β-Bromo-substituted palladium(II) tetraphenylporphyrins. Synthesis and spectral properties

Article abstract of DOI:10.1134/S1070363217070222

Bromination of (5,10,15,20-tetraphenylporphyrinato)palladium(II) and [5,10,15,20-tetrakis(4-methoxyphenyl)porphyrinato]palladium(II) with N-bromosuccinimide in chloroform–dimethylformamide and chloroform afforded mono-, tetra-, and octabromo derivatives substituted at the pyrrole rings. The products were identified by electronic absorption, ¹H NMR, and mass spectra and elemental analyses.

Full text of DOI:10.1134/S1070363217070222

ISSN 1070-3632, Russian Journal of General Chemistry, 2017, Vol. 87, No. 7, pp. 1580–1583. © Pleiades Publishing, Ltd., 2017.
Original Russian Text © N.V. Chizhova, O.V. Mal’tseva, N.Zh. Mamardashvili, O.I. Koifman, 2017, published in Zhurnal Obshchei Khimii, 2017, Vol. 87,
No. 7, pp. 1188–1191.
β-Bromo-Substituted Palladium(II) Tetraphenylporphyrins.
Synthesis and Spectral Properties
N. V. Chizhovaa*, O. V. Mal’tsevaa, N. Zh. Mamardashvilia, and O. I. Koifmana–c
a Krestov Institute of Solution Chemistry, Russian Academy of Sciences, ul. Akademicheskaya 1, Ivanovo, 153045 Russia
*e-mail: nvc@isc-ras.ru
b Ivanovo State University of Chemistry and Technology, Sheremetevskii pr. 7, Ivanovo, 153000 Russia
c Research Institute of Macroheterocyclic Chemistry, Ivanovo State University of Chemistry and Technology,
Sheremetevskii pr. 7, Ivanovo, 153000 Russia
Received February 15, 2017
Abstract—Bromination of (5,10,15,20-tetraphenylporphyrinato)palladium(II) and [5,10,15,20-tetrakis(4-
methoxyphenyl)porphyrinato]palladium(II) with N-bromosuccinimide in chloroform–dimethylformamide and
chloroform afforded mono-, tetra-, and octabromo derivatives substituted at the pyrrole rings. The products
were identified by electronic absorption, 1H NMR, and mass spectra and elemental analyses.
Keywords: Palladium(II) tetraphenylporphyrins, β-bromo-substituted palladium(II) tetraphenylporphyrins,
metal exchange reactions, bromination, complex formation
DOI: 10.1134/S1070363217070222
Introduction of bromine atoms into porphyrin
molecules gives rise to compounds possessing new
practically useful properties, in particular good
solubility in organic solvents and high stability of their
metal complexes in proton-donor medium. Bromo-
substituted porphyrins attract interest as substrates for
further chemical transformations. It is known that
porphyrins exhibit biological activity and that their
metal complexes show catalytic activity. Of particular
interest are palladium porphyrin complexes that are
used as optical materials, sensors, and molecular
switches [1–4].
Complex 1 reacted with NBS at a molar ratio of
1:2 in chloroform–DMF (10:1) at room temperature
(2.5 h) to give (2-bromo-5,10,15,20-tetraphenylpor-
phyrinato)palladium(II) (3). The electronic absorption
Scheme 1.
R1
R4
R2
R4
R3
Bhyrappa and Krishnan [5] previously synthesized
(2,3,7,8,12,13,17,18-octabromotetraphenylporphyri-
nato)copper(II) by reaction of (5,10,15,20-tetraphenyl-
porphyrinato)copper(II) (1) with molecular bromine in
a mixture of chloroform with carbon tetrachloride. The
complexation of the corresponding porphyrin ligand
with palladium chloride in acetic acid gave octabromo-
substituted palladium(II) complex [5] (Scheme 1).
N
N
N
N
R1
R1
Pd
R3
R4
R3
R4
With the goal of obtaining palladium(II) porphyrins
substituted at the pyrrole rings, in this work we studied
bromination of (5,10,15,20-tetraphenylporphyrinato)
palladium(II) (1) and [5,10,15,20-tetrakis(4-methoxy-
phenyl)porphyrinato)palladium(II) (2) with N-bromo-
succinimide (NBS) in chloroform and in a mixture of
chloroform and dimethylformamide.
