Metal Exchange Reaction of Cd(II) 5,10,15,20-Tetra(4-chlorophenyl)porphyrinate with Copper and Zinc Chlorides in DMSO

Article abstract of DOI:10.1134/S1070363220110134

Abstract: The metal exchange reactions of Cd(II)5,10,15,20-tetra(4-chlorophenyl)porphyrinate with CuCl₂and ZnCl₂ in DMSO were studied by the spectrophotometricmethod. The kinetic parameters of the metal exchange reactions were determined.A possible reaction mechanism was proposed. Zinc(II) and copper(II)5,10,15,20-tetra(4-chlorophenyl)porphyrinates were synthesized by the complexformation reactions of zinc(II) and copper(II) acetates with5,10,15,20-tetra(4-chlorophenyl)porphyrin and by metal exchange of its cadmiumcomplex with ZnCl₂ and CuCl₂ indimethylformamide. The resulting compounds were identified by electronicabsorption and ¹H NMR spectroscopy and massspectrometry methods.

Full text of DOI:10.1134/S1070363220110134

ISSN 1070-3632, Russian Journal of General Chemistry, 2020, Vol. 90, No. 11, pp. 2105–2110. © Pleiades Publishing, Ltd., 2020.
Russian Text © The Author(s), 2020, published in Zhurnal Obshchei Khimii, 2020, Vol. 90, No. 11, pp. 1732–1737.
Metal Exchange Reaction of Cd(II)
5,10,15,20-Tetra(4-chlorophenyl)porphyrinate with Copper
and Zinc Chlorides in DMSO
S. V. Zvezdinaa,*, N. V. Chizhovaa, and N. Zh. Mamardashvilia
a G.A. Krestov Institute of Solution Chemistry of the Russian Academy of Sciences, Ivanovo, 153045 Russia
*е-mail: svvr@isc-ras.ru
Received July 2, 2020; revised July 2, 2020; accepted July 19, 2020
Abstract—The metal exchange reactions of Cd(II) 5,10,15,20-tetra(4-chlorophenyl)porphyrinate with CuCl2 and
ZnCl2 in DMSO were studied by the spectrophotometric method. The kinetic parameters of the metal exchange
reactions were determined.Apossible reaction mechanism was proposed. Zinc(II) and copper(II) 5,10,15,20-tetra-
(4-chlorophenyl)porphyrinates were synthesized by the complex formation reactions of zinc(II) and copper(II)
acetates with 5,10,15,20-tetra(4-chlorophenyl)porphyrin and by metal exchange of its cadmium complex with
ZnCl2 and CuCl2 in dimethylformamide. The resulting compounds were identified by electronic absorption and
1H NMR spectroscopy and mass spectrometry methods.
Keywords: Cd(II), Zn(II), Cu(II) 5,10,15,20-tetra(4-chlorophenyl)porphyrinates, complexation, metal exchange
reaction, spectral characteristics
DOI: 10.1134/S1070363220110134
The metal exchange reaction is one of the complex
associative-dissociative chemical reactions of the
exchange by metal ions or ligands, which proceeds
according to Eq. (1).
porphyrinates in DMF are faster than in DMSO [6, 7].
As the solvating capacity of the solvent increases, the
strength of the solvate shell of the salt usually increases,
preventing metal exchange.
In order to identify the regularities of the metal
exchange reaction, we have studied the remetallization
of Cd(II) 5,10,15,20-tetra(4-chlorophenyl)porphyrinate
[CdP(PhCl)4] with CuCl2 and ZnCl2 in DMSO (Scheme 1).
MР + MʹXn(Solv)m–n → MʹР + MXn(Solv)m–n
.
(1)
Here МP and MʹP – are metalporphyrins, MʹXn(Solv)m–n
and MXn(Solv)m–n are metal solvatocomplexes.
For the first time, metal exchange reactions were
carried out by the Linstead research group [1]. The
widespread use of the exchange of some metals for other
metals in the composition of porphyrins is described in
the monograph [2]. An important condition for metal
exchange is the presence of significant effective negative
charges on the coordinating nitrogen atoms in the complex
(δ‒) and positive charges (δ+) on the atom of the outgoing
metal ion. They may appear due to out-of-plane vibrations
of the metal ion in the complex, which are favored by a
disruption of the flat structure of the ligand and a decrease
in its aromaticity.
