Synthesis and characterization of 5 , 10 , 15 , 20-Tetrakis ( 4-Tolyl ) Porphyrin and its Tin and Cobalt complexes : investigation of their photodynamic properties in degradation of Methylene blue

In present work, the synthesis and characterization of 5, 10, 15, 20-tetrakis (4-tolyl) porphyrin [H2TTP] and its metal complexes with tin and cobalt were investigated. H2TTP complex was characterized by UV-vis, FT-IR and H NMR spectra. The photodynamic degradation activity of these compounds was investigated by destruction of methylene blue under visible light irradiation. Keyword: Synthesis, Porphyrin, Photodynamic degradation, Methylene blue 1. Introdudtion Colored wastewater from textile industry is one of the largest sources of pollution of the aquatic environment. One of the so used colors in the textile industry is methylene blue. Due to limited efficiency, the biological treatment of pollutants is not satisfying [1]. Photodynamic treatment provides an eco-friendly pathway for degradation of pathogenic microorganisms from wastewater. This technique is considered as a promising and new technology for wastewater treatment [2]. Use of porphyrin absorbents for separating several pollutants including methylene blue has been specially considered. Porphyrins, the pigments of life, are having a 2D 18 π-electron structure, and they play a prospective role in enzymes, catalytic reactions, PDT and conversion of solar energy [3]. The efficiency of the porphyrin photosensitizing effect depends on the presence and nature of complexed metal ions and on the structure of the side chains of the tetrapyrrole core [4]. Metalloporphyrins are an important group of sensitizers with a porphyrin skeleton. Their photosensitizing properties have led to their utilization in photodynamic therapy. The nature of the central metal ion has significantly affected their photophysical properties [5]. Certain metalloporphyrins such as SnPp are being tested as drugs for the treatment of Neonatal hyperbilirubinemia [6]. This article has been specially considered the use of porphyrin photosensitizer for degradation of several pollutants including methylene blue. 2. Experimental 2.1. Synthesis of 5, 10, 15, 20-Tetrakis-(4-Tolyl) Porphyrin (H2TTP) To prepare H2TTP, pyrrole and 4-methylbenzaldehyde were refluxed in propionic acid for 2h at 138C. The product was obtained by filtration and washed with DI.IR (KBr): ʋmax = 3448, 3024, 2920, 2852, 1635, 1471, 1350, 1218, 1182, 968, 798, 738, and 526 cm. 2.2. Synthesis of Sn(II) 5, 10, 15, 20-Tetrakis-(4-Tolyl) Porphyrin To prepare tin complexe of H2TTP, SnCl2.2H2O and H2TTP were refluxed in pyridine for 6h at 120 ̊C. The complex was obtained with filtration. 2.3. Synthesis of Co(II) 5, 10, 15, 20-Tetrakis-(4-Tolyl) Porphyrin To prepare Cobalt complex of H2TTP, CoCl2·6H2O (0.1 g, 6 mmol), and H2TTP (0.1 g, 1 mmol) were refluxed in DMSO (28 mL) for 24 h. Then, 1 M HCl (ca. 80 mL) was added to the solution to cause deposition of the crude product as a purple solid, which was collected by filtration, washed with water, and dried in vacuo. The prepared sample was redissolved in 0.1 M NaOH (ca. 25 mL) followed by addition of 1 M HCl (ca. 40), which caused deposition of the product as a purple solid. The final products was collected by filtration and dried in vacuo [7]. 3. Results and discussion 3.1. FT-IR spectra analysis The FT-IR spectra were recorded on a FT-IR spectrometer (4000 400 cm) in KBr pellets. As shown in Fig. 1, FT-IR spectra of compound with the characteristic peak of C-H vibration of toluene in the range of 2920 cm indicated that the relative schiff base porphyrin were successfully synthesized. Moreover disappearance of N-H vibration around 3448 cm and emergence of C-H vibration of aromatic around 3024 cm predicated that the related metalloporphyrin were also quantitatively prepared. Scheme. 1. Synthesis of 5, 10, 15, 20-tetrakis (4-tolyl) porphyrin (H2TTP), Co(II) H2TTP and Sn(II)H2TTP 3.2. H NMR Spectra analysis The H NMR spectrum of H2TTP was recorded at 400 MHz and in CDCl3. Peak appeared in the weakest field can be attributed to the pyrrole hydrogens. Peak in the area of almost 3 ppm can be attributed to the methyl groups of H2TTP. As shown in Fig. 2, in stronger fields of H NMR spectrum, in the range of 7 to 8 ppm, two peaks can be seen. These peaks are related to the aromatic hydrogens which attached to the phenyl ring. Because of the differences in the chemical environment of ortho and meta hydrogen, these peaks appear in two different fields. Fig. 1. The FT-IR Spectrum of 5, 10, 15, 20-tetrakis (4-tolyl) porphyrin Fig. 2. The H NMR Spectrum of 5, 10, 15, 20-tetrakis(4-tolyl) porphyrin 40 55 70 85 100 400 90


