K. Ozoemena et al., Photosensitized transformation of 4-chlorophenol in the presence of aggregated and non-aggregated metallophthalocyanines, J PHOTOCH A, 139(2-3), 2001, pp. 217-224
Citations number
33
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY
The photosensitizing properties of various water-soluble zinc and aluminum
phthalocyanines towards the phototransformation of 4-chlorophenol (4-Cp) ar
e presented. The complexes studied are the zinc (ZnPcS4) and aluminum (AlPc
S4) tetra-sulfophthalocyanines; the zinc and aluminum complexes containing
a mixture of differently substituted sulfophthalocyanines (represented as z
inc (ZnPcSmix) and aluminum (AlPcSmix), respectively); the zinc (ZnOCPc) an
d aluminum (AlOCPc) octacarboxy phthalocyanines. The AlPcSmix and ZnPcSmix,
complexes showed the best photocatalytic activity towards the transformati
on of 4-Cp. The values of singlet oxygen quantum yields of the sensitizers
were obtained, and it was found that the rates of 4-Cp photooxidation, in g
eneral, follow the efficiency of singlet oxygen photosensitization by the p
hthalocyanine complexes. At 4-Cp concentration below 10(-4) mol l(-1) photo
oxidation by singlet oxygen is the dominating mechanism of substrate photod
egradation, while at 4-Cp concentration above 10(-3) mol l(-1) the role of
Type I mechanism increases. Kinetic analysis indicates that interaction of
4-Cp with singlet oxygen mainly results in "physical" quenching with (k(q)
+ k(r)) = (13.5 +/- 3) x 10(8) mol(-1) l s(-1) and k(r) = (2.7 +/- 0.3) x 1
0(8) mol(-1) l s(-1) for the phenolate form of 4-Cp, which significantly li
mits the rates and quantum yields of 4-Cp photooxidation. (C) 2001 Publishe
d by Elsevier Science B.V.