Synthesis and properties of bromine-substituted Co(II) tetraphenylporphyrinates

Article abstract of DOI:10.1134/S1070363216050182

The interaction of bromine-substituted tetraphenylporphyrins with cobalt(II) acetate in a chloroform–methanol mixture yielding the corresponding cobalt(II) porphyrinates has been studied by means of spectrophotometry. Treatment of Co(II) porphyrinates wit

Full text of DOI:10.1134/S1070363216050182

ISSN 1070-3632, Russian Journal of General Chemistry, 2016, Vol. 86, No. 5, pp. 1091–1094. © Pleiades Publishing, Ltd., 2016.
Original Russian Text © N.V. Chizhova, S.V. Zvezdina, N.Zh. Mamardashvili, 2016, published in Zhurnal Obshchei Khimii, 2016, Vol. 86, No. 5, pp. 829–
832.
Synthesis and Properties
of Bromine-Substituted Co(II) Tetraphenylporphyrinates
N. V. Chizhova, S. V. Zvezdina, and N. Zh. Mamardashvili
Krestov Institute of Solutions Chemistry, Russian Academy of Sciences, ul. Akademicheskaya 1, Ivanovo, 153045 Russia
e-mail: nvc@isc-ras.ru
Received June 26, 2015
Abstract—The interaction of bromine-substituted tetraphenylporphyrins with cobalt(II) acetate in a
chloroform–methanol mixture yielding the corresponding cobalt(II) porphyrinates has been studied by means
of spectrophotometry. Treatment of Co(II) porphyrinates with bromine in the same medium has afforded the
Co(III) porphyrinates.
Keywords: bromine-substitutes tetraphenylporphyrin, complex formation, cobalt tetraphenylporphyrinate,
visible-range spectroscopy
DOI: 10.1134/S1070363216050182
The interest to synthesis and studies of transition
metals porphyrinates is owing to the possibilities of
their application as chemical sensors, photochromic
materials, and redox reactions catalysts.
methanol occurred within 1.5 h to afford the corres-
ponding porphyrinate 4. The electronic absorption
spectrum of a specimen samples from the reaction
mixture after the reaction completion contained the
bands at λmax 529 and 411 nm, whereas the bands of
the starting compound 1 (646, 590, 550, 515, and
418 nm) were absent (see the figure).
Synthesis of Со(II) and Со(III) complexes with
tetraphenylporphyrin has been described in [1–3].
Electrochemical oxidation and reduction of Co(II)
complexes with β-brominated tetraphenylporphyri-
nates has been described [4, 5].
Со(II)
porphyrinates
exhibit
paramagnetic
1
properties. Н NMR spectrum of complex 4 contained
the broadened signals of β-protons and phenyl rings at
15.87, 12.96, and 10.08 ppm, whereas the signals of
the starting compound 1 at 8.85, 8.08, 7.92, and
–2.88 ppm were absent.
Aiming to prepare Со(II) and Со(III) complexes
with para- and β-brominated tetraphenylporphyrins
and elucidate the influence of bromine on the
coordination properties of porphyrins, in this work we
studied the coordination reactions of 5,10,15,20-tetra-
(4-bromophenyl)porphyrin 1, 2,3,12,13-tetrabromo-
5,10,15,20-tetraphenylporphyrin 2, and 2,3,7,8,12,-
13,17,18-octabromo-5,10,15,20-tetraphenylporphyrin
3 with cobalt(II) acetate in a chloroform–methanol
mixture by means of spectrophotometry.
The reaction of formation of cobalt(II) porphy-
rinates was faster in the cases of the β-brominated
porphyrins 2 and 3. For instance, the tetrabrominated
Co(II) porphyrinate was formed upon refluxing of the
starting compounds in a chloroform–methanol mixture
in the course of 40 min, whereas the octabrominated
Co(II) porphyrinate was formed upon incubation of the
reaction mixture at 20°С during 10 min.
The significant differences in the electronic absorp-
1
tion and Н NMR spectra of the starting porphyrins
According to the available data [6], electron-
donating substituents increase the electronic density on
the tertiary nitrogen atoms of the macrocycle, thus
enhancing the coordination interaction of the solvated
cationic complex [MX2(Solv)n–2] with porphyrin in the
transition state. In the cases of the β-brominated
porphyrins 2 and 3, the coordination with Со(ОАс)2
and the formed Co(II) complexes (Table 1) allowed for
the study of the complexes formation of porphyrins 1–
3 and identification of porphyrinates 4–6 using those
spectral methods.
Complex formation of porphyrin 1 with cobalt(II)
acetate in a boiling mixture of chloroform and
1091