Introdudtion
Colored wastewater from textile industry is one of the largest sources of pollution of the aquatic environment.One of the so used colors in the textile industry is methylene blue.Due to limited efficiency, the biological treatment of pollutants is not satisfying [1].
Photodynamic treatment provides an eco-friendly pathway for degradation of pathogenic microorganisms from wastewater.This technique is considered as a promising and new technology for wastewater treatment [2].Use of porphyrin absorbents for separating several pollutants including methylene blue has been specially considered.
Porphyrins, the pigments of life, are having a 2D 18 π-electron structure, and they play a prospective role in enzymes, catalytic reactions, PDT and conversion of solar energy [3].The efficiency of the porphyrin photosensitizing effect depends on the presence and nature of complexed metal ions and on the structure of the side chains of the tetrapyrrole core [4].
Metalloporphyrins are an important group of sensitizers with a porphyrin skeleton.Their photosensitizing properties have led to their utilization in photodynamic therapy.The nature of the central metal ion has significantly affected their photophysical properties [5].Certain metalloporphyrins such as SnPp are being tested as drugs for the treatment of Neonatal hyperbilirubinemia [6].This article has been specially considered the use of porphyrin photosensitizer for degradation of several pollutants including methylene blue.

Synthesis of Co(II) 5, 10, 15, 20-Tetrakis-(4-Tolyl) Porphyrin
To prepare Cobalt complex of H 2 TTP, CoCl 2 •6H2O (0.1 g, 6 mmol), and H 2 TTP (0.1 g, 1 mmol) were refluxed in DMSO (28 mL) for 24 h.Then, 1 M HCl (ca.80 mL) was added to the solution to cause deposition of the crude product as a purple solid, which was collected by filtration, washed with water, and dried in vacuo.The prepared sample was redissolved in 0.1 M NaOH (ca. 25 mL) followed by addition of 1 M HCl (ca.40), which caused deposition of the product as a purple solid.The final products was collected by filtration and dried in vacuo [7].

FT-IR spectra analysis
The FT-IR spectra were recorded on a FT-IR spectrometer (4000 -400 cm -1 ) in KBr pellets.
As shown in Fig. 1, FT-IR spectra of compound with the characteristic peak of C-H vibration of toluene in the range of 2920 cm -1 indicated that the relative schiff base porphyrin were successfully synthesized.Moreover disappearance of N-H vibration around 3448 cm -1 and emergence of C-H vibration of aromatic around 3024 cm -1 predicated that the related metalloporphyrin were also quantitatively prepared.

H NMR Spectra analysis
The 1 H NMR spectrum of H 2 TTP was recorded at 400 MHz and in CDCl 3 .Peak appeared in the weakest field can be attributed to the pyrrole hydrogens.Peak in the area of almost 3 ppm can be attributed to the methyl groups of H 2 TTP.As shown in Fig. 2, in stronger fields of H NMR spectrum, in the range of 7 to 8 ppm, two peaks can be seen.These peaks are related to the aromatic hydrogens which attached to the phenyl ring.Because of the differences in the chemical environment of ortho and meta hydrogen, these peaks appear in two different fields.

UV-Vis Spectra Analysis
As shown in Fig. 3, the UV-vis spectrum of H 2 TTP showed a band centered at 420 nm (Soret band), and four Q bands absorptions at 515, 550, 590 and 650 nm, respectively.The insertion of Sn(II) and Co(II) into the porphyrin ring caused redshift of 3 nm of the corresponding Soret band as well as a decreasing number of Q bands in UV-vis spectrum.This is because when the hydrogen ions of N-H was replaced by Sn(ll) and Co(II), the symmetry of porphyrin ring increases [4].

Fig. 4 Fig. 3 .
Fig. 4 shows the UV-Vis absorption spectrum of the MB solution at different reaction times, in which the absorption spectrum of the original solution shows two characteristic peaks at 610 and 660 nm.It is clear that under the irradiation of the visible light, the MB concentration is gradually decreased as a result of the visible light irradiation.