1,3-Diphenylisobenzofuran (DPBF) is a fluorescent probe used to detect various reactive species, particularly singlet oxygen, by undergoing a [4+2] cycloaddition reaction. This reaction results in 1,2-dibenzoylbenzene, a non-fluorescent product, and changes the fluorescence of DPBF, making it a valuable tool in chemical and biological research. It is also used as a model compound for singlet fission studies, in organic photovoltaic applications, and as a building block for synthesizing new polymers.