Perylene fusion reaction

The third reaction stage is the most important and complex in the sequence, and is an alkaline fusion reaction. This is the synthesis stage in which the perylene chromophore is chemically formed, as well as the step in which many of the important physical properties of perylene tetracarboxylic acid diimide (PTCI) are determined. In the fusion reaction, (4) is fused with itself via a bimolecular nucleophilic substitution in the presence of molten alkali at temperatures in excess of 200 C. The resulting alkaline mass is then precipitated by slowly mixing into water. The subsequent slurry contains perylene in its reduced (leuco) form or salt. One of the several possible isomers of the lenco form is represented with the general formula (5). 

New processing techniques allow for more precise control of the fusion reaction and also the precipitation and oxidation stages. These include the continuous manufacture of PTCI (6) , and fusion of naphthalimide (4) under vacuum or in the absence of oxygen. Such advances are important for better understanding and control of the performance properties of perylene pigments. 

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