Highly luminescent organic-inorganic hybrid materials have been prepared by combining task-specific polymerized ionic liquids (PILs) based on the 1-alkyl-3-vinylimidazolium cation ([CnVim]+ (with n = 2-6)) with suitable halides of trivalent lanthanides such as europium and terbium. The resulting materials have been characterized by 1H nuclear magnetic resonance, Fourier transform infrared, UV-Vis and photoluminescence spectroscopy. They show bright and intense luminescence over a wide range of excitation wavelengths, which particularly for the Eu3+ containing compounds, benefits from efficient energy transfer from the organic aromatic moieties in the PIL to the emitting level of the lanthanide(iii) ion. In the case of the Tb3+ ion, the emission benefits from excitation into the Tb3+ d levels. The emission colour can be tuned from green to red for Tb and Eu respectively. This includes bright white emission for Eu that can be achieved by altering the excitation wavelength. The easy processability of these novel PILs renders them interesting for a wide range of optical applications.

Since the discovery of AlQ3 (Q = 8-quinolinolato) quinolinato complexes, they have been extensively scrutinized as emitter materials for organic lighting. Herein, we report on the first representatives of a series of tetrabutylphosphonium tetrakis(8-quinolinolato)lanthanidate complexes [P4444][Ln(Q)4]·2X (Ln = Dy-Lu and Y; X = H2O for Ln = Dy-Tm, Lu and Y and (CH3)2CO for Ln = Yb), which are synthesised by a simple metathesis reaction of the respective potassium tetrakis(8-quinolinolato)lanthanidate salts with tetrabutylphosphonium bromide in acetone at room temperature. Single-crystal X-ray diffraction reveals that Ln(iii) is coordinated by four bidentate 8-quinolinato ligands in the form of a distorted square antiprism. The distinct [Ln(Q)4]− anions interact with the [P4444]+ cations through secondary bonding interactions, such as CH-π and van der Waals interactions, in addition to electrostatic coulombic interactions. Although these compounds contain crystal water/solvent molecules (and their synthesis does not require an inert atmosphere), they do not enter the metal coordination sphere but form pairwise intramolecular hydrogen bonds with the two 8-quinolinato ligands of the complex lanthanide anions. Combined differential scanning calorimetry-thermogravimetric analysis indicates that crystal water is lost at around 100 °C and [P4444][Ln(Q)4] is formed, which is stable up to 300 °C, where further degradation occurs. All compounds feature strong emission in the green region, originating from the π* → π transitions within the 8-quinolinato ligand, with lifetimes in the nanosecond range. The luminescence colour changes from blue-green to yellow-green depending on Ln3+, which opens up additional directions in the colour tuning of emitters for organic lighting applications.

A set of IL-forming ion combinations has been studied to gain a deeper understanding of how, aside from obvious electrostatic interactions and ion size effects, secondary bonding such as hydrogen as well as halogen bonding and van der Waals interactions along with conformational and structural flexibility influence the crystallization behavior of potentially IL forming salts. The scrutinized ions have been specifically chosen to allow for unraveling preferential interactions of functional groups that may favor or disfavor crystallization with respect to secondary bonding interactions, i.e., primary and quaternary ammonium cations of variable alkyl chain lengths, which were also endowed with hydroxy groups, combined with formate and bis(trifluoromethanesulfonyl)amide anions. The background is to provide a deeper fundamental understanding of how to intentionally pair cations and anions that will not support the formation of a crystalline solid but rather IL formation, an approach described as “anti-crystal engineering”. This concept is based on the idea to avoid combining ions that are strong supramolecular synthons for crystallization. To this avail, the crystallization behavior of salts constituted of combinations of selected ions bearing different structural, supramolecular crystallization motifs has been studied in detail by low-temperature differential scanning calorimetry (DSC). Single crystal X-ray structure analysis has been used to elucidate ion packing and preferential interactions whenever crystalline solid formation is observed. The study reveals that the lowest melting points are supported by cation-anion combinations that have the least hydrogen bonding. However, if there are multiple possibilities of H-bonding for an ion with its counteranion, this bonding frustration leads as well to low melting points-albeit they are still higher compared to ion combinations with no H-bonding capacity. Through a careful balance of primary and secondary, directional and nondirectional interactions, it was possible to rationally identify a record class of ionic liquids, which combine exceptionally high decomposition points (440-450 °C) with an enormously high liquid range around of more than 500 °C and no tendency for solidification down to well below ambient temperature (−90 °C). These ILs are formed by bis(trifluoromethane)sulfonylamides with quaternary ammonium ions that bear an −OH group in the side chain.

