Highly tunable emission properties of solid-state supramolecular compounds based on Eu mixed-lanthanide complexes and cucurbit[6]uril

Abstract

We obtained crystals of novel supramolecular compounds with cucurbit[6]uril which contain aquanitrato complexes of mixed lanthanides. The supramolecular approach was used to produce compounds exhibiting multicolor emission. An X-ray diffraction study demonstrated that the compounds have the following compositions: [{Ln¹_0.5Ln²_0.5(H₂O)₅(NO₃)}₂CB[6]](NO₃)₄·HNO₃·nH₂O (Ln¹ = Eu, Ln² = Pr (1), Nd (2), Sm (3), Gd (4), Tb (5) Dy (6), Er (8)), [{Ln¹_0.7Ln²_0.3(H₂O)₅(NO₃)}₂CB[6]](NO₃)₄·HNO₃·nH₂O (Ln¹ = Eu, Ln² = Ho (7)) and 2[Ln¹_0.5Ln²_0.5(H₂O)₈](NO₃)₃·CB[6]·2HNO₃·mH₂O (Ln¹ = Eu, Ln² = Yb (9)). The luminescence properties of compounds 1–9 were investigated in the solid state. The color purity of compound 6 is very close to zero, so it is well suited for white-light generation and can be used for WLED applications. A cool white LED device was fabricated by combining the supramolecular compound 6 and a UV LED chip (365 nm) at a voltage of 3.0 V; the CIE, CCT and CP were (0.328; 0.313), 5736 K and 2%, respectively. Compounds 5 and 6 have different glow colors when irradiated with different wavelengths; modulation of light emission in such compounds can be used to protect against counterfeiting.