1,4-Diiodobenzene, also called para-diiodobenzene, is an organic chemical compound used as a building block in organic synthesis for creating pharmaceuticals, agrochemicals, and advanced materials like liquid crystals. It features a benzene ring with two iodine atoms in a para (1,4) position, making it useful in cross-coupling reactions like the Suzuki reaction to form new carbon-carbon bonds. This versatile compound is also an ingredient in antiseptics and disinfectants and a reagent in life science research.

1,3-Diiodobenzene, also known as m-diiodobenzene, is an aromatic organic compound with the chemical formula C₆H₄I₂. It consists of a benzene ring with two iodine atoms attached to it at the meta positions, meaning they are separated by one carbon atom on the ring. This compound is primarily used as a building block in organic synthesis for creating various iodinated compounds and as an intermediate in the production of pharmaceuticals, agrochemicals, and materials science applications, particularly for organic semiconductors.