Cadmium(II) 5,10,15,20-tetra(4-chlorophenyl) por-
phyrinate was obtained by heating a dimethylformamide
solution of 5,10,15,20-tetra(4-chlorophenyl)porphyrin to
the boiling point with cadmium(II) acetate (mole ratio 1
: 10). The EAS of (PhCl)4 in DMF contains bands with
maxima of 417, 439, 577, and 622 nm. In the 1H NMR
spectrum of CdP(PhCl)4 in C6D6, the signal of protons
of pyrrole rings at 8.90 ppm, and also of ortho- and
meta-protons of phenyl groups at 7.96 and 7.46 ppm,
respectively, were recorded. In the mass spectrum of
labile cadmium porphyrinate, along with the peak m/z
862.1 corresponding to the molecular ion CdP(PhCl)4,
there is a peak of porphyrin m/z 753.3.
Possible mechanisms of double metal exchange in
metalloporphyrins in organic solvents were discussed in
[3‒5]. The nature of the solvent defines the strength of the
salt solvate, thus metal exchange reactions of cadmium
Cadmium porphyrins are mainly ionic, kinetically
unstable complexes [8], and their remetallization reactions
with Zn2+, Co2+, Ni2+, and Cu2+ salts occur with the
2105

2106
ZVEZDINA et al.
Scheme 1.
formation of stronger compounds [9]. The changes in EAS
during the CdP(PhCl)4 metal exchange reaction with ZnCl2
in DMSO are shown in Fig. 1, and the experimental data
obtained are shown in Tables 1 and 2.
and porphyrin complexes is presented in [2, 9]. It is
assumed that there are two mechanisms of exchange—
associative and dissociative.
Apparently, the reactions of CdP(PhCl)4 metal
exchange with ZnCl2 and CuCl2 in DMSO proceed by a
bimolecular associative mechanism [3, 10, 11]. In the first
bimolecular stage (3), an intermediate binuclear complex
(intermediate) is formed. It can be formed immediately
after the solutions are poured together and then it is easily
determined spectrally, or this stage is inhibited. In the
second slow monomolecular stage (4), the intermediate
dissociates to form final exchange products.
We found that the reaction order with respect to the salt
for the CdP(PhCl)4 metal exchange with СuCl2 and ZnCl2
in DMSO, defined as the slope ratio of the rectilinear
dependence log kef = f(lgсCuCl ) and log kef = f(lgсZnCl2),
2
is equal to one. The rate of CdP(PhCl)4 metal exchange
with CuCl2 and ZnCl2 in DMSO is described by first-
order Eq. (2) for the cadmium complex, as evidenced by
the rectilinear dependence of lg[с0CdP(PhCl) /сCdP(PhCl)4] on
4
the reaction time τ.
(Solv)mMP + MʹX2(Solv)n–2
‒dсCdP(PhCl) /dτ = kv[CdP(PhCl)4][МCl2].
(2)
↔ (Solv)mMPMʹX2(Solv)n–4 + 2 Solv,
(3)
4
Information about a possible mechanism of the
stoichiometric metal exchange reaction in macrocyclic
(Solv)mMP∙MʹX2(Solv)n–4
≠
↔ [(Solv)mM ∙∙∙ P ∙∙∙ MʹX2(Solv)n–4
]
→ МX2(Solv)m + MʹP(Solv)n–4
.
(4)
Stage (4) is observed in the EAS as a change in the
intensity of absorption bands (Fig. 1). In a strongly
coordinating DMSO medium, the intermediate is not
fixed spectrally.
During the experiment, the influence of the salt solvate
nature on the metal exchange rate was established.
Comparison of effective rate constants of the CdP(PhCl)4
metal exchange with ZnCl2 and CuCl2 in DMSO shows
that the metal exchange with CuCl2 is 43 times faster
than with ZnCl2.
Fig. 1. The change in EAS in the course of metal exchange of
CdP(PhCl)4 with ZnCl2 in DMSO, cCdP(PhCl) = 2.0×10–5 M (1)
The rate of metal exchange is determined to a greater
extent by the stability of the exchange complex itself than
4
at the initial time and (2) after 80 min at 328 K.