1092
CHIZHOVA et al.
Scheme 1.
R1
R1
R3
R2
R3
R2
R2
R3
R2
R3
R3
R2
R3
R2
NH
N
N
N
N
N
N
R1
R1
R1
R1
M
HN
R3
R3
R2
R2
R1
1−3
R1
4−9
R1 = Br, R2 = R3 = H (1, 4, 7); R1 = H, R2 = Br, R3 = H (2, 5, 8); R1 = H, R2 = R3 = Br (3, 6, 9); M = Co(II) (4–6),
Co(III)(OH)·CH3OH (7–9).
was significantly affected by the spatial structure of the
macrocycle [7, 13] (Scheme 1).
Redox potential ECo2+ 3+ of the central ion is low
/Co
for cobalt porphyrinates [8, 9]. The value of the
potential is largely determined by the donor-acceptor
properties of the tetrapyrrole ligands. Electron-
donating substituents in the tetrapyrrole macrocycle
favor the anodic shift of the redox potential and
stabilize the cobalt(III) complexes, and the effect of
the electron-accepting substituents is the opposite
[9, 10].
X-ray diffraction data for Zn(II) complex of
porphyrin 2 have been given in Ref. [13]. It has been
demonstrated that the Zn(II) porphyrinate existed in
the saddle conformation. The four bromine atoms in
the molecule of porphyrin 2 are located in the same
plane [7]. In the case of the octabrominated porphyrin
3, the phenyl fragments are located in the same plane,
the macrocycle exhibiting the saddle conformation.
Bromine atoms of the two adjacent pyrrole rings of
compound 3 are located above the corresponding
planes by 0.170–0.461 Å, and bromine atoms of the
two other rings are located below their planes.
The experiments performed in this study revealed
that treatment of cobalt(II) porphyrinate 4 with
bromine in a chloroform–methanol mixture afforded
1
the cobalt(III) porphyrinate 7. Н NMR spectrum of
diamagnetic porphyrinate 7 contained the signals at
Table 1. Parameters of electronic absorption spectra of porphyrins 1–3 in CH2Cl2 [λ, nm (log ε)]
Compound
Band I
Band II
Bands III and IV
Soret band
417 (5.77)
Reference
This work
1
646 (4.05)
590 (4.15)
550 (4.25)
515 (4.51)
533 (4.30)
533 (4.31)
569 (3.96)
2
3
685 (4.02)
683 (4.06)
743 (3.87)
612 (3.58)
612 (3.70)
626 (4.12)
436 (5.52)
436 (5.46)
469 (5.31)
370 (4.52)
469 (5.29)
369 (4.48)
[13]
This work
[5]
741 (3.85)
625 (4.11)
569 (3.95)
This work
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 86 No. 5 2016

