Palladium(II) octaalkylporphyrinates: Synthesis and spectral properties

Article abstract of DOI:10.1134/S003602360809009X

Palladium 3,7,13,17-tetramethyl-2,8,12,18-tetrabutylporphyrinate (I) and its 5,15-diaza (II), diphenyl (III), and di(4-bromophenyl) (IV) derivatives were synthesized by the complex formation reaction of palladium(II) chloride with corresponding tetrapyrro

Full text of DOI:10.1134/S003602360809009X

ISSN 0036-0236, Russian Journal of Inorganic Chemistry, 2008, Vol. 53, No. 9, pp. 1401–1404. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © N.V. Chizhova, O.V. Toldina, N.Zh. Mamardashvili, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 9, pp. 1500–1503.
COORDINATION
COMPOUNDS
Palladium(II) Octaalkylporphyrinates:
Synthesis and Spectral Properties
N. V. Chizhovaa, O. V. Toldinaa, and N. Zh. Mamardashvilib
a Institute of Solution Chemistry, Russian Academy of Sciences, Akademicheskaya 1, Ivanovo, 153045 Russia
b Ivanovo State University of Chemical Technology, pr. F. Engel’sa 7, Ivanovo, 153000 Russia
Received May 21, 2007
Abstract—Palladium 3,7,13,17-tetramethyl-2,8,12,18-tetrabutylporphyrinate (I) and its 5,15-diaza (II), diphe-
nyl (III), and di(4-bromophenyl) (IV) derivatives were synthesized by the complex formation reaction of pal-
ladium(II) chloride with corresponding tetrapyrrole ligands in dimethylformamide, and their spectral properties
were studied.
DOI: 10.1134/S003602360809009X
Porphyrins are widely used in design of new materi-
als, sensors, and molecular measuring devices of vari-
ous nature. Interest in this class of tetrapyrrole com-
pounds is mainly caused by the following factors:
(1) they are chromophores, which can be used as
probes for monitoring the processes in the systems to be
studied; (2) they are macrocycles with unique complex-
ation properties; (3) they are convenient building
blocks, which can be selectively modified to produce
compounds in which required reaction centers are
arranged in certain spatial orientation with respect to
one another [1, 2].
CH3
CH3
X
C4H9
C4H9
C4H9
C4H9
Cl
M
Solv
Solv
Solv
Solv
N
N
N
M
X
Cl
N
(IX)
CH3
CH3
å = Pd, X = ëH (I),
M = Pd, X = N (II),
M = Pd, X = ë–C6H5 (III),
M = Pd, ï = ë–4-BrC6H4 (IV),
å = H2, X = ëH (V),
M = H2, X = N (VI),
The introduction of metals into porphyrins signifi-
cantly changes their spectral characteristics. In particu-
lar, as distinct from initial compounds, Pd(II) com-
plexes with porphyrins begin to phosphoresce even at
room temperature [3]. This makes it possible to use pal-
ladium porphyrinates in molecular electronics (as ele-
mentary cells for storage, transformation, transmission,
and mapping of information [4]) and analytical bio-
chemistry (as labels for luminescent immunoassay in
determination of different biologically active com-
pounds) [5].
M = H , X = ë–C6H5 (VII),
2
M = H2, ï = ë–4-BrC6H4 (VIII),
å = Cu, X = N (XI) [8].
EXPERIMENTAL
Porphyrin ligands V–VIII were synthesized as
described in [6]. The course of the reaction of the metal
cation with the porphyrin ligand was monitored by
spectrophotometry and thin-layer chromatography
(TLC). The electronic absorption spectra were recorded
in chloroform on a Cary-100 spectrophotometer at 298 K.
The electron impact mass spectra were recorded on an
MX-1310 mass spectrometer at an ionizing electron
energy of 70 eV and an ionization chamber temperature
of 150–200°ë. Analysis by the TLC method was carried
out on Silufol (G/UV254) plates, a hexane–chloroform
(1 : 1) mixture was used as the eluent. The IR spectra
were recorded as KBr discs on a Specord M-80 spectro-
photometer in the range 4500–400 cm–1. Solvents were
purified as described in [7].
In this work, with the aim of designing porphyrin-
containing photochromic systems capable of respond-
ing to the external impact, we synthesized palladium
3,7,13,17-tetramethyl-2,8,12,18-tetrabutylporphyri-
nate (I) and its 5,15-diaza (II), diphenyl (III), and di(4-
bromophenyl) (IV) derivatives by the complex forma-
tion reaction of Pd2+ with corresponding tetrapyrrole
ligands in dimethylformamide (DMF) and studied their
spectral properties.
1401