R1
1, R1 = R2 = R3 = R4 = H; 2, R1 = MeO, R2 = R3 = R4 = H;
3, R1 = R3 = R4 = H, R2 = Br; 4, R1 = R4 = H, R2 = R3 = Br;
5, R1 = H, R2 = R3 = R4 = Br; 6, R1 = MeO, R2 = Br, R3 =
R4 = H; 7, R1 = MeO, R2 = R3 = Br, R4 = H.
1580

β-BROMO-SUBSTITUTED PALLADIUM(II) TETRAPHENYLPORPHYRINS
spectrum of 3 in chloroform displayed bands with their
1581
А
maxima at λ 559, 526, and 419 nm, whereas absorption
bands at λmax 555, 523, and 416 nm typical of initial
complex 1 disappeared. The mass spectrum of 3
contained the molecular ion peak with m/z 797 (cal-
culated for C44H27N4BrPd: 798). Figure 1 shows the
electronic absorption spectrum of 3 in DMF (λmax 560,
525, 418 nm).
The reaction of 1 with 6 equiv of NBS in 3 h (other
conditions being the same as above) afforded a mixture
of brominated palladium(II) tetraphenylporphyrins
containing four to five bromine atoms in the pyrrole
rings. Bhyrappa et al. [6] described bromination of
tetraphenylporphyrin with NBS at a molar ratio of 1:6
in boiling chloroform. The bromination of 1 with NBS
(1:20) under analogous conditions in 2 h afforded
(2,3,12,13-tetrabromo-5,10,15,20-tetraphenylporphyri-
nato)palladium(II) (4) (Fig. 1) which showed in the 1H
NMR spectrum one signal at δ 8.51 ppm from protons
in the pyrrole rings and signals in the region δ 8.04–
7.72 ppm due to protons of the phenyl rings. Com-
pound 4 was also formed when a solution of 2,3,12,13-
tetrabromo-5,10,15,20-tetraphenylporphyrin and PdCl2
at a molar ratio of 1:3 in dimethylformamide was
heated to the boiling point.
λ, nm
Fig. 1. Electronic absorption spectra of palladium(II) por-
phyrins (1) 3, (2) 4, and (3) 5 in DMF.
obtained by reaction of 2 with 5 equiv of NBS in
chloroform–DMF at room temperature in 1 h or in
boiling chloroform in 20 min. The electronic absorp-
tion spectra of 6 and 7 are shown in Fig. 2.
Complex 2 reacted with NBS at a molar ratio of
1:12 in chloroform–DMF at room temperature to
produce in 3 h a compound which displayed absorp-
tion bands at λmax 604, 561, and 460 nm in the elec-
tronic spectrum (chloroform solution). The complex
isolated from the reaction mixture partially decom-
posed, and appreciable changes were observed in the
electronic absorption spectrum recorded from a
solution in chloroform. In particular, the I and II bands
shifted blue by ~3–6 nm, and the Soret band was split
The reaction of 1 with 20 equiv of NBS in
chloroform–DMF (10:1) at room temperature (5 h)
afforded (2,3,7,8,12,13,17,18-octabromo-5,10,15,20-
tetraphenylporphyrinato)palladium(II)
(5).
The
electronic absorption spectrum of 5 in DMF contained
1
bands at λmax 594, 558, and 451 nm (Fig. 1). Its H
NMR spectrum lacked signals assignable to protons of
the pyrrole rings, and signals of protons of the phenyl
rings appeared in a stronger field relative to those of
unsubstituted compound 1 and in a weaker field
relative to those of tetrabromo derivative 4. The
Electronic absorption spectra of palladium(II) tetraphenyl-
porphyrins 1–7 in chloroform
λmax, nm (log ε)
Comp.
1
no.
electronic absorption and H NMR spectra of complex
I
II
Soret
5 fully coincided with the corresponding spectral
parameters of the same compound described in [5] (see
table).
