Emission-titration spectroscopy has been used to study the formation of five europium(III)β-diketonate complexes with NRH2(R = Prn, Pri, Bun, Bu8, or But) and R′OH (R′= Me, Et, Prn, Pri, Bun, Bu8, or But). The emission intensity of the 5D0→7F2 Eu3+ transition is found to be quite sensitive to the interaction between the chelate complex and a substrate molecule. Emission titrations and also Job's method of continuous variations have been used to find both the formation constant and stoicheiometry of all adducts studied. Depending on the chelate complex and substrate, either a 1 : 1 or a 1 : 2 chelate complex–substrate adduct is formed. Steric factors usually play only a minor role in this interaction, although in a few cases they influence the extent of the interaction.