SYNTHESIS AND PROPERTIES OF BROMINE-SUBSTITUTED Co(II)
9.07–7.92 ppm, and the downfield signals of Со(II)
1093
A
porphyrinate were absent.
The Со(II)→Co(III) oxidation of porphyrinates
resulted in red shift of the bands in the electronic
absorption spectrum (Table 2 and the figure).
Solid compound 7 was stable during several days.
Similarly to the earlier described case of the Pt(II)→
Pt(IV) tetraphenylporphyrinates oxidation with
bromine in chloroform [11], the macrocycle was not
brominated under the reaction conditions. That was
confirmed by the visible spectroscopy data: reduction
of complex 7 on alumina gave the product identical to
the Co(II) porphyrinate 4 (Table 2).
λ, nm
Electronic absorption spectra of compounds (1) 4 and (2) 7
in chloroform.
The β-octabrominated Со(III) porphyrinate prepared
under similar conditions was reduced into the Co(II)
complex upon the solvent removal. The electronic
absorption spectrum of the compound isolated from
the reaction mixture and dissolved in chloroform
contained the bands at λmax 563, 447, and 358 nm,
chloroform (“chemical pure” grade) were used.
Compounds 2 and 3 were synthesized via the methods
adopted from [5, 13]. Cobalt(II) acetate (“chemical
pure” grade) was recrystallized from glacial acetic acid
and dried at 80°С during 1 h. Bromine was purified as
described in Ref. [14].
1
typical of Co(II) porphyrinate 6. Н NMR spectrum of
the obtained compound contained the broadened weak-
field signals of ortho-, meta-, and para-protons at
15.32 and 10.16–10.10 ppm. The data coincided with
the relevant information for paramagnetic Co(II)
porphyrinates (3d7 configuration) [12].
Complex formation of the porphyrins with
Со(ОАс)2 was monitored by means of spectro-
photometry. Electronic absorption spectra were re-
corded using a Cary-100 spectrophotometer at room
temperature. 1Н NMR spectra (500 MHz, CDCl3) were
recorded using a Bruker AV III-500 instrument with
TMS as the internal reference. Mass spectra (MALDI
TOF) were registered using a Shimadzu Biotech
Axima Confidence mass spectrometer with methanol
as solvent.
Treatment of cobalt(II) porphyrinate 5 with bromine
in a chloroform–methanol mixture gave rise to a
mixture of Co(II) and Co(III) complexes. The elec-
tronic absorption spectrum in chloroform contained the
bands at λmax 582, 547, and 427 nm, typical of the both
porphyrinates.
Cobalt(II) 5,10,15,20-tetra-(4-bromophenyl)por-
phyrinate (4). 0.038 g (0.215 mmol) of Со(ОАс)2
In summary, the interaction of brominated por-
phyrins with cobalt(II) acetate in a chloroform–
methanol mixture resulted in the formation of the
corresponding Co(II) porphyrinates. Bromine subst-
ituents in the pyrrole rings of the macrocycle sig-
nificantly affected the formation of the Co(II) por-
phyrinates. In particular, the para-bromination of the
benzene rings did not accelerate the reaction, whereas
the β-bromination accelerated the formation and
stabilized the Co(II) porphyrins. Formation of the
stable Co(III) porphyrinates likely requires the severe
conditions (strong oxidizer, elevated temperature, and
prolonged reaction).
Table 2. Parameters of electronic absorption spectra of
porphyrinates 4–9 in chloroform [λ, nm (log ε)]
Compound
Band I
Band II
Soret band
4
5
6
528 (4.50)
582 (3.94)
563 (4.26)
411 (5.57)
427 (5.08)
547 (4.05)
447 (5.22),
358 (4.46)
7
589 (4.26)
549 (4.56)
431 (5.41)
8а
9а
608 [0.117] 568 [0.178] 445 [1.14]
EXPERIMENTAL
628 [0.19] 583 [0.28] 464 [1.66]
a
Commercially available porphyrin 1 (Porphychem),
methanol (Fisher Chemical), dichloromethane and
The relative intensities in the presence of Br2 and CH3OH are
reported.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 86 No. 5 2016

