A highly-efficient blue-light excitable red phosphor: intramolecular π-stacking interactions in one dinuclear europium(iii) complex

Abstract

A series of ternary dinuclear europium(III) complexes [Eu₂(2,7-BTFDBC)_3−n(DBM)_2n(Phen)₂] (n = 0, 1, or 2) were synthesized by using 2,7-bis(4′4′4′-trifluoro-1,3-dioxobutyl)-(9-ethyl-9H-carbazole) (2,7-BTFDBC), dibenzoylmethane (DBM), 1,10-phenanthroline (Phen) and europium(III) ions. All these complexes display a broad excitation band in the blue region and high intensity emission with high colour purity. The intensity of emission significantly increases with the increase of DBM in [Eu₂(2,7-BTFDBC)_3−n(DBM)_2n(Phen)₂] (n = 0, 1, or 2). The theoretical predictions of the molecular geometry and electronic absorption spectrum of [Eu₂(2,7-BTFDBC)(DBM)₄(Phen)₂] confirm that the pendant phenyl domains engage in multiple T-shaped and parallel-displaced π-stacking interactions with the coordination sphere of two europium(III) centers. Using [Eu₂(2,7-BTFDBC)(DBM)₄(Phen)₂] as a red phosphor, a single red LED has been obtained with a ∼460 nm-emitting GaN chip.