Commonly accepted design concepts for ionic liquids (ILs) state that the constituting ions must be large and carry low, well-dispersed charges. A series of ILs based of pentadeca charged ILs with pentanuclear linear {Ln₅} units ([Ln₅(C₂H₅-C₃H₃N₂-CH₂COO)₁₆(H₂O)₈](Tf₂N)₁₅ (C₃H₃N₂ = imidazolium moiety, Tf₂N = bis(trifluoromethanesulfonyl)amide) with Ln = Er, Ho, Tm) demonstrates that these criteria are not absolute. Highly charged ions can also support IL formation, provided they are sufficiently large. Expanding the series of these unconventional, record pentadeca charged with new lanthanide representatives, led to the discovery of additional unprecedented properties for ILs: The Gd compound exhibits a strong magnetocaloric effect (MCE) in the liquid state with a maximum magnetic entropy change of −ΔS_M = −11 J⋅kg⁻¹⋅K⁻¹ at 2 K for Δμ₀H = 7 T. Albeit the Dy representative shows slow magnetic relaxation, the relaxation times are not favorable for practical application as a molecular magnet. Lastly, for both the Gd and the Y compound, phosphorescence in the seconds time scale is observed, which is, to the best of our knowledge, the longest ever reported for an IL.

Three nonhalogenated ionic liquids (ILs) dissolved in 2-ethylhexyl laurate (2-EHL), a biodegradable oil, are investigated in terms of their bulk and electro-interfacial nanoscale structures using small-angle neutron scattering (SANS) and neutron reflectivity (NR). The ILs share the same trihexyl(tetradecyl)phosphonium ([P_6,6,6,14]⁺) cation paired with different anions, bis(mandelato)borate ([BMB]⁻), bis(oxalato)borate ([BOB]⁻), and bis(salicylato)borate ([BScB]⁻). SANS shows a high aspect ratio tubular self-assembly structure characterized by an IL core of alternating cations and anions with a 2-EHL-rich shell or corona in the bulk, the geometry of which depends upon the anion structure and concentration. NR also reveals a solvent-rich interfacial corona layer. Their electro-responsive behavior, pertaining to the structuring and composition of the interfacial layers, is also influenced by the anion identity. [P_6,6,6,14][BOB] exhibits distinct electroresponsiveness to applied potentials, suggesting an ion exchange behavior from cation-dominated to anion-rich. Conversely, [P_6,6,6,14][BMB] and [P_6,6,6,14][BScB] demonstrate minimal electroresponses across all studied potentials, related to their different dissociative and diffusive behavior. A mixed system is dominated by the least soluble IL but exhibits an increase in disorder. This work reveals the subtlety of anion architecture in tuning bulk and electro-interfacial properties, offering valuable molecular insights for deploying nonhalogenated ILs as additives in biodegradable lubricants and supercapacitors.

Our recent observations of an unexpected Ce(III) hydrolysis product from the reaction of 4-amino-1,2,4-triazole (4-NH₂-1,2,4-Triaz) with CeCl₃·7H₂O, [Ce₆(μ₃-O)₄(μ₃-OH)₂(μ₃-Cl)₂(Cl)₆(μ₂-4-NH₂-1,2,4-Triaz)₁₂]·7H₂O, the first high-nuclearity lanthanide complex where all Ln atoms are connected pairwise through 12 N-donor ligands or 12 neutral bridging ligands of any type, prompted us to explore the utility of this ligand in trapping additional f-element examples. Reactions of LnCl₃·6H₂O (Ln = Nd, Eu, Ho) with a large excess of 4-NH₂-1,2,4-Triaz (20 equiv) and with the addition of small amounts of water to help solubilize the metal salts led to the isolation of the unique hydrolysis products [Nd₆(μ₃-OH)₈Cl₆(μ₂-4-NH₂-1,2,4-Triaz)₁₂][Cl₄]·2H₂O, [Eu₆(μ₆-Cl)_0.23(μ₃-O_0.77)4(μ₃-O)_2.6(μ₃-Cl)_0.4Cl₆(μ₂-4-NH₂-1,2,4-Triaz)₁₂], and [Ho₆(μ₆-Cl)_0.21(μ₃-O_0.79)₄(μ₃-OH)₂Cl₆(μ₂-4-NH₂-1,2,4-Triaz)₁₂][Cl]_3.4. We also report a Ce(III) analogue prepared in glassware contaminated with Pb(OAc)₂, namely, [Ce₆(μ₃-OH)₈(BrPbBr₅)(μ₂-4-NH₂-1,2,4-Triaz)_11.5(OH₂)₆][Pb_0.84Br_4.2][Br]_3.8·2(4-NH₂-1,2,4-Triaz)·3.6H₂O. The Nd(III) complex is the structurally most ordered with a clear [Nd₆(μ₃-OH)₈] cluster core, while the Eu(III) and Ho(III) compounds contain partial occupancy of a μ6 position and thus result in an incomplete Ln₆O₉ cluster core formation. The crystallographic results suggest that the 4-NH₂-1,2,4-Triaz ligand brings Ln(III) ions together, followed by the formation of an Ln₆O₈ or Ln₆O₉ core with whatever remaining anions or ligands can be incorporated. Given the complexity of the hydrolysis products of nuclear waste, we expect to continue to find a myriad of closely related complex structures of these types for the f-elements. 