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METAL EXCHANGE REACTION OF Cd(II)
2107
Table 1. Rates of the Cd2+ exchange for Cu2+ in the complex CdP(PhCl)4 in DMSO [cCdP(PhCl)4= 2.0×10–5 M]
kef×102, s–1
kv, L mol–1 s–1
Еа, kJ/mol
ΔS≠, J mol–1 K–1
3
сCuCl
×
Т, K
10 , M
2
2.00
1.73
1.33
1.07
303
298
293
288
303
298
293
288
303
298
293
288
303
298
293
288
3.20±0.01
2.50±0.01
1.50±0.01
0.85±0.01
3.15±0.01
2.21±0.01
1.40±0.01
0.71±0.01
2.97±0.01
1.67±0.01
1.08±0.01
0.65±0.01
2.29±0.01
1.51±0.01
0.89±0.01
0.50±0.01
16.0
12.5
7.5
65±9
‒87±36
‒35±20
‒50±29
‒50±28
4.3
18.2
12.8
8.1
72±6
73±8
74±5
4.1
22.3
12.6
8.1
4.9
21.4
14.1
8.3
4.6
Table 2. Rates of the Cd2+ exchange for Zn2+ in the complex CdP(PhCl)4 in DMSO [cCdP(PhCl)4= 2.0×10–5 M]
kef×102, s–1
kv, L mol–1 s–1
Еа, kJ/mol
ΔS≠, J mol–1 K–1
3
сZnCl
×
Т, K
10 , M
2
2.00
1.73
1.33
1.07
328
318
298
328
318
298
328
318
298
328
318
298
9.87±0.01
8.22±0.01
5.88±0.01
8.96±0.01
7.5±0.01
5.23±0.01
7.01±0.01
5.96±0.01
4.21±0.01
5.91±0.01
4.95±0.01
3.21±0.01
0.49
0.41
0.29
0.52
0.43
14±5
‒266±20
15±5
14±6
16±7
‒266±20
‒271±19
‒266±21
0.30
0.530.45
0.32
0.55
0.46
0.30
by the coordinating ability of the ligand. This, and also
the greater reactivity of complexes in the metal exchange
reactions compared to the reactivity of porphyrins in the
complex formation reactions, points to the associative
path of metal exchange in cadmium porphyrin complexes.
medium using complex formation and metal exchange
reactions (Scheme 2).
Metal exchange of CdP(PhCl)4 with copper chloride
(mole ratio 1 : 10) in DMF occurs almost instantly at room
temperature. When CdP(PhCl)4 and copper(II) chloride
are dissolved in DMF, the color of the solution changes
from emerald green to red-brown. The EAS of the sample
dissolved in DMF contains bands with λmax = 415, 539,
Comparison of effective metal exchange rate
constants for Cd(II) octa(4-bromophenyl)porphyrinate
CdP(PhBr)8 with СuCl2 and ZnCl2 [7] and for
CdP(PhCl)4 metal exchange with the same salts in
DMSO shows that the CuCl2 metal exchange with
CdP(PhCl)4 in DMSO proceeds ~130 times faster than
with CdP(PhBr)8, and the ZnCl2 metal exchange with
CdP(PhCl)4 proceeds in DMSO ~300 times faster than
with CdP(PhBr)8. This is due to the fact that Cl‒ ions
are stronger electron-acceptors than Br‒ ions.
579nm, whereasthebandsoftheoriginalcomplexatλmax
=
439, 577, 622 nm disappear. Under similar conditions
the metal exchange of CdP(PhCl)4 with zinc(II) chloride
proceeds for 10 min. The color of the dimethylformamide
solution of the reaction mixture turns purple. The EAS
of the zinc complex in DMF contains bands with λmax
=
405, 426, 559, 598 nm. The complexation of Н2P(PhCl)4
with zinc and copper acetates (mole ratio 1 : 10) in boiling
Complexes of Zn(II) and Cu(II) with tetra(4-chloro-
phenyl)porphyrinweresynthesizedinadimethylformamide
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 90 No. 11 2020

2108
ZVEZDINA et al.
Scheme 2.
DMF passes for 60 and 20 s, respectively. A significant
decrease in the metal exchange temperature of labile
cadmium porphyrinate compared to the complexation
temperature can be explained by the absence of the need
to break the N‒H bonds of the macrocycle.
CDCl3, the signals of pyrrole rings appear at 8.95 ppm,
and the signals of phenyl protons Но and Нm—at 8.01
and 7.85 ppm, respectively.
Thus,themetalexchangereactionsofCd(II)5,10,15,20-
tetra(4–chlorophenyl)porphyrinate with CuCl2 and ZnCl2
in DMSO were studied by spectrophotometric method,
and Zn(II) and Cu(II) 5,10,15,20-tetra(4-chlorophenyl)-
porphyrinates were obtained. It was shown that the metal
exchange reaction proceeds under milder conditions
compared to complex formation.