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CHIZHOVA et al.
Synthesis of Pd2+ Porphyrinates
Found (wt %): C, 73.65; N, 6.57; H, 7.11.
MS: m/z = 844.9 (846.3 (calcd.)), Irel = 82%, [M+].
Palladium(II) 3,7,13,17-Tetramethyl-2,8,12,18-
tetrabutylporphyrinate (I). A mixture of 0.05 g (0.085
mmol) of porphyrin V and 0.15 g of PdCl2 (0.85 mmol)
was dissolved in 30 mL of DMF and heated under reflux
for 1 min. The reaction mixture was cooled and diluted
with 50 mL of water. The resulting precipitate was filtered
off, washed with water, dried, and chromatographed on
neutral alumina (elution with hexane–chloroform (1 : 1)).
The yield was 0.031 g (0.045 mmol), 53%. Rf = 0.70.
IR, cm–1: 3186 w, 3051 w, 2959 s, 2927 s, 2867 m,
1734 w, 1670 w, 1634 w, 1553 w, 1452 s, 1388 s,
1372 s, 1309 w, 1264 s, 1235 s, 1153 s, 1106 m, 1058 s,
1015 s, 990 s, 938 w, 832 s, 754 w, 732 m, 716 m,
611 w, 468 w, 451 w, 425 w.
Palladium(II) 3,7,13,17-Tetramethyl-2,8,12,18-
tetrabutyl-5,15-4-dibromophenylporphyrinate (IV).
A mixture of 0.05 g of porphyrin VIII and 0.1 g of
PdCl2 (molar ratio 1 : 10) was heated in 40 mL of DMF
to boiling. The reaction was instantaneous. The reac-
tion mixture was cooled and chromatographed on neu-
tral alumina (elution with hexane–chloroform 1 : 1).
The yield was 0.042 g (0.042 mmol), 76%. Rf = 0.78.
For PdC40N4, anal. calcd. (wt %): C, 69.10; N, 8.06;
H, 7.54.
Found (wt %): C, 69.06; N, 8.02; H, 7.51.
MS: m/z = 693.1 (694.3 (calcd.)), Irel = 71%, [M+].
IR, cm–1: 3057 w, 2923 m, 2851 w, 1809 w, 1634 m,
1565 w, 1543 w, 1472 m, 1429 m, 1352 s, 1314 m,
1237 w, 1210 w, 1159 w, 1073 s, 1036 m, 1014 s,
946 w, 866 w, 833 w, 795 s, 752 s, 724 m, 715 m,
648 m, 459 m, 412 w.
For PdC52H58N4Br2 anal. calcd. (wt %): C, 62.13;
N, 5.57; H, 5.82.
Found (wt %): C, 62.09; N, 5.54; H, 5.78.
MS: m/z = 1003.1 (1004.2 (calcd.)), Irel = 67%, [M+].
IR, cm–1: 2922 w, 2851 w, 1732 w, 1645 w, 1603 w,
1570 m, 1485 s, 1450 w, 1408 s, 1352 s, 1314 m,
1287 w, 1244 m, 1208 w, 1181 m, 1140 w, 1068 s,
945 m, 883 m, 821 s, 795 s, 715 m, 695 m, 569 w, 528 w.
Palladium(II) 3,7,13,17-Tetramethyl-2,8,12,18-
tetrabutyl-5,15-diazaporphyrinate (II). A mixture of
0.05 g of porphyrin VI and 0.15 g of PdCl2 (molar ratio
1 : 10) was heated under reflux in 50 mL of DMF for
3 min. The reaction mixture was cooled and chromato-
graphed on neutral alumina (elution with hexane–chlo-
roform 1 : 1). The yield was 0.014 g (0.019 mmol),
24%. Rf = 0.75.
RESULTS AND DISCUSSION
According to the mechanism of coordination of por-
phyrins by metal cations in solutions, metalloporphy-
rins are formed upon the bimolecular collision of the
porphyrin ligand and solvated salt (IX) [9]. The com-
