Abstract Europium nitrate hexahydrate (Eu(NO3)3 · 6H2O) and heterocyclic ligands were dissolved to form complexes in poly(ethylene oxide) (PEO). The complexed Eu ion was electrochemically redox active, like that without ligands, in PEO oligomers. The fluorescence intensity from Eu3+ was enhanced 632-fold after complexation with 2,2′:6′,2″-terpyridine (Terpy). The improved red fluorescence based on Eu3+ decreased at a negative potential (−1.0 V vs Ag) of the working ITO glass electrode. A positive potential (+1.0 V) increased the intensity of red fluorescence, suggesting a chemically reversible redox process. It was confirmed that complexed Eu3+ was reduced in PEO by the cyclic voltammetry. However, the blue fluorescence based on Eu2+ was not observed, due to energy migration through the ligand. On the other hand, the blue fluorescent emission was induced by the complexation between Eu ions and 2,2′-bibenzoxazoline (BA). Cyclic voltammetry showed that europium ions complexed with BA were electrochemically redox active. The blue fluorescence emission intensity of these Eu ∣ BA complexes was controllable by changing the potential polarity. Mixed PEO solutions of Eu ∣ Terpy and Eu ∣ BA complexes showed the alternate emission color change between red and blue.