Microwave assisted synthesis of meso-tetraphenylporphyrin and its application for trace metal spectrophotometric determination

Article abstract of DOI:10.14233/ajchem.2013.14273

The synthesis of meso-tetraphenylporphyrin with quantitative yield in presence of p-toluene sulfonic acid as new catalyst under microwave irradiation was accomplished. The meso-tetraphenylporphyrin was characterized by means of elemental analysis, UV-visi

Full text of DOI:10.14233/ajchem.2013.14273

Asian Journal of Chemistry; Vol. 25, No. 11 (2013), 6102-6104
http://dx.doi.org/10.14233/ajchem.2013.14273
Microwave Assisted Synthesis of meso-Tetraphenylporphyrin and
Its Application for Trace Metal Spectrophotometric Determination
*
M.H. GIVIANRAD and A. BAHRAMI
Department of Chemistry, Science and Research Branch, Islamic Azad University, Tehran, Iran
*Corresponding author: Fax: +98 21 44868445; Tel: +98 21 44868449; E-mail: givianradh@yahoo.com
(Received: 7 July 2012;
Accepted: 29 April 2013)
AJC-13411
The synthesis of meso-tetraphenylporphyrin with quantitative yield in presence of p-toluene sulfonic acid as new catalyst under microwave
irradiation was accomplished. The meso-tetraphenylporphyrin was characterized by means of elemental analysis, UV-visible spectra, 1H
NMR spectra, infrared spectra and was used as chelating agent for direct determination of zinc ions by UV-visible spectroscopy.
Key Words: Microwave, Meso-tetraphenylporphyrin, Zinc, UV-visible spectroscopy.
INTRODUCTION
EXPERIMENTAL
The porphyrins comprise an important class of macrocyclic
compounds that serve nature in a variety of ways. The metal-
loporphyrin rings play an important role in important biological
systems. They have also been verified as efficient sentitizers and
catalyst in a number of chemical processes1,2.
All of materials were prepared in the quartz vessel. The
microwave oven used for synthesis of tetraphenylporphyrin
was LG, intellowave, 1000 W. UV-VIS spectra were mea-
sured by Cary100 Cone UV-VIS system. H NMR Spectra
and FT-IR spectra were recorded by Bruker, 300 MHz, 7T,
FT-H NMR system and thermo Nicolet FT-IR system, respec-
tively. All experimental procedures were performed at room
temperature.
All the reagents were used without more purification and
were of analytical grade. Glacial acetic acid was prepared by
adding 20 mL acetic anhydride to 1 liter glacial acetic acid.
Synthesis of meso-tetraphenylporphyrin: The meso-
tetraphenylporphyrin was synthesized by reaction of pyrrole
(0.4 mL) with benzaldehyde (0.53 mL) and 0.05 g of p-toluene
sulfonic acid in a Pyrex bottle under microwave irradiation at
2 min intervals for 10 min. Catalyst was removed by filtration
and washed thoroughly with ultrapure water.A chromatographic
column for separation of product mixture was prepared by
applying the silica gel (100-200 mesh size) and hexane eluting
with 7:1 (v/v) hexane-ethyl acetate solution.
Accordingly, the meso-tetraphenylporphyrin was prepared
and characterized by UV-visible, H NMR and FT-IR spectro-
metry. UV-VIS spectroscopy showed the characteristic soret
band at 418 nm and Q band at 511, 544, 594 and 653 nm in
toluene. The IR spectrum of H2TPP in KBr exhibited at 3430,
3314, 3140, 3054, 3021, 2920, 2856, 2603, 2529, 2352, 2257,
1886, 1469, 1399, 990, 962, 955, 798, 646 and 556 cm-1. Further-
more, H NMR spectrum and chemical shifts as shown in Table-
1 indicates the meso-substituted porphyrin structure.
Traditionally, porphyrins and metalloporphyrins syntheses
have been carried out in acidic conditions such as propanoic acid
or in a halogenated solvent3-5. In most cases, toxic oxidizing
reagents are used to convert the initial porphyrinogen product to
porphyrin. The porphyrin nucleus is a tetradentate ligand in with
the space available for a coordinated metal has maximum diameter
of approximately 3.7 Å. The porphyrin ring system and the
porphyrin complexes with transition metal ions are very stable6.
The application and importance of porphyrins and
metalloporphyrins have gained increasing interest in last
decades in analytical chemistry, significantly. The porphyrins
are one class of superior colourimetric compounds that became
useful as the reagents in spectrophotometric methods for the
determination of metal ions. Application of porphyrins as
spectrophotometric reagents have two problems, the first one
is that the absorption spectra of the reagent often overlaps with
metal chelates and the second one is that the rate of reaction is
lower than with the common reagent7.
In this paper meso-tetraphenylporphyrin has been synthe-
sized promptly, by combination of pyrrole and benzaldehyde
under microwave irradiation8. Moreover, it has been characterized
with UV-visible spectra, H NMR spectra, infrared spectra. The
complex of zinc meso-tetraphenylporphyrin was formed in room
temperature and was used for direct determination of zinc ions.