plex formation rate depends on two factors: (1) the
strength of the N–H bond of the porphyrin reaction cen-
ter and (2) donor–acceptor interaction of the nitrogen
atoms of porphyrin with the metal cation of the salt.
The effect of these factors can vary as a function of spe-
cific conditions of the process.
Our spectrophotometric study of complex formation
of the Pd(II) cation with porphyrin ligands V–VIII in
DMF by the sampling method [10] showed that Pd(II)
porphyrinates are formed faster from porphyrins VII
and VIII than from porphyrin V. It is likely that elec-
tron-donating aryl (aryl = ë6ç5, 4-Brë6ç4) substituents
in the 5- and 15-positions of the porphyrin macrocycle
increase the electron density on the tertiary nitrogen
atoms of the macrocycle and, hence, enhance the coor-
dination interaction of the cation of the solvate complex
with porphyrin in the transition state. As a result, the
reactivity of porphyrins VII and VIII during complex
formation with PdCl2 increases as compared to meso-
unsubstituted porphyrin V.
For PdC38H50N6 anal. calcd. (wt %): C, 65.52; N,
12.07; H, 7.18.
Found (wt %): C, 65.47; N, 12.01; H, 7.13.
MS: m/z = 695.4 (696.3 (calcd.)), Irel = 64%, [M+].
IR, cm–1: 2997 w, 2929 w, 2833 w, 1632 w, 1606 s,
1574 w, 1541 w, 1505 s, 1462 m, 1440 m, 1410 w, 1353 s,
1311 w, 1288 m, 1247 s, 1175 s, 1106 w, 1075 w, 1016
s, 1009 s, 849 w, 811 m, 799 m, 714 m, 640 w, 608 m,
541 m, 438 w, 408 w.
In addition to the major product (porphyrinate II),
the 3 : 2 complex of porphyrinate II with PdCl2 (X) was
isolated from the reaction mixture by column chroma-
tography on neutral alumina (elution with hexane–
chloroform 1 : 2). The yield was 0.005 g (0.002 mmol),
2.4(%. Rf = 0.15.
For Pd5C114H150N18Cl4 anal. calcd. (wt %): C, 56.02;
N, 10.32; H, 6.14.
Found (wt %): C, 55.91; N, 10.21; H, 6.03.
Palladium(II) 3,7,13,17-Tetramethyl-2,8,12,18-
tetrabutyl-5,15-diphenylporphyrinate (III). A mix-
ture of 0.05 g of porphyrinVII and 0.12 g of PdCl2 (molar
ratio 1 : 10) was boiled in 60 mL of DMF for 15 s. The
reaction mixture was cooled and chromatographed on
neutral alumina (elution with hexane–chloroform 1 : 1).
The yield was 0.043 g (0.051 mmol), 85%. Rf = 0.77.
A decrease in the reactivity of VI with respect to
PdCl2 is presumably explained by the electronic effect
of the meso-substituent: the electron-accepting nitro-
gen atoms decrease the electron density on the tertiary
nitrogen atoms of the porphyrin reaction center and,
thus, suppress the coordination interaction of the cation
For PdC52H60N4 anal. calcd. (wt %): C, 73.30; N,
6.61; H, 7.14.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 53 No. 9 2008

