Used as a photochromic compound in specialty optical materials, particularly in the development of light-responsive lenses and coatings. Its spiro structure enables reversible ring-opening under UV light, resulting in a visible color change, making it suitable for applications in smart windows, ophthalmic lenses, and sensors. The presence of nitro and ester groups enhances photoresponsiveness and thermal stability. The pent-4-enoyloxy side chains allow for covalent incorporation into polymer matrices through crosslinking, improving durability and fatigue resistance in final products.