Photooxidation of 4-chlorophenol sensitised by iron meso-tetrakis(2,6-dichloro-3-sulfophenyl)porphyrin in aqueous solution

Abstract

The photosensitised degradation of 4-chlorophenol (4-CP) by iron meso-tetrakis (2,6-dichloro-3-sulfophenyl)porphyrin (FeTDCPPS) has been studied in aerated aqueous solution, and is shown to lead to formation of p-benzoquinone (BQ) and p-hydroquinone (HQ) as main photoproducts. In deaerated solution no p-benzoquinone was formed. The photolysis products were identified by high performance liquid chromatography (HPLC) and UV-visible spectroscopy. The photodegradation in aerated solution was also carried out in the presence of sodium azide (NaN 3 ) as a singlet oxygen [, and showed a significant decrease in the rate of photolysis, suggesting under these conditions, that Type II sensitisation is one of the dominant mechanisms of 4-CP degradation. Support for this comes from laser flash photolysis and time-resolved singlet oxygen phosphorescence measurements. However, these also show direct reaction between the excited porphyrin and 4-CP, indicating that there are two mechanisms involved in the chlorophenol photodegradation.

Substituent effects on the catalytic activity of a series of manganese meso-tetra(aryl)porphyrins: (2-, 3-, 4)-Pyridyl, 4-sulfonatophenyl and 3-sulfonato-4-methoxyphenyl groups compared to phenyl and 4-methoxyphenyl ones

“…meso-Tetra(pyridyl)- [19,20], meso-tetraphenyl- [21], mesotetra(4-OCH 3 phenyl)- [21], meso-tetra(4-sulfonatophenyl)- [22,23], meso-tetra(3-sulfonato-4-methoxyphenyl)porphyrin [22,23], were prepared and purified according to the literature methods. The sulfonated meso-tetra(aryl)porphyrins were isolated as the tetra-n-butylammonium salt by extraction of the sulfonated porphyrin into dichloromethane using tetra-n-butylammonium bromide as the phase transfer catalyst.…”

“…Metallation of the porphyrins with Mn(OAc) 2 ·4H 2 O, following the literature method, gave the corresponding Mn(III) complexes [22][23][24]. The Soret (and visible bands, the data in the parentheses) of MnT(2-py)P(OAc), MnT(3-py)P(OAc), MnT(4-py)P(OAc), MnTPP(OAc), MnT(4-OCH 3 )PP(OAc), MnTPPS 4 (OAc) and MnT(4-OCH 3 )PS 4 (OAc), appears at 468 ( max ) (570, 598), 469 ( max ) (572, 606), 467 ( max ) (572, 604), 468 ( max ) (574, 608), 468 ( max ) (574, 608), 470 ( max ) (576, 610), 480 ( max ) (583, 624) nm, respectively.…”

Zinc(II) phthalocyanines immobilized in mesoporous silica Al-MCM-41 and their applications in photocatalytic degradation of pesticides

“…The main photoproduct has been identified as 2,3,5,6-tetrachloro-hydroquinone [M−1] = 245, retention time 13.6 min, Scheme 2. The formation of this photoproduct has previously been described in photocatalytic reactions of this compound involving a radical mechanism [46][47][48]. However, the pentachlorophenol photoproducts can be more toxic than the corresponding source material as determined by Jardim et al [49], where acute toxicity tests of samples at different time intervals of light exposure, were carried out by measuring the respiratory inhibition in the bacteria Escherichia coli.…”

Synthesis of polymeric phthalocyanine sulfonate photosensitizer and its photodegradation on rhodamine B in aqueous medium

“…In homogenous catalyst system, Type II mechanism via singlet oxygen catalyzed by Pcs was predominant in photocatalyst as reported. [5][6][7] Pc(S 0 ) Pc(S 1 ) Pc(T 1 ) ( 1 )…”