The photogeneration of singlet oxygen (O-1(2)) by tetrasodium salt of meso-tetrakis(4-sulfonatophenyl)porphyrins (H2TPPS) and some of its metal complexes (MTPPS; M = Cd2+, Zn2+), immobilized on cationically functionalized polystyrene (PS) beads, was studied. The generation of O-1(2) was monitored by a N,N-dimethyl-4-nitrosoaniline (RNO) bleaching assay. The rate of RNO bleaching was seen to be retarded in the presence of DABCO, a specific O-1(2) scavanger, providing evidence for the involvement of 10, as an active intermediate. The relative efficiencies of the generation of O-1(2), with respect to immobilized rose bengal (PS-RB), by different polymer-supported porphyrins, were determined to be 0.29, 0.27, and 0.16 for PS-H2TPPS, PS-ZnTPPS, and PS-CdTPPS, respectively. Binding of porphyrins to a polymer has been found to decrease the efficiency of the O-1(2) generation, which could be attributed to the structural deformation of the appended porphyrins. (C) 2003 Wiley Periodicals, Inc.