Photo-catalytic activity of cationic zinc(II) complexes of phthalocyanine and porphyrazine derivatives loaded on the surface of silica gel

Cationic 2,9,16,23-tetra(3-N,N,N-trimethylaminoethyloxy) phthalocyaninatozinc(II) (complex 1) and 2²,2³-di(4-N,N,N- trimethylaminophenyl)benzo[b]-7,8,12,13,17,18-hexa(4-t-butylphenyl) porphyrazinatozinc(II) (complex 2) were loaded on the surface of silica gel by use of an electrostatic interaction with deprotonated silanol groups of silica gel. While complex 1 formed its dimer with increase in the amount of the complex in the composite, complex 2 hardly formed the dimer in the composite due to the steric hindrance of its peripheral substituents. 1,3-diphenylisobenzofuran was photo-oxidized using the composites as the sensitizer in aerated methanol. The reaction proceeded with singlet dioxygen generated by the visible-light irradiation upon the sensitizer. While the initial reaction rate with the composite of complex 2 steadily increased in accordance with increase in the amount of the complex, that with the composite of complex 1 at first increased, but subsequently decreased due to the formation of the photo-inactive dimer. Bilirubinditaurate was also photo-oxidized using the composites as the sensitizer in an aerated aqueous solution. The reaction proceeded with superoxide instead of singlet dioxygen. The relationship between the initial reaction rate and the amount of the complex was similar to that in methanol.