1,10-Phenanthroline-2,9-dicarboxylic anhydride is a heterocyclic organic compound derived from 1,10-phenanthroline. It features a rigid, planar phenanthroline core with two carboxylic acid groups condensed into an anhydride functionality at the 2 and 9 positions. This structure makes it a versatile bidentate chelating ligand precursor. Its primary application is in the field of materials chemistry, particularly for the synthesis of functional coordination complexes. It serves as a key precursor for constructing highly conjugated and rigid ligands used in the development of luminescent materials, such as those for organic light-emitting diodes (OLEDs) and electroluminescent devices. The anhydride group readily reacts with amines to form imide-based ligands that can coordinate with various metal ions (e.g., Ru, Ir, Eu) to create efficient phosphorescent or electroluminescent complexes. Furthermore, due to its defined heterocyclic structure and reactive anhydride group, it is also employed as a specialized organic synthesis building block for constructing complex molecular architectures in supramolecular chemistry and for preparing analytical reagents in chelatometric titrations.