Silicon octaphenoxyphthalocyanines: photostability and singlet oxygen quantum yields

Photochemical properties of series of axially substituted silicon octapheno xyphthalocyanines with aryloxy, siloxy, aminoalkoxy, esters of carboxylic a cids and sulphonic acid esters residues as axial ligands were studied in di methylsulfoxide (DMSO) solution. It was found, that under Q-band excitation axial ligands in compounds studied have the propensity to be changed by hy droxyl groups with quantum yields in the range 10(-5) to 10(-2) depending o n the nature of the axial ligand. Axial substituent phototransformation was followed by slow photobleaching of dihydroxysilicon octaphenoxyphthalocyan ine (photoproduct) in self-sensitized singlet oxygen mediated oxidation of the macrocycle. Singlet oxygen quantum yields were found to be in the range 0.15-0.20 for majority of the phthalocyanines (Pc) studied. (C) 2001 Elsev ier Science B.V. All rights reserved.