1,3-Diiminoisoindoline is primarily used as an intermediate in the synthesis of phthalocyanine dyes and pigments. These dyes are widely applied in the coloration of plastics, textiles, and inks due to their excellent stability and vibrant colors. Additionally, it plays a role in the production of organic semiconductors, which are utilized in electronic devices such as solar cells, transistors, and light-emitting diodes (LEDs). Its ability to form complex structures makes it valuable in advanced material science and nanotechnology applications.