PALLADIUM(II) OCTAALKYLPORPHYRINATES
1403
Electronic absorption spectra of Pd2+ porphyrinates in chlo-
roform
of the solvate complex with the porphyrin in the transi-
tion state.
A change in the reaction rate in going from V to VI,
VII, and VIII is evidence that the decisive contribution
to the energy of the transition state of the complex-
forming process is made by the coordination interac-
tion between the metal cation and the porphyrin nitro-
gen atoms.
Band I
Band II
Soret band λ,
Compound
λ, nm ( logε ) λ, nm ( logε ) nm ( logε )
I
558 (3.79)
559 (3.48)
553 (4.38)
553 (3.60)
560 (3.41)
527 (4.11)
525 (4.10)
519 (4.06)
528 (4.31)
527 (4.03)
587 (4.96)
412 (5.21)
420 (5.10)
412 (5.19)
414 (5.41)
423 (4.98)
384 (4.99)
II
III
IV
X
Elemental analysis data, mass spectra, and elec-
tronic absorption and IR spectra are consistent with the
structures of the synthesized compounds. The hypsoch-
romic shift of absorption bands in the electronic spectra
of palladium porphyrinate II as compared with Cu2+
3,7,13,17-tetramethyl-2,8,12,18-tetrabutyl-5,15-diaza-
porphyrinate (XI) is explained by the enhancement of
the π-dative interaction between the metal ion and the
∗
porphyrin macrocycle of the dπ–eg(π ) type (table).
∗
XI
Formation of metalloporphyrin from the porphyrin
ligand is accompanied by an increase in the symmetry
of a molecule. This is due to the substitution of a metal
atom for the two hydrogen atoms of the coordinating
center of the tetrapyrrole macrocycle and to equaliza-
tion of the geometric parameters of the pyrrole moieties
of porphyrin. A change in the molecular geometry upon
complexation clearly manifests itself in the IR spectra:
the number of bands decreases due to degeneracy of
odd in-plane vibrations. The spectra of porphyrinates
I−IV show the following characteristic changes as com-
pared with porphyrin ligand V studied in [11]: (1) the
bands due to N–H vibrations (stretching vibrations at
3320 cm–1 and bending vibrations at 965 and 685 cm–1)
disappear; (12) new strong “metal-sensitive” bands
appear at ≈1015 cm–1, which, according to [12] are due
to Pd–N vibrations. In addition, formation of metal-
loporphyrin gives rise to considerable changes in the
intensity of skeletal vibrations of the pyrrole rings of
porphyrin at 625 (I) and 715 (II) cm–1. A sharp decrease
in the band I intensity is accompanied by the buildup of
* Taken from [8].
eral substituents of the macrocycle remain almost unal-
tered.
We found that palladium chloride reacts with diaza-
porphyrin VI to form, in addition to compound II (the
complex in which the metal ion is located in the plane
of the macrocycle), complex X, in which Pd2+ ions are
bound to the mesoatoms of the macrocycle. Elemental
analysis supports the formation of the 3 : 2 complex of
porphyrinate II with PdCl2 (X). Analogous palladium
chloride complexes with tetrapyridylporphyrin were
described in [13]. Good outlook for compounds of this
type is determined by the selectivity and high sensitiv-
ity of porphyrins to low-energy impacts, which create
conditions for controlling their photophysical and elec-
band II. The frequencies typical of vibrations of periph- trochemical properties.
C4H9
C4H9
C4H9
C4H9
C4H9
C4H9
H3C
H3C
CH
H3C
CH3
CH3
H3C
H3C
CH3
CH3
Cl
Pd
Cl
3 Cl
Pd
Cl
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
Pd
Pd
N
N
Pd
CH3 H3C
H9C4
H9C4
H9C4
H9C4
H9C4
H9C4
(X)
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 53 No. 9 2008

1404
CHIZHOVA et al.
6. N. Zh. Mamardashvili, A. S. Semeikin, O. A. Golub-
ACKNOWLEDGMENTS
chikov, and B. D. Berezin, Zh. Org. Khim. 29 (6), 1213
This work was supported by the Russian Foundation
for Basic Research (project nos. 05-03-32055 and
06-03-81001-Bel) and program no. 7 “Chemistry and
Physical Chemistry of Supramolecular Systems and
Clusters” of the Division of Chemistry and Materials
Science of the RAS.
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1979).
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Koord. Khim. 22 (11), 866 (1996).
9. B. D. Berezin, Coordination Compounds of Porphyrins
and Phthalocyanine (Nauka, Moscow, 1978; Wiley, New
York, 1981).
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