The first observation of emission of electronically-excited states of the divalent Eu2+⁎ ion in the new chemiluminescent system EuCl3·6H2O–Bui2AlH–O2 and the energy transfer from Eu2+⁎ ion to the trivalent ion, Tb3+

We have discovered a new bright blue chemiluminescence (CL) in the title system, visible to the naked eye, caused by broadband fd emission of electronically-excited divalent europium ion, Eu2+⁎ (λmax=465 nm). This is the first example in which a divalent lanthanide ion acts as a emitter and enhancer of liquid-phase CL. The CL was produced by adding the diisobutylaluminum hydride Bui2AlH to a suspension of EuCl3·6H2O crystalline hydrate in THF. Bui2AlH removes water molecules from the coordination sphere of Eu3+, and reduces Eu3+ to Eu2+. As a result, aluminoxane, isobutane, hydrogen and the complex EuCl2·(THF)x, where x≈2, are formed. And simultaneously excess of Bui2AlH is oxidized by oxygen traces generating a primary emitter, triplet-excited molecule, isobutyric aldehyde. The energy of the latter is transferred to the europium complex, EuCl2·(THF)x (x≈2), which emits blue light. The divalent Eu2+ ion is a much more efficient enhancer of CL in oxidation of Bui2AlH than the trivalent lanthanide ion Tb3+.