Eu3+ ternary and tetrakis complexes with carbazole and methyl group substituted dibenzoylmethane derivatives: Induction of aggregation enhanced emission

Two dibenzoylmethane (DBM) derivatives with methyl (Me-DBM) or carbazole (CBZ-DBM) substituents at the para-position of the phenyl ring and their four novel ternary and tetrakis Eu3+ complexes with 1,10-phenanthroline (PHEN) as a secondary ligand or tetraethylamonium ion (N+(Et)(4)) as the counter-cation were synthesized and characterized. The investigation of the optical properties of the complexes revealed that Me-DBM based compounds exhibit aggregation enhanced emission (AEE), while in the case of CBZ-DBM this effect is not observed. At the same time, the introduction of a carbazole substituent reduces the emission quantum yield of the complexes. The decrease in luminescence efficiency for CBZ-DBM based Eu3+ complexes is mainly attributed to the closely situated S-1 and T-1 energy levels of the ligand that obstruct the intersystem crossing process.