1094
CHIZHOVA et al.
dissolved in 10 mL of methanol was added to a
solution of 0.02 g (0.0215 mmol) of porphyrin 1 in
15 mL of chloroform. The reaction mixture was
refluxed during 1.5 h and then cooled; distilled water
was added to the mixture; the organic layer was
separated off, washed with water, dried over Na2SO4,
and evaporated. The residue was subject to chromato-
graphy on alumina with chloroform and then repre-
cipitated from methanol. Yield 0.013 g (0.013 mmol,
of Upper-Volga Regional Center for Physico-Chemical
Studies.
REFERENCES
1. Shirazi, A. and Goff, H.M., Inorg. Chem., 1982, vol. 21,
p. 3420. DOI: 10.1021/ic00139a030.
2. Shunichi, F., Hironori, K., Tomoyoshi, S., and Seiji, O.,
Chem. Commun., 2002, vol. 17, p. 1984. DOI: 10.1039/
B205517A.
1
62%). H NMR spectrum, δ, ppm: 15.87 br.s. (8Н,
pyrrole), 12.96 br.s (8Н, Нo), 10.08 br.s (8Н, Нm).
Mass spectrum, m/z (Irel, %): 986 (70) [M – H]+.
3. Scherson, D., Tanaka, A.A., Gupta, S.L., Tryk, D.,
Fierro, C., Holze, R., Yeager, E.B., and Lattimer, R.P.,
Electrochim. Acta, 1986, vol. 31, p. 1247. DOI:
10.1016/0013- 4686(86)80144-X.
Compounds 5 and 6 were prepared similarly
4. D’Souza, F., Villard, A., Caemelbecke, E.V., Franzen, M.,
Boschi, T., Tagliatesta, P., and Kadish, K.M., Inorg.
Chem., 1993, vol. 32, p. 4042. DOI: 10.1021/ic00071a012.
Cobalt(II) 2,3,12,13-tetrabromo-5,10,15,20-tetra-
phenylporphyrinate Со(II) (5). Yield 0.014 g
(0.014 mmol, 67%). 1H NMR spectrum, δ, ppm: 15.65
br.s (4Н, pyrrole), 13.25 br.s (8Н, Нo), 9.75 br.s (8Н,
Нm), 9.10 br.s (4Н, Нp). Mass spectrum, m/z (Irel, %):
986 (31) [M – H]+.
5. Bhyrappa, P. and Krishnan, V., Inorg. Chem., 1991,
vol. 30, p. 239. DOI: 10.1021/ic00002a018.
6. Berezin, B.D., Koordinatsionnye soedineniya porfirinov
i ftalotsianina (Coordination Compounds of Porphyrin
and Phthalocyanine), Moscow: Nauka, 1978.
Cobalt(II) 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-
tetraphenylporphyrinate Со(II) (6). Yield 0.018 g
7. Maltseva, O.V., Chizhova, N.V., and Mamardashvili, N.Zh.,
Russ. J. Gen. Chem., 2012, vol. 82, no. 7, p. 1278. DOI:
10.1134/S107036321207016X.
1
(0.0138 mmol, 85%). H NMR spectrum, δ, ppm:
15.32 br.s (8Н, Нo), 10.16–10.10 m (8Н, Нm,p). Mass
spectrum, m/z (Irel, %): 1302 (51) [M – H]+.
8. Mann, C.K. and Barnes, K.K., Electrochemical Reac-
tions in Nonaqueous Systems, New York: Marcel
Dekker, 1970.
Со(III)(OH)·CH3OH 5,10,15,20-tetra-(4-bromo-
phenyl)porphyrinate (7). 0.3 mL of methanol and
0.4 mL of bromine (10 drops of bromine per 10 mL of
chloroform) were added to a solution of 0.02 g
(0.0203 mmol) of complex 4 in 15 mL of chloroform.
The reaction mixture was incubated at room
temperature at stirring during 10 min, poured in a Petri
dish, and evaporated. The residue was recrystallized
from methanol. Yield 0.018 g (0.0164 mmol, 82%). 1H
NMR spectrum, δ, ppm: 9.07 s and 8.84 s (8Н,
pyrrole), 8.10 d (8Н, Нo, J = 7.70 Hz), 7.92 d (8Н, Нm,
J = 7.60 Hz). Mass spectrum, m/z (Irel, %): 1034 (72)
[M – H]+.
9. Porfiriny: Spektroskopiya, elektrokhimiya, primenenie
(Porphyrins: Spectroscopy, Electrochemistry, Applica-
tion), Enikolopyan, N.S., Ed., Moscow: Nauka, 1987.
10. Uspekhi khimii porfirinov (Advances in Porphyrin
Chemistry), Golubchikov, O.A., St. Petersburg: NII
Khimii S.-Peterburg. Gos. Univ., 1999, vol. 2, p. 190.
11. Chizhova, N.V., Kulikova, O.M., and Mamardashvili, N.Zh.,
Russ. J. Gen. Chem., 2013, vol. 83, no. 11, p. 2108.
DOI: 10.1134/S107036321311025X.
12. Ali, B.B., Belkhiria, M.S., Giorgi, M., and Nasri, H.,
Open J. Inorg. Chem., 2011, vol. 1, p. 39. DOI:
10.4236/ojic.2011.13006.
13. Kumar, P.K., Bhyrappa, P., and Varghese, B.,
Tetrahedron Lett., 2003, vol. 44, p. 4849. DOI: 10.1016/
S004039(03)01143-2.
ACKNOWLEDGMENTS
This work was financially supported by Russian
Foundation for Basic Research (projects 14-03-00011
and 14-03-00009) and performed using the equipment
14. Khelevina, O.G., Chizhova, N.V., and Berezin, B.D.,
Zh. Org. Khim., 1991, vol. 27, no. 4, p. 805.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 86 No. 5 2016