1
2
3
4
5а
5
6
7
555 sh
558 sh
559 sh
572 sh
589 sh
591 sh
561 sh
573 sh
523 (4.53) 416 (5.63)
525 (4.44) 419 (5.43)
Introduction of electron-donating methoxy groups
into the para positions of the meso-phenyl groups
facilitated bromination of the macrocycle with N-
bromosuccinimide. The reaction of methoxy-substi-
tuted complex 2 with 2 equiv of NBS gave [2-bromo-
5,10,15,20-tetrakis(4-methoxyphenyl)porphyrinato]-
palladium(II) (6) in 20 min. When the ratio 2 : NBS
was reduced to 1:1.2, compound 6 was formed in
30 min. [2,3,12,13-Tetrabromo-5,10,15,20-tetrakis(4-
methoxyphenyl)porphyrinato]palladium(II) (7) was
526 (4.42) 419 (5.41), 310 (4.31)
536 (4.33) 428 (5.24), 332 (4.27)
556 (4.36) 449 (5.30), 355 (4.46)
556 (4.45) 450 (5.34), 356 (4.52)
528 (4.48) 422 (5.45), 311 (4.27)
537 (4.37) 431 (5.30), 334 (4.24)
a
In methylene chloride [5].
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 87 No. 7 2017

1582
CHIZHOVA et al.
spectra (MALDI TOF) were recorded on a Shimadzu
А
Biotech Axima Confidence mass spectrometer using
1
2,5-dihydroxybenzoic acid as matrix. The H NMR
spectra were measured on a Bruker AV III-500
instrument at 500 MHz using CDCl3 as solvent and
tetramethylsilane as internal standard. The elemental
analyses were obtained on a Thermo Scientific Flash
EA 1112 analyzer.
5,10,15,20-Tetraphenylporphyrin, 5,10,15,20-tetra-
kis(4-methoxyphenyl)porphyrin (Porphychem), N-bromo-
succinimide, PdCl2 (Acros), and aluminum oxide
(Merck) were commercial products; chloroform, DMF,
hexane, and pyridine were of chemically pure grade.
2,3,12,13-Tetrabromo-5,10,15,20-tetraphenylporphyrin
was synthesized as described in [6]. (5,10,15,20-
Tetraphenylporphyrinato)cadmium(II) was synthesized
according to Adler [7]. (5,10,15,20-Tetraphenyl-
porphyrinato)palladium(II) was synthesized according
to the procedure described for transmetalation of labile
porphyrin complexes [8].
λ, nm
Fig. 2. Electronic absorption spectra of metal porphyrins
(1) 6 and (2) 7 in DMF.
into two bands with their maxima at λ 457 and 440 nm
with approximately equal intensities. The electronic
spectrum of a sample withdrawn from the reaction
mixture and dissolved in DMF did not change over a
long time (λmax 606, 564, 463 nm). After isolation from
the DMF solution, a mixture of brominated palladium
porphyrins was formed, which showed absorption bands
at λmax 558, 460, and 438 nm in the electronic spectrum.
(5,10,15,20-Tetraphenylporphyrinato)palladium(II)
(1). A mixture of 0.05 g of (5,10,15,20-tetraphenyl-
porphyrinato)cadmium(II) and 0.037 g of palladium(II)
chloride at a molar ratio of 1:3 was dissolved in 20 mL
of DMF, and the solution was refluxed for 2 min. The
mixture was cooled and poured into water, and the
precipitate was filtered off, washed with water, dried,
and purified by alumina chromatography using
chloroform as eluent. Yield 0.04 g (0.0556 mmol,
The bromination of 2 with excess NBS in boiling
chloroform for 1 h gave a product characterized by
absorption bands at λmax 596, 557, and 454 nm. The
product partially decomposed upon isolation from the
reaction mixture to form a mixture of bromo-sub-
stituted palladium porphyrins.
1
81%). H NMR spectrum, δ, ppm: 8.84 s (8H, β-
pyrrole), 8.20 d (8H, o-H, J = 7.70 Hz), 7.81–7.76 m
(12H, m-H, p-H). Mass spectrum: m/z 718 (Irel 87%)
[M – H]+; calculated for C44H28N4Pd: 719.