Two series of isostructural intermetallics have been discovered in our search for new compounds with fused honeycomb motifs, both stable at elevated temperatures (1073 K). They crystallize with orthorhombic unit cells - La4Co4M (M = Sn, Sb, Te, Pb, Bi, SG Pbam, a = 8.247-8.315(2), b = 21.913-22.137(7), c = 4.750-4.664(2) angstrom, V = 850.5-869.5(4) angstrom 3, Z = 4) and La3Ni3M (M = Al, Ga, SG Cmcm, a = 4.1790-4.2395(1), b = 10.4921-10.6426 (6), c = 13.6399-13.7616(8) angstrom, V = 606.72-612.05(7), Z = 3). The crystal structures represent interesting variations of semiregular tilings of corrugated anionic layers and predominantly cationic zigzag motifs. The La4Co4M compounds reveal a complex type of ordering with a high degree of frustration as could be expected for the Kagome ' -related lattices, while magnetic ordering in the La3Ni3M series is less evident. Electronic structure calculations have been performed for multiple compounds within both series revealing metallic character and visible local minima around the Fermi level. The bonding picture is characterized by nearly equal contributions from the anionic and the cationic components.

The La-poor part of the ternary La–Ni–Si system has been explored leading to the discovery and structural characterization of four new polar intermetallic compounds. LaNi₅Si₂ [BaAu₅Ga₂ type, oP64, space group Pnma, a = 7.8223(7) Å, b = 6.3894(6) Å, c = 17.843(2) Å, V = 891.8(2) ų, Z = 8] features a diamond (lonsdaleite)-like homoatomic Ni framework and is the first Ni representative of a larger family of compounds typically formed by aurides. La₂Ni₈Si₃ [Eu₂Ni₈Si₃ type, tP52, P4₂/nmc, a = 10.0278(3) Å, c = 7.5047(4) Å, V = 754.65(6) ų, Z = 4] is characterized by homoatomic Ni₄ tetrahedra and rectangles. LaNi₅Si₃ [SrNi₅P₃ type, oS36, Cmcm, a = 3.722(2) Å, b = 11.759(5) Å, c = 11.622(3) Å, V = 508.7(3) ų, Z = 4] is governed by extensive heteroatomic bonding and characterized by homopolyhedral packing. La₃Ni₄Si₂ [Ce₃Ni₄Si₂ type, mC36, C2/c, a = 15.819(1) Å, b = 6.0068(5) Å, c = 7.4918(6) Å, β = 103.163(5)°, V = 693.17(10) ų, Z = 4] is a new member of homologous series that includes La₃Ni₃Si₂ and La₃Ni_3.5Si₂. We conclude that the similar radii and electronegativities of Ni and Si are the reason for the incredible diversity of compositions and structures in this system.

Magnetic materials with noncollinear spin arrangements are of considerable interest owing to their potential use in emerging computational technologies and memory devices. Competing magnetic interactions, i.e., magnetic frustration, are one of the main origins of noncollinear magnetic structures. While frustrated systems have been mainly studied among magnetic insulators, combining magnetic frustration with electrical conductivity can allow simultaneous charge and spin manipulation, which is crucial for the design of electronic devices. Here, we present a new intermetallic solid solution LaMn_2–xAu_4+x, whose crystal structure accommodates magnetically frustrated Mn square nets. Powder neutron diffraction and first-principles analysis provide evidence that the metallic LaMn_2–xAu_4+x phase can host the frustration-driven hedgehog spin-vortex crystal─a rare noncollinear magnetic state, which was previously exclusively observed for iron pnictides. 

Commercial (protiated) samples of the green and biodegradable bioester 2-ethylhexyl laurate (2-EHL) were mixed with D-2-EHL synthesized by hydrothermal deuteration, with the mixtures demonstrating bulk structuring in small-angle neutron scattering measurements. Analysis in a polymer scattering framework yielded a radius of gyration (R (g)) of 6.5 angstrom and a Kuhn length (alternatively described as the persistence length or average segment length) of 11.2 angstrom. Samples of 2-EHL dispersed in acetonitrile formed self-assembled structures exceeding the molecular dimensions of the 2-EHL, with a mean aggregation number (N-agg) of 3.5 +/- 0.2 molecules across the tested concentrations. We therefore present structural evidence that this ester can function as a nonionic (co)-surfactant. The available surfactant-like conformations appear to enable performance beyond the low calculated hydrophilic-lipophilic balance value of 2.9. Overall, our data offer an explanation for 2-EHL's interfacial adsorption properties via self-assembly, resulting in strong emolliency and lubricity for this sustainable ester-based bio-oil.