Ru(dpp)3(PF6)2 is a complex containing the metal ruthenium (Ru) and acts as a chemiluminescent oxygen probe. The compound [Ru(dpp)3]2+ emits light via metal-to-ligand charge transfer (MLCT), where charge transfers from Ru to the ligand, resulting in fluorescence. This fluorescence is effectively quenched by molecular oxygen, making Ru(dpp)3(PF6)2 widely utilized in biosensors, environmental monitoring, and materials science. Additionally, the ability of Ru2+ in Ru(dpp)3(PF6)2 to oxidize to Ru3+ is instrumental in the design and development of solid-state electroluminescent cells.