Water enhances quantum yield and lifetime of luminescence of europium(III) tris-β-diketonates in concentrated toluene and acetonitrile solutions

Europium tris-β-diketonates (Eu(L)3·nH2O) show concentration quenching of luminescence in toluene solutions due to the formation of weakly luminescent dimers. Addition of water to the concentrated toluene solutions of Eu(L)3·nH2O unexpectedly enhances quantum yield (φ) and lifetime of Eu3+ luminescence by causing dissociation of dimers and by reducing quenching of excited Eu3+ through the ligand-to-metal charge transfer (LMCT). Water also enhances φ of Eu(L)3·nH2O in acetonitrile (although to a lower extent than in toluene) only by reducing LMCT quenching of Eu3+.