Luminescent Soft Material: Two New Europium-Based Ionic Liquids

Bright Solvent-Free Luminescent Liquid with Magnetism Composed of a Thiocyanate Complex of Ce(III)

Ionic liquids composed of a thiocyanate complex of Ce(III) exhibit bright cyan photoluminescence with a quantum yield close to 40% in addition to paramagnetism. The morphology of a droplet of ionic liquid changes in response to solvent vapor as a stimulus. The emission lifetime and thermal property are characterized. The Weiss temperature is evaluated from the magnetic property measurements, which indicates that antiferromagnetic exchange interaction exists between Ce(III) ions. Insight into the characteristics of the electronic transitions in the Ce(III) complex is obtained using quantum chemical calculations. Thiocyanate complexes of Ce(III) are demonstrated as promising building blocks to produce solvent-free luminescent functional materials.

Forcing Dicyanamide Coordination to f-Elements by Dissolution in Dicyanamide-Based Ionic Liquids

A robust general route to lanthanide dicyanamide (DCA^–) complexes has been developed where f-element salts are dissolved in DCA^–-based ionic liquids (ILs) directly or formed in situ, forcing coordination of these normally weakly coordinating soft N-donor anions, even in an ambient, non-moisture-excluding environment. A series of lanthanide complexes [C₂mim][Ln(DCA)₄(H₂O)₄] (C₂mim = 1-ethyl-3-methylimidazolium; Ln = La, Nd, Eu, Tb, Dy, and Yb) and [C₂mim]_3n[La(OH₂)₄(μ²-DCA)₄]_n[La(OH₂)₂(μ³-DCA)₃(μ²-DCA)₄]_2n(Cl)_4n were crystallized under a variety of conditions using this methodology and structurally characterized using single crystal X-ray diffraction. Although not all examples were isostructural, the dominant feature across the series was the presence of [Ln(DCA)₄(H₂O)₄]⁻ anionic nodes with all terminal DCA^– ligands accepting hydrogen bonds from the coordinated water molecules forming a 3D metal organic framework. To determine if any structural clues might aid in the further development of the synthetic methodology, the metal-free IL [C₁mim][DCA] (C₁mim = 1,3-dimethylimidazolium), a room-temperature solid, crystalline analogue of the reaction IL, which is liquid at room temperature, was also prepared and structurally characterized. The ready isolation of these compounds allowed us to begin an investigation of the physical properties such as the luminescence at room and low temperatures for the Eu, Tb, and Dy representatives.

Direct dissolution of lanthanide chloride hydrates in the DCA⁻ ionic liquids leads to coordination of DCA⁻ anions to Ln³⁺ under full displacement of chloride and partial displacement of water ligands leading to the formation of metal organic frameworks under ambient conditions. X-ray analyses reveal a significant influence of the hydrogen bonding and lanthanides’ size on crystallographic disorder in their crystal structures.

Sonochemical synthesis of 0D, 1D, and 2D zinc oxide nanostructures in ionic liquids and their photocatalytic activity

Ultrasound synthesis of zinc oxide from zinc acetate and sodium hydroxide in ionic liquids (ILs) is a fast, facile, and effective, yet highly morphology- and size-selective route to zinc oxide nanostructures of various dimensionalities. No additional organic solvents, water, surfactants, or templating agents are required. Depending on the synthetic conditions, the selective manufacturing of 0D, 1D, and 2D ZnO nanostructures is possible: Whereas the formation of rodlike structures is typically favored, ZnO nanoparticles can be obtained either under strongly basic conditions or by use of ILs with a long alkyl chain, such as 1-n-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C(n)mim][Tf(2)N]; n>8). A short ultrasound irradiation time favors the formation of ZnO nanosheets. Prolonged irradiation leads to the conversion of the ZnO nanosheets into nanorods. In contrast, ionothermal synthesis (conventional heating) does not allow for morphology tuning by variation of the IL or other synthesis conditions, as the longer reaction times required lead always to the formation of well-developed hexagonal nanocrystals with prismatic tips. The ZnO nanostructures synthesized by using ultrasound were efficient photocatalysts in the photodegradation of methyl orange. The photoactivity was observed to be as high as 95 % for ZnO nanoparticles obtained in [C(10)mim][Tf(2)N].