Vol. 25, No. 11 (2013)
Microwave Assisted Synthesis of meso-Tetraphenylporphyrin and Its Application 6103
TABLE-1
the absorbance was read. Calibration curve was applied for
HNMR CHEMICAL SHIFTS (∆[P.P.M.] FROM TMS) OF
meso-TETRAPHENYLPORPHYRIN
determination of the zinc ion of the samples (Table-3).
Parent
meso Subst- NH Substituent- Pyrrole Solvent
TABLE-2
compound ituent (Position)
H
-H
PARAMETERS FOR CALIBRATION CURVE
7.27
7.76
7.78
7.97
8.08
8.59
8.86
Samples
Wavelength
(nm)
Quantitative
Ra
RSDb
(%)
3.6
0
range (mg L-1)
Porphyrin
(C6H5)4
CDCl3
Zinc acetate
Zinc perchlorate
a Correlation coefficient; b Relative Standard Deviation
551
551
0.8-8.0
0.8-8.0
0.991 3.1
0.986 5.9
Preparation of solution: Glacial acetic acid was prepared
by adding 20 mL of acetic anhydride to 1 L glacial acetic
acid. At least 12 h before used the meso-tetraphenylporphyrin
solution was prepared by refluxing 0.269 g of meso-tetraphenyl-
porphyrin in 250 mL glacial acetic acid for 7 h. Zinc acetate
solution was prepared by dissolving reagent grade metal
acetates in glacial acetic acid. The acid was kept hot and water
added slowly in 0.5 mL.
TABLE-3
CONCENTRATIONS OF THE ZINC METAL IONS IN SAMPLES
Metal Zn2+ (mg L-1)
Added
2.00
5.00
7.00
Sample
Founded
2.50
5.12
Sample a
Sample b
Sample c
6.93
RESULTS AND DISCUSSION
Interferences: In this study interference of Mg(II), Co(II),
Fe(II) and Cu(II) ions, which are likely to form complexes
with meso-tetraphenylporphyrin in acetic acid was investigated
(Table-4). In quantitative determination of zinc with complex
formation, the most interaction was absorbed in presence of
copper ions, Due to the similarity of the absorption spectra
and also molar absorptivities of two metal complexes.
Microwave assisted procedure: Microwave irradiation
has recently been a fast procedure for chemical synthesis9-12
.
In this paper, the procedure for preparation of meso-
tetraphenylporphyrin, take only 10 min. However, the classical
methods present some experimental limitations likes, long
reaction times and sometimes low yields. These limitations
are not associated with microwave irradiation13,14. No solvent
is necessary in the reactions described in this study and the
reaction condition is moderate. The synthesis reactions have
been successfully repeated several times with identical results.
Determination of zinc: The zinc meso-tetraphenylpor-
phyrin complex was established, as soon as zinc acetate was
added to a solution of meso-tetraphenylporphyrin in glacial
acetic acid after 50-60 min at room temperature. The absorption
band of the complex was diminished at 551 nm (Fig. 1).
TABLE-4
THE INTERFERENCE OF THE METAL IONS
Salt
Reagent Wavelength
(nm)
Tolerable level of interference
concentration (mg L-1)
Cu(II) Fe(II) Co(II) Mg(II)
Zinc
acetate
TPP
551
N. Da
223
235
4.8
a Represents less than detection limit of method
Effect of metal salt: The absorbance of two identical
solutions of meso- tetraphenylporphyrin with zinc acetate and
meso-tetraphenylporphyrin with zinc perchlorate at 551 nm was
compared. Consequently, as shown in Table-2, the absorbance
was increased when zinc was added as zinc acetate. Moreover,
according to the theory of solvent systems acetate salt functions
as base and increases the concentration of the solvent anion15.
Wavelengh (nm)
Fig. 1. (a) Absorption spectra of zinc tetraphenylporphyrin complex in
glacial acetic acid; (b) Absorption spectra of meso-tetraphenyl-
porphyrin complex in glacial acetic acid
The calibration curve was organized by transferring zinc
acetate solution into series of 25 mL volumetric flasks and
adding appropriate aliquots of the meso-tetraphenylporphyrin
solution to each of them. Following 50 min the absorbance at
551 nm was read against a reference solution. The calibration
curve parameters are given in Table-2.
Sample was dissolved and prepared to yield the same
concentration, as was used in the calibration curve. The same
amount of meso-tetraphenylporphyrin was added and after 1 h
Concentration of zinc (ppm)
Fig. 2. (a) ZnTPP calibration curve with zinc acetate (b) ZnTPP calibration
curve with zinc perchlorate

6104 Givianrad et al.
Asian J. Chem.
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Conclusion
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meso-Tetraphenylporphyrin was synthesized by micro-
wave irradiation with innovative, effective and available
catalyst in 10 min with enhanced yield. Spectrophotometry
property of the porphyrin was applied to obtain the concen-
tration of zinc ions in the samples. Consequently, this study
offers a simple and appropriate method for indirect spectro-
photometric determination of metal ions, chelates, porphyrins
and metalloporphyrins, which could be dissociated in acetic
acid by effect on the complex formation equilibrium and
changes in the absorbance at 551 nm.
ACKNOWLEDGEMENTS
The authors are grateful to the Laboratory Complex of
Islamic Azad University for valuable technical assistance.
15. E.C. Franklin, J. Am. Chem. Soc., 46, 2137 (1924).
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