In summary, by bromination of palladium(II) tetra-
phenylporphyrins 1 and 2 with N-bromosuccinimide in
a mixture of chloroform and DMF under mild condi-
tions we obtained the corresponding mono- and octa-
bromo derivatives. Exhaustive bromination of [5,10,15,20-
tetrakis(4-methoxyphenyl)porphyrinato]palladium(II)
gave a product which is stable in DMF solution, but it
was converted into a mixture of bromo-substituted
palladium(II) porphyrins during isolation from the
reaction mixture. The bromination of 1 and 2 with
NBS in boiling chloroform afforded the correspond-
ing tetrabromo derivatives. The isolated compounds
[5,10,15,20-Tetrakis(4-methoxyphenyl)porphyri-
nato]palladium(II) (2). A mixture of 0.05 g of
5,10,15,20-tetrakis(4-methoxyphenyl)porphyrin and
0.036 g of palladium(II) chloride at a molar ratio of
1:3 was dissolved in 30 mL of DMF. The solution was
refluxed for 20 s and was then treated as described
above for complex 1. Yield 0.041 g (0.049 mmol,
1
72%). H NMR spectrum, δ, ppm: 8.86 s (8H, β-
pyrrole), 8.10 d (8H, o-H, J = 7.70 Hz), 7.30 d (8H, m-
H, J = 7.60 Hz), 4.11 s (12H, OCH3). Found, %: C
68.84; H 4.27; N 6.63. C48H36N4O4Pd. Calculated, %:
C 68.87; H 4.32; N 6.68.
1
were characterized by electronic absorption, H NMR,
and MALDI TOF mass spectra and elemental analyses.
(2-Bromo-5,10,15,20-tetraphenylporphyrinato)-
palladium(II) (3). N-Bromosuccinimide, 0.01 g
(0.0557 mmol), was added with stirring to a solution of
0.02 g (0.0278 mmol) of complex 1 in a mixture of
EXPERIMENTAL
The electronic absorption spectra were recorded on
a Varian Cary-100 spectrophotometer. The mass
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 87 No. 7 2017

β-BROMO-SUBSTITUTED PALLADIUM(II) TETRAPHENYLPORPHYRINS
1583
10 mL of chloroform and 1 mL of DMF. The mixture
was stirred for 2.5 h at room temperature, 0.1 mL of
pyridine and water were added, and the organic phase
was separated, washed with water, dried over Na2SO4,
and evaporated to a minimum volume. The residue was
purified by alumina chromatography (eluent chloro-
form), followed by reprecipitation from ethanol. Yield
[2-Bromo-5,10,15,20-tetrakis(4-methoxyphenyl)-
porphyrinato]palladium(II)(6) was synthesized from
0.02 g (0.0238 mmol) of complex 2 and 0.0051 g
(0.0286 mmol) of NBS; reaction time 30 min. Yield
1
0.018 g (0.0196 mmol, 82%). H NMR spectrum, δ,
ppm: 8.97–8.94 m (2H), 8.88 s (1H), 8.82–8.79 m
(2H), and 8.77–8.75 m (2H) (β-pyrrole); 8.10–8.05 m
(6H) and 8.04–8.01 m (2H) (o-H), 7.92–7.88 m (8H,
m-H), 4.10 s (12H, OCH3). Mass spectrum: m/z 917
(Irel 72%) [M – H]+; calculated for C48H35N4Br4O4Pd:
918.
1
0.017 g (0.0215 mmol, 78%). H NMR spectrum, δ,
ppm: 8.97–8.95 m (2H), 8.81 s (1H), 8.80–8.77 m
(2H), and 8.74–8.72 m (2H) (β-pyrrole); 8.18–8.15 m
(6H) and 8.03–7.99 m (2H) (o-H), 7.76–7.68 m (12H,
m-H, p-H). Mass spectrum: m/z 797 (Irel 69%) [M – H]+;
calculated for C44H27N4BrPd: 798.