When passing from the cadmium complex to the zinc
and copper complexes, a hypsochromic shift is observed
in EAS in accordance with spectral strength criterion
[12], characterized by strengthening M←N σ-bond (for
all systems), and M→N π-back bonds (for copper). The
mass spectra of zinc and copper porphyrinates show m/z
peaks 815.5 and 813.3 corresponding to the molecular
EXPERIMENTAL
1
Electronic absorption spectra were recorded on a
Cary-100 spectrophotometer (Varian). 1H NMR spectra
ions of the synthesized compounds. In the H NMR
spectrum of the chloro‒substituted zinc complex in
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METAL EXCHANGE REACTION OF Cd(II)
2109
(500 MHz, CDCl3) were taken on a Bruker AV III-
500 device (internal standard-TMS). Mass spectra
were recorded on a Maldi Tof Shimadzu Biotech
Axima Confidence mass spectrometer (matrix—
dihydroxybenzoic acid).
The precipitate was filtered, washed with water, dried,
and chromatographed on aluminum oxides, the eluent—
chloroform. Yield 0.018 g (0.0221 mmol, 85%). EAS
(DMF), λ, nm (log ε): 395 (4.58), 415 (5.54), 539 (4.33),
579 (3.72). Mass-spectrum, m/z (Irel, %): 813.3 (98) [M]+
(calculated for С44Н24Cl4CuN4: 814.1).
5,10,15,20-Tetra-(4-chlorophenyl)porphyrin of
company “Porphychem,” chemically-pure grade
dimethylformamide, chloroform, dichloromethane, and
cadmium acetate, aluminum oxide and DMSO of “Merck”
company were used in the work. CaCl2 and ZnCl2 were
calcined for 4 h at 200°C. Cd(II) 5,10,15,20-tetra(4-
chlorophenyl)porphyrin was synthesized by the Adler
method [13].
b. A mixture of 0.02 g (0.0232 mol) of CdP(PhCl)4
and 0.031 g (0.232 mol) of CuCl2 in 12 mL of DMF was
kept for 5 min at room temperature and processed as in
method a. Yield 0.017 g (0.0209 mmol, 90%).
The metal exchange reactions of complexes of
tetrapyrrole compounds with d-metal salts was studied
by chemical kinetics and spectroscopy methods.
Experimental procedure and processing of experimental
data are presented in [14].
Cd(II) 5,10,15,20-tetra(4-chlorophenyl)por-
phyrinate. Amixture of 0.03 g (0.0399 mmol) of tetra(4-
chlorophenyl)porphyrin and 0.092 g (0.399 mmol) of
Cd(OAc)2 in 20 mL of DMF was heated to the boiling
point. The reaction mixture was cooled and poured into
water. The precipitate was filtered, washed with water,
dried, and re-precipitated from hexane. Yield 0.031 g
(0.0355 mmol, 94%). EAS (DMF), λ, nm (log ε): 417
FUNDING
The work was supported by the Russian Foundation
for basic research (project no. 19-03-00078 A, study of the
complexation reaction of porphyrin ligand with zinc and
copper cations; project no. 1843370001 p-a, study of the metal
exchange reaction of cadmium porphyrinate with copper and
zinc cations). The equipment of the Upper Volga regional center
for physical and chemical research was used.
1
(4.62), 439 (5.47), 577 (4.12), 622 (4.06). H NMR
spectrum (C6D6), δ, ppm: 8.90 s (8H, pyrrole), 7.96 d
(8Но, J = 7.7 Hz), 7.46 d (8Нm, J = 7.6 Hz). Mass
spectrum, m/z (Irel., %): 862.1. (22) [M]+ (calculated for
С44H24CdCl4N4: 862.9).
CONFLICT OF INTEREST
No conflict of interest was declared by the authors.
REFERENCES
Zn(II) 5,10,15,20-tetra(4-chlorophenyl)por-
phyrinate. a. A mixture of 0.02 g (0.0266 mmol) of
tetra(4-chlorophenyl)porphyrin and 0.049 g (0.266 mmol)
of Zn(OAc)2 in 15 mL DMF was boiled for 1 min, then
cooled, water was added, and the product was salted out.
