4-Bromopyrene is an organic compound featuring a pyrene core functionalized with a bromine atom at the 4-position. It is a yellow to orange crystalline solid with a molecular formula of C₁₆H₉Br. This compound is a key halogenated derivative of pyrene, a well-known polycyclic aromatic hydrocarbon (PAH). The primary application of 4-bromopyrene is as a crucial building block in materials science, particularly in the synthesis of organic semiconductors and optoelectronic materials. Its bromine atom serves as an excellent reactive site for cross-coupling reactions (e.g., Suzuki, Stille, or Sonogashira couplings), enabling the construction of extended π-conjugated systems. It is widely used in the development of organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs), and organic photovoltaic (OPV) cells, where pyrene-based derivatives are valued for their strong fluorescence, high charge carrier mobility, and good thermal stability. As a versatile synthetic intermediate, it is also employed in academic and industrial research to create more complex functional molecules, including dyes, sensors, and liquid crystals. Handling requires standard precautions for halogenated aromatic compounds.