A diazonium salt is a type of chemical compound that contains a positively charged nitrogen atom bonded to a carbon atom, which is also connected to a negatively charged ion. These salts are typically formed by the reaction of primary aromatic amines with nitrous acid. They are known for their stability in cold conditions and are often used in organic synthesis. Diazonium salts play a crucial role in the azo coupling reaction, where they react with aromatic compounds to form azo dyes. These dyes are widely used in textiles and other industries due to their vibrant colors and stability.