The precipitate was filtered, washed with water, dried,
and chromatographed on aluminum oxide, the eluent-
chloroform. Yield 0.018 g (0.0221 mmol, 83%). EAS
(DMF), λ, nm (log ε): 405 (4.75), 426 (5.64), 559 (4.42),
598 (4.09). 1H NMR spectrum (CDCl3), δ, ppm: 8.95 s
(8H, pyrrole), 8.01 d (8Но, J = 7.7 Hz), 7.85 d (8Нm, J =
7.6 Hz). Mass spectrum, m/z (Irel., %): 815.5 (97) [M]+
(calculated for С44Н24Cl4N4Zn: 815.9).
1. Barrett, P.A., Frye, D.A., and Linstead, R.P., J. Chem.
Soc., 1938, p. 1157.
https://doi.org/10.1039/JR9380001157
2. Hambright, P., Porphyrin Handbook, Smith,K.,Kadish,K.,
and Guillard R., Eds., New York: Academic Press, 2000,
vol. 3.
3. Berezin, B.D., Zvezdina, S.V., and Berezin, M.B., Russ.
J. Gen. Chem., 2013, vol. 83, no. 7, p. 410.
https://doi.org/10.1134/S1070363213070189
4. Berezin, M.B., Zvezdin, S.V., and Berezin, B.D., Russ. J.
Coord. Chem., 2007, vol. 33, no. 7, p. 488.
https://doi.org/10.1134/S1070328407070032
5. Zvezdina, S.V., Berezin, M.B., and Berezin, B.D., Russ.
J. Coord. Chem., 2010, vol. 36, no. 12, p. 913.
https://doi.org/10.1134/S1070328410120080
6. Zvezdina, S.V., Chizhova, N.V., and Mamardash-
vili, N.Zh., Russ. J. Gen. Chem., 2014, vol. 84,
no. 10, p. 989.
b. A mixture of 0.02 g (0.0232 mol) CdP(PhCl)4 and
0.032 g (0.232 mol) of ZnCl2 in 12 mLDMF was kept for
20 min at room temperature and processed as in method a.
Yield 0.017 g (0.0208 mmol, 88%).
Cu(II) 5,10,15,20-tetra(4-chlorophenyl)por-
phyrinate. a. A mixture of 0.02 g (0.0266 mmol) of
tetra(4-chlorophenyl)porphyrin and 0.048 g (0.266 mmol)
of Cu(OAc)2 in 15 mL of DMF was boiled for 20 s, then
cooled, water was added, and the product was salted out.
https://doi.org/10.1134/S1070363214100211
7. Zvezdina, S.V., Chizhova, N.V., and Mamardashvi-
li, N.Z., Russ. J. Phys. Chem. (A), 2017, vol. 91,
no. 3, p. 437.
https://doi.org/10.1134/S0036024417030335
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 90 No. 11 2020

2110
ZVEZDINA et al.
8. Berezin, B.D., Koordinatsionnye soedineniya porfirinov
i ftalotsianina (Coordination Compounds of Porphyrins
and Phthalocyanine), Moscow: Nauka, 1978.
9. Yatsimirskii, K.B and Lampeka, Ya.D., Fizikokhimiya
kompleksov metallov s makrotsiklicheskimi ligandami
(Physicochemistry of Metal Complexes with Macrocyclic
Ligands), Kiev: Naukova Dumka, 1985.
10. Berezin, B.D., Shukhto, O.V., and Berezin, D.B., Russ. J.
Inorg. Chem., 2002, vol. 47, no. 8, p. 187.
11. Berezin, B.D., Rumyantseva, S.V., and Berezin, M.B.,
Russ. J. Coord. Chem., 2004, vol. 30, no. 4, p. 291.
https://doi.org/10.1023/B:RUCO.0000022806.85114.93
12. Berezin, B.D. and Enikolopyan, N.S., Metalloporfiriny
(Metalloporphyrins), Moscow: Nauka, 1988.
13. Adler, A.D., Longo, F.R., Kampas, F., and Kim, J., J. Inorg.
Nucl. Chem., 1970, vol. 32, no. 7, p. 2443.
https://doi.org/10.1016/0022-1902(70)805 35-8
14. Zvezdina, S.V., Kozgova, E.V., Berezin, M.B., and Bere-
zin, B.D., Russ. J. Inorg. Chem., 2007, vol. 52, no. 9,
p. 1430.
https://doi.org/10.1134/S0036023607090197
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