The luminescence properties of three tetrakis dibenzoylmethane europium(III) complexes with different counter ions

We report the synthesis and emission properties of some europium compounds, which are highly luminescent under UV excitation, formed by the tetrakis complex anion of [Eu(dbm)4]− type with three different counter cations: N(C2H5)4+, P(C6H5)4+ and As(C6H5)4+. For (N(C2H5)4)[Eu(dbm)4], only one Eu3+ site, site (a), was observed with an emission lifetime of 0.301 ms and an evaluated quantum efficiency of 27.0% at 77 K. The presence of the P(C6H5)4+ or As(C6H5)4+ cations in the salts causes a decrease of the lifetime and the quantum efficiency of the Eu3+ ions occupying the site (a). Moreover, steric effects resulting from the incorporation of the larger counter ions into a crystal structure lead to a formation of another site, in which Eu3+ ions have significantly longer lifetimes and higher quantum efficiencies compared to the site (a), equal to 0.829 ms and 41% for (P(C6H5)4)[Eu(dbm)4], and 0.815 ms and 35% for (As(C6H5)4)[Eu(dbm)4], respectively.