The singlet oxygen quantum yields (phi(Delta)), LUMO energy levels (eV). photo stabilities under Xe-lamp irradiation of N,N'-di-dodecyl-3,4,9,10-bis(dicarboximide)perylene and N,N'-di-(1-dehydroabiethyl)-3,4,9,10-bis(dicarboximide)perylene, N-DODEPER and ABIPER, respectively, in different host matrices (solution. PVC and sol-gel matrix) are determined. Quenching of their emission by KI is found to give k(q) values of 3.5-37.4 x 10(9)M(-1) s(-1). Quenching is more efficient in solution phase than it is in immobilized phases. phi(Delta)'s of ABIPER and N-DODEPER are in negligible range. 0.090 and 0.095, respectively. The LUMO energy levels determined by cyclic voltammetric studies are 3.65 and 3.49eV for ABIPER and N-DODEPER, respectively. Neither ABIPER nor N-DODEPER showed degradation tendency in sol- gel matrix. Photooxidation of alpha-terpinene is performed with ABIPER and N-DODEPER as pholosensitizers. both in acetonitrile solutions and immobilized phases (PVC and sol-gel host matrices) by the use of two different irradiation sources, Na lamp and concentrated sun light. The photosensitizers exhibited different activities on the product profile, which were strongly dependent on the irradiation source, period of irradiation and the phase that the sensitizers were placed (solution or immobilized phases). Product analysis results point that in immobilized phases of PVC films 3,6-dioxoheptanal is the major product. In solution and immobilized phase of sol-gel ascaridol is the most abundant product. Superoxide anion radical, forms as reactive intermediate at photoinduced electron transfer process. directs the primary, mechanistic step of photooxidations. A secondary mechanistic step is being proposed for the clarification of product formations. (C) 2004 Elsevier Ltd. All rights reserved.