Used as a ligand in coordination chemistry, particularly in the formation of metal complexes with transition metals such as ruthenium, iron, and copper. These complexes are often employed in catalysis, especially in reactions like oxidation and C–H activation. It is also utilized in the development of luminescent materials and sensors due to its ability to enhance the photophysical properties of metal ions. In addition, derivatives of 2-phenyl-1,10-phenanthroline find application in electrochemical devices and as components in dye-sensitized solar cells. Its rigid aromatic structure contributes to improved stability and electron delocalization in functional materials. It can also serve as a reagent for the colorimetric analysis of certain metal ions, forming colored complexes with heavy metals suitable for chemical sensors.