Fluorescence spectroscopy, laser flash photolysis (LPF), and density functional theory calculations have been performed to characterize the photobehavior of thiabendazole (1). Direct LFP of 1 results in the generation of a transient absorbing at lambda(max) = 570 nm identified as the triplet excited state ((3)1*). The intersystem crossing quantum yield is 0.91, and the triplet energy is 288 kJ mol(-1). The singlet-triplet energy gap is 84 kJ mol(-1). The behavior of thiabendazole within CDs results in a marked enhancement of the triplet lifetime, this change is attributed to the mobility restrictions of included 1 imposed by the cyclodextrin cavities. (C) 2012 Elsevier B.V. All rights reserved.