[2,3,12,13-Tetrabromo-5,10,15,20-tetrakis(4-me-
thoxyphenyl)porphyrinato]palladium(II) (7) was
synthesized as described above for complex 4 (method
a) from 0.02 g (0.0238 mmol) of complex 2 and 0.022 g
(0.119 mmol) of NBS; reaction time 20 min. Yield
(2,3,12,13-Tetrabromo-5,10,15,20-tetraphenylpor-
phyrinato)palladium(II) (4). a. N-Bromosuccinimide,
0.025 g (0.139 mmol), was added in four portions with
stirring to a solution of 0.02 g (0.0278 mmol) of
complex 1 in 10 mL of chloroform. The mixture was
refluxed for 30 min and cooled, 0.2 mL of pyridine and
water were added, and the organic phase was
separated, washed with water, dried over Na2SO4, and
evaporated. The residue was purified by alumina
chromatography using first chloroform–hexane (1:2)
and then chloroform as eluent, followed by repre-
cipitation from ethanol. Yield 0.018 g (0.0174 mmol,
1
0.02 g (0.0173 mmol, 73%). H NMR spectrum, δ,
ppm: 8.84 s (8H, β-pyrrole), 7.95 d (8H, o-H, J =
7.70 Hz), 7.88 d (8H, m-H, J = 7.60 Hz), 4.08 s (12H,
OCH3). Mass spectrum: m/z 1154 (Irel 67%) [M – H]+;
calculated for C48H32N4Br4O4Pd: 1155.
ACKNOWLEDGMENTS
This study was performed under financial support
by the Russian Science Foundation (project no. 14-23-
00204-P).
1
63%). H NMR spectrum, δ, ppm: 8.51 s (8H, β-
pyrrole), 8.04 d (8H, o-H, J = 7.70 Hz), 7.77–7.72 m
(12H, m-H, p-H). Mass spectrum: m/z 1033 (Irel 72%)
[M – H]+; calculated for C44H24N4Br4Pd: 1034.
REFERENCES
1. Porfiriny: spektroskopiya, elektrokhimiya, primenenie
(Porphyrins: Spectroscopy, Electrochemistry, and
Applications), Enikolopyan, N.S., Ed., Moscow: Nauka,
1987.
2. Lebedev, A.Y., Filatov, M.A., Cheprakov, A.V., and
Vinogradov, S.A., J. Phys. Chem. A, 2008, vol. 112,
p. 7723. doi 10.1021/jp8043626
b. A mixture of 0.02 g (0.0215 mmol) of 2,3,12,13-
tetrabromo-5,10,15,20-tetraphenylporphyrin and 0.011 g
(0.0644 mmol) of palladium(II) chloride was dissolved
in 8 mL of DMF, and the solution was heated to the
boiling point over a period of 1 min, cooled, and
poured into water. The precipitate was filtered off,
washed with water, dried, and purified by alumina chro-
matography (chloroform). Yield 0.019 g (0.0184 mmol,
86%).
3. Lupton, J.M., Appl. Phys. Lett., 2002, vol. 81, no. 13,
p. 2478. doi 10.1063/1.1509115
4. Borovkov, V.V., Mamardashvili, N.Zh., and Inoue, Y.,
Russ. Chem. Rev., 2006, vol. 75, no. 8, p. 737. doi
10.1070/RC2006v075n08ABEH003630
Compounds 5 and 6 were synthesized as described
above for complex 3.
5. Bhyrappa, P. and Krishnan, V.J., Inorg. Chem., 1991,
vol. 30, p. 239. doi 1021/ic00002a018
(2,3,7,8,12,13,17,17,18-Octabromo-5,10,15,20-
tetraphenylporphyrinato)palladium(II) (5) was syn-
thesized from 0.02 g (0.0278 mmol) of complex 1 and
0.1 g (0.556 mmol) of NBS; reaction time 5 h. Yield
0.027 g (0.02 mmol, 72%). 1H NMR spectrum, δ, ppm:
8.07 d (8H, o-H, J = 7.70 Hz), 7.79–7.75 m (12H,
m-H, p-H). Mass spectrum, m/z 1349 (Irel 69%) [M –
H]+; calculated for C44H20N4Br8Pd: 1350.
6. Kumar, P.K., Bhyrappa, P., and Varghese, B., Tetrahedron
Lett., 2003, vol. 44, p. 4849. doi 10.1016/S004039(03)
01143-2
7. Adler, A.D., Longo, F.R., Kampas, F., and Kim, J., J. Inorg.
Nucl. Chem., 1970, vol. 32, p. 2443. doi 10.1016/0022-
1902(70)80535-8
8. Hambright, P., Coord. Chem. Rev., 1971, vol. 6, p. 247.
doi 10.1016/S0010-8545(00)80041-7
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