K. Ozoemena et al., Comparative photosensitised transformation of polychlorophenols with different sulphonated metallophthalocyanine complexes in aqueous medium, J MOL CAT A, 176(1-2), 2001, pp. 29-40
The relative efficiencies for the oxidation of trichlorophenol (TCP) and pe
ntachlorophenol (PCP), sensitised by sulphonated phthalocyanine complexes c
ontaining Zn, Al, Sn and Si as central metals, were studied in aqueous solu
tions. For the first time, sulphonated silicon and tin phthalocyanines were
synthesised and their activity towards photosensitisation of singlet oxyge
n and photo-oxidation of polychlorophenols was examined. The efficiency of
the sensitised photo-oxidative degradation of polychlorophenols depends not
only on singlet oxygen quantum yield of sensitiser, but also on its stabil
ity. The influence of substrate structure and the pH of the solution on the
photo-oxidation efficiency, as well as on the sensitiser photodegradation
were studied. It was found that the contribution of the Type II (singlet ox
ygen-mediated) mechanism to the relative efficiency of the photosensitised
photo-oxidation of the phenol, decreased from phenol top-chlorophenol, TCP
and PCP, whereas Type I radical pathway increased. The results obtained for
PCP give evidence that electron transfer from the excited sensitiser to th
e substrate in its unionised form is responsible for enhanced sensitiser ph
otodegradation. (C) 2001 Elsevier Science B.V. All rights reserved.