 3500 4000 4500
–logcMnCl
2
τ, s
Fig. 4. Dependence of logkeff1 on logcMnCl2 in the metal
Fig. 3. Time dependence of log(c0
CdTAPPh8
/cCdTAPPh8
)
exchange reaction of MgTAPPh with MnCl in DMSO at
8
2
for the reaction of CdTAPPh with MnCl in DMSO at
8
2
T = 348 (1), 353 (2), 358 (3), 363 K (4).
cMnCl2 = 2.5 × 10–3 mol/L and T = 313 (1), 323 (2),
33 K (3).
3
leads to it out-of-plane arrangement and hence more
efficient ion solvation by coordinating solvent. All this
in combination with activation of out-of-plane vibra-
tions of N–M bond facilitates the reaction (5).
mined as the slope of linear dependence logk
=
eff
f(lоgc ) equals to one (Figs. 4 and 5).
salt
Thus, the kinetic equation of metal exchange reac-
298
True rate constants (kv ) of the metal exchange
tion of MgTAPPh and CdTAPPh with MnCl in
8
8
2
reaction of MgTAPPh and CdTAPPh with MnCl in
8
8
2
DMSO can be written in general view as:
DMSO were compared. The metal exchange reaction
of MnCl in DMSO was found to proceed with
–
dcMP/dτ = k [MTAP][MnCl ],
(6)
2
v
2
CdTAPPh 13 times faster than with MgTAPPh
8
8
where MTAP = MgTAPPh and CdTAPPh .
8
8
(
Tables 1 and 2). This is likely to result from the low
On the basis of experimental data (Tables 1 and 2),
degree of covalence of coordination σ Cd–N bonds in
the complex, for which the contribution of ionic com-
ponent is rather considerable, and large ionic radius of
we found that the metal exchange reaction of
MgTAPPh and CdTAPPh with MnCl in DMSO
8
8
2
proceeds via bimolecular associative mechanism. An metal, which is incompatible with the size of coordi-
intermediate binuclear complex forms at the first nation cavity of pophyrazine ligand [19].
bimolecular stage:
(
Solv) MTAP + M'X (Solv)
m 2 n−2
–
logkeff 2
(
7)
↔
(Solv) MTAP ⋅M'X (Solv) + 2Solv.
m 2 n−4
4
.0
1
It can form immediately after mixing solutions and
then can be readily determined by spectra, or this stage
may be retarded. The rate of formation of intermediate (8)
is supposed to be dependent on the strength of MTAP
and M'TAP complexes, retarding as MTAP strength
rises and accelerating as M'TAP strength increases in
reaction (6).
3.9
3
3
3
3
3
3
3
.8
.7
.6
.5
.4
.3
.2
2
3
At the second slow monomolecular stage, the
intermediate dissociates to give final products:
3
.1
3.0
(
Solv) MТАP ⋅ M'X (Solv)
m 2 n – 4
2
.55
2.60
2.65
2.70
2.75
2.80
2.85
↔
[(Solv) M⋅⋅⋅ТАP⋅⋅⋅M'X (Solv) ]≠
(8)
–logcMnCl2
m
2
n – 4
→
МX (Solv) + M'ТАP(Solv)n – 4.
2 m
The size of metal ion in the initial Mg or Cd com-
plex is one of factors that favor metal exchange. The
Fig. 5. Dependence of logkeff2 on logcMnCl2 in the metal
exchange reaction of CdTAPPh with MnCl in DMSO at
8
2
large size of Cd(II) ion (in the case of CdTAPPh )
T = 313 (1), 323 (2), 333 K (3).
8
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MAGNESIUM(II) AND CADMIUM(II)
521
We revealed the effect of nature of salt solvate on m, 745 m, 610 m (pyrrole rings), 535 m, 467 m (M–
the rate of metal exchange reaction. The comparison N). For C H N ClMn anal. calcd. (%): C, 76.00; H,
6
4
40
8
of true rate constants of metal exchange reactions of 3.99; N, 11.08. Found (%): C, 76.08; H, 4.07; N, 11.01.
CdTAPPh with MnCl , CuCl , and CоCl [20] in
8
2
2
2
The metal exchange reaction of MgTAPPh
8
DMSO showed that the metal exchange reaction of
–5
(
1
c(
= 2.5 × 10 mol/L) with MnCl (c
=
MgTAP(PhBr)
2
8
2
MnCl2
CdTAPPh with CоCl proceeds 4 times faster than
8
2
.25 × 10– mol/L) in DMSO was found to be
with MnCl , while that with CuCl occurs very fast
2
2
extremely slow at T = 363 K.
even at T = 288 K. Thus, the studied metal chlorides
in terms of the rate of metal exchange with CdTAPPh
We have compared true rate constants for the metal
8
in DMSO can be arranged in the following order:
exchange reactions of CdTAPPh and MgTAPPh
8 8
with MnCl in DMSO and DMF [20, 23]. The metal
2
MnCl < CоCl < CuCl .
(9)
The comparison of true rate constants of metal
exchange reaction of MgTAPPh with MnCl and
2
2
2
exchange reaction of MnCl was found to proceed
2
slower in DMSO than DMF by 3 and 400 times for
MgTAPPh and CdTAPPh , respectively. This is
8
2
8
8
CоCl [21] in DMSO showed that the metal exchange
2
caused by the fact that the strength of solvate shell of
salt as a rule increases with solvating ability of solvent,
thus hindering metal exchange. Therefore solvent with
moderate electron-donating properties will be the
most efficient in the metal exchange reaction.
reaction of MgTAPPh with CоCl proceeds 22 times
8
2
faster than with MnCl , which agrees well with the
2
series (9).
It is known [22] that Mn2+ undergoes oxidation to
Mn3 upon synthesis of porphyrin complexes under
common conditions and in complexes with porphyrins
contain acido ligand as a counterion (chloride in our
case). The distinctive feature of (X)Mn(III)P (P is
+
ACKNOWLEDGMENTS
This work was supported by the Russian Science
1
dianion of porphyrin or azaporphyrin, X is acido Foundation, project no. 14-13-00232. H NMR spec-
ligand) is the presence of strong electron-withdrawing tral studies were performed with the use of equipment
interaction of metal atom with porphyrin ligand on of the Shared Facility Center, Upper Volga Regional
account of direct (N → Mn) p(π)–d(π) interaction Center of Physicochemical Studies.
that coincides in direction with dative σ bond. The
introduction of acido ligand into inner coordination
sphere changes molecule geometry resulting in the
shift of bands in electronic absorption spectrum of Mn
complex of octaphenyltetraazaporphyrin as compared
with CdTAPPh and MgTAPPh complexes.
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Translated by I. Kudryavtsev
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